Solid state ionics: advanced concepts and devices
This symposium will focus on functional properties of ionic and mixed ionic-electronic conducting materials with especial emphasis on the interplay between ions and electrons and with a view toward their application in relevant smart and energy devices.
Mass and charge transport properties occurring at the bulk, interface or surface level in ionic or mixed ionic-electronic conducting materials are often controlling the properties of relevant solid state based devices such as solid oxide fuel and electrolysis cells, solid state batteries, permeation membranes, gas sensors or memristors. This symposium will focus on fundamental and applied aspects of Solid State Ionics covering theory, advanced characterization techniques, functional materials and interfaces as well as novel methodologies for the implementation of innovative concepts into enhanced devices. Moreover, the symposium will cover recent interest in ion-assisted phenomena that give rise to new families of fascinating devices such as all oxide photovoltaic cells or electrostriction-based transducers.
This symposium will provide a forum for extensive discussion and exchange of information among researchers exploring ion-conducting functional oxides in different contexts and diverse applications. This will include state-of-the art methods for structural and chemical characterization such as high resolution transmission electron microscopy, synchrotron-based spectroscopy and diffractometry, scanning probe microscopy and atom probe tomography, just to name a few, combined in many cases with modeling and simulation methodologies such as density functional theory and molecular dynamics. In addition, new methodologies for engineering ionic transport in functional materials will also be one of the main topics under discussion, with special emphasis in heterostructuring, doping and strain. Alternatively, advanced fabrication techniques able to define enhanced materials by design at the macroscale, such as 3D printing or ex-solution decoration, will be covered. Electrolysis, switching phenomena, photocatalysis, gas sensing, and solid state devices for energy and informatics (batteries, solid oxide fuel cells, memristors) will be some of the main applications and devices to be discussed.
Hot topics to be covered by the symposium:
Papers are solicited on (but not limited to) the following topics:
- Defect chemistry in functional oxides
- Nanoionics: mass and charge transport in the nanoscale
- Ion-assisted phenomena including iontronics, ferroelectrics, etc
- Methodologies for engineering ionic transport in functional materials
- Advanced structural characterization tools
- Advanced techniques for in situ/ in operando characterization of solid state ionics materials and devices
- Mass transport in bulk materials for solid state devices
- Solid State Ionics applied to energy devices: solid oxide cells, solid state batteries, permeation membranes, all oxide photovoltaics, oxide thermoelectrics, etc
- Solid State Ionics applied to smart devices: memristors, gas sensors, transducers, etc
- Thin film based solid state devices
List of invited speakers:
- John T. S. Irvine University of St Andrews, UK
- Rotraut Merkle, Max Planck Institute, Germany
- Mauro Pasta, University of Oxford, UK
- Jeff Sakamoto, University of Michigan, USA
- Vincenzo Esposito, DTU, DK
- Regina Dittmann, Forschungszentrum Jülich GmbH, Germany
- Mark Huijben, University of Twente, The Netherlands
- Andreas Klein, Technische Universität Darmstadt, Germany
- Mónica Burriel, CNRS-INP, France
- Sandrine Ricote, Colorado School of Mines, USA
- Felix Gunkel, Forschungszentrum Jülich GmbH, Germany
- David Mebane, West Virginia University, USA
- Sam Copper, Imperial College, UK
- George Harrington, Kyushu University, Japan
- Francesco Ciucci, The Hong Kong University of Science and Technology, Hong Kong
List of scientific committee members:
- Stephen Skinner, Imperial College London, UK
- Joachim Maier, Max Planck Institute for Solid State Research, Germany
- Igor Lubomirsky, Weizmann Institute, Israel
- Juergen Fleig, T.U. Wien, Austria
- Werner Sitte, Graz University of Technology, Austria
- Scott Barnett, Northwestern University, USA
- Susanne Hoffmann-Eifert, FZ-Juelich, Germany
- Harry L. Tuller, Massachusetts Institute of Technology, Cambridge, USA
- Zonping Shao, Nanjing University of Technology, China
- Jennifer Rupp, ETHZ, Switzerland and MIT, USA
- Tatsumi Ishihara, Kyushu University, Fukuoka, Japan
- Jose Santiso, ICN2, Barcelona, Spain
Selected papers will be published in a special issue of the journal Solid State Ionics (Elsevier Ltd.). Accepted papers will appear online immediately (with doi and page numbers) and subsequently be compiled in an online special issue. Attendance to the meeting is mandatory for the papers to be published.
3 poster prizes will be given:
- 1st prize: 250 euros,
- 2nd prize: 150 euros,
- 3rd prize 100 euros.
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|09:00||OPENING AND WELCOME|
Solid State Energy Devices (I): Solid Oxide Cells : TBC
Authors : John TS Irvine
Affiliations : University of St Andrews
Resume : Understanding and controlling the processes occurring at electrode/electrolyte interface are key factors in optimising fuel cells and electrolysers. Metal particles supported on oxide surfaces promote many of the reactions and processes that underpin the global chemical industry and are key to many emergent clean energy technologies. At present, particles are generally prepared by deposition or assembly methods which, although versatile, usually offer limited control over several key particle characteristics, including size, coverage, and especially metal-surface linkage. In a new approach, metal particles are grown directly from the oxide support though in situ redox exsolution. We demonstrate that by understanding and manipulating the surface chemistry of an oxide support with adequately designed bulk (non)stoichiometry, one can control the size, distribution and surface coverage of produced particles. We also reveal that exsolved particles are generally epitaxially socketed in the parent perovskite which appears to be the underlying origin of their remarkable stability, including unique resistance of Ni particles to agglomeration and to hydrocarbon coking, whilst retaining catalytic activity. Here we highlight recent work on electrochemical generation of nanoparticles in situ in solid oxide cells, the application of exolved particles on perovskite substrates in OER alkali fuel cells and the incorporation and exsolution of PGM nanoparticles from titanate perovskites.
Authors : Ji Wu,Jonathan Skelton,Stephen C. Parker
Affiliations : Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK;Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK;Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
Resume : The creation of socketed metal nano-particle through dopant exsolution from complex perovskite oxides has attracted significant interests over the past few years in the field of solid state ionics. Compared to deposited metal nano-particles, these exsoluted nano-particles retain good catalysis performances but are more resilient towards coking and delamination/agglomeration during cycling. Thus, these durable exsoluted nano-particles have many promising applications, like in chemical looping devices and anodes of solid oxide fuel/electrolyser cells (SOCs). Despite its great application potential, the mechanism behind the nano-particle exsolution process is not yet clear. Earlier theoretical efforts have shown that the migration of the transition metal dopants towards the perovskite surface are thermodynamically favourable. However, these findings cannot explain the highly reducing condition (5% H2/Ar mixed gas) and high temperature (above 950 degree Celsius) required to activate the exsolution process in experiments. In this work, atomistic simulation methods were applied to two typical perovskite systems, (La, Sr)1-x(Ni, Ti)O3-d and (La, Ca)1-x(Ni, Ti)O3-d, to study the kinetics of the metal cation migration during exsolution. We have shown that the metal cation hopping barrier between sites is too high in perovskites without A-site deficiency, but the introduction of A-site deficiency greatly reduces this barrier and makes cation migration viable under reported experimental conditions. Our findings reveal the critical role of A-site deficiency in the nano-particle exsolution process from oxide, and provide insights for future materials optimisation to utilize this exsolution process better.
Authors : Alfonso J. Carrillo, Laura Navarrete, Marwan Laqdiem, María Balaguer, Jose M. Serra
Affiliations : Instituto de Tecnología Química, UPV-CSIC. Av. de los Naranjos s/n, 46022 Valencia, Spain
Resume : Chemical looping reforming of methane coupled with CO2 splitting is a promising technology for syngas production. It consists of 2-steps that rely on the oxygen exchange capacity of metal oxides, such as CeO2. In the first step, CH4 is partially oxidized with CeO2 lattice oxygen, generating H2 and CO. Afterward, CO2 re-oxidizes the oxide, forming CO, closing the loop. Although CeO2 presents remarkable multicycle stability, its surface exchange kinetics are slow, hindering fast syngas production during the partial oxidation of methane. Surface functionalization with metal catalysts, prepared by impregnation, is normally employed to enhance reaction rates. However, the high process temperatures (~900 ºC) can cause nanoparticle sintering, decreasing the catalytic activity. To overcome this issue, the exsolution method has emerged as an alternative. In this process, metallic nanoparticles are created by the diffusion of cations contained in the oxide lattice that migrate to the surface, remaining anchored into the oxide support, minimizing particle agglomeration during prolonged operation. Here, we apply the exsolution method to create stable Ru nanoparticles of 2-5 nm. Catalytic tests show that exsolved Ru nanoparticles boost the fuel production rates, increasing the selectivity towards syngas. TEM analysis confirmed nanoparticle stability after 20 chemical loops, indicating the beneficial effects of exsolution oxide functionalization for high-temperature fuel production.
Authors : Tatsumi Ishihara, Zhe Tan, Atsushi Takagaki
Affiliations : Department of Applied Chemistry, Faculty of Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
Resume : NiO-Y2O3 stabilized ZrO2 (NiO-YSZ) supported tubular solid oxide cell, which consist of La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) dip-coated electrolyte film and Sm0.5Sr0.5CoO3-δ (SSC) air electrode, was prepared and power generation and electrolysis performance at intermediate temperature range were investigated. Among the rare earth oxides examined, infiltration of Ce nitrate into the substrate was the most effective for increasing cell performance in the case of 2 M infiltration. Moreover, it was found that the infiltration of higher concentration of Ce solution increased the maximum power density, because both IR loss and overpotential were significantly decreased. The maximum power density of the cell was 0.95 and 0.42 W cm-2 at 873 and 773 K, respectively at 3 M Ce nitrate infiltrated. The steam electrolysis performance of the cell using Ce infiltration was further studied and it was found that Ce also contributes to higher current density in SOEC operation and 1.07 A cm-2 at 1.6 V was achieved at 873 K using 2 M Ce infiltration. This superior SOFC/SOEC performance was achieved by formation of Ce3 in nano size CeO2 formed in Ni-YSZ substrate.
Authors : Navarrete, L.* (1), Sanchis-Sebastiá, M. (2) & Serra, J.M. (1). * firstname.lastname@example.org
Affiliations : (1) Instituto de Tecnología Química (Universitat Politècnica de València – Consejo Superior de Investigaciones Científicas), Av. Los Naranjos, s/n, 46022 Valencia, Spain. (2) Department of Chemical Engineering, Lund University, PO Box 124, SE-221 00 Lund, Sweden
Resume : Global warming and its consequences over environment have boosted the investigation of alternative energy sources for the reduction of CO2 emissions, and consequently, the dependence on fossil fuels. In addition, the scientific community efforts have focused on the CO2 transformation into added value chemicals and fuels. H2 is a flexible energy carrier and can be produced from water, with a low CO2 footprint. Among the technologies employed for H2 production, water electrolysis, is an efficient, green and commercial technology and if combined with CO2 electrolysis comes up as promising clean route for synthetic fuel production, such as CH4. Thus, in this work we have evaluated CH4 production via co-electolysis focusing on the selection of the most suitable catalyst for a high CH4 yield. Firstly, Ce0.9Gd0.1O2-δ-Ni (GDC-Ni) composite electrode was developed to ensure a proper electronic and ionic conductivity, and to guarantee a good porosity and electrode-electrolyte adhesion. In that direction, different Ce0.9Gd0.1O2-δ:Ni ratios and sintering temperatures were assessed. In a second step, a fixed-bed reactor was employed for the methane catalyst selection. The GDC-Ni powder was impregnated with different metal (Cr, Cu, Ni, Rh, Ru, Pd and Mo) precursors and tested in the co-electrolysis conditions to select the catalyst with the highest yield and selectivity to CH4. Finally, a fully-assembled co-electrolysis cell consisting of Sc doped Yttria as electrolyte and GDC-Ni and LSM-GDC as cathode and anode, respectively, was manufactured. Different current densities and temperatures were selected to study the methane production. The exhaust gas was monitored by a mass spectrometer and gas chromatograph.
Authors : M. A. Morales-Zapata, A. Larrea, M. A. Laguna-Bercero
Affiliations : Instituto de Nanociencia y Materiales de Aragón, c/ María de Luna 3, 50018 Zaragoza, Spain
Resume : Pr2NiO4-δ (PNO) and Ce0.9Gd0.1O2-δ (CGO) oxide mixtures have been tested in symmetrical cells by electrochemical impedance spectra (EIS) measurements at temperatures between 700°C and 850°C. As previously reported, PNO-CGO mixtures react at the typical SOFC sintering temperatures forming CPGO (praseodymium and gadolinium doped ceria). In despite of this in situ reaction, low polarization resistances can be achieved. The lowest polarization resistance was found for samples with 80 vol%. PNO-20 vol% CGO, showing polarization resistance values of about 0.16 Ωcm2 at 850°C. In addition, chemical diffusion (Dchem) and surface exchange (kex) coefficients of oxygen on mixed PNO and CGO oxides, were investigated using the electric conductivity relaxation technique (ECR) at different intervals of partial oxygen pressures (pO2) in temperature ranges between 600°C to 850°C. Changes in rate performance are observed as a result of heat treatment, which is manifested through variations in kex and their activation energies. Single cell electrochemical performance under SOFC and SOEC will be also shown. These findings confirm that PNO-CGO mixtures, forming mainly PCGO compositions, are presented as excellent candidates for SOC applications.
|11:00||OPEN DISCUSSION SESSION|
Solid State Energy Devices (II): Batteries : TBC
Authors : Francesco Ciucci (a,b)
Affiliations : (a) The Hong Kong University of Science and Technology, Mechanical and Aerospace Engineering, Clearwater Bay, Kowloon, Hong Kong, China SAR (b) The Hong Kong University of Science and Technology, Chemical and Biological Engineering, Clearwater Bay, Kowloon, Hong Kong, China SAR
Resume : Despite the widespread commercialization of conventional Li-ion batteries (LIBs), their safety I still a significant challenge. Conventional electrolytes are highly flammable and pose a significant safety hazard in case of an accident, overheating, and overcharging. Through experiments  and computations [2, 3], we developed and studied several alternative electrolytes, including ceramics, non-flammable composite polymers, and non-flammable liquids for high-energy-density Li- and Na-metal batteries. Improving the interfacial resistances and allowing a stable operation is key to these technologies. For these reasons, our works deployed several strategies including the development of conformal interlayers using plastic crystals and gels as well as fluorinated additives for the formation of stable solid electrolyte interlayers . We also designed a non-flammable trimethyl-phosphate-based electrolyte for sodium-sulfur batteries operating at room temperature . Acknowledgments The author gratefully acknowledges support from the Hong Kong Innovation and Technology Fund (No. ITS/292/18FP). References:  Z. Lu, J. Yu, J. Wu, M.B. Effat, S.C. Kwok, Y. Lyu, M.M. Yuen, F. Ciucci, Enabling room-temperature solid-state lithium-metal batteries with fluoroethylene carbonate-modified plastic crystal interlayers, Energy Storage Materials, 18 (2019) 311-319.  Z. Lu, F. Ciucci, Metal Borohydrides as Electrolytes for Solid-State Li, Na, Mg, and Ca Batteries: A First-Principles Study, Chemistry of Materials, 29 (2017) 9308-9319.  Z. Lu, J. Liu, F. Ciucci, Superionic Conduction in Low-Dimensional-Networked Anti-Perovskites (2019) - submitted  J. Yu, Y.-Q. Lyu, J. Liu, M.B. Effat, S.C. Kwok, J. Wu, F. Ciucci, Enabling non-flammable Li-metal batteries via electrolyte functionalization and interface engineering, Journal of Materials Chemistry A, 7 (2019) 17995-18002.  J. Wu, J. Liu, Z. Lu, K. Lin, Y.-Q. Lyu, B. Li, F. Ciucci, J.-K. Kim, Non-flammable electrolyte for dendrite-free sodium-sulfur battery, Energy Storage Materials, (2019)-In Press.
Authors : Markus Joos, Christian Schneider, Andreas Münchinger, Robert Usiskin, Bettina Lotsch, Joachim Maier
Affiliations : Markus Joos; Christian Schneider; Andreas Münchinger; Robert Usiskin; Bettina Lotsch; Joachim Maier; Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart Christian Schneider; Bettina Lotsch; Ludwig-Maximilians-Universität München (LMU), Butenandstr. 5-13 (Haus D), D-81377 München
Resume : Hydration can have profound effects on the defect chemistry and transport properties of ion conductors. Here we investigate hydration of the layered Li conductor Li2Sn2S5, which consists of covalently-bonded (Li,Sn)S2 layers and Li cations located between the layers. By varying the surrounding humidity, the water content of Li2Sn2S5 · x H2O can be readily and reversibly varied over the range x = 0 to 10. The water intercalates between the layers, increasing the interlayer distance from 6.2 Å for the anhydrous material up to 11.0 Å for Li2Sn2S5 ⋅ 10 H2O. A first-order phase transition is seen between x = 0 and about 2 by both thermogravimetry and X-ray diffraction, consistent with intercalation of the first monolayer of water. Impedance spectroscopy and pulsed-field gradient nuclear magnetic resonance reveal that the predominantly two-dimensional Li transport increases dramatically upon hydration. The fully hydrated compound remains solid, but reaches liquid-like values of 10-2 S/cm for the Li conductivity and 10-7 cm2/s for the Li self-diffusivity at 25 °C. These results provide an interesting example of a sulfide electrolyte system where humidity is highly beneficial to ion transport.
Authors : B. Gadermaier (1), K. Hogrefe (1), P. Frühwirt (2), G. Gescheidt (2), I. Hanzu (1), H. M. R. Wilkening (1)
Affiliations : (1) Institute of Chemistry and Technology of Materials, Graz University of Technology (NAWI Graz), Stremayrgasse 9, A-8010, Austria (2) Institute of Physical and Theoretical Chemistry, Graz University of Technology (NAWI Graz), Stremayrgasse 9, A-8010, Austria
Resume : Li4+xTi5O12 (LTO) is a well-known active material with promising properties for its use as an anode material in lithium-ion batteries. LTO can accommodate up to 3 excessive Li+ ions (and e− electrons) in its crystal structure with marginal volume changes and is, therefore, known as a so-called zero-strain material. During Li+ insertion, the Li-ions change their preference for the available crystallographic positions. This new situation of occupational disorder gives rise to a huge increase in both electronic and ionic conductivity. Rapid Li+ exchange between the sites 8a and 16c was found to be responsible for governing the main conduction mechanism in samples with x being larger than 0. Here, we focused on the conduction mechanisms present at the start of insertion, that is, in the non-lithiated Li4Ti5O12. Via impedance spectroscopy, we observed two distinctly differing conduction processes corresponding to a fast short-range and a slow long-range process. While the slow process must be characterized by an activation energy Ea of 0.83 eV, the faster one reflects Li+ translational dynamics determined by a considerably lower value of Ea = 0.54 eV. Interestingly, cycling the sample between RT and 200 °C in a slightly reducing nitrogen atmosphere increases the conductivity of the short-range process while long-range conductivity remains unaffected. To identify the responsible mechanism, we mimicked the soft annealing in a slightly reducing atmosphere by annealing the sample in a vacuum at 300 °C. This treatment led to even higher conductivity of the short-range process while that of the long-range process becomes slightly reduced. Making use of electron paramagnetic resonance (EPR) spectroscopy, we found that in vacuo annealing generates a strong resonance signal with a Landé factor of 2.003 pointing to free electrons that are most likely trapped in oxygen vacancies. Most importantly, EPR gave no evidence for Ti3+, which could give rise to polaronic conductivity. We, therefore, assume that the oxygen vacancies are responsible for the increased short-range ionic conductivity. Our results are furthermore supported by 6Li spin-lattice relaxation rates under magic-angle spinning conditions.
|12:30||OPEN DISCUSSION SESSION|
Interface & Surface Phenomena (I) : TBC
Authors : M. Rose, M. L. Weber, H. Yan, S. He, M. Andrae, F. Gunkel
Affiliations : Peter Gruenberg Institute 7 (PGI-7), Institute of Energy and Climate Research (IEK-1), RWTH Aachen University
Resume : Epitaxial oxide thin films allow combining the properties of complex oxides on the nanoscale in atomically defined manner. This enables us to play with electronic band structure and charge transfer at interfaces and surfaces of oxides, reflecting an additional degree freedom to control and manipulate their magnetic, electronic, and ionic properties. In complex oxides, the charge transfer associated with the electronic band alignment at interfaces can have both ionic and electronic contributions, making the understanding of charge-transfer phenomena complex. At the same time, the additional complexity arising from mixed ionic-electronic space charges can be very useful to tailor properties on the nanoscale. Here, we first discuss in a general manner the origin of space charges and defect structure at interfaces of complex oxides. We then discuss different examples of solid-solid oxide interfaces, [1,2] solid oxide-gas interfaces , and solid oxide-liquid interfaces. In the second part, special focus will be set on tailored oxide heterostructures employed for electrochemical water splitting in alkaline media, where we discuss strategies to tune catalytic activity and stability of tailored model catalysts, using an atomically defined epitaxy approach and space charge engineering.   Rose et al., Advanced Materials 2004132 (2020)  Gunkel, Christensen, Pryds, J. Mater. Chem C (2020)  Andrae et al., Phys. Rev. Mater., 3, 044604 (2019)  M. L. Weber, F. Gunkel, JPhys Energy 3, 031001 (2019)  M. L. Weber et al., Chem. of Mater., 31, 2337 (2019)
Authors : F. Baiutti (1), F. Chiabrera (1), M. Acosta (2), D. Diercks (3), D. Parfitt (4), J. Santiso (5), X. Wang (6), A. Cavallaro (7), A Morata (1), H. Wang (6), A. Chroneos (4), J. MacManus-Driscoll (2), A. Tarancon (1,8)
Affiliations : (1) Catalonia Institute for Energy Research (IREC), Jardins de Les Dones de Negre 1, 08930 Sant Adrià del Besòs, Barcelona, Spain (2) Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom (3) Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401, United States (4) Faculty of Engineering, Environment and Computing, Coventry University, Priory Street, Coventry CV1 5FB, United Kingdom (5) Catalan Institute of Nanoscience and Nanotechnology, ICN2, CSIC and The Barcelona Institute of Science and Technology (BIST), Campus UAB, 08193 Bellaterra, Barcelona. (6) School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States (7) Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP, United Kingdom (8) ICREA, 23 Passeig Lluís Companys, Barcelona 08010, Spain.
Resume : Nanoscale engineering is key for enhancing the electrochemical performance of high-temperature materials with potential application as functional layers in energy conversion devices. In the present contribution, we employed thin film self-assembly in order to fabricate vertically aligned nanostructures (VANs) of a predominantly electronic conductor (doped lanthanum manganite) and an ionic conductor (acceptor-doped ceria). The so-obtained composite exhibits nanoscale phase alternation of the phase components and long-range order. We assessed the structural and electrochemical properties of the VAN films by complementary structural and electrochemical methods and DFT simulations. We provide direct evidence of synergistic local effects which enhance both the oxygen reduction and the diffusion kinetics. Particularly, the novel use of atom probe tomography coupled with oxygen isotope tracing allowed for directly observing local pathways for fast oxygen migration with nm-resolution. The final electrochemical performance largely surpasses single phase LSM. Remarkably, the VAN under consideration also exhibits no apparent Sr segregation at operational temperatures, leading to stable area-specific resistance for over 100 hrs at 700 ºC as opposed to single-phase LSM. Low-energy ion scattering spectroscopy highlights a decrease of the Sr content upon thermal annealing. The finding is rationalized by DFT calculations in light of LSM lattice stabilization induced by cationic substitution during sample fabrication. The present work demonstrates the high potential of VAN films for solid oxide cells and highlights the role of cationic intermixing in the definition of the final functionalities of VAN heterostructures.
Authors : Clement Nicollet, Cigdem Toparli, George Harrington, Thomas Defferriere, Bilge Yildiz, Harry L. Tuller
Affiliations : Massachusetts Institute of Technology, 77 Massachusetts Av, 02139 Cambridge, MA, USA
Resume : In Solid Oxide Fuel Cells, oxygen electrode polarization related to electrochemical reactions at the gas/solid interface is often the dominant flux limiting mechanism. Accumulating surface impurities are well known to lead to a reduction in long term durability. On the contrary, surface modification with selected metal oxides can also have a positive effect on the oxygen surface exchange rate . As there is no clear understanding as to why some elements poison oxide surfaces while others enhance their oxygen exchange kinetics, defining a general descriptor is highly desirable, and is the goal of this work. The study uses Pr-doped ceria (PCO) as a model mixed ionic and electronic conductor with a high electrocatalytic activity toward the oxygen reduction reaction . PCO specimens were infiltrated with a variety of binary oxides and their surface exchange kinetics were evaluated by analysis of electrical conductivity relaxation measurements. By comparing the evolution of the surface exchange kinetics with different infiltrated oxides, it is possible to define the acidity of the infiltrated oxide as a descriptor that allows one, on the one hand, to predict what will be the effect of a given oxide on the surface exchange kinetics, and on the other hand to tune the surface exchange coefficient over 7 orders of magnitude with great precision. Through this new insight, it was possible to enhance the surface exchange coefficient by 500 times the initial values, illustrating the power of this new descriptor.  N. Tsvetkov, et al., Nat. Mater., 15 (9) (2016), 1010-1016  C. Nicollet, et al., Nat. Cat., 3 (2020), 913–920
Authors : Vincent Thoréton(1)*, Tor Svendsen Bjørheim(1), Xin Liu(1), Zuoan Li(2), Reidar Haugsrud(1)
Affiliations : (1) Centre for Materials Science and Nanotechnology (SMN), University of Oslo, Gaustadalléen 21, NO-0349, Norway. (2) SINTEF Industry, Sustainable Energy Technology, P.O. Box 124, Blindern,0314 Oslo, Norway.
Resume : Efficient Solid Oxide Cells (SOCs) require fast kinetics of the Oxygen Reduction Reaction (ORR) or Oxygen Evolution Reaction (OER) at the air electrode. The surface kinetics is affected by both intrinsic and extrinsic factors such as doping type and level, surface composition, applied potential and composition of the surrounding atmosphere. In particular, the interaction of oxygen-bearing molecules from the feed gas with the electrode surface is relevant to understand. One step is the interaction of water vapour with the air electrode since water is omnipresent in most situations and yields to diverse reactivities. In this work, we investigated the effect of humidity on the surface exchange kinetics of CaTi0.9Fe0.1O3-δ (CTF). The transport parameters were determined, and surface reaction mechanisms were investigated. We observed that water vapour exchanges more rapidly than molecular oxygen. Also, gradual lowering of the exchange kinetics of molecular oxygen is observed with exposure to water. This evolution could be explained by partial blockage of the surface by water and progressive degradation of the surface microstructure. The results were compared to those of other electrode materials and discussed in terms of bulk/surface defect chemistry. Acknowledgements The authors acknowledge financial support from the national funding organizations (Research Council of Norway, NWO, MINECO) in the framework of the M-ERA.NET project (grant number 258875) "Designing rules for enhancing SURface KINetics in functional OXides for clean energy technologies (SURKINOX). The authors would also like to acknowledge sup- port of the FRINATEK project 262393 ‘‘Fundamentals of Surface Kinetics in High Temperature Electrochemistry’’ (FUSKE) of the Research Council of Norway.
Authors : Christoph Riedl, Matthäus Siebenhofer, Andreas Nenning, Andreas Limbeck, Christoph Rameshan, Markus Kubicek, Alexander Opitz, Juergen Fleig
Affiliations : Vienna University of Technology, Institute of Chemical Technologies and Analytics, Am Getreidemarkt 6, 1060 Wien, Austria
Resume : In the search for high performance intermediate temperature solid oxide fuel cells (SOFCs), lowering the polarisation resistance of mixed ionic and electronic conducting electrodes is one of the main goals of current research activities. In this study, perovskite-type LaSr0.4FeO3-d (LSF64) electrodes were doped with minor amounts of platinum and two platinum doping levels were studied – 0.9 % and 1.5 % of the total cation amount - in the following denoted LSF-Pt1 and LSF-Pt2, respectively. The structure and composition of Pt doped LSF electrodes was characterized by atomic force microscope (AFM), inductively coupled plasma mass spectrometry (ICP-MS), ambient pressure X-ray photospectroscopy (AP-XPS) and high resolution scanning transmission electron microscopy (HR-STEM) measurements and, to conclude, platinum was found to be successfully incorporated into the perovskite lattice. The polarisation resistance of electrodes was measured in-situ directly after growth of the thin films in the pulsed laser deposition (PLD) chamber. Such a recording of electrochemical impedance spectra directly in the PLD chamber – which we usually refer to as in-situ PLD (i-PLD) – allows to characterize pristine electrodes with super clean surfaces unaltered by degradation. Despite the little Pt doping (1.5 %), LSF-Pt2 electrodes showed about a factor of 2.5 faster oxygen reduction kinetics at 0.04 mbar O2 compared to pure LSF. Furthermore, pure LSF and Pt-doped LSF electrodes revealed equal p(O2) dependence of the polarisation resistance and similar activation energies. Surprisingly, the rate determining step appears to be unchanged by the Pt addition and the improved oxygen reduction kinetics can thus solely be explained be an increase of reaction sites on the electrode surface. In addition, in-situ monitored multilayer growth of different electrode materials on the very same substrate allows excellent comparability of obtained resistance values and again highlights the important role of the electrode surface. Moreover, these experiments reveal the enormous increase in electrode performance realisable by targeted addition of tiny amounts of Pt, thus showing a possible way for the highly efficient use of precious metal catalysts in SOFCs.
Authors : Christoph Baeumer
Affiliations : MESA+ Institute for Nanotechnology, University of Twente, Faculty of Science and Technology, P.O. Box 217, 7500 AE Enschede, Netherland; Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, 52425 Juelich, Germany
Resume : Energy storage through the electrocatalytic generation of chemical fuels such as hydrogen is an attractive pathway for storing intermittent renewable energies, and perovskite oxides are among the most attractive candidate materials to catalyze the kinetically limiting half reaction, the oxygen evolution reaction (OER). To overcome the limited stability and decrease high overpotentials, a detailed understanding of the underlying relationships between catalytic activity, stability and atomic-level surface structure is required, but challenging to obtain due to the complex surface transformations occurring under reaction conditions. Single crystalline surfaces offer the ideal platform to derive such relationships, for example in the form of epitaxial thin films, which can be fabricated with unit-cell precision and enable direct comparison to surfaces investigated in density functional theory. Here, we will demonstrate surface-composition-activity relationships in epitaxial LaNiO3 thin films, which are atomically flat both before and after application as electrocatalysts for the OER during water electrolysis. We selectively tuned the surface cationic composition through the choice of growth temperature and through sequential deposition, resulting in Ni- and La- terminated model surfaces. The Ni-termination is approximately twice as active for the OER as the La-termination. Using a suite of ex situ, in situ and operando spectroscopy tools, we found that the Ni-rich surface undergoes a surface transformation towards a catalytically active Ni hydroxide-type surface that preserves the surface cation stoichiometry of the as prepared state, while La-termination only leads to high overpotentials and eventual failure.1 Our work thus demonstrates tunability of surface transformation pathways by modifying a single atomic layer at the surface and it shows that active surface phases only develop for select as-synthesized surface terminations, highlighting the instructional value of epitaxial model electrocatalysts. It also confirms that we need to further explore the three-step relationship between as-prepared surface, transformation under applied potential, and electrocatalytic activity. References 1. Baeumer, C. et al. Tuning electrochemically driven surface transformation in atomically flat LaNiO3 thin films for enhanced water electrolysis. Nat. Mater. accepted, (2021).
|15:45||OPEN DISCUSSION SESSION|
Poster Session (I) : TBC
Authors : Antonino Curcio (1), Jian Wang (2), Zheng Wang (1), Zhiqi Zhang (1), Alessio Belotti (1), Simona Pepe (1), Mohammed B. Effat (1), Zongping Shao (3,4), Jongwoo Lim (2), Francesco Ciucci (1,5,6)
Affiliations : (1) Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China (2) Department of Chemistry, College of Science, Seoul National University, Seoul, 08826, South Korea (3) State Key Laboratory of Materials‐Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing, China (4) Department of Chemical Engineering, Curtin University, Perth, Western Australia, Australia (5) Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, China (6) Guangzhou HKUST Fok Ying Tung Research Institute, China
Resume : Hydrogen is projected to play a central role in the energy storage and conversion sector. For hydrogen production, electrochemical water splitting will likely be one of the most important technologies. However, significant challenges remain, especially because the kinetics of the water splitting reactions is sluggish. Transition metal dichalcogenides (TMDs) and perovskites have shown promise for the evolution of hydrogen and oxygen, respectively. However, several perovskites, including SrCoO¬3−δ, are characterized by proton-transfer-limited oxygen evolution reaction. In principle, perovskites and TMDs can be combined to obtain higher catalytic activity, exploiting the favorable energetics for the hydrogen adsorption of the latter. However, the interaction between these two materials has not been studied yet. Here, we studied composite materials obtained by mechanochemically coupling a family of perovskites SrMO¬3-δ (M=Co, Fe, Ti) and MoS2, a model TMD. We observed that the proton‐transfer kinetic limitation of SrCoO¬3−δ can be overcome by mating it with MoS2 mechanochemically. Through the combination of different experimental techniques and DFT computations, we reveal that the MoS2 at the MoS2@SrCoO3−δ heterointerfaces acts as an electron and a proton acceptor, thereby facilitating deprotonation of the perovskite, leading to faster OER kinetics. In contrast, if the transfer of protons is not rate-limiting, like in the case of SrFeO¬3−δ and SrTiO¬3−δ, mating MoS2 and the perovskite, does not lead to significant activity improvement. This work paves the way to the hybridization of MoS2 and oxides as a strategy for breaking the linear scaling relationship of the OER, enhancing the activity of materials limited by proton‐transfer energetics.
Authors : S. Siol (a), N. Ott (a), C. Beall (a,b), S. D. Tilley (a,b), Y. Unutulmazsoy (a), P. Schmutz (a), L. P. H. Jeurgens (a), C. Cancellieri (a)
Affiliations : (a) Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland (b) University of Zurich, Department of Chemistry, Winterthurerstrasse 190, 8057 Zurich, Switzerland
Resume : TiO2 and WO3 are two of the most important, industrially relevant earth-abundant oxides. Both materials show complementary functionality, and are promising candidates for similar types of applications such as catalysis, sensor technology and energy conversion. At the same time their chemical stability in reactive environments differs remarkably, often limiting the durability of WO3 as compared to TiO2. In this work, tungsten titanium oxides are grown on solid solution WxTi1-x alloy precursors with the goal of creating functional oxides with tailored surface passivation. Different oxidation routes (thermal oxidation versus barrier anodizing) are employed on precursors covering the entire compositional range (0≤x≤1) and with different oxidation conditions.[1,2] To investigate the synthesis-property-relationships in this complex phase space we use a combination of combinatorial and serial experiments including combinatorial sputter deposition as well as XRD, XRF, and XPS mapping. Using this approach over 200 unique oxide samples were analyzed with respect to their crystal structure as well as their bulk and surface composition. The resulting mixed WxTi1-xOn oxides exhibit a composition-dependent structural evolution from monoclinic over cubic to tetragonal. In addition, a strong Ti-cation enrichment in the surface region of the grown WxTi1-xOn layer is observed, which can be controlled by both the oxidation kinetics and the alloy precursor composition. For Ti-concentrations above 55 at.%, a continuous nm-thick TiO2 protective coating is achieved on top of a homogeneous WxTi1-xOn film as evidenced by detailed photoemission and transmission electron microscopy analyses . A comprehensive electrochemical assessment is performed on the oxides, demonstrating a very stable passivation of the surface in both acidic and alkaline environments. This increase in chemical stability correlates directly with the presence of the protective TiO2 film . The results of this work provide insights into the passivation and phase formation of WxTi1-xOn alloys, but more importantly demonstrate how controlled oxidation of self-passivating alloys can lead to oxide alloys with thin, protective surface layers that otherwise would require more sophisticated deposition methods.  Siol et al. ACS Appl. Mater. Interfaces, 2019, 11 (9), 9510–9518  Siol et al. Acta Materialia 2020, 186, 95–104
Authors : Sarah Eisbacher-Lubensky, Andreas Egger, Edith Bucher, Werner Sitte
Affiliations : Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria
Resume : A substantial challenge of materials research for solid oxide cells is the development of air electrodes with fast oxygen exchange kinetics, high electronic and ionic conductivities, and improved long-term stability. The present work is focused on cobalt-doped lanthanum nickelate La2Ni0.9Co0.1O4+δ with respect to its crystal structure, oxygen nonstoichiometry, defect chemistry, thermal expansion behaviour as well as mass and charge transport properties. The powder was synthesized via the citrate/EDTA method and X-ray powder diffraction confirmed that the material is single-phase and crystallizes in the K2NiF4-type structure. The electronic conductivity and oxygen exchange kinetics were studied using in-situ dc-conductivity and relaxation measurements. The chemical diffusion coefficient of oxygen Dchem and the chemical oxygen surface exchange coefficient kchem as well as the electronic conductivity were determined as a function of temperature and oxygen partial pressure. The oxygen nonstoichiometry was obtained by thermogravimetry. Self-diffusion coefficients of oxygen and ionic conductivities were estimated from the experimentally determined values of Dchem and the thermodynamic factor of oxygen. Within this contribution, the influence of cobalt doping with respect to the specified properties is discussed by comparing La2Ni0.9Co0.1O4+δ with La2NiO4+δ. The results indicate that La2Ni0.9Co0.1O4+δ offers an attractive option for application as air electrode in solid oxide cells.
Authors : Monica Susana Campos Covarrubias1, Mantas Sriubas1, Kristina Bockute1, Piotr Winiarz2, Maria Gazda2, Giedrius Laukaitis1
Affiliations : (1) Kaunas University of Technology, Physics Department, Studentu str. 50, LT-51368, Kaunas, Lithuania (2)Gdansk University of Technology, Faculty of Applied Physics and Mathematics, Narutowicza 11/12, 80-233 Gdansk, Poland e-mail: email@example.com
Resume : Proton conductive thin film ceramics are largely studied due to their applications to various portable1 electrochemical devices as fuel cells, sensors, batteries, hydrogen separators2-3, hydrogenation/dehydrogenation reactions as ammonia formation, and ethylene production. BaZrO3 is a perovskite oxide represented by a general formula of ABO3. The B side can be doped with lower oxidation state metals4 (e.g. Al+3, Sc+3, In+3, Lu+3, Tm+3, Y+3, Gd+3, and Sm+3) to create oxygen vacancies promoting proton conduction. This material is stable above 600oC and less reactive to CO2. However, it requires high sintering temperatures to reach high density and enhance the proton conduction. One of the drawbacks of high temperatures is the evaporation of Ba that influences its ion conductivity5. This drawback can be eliminated by employing different deposition techniques, for example, e-beam vapor deposition can form a high dense thin film at intermediate substrate temperatures6. E-beam vapor deposition allows the evaporation of high melting point materials due to the high beam power and improves the density of the films at low substrate temperatures. The current research discusses the microstructure, lattice strain, and chemical stability of Yttrium-doped Barium zirconate (BZY) thin films formed by e-beam deposition. Thin films were deposited on different alloy substrates (Invar, glass sealing alloy, Stainless steel, and Inconel) distinguished by their thermal expansion coefficient varying in great range at 600oC using different deposition rates. That influenced the microstructure and the crystallinity of the formed BZY thin films. Low deposition rate (1Å/s) and substrate temperature 600oC allows to obtain highly oriented and highly dense thin films. Also, the different yttrium concentration influenced the crystal phase and crystallization. Thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS). The research was financially supported by project no. 2017/27/L/ST5/03185 founded by the National Science Centre, Poland and Research Council of Lithuania (LMTLT), agreement No S-LL-18-3. (1) Serra, J. M.; Meulenberg, W. A. Journal of the American Ceramic Society 2007, 90 (7), 2082–2089. https://doi.org/10.1111/j.1551-2916.2007.01677.x. (2) Mazzei, L.et. all. J. Mater. Chem. A 2018. https://doi.org/10.1039/C8TA06202A. (3) Sažinas, R.et. all. J. Mater. Chem. A 2019. https://doi.org/10.1039/C8TA11021B. (4) Gilardi, E.; et. all. The Journal of Physical Chemistry C 2017, 121 (18), 9739–9747. https://doi.org/10.1021/acs.jpcc.7b02163. (5) Yamazaki, Y.; et. all. J. Mater. Chem. 2010, 20 (37), 8158–8166. https://doi.org/10.1039/C0JM02013C. (6) Campos Covarrubias, et. all. Crystals 2020, 10 (12), 1152. https://doi.org/10.3390/cryst10121152.
Authors : Maxim Varenik, Ellen Wachtel, Elad Gaver, and Igor Lubomirsky
Affiliations : Dept. Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel
Resume : The majority of commonly used electrostrictive ceramics are based on lead manganese niobate. These ceramics display large electrostriction strain coefficients ~ 10^-16 m^2/V^2 at frequencies up to a few kHz; however they suffer from two major drawbacks: large dielectric constants (>10000), which require high driving currents, and incompatibility with thin-film Si-microfabrication techniques. We have recently reported that aliovalent doped ceria exhibits electrostriction coefficients >100-fold larger than estimated on the basis of Newnham’s scaling law for classical electrostrictors, despite ceria’s large Young’s modulus (~ 200 GPa) and low dielectric constant (< 30). This “non-classical” behavior has been attributed to the formation of highly polarizable, elastic dipoles reorienting under external electric field. For 10mol% Sm- or Gd-doped ceria, the measured longitudinal electrostriction strain coefficient, |M|, reaches 10^-16 m^2/V^2; however, relaxation to <10^-18 m^2/V^2 is observed at frequencies > 1 Hz , well below the technologically important frequency range 100Hz-100 kHz. The introduction of aliovalent lanthanide dopants with smaller radii than that of Gd, such as Lu or Yb, succeeds in increasing |M| at 100Hz to 10^-17 m^2/V^2. Nevertheless, aliovalent dopants with radii smaller than that of Lu do not continue the trend. We have found that partially reduced, 10 mol% Zr4+-doped ceria displays |M| ~10^-16 m^2/V^2 throughout the 0.1-150 Hz frequency range. However, practical application of these ceramics may be hindered by the relatively large, room-temperature electrical conductivity (10^-10 S/m), a result of the formation of Ce3+ which can promote electron hopping. Formation of Ce3+ also raises the dielectric constant to ~ 200, as measured by impedance spectroscopy. Suppression of Ce3+ by co-doping with 0.5mol% Yb produces a dramatically reduced electrostriction strain coefficient (at f = 0.1-150Hz), ~ 4·10^-18 m^2/V^2. If the Yb concentration is raised to 10 mol% , |M| increases to ~2·10^-17 m^2/V^2 but is sharply lowered to 4·10^-16 m^2/V^2 at 15 mol% Yb. Co-doping with a large radius, aliovalent lanthanide, e.g. 0.5-10mol% La, returns the measured high frequency |M | to ~ 4·10^-18 m^2/V^2. Taken together, these results suggest that elastic dipoles induced in ceria ceramics by small aliovalent dopants, give stronger electrostrictive response at high frequencies (>10 Hz) than the larger aliovalent dopants. For the case of isovalent doping with Zr of reduced ceria, the presence of Ce3+ seems to be essential for large |M|. Noting that Ce3+ is almost as large as La3+, we may conclude that the elastic dipoles operating in Zr-doped, reduced ceria are fundamentally different from those observed for aliovalent doping. Our results imply that by systematically adjusting the composition of ceria-based solid solutions, the potential exists for development of technologically useful electrostrictive materials which are, at the same time, fully compatible with Si-microfabrication.
Authors : Lukas Porz, Till Frömling, Atsutomo Nakamura, Ning Li, Ryohei Maruyama, Katsuyuki Matsunaga, Peng Gao, Hugh Simons, Christian Dietz, Marcus Rohnke, Jürgen Janek, and Jürgen Rödel
Affiliations : Technical University of Darmstadt
Resume : Dislocations are known to influence functional properties of oxides  and have recently been suggested as viable means to tune functional ceramics. Besides the difficulty to introduce dislocations into ceramics, their exact influence on functional properties is still unclear. As not all influence factors are known it is difficult to compare one study to another. We introduce dislocations into SrTiO3 single crystals by plastic deformation at different temperatures in a highly ordered manner. Using both impedance spectroscopy and TOF-SIMS it is demonstrated that the introduced dislocations – in contrast to expectations raised from other studies – do no alter the conductivity noticeably. Dark field x-ray diffraction and TEM investigation are used for detailed characterization of the dislocation substructure supplemented by atomic resolution TEM revealing a completely different structure as compared to other studies. We conclude that functional properties depend on a multitude of features. Hence, we suggest to discuss dislocations in functional ceramics in the context of three sets of features: 1) The arrangement (loops, kinks, jogs, screw, edge, etc.), 2) the core structure, and 3) the space charge zone.
Authors : Christina Nader (1), Christian Berger (2), Edith Bucher (1), Werner Sitte (1)
Affiliations : (1) Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben, Austria; (2) Max-Planck-Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
Resume : Protonic ceramic fuel cells (PCFCs) offer the possibility of highly efficient, sustainable and cost-effective generation of electrical energy. However, a challenge, which has yet to be overcome, is the development of highly-active cathode materials, which provide mixed proton-, oxygen ion- and electron conductivity, and fast oxygen- as well as proton exchange kinetics. Recently, a sol-gel synthesis route was described, which allows for the preparation of self-generated nanocomposites from the BaCeO3-δ - BaFeO3-δ system . In our group, this approach was adapted by the partial substitution of Ce and Fe by Y, in order to develop ceramic nanocomposites Ba(Ce,Fe,Y)O3-δ - Ba(Fe,Ce,Y)O3-δ with increased proton uptake capacity. In the present study, the chemical diffusion coefficients of oxygen Dchem of selected self-generated nanocomposites from the Ba(Ce,Fe,Y)O3-δ - Ba(Fe,Ce,Y)O3-δ system were investigated by the dc-conductivity relaxation method. The electrical conductivity of the composites was determined by four-point dc-conductivity measurements. The experiments were conducted on dense sintered samples as a function of temperature in the range of 400-800°C and 0.10 ≤ pO2/bar ≤ 0.15 in dry and humidified atmospheres (0 ≤ pH2O/bar ≤ 0.024). In dry atmosphere, the electrical conductivities of self-generated composites from the Ba(Ce,Fe,Y)O3-δ - Ba(Fe,Ce,Y)O3-δ system with the overall stoichiometries BaCe0.8-xFexY0.2O3-δ (x=0.6, 0.4, 0.2) are in the range of 1E-3 ≤ S/cm ≤ 1E-1 (dry atmosphere) and increase with increasing Fe-content. This is expected due to the increase in the concentration of p-type charge carriers [Fe4+]=[h●] leading to an increase in the contribution of the electronic conductivity to the electrical conductivity. In humidified atmosphere, the electrical conductivity is lower than in dry atmosphere, which may be due to the annihilation of p-type charge carriers upon proton incorporation. Chemical diffusion coefficients of oxygen of the composites with the overall stoichiometries BaCe0.8-xFexY0.2O3-δ (x=0.6, 0.4, 0.2) are in the range of 6E-8 ≤ Dchem / cm²/s ≤ 2E-5 at 400-800°C (dry atmosphere) and increase with increasing temperature and Fe-concentration. In humidified atmosphere, Dchem is slightly higher than in dry atmosphere.  S.Cheng et al., Angew. Chem. Int. Ed. 2016, 55, 10895.
Authors : Yu.A. Mastrikov 1, D.S. Pavlov 2, M.V. Ananyev 2,3, M.N. Sokolov 1
Affiliations : 1 Institute of Solid State Physics, University of Latvia, 8 Kengaraga, LV1063, Riga, Latvia 2 Institute of High Temperature Electrochemistry, the Ural Branch of the Russian Academy of Sciences, 20 Akademicheskaya st., Ekaterinburg, Russia, 620990 3 B. N. Yeltsin Ural Federal University, 19 Mira st., Ekaterinburg, Russia, 620002
Resume : LaScO3-based oxides (LSO) are promising oxide materials for solid oxide electrochemical devices: Protonic Ceramic Fuel Cells (PCFC), - Electrolysis Cells (PCEC) and gas sensors. Comparing with BaZrO3- and BaCeO3-based systems, lanthanum scandate-based oxides possess higher stability in reductive and carbon-containing atmospheres, which promotes their potential application for dry hydrocarbon reforming in PCFCs and PCECs devices, and sensors in respective atmospheres. Application relevant properties of LSO strongly depend on its structure. Various defects were observed experimentally in polycrystalline samples. Among them - AntiPhase Boundaries (APB). APB may serve as channels for enhanced ionic/proton conductivity in perovskites. DFT modelling was performed for APB of several types. Structural as well as energetic stability of calculated APB were determined.
Authors : Victor Duffort*(a), Martin Pajot(a), Soukaina Mountadir(a), Edouard Capoen(a), Anne-Sophie Mamede(a), Rose‑Noëlle Vannier(a)
Affiliations : (a) Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
Resume : Typical high temperature solid oxide fuel cells (HT-SOFC) use a La0.8Sr0.2MnO3 (LSM)/Zr1.92Y0.08O3.96 (YSZ) composite cathode on a YSZ electrolyte and a nickel/YSZ cermet anode. Due to the limited oxide conductivity of yttria stabilized zirconia, high temperatures (> 700 °C) are required in order to achieve sufficient ionic conduction. However, elevated temperatures come with significant engineering challenges motivating the long standing effort to decrease the operation temperature of SOFC. Substituting YSZ by erbium stabilized bismuth oxide (ESB) in the cathodic compartment and gadolinium doped ceria (GDC) at the anode, two much better ionic conductors, allow for a significant improvement leading to a specific power density of ~1 W cm-2 at 650 °C. Based on these results several groups optimized the microstructure or preparation of the cathode without changing the composition of the LSM. However, this stoichiometry was optimized for high temperature compatibility with YSZ and needed to be optimized as well for lower temperature. Here, we focused on the influence of the strontium content in La1-xSrxMnO3 on the area specific resistance (ASR) of composite LSM/ESB electrodes. Several compositions (x = 0.15, 0.3, 0.4, 0.5, 0.6, 0.8) were tested to investigate the influence of the structure, the electronic transport mechanism or the Mn3+/4+ ratio. Using X-ray diffraction, thermogravimetric analysis and Low Energy Ion Scattering spectroscopy (LEIS) we showed that, differently from the high temperature range, where surface segregation of SrO is the main deactivation process, at lower temperature it is the surface oxidation that inhibits the oxygen reduction efficiency of LSM. The catalytic activity of the cathodes was evaluated by Electrochemical Impedance Spectroscopy (EIS) on symmetric cells using an ESB electrolyte. We found a 2-fold decrease of the ASR at 500 °C when switching from La0.85Sr0.15MnO3, i.e. the high temperature optimized stoichiometry, to La0.6Sr0.4MnO3. Acknowledgements The Fonds Européen de Développement Régional (FEDER), CNRS, Région Hauts de France, Ministère de l'Enseignement Supérieur et de la Recherche and Agence Nationale de la Recherche and BIBELOT ANR-18-CE05-0001 are acknowledged for funding. References E.D. Wachsman, K.T. Lee, Science, 334 (2011), 935-939 J.W. Park, B.H. Yun, D.W. Joh, K.T. Lee, Electrochemical Society, 68(1) (2015), 957-96 M. Pajot, V. Duffort, E. Capoen, A.-S. Mamede, R.N. Vannier, J. Power Sources 450 (2020), 227649.
Authors : Xavier Randrema, Mohamed Chakir, Virginie Viallet, et Mathieu Morcrette
Affiliations : Renault, 1 avenue du Golf, 78084 Guyancourt, France Laboratoire de Réactivité et Chimie des Solides (LRCS), 33 rue Saint Leu, 80039 Amiens, France
Resume : The rapid growth of electric mobility is characterized by a strong interest of academic and industrial research laboratories on the so-called “All-Solid-State-Batteries”. Indeed, conventional commercialized batteries are based on liquid electrolyte composed by flammable compounds. The first target of solid-state technology is thus to solve concerns regarding safety issue for the more and more numerous users of electric vehicle. In addition, promising energy density (Wh.kg-1 and Wh.l-1) superior to conventional lithium-ion batteries are supposed thanks to the use of lithium metal as anode material (3860 mAh.g-1). Solid electrolytes and particularly sulfide-based solid electrolyte have attracted attention because they present a high ionic conductivity allowing fast charge application if lithium dendrites (1) can be solved and low temperature operation. Among these, the Li6PS5Cl Argyrodite (space group F4 ̅3m) discovered in 2008 (2) is the subject of many recent studies due to its simplicity to obtain by mecano-synthesis (3) as well as a high ionic conductivity up to 3 mS.cm-1 at room temperature (4). This material seems promising for its use in composite electrodes, but also in separator for all-solid-state-batteries made by dry or by wet process (5). Nevertheless, intrinsic chemical instabilities (6) and decomposition reactions by contact with active material lead to electrochemical performances below expectations. Moreover, an industrial lock to solid-state technology development is the difficulty to produce those batteries on current Li-ion production lines based on slurry coating processes (7). In this work, we were first interested in the deep characterization of solid electrolyte, to assess structure and ionic conductivity of the material. We found the presence of an amorphous phase and we highlighted the importance of annealing treatment to increase argyrodite crystallite size along with ionic conductivity values. In a second time, electrochemical stability of the phase was tested by galvanostatic cycle in order to verify the electrochemical window. Then, a new route synthesis was proposed through an intermediate step precursor in order to obtain Li6PS5Cl without impurities remaining. Finally, a wet process approach will be discussed in order to match with industrial prospects. This require a dissolution - precipitation protocol. Nevertheless, the dissolution of Li6PS5Cl in organic solvent have shown a decrease of ionic conductivity after solvent evaporation. From the deep characterizations previously tackled, preliminary results will be presented to elucidate this detrimental effect for All-Solid-State-Batteries domain especially if fast-charge applications are targeted. References (1) J. Kasemchainan, S. Zekoll, D. Spencer Jolly, Z. Ning, G. O. Hartley, J. Marrow, and P. G. Bruce, Nature Materials, 18 (2019) 1105. (2) H-J. Deiseroth, S-T Kong, H. Eckert, J. Vannahme, C. Reiner, T. Zaiß, and M. Schlosser, Angewandte Chimie, 120 (2008) 767. (3) S. Boulineau, M. Courty, J-M. Tarascon, and V. Viallet, Solid State Ionics, 221 (2012) 1. (4) S. Wang, Y. Zhang, X. Zhang, T. Liu, Y-H. Lin, Y. Shen, L. Li, and C-W. Nan, ACS Applied Materials Interfaces, 10 (2018) 42279. (5) Y-J. Nam, D-Y. Oh, S-H. Jung, and Y-S. Jung, Journal of Power Sources, 375 (2018) 93. (6) T. Schwietert, V. Arszelewska, C. Yu, C. Wang, A. Vasileiadis, N. de Klerk, J. Hageman, T. Hupfer, I. Kerkamm, Y. Xu, E. van der Maas, E. M. Kelder, S. Ganapathy, and M. Wagemaker, Nature Materials, (2020). (7) J. Schnella, T. Günthera, T. Knochea, C. Vieidera, L. Köhlera, A. Justa, M. Kellerb, S. Passerinib, G. Reinhart, Journal of Power Sources, 382 (2018) 160.
Authors : Anna Ivanova, Andrew Chesnokov, Dmitry Bocharov, Kai S. Exner
Affiliations : Anna Ivanova, University of Latvia Institute of Solid State Physics; Andrew Chesnokov, University of Latvia Institute of Solid State Physics; Dmitry Bocharov, Latvijas Universitate, Institut of Solid State Physics; Kai S. Exner, University of Duisburg-Essen, Theoretical Chemistry;
Resume : In present study the competing oxygen evolution and hydrogen peroxide (H2O2) formation reactions for periodic models of graphene with different active-site concentrations by means of density functional theory (DFT) calculations. Linking the DFT calculations to ab-initio thermodynamic considerations enables gaining unprecedented insight into the activity and selectivity trends of graphene-based electrodes as a function of applied bias. We illustrate that both the coverage of intermediates on the electrode surface as well as the applied electrode potential have a significant effect on the Faradaic efficiency for the electrocatalytic production of H2O2. This allows deriving design criteria for peroxide formation, which may serve as a guideline for further studies to realize selective formation of H2O2 by carbon-based materials.
Authors : G. Zvejnieks, D. Zavickis, E. A. Kotomin, D. Gryaznov
Affiliations : Institute of Solid State Physics, University of Latvia, Riga, Latvia
Resume : Cobalt oxide based materials demonstrate a wide range of physical phenomena. Recently these materials became actively studied for applications in catalysis  and as an effective cathode materials in solid oxide fuel cells . Materials used in practical applications have a complex multicomponent structure  that often is built on the basis of BaCoO3 (BCO) type perovskites. Therefore, understanding of this simplest perovskite structure is of paramount importance. Contrary to earlier assumed hexagonal (space group P6_3/mmc) ground state of BCO , using first principles calculations and group-theoretical analysis, we predict here BCO monoclinic distortion. Our first principles calculations included Gaussian-type basis set and hybrid (B1WC) functional as implemented in the CRYSTAL17 code . We demonstrate that the BCO ground state properties are also consistent with recent experimental findings . The C-AFM low spin (LS) magnetic structure (obtained with SG P2/c) is energetically only slightly more preferential than the FM LS magnetic structure (SG C2/c). However, these monoclinic geometry is energetically more preferential than the hexagonal one due to a slight z-axis tilting. A connection between the electronic properties and distortion preference is discussed in detail.  X. Xu, et al., Adv. Sci., 2016, 3, 1500187.  T. Ogawa, M. Takeuchi and Y. Kajikawa, Sustainability, 2018, 10, 458.  R. Zohourian, et al., Adv. Funct. Mater., 2018, 28, 1801241.  H. Nozaki, et al., Phys. Rev. B, 2007, 76, 014402.  R. Dovesi, et al., CRYSTAL17 User’s Manual, University of Torino, Torino, 2017.  Y. Y. Chin et al., Phys. Rev. B, 2019, 100, 205139.
Authors : Alexander Schmid, Maximilian Morgenbesser, Alexander Viernstein, Federico Baiutti, Juan de Dios Sirvent, Niklas Bodenmüller, Stefanie Taibl, Markus Kubicek, Albert Tarancon, Jürgen Fleig
Affiliations : TU Wien, Institut für chemische Technologien und Analytik; TU Wien, Institut für chemische Technologien und Analytik; TU Wien, Institut für chemische Technologien und Analytik; Catalonia Institute for energy reasearch, IREC; Catalonia Institute for energy reasearch, IREC; TU Wien, Institut für chemische Technologien und Analytik; TU Wien, Institut für chemische Technologien und Analytik; TU Wien, Institut für chemische Technologien und Analytik; Catalonia Institute for energy reasearch, IREC, Catalan Institution for Research and Advanced Studies, ICREA; TU Wien, Institut für chemische Technologien und Analytik
Resume : High temperature solid oxide solar cells based on SrTiO3 (STO) are investigated. Those are based on hetero-junctions between STO single crystals and different materials, including La1-xSrxCrO3 (LSCr), La0.8Sr0.2MnO3, La0.6Sr0.4CoO3 and metals like Au and Pt, UV illuminated at 350 °C in air. The resulting open circuit photo-voltages are remarkably high, i.e. more than 1 V for STO/Au and STO/LSCr. An additional contribution to the photovoltage with a long characteristic timescale was observed and attributed to photo-ionic effects, i.e. oxygen transport due to photo-induced chemical potential gradients. Short circuit current measurements showed a continuous increase of the photo-current over several hours, likely related to stoichiometry changes in the bulk STO due to self polarization. Under operation, this results in a self enhancement effect of the photovoltaic cell with time. Electrochemical impedance spectroscopy was used to reveal mechanistic information on the processes under UV illumination, especially regarding the space charge region at the hetero-junction. Furthermore, the transferability of these single crystal studies to thin film oxide solar cells was investigated. First results highlight the importance of thin film (non)stoichiometry for the photo-voltage.
Authors : Joe Kler, Roger A. De Souza
Affiliations : Institute of Physical Chemistry RWTH Aachen University; Institute of Physical Chemistry RWTH Aachen University
Resume : Oxygen surface exchange refers to the dynamic equilibrium between oxygen in the gas phase and oxygen in a solid oxide. It is a complex process, comprising many possible reaction steps (e.g., adsorption, charge transfer, dissociation, incorporation) that involve various possible intermediate species. To date, a large variety of materials have been investigated, but two aspects of the exchange process have not been given sufficient attention: the influence of a surface space-charge layer and the influence of the surface orientation on the surface exchange. The perovskite oxide SrTiO3 was chosen for this study as its bulk properties are already well understood, and it can be used as a model system for more complex perovskites. Oxygen isotope exchange experiments, combined with determination of the isotope profile by means of Secondary Ion Mass Spectrometry (SIMS), were carried out on nominally un-doped SrTiO3 single crystals with different surface orientations [(100), (110), and (111)]. In all cases, the isotope profiles can be described quantitatively with a numerical solution to the diffusion equation with a position-dependent diffusion coefficient, yielding the tracer diffusion coefficient in the bulk D_b^*, the surface exchange coefficient k_s^* and the space charge potential Φ0. Results as a function of temperature for the three different surface orientations will be presented. In addition, a thermodynamic model was used to extract possible thermodynamic driving forces for space charge formation. Furthermore, a model focused on the kinetics of the exchange reaction of the solid surface was used to describe the influence of the space charge layer on the surface exchange coefficient.
Authors : Harald Summerer, Melanie Maurer, Andreas Nenning, Lorenz Lindenthal, Raffael Rameshan, Christoph Rameshan, Alexander K. Opitz
Affiliations : TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165, 1060 Vienna, Austria; TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165, 1060 Vienna, Austria; TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria
Resume : Exsolution catalysts gained popularity as novel type of oxide-supported catalysts, where a transition metal, originally part of the perovskite lattice, can be exsolved as metallic nano-particles on the oxide surface during a reductive treatment. By employing such a perovskite as an electrode in a solid oxide cell (SOC), one can change the effective oxygen partial pressure within the oxide electrode by application of an overpotential. Consequently, exsolution of metallic particles can be triggered by applying a sufficiently cathodic overpotential. By subsequently changing the polarisation, the electrode can be switched between an active and a less active state (called “electrochemical switching”). In a recent study, we showed that this electrochemical switching process is reversibly possible, even if the exsolved particles do not re-dissolve into the perovskite lattice. Moreover, the increase in catalytic activity by presence of surface-decorating metallic catalyst particles arises from enabling an additional reaction path and thus bypassing the rate determining step on the bare perovskite surface . In the present study, we aim to gain further detailed insights into the electrochemical switching behaviour of perovskite-type electrodes by electrochemical and ambient pressure XPS (APXPS) measurements. The studied materials are La 0.6Sr0.4FeO3-δ (LSF) and Nd0.6Ca0.4Fe1-zXzO3-δ (NCFX, where X can be either Co or Ni, and z is either 0 or 0.03 or 0.1), from which thin film electrodes were grown by pulsed laser deposition (PLD) on single-crystalline yttria-stabilised zirconia electrolytes. The obtained model-type thin film electrodes are characterised at elevated temperatures over a wide range of oxygen partial pressures by means of electrochemical impedance spectroscopy (EIS) and steady-state I-V-curve measurements. With this, we can determine the minimum required overpotential and gas phase composition for the formation of exsolutions. We also observe reversible electrochemical switching between metal and metal oxide surface phases by a switch from a steep to a shallow I-V slope and a hysteresis loop in the transition region. The electrochemical switching point coincides with the metal to metal oxide transition found in the APXPS measurements. By combining electrochemical and spectroscopic results, we aim at drawing mechanistic conclusions of the switching effect and its interesting features such as the hysteresis while switching between active and inactive states. Moreover, we deal with the question of fractionated exsolution in multi-B-site-component perovskites, which is especially interesting for the application in heterogeneous catalysis.
Exsolution catalysts gained popularity as novel type of oxide-supported catalysts, where a transition metal, originally part of the perovskite lattice, can be exsolved as metallic nano-particles on the oxide surface during a reductive treatment. By employing such a perovskite as an electrode in a solid oxide cell (SOC), one can change the effective oxygen partial pressure within the oxide electrode by application of an overpotential. Consequently, exsolution of metallic particles can be triggered by applying a sufficiently cathodic overpotential. By subsequently changing the polarisation, the electrode can be switched between an active and a less active state (called “electrochemical switching”). In a recent study, we showed that this electrochemical switching process is reversibly possible, even if the exsolved particles do not re-dissolve into the perovskite lattice. Moreover, the increase in catalytic activity by presence of surface-decorating metallic catalyst particles arises from enabling an additional reaction path and thus bypassing the rate determining step on the bare perovskite surface .
In the present study, we aim to gain further detailed insights into the electrochemical switching behaviour of perovskite-type electrodes by electrochemical and ambient pressure XPS (APXPS) measurements. The studied materials are La 0.6Sr0.4FeO3-δ (LSF) and Nd0.6Ca0.4Fe1-zXzO3-δ (NCFX, where X can be either Co or Ni, and z is either 0 or 0.03 or 0.1), from which thin film electrodes were grown by pulsed laser deposition (PLD) on single-crystalline yttria-stabilised zirconia electrolytes. The obtained model-type thin film electrodes are characterised at elevated temperatures over a wide range of oxygen partial pressures by means of electrochemical impedance spectroscopy (EIS) and steady-state I-V-curve measurements. With this, we can determine the minimum required overpotential and gas phase composition for the formation of exsolutions. We also observe reversible electrochemical switching between metal and metal oxide surface phases by a switch from a steep to a shallow I-V slope and a hysteresis loop in the transition region. The electrochemical switching point coincides with the metal to metal oxide transition found in the APXPS measurements. By combining electrochemical and spectroscopic results, we aim at drawing mechanistic conclusions of the switching effect and its interesting features such as the hysteresis while switching between active and inactive states. Moreover, we deal with the question of fractionated exsolution in multi-B-site-component perovskites, which is especially interesting for the application in heterogeneous catalysis. A. K. Opitz et al. Understanding electrochemical switchability of perovskite-type exsolution catalysts. Nat. Communications. 2020, 11, 1-10.
Authors : Christoph Riedl, Matthäus Siebenhofer, Andreas Limbeck, Markus Kubicek, Alexander Opitz, Juergen Fleig
Affiliations : Vienna University of Technology, Institute of Chemical Technologies and Analytics, Am Getreidemarkt 6, 1060 Wien, Austria; Vienna University of Technology, Institute of Chemical Technologies and Analytics, Am Getreidemarkt 6, 1060 Wien, Austria; Vienna University of Technology, Institute of Chemical Technologies and Analytics, Am Getreidemarkt 6, 1060 Wien, Austria; Vienna University of Technology, Institute of Chemical Technologies and Analytics, Am Getreidemarkt 6, 1060 Wien, Austria; Vienna University of Technology, Institute of Chemical Technologies and Analytics, Am Getreidemarkt 6, 1060 Wien, Austria; Vienna University of Technology, Institute of Chemical Technologies and Analytics, Am Getreidemarkt 6, 1060 Wien, Austria;
Resume : Understanding the oxygen reduction pathway on the surface of mixed ionic and electronic conducting (MIEC) materials and revealing the rate-determining step is of great importance for further knowledge-driven development of intermediate temperature solid oxide fuel cells (SOFCs). In this study, the impedance of different lanthanum based electrodes (LaSr0.4CoO3-d (LSC), La0.6Sr0.4FeO3-d (LSF), Pt-doped La0.6Sr0.4FeO3-d (LSF) and La0.6Sr0.4MnO3-d (LSM)) was measured in-situ , directly after thin film electrode growth in the pulsed laser deposition (PLD) chamber. This in-situ PLD (i-PLD) approach enables impedance measurements of pristine electrodes unaltered by degradation and without any external contaminations of the surface that might occur during sample transfer from the PLD to an ex-situ measurement setup. Electrodes were stepwise deposited on different single crystalline electrolyte substrates and the polarisation resistance was monitored during growth, which yielded thickness dependent information on polarisation resistance and defect chemistry. Growth on different substrates allowed us to investigate the influence of different crystallographic orientations on the electrode properties. In addition, studying the influence of the p(O2) on the polarisation resistance and its activation energy yielded further insights to improve our understanding of oxygen reduction on MIEC electrodes.
Authors : Laura M. de Kort, Petra E. de Jongh, Peter Ngene
Affiliations : Debye Institute for Nanomaterials Science, Utrecht University
Resume : The development of energy storage technologies, such as rechargeable batteries, is crucial for the transition to a sustainable energy supply. Lithium-ion batteries have already proven to be an effective means of energy storage, which is illustrated by their wide application ranging from mobile phones to laptops and electric vehicles. Unfortunately, Li-ion batteries suffer from safety issues arising from their combustible organic electrolytes. All-solid-state batteries, in which the common liquid organic electrolyte is replaced by a solid electrolyte, could potentially lead to safer batteries with increased energy density. Metal hydrides (e.g. LiBH4) have gained attention as promising solid electrolytes due to their electrochemical and thermal stability, low density and high ionic conductivity at elevated temperatures. However, sufficient conductivity at ambient temperatures remains a challenge. Fortunately, it was shown that the room temperature conductivity can be enhanced via two methods: partial ionic substitution and nanoconfinement. In this contribution, we will show a conductivity enhancement approach in which both methods were successfully combined to achieve high ionic conductivities at moderate temperatures. Specifically, via partial ion substitution, followed by confinement in a nanoporous metal oxide, LiBH4-LiNH2/oxide nanocomposites with excellent ionic conductivity were obtained. The ionic conductivity of nanocomposites electrolytes is strongly influenced by the chemical and physical nature of the nanoporous metal oxide, leading to conductivity variation up to three orders of magnitude. We will discuss how the conductivity of the both LiBH4- and LiBH4-LiNH2 nanocomposite electrolytes can be optimized by tuning the physical and chemical properties of the metal oxide nanoscaffolds. References  Goodenough, John B., and Kyu-Sung Park. "The Li-ion rechargeable battery: a perspective." Journal of the American Chemical Society 135.4 (2013): 1167-1176.  Mohtadi, Rana, and Shin-ichi Orimo. "The renaissance of hydrides as energy materials." Nature Reviews Materials 2.3 (2017): 16091.  Maekawa, Hideki, et al. "Halide-stabilized LiBH4, a room-temperature lithium fast-ion conductor." Journal of the American Chemical Society 131.3 (2009): 894-895.  Blanchard, Didier, et al. "Nanoconfined LiBH4 as a fast lithium ion conductor." Advanced Functional Materials 25.2 (2015): 184-192.
Authors : Roman Zettl (1,2), Maria Gombotz(1), David Clarkson (3), Steven G. Greenbaum (3), Peter Ngene (2), Petra E. de Jongh (2), H. Martin R. Wilkening (1,4)
Affiliations : (1) Institute of Chemistry and Technology of Materials, Graz University of Technology (NAWI Graz), Stremayrgasse 9, 8010 Graz, Austria; (2) Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht 3584, Netherlands; (3 ) Department of Physics and Astronomy, Hunter College of the City University of New York, New York 10065 New York, United States; (4) Alistore−ERI European Research Institute, CNRS FR3104, Hub de l’Energie, Rue Baudelocque, F-80039 Amiens, France
Resume : Solid electrolytes based on LiBH4 receive much attention because of their high ionic conductivity, electrochemical robustness, and low interfacial resistance against Li metal. The highly conductive hexagonal modification of LiBH4 can be stabilized via the incorporation of LiI. If the resulting LiBH4-LiI is confined to the nanopores of an oxide, such as Al2O3, interface-engineered LiBH4-LiI/Al2O3 is obtained that revealed promising properties as a solid electrolyte. The underlying principles of Li+ conduction in such a nanocomposite are, however, far from being understood completely. Here, we used broadband conductivity spectroscopy and 1H, 6Li, 7Li, 11B, and 27Al nuclear magnetic resonance (NMR) to study structural and dynamic features of nanoconfined LiBH4-LiI/Al2O3. In particular, diffusion-induced 1H, 7Li, and 11B NMR spin−lattice relaxation measurements and 7Li pulsed field gradient (PFG) NMR experiments were used to extract activation energies and diffusion coefficients. 27Al magic angle spinning NMR revealed surface interactions of LiBH4-LiI with pentacoordinated Al sites, and two-component 1H NMR line shapes clearly revealed heterogeneous dynamic processes. These results show that interfacial regions have a determining influence on overall ionic transport (0.1 mS cm−1 at 293 K). Importantly, electrical relaxation in the LiBH4-LiI regions turned out to be fully homogenous. This view is supported by 7Li NMR results, which can be interpreted with an overall (averaged) spin ensemble subjected to uniform dipolar magnetic and quadrupolar electric interactions. Finally, broadband conductivity spectroscopy gives strong evidence for 2D ionic transport in the LiBH4-LiI bulk regions, which we observed over a dynamic range of 8 orders of magnitude. Macroscopic diffusion coefficients from PFG NMR agree with those estimated from measurements of ionic conductivity and nuclear spin relaxation. The resulting 3D ionic transport in nanoconfined LiBH4-LiI/Al2O3 is characterized by an activation energy of 0.43 eV.  A. Manthiram, X. W. Yu, S. F. Wang, Nat Rev Mater 2017, 2.  H. Maekawa, M. Matsuo, H. Takamura, M. Ando, Y. Noda, T. Karahashi, S. I. Orimo, J Am Chem Soc 2009, 131, 894-+.  R. Zettl, L. de Kort, M. Gombotz, H. M. R. Wilkening, P. E. de Jongh, P. Ngene, J Phys Chem C 2020, 124, 2806-2816.
Authors : G. Mineo (1,2), S. Mirabella (1,2), E. Bruno(1,2)
Affiliations : (1) Dipartimento di Fisica e Astronomia “Ettore Majorana”, Università di Catania, via S. Sofia 64, 95123 Catania, Italy. (2) CNR-IMM, Università di Catania, via S. Sofia 64, 95123 Catania, Italy.
Resume : Given the wide capability of small positive ions (H+ and Li+) intercalation WO3 represents a promising material for energy storage applications. In this scenario, nanostructured WO3 is extremely interesting given the high surface-to-volume ratio allowing a high rate of charge transfer in supercapacitors. Here, we report a simple and low-cost hydrothermal technique for WO3 nanorods synthesis on Fluorine doped Tin Oxide (FTO) coated glass. SEM analysis reveals a full intertwining of ~250nm long nanorods, with hexagonal crystal structure confirmed by XRD investigation. Growth optimization against time, pH and temperature synthesis allowed to get a stable covering of FTO substrate. A large electrochemical study (employing by cyclic voltammetry, electrochemical impedance spectrometry and galvanostatic charge discharge analysis) allowed to measure quantitative performances of WO3 nanorods in terms of specific capacitance (Cs), specific energy (SE) and specific power (SP). These data are presented and discussed.
Authors : Jia Guo, Stephen J Skinner
Affiliations : Department of Materials Imperial College London
Resume : As one of the most promising candidates for electrodes of solid oxide fuel cells (SOFCs), double perovskite has been drawing attention in the past few years due to its high structural variability and chemical-physical tunability . A properly tuned double perovskite usually possesses both high electronic conductivity and ionic conductivity (MIEC). Usually, higher electronic conductivity can be contributed by multi-valent B-site cations in double perovskites, while oxygen vacancies are essential to enable oxygen ion transport through the electrode layer for higher ionic conductivity. A-site non-stoichiometry can be introduced to promote the oxygen deficiency of perovskite materials, hence enhancing the electrochemical performance of double-perovskite based SOFCs . Ruthenium is widely applied as an electrocatalyst in fuel cells because the high density of d-states of ruthenium atoms can directly exchange electrons with the absorbed gas molecules or species . Ruthenium-based double perovskites have, however, only rarely been investigated as an electrode in SOFCs. In this work, the stoichiometric and A-site-deficient lanthanum nickel ruthenate double perovskites, La2-xNiRuO6-δ (0 < x < 0.25, LxNR), were successfully synthesized by the nitrate-citrate sol-gel method. The crystal structure and degree of B-site ordering were characterized by X-ray diffraction (XRD) and the compositions were confirmed with EDX and ICP spectroscopies. The oxidation states and electron configurations were characterized by X-ray photoelectron spectroscopy (XPS). Interestingly, the XPS spectra demonstrated a unique chemical environment of Ru cations, implying a distinctive electronic conducting mechanism and electronic properties. Thereafter, four-probe DC conductivity measurement and electrochemical impedance spectroscopy (EIS) were adopted to study the electrical conductivity of LxNR. The results revealed the evolution of electrical conductivity with increasing concentration of A-site deficiency in the LxNR double perovskites. Besides, the stability of LxNR under reducing atmosphere and the possibility of exsolving B-site metal nanoparticles from the LxNR substrate are discussed. In general, a novel series of A-site deficient double perovskite ruthenates was synthesized and investigated with multiple techniques, showing promising perspectives as applied to SOFC electrodes. References:  X. Chen et al., Inorg. Chem. Front., 2019, 6, 2226  J. C. Pérez-Flores et al., Chem. Mater. 2013, 25, 12, 2484  J. Lee and B. Popov, J Solid State Electrochem. 2007, 11, 1355
Authors : *Xin DAI(1), Yuya Komatsu(1), Ryota Shimizu(1)(2), Taro Hitosugi(1)
Affiliations : (1) Tokyo Tech, Japan; (2) JST-PRESTO，Japan
Resume : Divalent europium (Eu2+) compounds such as EuF2 and EuO have attracted wide attention due to their unique optical and magnetic properties originating from the f7-electron configurations. (1) For optoelectronics and spintronics applications, it is required to fabricate them in an epitaxial thin film form. However, previous reports on epitaxial growth are limited; besides, there are only a few reports on the growth of EuO (2), (3) and no report on the growth of EuF2. The difficulty in the epitaxial growth is the precise control of anion supply to thin films. Recently, we reported that the use of F-conducting substrates is useful for the fluorination of metal films, and demonstrated the fabrication of YF3(010) epitaxial thin films on a MgF2(100) substrate (4). Here, we expand this concept to Eu2+ compounds, and report the epitaxial growth of EuF2(111) on a CaF2(111) substrate and the epitaxial growth of EuO(100) on a yttria-stabilized ZrO2 (YSZ) (100) substrate. We fabricated EuF2 (thickness: 80 nm) and EuO (thickness: 40 nm) thin films using magnetron sputtering. CaF2(111) and YSZ(100) substrates are chosen for F-conducting and O-conducting substrates, respectively. We used the Eu metal (diameter: 1 inch) as a target, and only introduce Ar gas into the deposition chamber. The structural characterization was operated using X-ray diffraction and cross-sectional transmission electron microscopy. The XRD patterns of thin films deposited at a substrate temperature of 700°C on CaF2(111) and YSZ(100) substrates showed diffraction peaks of EuF2 111 and EuO 200. Furthermore, pole figure measurements and cross-sectional transmission electron microscopy revealed that both the EuF2 and EuO thin films are epitaxially grown. These results indicate that the use of anion-conducting substrates offers us an effective way to fabricate metal-fluoride and metal-oxide epitaxial thin films. Reference: 1) He et al., Nanoscale, 3, 184 (2011), 2) Iwata et al., J. Phys. Soc. Jpn. 69, 230 (2000), 3) Yamasaki et al., Appl. Phys. Lett. 98, 082116 (2011). 4) Dai et al., Appl. Phys. Express, 13, 085507 (2020).
Authors : Anshuman Chaupatnaik¹*, Eldho Edison², Rodney Chua², Madhavi Srinivasan², Prabeer Barpanda¹.
Affiliations : ¹Faraday Materials Laboratory, Materials Research Centre, Indian Institute of Science, Bangalore – 560012, India ²School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore - 639798
Resume : SONY’s LiCoO₂/Graphite lithium-ion battery (LIB, circa 1991) made LIBs the top power source for mobile electronics. Although early research in 1967 on Na-β-Al₂O₃ based on American Ford Motor’s Na-S or African ZEBRA’s Na-NiCl₂ cells preceded LIBs, both grew parallelly until graphite (which cannot host Na) put LIBs in the limelight. Due to the low availability hence the high cost of lithium sources, sodium-ion batteries (NIBs) have come back with a promise for large-scale grid storage. On the other hand, leading battery industries, pack more material in confined space to accumulate higher energy densities for advertising longer hours or more miles. However, this comes at a safety cost which calls for new material exploration, more urgently for NIB anodes. This is because both the stellar LIB anodes (high-energy graphite and high-power Li₄Ti₅O₁₂) are inactive in NIBs. Also, low voltage Na₂Ti₃O₇ is likely impractical due to the instability of its sodiated phase which leaves hard carbon as the only NIB anode. Inspired by Na₂Ti₃O₇, we found PbTi₃O₇ to store both sodium and lithium (300-400 mAh/g) ions. NIBs and novel hybrid sodium-ion capacitors (NIC) employing monoclinic freudenbergite NaFeTi₃O₈ (200 mAh/g) and high-temperature tetragonal hollandite Na₁.₇Cr₁.₇Ti₆.₃O₁₆ (90 mAh/g) minerals will be presented. Finally, LIBs employing tetragonal narsarsukite Na₂TiOSi₄O₁₀¹, monoclinic freudenbergite NaMTi₃O₈ (M = Al, Fe, Cr), Cr-hollandite minerals and LICs using orthorhombic MLi₂Ti₆O₁₄ (M = 2Na, Ba², Sr³, Pb⁴) (MLTO) materials will be discussed. The role of atomic structure, ionic conductivity, and migration pathways on final electrochemical performance will be described for this titanate anodes⁵. The underlying electrochemical redox mechanism will be explained for some such titanium-based anodes. References ¹ A. Chaupatnaik, M. Srinivasan, P. Barpanda, Narsarsukite Na₂TiOSi₄O₁₀ as a low voltage silicate anode for rechargeable Li-ion and Na-ion batteries, Appl. Energy Mater., (2019), 2, 2350-2355. ² A. Chaupatnaik, P. Barpanda, Diffusional and electrochemical investigation of combustion synthesized BaLi₂Ti₆O₁₄ titanate anode for rechargeable batteries, J. Mater. Res., 2018, 34, 158-168. ³ A. Dayamani, G. Shinde, A. Chaupatnaik, R. P. Rao, S. Adams, P. Barpanda, Electrochemical and diffusional insights of combustion synthesized SrLi₂Ti₆O₁₄ negative insertion material for Li-ion Batteries, J. Power Sources, 2018, 385, 122-129. ⁴ A. Chaupatnaik, P. Barpanda, Swift combustion synthesis of PbLi₂Ti₆O₁₄ anode for lithium-ion batteries: diffusional and electrochemical investigation J. Electrochem. Soc., 2019, 166, A5122-A5130. ⁵ A. Chaupatnaik, A. Rambabu, P. Barpanda, Investigation of Titanate Family of Anode Materials for Li-Ion Batteries: Three Case Studies. ECS Meeting Abstract, 2018, MA2018-02, 286.
Authors : Anshuman Chaupatnaik¹*, Prabeer Barpanda¹
Affiliations : ¹Faraday Materials Laboratory, Materials Research Centre, Indian Institute of Science, Bangalore – 560012, India.
Resume : This work repurposes lead-based simple ABX₃ perovskite structure (not its complex derivatives) as an anode in high energy density rechargeable batteries. Barely 4 years after 1991’s SONY’s introduction of Li-Ion battery, Fuji Photo Film Co. in a 1995 patent ¹ announced an Sn-based amorphous tin composite oxide (ATCO ²) glass that delivered four times volumetric and two times the gravimetric anode energy density than graphite ³. Enlightened by this, there was an instant swing in research activity over the next decade in all kinds of starting materials having the Sn alloying center ⁴ including some having perovskite-type ABX₃ structure ⁵. In this aspect, experimental proof using PbTiO₃, PbZrO₃ will be presented here for the first time ⁶ as a glimpse into many similar potential ABX₃ candidate battery materials. Following the structural breakdown of PbTiO₃ during the first irreversible conversion cycle, Pb alloying and TiO₂ insertion gave reversible capacities up to 400 mAh/g for Li/Na (nearly 4e-/mol) and 180 mAh/g for K (nearly 2e-/mol) for the first charge.
Authors : Alexander Schmid, Jürgen Fleig
Affiliations : TU Wien, Institut für chemische Technologien und Analytik; TU Wien, Institut für chemische Technologien und Analytik
Resume : The chemical capacitance of mixed ionic electronic conducting (MIEC) solid oxide fuel cell (SOFC) electrodes is a capacitive property, reflecting changes in their (oxygen) stoichiometry in response to (oxygen) chemical potential variations. Fundamentally, this is the same electrochemical process that occurs when charging and discharging of lithium ion battery cathodes, except that lithium takes the place of oxygen there. This equivalence of SOFC electrodes and ion battery electrodes is discussed, with a focus on the relation between chemical capacitance, electrode capacity and defect chemistry. We demonstrate this by the example of La0.6Sr0.4FeO3-δ (LSF) thin film (200 nm) electrodes grown by pulsed laser deposition (PLD) on yttria stabilized zirconia (YSZ) single crystal substrates. Dense zirconia cover layers were deposited on top of these films to block the oxygen surface exchange, thus creating oxygen ion battery electrodes. Bias dependent impedance spectroscopic (EIS) chemical capacitance measurements and galvanostatic current voltage discharge curve measurements were performed on those oxygen ion battery electrode films. Those showed the correspondence between the battery capacity measured via discharge curves and the chemical capacitance measured via EIS, and thus that SOFC and ion battery electrodes behave in the same way, electrochemically.
Authors : Matthäus Siebenhofer, Alexander Viernstein, Tobias Huber, Stefan Smetaczek, Christopher Herzig, Andreas Limbeck, Jürgen Fleig, Markus Kubicek
Affiliations : Institute of Chemical Technologies and Analytics, Technische Universität Wien, Getreidemarkt 9/164EC, 1060 Vienna, Austria
Resume : Strontium titanate is a perovskite oxide and its properties which are exploited in different devices range from dielectric to memristive to mixed ionic electronic conductive. Well established defect models exist for acceptor and donor-doped SrTiO3, however, establishing a model for nominally undoped SrTiO3 single crystals is challenging due to the need to investigate all defects and impurities down to ppm level. Here we present a new method capable of sub-ppm defect analysis, namely investigations of the chemical capacitance by electrochemical impedance spectroscopy. By parameter variation of p(O2) and temperature (RT-700°C), we established a complex defect model for undoped SrTiO3 based on the low frequency impedance response of single crystals contacted by sputtered platinum. In addition to the charge-active defect concentrations, our model also allows to determine electronic trapping energies, e.g. of electronic holes trapped at Ti vacancies. Further, our technique of detailed measurements of the chemical capacitance upon parameter variation is not restricted to strontium titanate, but may be used for many mixed ionic electronic conducting materials. In combination with trace elemental analysis (by ICP-MS) and positron annihilation lifetime spectroscopy (PALS) we could also determine exactly which charge-active defects species were responsible for the measured impedance responses (e.g. the most important cation defects were 6 ppm Ti vacancies). In addition, also the concentrations of relatively uncharged impurity species such as Ca, Ba on the Sr site were determined.
Authors : Giorgio Colombi, Diana Chaykina, Tom de Krom, Steffen Cornelius, Stephan Eijt, Bernard Dam
Affiliations : Materials for Energy Conversion and Storage, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, NL-2629HZ Delft, The Netherlands ; Materials for Energy Conversion and Storage, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, NL-2629HZ Delft, The Netherlands & Fundamental Aspects of Materials and Energy, Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft,The Netherlands ; Fundamental Aspects of Materials and Energy, Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft,The Netherlands ; Materials for Energy Conversion and Storage, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, NL-2629HZ Delft, The Netherlands ; Materials for Energy Conversion and Storage, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, NL-2629HZ Delft, The Netherlands & Fundamental Aspects of Materials and Energy, Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft,The Netherlands ; Materials for Energy Conversion and Storage, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, NL-2629HZ Delft, The Netherlands
Resume : Rare-earth oxyhydride thin films prepared by air-oxidation of reactively sputtered REH2 dihydrides show a color-neutral, reversible photochromic effect at ambient conditions. Here we show how the O:H anion ratio, as well as the choice of the cation, allow to largely tune the extent of the optical change and its speed. The bleaching time in particular can be reduced by an order of magnitude by increasing the O:H ratio. The influence of the cation (RE=Sc, Y, Gd) under comparable deposition conditions is discussed. Our data suggest that REs of larger ionic radius form oxyhydrides with larger optical contrast and faster bleaching speed, hinting to a dependency of the photochromic mechanism on the anion diffusion. We frame these novel results in a broader discussion of (i) the hypothesized mechanisms behind the photochromic effect, and (ii) the analogies & differences between RE-oxyhydride thin films and bulk powders.
Authors : Benjamin Rudolph, Galina Kokorin, Simone Mascotto
Affiliations : Institute of Inorganic and Applied Chemistry University of Hamburg Martin-Luther-King Platz, 6 D-20146 Hamburg tel.: +49(0)40 42838-4304
Resume : Perovskite-type oxides (ABO3) systems has been widely used to prepare metal supported nanoparticles as novel high performing catalysts. Perovskites display a high degree of structural stability and the ability to incorporate catalytically active species into the lattice via doping. Upon exposure at reducing atmosphere (Ar/H2) at high temperatures (≈ 900 °C), oxygen is released and transition metal dopants are exsolved via surface segregation. The exsolution process is highly dependent on the oxygen release kinetics of the system. Nanoporosity represents a beneficial method to improve exsolution kinetics via shorter diffusion path length of ionic charge carriers in the nanostructured perovskite crystallites. Even though the exsolution phenomenon is extensively studied, to the best of our knowledge, the concept of nanostructuring of the parent structure received poor attention. In the present work, nanoporous La0.52Sr0.28Ti0.94Ni0.06O3 (LSTN) with a surface area of approx. 25 m²/g demonstrated to exsolved Ni nanoparticles at temperature as low as 500 °C instead of 900 °C typical for sintered systems. H2 TPR reduction profiles witnessed early stages of exsolution while XRD evidenced the presence of crystalline metallic Ni. Electron microscopy revealed nanoparticle of 20 to 50 nm, for both nanoporous and sintered LSTN. Information on the amount of exsolved Ni0 was obtained by X ray absorption spectroscopy. Element specific X ray absorption near edge structure (XANES) was measured at the Ni X-ray absorption K edge at 8333 eV. Linear combination fitting was applied to quantify the contribution of each Ni species after reduction. We could point out that nanostructured LSTN exsolved the same amount of Nickel at temperatures 200 °C lower than its sintered counterpart. In this way, we demonstrated that nanoporous of the host material effectively reduces time and temperature of exsolution. In this way, it will be possible tailor the particle size and distribution in much more precise fashion for optimization of the materials surface chemistry and porosity for applications in catalysis and energy conversion.
Authors : Marcel Sadowski, Karsten Albe
Affiliations : Institute of Materials Science, Technical University of Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt; Institute of Materials Science, Technical University of Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt
Resume : Sulfide solid electrolytes (SE) comprise promising materials for the usage in Li all-solid-state batteries due to high Li ion conductivities and easy processing. Especially the argyrodite materials within Li6PS5X (X = Cl, Br, I) stand out with ionic conductivities in the range of 1 mS/cm competing with those of conventional liquid electrolytes. For the Li6PS5Br it was found that a S/Br site-disorder in the range of 10-40% can be induced depending on the synthesis protocol. Furthermore, it was found that the ionic conductivity increases with increasing site-disorder. In order to understand the underlying dependence between structure and ionic transport we performed density functional theory (DFT) and ab-initio molecular dynamics (AIMD) simulations on a variety of Li6PS5Br structures with different degrees of site-disorder. In line with the experiment, we will present results from AIMD simulations proving the necessity of S/Br site-disorder to enable sufficient Li transport at low temperatures . A detailed analysis of the influence of the local structure on the Li transport is carried out and relations between the S/Br site-disorder and other properties such as the thermodynamical stability or lattice constants are presented. The results can be used to develop improved materials and synthesis protocols.  A. Gautam, M. Sadowski et al., Chem. Mater. 31 (24) 10178-10185 (2019), https://doi.org/10.1021/acs.chemmater.9b03852
Authors : Adrian L. Usler, Roger A. De Souza
Affiliations : Institute of Physical Chemistry, RWTH Aachen University; Institute of Physical Chemistry, RWTH Aachen University
Resume : It is generally accepted that, in polycrystalline oxygen-ion conductors, a considerable excess resistivity stems from the influence of the grain boundaries. In samples of high purity, this excess resistivity is commonly attributed to the presence of space-charge layers in which oxygen vacancies are depleted. In this study, the electrical properties of space-charge layers adjacent to grain boundaries are studied by means of Finite Element Method (FEM) simulations. As an archetypal system for acceptor-doped oxides, a simple defect model of acceptor-doped ceria is implemented, involving the acceptor ions and oxygen vacancies. For the description of space charge, 3 cases are distinguished with regard to the mobility of the acceptor dopant: the Gouy–Chapman case (assuming full mobility of the acceptor dopant), the Mott–Schottky case (assuming a constant acceptor dopant concentration throughout the sample), and the restricted-equilibrium case. In the latter case, the acceptor ions are assumed to be immobile and yet to be possessing a nonuniform concentration profile, which they have attained in a former state of mobility at a higher temperature. From the time-dependent current response to an applied voltage, impedance spectra are calculated and analysed to obtain grain-boundary resistance and capacitance. Special attention is paid to space-charge capacitance, which is inversely proportional to the length of the space-charge layer. The results for the 3 cases, mentioned above, are compared to detect possible errors in the analysis of impedance spectroscopic data. Based on the numerical results, qualitative criteria are formulated that shall help to identify the influence of thermal history on space charge in experimental impedance spectroscopy data.
Authors : Miriam Botros (1), Lucile Bernadet (2), Ling Lin (1), Marc Torrell (2), Ben Breitung (1), Albert Taracón (2,3) and Horst Hahn (1,4)
Affiliations : (1) Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein Leopoldshafen, Germany (2) Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy, Jardins de les Dones de Negre 1, 2nd Floor, 08930 Sant Adria de Besos, Barcelona, Spain (3) ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain (4) KIT-TUD Joint Research Laboratory Nanomaterials Institute of Materials Science, Technische Universität Darmstadt (TUD), 64206 Darmstadt, Hessen, Germany
Resume : The high entropy concept is based on incorporating five or more elements into a single lattice with random occupancy. Thereby, the configurational entropy of the material is increased above a certain threshold stabilizing the crystal lattice and through defect formation, lattice distortion and elemental interactions material properties can be tailored and potentially enhanced. The perovskite-type (Gd0.2La0.2Nd0.2Sm0.2Y0.2)(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 high entropy oxide  was synthesized for the first time using a simple mechanochemical synthesis method. The high temperature stability of the structure as well as its stability against Gd-doped CeO2 (GDC) barrier layer, commonly used for solid oxide fuel cell (SOFC) fabrication, were confirmed by high-temperature X-ray diffraction. The adhesion of the novel material to the GDC pellet was optimized, in addition to the characterization of the electrochemical performance utilizing different cell configurations. This work paves the way to the introduction of high entropy oxides for SOFC applications exploiting their structural stability and tailorable properties. References  C. M. Rost, E. Sachet, T. Borman, A. Moballegh, E. C. Dickey, D. Hou, J. L. Jones, S. Curtarolo, J.-P. Maria, Nat. Commun. 2015, 6, 8485.  A. Sarkar, R. Djenadic, D. Wang, C. Hein, R. Kautenburger, O. Clemens, H. Hahn, J. Eur. Ceram. Soc. 2018, 38, 2318.
Authors : Wolfgang Stein
Affiliations : SURFACE systems+technology GmbH, Hückelhoven
Resume : The development of functional thin film materials is often characterized by typical three steps: the deposition process, a structural preparation and the characterization of the physical properties. Each of these steps is a separated by atmospheric handling and preparation activities. In case of reactive materials such preparation could be done under controlled conditions in glove boxes. But also under protected gas conditions any atmospheric gas contact to the sensitive surface of a complex multi layer film could affect the final film properties. A flexible and adaptable substrate carrier system in combination with interconnected systems could help to avoid atmospheric preparation steps and the possibility of negative influences to the film properties. The complexity of the film itself and the final characterization process demanding the kind of insitu inter action at the sample carrier level. Two ways exist to implement the structural process of the sample: for simple substrate preparation: a flexible carrier based, manipulator actuated moving shutter/mask for complex film or device oriented sample preparation: advanced mask system with exchangeable shadow masks and an integrated mask changing station as part of a multiple process cluster deposition system. In the first case a carrier integrated shutter/mask system allows during the process to shutter differ- ent areas of a sample. This can be actuated from the outside by dedicated manipulation devices and can be done even at the deposition temperature. The shutters are never touching the sample surface at any time. In case of more complex shutter/masking steps the carrier system has to allow the changing of precise masks between the different process steps. A separate mask changing station is necessary to store and exchange the different masks. The final design of these components must always recognize the ther- mal interaction with the substrate and its deposition temperature. The final structure width of the multiple masking processes depends of the proper handling of this thermal management between substrate and mask system. Examples for both versions are shown, including the different steps of in vacuum sample preparation.
Authors : Kudyakova, V.S., Politov, B.V., Markov, A.A., Suntsov, A.Yu., Kozhevnikov, V.L.
Affiliations : Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russia
Resume : Complex non-stoichiometric oxides with doubled perovskite-like structure attract much attention due to a combination of such functional properties as electrical and ionic conductivity, magnetic properties, and oxygen exchange. Because of large concentration of oxygen vacancies and movable oxygen ions in crystal structure these compounds acquire a high sensitivity even to slight changes in temperature and gas-phase composition. Thus oxygen content affecting to defect formation and crystal structure becomes a crucial factor to form required characteristics of oxides. Therefore a comprehensive study of defect formation processes with by conjunction of theoretical and experimental methods is essential to govern the required properties. In the present work solid solutions based on PrBaM2O6–, where Co, Fe and Mn, were obtained by the use of glycerol-nitrate precursors. It was shown that the modification of the cationic sublattice in cobaltite is an effective route for influencing the defect structure, electronic and ionic conductivity, as well as magnetic susceptibility and thermodynamic stability. Based on the simulation of the defective structure of oxides, the equilibrium concentrations of the corresponding defects were calculated in a wide range of temperatures and partial pressures of oxygen in the gas phase, which, in combination with experimental data on high-temperature magnetic susceptibility, made it possible to explain some features of electric transport properties. In particular, the phenomenon of the so-called “spin blockade” was established, which limits the electric transport between neighboring cobalt ions at elevated temperatures. This work was supported by the Russian Science Foundation under grant №19-79-10147
Authors : E. D. Linnik, I. A. Lukyanchuk, A. G. Razunmaya
Affiliations : Faculty of Physics, Southern Federal University, Rostov-on-Don, 344090, Russia; LPMC, University of Picardy Jules Verne, Amiens, 80080, France; Faculty of Physics, Southern Federal University, Rostov-on-Don, 344090, Russia
Resume : Study of the ABO3 ferroelectrics attracts a deep interest due the exceptional properties arising from the paraelectric-ferroelectric phase transition. Harvesting the nonlinear optical and dielectric properties with remarkable piezoelectric properties makes perovskite ferroelectrics advantageous for modern microelectronics. One of the most interesting materials is the SrTiO3, which is often referred as incipient ferroelectric or quantum paraelectric. On cooling the SrTiO3 tends to the ferroelectric instability, which however does not occur even at 4 K. It is supposed to be related to the abnormal quantum fluctuations preventing collective displacement of Ti ions. Apart from that, the SrTiO3 undergoes the antiferrodistortive (AFD) cubic-tetragonal transition at Ta≈105 K, related to the antiphase rotations of the oxygen octahedra and thus, leading to the unit cell multiplicity. Octahedral rotations compete with the ferroelectric order parameter affecting the polar transformations of the SrTiO3. The external influences, such as hydrostatic or chemical pressure, epitaxial strains or external electric field, may result to the dramatically changes of competing behavior of rotational and ferroelectric order parameter. The BaxSr1-xTiO3 with x = 0, 0.01, 0.02 were synthesized by the mechanical mixing of the BaTiO3 and SrTiO3 nanopowders in specified proportions and further sintering. The structural parameters of the BaxSr1-xTiO3 ceramics were determined by the X-Ray diffraction that revealed the cubic-tetragonal phase transition around 100 K. Room temperature Raman spectra of BaxSr1-xTiO3 solid solutions consist of the second-order bands appearing from complex phonon interactions from the whole Brillouin zone. On cooling Raman spectra reveal the arising of the folded Eg + B1g modes from R-point at 113, 103 and 93 K for SrTiO3, Ba0.01Sr0.99TiO3 and Ba0.02Sr0.98TiO3 ceramics, respectively. Therefore we may conclude, that small additives of Ba ions with bigger atomic radius influences the collective oxygen rotations in SrTiO3 matrix leading to the decrease of AFD transition temperature. Apart from that, Raman spectra of the BaxSr1-xTiO3 ceramics comprise the TO2 and TO4 polar modes forbidden in the paraelectric phase. The presence of TO2 and TO4 modes in Raman spectra in temperature range 4-300 K witnesses the forming of the polar nanoclusters in pure and Ba-doped SrTiO3 matrix. Temperature dependence of their intensities is characterized by kink-like behavior with special temperature points 103, 113, 123 K for SrTiO3, Ba0.01Sr0.99TiO3 and Ba0.02Sr0.98TiO3, respectively. They are supposed to be the critical temperatures of nanoregions extension and increase with Ba doping. We conclude therefore that polar displacement of the Ti atoms caused by the Ba-induced activation of polar nanoregions suppresses the TiO6 oxygen octahedra rotations, that is also confirmed by the previously described competition of the ferroelectric and AFD order parameters.
Authors : Masoud Akbari 1*, Abderrahime Sekkat 1, Viet Huong Nguyen 2, Skandar Basrour 3, Kevin Musselman 4 and David Muñoz-Rojas 1
Affiliations : 1 Laboratoire des Matériaux et du Génie Physique (LMGP), CNRS, University of Grenoble Alpes, F-38000 Grenoble, France 2 Faculty of Electrical and Electronic Engineering, Phenikaa University, Hanoi 12116, Vietnam 3 TIMA Laboratory, University of Grenoble Alpes, F-38000 Grenoble, France 4 Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, N2L 3G1 Canada
Resume : Among semiconducting metal oxides, tin oxide (SnOx) and zinc oxide (ZnO) have gained much attention due to their unique properties, such as high transparency in visible light and low resistivity. In the case of SnOx, it also offers an excellent thermal and chemical stability . Hence, these oxides have been used for a vast variety of applications including photovoltaics, gas sensing, catalysis, and optoelectronics . The fast development of nanotechnology relays on a low-cost and facile control of the properties of oxide thin films at the nano scale for the above mentioned applications. Recently, Atmospheric-Pressure Spatial Atomic Layer Deposition (AP-SALD) has proven to be an excellent deposition technique that is capable of producing high quality metal oxide thin films with precision control, while being up to 2 orders of magnitude faster than conventional ALD, and working at atmospheric pressure . Recently, we developed ZnO-Based transparent conductive films deposited with our home-made AP-SALD for gas sensing . While ALD has already been utilized effectively for deposition of SnOx , there are only a few works so far dealing with the deposition of SnOx films by SALD, mostly for application in photovoltaics . In this work, we present a complete study on the deposition of SnOx thin films by AP-SALD using different deposition conditions and oxidizers. Growth rates of about 0.15 nm/min/cm2 are achieved at low-temperature (< 220 °C) and open-air conditions. Structural, optical, chemical and electrical properties of the SnOx thin films will be shown and discussed in detail. Some results of using SnOx and ZnO thin films as an active layer for gas sensing application will be also presented. References: 1. E. Comini, G. Faglia, and G. (Giorgio) Sberveglieri, Solid State Gas Sensing (2009). 2. Y. Deng, Semiconducting Metal Oxides for Gas Sensing (2019). 3. D. Muñoz-Rojas and J. Macmanus-Driscoll, Mater. Horizons 1, 314 (2014). 4. V. H. Nguyen, D. Bellet, B. Masenelli, and D. Muñoz-Rojas, ACS Appl. Nano Mater. 1, 6922 (2018). 5. D. V. Nazarov, N. P. Bobrysheva, O. M. Osmolovskaya, M. G. Osmolovsky, and V. M. Smirnov, Rev. Adv. Mater. Sci. 40, 262 (2015). 6. L. Hoffmann, D. Theirich, D. Schlamm, T. Hasselmann, S. Pack, K. O. Brinkmann, D. Rogalla, S. Peters, A. Räupke, H. Gargouri, and T. Riedl, J. Vac. Sci. Technol. A Vacuum, Surfaces, Film. 36, 01A112 (2018). 7. L. Hoffmann, K. O. Brinkmann, J. Malerczyk, D. Rogalla, T. Becker, D. Theirich, I. Shutsko, P. Görrn, and T. Riedl, ACS Appl. Mater. Interfaces 10, 6006 (2018).
Authors : Joana S. Teixeira1,2, Rui S. Costa,1,2 André M. Pereira2, Clara Pereira1
Affiliations : 1 REQUIMTE/LAQV, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto (FCUP), Portugal. 2 IFIMUP, Institute of Physics for Advanced Materials, Nanotechnology and Photonics, Department of Physics and Astronomy, FCUP, Portugal.
Resume : The Era of the Internet of Things allied to the paradigm of Sustainable Energy unleashed a new challenge for energy storage and harvesting, involving the development of all-in-one autonomous smart textile devices that combine both properties. Thermoelectric devices are considered a promising energy harvesting technology since they allow harvesting wasted thermal energy (provided from industry or from our body) to power low-consumption electronic devices. However, they can only generate electricity in an intermittent manner. Energy storage solutions, namely supercapacitors (SCs), have the capability to cope with the intermittent nature of energy production fluctuations. The hybridization of both technologies in a single device, the so-called thermally-chargeable SCs, is a new and super innovative field that is in expansion, opening promising perspectives for the fabrication of efficient wearable/flexible and lightweight autonomous devices. Herein, hybrid nanomaterials based on carbon nanotubes functionalized with manganese(II) ferrite magnetic nanoparticles (CNT@MnFe2O4) were produced and used as active electrode materials for the fabrication of novel dual-functional magnetic thermally-chargeable textile SCs (TCSCs) with multifunctional properties – magnetism, energy storage and harvesting. The hybrid nanomaterials were prepared by a one-pot coprecipitation route, using two different MnFe2O4 loadings relatively to CNT material (25 and 50 wt%, theoretical). The characterization results confirmed the presence of nearly spherical MnFe2O4 nanoparticles immobilized on the CNTs surface, with average diameter of ~5 nm, regardless of the MnFe2O4 loading. Asymmetric magnetic textile TCSCs were then fabricated in a sandwich-type configuration, using textile fabrics coated with the as-prepared hybrid nanomaterials as electrodes and a solid-gel electrolyte. A maximum working potential of 2.05 V, an energy density of 13.38 W h g-1 and a power density of 130.93 W kg-1 were achieved for the asymmetric SC based on the 50 wt% CNT@MnFe2O4 hybrid. Remarkably, enhancements of 14% on the operation potential, 111% on the energy density and 13% on the power density were reached for the TSCS relative to the symmetric CNT-based SC owing to the simultaneous occurrence of redox reactions and a non-Faradaic type charge storage mechanism. Finally, it was proved that the all-in-one textile TCSCs besides storing energy, present the ability to generate energy when a temperature gradient is applied between the electrodes. These hybrid devices are a novel and promising solution as thermal energy harvesting/energy storage technology to power low-consumption small-scale electronic devices. Acknowledgments. Funded by FEDER through COMPETE 2020 and by FCT/MCTES under Program PT2020 (projects PTDC/CTM-TEX/31271/2017, UIDB/50006/2020 and UIDB/04968/2020). JST and CP thank FCT for PhD scholarship (SFRH/BD/145513/2019) and FCT Investigator contract (IF/01080/2015), respectively.
Authors : a,b Bouthayna Alrifai*, a Mohammad Kassem, a Maria Bokova, b Joumana Toufaily, a Eugene Bychkov
Affiliations : a ULCO University, LPCA laboratory (EA 4493), F-59140 Dunkerque, France b Lebanese University, Doctoral School for Science and Technology (EDST), LEADDER/MCEMA laboratory, faculty of Sciences, Hadath, Lebanon
Resume : Amorphous chalcogenide materials have received worldwide interest in both fundamental research and technological fields. They are suitable for various solid-state device applications in electronics, photonics and sensor fields. Using these chalcogenide materials in the field of environmental monitoring and industrial process control, as chemical sensors for detection of heavy metal ions as Pb, Hg, Cu, Cd, etc., is the aim of our research activity. In this context, establishing the relations between the materials composition, structure, and ionic/electronic transport properties is a must for the development of active membrane materials in the fabrication of the Pb(II)-ISEs (Ion-Selective-Electrode). To this end, novel chalcogenide glasses in the AgI-PbS-As2S3 system have been synthesized and characterized for the first time. The X-ray diffraction shows that the (AgI)x(PbS)0.5–x/2(As2S3)0.5–x/2 , 0.0 ≤ x ≤ 0.7, alloys are amorphous up to x = 0.6. Macroscopic properties measurements such as glass transition temperature (Tg), density (d), and total conductivity (σ) have been performed. The density increases monotonically with increasing x, while Tg decreases significantly from 197 to 76°C. The ionic conductivity increases by 11 orders of magnitude (from ~ 10^-16 S cm-1 to 10^–3 S cm-1) with increasing Ag+ ion concentration while the activation energy decreases from ~ 1 to 0.1 eV. The obtained Raman spectroscopy measurements provide an insight to the materials structural motifs and their relation to transport changes in AgI-PbS-As2S3 glasses.
Authors : Valerio Gulino (a)(b), Matteo Brighi (c), Peter Ngene (a), Radovan Černý (c), Marcello Baricco (b) and Petra de Jongh (a)
Affiliations : (a) Materials Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, The Netherlands; (b) Department of Chemistry and Inter-departmental Center Nanostructured Interfaces and Surfaces (NIS), University of Turin, Via Pietro Giuria 7, 10125 Torino, Italy; (c) Laboratoire de Cristallographie, DQMP, Université de Genève, quai Ernest-Ansermet 24, CH-1211 Geneva 4, Switzerland;
Resume : Solid-state electrolytes (SSEs) are promising candidates for resolving the intrinsic limitations of the organic liquid electrolytes currently employed in Li-ion batteries. Nevertheless, an SSE must fulfil several requirements to be employed in an all-solid state battery (SSB), such as high ionic conductivity. Complex hydrides (e.g. LiBH4) are suggested as solid-state electrolytes. Among the different polymorphs of LiBH4, only the hexagonal phase, which is stable at temperatures above 110°C, has a high ionic conductivity (~10-3 S cm-1 at 120 °C). To practically access a room temperature (RT) SSB, a promising approach to enhance the Li-ion conductivity of LiBH4 at RT is the development of new high conductive interface by mixing it with oxide nanoparticles (such as SiO2, Al2O3 and MgO). In this work the Li-ion conductivity of LiBH4 has been enhanced by means of MgO-mixing, optimizing the composition of composites in order to obtain a RT operating SSE. The optimum composition of the mixture results 53 v/v % of MgO, showing a Li-ion conductivity of 2.86 10-4 S cm-1 at 20 °C, four order or magnitude higher than pure LiBH4 and comparable to the Li-ion conductivity of a liquid electrolyte. The improved Li-ion conductivity relies on the formation of a conductive interface that has been described by a core-shell model where the fraction of LiBH4 (the core) is in direct contact with the oxide (the shell). The formation of the composite does not affect the electrochemical stability window, which is similar to that of pure LiBH4 (about 2.2 V vs. Li /Li). The mixture has been incorporated as solid-electrolyte in a TiS2/Li all-solid-state Lithium metal battery. A freshly prepared battery failed at RT after only 5 cycles. On the other hand, a stable solid electrolyte interphase can be obtained by a pre-conditioning cycling at 60 °C. Afterward, a capacity retention of about 80 % at the 30th cycle was obtained operating at RT. We illustrate that the addition of oxide nanoparticles to LiBH4 offers a promising strategy to obtain novel SSE candidates for Li-based SSB. (1) Matsuo, M.; Nakamori, Y.; Orimo, S.; Maekawa, H.; Takamura, H. Lithium Superionic Conduction in Lithium Borohydride Accompanied by Structural Transition. Appl. Phys. Lett. 2007, 91 (22), 224103. (2) Gulino, V.; Barberis, L.; Ngene, P.; Baricco, M.; de Jongh, P. E. Enhancing Li-Ion Conductivity in LiBH4-Based Solid Electrolytes by Adding Various Nanosized Oxides. ACS Appl. Energy Mater. 2020, 3 (5), 4941–4948.
Authors : *Christin Böhme, *Matthäus Siebenhofer, *Ghislain M. Rupp, *Jürgen Fleig, *Markus Kubicek
Affiliations : *TU Wien, Institute of Chemical Technologies and Analytics, Austria
Resume : Oxygen exchange properties of mixed ionic and electronic conducting oxides are affected by temperature and oxygen partial pressure as well as by specific material properties such as lattice strain. Tensile lattice strain in La0.6Sr0.4CoO3–𝛿 (LSC) thin films, for example, accelerates the oxygen surface exchange and diffusion kinetics in contrast to compressive strain . In this work, we use in-situ impedance spectroscopy during pulsed laser deposition to investigate the oxygen exchange properties of multilayered LSC|La0.6Ba0.4CoO3–𝛿 (LBC) thin film electrodes. Individual layers are grown on yttria-stabilized zirconia with respective layer thicknesses ranging from 0.5 nm - 20 nm at 500 ℃ - 600 ℃ and an pO2 of 0.04 mbar. Since LSC and LBC exhibit similar lattice parameters, a particular focus is laid on elucidating if and how lattice strain between the single layers may influence the chemical capacitance (Cchem) and thus, the defect chemistry of the multilayered system. For structural characterization X-ray diffraction is used. Moreover, high-resolution transmission electron microscopy measurements are planned to gain further insight into the structure of the multilayered electrode. Our measurements show that the absolute value of Cchem abruptly changes within the first 1 nm - 2 nm of a new layer for both LSC and LBC. These steps might be the product of strain effects and/or cation interdiffusion between the single LSC and LBC layers. Furthermore, analyzing the resistance of the multilayered electrode reveals that the oxygen exchange kinetics switch between LSC and LBC surface limitation. In accordance with literature , faster oxygen exchange is observed for the LBC layers. References  Markus Kubicek, Zhuhua Cai, Wen Ma, Bilge Yildiz, Herbert Hutter, and Jürgen Fleig. “Tensile Lattice Strain Accelerates Oxygen Surface Exchange and Diffusion in La1−𝑥Sr𝑥CoO3−𝛿 Thin Films”. In: ACS Nano 7.4 (2013), pp. 3276–3286. doi: 10.1021/nn305987x.  Ghislain M. Rupp, Alexander Schmid, Andreas Nenning, and Jürgen Fleig. “The Superior Properties of La0.6Ba0.4CoO3−𝛿 Thin Film Electrodes for Oxygen Exchange in Comparison to La0.6Sr0.4CoO3−𝛿”. In: Journal of The Electrochemical Society 163.6 (2016), F564–F573. doi: 10.1149/2.1061606jes.
Authors : Sudipta Biswas, Ananya Chowdhury, A Dhar, P S Burada, and Amreesh Chandra*
Affiliations : Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
Resume : As we move towards next generation applications for supercapacitors, it is imperative to characterize their performance under non-ambient and/or inconvenient environments. These include: changing magnetic field, temperature, external shocks or vibrations, etc. I will discuss the effects of all these external parameters on the device performance, which can open a new direction in the field of supercapacitor research. The strategy of exposing the supercaps to magnetic field before their real application can enhance the deliverable specific capacitance. In supercapacitors, fabricated using ferromagnetic metal oxides such as Fe2O3, MnO2, etc., nearly 170% increase in energy density, at 1 A g−1, was observed by varying the magnetic field from 0 to 5 mT. In addition, a ten-fold increase in the power density can be obtained. The observations are attributed to the changing Lorentz force and/ or magneto-hydrodynamic effects. Therefore, one may argue that size of the electrolyte ion should also be considered. It is clearly shown that this hypothesis, which predicts ‘change in specific capacitance’ by varying electrolyte, is correct. Till date, a Nernstian relation across the electrode is used to explain the super capacitive behaviour of a cell. The theoretical formulations proposed in the Gouy Chapman or the Stern models have no parameters that consider the consequences of a varying magnetic field. It is shown that the net charge flux is essentially dominated by the diffusive transport of the ions. The modified theory leads to consistent results, which are corroborated with the experimental data. In B=0 limit, the model reduces to the earlier mentioned established theoretical postulates
Authors : Alexander G. Squires, Jacob M. Dean, Benjamin J. Morgan
Affiliations : Department of Chemistry, University of Bath, Claverton Down BA2 7AY, United Kingdom and The Faraday Institution, Quad One, Harwell Science and Innovation Campus, Didcot OX11 0RA, United Kingdom
Resume : A common strategy for increasing the ionic conductivity of solid electrolytes is aliovalent doping to form charge-compensating mobile native defects. For the antiperovskite lithium-ion solid electrolyte Li3OCl, both supervalent (donor) and subvalent (acceptor) doping schemes have been proposed as routes to increase numbers of mobile lithium vacancies and lithium interstitials, respectively. These doping schemes rely on two assumptions: first, that aliovalent doping preferentially promotes the formation of lithium defects over competing native defects; and second, that additional mobile lithium defects can be formed in sufficiently high concentrations to meaningfully enhance the ionic conductivity. To assess the scope for enhancing mobile defect concentrations, and hence ionic conductivities, through aliovalent doping in Li3OCl, we have performed a hybrid density-functional theory study of the defect chemistry and subvalent/supervalent-doping response of this material. We find that under typical synthesis conditions the dominant native defects are V_Li, O_Cl, and V_Cl. Supervalent (acceptor) doping increases the concentrations of both V_Li and O_Cl, with the preferentially-formed defect species dependent on the thermodynamic conditions; chemical potential regimes in which O_Cl is favoured over V_Li show reduced ionic conductivity on doping. Subvalent (donor) doping promotes the formation of V_Cl ahead of Li_i, and results in a nonmonotonic increase in lithium conductivity owing to the reduction in lithium vacancy concentration. This contrast with the predictions of simple defect-pair charge-compensation models highlights the importance of considering a full self-consistent thermodynamic model of native defect species when considering the effects of aliovalent doping in solid electrolytes
Authors : Raphael Ahlmann (1), Ilia Valov (2), Stefan Tappertzhofen (1)
Affiliations : (1) Chair for Micro- and Nanoelectronics, TU Dortmund University, Dortmund, Germany; (2) Peter-Grünberg-Institut (PGI 7), Forschungszentrum Jülich, Jülich, Germany
Resume : Gas sensors are key components for a broad range of applications. Oxygen sensors are used in numerous battery-powered smart devices. In the transition to environmentally friendly mobility, hydrogen sensors are essential to detect smallest amounts of gas in case of leakage, for safety reasons. These applications demand for low-cost, low-power, robust, and ideally configurable thin-film gas sensors. In our previous work we already analyzed the interaction of ambient oxygen, moisture, and hydrogen with memristive devices. We now suggest exploiting these electrochemical interactions and the resistive switching effect to fabricate re-programmable memristive gas sensors. In this study we report on fundamental electrochemical interactions of the partial pressure of water, hydrogen and oxygen with the interface, the filament and on the resistive switching properties, and discuss how degradation and drift phenomena could be compensated by re-programming schemes. Due to the micro- to nanoscale sensing volume fast a response time is achievable. Further advantages of our approach are ultra-low power consumption, CMOS-friendly integration, and low-cost mass-fabrication.
Authors : Soukaina Mountadir*(a), Victor Duffort(a), Rose Noëlle Vannier(a)
Affiliations : (a) Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
Resume : Solid Oxide Fuel Cells (SOFC) have received great attention this last decade due to their high electrical efficiency (60%), durability, low cost and fuel flexibility (hydrogen, methane, ...).1 Yttria Stabilised Zirconia (YSZ) is the reference electrolyte used in these cells. However, it is a mediocre ionic conductor limiting the operational temperature range above ~700 °C. These high operating temperatures result in engineering challenges and long switch-on time. In order to decrease the operating temperature, a recent study has shown that by using a bilayer electrolyte, formed of erbium stabilized bismuth oxide (ESB) and gadolinium doped ceria (GDC), it was possible to lower the operating temperature to 500 °C and below. The applicability of these bilayer electrolytes was demonstrated with several different cathode materials, such as the composite cathode ESB/La0.8Sr0.2MnO3 which led to a power density of ~1 W.cm-2 at 650 °C.2 In the aim to prepare such bilayer electrolyte for the search of new cathode materials, in this study we focused on the deposition, using spin coating, of thin and dense layers of ESB on a GDC substrate. In particular we will present the syntheses that we developed, using wet chemical co-precipitation and a citrate procedure, in order to minimize the size of the ESB powders. Due to the mixing efficiency of these two methods, we were able to prepare the stabilized cubic structure at temperature as low as ~500 °C. The resulting powders exhibit grain sizes as small as 600 nm in the case of the citrate procedure. The two precursors were used to formulate inks based on an ethanol dispersion and a polyvinyl butyral binder. Scanning Electron Microscopy and Energy-Dispersive X-ray spectroscopy were used to reveal the high quality of the ESB layers obtained with the precursor synthesized through the citrate route. Acknowledgements Agence Nationale de la Recherche - BIBELOT ANR-18-CE05-0001, The Fonds Européen de Développement Régional (FEDER), CNRS, are acknowledged for funding. References  D. M. Bierschenk, J. R. Wilson and S. A. Barnett, Energy Environ. Sci., 2011, 4, 944–951.  E.D. Wachsman, K.T. Lee, Science, 334 (2011), 935-939.
Authors : Gaurav Lole, Vladimir Roddatis and Christian Jooss
Affiliations : Institut für Materialphysik, Georg-August-Universität Göttingen, Germany.
Resume : Understanding the active state of electrocatalysts in operando conditions is essential for improved understanding of mechanism and rational design of efficient and stable systems. Environmental transmission electron microscopy (ETEM) can contribute to this topic since it offers a comprehensive study of interactions of catalyst surfaces in controlled environment of water, in different reactive and non-reactive gases1, in electric potentials2 and at atomic column resolution. Here, we study the atomic dynamics of manganese (Mn) adatoms at single crystalline surface of La1-xSrxMnO3 (x=0.4) (LSMO) and Pr1-xCaxMnO3 (x=0.33) (PCMO) manganites in high vacuum (HV), reactive environment (H2O, O2) and in inert atmosphere (N2). Surface termination plays important role during OER process. Furthermore, the as prepared surface transform to catalytically active terminated surface3. Along with atomic dynamics we studied surface termination for different reactive and non-reactive gases for the LSMO and PCMO (001) surfaces. To study the atomic dynamics precisely we compared the experimental images to the images simulated using a Monte–Carlo-based least-squares optimization of simulated images based on the multislice method. The optimal electron optical parameters and thickness are obtained by contrast fitting. LSMO shows reversible Mn adatom mobility on top of stable A-site cations, whereas fast leaching behaviour is observed for PCMO. Our studies shed light on the role of Mn adatoms mobility and Mn leaching on manganite perovskite interfaces to H2O for the oxygen evolution catalysis in electrochemical water oxidation. It implies that partial solvation of active Mn surface adatoms might be essential for the understanding of the active state of Mn-O based catalyst and opens new perspectives in atomic scale design of efficient and stable electrode surfaces for OER. Reference 1. Ch. Jooss S. Mildner, M. Beleggia, D. Mierwaldt, V. Roddatis in “Controlled Atmosphere Transmission Electron Microscopy - Principles and Practice”, edited by Jakob Birkedal Wagner and Thomas Willum Hansen, Springer 2016 2. S. Mildner, M. Beleggia, D. Mierwaldt, Th. W. Hansen, J. B. Wagner, S. Yazdi, T. Kasama, J. Ciston, Y. Zhu, and Ch. Jooss, Environmental TEM Study of Electron Beam Induced Electrochemistry of Pr0.64Ca0.36MnO3 Catalysts for Oxygen Evolution J. Phys. Chem. C, 119 (2015) 5301–5310. 3. Gaurav Lole, Vladimir Roddatis, Ulrich Ross, Marcel Risch, Tobias Meyer, Lukas Rump, Janis Geppert, Garlef Wartner, Peter Blöchl & Christian Jooss, Dynamic observation of manganese adatom mobility at perovskite oxide catalyst interfaces with water. Commun Mater 1, 68 (2020). 4. V Roddatis, G Lole and Ch Jooss, In situ preparation of Pr1-xCaxMnO3 and La1-xSrxMnO3 catalyst surface for high resolution environmental transmission electron microscopy. Catalysts 9(9), 751 (2019).
Authors : Lucy M. Morgan, Benjamin J. Morgan, M. Saiful Islam
Affiliations : University of Bath, The Faraday Institution
Resume : The development of fast-ion-conducting solid electrolytes for use in all-solid-state batteries requires a detailed understanding of the key structural principles that give high ionic conductivities in specific materials. Lithium argyrodites based on Li6PS5X (X= Cl, Br, or I) are promising lithium ion solid electrolytes with room temperature ionic conductivities of up to 10-2 S cm-1. Recent experimental studies of these materials have shown that introducing subvalent cations into the host framework to give lithium stoichimetries x(Li)>6 can give significant increases in lithium ion conductivities. The microscopic cause for this behaviour is uncertain, however, and has been attributed in different studies to either a change in the anion substructure, or to purely the increase in lithium stoichiometry. To better understand the relationship between lithium stoichiometry, host-framework composition, and lithium conductivity in the lithium argyrodites we have performed a series of molecular dynamics studies on the series Li6 xPS5 xI1-x. To help deconvolve the coupled effects of changing the framework composition and changing the lithium stoichiometry in these stoichiometric systems, we have performed further simulations of non-stoichiometric systems, allowing us to vary each parameter independently. From these simulations we find a much greater effect from varying the host-framework stoichiometry than from varying lithium stoichiometry, and conclude that it is the change in framework chemistry, rather than lithium stoichiometry, that underpins the trends reported in previous experimental studies. A mechanistic analysis shows that lithium diffusion is effected by concerted motion of lithium ions at all stoichiometries. The quantitative mechanistic behaviour, however, does vary with host-framework composition (and to a lesser extent, with lithium stoichiometry) which we attribute to differing degrees of disorder in the lithium substructure.
Authors : Necmettin Kilinc1*, Senem Sanduvac2, Mustafa Erkovan3,4
Affiliations : 1Department of Physics, Faculty of Science & Arts, Inonu University, Malatya, Turkey 2Bünyan Vocational College, Kayseri University, Kayseri, Turkey 3Instituto de Engenharia de Sistemas E Computadores – Microsistemas e Nanotecnologias (INESC MN), Lisboa, Portugal 4Department of Computer Engineering, Beykoz University, Istanbul, Turkey
Resume : Hydrogen (H2) gas sensing properties of ultrathin platinum (Pt) and Pt - nickel (Ni) alloy films deposited on a glass substrate by co-sputter technique are investigated depending on alloy composition, temperature, and H2 concentration. The structural properties of ultrathin Pt and Pt-Ni alloy films are characterized by XRD, SEM, and EDS techniques. The amount of Ni atom in the alloy thin films is increased from 0 % up to 60 % and the H2 sensing properties of the alloy film sensors are examined in the concentration range of 25 ppm - 1000 ppm H2 at the temperature range from room temperature to 200 C. In order to measure four-point resistance measurements, four Au pad electrodes are contacted on the top of ultrathin Pt and Pt-Ni alloy films for H2 gas sensing measurements by using a thermal evaporator. The results revealed that the H2 sensing mechanism of the same thickness pure Pt and Pt-Ni alloy films could be explained with surface scattering phenomenon, and the ultrathin Pt79-Ni21 alloy film exhibited the best sensing performance to H2 at all measured temperature range. The limit of detection for ultrathin Pt and Pt-Ni alloy films is calculated as lower than 1 ppm and the response times of the films are decreased with rising H2 concentration and temperature. Acknowledgment: This study was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) with a project number of 114M853.
Authors : G. Hari Priya1, K.M.K. Srivatsa2, P. Koteswara Rao1
Affiliations : 1Department of Electronic Science, Delhi University (South Campus), India 2CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110012, India
Resume : Defects at the interface of high-k/semiconductor have a significant role on the reliability of metal-insulator-semiconductor (MIS) devices. Titanium oxide (TiO2) layers were developed by reactive sputtering on p-Si substrates at room-temperature and annealed at different annealing temperatures in the range, 400-900 oC under Ar ambient. The interfacial characteristics of TiO2/Si were studied using capacitance-voltage and current-voltage measurements by evaluating flat-band voltage (VFB), interface defect density (Dit), fixed charge density (Qeff), etc. The Dit at the interface of TiO2/Si was found to be 2.8x1012 eV-1cm-2 for room temperature (RT) deposited films, which reduced nearly by one order (4.6x1011 eV-1cm-2) at annealing temperature of 700 oC. Flat-band voltage (VFB) values changed from 0.6 V to 2.1 V when the annealing temperature varied from RT to 700 oC, revealing the presence of negative fixed charges in the layers. The leakage current density was found to be as low as 8.4x10-7 A/cm2. The defect levels were also evaluated using deep-level transient spectroscopy and the traps are found to be majority carrier type. The layers have shown strong photoluminescence at the wavelengths of 574 nm and 675 nm above the annealing temperatures of 600 oC, and intensity of which enhanced remarkably at the higher annealing temperatures, indicating the reduction of non-radiative transitions. The study demonstrated the importance of processing conditions in developing the devices with minimum interface defects.
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HARVESTORE sponsored session: Interface & Surface Phenomena (II) : Nini Pryds
Authors : Mark Huijben
Affiliations : MESA Institute for Nanotechnology, University of Twente, Netherlands
Resume : Solid-state batteries offer great potential for large improvements in safety and lifetime, as well as higher energy and power densities. However, the interfacial composition and structure between solid electrolytes and electrode materials often present major deviations from those of the bulk materials. Elucidating the nature of the involved interfaces is required to establish a rational approach towards the successful combination of materials in a new generation of solid-state cells. Controlled interfaces between a solid-state electrolyte (Li0.33La0.5TiO3), cathode (LiMn2O4) and anode (LI4Ti5O12) have been realized in 2D-planar and 3D-vertical thin film geometries by applying pulsed laser deposition. The influence of the temperature and deposition rate on the morphology evolution of lithium-based vertically aligned nanocomposites is modelled by applying Kinetic Monte Carlo Simulations with activation energies for hopping obtained experimentally and with minimum restrictions for hopping directions. Epitaxial engineering is used to control the crystal orientation within the 2D and 3D geometries, which enables a unique insight into the relation between electrochemistry and crystal directionality of such chemically complex inorganic interfaces, not obtainable in single crystals or polycrystalline samples. D.M. Cunha et al., ‘Morphology Evolution during Lithium-Based Vertically Aligned Nanocomposite Growth’, ACS Appl. Mater. Interfaces 2019, 11, 44444−44450.
Authors : A.Morata(a), V. Siller(a), F.Chiabrera(a), M. Nuñez(a), R. Trocoli(a), M. Stchakovsky(b), A. Tarancón (a,c)
Affiliations : (a)Department of Advanced Materials for Energy Applications, Catalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1, 08930 Sant Adrià del Besòs, Barcelona, Spain (b) HORIBA Scientific, Avenue de la Vauve, Passage Jobin Yvon, 91120 Palaiseau, France (c)ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain
Resume : Thin film solid state batteries are called to play a prominent role as a power supply for future micro-devices. Despite few commercial solutions exist, many efforts are still invested in the development of such devices with improved capabilities. The challenge is to develop appropriate electrodes with high capacity, stability and fast performance, and electrolytes with a low ionic resistance at room temperature. Furthermore, it is crucial to pay attention to the electrochemical compatibility between the components and to provide good quality interfaces. Here we present the development of LiMn2O4 (LMO) and Li4Ti5O12 spinel electrodes, and Li1 xAlxTi2-x(PO4)3 electrolyte thin films. The materials have been deposited by means of Large Area Pulsed Laser Deposition (LA-PLD), using multi-layering strategies to balance lithium content of the films. Exhaustive structural and electrochemical characterization of the layers has been carried out. In particular, recently developed operando spectroscopic ellipsometry and Raman spectroscopy techniques have been used for the study of ion-transport phenomena and the track of Lithium content and volume expansion during cycling.
Authors : Jordi Sastre, Xubin Chen, Abdessalem Aribia, Moritz H. Futscher, Ayodhya N. Tiwari, Yaroslav E. Romanyuk
Affiliations : Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
Resume : Thin film deposition techniques can be useful for the fabrication of better solid-state batteries. Reducing the thickness of the electrolyte material to a few hundred nanometers facilitates ionic conductance for faster charge-discharge and reduces the total volume of inactive material, therefore increasing energy density. Lithium garnet Li7La3Zr2O12 (LLZO) electrolyte is a promising ionic superconductor for solid-state lithium batteries. In bulk, this material has demonstrated high ionic conductivities (0.1 - 1 mS/cm), as well as a wide electrochemical stability window (against metallic lithium anode and high potential cathode materials). However, processing this ceramic material in the form of films presents still some challenges. We present a method for fabricating crystalline LLZO thin films at about 700°C (significantly below the standard processing temperatures of about 1100°C) with densities and ionic conductivities comparable to the values observed in bulk ceramic pellets. By engineering the interface between a thin film LiCoO2 cathode and the solid-state electrolyte, we demonstrate a low interfacial resistance between cathode and electrolyte. For the first time a functional thin film lithium battery with sputtered ceramic LLZO as solid-state electrolyte is demonstrated.
Authors : R. Xia, Y. Wang, M. Huijben, J.E. ten Elshof
Affiliations : R. Xia, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands; Y. Wang, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands; M. Huijben, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands; J.E. ten Elshof, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands.
Resume : Energy storage is essential for many applications such as portable electronic devices and electric vehicles. Lithium ion batteries (LIBs) are the most commonly used energy storage devices because of their high energy density and stability over repeated charge-discharge cycling. High rate performance of LIBs is nowadays one of the most important requirements for electric vehicles. However, due to the limitations of conventional graphite anodes, the charge-discharge process of the battery is limited to 1 C (or even lower). Titanium-based oxides are promising candidates to fulfill those requirements. However, in order to reach high power density, researchers usually use strategies like incorporation of carbon within the composites and/or a mesoporous structure design, which reduce the volumetric capacity. Niobium tungsten oxides have recently been shown to exhibit very fast (dis)charging capacity owing to their stable host structure suitable for lithium diffusion. It was originally suggested that dimensional reduction of the material would have a negligible effect on its electrochemical performance, and recent studies on 300 nm thick nanofibers seemingly confirmed that hypothesis by failing to demonstrate enhanced energy storage property in comparison to bulk materials. However, in this contribution we will provide conclusive evidence for the dependence of the lithiation process of Nb18W16O93 anodes on the grain size. We will show that the lithiation dynamics of niobium tungsten oxide are significantly enhanced when the secondary grain size is below 100 nm. This study provides a new perspective on the importance of nanoscaling this material to further improving the electrochemical performance of Nb18W16O93 anodes for realizing fast (dis)charging for future energy storage devices.
|11:00||OPEN DISCUSSION SESSION|
Solid State Energy Devices (III): Solid Oxide Cells : TBC
Authors : Sandrine Ricote 1, Steven Pirou 2, Xanthi Georgolamprou 2, Ragnar Kiebach 2, Alexis Dubois 3, Robert J. Kee 1
Affiliations : 1 Colorado School of Mines, 1500 Illinois Street, CO 80401 Golden, USA; 2 Technical University of Denmark, DTU Energy: Department of Energy Conversion and Storage, Anker Engelunds Vej, 2800 Kgs. Lyngby, Denmark; 3 HyET Hydrogen USA LLC, 43 Rock Lane, CA 94708, Berkeley, USA;
Resume : Proton-conducting ceramics, such as yttrium doped barium zirconates/cerates referred to as BZCY, are studied for intermediate temperature applications, including protonic-ceramic fuel/electrolysis cells, electrochemical compressors, or catalytic membrane reactors. In the presence of steam, the material hydrates with the consumption of oxygen vacancies and the formation of protonic defects. Hydration-induced chemical expansion (lattice expansion upon protonic defect formation) can be critical during the sample preparation and testing. Techniques for thermal and chemical expansion measurements will be presented together with challenges associated with analysis and interpretation. A short overview of the literature data on the expansion in proton-conducting ceramics will be provided. While all these measurements are performed in a single atmosphere, it is important to predict the expansion with different gas compositions on both sides of the membrane, thus representing real device applications. To do so, we developed a computational model based on a Nernst-Planck-Poisson formulation and included a chemo-thermo-mechanical component. Examples of crack formation due to uncontrolled hydration on symmetrical cells (BZCY-NiO//BZCY//BZCY-NiO) prepared by tape-casting will be shown.
Authors : Giulia Raimondi (1), Alessandro Chiara (2), Francesco Giannici (2), Alessandro Longo (3), Chiara Cavallari (3), Antonino Martorana (2), Rotraut Merkle (1), Joachim Maier (1)
Affiliations : (1) Max Planck Institute for Solid State Research, Physical Chemistry of Solids, Stuttgart, Germany. (2) Universita’ degli Studi di Palermo, Dipartimento di Fisica e Chimica, Palermo, Italy. (3) European Synchrotron Radiation Facility, Grenoble, France.
Resume : BaFeO3-δ perovskites with mobile oxygen vacancies, holes, and protons, can be used as cathode material for Protonic Ceramic Fuel Cells (PCFC). Their mixed conductivity including protons is important to make the whole cathode surface active for oxygen reduction. The proton concentration in such cathode perovskites was determined by thermogravimetry. [1,2] Crystal structure, symmetry and local lattice distortions have an important impact on the proton uptake. Partial substitution of Fe by redox-inactive and oversized Zn2+ or Y3+ is beneficial for proton uptake.  This can be assigned to local lattice distortions decreasing the covalency of Fe-O bonds. This enhances the basicity of the oxygen ions, which is important for dissociative water incorporation via an acid-base reaction. The local environment and bonding of the cations and of O2- is probed using Extended X-Ray Absorption Fine Structure (Fe,Zn,Y K-edges) and X-Ray Raman Scattering (O K-edge) for oxidized ("Fe4+"), reduced ("Fe3+") samples.  The rather small Fe edge shift between reduced and oxidized samples and strong pre-edge features at the O K-edge indicate that electron holes are largely delocalized to oxygen states. The variation in the pre-edge peak and edge position at the Fe K-edge demonstrates that the degree of electron hole transfer from the transition metal to oxygen depends sensitively on cation composition and formal Fe oxidation state. Zn and Y doped samples show the smallest energy shifts upon oxidation (i.e., even oxidized samples exhibit largely Fe3+ character). This may be related to the fact that the partial Y3+, Zn2+ substitution on the perovskite's B site increases the overall basicity of the perovskite, which allows for larger electron transfer from oxygen to iron. For oxidized samples without Y,Zn the EXAFS analysis shows very small deviation from an undistorted cubic structure. Reduction of the samples as well as partial Fe substitution by Y3+, Zn2+ strongly suppresses the third shell peak, indicating significant static disorder and buckling of B–O–B connections. These local distortions decrease the Fe–O covalency and disfavor hole transfer from iron to O. This is further confirmed by the decreased pre-peak in the O-K edge XRS spectra of Y,Zn-doped samples. The corresponding increased oxide ion basicity then leads to increased proton uptake. This consistent picture of the interplay of chemical, geometrical, and electronic structure features, and their impact on proton uptake can serve as guideline for further PCFC cathode material optimization.  D.Poetzsch et al. Phys.Chem.Chem.Phys.16,16446 (2014).  R.Zohourian et al. Adv.Funct Mater.28,1801241 (2018).  G. Raimondi et al., Chem. Mater. 32, 8502-8511 (2020).
Authors : Christian Berger (1), Judith Lammer (3), Christina Nader (2), Edith Bucher (2), Werner Grogger (3), Rotraut Merkle (1), Joachim Maier (1), Werner Sitte (2)
Affiliations : (1) Max Planck Institute for Solid State Research, Heisenbergstraße 1, DE-70569 Stuttgart, Germany (2) Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria (3) Institute of Electron Microscopy and Nanoanalysis (FELMI), Graz University of Technology & Graz Centre for Electron Microscopy (ZFE), Steyrergasse 17, A-8010 Graz, Austria
Resume : Mixed proton-, oxygen ion- and electron-conducting ceramics such as self-generated nanocomposites from the BaCeO3-δ-BaFeO3-δ system  offer attractive options for application in protonic ceramic fuel and electrolyser cells or hydrogen separation membranes. In the present work, partial substitution of Ce and Fe by Y in the BaCeO3-δ BaFeO3-δ system is investigated to further increase the proton uptake and gain a deeper understanding of the interrelation between chemical composition and oxygen-/proton-exchange processes. The precursor BaFe0.4Ce0.4Y0.2O3-δ was synthesised via a sol-gel process. After thermal treatment, a composite of a cubic (Pm-3m) Fe-rich and a trigonal (R-3c) Ce-rich perovskite was obtained. With increased annealing temperature, the fraction of the cubic phase increases (reaching 98 wt-% at 1370°C) and lattice parameters change systematically. Analytical scanning transmission electron microscopy is used to determine the distribution of both phases and their local cation stoichiometry. The water uptake measured by thermogravimetry shows characteristic differences depending on cation composition between the homogeneous BaFe0.4Ce0.4Y0.2O3-δ perovskite and 2-phase composites. These results will be related to water incorporation trends and deviations from ideally dilute defect chemistry observed for (Ba,Sr,La)FeO3-δ perovskites .  S.Cheng et al., Angew. Chem. Int. Ed. 2016, 55, 10895.  R.Zohourian et al., Adv. Funct. Mat. 2018, 28, 1801241.
|12:30||OPEN DISCUSSION SESSION|
HARVESTORE sponsored session: In situ/Operando Characterization: : TBC
Authors : R. Rodriguez-Lamas (a), C. Pirovano (b), A. Stangl (a), D. Pla (a),, R. Jónsson (a), L. Rapenne (a), E. Sarigiannidou (a), N. Nuns (b), H. Roussel (a), O. Chaix-Pluchery (a), M. Boudard (a),C. Jiménez (a), R.-N. Vannier (b), and M. Burriel* (a),
Affiliations : (a) Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France (b) Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
Resume : In recent years manganites with tailored functional properties have attracted special attention for their use in miniaturized devices such as resistive switching memories, spintronic sensors, micro solar cells and micro solid oxide fuel cells. When prepared in the form of thin films (from a few to around a hundred nanometers thick), their functional properties can largely vary in comparison to their intrinsic bulk properties. There is thus a large interest in understanding and controlling the influence of different parameters, such as epitaxy, substrate-induced strain and grain boundary effects, for the envisioned use of manganites in applied functional devices. In this work we have focused on the study of LaMnO3±δ (LMO), the parent compound of the manganese perovskites, as a promising oxygen electrode for µ-SOFCs. LMO undergoes two phase transitions upon heating and upon changes in oxygen stoichiometry, [2-4] which is of major importance for its potential functional applications. Epitaxial LMO films with different degree of strain and morphology were grown by Pulsed-Injection Metalorganic Chemical Vapor Deposition (PI-MOCVD) on two different substrates. While the LMO films grown on SrTiO3 are perfectly epitaxial and defect free, those grown on LaAlO3, with a higher film-substrate mismatch, release the strain by the formation of a high density of defects. Their oxygen exchange and diffusion properties were evaluated at the temperature range of interest (500°C- 600°C) by the Isotope Exchange Depth Profile methodology combined with Time-of-Flight Secondary Ion Mass Spectrometry. By combining the oxygen transport measurements with a detailed structural characterization using several complementary techniques, we show that the combination of defects and strain relaxation accelerates the oxygen transport across the LMO/LAO films. Additionally, we demonstrated that the oxygen diffusion at 500 °C is extraordinarily high due to the prevalence of the orthorhombic structure in the film, together with a high concentration of oxygen vacancies. These promising results open new perspectives for the use of LMO below its transition temperature for low temperature solid-state electrochemical applications in which oxygen diffusion is the key parameter determining the device performance.  D. Pla, C. Jimenez, M. Burriel, Adv. Mater. Interfaces 2017, 4, 1600974.  J. Rodríguez-Carvajal, M. Hennion, F. Moussa, A. H. Moudden, L. Pinsard and A. Revcolevschi, Phys. Rev. B, 1998, 57, R3189–R3192  J. Töpfer, J. B. Goodenough, J. Solid State Chem. 1997, 130, 117.  R. Rodriguez-Lamas, D. Pla, O. Chaix-Pluchery, B. Meunier, F. Wilhelm, A. Rogalev, L. Rapenne, X. Mescot, Q. Rafhay, H. Roussel, M. Boudard, C. Jiménez, M. Burriel, Beilstein J. Nanotechnol. 2019, 10, 389.
Authors : Catalina E. Jiménez(a), Mauricio D. Arce(a,b), Mariano Santaya(b), Emilia A. Carbonio(a,c), Raul Garcia-Diez (a), R. Gotesman (d), Horacio Troiani(b), R.G. Wilks(a), Axel Knop-Gericke(c,e), Liliana V. Mogni(b), Marcus Bär(a,f,g)
Affiliations : (a) Helmholtz-Zentrum Berlin, BESSY II, Albert-Einstein-Str.15, 12489, Berlin, Germany; (b) INN-CNEA-CONICET, Centro Atómico Bariloche, Av. Bustillo 9500, S. C. de Bariloche, Rio Negro, 8400, Argentina; (c) Fritz-Haber Institute, Dept. of Inorganic Chemistry, Faradayweg 4, 14195 Berlin, Germany; (d) Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109, Berlin, Germany; (e) MPI for Chemical Energy Conversion, Stiftstrasse 34 – 36, 45470 Mülheim an der Ruhr, Germany; (f) Friedrich Alexander Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany; (g) Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (HI ERN), Albert-Einstein.Str. 15, 12489 Berlin, Germany
Resume : Solid oxide fuel cells (SOFC) stand out among other technologies for stationary power and quality heat co-generation due to their high energy conversion efficiency that can reach 80% . SOFC generate electricity from chemical fuels such as H2, CO, CH4 at high temperatures (> 800 °C). The same device could become a solid oxide electrolyzer cell (SOEC), to generate reversely fuels from electricity. Large commercialization of this technology requires lower operation temperatures (< 600°C) to reduce costs and mitigate degradation but then typical electrode materials, i.e. electronic conductors and Ni-cermets, suffer from poisoning, C deposits, and increased activation overpotentials. Tackling these issues requires engineering new electrode materials for intermediate temperature SOFC . Ni-doped Sr(Ti,Fe)O3-d (STFN) is a mixed ionic electronic-conducting perovskite that exsolves Fe Ni nanoparticles (NPs) in a reducing atmosphere. These Fe-Ni NPs boost the performance of the supporting STFN electrodes but the underlying mechanisms at the solid/gas interface are not well understood [3-5]. In this study, we combine ambient pressure X-ray photoelectron and absorption spectroscopies with electrochemical impedance spectroscopy and polarization in SOFC and SOEC modes on model cells while redox cycling the atmosphere. We characterize the surface chemistry of STFN electrodes under operando conditions to investigate the tunability of the exsolution process, which could impact the life cycle.  “Technology Report Hydrogen and fuel cells”, International Energy Agency, Springer, 2015.  “A perspective on low-temperature solid oxide fuel cells”, Z. Gao, L.V. Mogni, E.C. Miller, J.G. Railsback, S.A. Barnett, Energy and Environmental Science, 9 (2016) 1602-1644.  “Ni-Substituted Sr(Ti,Fe)O3 SOFC Anodes: Achieving High Performance via Metal Alloy Nanoparticle Exsolution”, T. Zhu, H. Troiani, L.V. Mogni, M. Han, S.A. Barnett, Joule, 2 (2018) 478-496.  “Exsolution and chemistry in perovskite SOFC anodes Role of Stoichiometry in Sr(Ti,Fe,Ni)O3”, T. Zhu, H. Troiani, L.V. Mogni, M. Santaya, M. Han, S.A. Barnett, Journal of Power Sources, 439 (2019) 227077.  “Study of phase stability of SrTi0.3Fe0.7O3−d perovskite in reducing atmosphere: Effect of microstructure”, Solid State Ionics, 342(2019) 3-9.
Authors : Yunqing Tang(a)*, Francesco Chiabrera(a), Alex Morata(a), Iñigo Garbayo(b), Nerea Alayo(a), Albert Tarancón(a,c)
Affiliations : (a) Department of Advanced Materials for Energy Applications, Catalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1, 08930 Sant Adrià del Besòs, Barcelona, Spain; (b) Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein 48, 01510 Vitoria-Gasteiz, Spain; (c) ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain; *firstname.lastname@example.org
Resume : Mixed ionic and electronic conductor (MIECs) thin films offer an ideal platform for the study of oxygen mass transport mechanisms, which play a crucial role in many energy and information technologies, such as solid oxide fuel cells (SOFCs) and non-volatile resistive memory devices. For these applications, the defect chemistry is known to play a major role in determining the overall performances and the knowledge of the point defect concentration is needed to tailor the oxides’ functional properties. Nevertheless, traditional methods used in bulk materials presents many challenges in thin films’ form, especially at low temperature, since the small masses and volumes lower the sensitivity of the measurements. The objective of present work is to investigate the defect chemistry in La1-xSrxFeO3-δ (LSF) thin films as a function of equivalent oxygen partial pressure, temperature (450-350 ºC) and Sr concentration by in-situ ellipsometry measurements. LSF thin films were deposited on YSZ (001) substrate by Pulsed Laser Deposition (PLD). The oxygen chemical potential of the LSF was progressively varied by applying a voltage bias between the thin film and the counter-back electrode, while recording the ellipsometry spectra. The results show that it is possible to quantify the defect concentration in the LSF thin films at intermediate-to-low temperatures using ellipsometry, this method offers new insights into the effect of the point defect concentration on the material’s electronic structure and on the phenomena involved in the reduction and oxidation of LSF thin films.
Authors : Zijie Sha, Eleonora Cali, Zonghao Shen, Ecaterina Ware, Gwilherm Kerherve, and Stephen J. Skinner
Affiliations : Department of Materials, Imperial College London.
Resume : Mixed ionic and electronic conducting (MIEC) perovskites are often used as electrodes in high temperature electrochemical devices such as solid oxide fuel/electrolysis cells (SOFC/SOEC) and oxygen transport membranes (OTMs) due to their excellent catalytic activity for oxygen reduction and ionic and electronic conductivity. Previous studies on the use of MIEC perovskites for these applications have focussed on material behaviour and properties under pure oxygen conditions. Recently, however, it has been suggested that humid vapour may modify the materials’ chemistry under device operating conditions and impact device performance and durability [1-2]. Study of water-induced oxygen transport mechanisms on MIEC perovskites under different humid atmospheres is vital as the aforementioned electrochemical devices approach market viability. In this study, the oxygen surface exchange and bulk diffusion kinetics of MIEC perovskite (La0.8Sr0.2)0.95Cr0.5Fe0.5O3-δ (LSCrF8255) are probed through Isotopic Exchange Depth Profiling – Secondary Ion Mass Spectrometry (IEDP-SIMS). Isotopic exchange annealing was carried out from 600 to 900 °C under pure water (pO2 < 1 mbar, pH2O = 30 mbar), humidified oxygen (pO2 = 200 mbar, pH2O = 30 mbar), and dry oxygen (pO2 = 200 mbar, pH2O = 0 mbar) conditions. We have observed a significant enhancement in oxygen mass transport properties under the pure water vapour condition compared to the dry and the wet oxygen conditions with high pO2. This is primarily due to the higher concentration of oxygen vacancies generated in the materials during exchange annealing. To probe the defect chemistry of the samples, in particular the oxygen non-stoichiometry changes under the different annealing conditions, thermogravimetric analysis and neutron diffraction were used. Our study also demonstrates limited surface exchange between water and the LSCrF phase under the humidified oxygen conditions. This is primarily due to the dominance of homo-exchange between the humid vapour and gaseous oxygen molecules at high temperatures, as observed through in-situ residual gas analysis carried out during wet oxygen isotopic exchange. In addition to the study of transport properties, we have investigated the effect of the atmosphere on the stability of the LSCrF8255 surface using angle-resolved X-ray photoelectron spectroscopy, scanning electron microscopy, and scanning transmission electron microscopy, correlating changes in oxygen transport kinetics with cation segregation processes to provide a detailed understanding of potential degradation processes in the solid oxide cell or OTM devices under humid conditions. 1. Sha, Z., Cali, E., Kerherve, G. and Skinner, S.J., 2020. Oxygen diffusion behaviour of A-site deficient (La0.8Sr0.2)0.95Cr0.5Fe 0.5O3−δ perovskites in humid conditions. Journal of Materials Chemistry A, 8(40), pp.21273-21288. 2. Staykov, A., Fukumori, S., Yoshizawa, K., Sato, K., Ishihara, T. and Kilner, J., 2018. Interaction of SrO-terminated SrTiO3 surface with oxygen, carbon dioxide, and water. Journal of Materials Chemistry A, 6(45), pp.22662-22672.
Authors : Mogni, L.V. *(1), Santaya, M. (1), Toscani L. (1), Troiani, H.E. (1), Basbus, J.F. (1), Arce M.D. (1,2) Baque L. C. (1) Serquis, A.C. (1) Napolitano, F. R. (1), Ascolani-Yael J. (1), Cuello S. (1), Gamba N. (1), Bär, M. (2), Cuello G.(3), Fernández-Díaz M.T. (3), Alonso J.A. (4), Emilia A. Carbonio (5,6) y a Axel Knop-Gericke(6,7) Jimenez, C.E. (2)
Affiliations : (1)Instituto de Nanociencia y Nanotecnologia CNEA-CONICET, Bariloche, Argentina (2) Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Department Interface Design, Berlin, Germany. (3) Institute Laue Lagevin, Grenoble, France (4) Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Spain (5) Helmholtz-Zentrum Berlin, Research Group Catalysis for Energy, BESSY II, Albert-Einstein-Str.15, 12489, Berlin, Germany (6) Fritz-Haber Institute, Dept. of Inorganic Chemistry, Faradayweg 4, 14195 Berlin, Germany (7) MPI for Chemical Energy Conversion, Stiftstrasse 34 – 36, 45470 Mülheim an der RuhrMülheim an der Ruhr, Germany * lead presenter
Resume : The comprehension of the complex processes taking place at Solid Oxide Fuel Cells (SOFC) materials requires using complementary characterization techniques. In these devices, the ionic/electronic charge transport and the solid-gas electrode reactions depend on the atomic and electronic structures of the electrode surface and electrode/electrolyte's bulk. However, SOFC works at non-ambient conditions, which could induce changes in material structures affecting their performances. Therefore, simultaneous electrical or electrochemical experiments with in-situ studies using neutron or synchrotron radiation techniques are essential to understand the whole phenomena. In this work, we discuss results for both, proton conductor electrolyte and perovskite-based symmetrical electrode materials. In oxides with proton conductivity, O-ion and/or electronic conduction usually co-exist. Thus, in-situ X-ray diffraction combined with Impedance Spectroscopy (IS) and neutron-based techniques were used to elucidate the crystalline structure and validate the temperature range where BaCe0.4Zr0.4Y0.2O3-δ can operate as proton electrolyte. On the other hand, we evaluate the chance of using Ni-doped SrTi0.3Fe0.7O3-d perovskite as anode/cathode by studying the reversibility of reduction-oxidation cycles with the aim to explore electrode regeneration process. We used near ambient synchrotron spectroscopies, electron microscopy and IS aiming to understand the mechanism of surface decoration by nanoparticles exsolution and how it affects the electrode reactions.
Authors : Emily Skiba, Haley B. Buckner, Ting Chen, Qing Ma, Nicola H. Perry
Affiliations : Department of Materials Science & Engineering, University of Illinois at Urbana-Champaign; Kyushu University; Argonne National Laboratory
Resume : Mixed conductors find application in sensors, fuel/electrolysis cell electrodes, reactors for chemical fuel production, and gas separation membranes. In some cases, low-to-intermediate temperature processing and operation may be advantageous for limiting initial energy expenditure and long-term degradation, respectively. In such conditions, amorphous or poorly crystalline structures may prevail, though their performance has not been widely studied. Therefore, in recent work, we have been applying X-ray absorption spectroscopy and in situ impedance and optical measurements during crystallization, in order to explore how mixed conductor structure-property relationships are impacted by the degree of crystallinity. Our initial studies on thin films of the perovskite SrTi0.65Fe0.35O3-x (STF) demonstrate that the amorphous material, prepared by pulsed laser deposition at room temperature, contains relatively under-coordinated cations with a lower average oxidation state for Fe than in the crystalline counterpart, prepared via higher temperature deposition or annealing. These results are consistent with an observed increase in sub-gap optical absorption and electrical conductivity during crystallization, which is attributed to an increase in hole concentration. These local structural and defect chemical changes can help to explain the evolution of other functional properties of STF during crystallization, such as the dramatic increase in oxygen exchange kinetics.
|15:45||OPEN DISCUSSION SESSION|
Solid State Energy Devices (IV): Batteries : Ainara Aguadero
Authors : Jeff Sakamoto1,2,3, Michael Wang2, Marie-Claude Bay4, Michael Wang2, and Corsin Battaglia4
Affiliations : 1 Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA 2Department of Material Science and Engineering, University of Michigan, Ann Arbor, MI, USA 3 Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA 4Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
Resume : There is tremendous interest in making the next super battery, but state-of-the-art Li-ion technology works well and has inertia in several commercial markets. Supplanting Li-ion will be difficult. Recent material breakthroughs in Li and Na metal solid-state electrolytes could enable a new class of non-combustible solid-state batteries (SSB) delivering twice the energy density (1,200 Wh/L) compared to Li-ion. However, technological and manufacturing challenges remain. The discussion will consist of recent milestones and attempts to bridge knowledge gaps to include: • The physical and mechano-electrochemical phenomena that affect the stability and kinetics of the Li and Na metal-solid electrolyte interface • Thin film processing and Li integration with LLZO • Plating and stripping dynamics of Li and Na metal Despite the challenges, SSB technology is rapidly progressing. Multi-disciplinary research in the fields of materials science, solid-state electrochemistry, and solid-state mechanics will play an important role in determining if SSB will make the lab-to-market transition. Key words: energy storage, Li, Na
Authors : Lisette Haarmann, Karsten Albe
Affiliations : Technische Universität Darmstadt, Otto-Berndt-Str. 3, 64287 Darmstadt
Resume : The use of metallic lithium as anode material is crucial for achieving maximal energy densities in all solid state Li ion batteries (ASSLIB). Therefore, understanding the nature of ion transfer at the interface between the lithium metal and solid electrolyte is essential for further optimization of ASSLIB. In this contribution, the lithium transfer across the SE | lithium metal interface is investigated by means of ab-initio calculations based on density functional theory (DFT). The aluminum doped garnet Li6.25Al0.25La3Zr2O12 (LLZO) is considered as a model SE due to its practical stability against lithium metal. By combining the information of both ab-initio molecular dynamics (AIMD) simulations and calculations of energy barriers using the Nudged Elastic Band (NEB) method, a schematic energy landscape of the LLZO | lithium metal interface is constructed, implying that the charge transfer process across this interface is not the rate limiting step, neither during stripping, nor during plating conditions. This charge transfer reaction is additionally analyzed by tracking the transformation of the charge density profile during the interfacial jump. We observe, that the ionization of lithium atoms occurs after the energy barrier has been overcome. This confirms that the transfer of the electron from the ionized lithium to the delocalized metallic electron cloud does not impose any intrinsic energy barrier to the interfacial transport.
Authors : Edouard Quérel, Qianli Ma, Andrea Cavallaro, Ieuan Seymour, Frank Tietz, Ainara Aguadero
Affiliations : Department of Materials, Imperial College London; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, Materials Synthesis and Processing (IEK-1); Department of Materials, Imperial College London; Department of Materials, Imperial College London; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, Materials Synthesis and Processing (IEK-1); Department of Materials, Imperial College London
Resume : Na metal All-Solid-State batteries (ASSBs) could provide a single solution to simultaneously meet several notorious objectives for new generations of cells: outstanding safety, high energy density, fast charging rates and reduced environmental impact. Among the best Na+ conducting ceramic solid electrolytes, the family of Na+ SuperIonic CONductors (NaSICON) of composition Na1+xZr2SixP3-xO12 (0 ? x ? 3) has long been recognized for its remarkably high ionic conductivity. Thanks to perpetuated research over several decades, the ionic conductivity of NaSICON ceramics was improved and now reaches values of up to 5.0 mS cm-1 at room temperature for the composition Na3.4Zr2Si2.4P0.6O12 . Interfaces in NaSICON-based ASSBs ? and in particular the Na metal|NaSICON interface - have however yet to be optimized. In this work, the experimental conditions influencing the Na|NaSICON interface resistance are assessed. The impact of various polishing and annealing conditions on the surface composition of NaSICON ceramics are studied by a combination of X-Ray Photoelectron Spectroscopy (XPS) and Low Energy Ion Scattering (LEIS) and correlations with the electrochemical performance of Na|NaSICON interfaces are established. This study reveals the existence of an in-situ formed sodium phosphate film on the surface of thermally treated NaSICON ceramics and demonstrates that its presence systematically leads to Na|NaSICON interface resistances below 1 ? cm2 at room temperature. DFT simulations demonstrated that the segregation of this sodium phosphate layer on the surface of NaSICON ceramics was driven by a minimization of surface energies. NaSICON ceramics possessing this surface film were able to withstand high current densities of up to 8 mA.cm-2 which paves the way for fast-charging Na metal ASSBs. References  Ma, Qianli, et al. "Room temperature demonstration of a sodium superionic conductor with grain conductivity in excess of 0.01 S cm? 1 and its primary applications in symmetric battery cells." Journal of Materials Chemistry A 7.13 (2019): 7766-7776.
Authors : Katharina Hogrefe*, Bernhard Gadermaier and H. Martin R. Wilkening * presenting and contact author (email@example.com)
Affiliations : Institute of Chemistry and Technology of Materials, Graz University of Technology (NAWI Graz), Stremayrgasse 9, A-8010, Austria
Resume : Na3PS4 is a promising electrolyte for future sodium all-solid state batteries. Its readily available components make it a compelling and more sustainable alternative to recent Li-technologies. At ambient temperature, the ionic conductivity in its cubic crystal structure is in the order of 10−4 cm−1 . Even though several studies focused on explaining the dynamic properties of cubic Na3PS4, the driving forces that lead to fast Na+ exchange are not yet completely clear. Here, we synthesized nanocrystalline, defect-rich cubic Na3PS4 via a solid-state synthesis with subsequent annealing at 250 °C for 12 h. Additionally, we synthesized doped Na3PS4 to investigate the influence of foreign atoms in the crystal structure on the ionic transport properties. Ion dynamics of the powder samples were analysed using high-precision broadband impedance spectroscopy and variable-temperature, time-domain 23Na NMR spin-lattice relaxation rate measurements. We were able to separate bulk ion dynamics from electrical relaxation associated with grain boundary regions. While macroscopic transport is characterized by an activation energy of 0.36 eV, 23Na NMR indicates a much lower value of 0.18 eV, see also . This discrepancy points to length-scale dependent dynamic parameters. Indeed, electric modulus spectroscopy, i.e., the analysis of resistivity peaks ρν (= M''/ω)(1/T), revealed a low-temperature activation energy of 0.13 eV, which is consistent with our result from NMR. We attribute this barrier to extremely fast local Na hopping processes constituting the basis for long-range ionic transport in Na3PS4.  A. Hayashi et al., Nat. Commun., vol. 3, pp. 856-860, 2012.  C. Yu et al., J. Mater. Chem. A, vol. 4, pp. 15095-15105, 2016.
|17:30||OPEN DISCUSSION SESSION|
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Defects & Transport Phenomena (I): Modelling : TBC
Authors : Andreas Klein
Affiliations : Technical University of Darmstadt, Institute of Materials Science, Electronic Structure of Materials, Otto-Berndt-Str. 3, 64287 Darmstadt, Germany
Resume : Different charge compensation mechanisms are known for ionic solids. Among them are the formation of compensating defects such as electronic or ionic defects, the valence changes of atoms and the segregation of dopants. In principle, the introduction of positive charges by donor doping or reduction results either in the compensation by electrons, negatively charged intrinsic acceptors as metal vacancies, the reduction of one of the species in the compound, or in the segregation of the dopant species. The situation is reversed for the addition of negative charges. While the different mechanisms are well-documented for different materials, predicting the prevailing compensation mechanism in a material is hardly possible. It is a common perception that the Fermi energy is determined by the defect concentrations. However, it is also possible to describe the concentration of defects as a function of the Fermi energy. This reveals Brouwer diagrams, which are identical to those obtained using standard defect chemistry calculations. In addition, it enables a direct comparison of the different compensation mechanisms.
Authors : Kia Chai PHUAH, Ruoyu DAI, Chang Jie LEONG, Stefan ADAMS
Affiliations : Department of Materials Science and Engineering - National University of Singapore
Resume : The bond-valence method is a simple robust method originally developed to validate crystal structures. By comparing valence sums based on geometric distances between atoms in a crystal structure, apparently stable configurations can be identified and provide a dependable prediction for the stability of a structure. In our augmented energy-scaled “softBV” form the method is applied to solid-state ionic conductors to identify promising candidate structures with high ion mobility. Bond-valence site energy landscapes are generated by scanning probe ions throughout the structure. Probable ion transport pathways and their approximate migration barriers are rapidly visualized for prototype structures. The speed and simplicity of this approach enables screening of structure databases to identify next-generation solid electrolytes. We further extend the bond-valence site energy method by automatizing ion pathway analysis for high-throughput screening without human intervention in the freely available softBV-GUI software. Predictions of suitable dopants and of absolute conductivities guide the optimization of transport properties in candidate structures. Large numbers of structural modifications can be rapidly computed exploiting the speed of the approach, which in conjunction with big data techniques helps to improve the quantification and robustness of the predictions. Examples of experimental verifications of identified and optimized ion-conducting solids will be demonstrated.
Authors : Denis Gryaznov(a), Rotraut Merkle(b), Maximilian F. Hoedl(b), Eugene A. Kotomin(a,b), Joachim Maier(b)
Affiliations : (a) Institute of Solid State Physics, University of Latvia, 8 Kengaraga, LV-1063, Riga, Latvia (b) Max Planck Institute for Solid State Research, Heisenbergstr. 1, D-70569, Stuttgart, Germany
Resume : Protonic ceramic fuel cells (PCFC) attract growing interest, since BaZr(1-x)Y(x)O(3-x/2) electrolytes offer a higher ionic conductivity compared to oxide ion conductors < 600°C. Optimized cathode materials with mixed protonic and electronic conductivity (e.g. (La,Ba,Sr)(Co,Fe,Zn,Y)O3-delta ) are crucial for PCFC performance. However, they generally show lower degrees of hydration compared to BaZr(1-x)Y(x)O(3-x/2). We perform DFT calculations based on the Hubbard-type (PBE+U and SCAN+U) functionals for Ba(1-x)Sr(x)FeO3-delta , BaCoO3-delta and SrCoO3-delta in order to look deeper in the materials properties changes induced by oxygen vacancies and protons. We, therefore, present a detailed analysis of the electronic DOS, volume and local geometry changes, oxidation and hydration energies as a function of oxygen deficiency (nominal Fe and Co oxidation state, hole concentration). An important comparison with La(1-x)Sr(x)FeO3-delta  on the role of A-cation is also given. The hydration energy is more negative for Ba(1-x)SrxFeO3-delta than for La(1-x)Sr(x)FeO3-delta, which can be assigned to the larger oxide ion basicity. The hydration energy becomes less negative with increasing hole concentration, which is related to hole delocalization to the oxide ions. Thus, we achieve a comprehensive understanding of water incorporation in mixed protonic-electronic conductors.  R. Zohourian, R. Merkle, G. Raimondi, J. Maier, Adv. Funct. Mater. 28 (2018), 1801241  M. Hoedl, D. Gryaznov, R. Merkle, E. A. Kotomin, J. Maier, J. Phys. Chem. C 124 (2020), 11780  D. Gryaznov, R. Merkle, E. A. Kotomin, J. Maier, J. Mater. Chem. A 4 (2016), 13093
Authors : BP Uberuaga, CR Kreller, MT Janish, JA Valdez, R Perriot, G Pilania, YQ Wang
Affiliations : Los Alamos National Laboratory
Resume : It is becoming ever more apparent that, in complex compounds such as pyrochlores, the detailed arrangement of the cations drives functionality. For example, both radiation tolerance and ionic conductivity have been linked to how easily cations can mix across sublattices. This is due to the fact that mass transport in these materials is a strong function of the cation distributions. However, the actual relationship between the cation, or chemical, structure of these compounds and the rates of transport are still not well established. While some reports find enhanced ionic conductivity in disordered materials, others find higher conductivity in ordered phases. Many of these studies use chemistry to influence the disorder, essentially changing multiple variables at once. However, the degree to which cations mix can be finely controlled using radiation damage without changing chemistry. Here, we use radiation damage as a tool to induce changes in the cation structure of thin-film model pyrochlores. We then characterize the extent to which those changes impact mass transport. We combine these experimental efforts with state-of-the-art simulation methodologies to understand how atomic scale mechanisms dictating mass transport change when the cation structure is modified. We have found that even small changes in cation structure can lead to large changes in the transport characteristics of the material. Our results provide new insight into mass transport in materials that exhibit chemical complexity well beyond the model systems studied where chemical disorder dictates the fundamental behavior of the material.
|11:00||OPEN DISCUSSION SESSION|
Solid State Energy Devices (I): Solid Oxide Cells : TBC
Authors : R. Merkle,1 M. F. Hoedl,1 G. Raimondi,1 E. A. Kotomin,1,2 J. Maier,1
Affiliations : 1 Max Planck Institute for Solid State Research, Stuttgart, Germany 2 Institute of Solid State Physics, University of Latvia, Riga, Latvia
Resume : Cathode materials for protonic ceramic fuel cells (PCFC) require sufficient proton conductivity to extend the reaction zone beyond the three phase boundary. The hydration thermodynamics of BaFeO3-d-related perovskites was studied by thermogravimetry.  Despite a high oxygen vacancy concentration, the degree of hydration is lower for cathode materials compared to Ba(Zr,Y)O3-x electrolytes. A partial substitution of iron by redox-inactive, oversized Zn2+ or Y3+ drastically increases the proton uptake. Measurements of oxygen nonstoichiometry and proton uptake indicate pronounced deviations from ideally dilute defect chemistry (hole-hole and hole-proton defect interactions ). Based on DFT calculations  and EXAFS/XRS measurements , these interactions are related to the partial transfer of holes from iron to adjacent oxygen ions, which in turn disfavors protonation. The obtained detailed defect-chemical understanding serves as the basis for PCFC cathode optimization, in particular since proton uptake, catalytic activity, electronic conductivity, and stability show conflicting trends.  R. Zohourian, R. Merkle, G. Raimondi, J. Maier, Adv. Funct. Mater. 28, 1801241 (2018)  M. F. Hoedl, D. Gryaznov, R. Merkle, E. A. Kotomin, J. Maier, J. Phys. Chem. C 124, 11780 (2020)  G. Raimondi, A. Chiara, F. Giannici, R. Merkle, J. Maier, Chem. Mater. 32, 8502 (2020) We thank GIF (I-1342-302.5/2016) for financial support
Authors : Ragnar Strandbakke (1), Sebastian Lech Wachowski (3), Maria Balaguer (4), Alfonso Carrillo (4), Iga Szpunar (3), Aleksandra Mielewczyk-Gryń (3), Håkon Andersen (1), Visa Aleksi Mäntysalo (1), Vegar Øygarden (2), Einar Vøllestad (2), Sarmad W. Saeed (1), Truls Norby (1)
Affiliations : 1 Department of Chemistry, Centre for Materials Science and Nanotechnology, University of Oslo, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway 2 SINTEF Industry, Department of Sustainable Energy Technology, Forskningsveien 1, 0373, Oslo, Norway Department for Neutron Materials Characterization, Institute for Energy Technology, Kjeller, Norway 3 Faculty of Applied Physics and Mathematics, and Advanced Materials Centre Gdańsk University of Technology, Gdańsk, Poland 4 Instituto de Tecnología Química (Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas), Av. Naranjos s/n, E-46022, Valencia, Spain
Resume : Mixed Proton and Electron conducting Ceramics (MPEC’s) are central in the development of efficient positrode electrodes for Proton Ceramic Electrochemical Cells (PCEC’s). As for most high temperature oxygen electrodes, the mass transfer overpotential is limiting the electrode performance, and the interplay between catalytic activity for the surface red-ox reaction and the inherent partial proton conductivity determines the electroactive surface area during operation. Furthermore, the electronic conductivity of the electrode is important for good current collection and low ohmic overpotential, but mobile electronic defects also affects proton stability. The stability of proton defects in a ceramic structure strongly correlates with anion basicity. It has previously been shown that the basicity of the oxide ions is governed by the cation-anion charge transfer characteristics, and electron structure and mobility is therefore essential with respect to both red-ox activity and partial proton conductivity. In a perovskite structure, the B-site cation facilitates electron transfer and the A-site cation influences the structure and overall electronegativity. In this work, we investigate the influence of A- and B-site substitutions on proton concentration and electrochemical performance in Ba- and La-based cobaltites with perovskite- or perovskite-related structures. Thermogravimetric Analysis (TGA) has been used to investigate proton concentrations, and Electrochemical Impedance Spectroscopy (EIS) was used to investigate polarisation resistance of the positrode reactions for model electrodes and porous electrodes. In order to investigate the positrode in both anodic and cathodic operation, the EIS studies has been performed under positive and negative DC bias, and the results reveal that B-site substitutions affect water oxidation and oxygen reduction differently. Substituting Ti4+ for Co3+ in a BaLa0.8Gd0.2Co2O6-δ electrode promotes the anodic water oxidation reaction, while substituting Zn2+ for Co3+ impedes the anodic reaction and promotes the cathodic reduction of oxygen. Polarization resistances of several electrode compositions are obtained, and pO2, pH2O and T-dependencies are analysed for electrode materials with different hydration levels. The influence of B-site cation substitution on hydration is also shown for the BaLaCoO3-BaLaFeO3 system. Acknowledgements: The Research Council of Norway (Grant nᵒ 272797 “GoPHy MiCO” and nᵒ 299736 “FunKey Cat”)  T.S. Bjørheim, M.F. Hoedl, R. Merkle, E.A. Kotomin, J. Maier, The Journal of Physical Chemistry C 124 (2020) (2) 1277.  M.F. Hoedl, D. Gryaznov, R. Merkle, E.A. Kotomin, J. Maier, The Journal of Physical Chemistry C 124 (2020) (22) 11780.
Authors : Nicholas J. Williams, Ieuan D. Seymour and Stephen J. Skinner
Affiliations : Department of Materials Science and Engineering, Imperial College London
Resume : The local activation overpotential describes the electrostatic potential shift away from equilibrium at an electrode/electrolyte interface. This electrostatic potential is not entirely satisfactory for describing the reaction kinetics of a mixed ionic-electronic conducting (MIEC) solid-oxide cell (SOC) electrode where charge transfer occurs at the electrode-gas interface. Using the theory of the electrostatic potential at the MIEC-gas interface as an electrochemical driving force, charge transfer at the ceria-gas interface has been modelled based on the intrinsic dipole potential of adsorbate.1 This model gives a physically meaningful reason for the enhancement in electrochemical activity of a MIEC electrode as the steam pressure is increased in both fuel cell and electrolysis modes. We validated this model against operando XPS data to accurately predict the outer work function shift of thin film Sm¬0.2Ce0.8O1.9 in a H2/H2O atmosphere as a function of overpotential.2 1 J. Fleig, Phys. Chem. Chem. Phys., 2005, 7, 2027–2037. 2 Z. A. Feng, C. Balaji Gopal, X. Ye, Z. Guan, B. Jeong, E. Crumlin and W. C. Chueh, Chem. Mater., 2016, 28, 6233–6242.
|12:30||OPEN DISCUSSION SESSION|
Interface & Surface Phenomena (III) : TBC
Authors : David S. Mebane
Affiliations : Department of Mechanical and Aerospace Engineering, West Virginia University
Resume : This presentation will survey the continuing controversy surrounding the modeling of surfaces and interfaces in ionic conductors, and will move beyond it to a discussion of the feasibility of device-scale models incorporating microscopically accurate, nanoscale depictions of solid state electrochemical interfaces. Microscopic evidence makes it clear that dilute-solution theories cannot be trusted in concentrated ionic solutions, where 'concentrated' refers to anything greater than approximately one mole percent. The results of a quantitative analysis of a microscopic dataset and corresponding statistical comparison of dilute-case theories vs. those incorporating concentrated solution thermodynamics will be presented. Devices based on ionic materials -- such as high temperature fuel cells and electrolyzers -- require accurate models of interfaces that control ionic conductivity and where rate-limiting reactions take place. Device-scale models of ceria-based electrolyzers for carbon dioxide with nanoscale interface models are now in development at West Virginia and the latest results will be presented.
Authors : David Diercks 1, Federico Baiutti 2, Francesco Chiabrera 2, Alex Morata 2, Albert Tarancon 2,3
Affiliations : 1. Department of Metallurgical and Materials Engineering, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401, USA; 2. Catalonia Institute for Energy Research (IREC), Jardins de Les Dones de Negre 1, 08930 Sant Adrià del Besòs, Barcelona, Spain; 3. ICREA, 23 Passeig Lluís Companys, Barcelona 08010, Spain.
Resume : Solid oxide cells which convert chemical energy to electrical energy offer an opportunity toward the deployment of miniaturized energy generation systems for battery-free portable devices (1, 2). In particular, mixed ionic-electronic conducting oxide (MIEC)-based ceramic layers, which combine electronic and ionic conductivity, exhibit a promising combination of catalytic and transport behavior (3). In recent times, engineering the electrochemical properties of MIEC materials at the grain boundary level has shown great potential (4, 5). In order to improve upon the design of such materials, a better understanding of the nanoscale structure and especially the direct analysis of the grain boundary behavior is therefore key. Atom probe tomography (APT) has the unique ability to probe the nanoscale 3-D distribution of species down to tens of parts-per-million concentrations. This has provided fundamental insights into the compositions and composition profiles in and around precipitates, grain boundaries, phase boundaries, and dislocations in metal alloys, electronic materials, and ceramic materials (6). Additionally, since this time-of-flight technique has sufficient mass resolution to detect particular isotopes of species, the introduction of tracer isotopic species can be used to distinguish sources of an element. For example, this technique has been used to investigate hydrogen embrittlement of steels using a deuterium tracer (7). Here, annealing of lanthanum manganite and chromite films at controlled temperatures and times was carried out in an atmosphere containing an 18O isotopic tracer followed by APT analysis of these films. From the measured distribution of the 18O species, the diffusion of reactant oxygen is distinguished from that in the original oxide film structures allowing fundamental investigations on oxygen kinetics on the nanoscale. The experimental results display the local distributions of 18O and other species in and around the grain boundaries and phase boundaries in the MIEC films allowing for direct comparisons with simulation profiles. This work presents a novel powerful tool for the fundamental understanding of grain boundary electrochemical properties in MIEC materials. 1. E. D. Wachsman, K. T. Lee, Lowering the Temperature of Solid Oxide Fuel Cells. Science 334, 935-939 (2011). 2. S. S. Shin et al., Multiscale structured low-temperature solid oxide fuel cells with 13 W power at 500 °C. Energy & Environmental Science 13, 3459-3468 (2020). 3. Z. Gao, L. V. Mogni, E. C. Miller, J. G. Railsback, S. A. Barnett, A perspective on low-temperature solid oxide fuel cells. Energy & Environmental Science 9, 1602-1644 (2016). 4. E. Navickas et al., Fast oxygen exchange and diffusion kinetics of grain boundaries in Sr-doped LaMnO3 thin films. Physical Chemistry Chemical Physics 17, 7659-7669 (2015). 5. F. Chiabrera et al., Engineering Transport in Manganites by Tuning Local Nonstoichiometry in Grain Boundaries. Advanced Materials 31, 1805360 (2019). 6. A. Devaraj et al., Three-dimensional nanoscale characterisation of materials by atom probe tomography. International Materials Reviews, 1-34 (2017). 7. Y. S. Chen et al., Direct observation of individual hydrogen atoms at trapping sites in a ferritic steel. Science 355, 1196 (2017).
Authors : Alexander K. Opitz (1), Andreas Nenning (1), Manuel Holzmann (1), Cornelia Bischof (2), Matthias Gerstl (1), Jürgen Fleig (1), Martin Bram (2)
Affiliations : (1) TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; (2) Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-1), 52425 Jülich, Germany
Resume : Nickel/gadolinia-doped ceria (Ni/GDC) is the currently most promising alternative fuel electrode material for solid oxide fuel and electrolysis cells. For a targeted optimisation of real porous Ni/GDC cermet electrodes, a detailed insight into the role of the material properties for the electrochemical polarisation resistance is crucial. Here, model-composite GDC thin film electrodes with embedded current collectors were used in the first step to characterize the electrochemical elementary parameters of this material. In the second step, the results from model experiments are transferred to the interpretation of the impedance of porous cermet electrodes. Analytic fits of the electrode impedance are done by using a transmission line circuit, which reflects the physically correct relationship of the relevant elementary processes on Ni/GDC cermet electrodes. With this approach, it is possible to separate and quantify the individual contributions to the electrode polarisation resistance, such as oxygen ion transport across the electrolyte/GDC interface, ionic conductivity within the porous Ni/GDC electrode, and oxygen exchange at the GDC surface. Comparison with our model studies yields very good quantitative agreement. With these detailed insights, we can explain the excellent performance of real porous Ni/GDC fuel electrodes, which is enabled by the mixed ion/electron conduction of GDC and a microstructure with small GDC and large Ni grains. Moreover, we show that anode functional layers consisting entirely of GDC can even surpass the performance of cermet anodes (at 800 °C an ASR of 0.012 Ωcm² can be achieved), if the functional layer is sufficiently thin and good contact to a current collecting layer is established.
Authors : Edith Bucher (1), Christian Berger (1), Judith Lammer (2), Christina Nader (1), Werner Sitte (1)
Affiliations : (1) Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria; (2) Institute of Electron Microscopy and Nanoanalysis (FELMI), Graz University of Technology & Graz Centre for Electron Microscopy (ZFE), Steyrergasse 17, A-8010 Graz, Austria
Resume : Perovskites from the La1-xSrxCo1-yFeyO3-δ series are promising materials for solid oxide cell air electrodes. However, Sr-segregation and reaction with acidic impurities lead to significant long-term degradation. Thus, research efforts are directed towards the development of alternative materials with a weak driving force for cation-segregation, low basicity, and excellent mass- and charge transport properties. Recently, promising results were obtained for La0.8Ca0.2FeO3-δ, which shows fast oxygen exchange kinetics and good long-term stability. In the present study, we explore the effects of Nd-substitution on structure-property relations in the La0.8-xNdxCa0.2FeO3-δ series in order to further optimize the mass- and charge transport properties and long-term stability. Single-phase orthorhombic perovskites (space group Pnma) were obtained in the range 0≤x≤0.6. Atomically resolved STEM-EDX maps confirm that La, Nd, and Ca are distributed homogeneously on the A-site. As expected from considerations of the ionic radii, increasing Nd-substitution leads to a decrease in unit cell volume. The orthorhombic/trigonal phase transition, which is observed for x=0 at approx. 750°C, is suppressed for x≥0.1. A maximum in the electronic conductivity was observed for x=0.1-0.2, whereas the thermal expansion coefficient and the oxygen nonstoichiometry are nearly independent of x at 0.1≤x≤0.6. First results on the oxygen exchange kinetics of LNCF (x=0.6) show high activity towards oxygen reduction.
Authors : Wolfgang Preis
Affiliations : Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben, Austria
Resume : The performance of mixed conducting oxides, such as cathode materials for solid oxide fuel cells, is strongly correlated with oxygen exchange processes between the gas phase and the ceramic oxide which can be described by oxygen diffusion as well as the surface exchange reaction. The long-term stability of cathode materials is highly affected by the occurrence of inert surface particles blocking the surface exchange reaction. Amongst others, conductivity relaxation experiments are a powerful tool for the investigation of the oxygen exchange properties. It is the aim of this contribution to present finite element modeling (FEM) of relaxation curves for ceramic samples as a function of surface coverage of inert particles. In particular, the effect of the particle shape as well as size distribution is studied in detail. Basically, the FEM simulations have been carried out on thick (0.05 cm) as well as thin samples (0.5 – 5 µm). A bimodal distribution of the surface particles is accomplished by a combination of large particles (100 µm) with significantly smaller particles (1 – 17 µm). In addition, large particles (100 µm) combined with particles of comparable size (20 – 40 µm) have been investigated. Moreover, the effect of surface particles with a square shaped cross-section as well as a rectangular cross section has been taken into account. Interestingly, the oxygen exchange kinetics is affected by flux constriction especially in the case of fairly large particle sizes.
Authors : Filip Podjaski (1 2), Daniel Weber (1 3), Siyuan Zhang (4), Leo Diehl (1 3), Roland Eger (1), Viola Duppel (1), Esther Alarcon-Llado (5), Gunther Richter (6), Frederik Haase (1 3) Anna Fontcuberta i Morral (2 7), Christina Scheu (4), Bettina V. Lotsch (1 3 8 9)
Affiliations : (1) Max-Planck-Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany. (2) Laboratory of Semiconductor Materials, Institute of Materials, Faculty of Engineering, Ecole Polytechnique Fédérale de Lausanne, Station 12, 1015 Lausanne, Switzerland. (3) Department of Chemistry, University of Munich (LMU), Butenandtstraße 5-13, 81377 München, Germany. (4) Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany. (5) AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands. (6) Max-Planck-Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany. (7) Institute of Physics, Faculty of Basic Sciences, EPFL, 1015 Lausanne, Switzerland. (8) Center for Nanoscience, Schellingstraße 4, 80799 München, Germany. (9) Cluster of Excellence e-conversion, Munich, Germany.
Resume : Power-to-gas technologies are on the way to become economically viable in order to make more use of fluctuating renewable energy, but the rational design of hydrogen evolution reaction (HER) electrocatalysts that are competitive with platinum remains to be an outstanding challenge. We present the delafossites PdCrO2, PdCoO2 and PtCoO2 as a new family of highly efficient electrocatalysts for the HER in acidic media and show that the reductive operation can modify their surface and hence, the catalytic performance in different ways. For PdCoO2, the inherently strained Pd metal sublattice acts as a pseudomorphic template for the growth of a tensile strained Pd rich capping layer that ranges up to 400 nm, far beyond epitaxial methods. Its formation continuously improves the electrocatalytic activity by simultaneously increasing the exchange current density j0 and by reducing the Tafel slope down to 38 mV/decade, leading to overpotentials η_10< 15 mV for 10 mA/cm², superior to bulk platinum. We attribute these effects to the strain facilitated operando formation of a β-palladium hydride phase with drastically enhanced surface catalytic properties with respect to bulk or nanostructured palladium. These findings illustrate how operando induced electrochemical modifications can be used as a long ranging top-down design concept for rational surface and property engineering through the strain-stabilized formation of catalytically active phases. F. Podjaski et al. ”Rational strain engineering in delafossite oxides for highly efficient hydrogen evolution catalysis in acidic media.” Nat Catal 3, 55–63 (2020) doi:10.1038/s41929-019-0400-x
|15:45||OPEN DISCUSSION SESSION|
Poster Session (II) : TBC
Authors : Kwang Ho Park, Ji-Seop Shin, Min-Kyeong Jo, Muhammad Saqib, Jun-Young Park
Affiliations : HMC, Department of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05009, Republic of Korea
Resume : Proton ceramic fuel cells (PCFCs) are a electrochemical devices based a ceramic electrolyte that exhibits high protonic conductivity at elevated temperatures. PCFCs have received big attentions as alternatives of oxygen-ion conducting solid oxide fuel cells (SOFCs), because they have high ionic conductivity with low activation of protons, compared to that of SOFCs at intermediate temperatures [1, 2]. Recently, Lee et al. reported that the PCFC with cell size of 5×5 cm2 achieved a power density of 1.3 W‧cm-2 at 600 ℃ by using a Ni-cermet anode-supported cell design with the BaCe0.7Zr0.1Y0.1Yb0.1O3-δ(BCZYYb) electrolyte and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) cathode . However, the BSCF cathode material has limited durability in terms of Sr segregation phenomena and high thermal expansion coefficient (TEC) under PCFC condition. Thus, many researchers try to develop the highly active and stable cathode materials with low activation energy at intermediate temperatures . Usually, cobaltites have good catalytic properties for oxygen reduction reaction. However, TEC of cobaltite-materials is almost twice larger than that of state-of-art BCZYYb electrolyte for PCFCs . Exceptionally, layered cobaltites have low TEC of ~ 10×10-6 K-1 . Hence, in this study, we investigate layered cobaltites as a cathode material to improve thermal stability of PCFCs. In addition, to improve the catalytic property of cathode materials, various metal oxides are doped into layered cobaltites. In addition, doped layered cobaltites are prepared using various synthesis methods such as combustion, citrate-hydrothermal, and acetate methods. To confirm phase purity of synthesized powders, we use Rigaku X-ray diffraction spectroscopy. The symmetric cells are fabricated with the BCZYYb electrolyte and measured by electrochemical impedance spectroscopy at 450-800℃ under wet and dry condition to investigate electrochemical property of materials. References  Kim, J., S. Sengodan, S. Kim, O. Kwon, Y. Bu, and G. Kim, Renewable & Sustainable Energy Reviews 109, 606-618 (2019).  Duan, C. C., J. H. Tong, M. Shang, S. Nikodemski, M. Sanders, S. Ricote, Science 349 (6254), 1321-1326 (2015).  An, H., H. W. Lee, B. K. Kim, J. W. Son, K. J. Yoon, H. Kim, D. Shin, H. I. Ji, and J. H. Lee, Nature Energy 3 (10), 870-875 (2018)  Rioja-Monllor, L., C. Bernuy-Lopez, M. L. Fontaine, T. Grande, and M. A. Einarsrud, Journal of Materials Chemistry A 7 (14), 8609-8619 (2019)  Danilov, N. A., A. P. Tarutin, J. G. Lyagaeva, E. Y. Pikalova, A. A. Murashkina, D. A. Medvedev, M. V. Patrakeev, and A. K. Demin, Ceramics International 43 (17), 15418-15423 (2017)  Rolle, A., S. Boulfrad, K. Nagasawa, H. Nakatsugawa, O. Mentre, J. Irvine, and S. Daviero-Minaud, Journal of Power Sources 196 (17), 7328-7332 (2011). Keywords: Protonic ceramic fuel cells, Thermal expansion coefficient, Electrochemical spectroscopy, Cobaltite cathode * Corresponding author: firstname.lastname@example.org(J. Y. Park)
Authors : M. Khalid Hossain (1,2)*, Y. Hatano (3), K. Hashizume (1)
Affiliations : (1) Department of Advanced Energy Engineering Science, Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-1 Kasugakoen, Kasuga 816-8580, Japan. (2) Atomic Energy Research Establishment, Bangladesh Atomic Energy Commission, Savar, Dhaka 1349, Bangladesh. (3) Hydrogen Isotope Research Center, Organization for Promotion of Research, University of Toyama, Gofuku, Toyama 930-8555, Japan.
Resume : Proton-conducting oxides are promising materials for electrochemical devices like fuel cell, hydrogen pump, hydrogen sensor, etc., and also for tritium purification and recovery system in nuclear fusion reactors. The hydrogen concentration in such oxide materials is very fundamental and important, but its precise measurement is not easy. Tritium tracer method such as tritium imaging plate (TIP) technique is a powerful tool not only for measuring hydrogen concentration but also for clarifying hydrogen behavior in oxide materials. In the present study, hydrogen solubility and diffusivity behavior in three different proton-conducting oxides, BaZr0.9Y0.1O2.95 (BZY), BaZr0.955Y0.03Co0.015O2.97 (BZYC), and CaZr0.9In0.1O2.95 (CZI), were studied by the TIP method using a hydrogen-tritium gas mixture (HT) (T = 0.0001%, ~1.3kPa) and also partially-tritiated heavy water vapor (DTO) (T = 0.1%, ~2kPa) in the temperature range of 623 to 1273 K. The hydrogen solubility and diffusivity behavior in BZY, BZYC, and CZI were also studied by thermal desorption spectroscopy (TDS) using deuterium (D2), heavy water (D2O), and O-18 enriched water (or H218O). The oxide specimens were prepared with conventional powder metallurgy using BZY, BZYC, and CZI powders separately by being die-pressed, cold-isostatically-pressed (200MPa), and sintered in air at 1913 K for 20 h. The specimens obtained were having a disc shape (~7.5 mm in diameter, ~2.3 mm in thickness) and more than 95% TD. From IP images for the surface of all tritium (T) exposed specimens, uniform T distribution was found. Observing cross-sectional T concentration profiles of cut specimens allowed us to determine hydrogen solubility and diffusivity in the specimens. In all cases of tritium exposure (HT and DTO), BZYC always shows the highest hydrogen solubility, while CZI always shows the lowest one. In DTO exposure, the BZY shows the highest hydrogen diffusivity, while in HT the BZYC shows the highest one. In all cases, CZI shows almost one order lower solubility and diffusivity than the BZY and BZYC. These results mean that BaZrO3 shows better electrochemical performance than the CaZrO3 and that a small amount of Y and Co doping in BaZrO3 may play a vital role in the enhancement of its electrochemical activity. Detail comparison of TDS results with TIP data for all three samples will be discussed in the paper in detail. Keywords: BaZrO3; CaZrO3; tritium, deuterium, heavy water, and H218O exposure, hydrogen solubility and diffusivity, fusion reactor materials.
Authors : Tien-Chai Lin1, Wen-Chang Huang1, 2, Bai-Jhong Jheng3
Affiliations : 1 Department of Electrical Engineering, Kun Shan University, No. 195, Kun-Da Rd., Yung-Kang Dist., Tainan, 71003, Taiwan, ROC 2 Green Energy Technology Research Center, Kun Shan University, No. 195, Kun-Da Rd., Yung-Kang Dist., Tainan, 71003, Taiwan, ROC 3 Tintable Kibing Cooperation, Tainan, Taiwan
Resume : The thin film vanadium pentoxide (V2O5) as ion-storage layer for electrochromic device is deposited on ITO glass by an RF magnetron sputtering. The electrochromic properties of the film are discussed after various thermal annealing temperature with/without oxygen flow ambient. It is found that the crystal structure of V2O5 thin film transfer from amorphous to crystalline phases (110) and (021) as the annealed temperature is 400 C. And the grain size of the sample without oxygen flow is larger than that of with oxygen flow after annealing. A degradation of electrochromic property is observed at sample both after the treatment of oxygen flow and thermal annealing. This is due to the oxygen occupies the ion-sites of bleach in/out and results in the reduction of charge capacity. While, an improvement of electrochromic property is obtained at the sample after thermal annealing without oxygen flow. The charge capacity of 69.68 mC/cm2 with a transparent difference, △T between colored/bleached processes of 28.7 % was obtained at the sample after 300 C thermal annealing
Authors : T.S.Björheim,1 M.F. Hoedl,2 R. Merkle,2, E. A. Kotomin,2,3, J. Maier,2
Affiliations : 1 Centre for Materials Science and Nanotechnology, University of Oslo, Norway 2 Max Planck Institute for Solid State Research, Stuttgart, Germany 3 Institute of Solid State Physics, University of Latvia, Riga, Latvia
Resume : Oxide materials can dissociatively incorporate water into oxygen vacancies, but the thermodynamic feasibility of this reaction varies greatly. The individual contributions from proton affinity of lattice oxide ions and hydroxide affinity of oxygen vacancies to the hydration enthalpy are experimentally not accessible. This impedes an in-depth understanding of the hydration trends for different materials. We calculate proton and hydroxide affinities applying a thermochemical cycle based on reaction energies from first-principles DFT calculations; band alignment with respect to vacuum ensures the comparability of the calculated affinities . This scheme is applied to a large variety of oxides ranging from binary oxides (Cs2O to SiO2) to ternary oxides, e.g. BaZrO3. Although the proton and hydroxide affinities describe purely ionic reactions, they strongly correlate with the oxide’s electronic structure, in particular with the ionization potential (position of O2p states relative to vacuum level). The slope is steeper for the proton affinity, naturally explaining the often found phenomenological correlation between basicity and more favorable hydration of the oxide. This analysis will be extended to open-shell proton and electron mixed conducting perovskites (e.g. cathode materials).  T.S. Bjorheim, M.F. Hoedl, R. Merkle, E.A. Kotomin, J. Maier, J. Phys. Chem. C 124 (2020) 1277
Authors : Ie Mei Bhattacharyya, Gil Shalev
Affiliations : School of Electrical and Computer Engineering, Ben Gurion University of the Negev, POB 653, Beer-Sheva, Israel 8410501
Resume : ABSTRACT: Biosensors based on field-effect devices (bioFETs) have gained immense research over the past few decades because of their numerous advantages over existing technologies. Yet, their commercialization remains very limited. The biggest challenge for bioFET realization is the extremely short Debye screening length at high ionic strengths. This problem becomes significantly more severe at the solution-oxide interface due to high ion concentration induced due to the charged oxide surface groups which cripples any attempt to use field-effect mechanism to ‘sense’ the target analytes. In this work, we propose an electrostatic approach to remove the double layer (DL) excess ion concentration, thereby forcing the DL ion concentration to match the bulk concentration. This consequently forces bulk screening length at the DL, thus ‘exposing’ target biomolecules to the underlying FET. To this end, local tunable surface electric fields are introduced to the DL using surface passivated-metal electrodes. The effect of these electric fields on the DL ion distribution are examined numerically and analytically. Also, the feasibility of the proposed approach is demonstrated numerically for a fully-depleted silicon-on-insulator based bioFET. We show how a significant twofold increase in the threshold voltage shift is achieved due to the presence of target molecules upon the removal of the surface excess ion population. Reference  I. M. Bhattacharyya, G. Shalev, Electrostatically-governed Debye screening length at the solution-solid interface for biosensing applications, ACS Sensors, 2019. https://doi.org/10.1021/acssensors.9b01939
Authors : Matthäus Siebenhofer, Tobias Huber, Jürgen Fleig, Markus Kubicek
Affiliations : Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria & Kyushu University, Japan; Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria
Resume : Pulsed Laser Deposition (PLD) is a widely used technique to grow complex oxide films of a given stoichiometry. Due to the complex nature of the process itself, many parameters are known to influence thin film properties, structure or defect concentrations of the deposited thin films. However, the effect of ultraviolet radiation emitted by the plasma plume on thin film and substrate was so far a widely uncharted territory. Recent advances in the understanding of the photoconductivity and the effect of UV radiation on SrTiO3 now raise the question, if and how the UV radiation of the PLD plasma plume affects the electrical properties of an STO substrate during pulsed laser deposition. For this purpose STO single crystals with Pt current collectors were investigated by the means of in situ impedance spectroscopy during pulsed laser deposition (IPLD). By shielding the sample with a quartz disc the effect of the UV light could be isolated from potential effects of impinging species and real film growth. Our measurements revealed an increase of the STO conductivity as a response to the UV light, which persists after the illumination. When a thin STO layer is deposited on top, the conductivity decreases and the aforementioned effect disappears or is cloaked by another effect. This indicates that on the one hand the oxygen exchange on the STO surface is strongly affected by the UV light and that, on the other hand, thin layers of material deposited on the surface dramatically change the behavior of the whole system. The results of in- and across-plane impedance measurements are presented in this contribution.
Authors : D. Kemp, Prof. Dr. Roger A. De Souza
Affiliations : RWTH Aachen University; RWTH Aachen University, JARA-FIT
Resume : The material class of perovskites is well known for over a century and one of their most prominent and most researched representatives is strontium titanate (SrTiO3, short STO). STO is used as a model system in many applications such as solid oxide fuel cells or resistive switching. [1,2] In contrast, the material class of hybrid perovskites is a rather young research field. It has attracted huge attention in the last decade as absorber material in photovoltaic applications.  The main difference between those two material classes is that one component of the usually inorganic perovskite is replaced by an organic molecule, hence the name hybrid perovskite, and one promising candidate of this group is methylammonium lead iodide (CH3NH3PbI3, short MAPI). Both materials – STO and MAPI – have in common that their applications require external electric fields which can influence the material properties in general and particularly the ion transport. In this study we conducted molecular dynamics simulations using the LAMMPS code  and empirical pair potentials derived by Pedone et al.  for STO and Mattoni et al.  for MAPI. These potential sets have already shown by our group to be capable of describing oxygen and iodine diffusion in the respective system. We are able to describe the field-dependent oxide-ion mobility in STO very well with an analytical model from Genreith-Schriever and De Souza ; in contrast the field-dependent mobility of iodide ions in the hybrid perovskite MAPI showed some unusual features. This behavior will be discussed. Literature:  R. Merkle, Angew. Chem. Int. Ed. 2011, 47, 3874.  R. Waser, Adv. Mater. 2009, 21, 2632.  P. Gao, Energy Environ. Sci. 2014, 7, 2448.  S. Plimpton, J. Comp. Phys. 1995, 117, 1.  A. Pedone, J. Phys. Chem. B 2006, 110, 11780.  A. Mattoni, J. Phys. Condens. Mat. 2017, 29, 043001.  A. R. Genreith-Schriever, Phys. Rev. B 2016, 94.
Authors : Martin Krammer *(1), Alexander Schmid (1), Markus Kubicek (1), Jürgen Fleig (1)
Affiliations : (1) Institute of Chemical Technologies and Analytics, Technische Universität Wien, Austria * lead presenter
Resume : Solid oxide electrolysis cells (SOECs) have received growing attention in the last few years as they offer a way to highly efficient hydrogen production. However, degradation effects occurring at the air electrode are a major problem, thus efforts are made to characterise and optimise its performance. The perovskite-type oxide La0.6Sr0.4CoO3-δ (LSC) is a promising material for the air electrode due to its mixed ionic-electronic conductivity and high catalytic activity. Although LSC has been extensively tested in solid oxide fuel cells (SOFCs), comparatively few studies have been made on LSC in the SOEC mode. In this work, the defect chemistry of LSC thin film microelectrodes at varying anodic DC voltages was investigated by analysing the chemical capacitance. Depending on the electrode morphology, unexpected peaks of the chemical capacitance up to 1000 F/cm^3 at overpotentials higher than 100 mV were observed after several hours of annealing at around 600 °C or after applying high bias voltage up to 1 V. Correlations of these capacitive effects with variations of the oxygen exchange kinetics were also investigated. Supposedly, strontium segregation to the surface and a consequential formation of A-site vacancies in the bulk of the electrodes is responsible for these peaks of the chemical capacitance. Hence, a novel defect chemical mechanism connecting the oxygen exchange reaction and A-site vacancies is suggested to contribute to the chemical capacitance of oxides.
Authors : Francesco Ciucci (a, b)
Affiliations : (a) The Hong Kong University of Science and Technology, Mechanical and Aerospace Engineering, Clearwater Bay, Kowloon, Hong Kong, China SAR (b) The Hong Kong University of Science and Technology, Chemical and Biological Engineering, Clearwater Bay, Kowloon, Hong Kong, China SAR
Resume : Mathematical models are ubiquitous in science and engineering and are used to interpret and predict the outcome of experiments and the behavior of devices or systems. Models with varying degrees of complexity are found in the study of electroactive materials, and they have been used to explain the nature of electrochemical reactions. Electrochemical impedance spectroscopy (EIS) is one of the most powerful electrochemical characterization techniques used in electrochemistry research. One of the most challenging steps associated with EIS is interpreting the data, which typically uses non-unique equivalent circuit models. The distribution of relaxation time (DRT) method is an alternative approach to equivalent circuits . However, obtaining DRT from EIS data involves solving an ill-posed inverse problem . We tackle this issue by formulating the DRT problem in a Bayesian statistical framework . The inherent flexibility of the Bayesian framework allows adding our prior knowledge about the DRT. We propose two prior models. First, the regularization penalty term and the regularization parameter itself are treated as multivariate random vectors. Such formulation leads to a timescale dependent regularization giving better DRT recovery than the conventional timescale independent approach. The second prior is proposed for the weights of the fitting residuals. We show by treating them as random vectors that anomalies present in the EIS data can be detected, leading to a better-quality DRT recovery. Also, as the DRT problem is a Bayesian setting, we show that, for a given prior hypothesis, we can sample many possible DRTs from the data . We extend this approach to the context of Gaussian processes (Figure 1). Nevertheless, the DRT obtained from the conventional ridge regularization represents the most probable DRT. Consequently, the Bayesian formulation generalizes the DRT problem. We wish to emphasize the power of the DRT method and the need for using principles of data sciences in the analysis of the measured electrochemical data. Such applications may enable a more profound understanding beyond the ones obtained from conventional analysis methods. Further, they can be used to assess data quality [6-8]. References  M. Saccoccio, T.H. Wan, C. Chen, and F. Ciucci. Electrochimica Acta, 147, 470-482 (2014)  T.H. Wan, M. Saccoccio, C. Chen, and F. Ciucci. Electrochimica Acta, 184, 483-499 (2015)  F. Ciucci and C. Chen. Electrochimica Acta 167, 439-454 (2015)  M.B. Effat and F. Ciucci. Electrochimica Acta, 247, 1117-1129 (2017)  F. Ciucci http://sites.google/drttools & https://github.com/ciuccislab  E. Quattrocchi, T.H. Wan, A. Curcio, S. Pepe, M.B. Effat, and F. Ciucci. 324, 20 November 2019, 134853 (2019)  J. Liu and F. Ciucci. Electrochimica Acta, 331, 135316 (2020)  J. Liu and F. Ciucci. Journal of The Electrochemical Society, 167, 026506 (2020)
Authors : M. Schaube, R. Merkle, J. Maier
Affiliations : MPI for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
Resume : Surface point defects represent centers of enhanced energy and thus enhanced reactivity. For example, the oxygen exchange rate of Gd- and Pr-doped ceria was found to increase strongly with dopant concentration, which increases the concentration of oxygen vacancies (VO..) in case of Gd, and VO.. as well as Pr3 /4 redox active centers for Pr doping. Here, oxidation kinetics of CO and CH4 as test reaction is studied on systematically Pr, Gd, Nb–doped ceria, and Y- and Pr–doped zirconia. CO and CH4 oxidation proceed via the Mars–Van–Krevelen mechanism; the rate–determining step involves the reaction of adsorbed CO with surface layer oxygen, followed by fast CO2 desorption and VO.. formation. Under certain conditions, the competition of oxygen consumption by CO and catalyst re-oxidation by O2 leads to a kinetically determined decreased effective oxygen partial pressure (pO2,eff) inside the catalyst particles, as evidenced by the increased steady state oxygen deficiency. This accelerates the oxygen incorporation until CO oxidation and O incorporation rates are balanced. Samples with lower Pr content exhibit lower pO2,eff values. The presence of pO2,eff affects also the apparent reaction orders. No decreased pO2,eff appears during methane oxidation, because the CH4 oxidation branch is slower than the oxygen incorporation.  J. Maier, Chem. Eur. J. 2001, 7, 4762  M. Schaube et al., J. Mat. Chem. A 2019, 7, 21854  M. Schaube et al., J. Phys. Chem. C 2020, 124, 18544
Authors : Nan Yang
Affiliations : ShanghaiTech University
Resume : Solid oxide fuel cells (SOFCs) represent a clean, efficient, and universal chemical energy-electric energy conversion technology. Reducing its operating temperature to intermediate range (650-850℃) or even lower temperature range (400-650℃) is an important practical requirement. However, the main obstacle to lowering the operating temperature is due to the slow kinetics of the oxygen reduction reaction (ORR) on the cathode side at lower temperatures, and therefore it is important to explore new cathode materials with good ORR activity. Recently, Mixed ion and electron conductor (MIEC) cathodes are widely studied for their good ionic and electronic conductivities. Among them, Sr-doped Lanthanum Cobaltite based cathode is one of the current research hotspots as a MIEC material. The La1-xSrxCoO3-δ (from x = 0 to x = 0.8) thin films were investigated as the electron conductivity and oxygen reduction activity of a medium and low temperature solid oxide fuel cell (SOFC) cathodes. Thin film materials can avoid external interference caused by microstructure and crystal orientation to better explain the complex relationship between chemical composition, electronic conductivity and ORR activity. It was observed that the electronic conductivity and the polarization resistance varied together, and had the best electronic conductivity and polarization resistance at the Sr doping concentration of x = 0.4. The Co3 /Co4 change explains that the electronic conductivity and oxygen reduction activity improve as the Sr doping concentration increases from x = 0 to x < 0.4. As the Sr doping content is further increased, a doping condition exceeding 0.4 favors the oxygen vacancy formation process and can be demonstrated by forming Co2 to balance the system charge. Therefore, Co3 /Co4 is no longer the best choice for surface oxygen reduction. The increased oxygen vacancy concentration provides more oxygen ion exchange sites for the surface oxygen reduction reaction process, and at the same time, the electron conductivity is deteriorated, thereby lowering the charge transfer efficiency of the oxygen reduction process. Although the concentration of oxygen vacancies is enhanced, the highly doped LSCO film, the non-optimal Co3 /Co4 valence state and poor electronic conductivity synergistically cause a decrease in oxygen reduction activity. Finally, it is shown that the electronic conductivity and oxygen reduction activity are related to the Co valence state and the surface composition. Our results demonstrate that tuning the mixed valence state with the electronic band structure can be a valid root in designing cathode materials. In particular, heavily doped LSCO film electrodes could have interesting potentials for SOFCs applications at lower temperature. 1. Zhaoxin Zhu, Yanuo Shi, Carmela Aruta, and Nan Yang, ACS Appl. Energy Mater. 2018, 1, 5308−5317.
Authors : Garcia-Fayos, J.1 *, Catalán-Martinez, D., Laqdiem, M.1, Navarrete, L.1 and Serra J.M.1 *email@example.com
Affiliations : 1 Instituto de Tecnología Química (Universitat Politècnica de València – Consejo Superior de Investigaciones Científicas), Av. Los Naranjos, s/n, 46022 Valencia, Spain
Resume : The strategy most commonly employed for the valorization of the non-profitable by-products in the industry is the burning of these, generating heat and power. The EU project iCAREPLAST considers this approach for the valorisation of a by-product gas mixture composed by pyrolysis gases, oxygenates and other hydrocarbons resulting from the up‐cycling of non-recycled plastic waste into alkyl-aromatics. iCAREPLAST project considers the burning of these undesired gas streams by using pure O2 (oxyfuel combustion) in specially-conceived catalytic membrane reactors (Oxygen Transport Membrane modules) to produce heat and power (integrated in a combined cycle) while applying efficient CO2 capture. This work presents the advances conducted within iCAREPLAST project activities in the application of oxyfuel combustion with OTM modules. Several material compositions have been considered for burning gas hydrocarbon streams (CH4/Ar mixtures) at temperatures in the range of 1000-850 ºC. The CH4 conversion and CO2 selectivity for different membrane composition have been studied. The membranes have been surface activated by adding a porous catalytic layer by screen-printing for the promotion of permeation and combustion. The best results are obtained for BSCF membranes, nearly achieving a total combustion of the HC stream (10% CH4 in Ar), nevertheless, the limited stability of BSCF membranes under reducing and CO2-containing environments makes necessary the selection of more stable alternatives. Other tested compositions show lower results with respect to CH4 combustion towards CO2 generation, despite their high stability.
Authors : Roberts Eglitis
Affiliations : Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., Riga LV1063, Latvia
Resume : Current commercially available rechargeable Li-ion batteries, for example LiCoO2, are working mostly in the 4 V regime. One often suggested possibility to improve the effectivity of Li ion batteries are the creation of the 5 Volt cathode materials. We performed quantum mechanical calculations on the average battery voltage for the Li2CoxMn4-xO8 (x=0,1,2,3 and 4) cathode materials by means of the WIEN2k computer program package. The calculated average battery voltages for x = 0,1,2,3 and 4 are equal to 3.95, 5, 4.47, 4.19 and 3.99 V [1-3]. Our ab initio calculation results are compared with the available experimental data for x = 0, 1, 2 and 4 which are equal to 4, 5, 5 and 4 Volt. Thereby, for the Li2Co1Mn3O8 battery cathode material, our calculated average battery voltage around 5 Volt is in perfect agreement with the experimentally available battery voltage values of 5 Volt. Nevertheless, our calculated average battery voltage is underestimated (4.47 V) for the Li2Co2Mn2O8 cathode material, which also experimentally exhibits the 5 Volt voltage. References:  Roberts Eglitis, Int. J. Mod. Phys. B 33, 1950151 (2019)  R. I. Eglitis, Phys. Scr. 90, 094012 (2015)  R. I. Eglitis and G. Borstel, Phys. Stat. Sol. A 202, R13 (2005)
Authors : M.A. Borik1, A.S. Chislov1,4, G.M. Korableva2, A.V. Kulebyakin1, I.E. Kuritsyna2, E.E. Lomonova1, V.A. Myzina1, P.A. Ryabochkina3, N.Yu. Tabachkova1,4
Affiliations : 1Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia 2Institute of Solid State Physics of the Russian Academy of Sciences, Chernogolovka, Russia 3Ogarev Mordovia State University, Saransk, Russia 4National University of Science and Technology «MISIS», Moscow, Russia
Resume : Zirconia based materials are known for having high values of ionic conductivity at high temperatures, therefore, they are used as a solid electrolyte in the construction of solid oxide fuel cells (SOFCs). In this work, we studied the effect of the chemical composition of zirconia based crystals on their phase composition, local structure and transport characteristics. A comparative analysis of two systems was carried out: zirconia stabilized only with ytterbium oxide and zirconia stabilized together with ytterbium and scandium oxides. Crystals of (ZrO2)1-x-y(Sc2O3)x(Tb2O3)y and (ZrO2)1-x-y(Sc2O3)x(Yb2O3)y were grown by directional crystallization of a melt in a cold container using direct high-frequency heating. Investigations of the phase composition were carried out by Raman scattering and x-ray phase analysis. The conductivity of the crystals was measured by impedance spectroscopy. The local structure of the grown crystals was studied by optical spectroscopy using Eu3+ ions as a spectroscopic probe. This work was performed with the financial support of the Russian Science Foundation (grant № 19-72-10113).
Authors : Grieshammer, S.*(1), Eisele, S.(1), Draber, F.(1), Martin, M.(1).
Affiliations : (1) Institute of Physical Chemistry, RWTH Aachen University, Germany
Resume : Acceptor doped barium zirconate is a promising proton conductor suitable as electrolyte in protonic-ceramic fuel cells. The doping with e.g. yttria leads to the formation of oxygen vacancies and exposing to a hydrating atmosphere at elevated temperatures introduces mobile protons into the system leading to high proton conductivity. The degree of hydration is a function of the partial pressure water and the temperature. In most studies, the classical mass action law for non-interacting defects is applied to model the defect chemistry of this system and connect the proton concentration to the thermodynamic parameters. However, at typical defect concentrations the interactions of defects are no longer negligible. The present study investigates influence of defect interactions on the free energy of hydration in yttrium-doped barium zirconate. Combining a DFT derived interaction model with an MMC multistage sampling approach [1,2], we obtain the free energy of interaction, which can be separated into contributions to the internal energy and the configurational entropy. Neglecting volume changes, the interaction dependent part of the equilibrium constant is deductible from the free energy of interaction. This enables an ab-initio calculation of the relation between water partial pressure and degree of hydration for a concentrated, interacting system. First results indicate intermediate degrees of hydration as the energetically favorable state, as the attractive interactions between dopant and protons cannot compensate rising proton-proton repulsion and entropy loss indefinitely.  J. P. Valleau and D. N. Card, J. Chem. Phys., 57, 5457, 1972  S. Grieshammer and M. Martin, J. Mater. Chem. A, 5, 9241, 2017
Authors : Tobias M. Huber a,b,c,*; Matthaeus Siebenhofer a; Alexander Schmid a; Alexander Viernstein a; Markus Kubicek a; and Jürgen Fleig a;
Affiliations : a Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, Vienna, A-1060, Austria; b Next-Generation Fuel Cell Research Center (NEXT-FC), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan; c Huber Scientific, Rottmayrgasse 17/29, Vienna, A-1120, Austria;
Resume : Oxides which change their defect concentration with the oxygen partial pressure p(O2) are important materials for solid oxide fuel and electrolysis cells (SOFCs, SOECs) and sensors. Exact characterization of these materials over a large p(O2) range is necessary to understand their defect related properties such as ionic and electronic conductivity. For such measurements two different oxygen pump systems were designed and constructed: one was integrated in the hull of the experimental chamber while the other one is insertable into an experimental chamber. The capability of these setups are exemplified with measurements on LaSrFeO3 (LSF) thin film electrodes and SrTi O3 (STO) single crystals. The first setup shows an outstanding pumping performance (from 10-5 bar to 10-17 bar oxygen partial pressure in less than 5 minutes). The second setup can be equipped with an additional oxygen sensor directly next to sample in the electrochemical measurement cell. This design has two advantage: i) the oxygen pump is kept at one temperature while the electrochemical cell operates at various measurement temperatures and ii) the setup can be operated statically with different chamber base pressures or with continuous gas stream. The oxygen partial pressure is controlled with a PID controller to automatically change the desired set point. Additionally, the setup can be connected to mass flow controllers and a furnace controller to automatically change all experimental parameters. Different cells can be implemented, for example for Van-der-Pauw, current voltage and impedance measurements on thin films, pellets and microelectrodes.
Authors : Alexander Bonkowski, Ji Wu, Roger A. De Souza, Stephen C. Parker
Affiliations : Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany; Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK; Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany; Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
Resume : Recent experimental work has demonstrated that catalytically active nanoparticles with enhanced stability can be readily dispersed on a perovskite oxide support through a process of ex-solution. This process produces socketed nanoparticles, which show high activity and are more resistant to catalytic poisoning. One such example is exsolved nickel on lanthanum doped strontium titanate support that can be used for syngas production by methane steam reforming. However, the transport of the dopant and the formation of the metal nanoparticle are still not well understood. We have begun to address this by using a range of atomistic simulation techniques. Potential based molecular dynamics were used to investigate the dynamics of nickel diffusion in lanthanum-doped strontium titanate. While nickel favourably resides on B-sites, A-site deficiency is found to be a key factor in determining the migration barrier and the diffusion rate. We also found evidence of enhanced lanthanum and nickel diffusion, as seen in experiments. However, when larger concentrations of lanthanum dopants are present, lanthanum rich layers form and are predicted to inhibit diffusion. We also investigated the transport at surfaces and found low energy barriers and trapping sites on surface layers. One of the advantages of atomistic simulation is that compositional changes can be easily made, and we illustrate this by exploring the effect of different dopants such as Fe and Mn and the effect of different host lattices by replacing strontium titanate with calcium titanate.
Authors : Antipinskaia, E.A., Politov, B.V., Suntsov, A.Yu., Kozhevnikov, V.L.
Affiliations : Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russia
Resume : Today, within the framework of materials science topics, the leading positions are consistently occupied by the studies on the perovskite-like structures with general formula ABO3. Despite saving sustained interest in these compounds over the years and a wide range of studied compositions and their properties, continued development in this direction does not lose its relevance up to this day. In particular, layered compounds with alterating rock-salt and perovskite blocks - so called Ruddlesden-Popper phases, for example manganites, till now were not studied in much detail compared to other perovskite structure modifications. However, with a more thorough research, these objects show curious features, thereby potentially representing scientific interest. In the scope of current work, layered perovskite-like oxides corresponding to the chemical formula Sr4-yCayMn3-xFexO10-δ, where y = 0; 3, x = 0; 1; 2, were synthesized using the glycine-nitrate method. The X-ray diffraction confirmed the obtained compounds to be single-phase. This work includes the studying of oxygen non-stoichiometry dependences on temperature and oxygen pressure, calculation and measurement of specific heat effects, as well as thermal cycling test of degradation resistance. Accordingly, these compounds appear to be promising not only for a further detailed research, but also for practical application as oxygen carrier materials in the developing technology of thermochemical energy storage.
Authors : Politov B.V., Marshenya S.N., Mychinko M.Yu., Suntsov A.Yu., Shein I.R., Zhukov V.P., Kozhevnikov V.L.
Affiliations : Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russia
Resume : Complex oxides of d-metals with perovskite-like structure are acquiring great attention in modern science. Apparently, the number of fields these compounds can be applied for is constantly growing due to the enormous amount of their functional properties discovered. For instance, the so-called “double perovskites” possess high electron/ion mobility, good catalytic and magneto-transport properties in wide range of external conditions (temperature, pressure, magnetic field etc.). In this regard, the practical aspects of their usage are undoubtedly better studied experimentally rather than theoretically. Accordingly, the lack of theoretical knowledge should be somehow filled with. This work is aimed at ab initio investigation of various typical representatives – strontium molybdates, layered cobaltites and recently discovered Co-based double perovskites with high Ta/Nb concentrations. All these are perspective candidates for practical use as solid oxide fuel cell electrodes. In this study we try to analyze using combined theoretical and experimental approaches how the electron band structure features of the initial phases are changing upon doping and what are the reasons underlying the respective alterations in functional properties of materials considered. The results of the research done provide solid fundamental for recent experimental findings and also propose some new advantageous doping strategies. This work was supported by the RFBR under grant №19-33-90173
Authors : Tom Underwood, John Purton, Steve Parker
Affiliations : Tom Underwood, Department of Chemistry, University of Bath, United Kingdom; John Purton, Scientiﬁc Computing Department, STFC Daresbury Laboratory, United Kingdom; Steve Parker, Department of Chemistry, University of Bath, United Kingdom
Resume : Many state-of-the-art energy materials can be regarded as solid oxides with a certain amount of dopant atoms which act to enhance their properties. It is well known that the dopant species can exhibit segregation at interfaces in the material (e.g. surfaces, grain boundaries), and that this can have a significant effect on key properties of the material such as its conductivity. However, a detailed understanding of this phenomenon is lacking. There is considerable interest in being able to determine: 1) for a given dopant element and concentration, to what extent segregation will occur at different types of interface in the material; 2) what effect the segregation will have on key properties of the material. Computer simulation is in principle able to answer these questions. However, due to the large activation energies associated with dopant diffusion, often equilibrium cannot be reached in reasonable timescales using standard simulation methods. We have explored alternative simulation methods for studying segregation, and have found that Monte-Carlo-based methods allow the atomic-scale equilibrium segregation profiles at grain boundaries and surfaces to be determined efficiently, even when used in conjunction with state-of-the-art models commonly employed in molecular dynamics simulations of oxides. Here we present results for ceria-zirconia, a material of interest due to its catalytic properties. We use Monte-Carlo methods to determine the miscibility gap and cation ordering tendencies in bulk ceria-zirconia, as well as the segregation profiles at various surfaces and grain boundaries. Our simulations provide fundamental insights into ordering and segregation phenomena in ceria-zirconia and similar systems.
Authors : Vincent Thoréton(1), Reidar Haugsrud(1)
Affiliations : (1) Centre for Materials Science and Nanotechnology (SMN), University of Oslo, Gaustadalléen 21, NO-0349, Norway.
Resume : In the field of Solid-State Ionics, it is often necessary to determine the absolute oxygen stoichiometry of materials. It is commonly measured in a given temperature range and at a given oxygen partial pressure by coupling iodometric titration to thermogravimetric measurement. Iodometry titration provides the absolute oxygen stoichiometry at room temperature and thermogravimetric measurement provides the relative change of oxygen stoichiometry. It is possible as well to determine an absolute oxygen stoichiometry at high temperature by reducing the material to a definite mixture of components, commonly metal oxides (rock-salt structure) or metal. In certain conditions, these approaches may fail to provide valid results. We report here an alternative approach by isotopic titration. The method consists in equilibrating a sample with a definite amount of labelled diatomic oxygen. The isotopic fraction of labelled oxygen is measured in the gas phase before and after annealing the system at high temperature until complete homogenisation of the isotope fraction in the sample and in the atmosphere is achieved. Benefits and limitations of the approach are discussed.
Authors : Vidyanand Vijayakumar, Diddo Diddens, Andreas Heuer, Sreekumar Kurungot, Jijeesh Ravi Nair, Martin Winter
Affiliations : Vidyanand Vijayakumar; Sreekumar Kurungot Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune-411008, Maharashtra Diddo Diddens; Andreas Heuer; Jijeesh Ravi Nair; Martin Winter Helmholtz Institute Münster, IEK-12, Forschungszentrum Jülich GmbH, Corrensstraße 46, 48149 Münster, Germany.
Resume : Free-radical copolymerization of a reactive solution consisting of a difunctional poly(ethylene glycol) diallyl ether oligomer (PEGDAE), a monofunctional reactive diluent 4-vinyl-1,3-dioxolan-2-one (VEC), and a stock solution containing lithium salt (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI) in a carbonate-free non-volatile plasticizer, poly(ethylene glycol) dimethyl ether (PEGDME) is achieved by means of ultraviolet (UV)-light irradiation. Hence obtained cross-linked polymer electrolytes (XPEs) possessed a unique structure with cycling carbonate moieties attached to linear polyethylene chains which are cross-linked by ethylene oxide (EO) units. By changing [O]/[Li ] ratio from 24 to 3, a series of XPEs were prepared and physicochemical properties are characterized by thermogravimetric analysis–mass spectrometry, differential scanning calorimetry, NMR, etc., and electrochemical techniques. Quantum chemical calculations provided insights into the coordination of Li -ions and EO units. The XPEs exhibited RT ionic conductivity in the order of 10-4 and 10-5 S/cm. The addition of lithium bis(fluorosulfonyl)imide (LiFSI) salt along with LiTFSI resulted in dual-salt XPEs exhibiting improved physical and electrochemical properties. All the single- and dual-salt XPEs exhibited electrochemical stability between 4.2 and 5V vs. Li|Li facilitating them to be employed against high-voltage cathodes in lithium metal batteries (LMBs). Remarkably, NCA-based lithium metal cells displayed excellent cycling stability (capacity retention >50%) even after 1000 cycles when operated at 20oC.
Authors : Andreas Bumberger,Joseph Ring,Claudia Schrenk,Andreas Nenning,Jürgen Fleig
Affiliations : TU Wien
Resume : Solid-state diffusion in lithium intercalation compounds is one of the most important processes determining the overall kinetics in lithium-ion cells and placing practical constraints on the composition and morphology of composite electrode coatings. Thin films of lithium intercalation compounds offer a suitable platform for the extraction of the underlying intrinsic material properties from electrochemical impedance spectra. However, although lithium intercalation compounds generally constitute a class of mixed ionic and electronic conductors, the relevant literature currently relies on the traditional finite-length diffusion model that neglects electronic resistances and treats the resulting Warburg impedance as a simple two-terminal element in equivalent circuits. Most commonly, the reflective-boundary Warburg element is incorporated into the intuitively derived Randles circuit. In this work, we apply the generalized transmission line model proposed by Jamnik and Maier [Phys. Chem. Chem. Phys., 2001, 3, 1668-1678] to the specific case of lithium intercalation materials and thus also go beyond the assumptions underlying the traditional Randles model by considering both electronic and ionic resistances in the material as well as differentiated pathways for capacitive and ohmic charge transfer across the contact interfaces. This model is applied to study ambipolar diffusion in oriented LiCoO2 thin films. An aqueous three-electrode cell is used to control the state of charge (SOC) and to measure cross-plane impedance spectra. This revealed information on SOC-dependent conductivities, interfacial resistances, and chemical capacitances. Furthermore, we extend our analysis to in-plane impedance measurements at low SOC, where cross-plane impedance spectra typically do not allow a separation of solid-state diffusion from interfacial charge transfer kinetics. Finally, we discuss the relationships between the ambipolar diffusion coefficient, chemical capacitance, and electronic and ionic conductivities.
Authors : Joseph Ring, Lukas Ladenstein, Markus Kubicek, Herbert Hutter, Steffen Ganschow, Andreas Nenning, Daniel Rettenwander, Jürgen Fleig
Affiliations : TU Wien; TU Graz; TU Wien; TU Wien; Leibnitz-Institut für Kristallzüchtung; TU Wien; TU Graz, Christian Doppler Laboratory for Solid-State Batteries; TU Wien
Resume : Cubic Li7La3Zr2O12 (LLZO) based garnet electrolytes are promising for solid state batteries, due to their high conductivity and stability towards Li-metal anodes. The stability of LLZO towards high voltage cathodes, however, is less clear. According to DFT calculations, the thermodynamic stability window of LLZO ranges only up to 3-3.3 V vs. Li0, whereas experimental studies with ion blocking electrodes report a stability window up to 5-6 V vs Li0. The practically usable voltage range of LLZO electrolytes is therefore an important unresolved question. LiCoO2 (LCO) is a well understood and widely used cathode material ranging up to about 4.2 V. Fortunately, the electrolyte degradation is slow at room temperature, so operation of LCO|LLZO cells is possible. For cell fabrication, however, higher temperatures are required at which undesired solid-state reactions occur between LLZO and LCO. Various phases, consisting of Li, La, Zr, Co and O, are formed at the LLZO-LCO interface. These undesired phases have low Li-ion conductivity, hence reducing the overall Li-ion conductivity of the system. Furthermore, diffusion of Co into the garnet may be an issue. A method to minimize these undesired reactions is therefore critical for the use of LLZO electrolytes with high voltage cathodes. In this work, we aim at the fabrication of kinetically fast LLZO-LCO interfaces by sputter deposition of LCO thin film electrodes on LLZO electrolytes. Among others, we tested the effect of a Li-Nb-O interlayer, which partly prevents the undesired reactions. The kinetics of Co diffusion in LLZO at various temperatures was determined via secondary ion mass spectroscopy (SIMS). The effects of cobalt impurities on the bandgap and conductivity of LLZO were investigated by means of UV-VIS spectroscopy. Changes of ionic and electronic conductivities were determined using DC and AC methods. The electrochemical Li (de)intercalation properties of symmetrical LCO-LLZO-LCO cells and LCO-LLZO-Li cells were measured by means of DC-cycling and electrochemical impedance spectroscopy (EIS) in order to find optimal processing parameters for efficient lithium transfer. The interfacial impedance was measured as function of the state of charge by means of microelectrodes. We found that the charge transfer kinetics of the LLZO-LCO interface can differ drastically from liquid electrolytes and strongly depend on the state of charge and fabrication parameters. We expect that our studies will help to better understand and optimize the kinetics of Li transfer at the LLZO-LCO interface.
Authors : Lucile Bernadet (1), Marc Torrell (1), Dario Montinaro (2), Alex Morata (1), Albert Tarancón (1, 3)
Affiliations : (1) Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy, Jardins de les Dones de Negre 1, 2nd Floor, 08930 Sant Adria de Besos, Barcelona, Spain (2) SOLIDPower SpA, Viale Trento 117, Mezzolombardo, 38017, Italy. (3) ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain Tel.: +34 933562615 (ext. 225) firstname.lastname@example.org
Resume : Gadolinium-doped ceria (CGO) barrier layer placed between yttrium-stabilized zirconia (YSZ) electrolyte and strontium-based electrode aims to avoid the formation of insulating phase SrZrO3 during solid oxide fuel cell operation. However, this phase was observed in as-fabricated state-of-the-art cells, which evidences cation inter-diffusion during the sintering process . The use of vacuum techniques such as sputtering and Large Area Pulsed Laser Deposition (LA-PLD) allows the implementation of dense layers at lower temperature compared with traditional deposition techniques (i. e. screen printing). CGO barrier layer deposition and annealing parameters were optimized in a previous work from the group and led to an increase of 70% in power density at 750ºC and 0.7 V compared to a state-of-the-art button cell. Remarkable results were also obtained when the PLD barrier layer was up-scaled to large area cells of 80 cm2 and tested in short-stack configuration for long-term operation . This short-stack, that includes state-of-the-art cells as well as the large-area PLD ones, was aged for a total of 14,000 h at 750ºC for the first 8,000 h and 700ºC until the end of the experiment. Cells with PLD barrier layer showed enhanced initial performances with a low degradation rate. This work presents a post-mortem characterization of the barrier layers and interfaces in both types of cells. Scanning-electronic microscope, Electron Probe Micro Analysis with Wavelength Dispersive X-Ray (EPMA-WDX), micro-Raman spectroscopy and TEM were used to observe any microstructural changes as well as any changes in composition due to cation inter-diffusion.  Morales et al., Journal of Power Sources 344 (2017) 141-151.  Morales et al. ACS Applied Energy Materials 1 (2018) 1955-1964.
Authors : Lucile Bernadet (1), Carlos Moncasi (1), Marc Torrell (1), Albert Tarancón (1, 2)
Affiliations : (1) Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy, Jardins de les Dones de Negre 1, 2nd Floor, 08930 Sant Adria de Besos, Barcelona, Spain (2) ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain Tel.: +34 933562615 (ext. 225) email@example.com
Resume : State of the art SOEC are complex structures requiring many fabrication steps and are still presenting durability issues. On one side, fuel electrodes, usually made with Ni YSZ (yttria stabilized zirconia Y2O3-ZrO2) cermets, suffer re-oxidation, Ni volatility and agglomeration and coking issues during pure CO2 electrolysis and co-electrolysis. On the other side, oxygen electrodes, usually made with La1 xSrxMO3 δ (LSM) YSZ composites or by mixed ionic-electronic conducting (MIEC) perovskite like La1 xSrxCo1 yFeyO3 δ (LSCF), are subject to delamination problem or inter-diffusion of ions. This work presents the study of symmetrical solid oxide cells made with Sr2Fe1.5Mo0.5O6−δ (SFM) electrodes. The symmetrical configuration allow a reduction of sintering steps and an improvement of the electrodes-electrolyte thermomechanical compatibility meanwhile the use of MIEC perovskite/metallic electrodes enables operations under steam electrolysis (SOEC) or co-electrolysis (co-SOEC) without the use of reducing safe gas at the fuel electrode. YbScSZ tapes previously coated with a Ce1 xGdxO1.9 (GDC) barrier layer grown by pulsed laser deposition were used as electrolyte supports. Electrode sintering temperature was optimized by means of electrochemical impedance spectroscopy (EIS) measurements in both air and H2 symmetrical atmosphere. The cell was then characterized at 900ºC in SOEC and co-SOEC modes without the use of any safe gas obtaining high current densities of 1.4 and 1.1 A·cm-2 at 1.3 V respectively. Short-term reversibility was finally proven by switching the gas atmosphere between the cathode and anode sides while keeping the electrolysis conditions. Similar performances are obtained in both configurations.
Authors : Qaisar Khushi Muhammad1, Lukas Porz1, Atsutomo Nakamura2, Katsuyuki Matsunaga2, Marcus Rohnke3, Jürgen Janek3, Jürgen Rödel1 and Till Frömling1
Affiliations : 1Division of Non-metallic-Inorganic Materials, Department of Materials and Earth Sciences, Technical University of Darmstadt, Darmstadt, 64287, Germany 2Department of Materials Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan 3Physikalisch-Chemisches Institut & Zentrum für Materialforschung (ZfM), Justus Liebig University, Gießen, 35392, Germany
Resume : The functional properties of ceramics are classically tailored by designing point defects and interfaces. Dislocations as heavily charged line defects have so far been underappreciated as a means to tune functionality but are finding increasing attention today. To modify electrical properties of rutile (TiO2), (a semiconductor with wide bandgap prevalent due to its important applications in gas sensors and solar cells), defect engineering via chemical doping has an important role. However, often the solubility limit of the dopants restricts this method for tailoring material properties significantly while it increases material complexity . Here, we demonstrate the possibility to induce equivalent conductivity enhancements akin to conventional chemical doping by mechanically introduced dislocations. We combine the understanding of mesoscopic dislocation structure and its behavior at elevated temperatures, which results in highly arranged dislocation bundles in single crystals. By controlling the mesoscopic structure of dislocations, we are able to both enhance and reduce the electrical conductivity. These changes are documented by temperature and oxygen partial pressure dependent conductivity measurements. Furthermore, local impact of dislocations is afforded by micro-contact impedance spectroscopy. In this way, the prospect of dislocations as “self-dopant” is presented, where the additional design parameter of the dislocation arrangement renders them potentially superior to conventional chemical doping strategies.  M. K. Nowotny, L. R. Sheppard, T. Bak, J. Nowotny, Phys. Chem. C 2008, 112, 5275-5300
Authors : Erik A. Wu, Grayson Deysher, Darren H.S. Tan, Yu-Ting Chen, Yixuan Li, Ying Shirley Meng, Jean-Marie Doux
Affiliations : Erik A. Wu; Darren H.S. Tan; Yixuan Li; Ying Shirley Meng; Jean-Marie Doux Department of NanoEngineering, University of California San Diego, La Jolla, CA 92093. Grayson Deysher; Yu-Ting Chen Department of Materials Science and Engineering, University of California San Diego, La Jolla, CA 92093. Ying Shirley Meng Sustainable Power & Energy Center (SPEC), University of California San Diego, La Jolla, CA 92093.
Resume : Owing to the unique properties of solid electrolytes, rechargeable solid-state sodium-ion batteries (SSSBs) hold great promise for safe and sustainable energy storage applications. In addition to safety, more energy-dense batteries can be built by using higher voltage cathodes together with dense stacking architectures. Moreover, SSSBs are a more cost-effective alternative due to the higher abundance of sodium compared to conventional lithium. All of these advantages make SSSBs particularly attractive for large-scale grid storage applications. However, the poor electrochemical stability of current sulfide-based solid electrolytes, especially when used in conjunction with higher-voltage oxide cathodes, has largely limited their long-term cycling performance and practicality. Here, we report the computationally-assisted discovery of a chloride Na-ion conductor, Na3-xY1-xZrxCl6 (NYZC), that is both chemically compatible with oxide cathodes and electrochemically stable (up to 3.8 V vs. Na/Na+). Its exhibits a relatively good ionic conductivity of 6.6 x 10-5 S cm-1 at ambient temperature, several orders of magnitude higher than commonly used oxide coatings. This performance is attributed to abundant Na vacancies and facilitated by cooperative MCl6 polyanionic rotation, resulting in an extremely low interfacial impedance. This makes NYZC a promising candidate to be adopted in a cathode composite with an oxide cathode (such as NaCrO2) in order to mitigate the detrimental interfacial reactions commonly observed with sulfide electrolytes. As such, a SSSB comprising a NaCrO2 + NYZC composite cathode, Na3PS4 electrolyte, and Na-Sn anode exhibits an exceptional first-cycle Coulombic efficiency of 97.1% at room temperature and demonstrates impressive cycling capabilities: over 1000 cycles with 89.3% capacity retention at 40°C. These findings validate the coupled computational/experimental approach to find new electrolyte materials and highlight the immense potential of halide ion conductors for SSSB applications. Reference: Wu, E.; Banerjee, S.; Tang, H.; Richardson, P. M.; Doux, J.-M.; Qi, J.; Zhu, Z.; Grenier, A.; Li, Y.; Zhao, E.; Deysher, G.; Nguyen, H.; Stephens, R.; Verbist, G.; Chapman, K. W.; Clément, R. J.; Banerjee, A.; Meng, Y. S.; Ong, S. P. A Stable Cathode-Solid Electrolyte Composite for Long-Cycle-Life, High Voltage Solid-State Sodium-Ion Batteries. 2020. https://doi.org/10.26434/chemrxiv.12730964.v1.
Authors : Seoungmin Chon (1), Ryota Shimizu (1,2), Yuki Sugisawa (3), Shigeru Kobayashi (1), Kazunori Nishio (1), Daiichiro Sekiba (3,4), and Taro Hitosugi (1)
Affiliations : (1) Department of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan.; (2) PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan.; (3) Graduate School of Pure and Applied Sciences, University of Tsukuba, 1–1–1 Tennoudai, Tsukuba, Ibaraki, 305–8573 Japan.; (4) University of Tsukuba Tandem Accelerator Complex (UTTAC), 1–1–1 Tennoudai, Tsukuba, Ibaraki, 305–8577 Japan
Resume : Ammonia (NH3) is an important chemical source of fertilizers and possible candidates for hydrogen storage materials . To facilitate these applications, fast conversion between NH3 and H2-N2 is required. Recently, calcium compounds combined with nitrogen and hydrogen attracts attention as promising catalysts for the fast conversion. Among them, Ca2NH and CaNH exhibit high catalytic performance in NH3 synthesis and decomposition, respectively [1,2,3]. To quantitatively understand the mechanism of the catalytic reactions, epitaxial thin film surfaces can provide an ideal platform due to well-defined size and crystal orientation. However, neither Ca2NH nor CaNH thin films have been reported to date. In addition, due to the structural similarity between Ca2NH and CaNH, it is difficult to selectively stabilize each phase using epitaxial effects. In this study, under various gas conditions, we study a route to selectively fabricate Ca2NH and CaNH epitaxial thin films using reactive magnetron sputtering. Ca-N-H thin films were deposited on MgO(110) substrates using reactive magnetron sputtering with a mixture of Ar, N2, and H2 gases. Structural properties were characterized using X-ray diffraction and Raman spectroscopy. At lower H2 partial pressure (PH2) of 0.020 Pa, we observed diffraction peaks at 2-theta= 50.9°. As PH2 increased to 0.074 Pa, the 2theta position was shifted to 49.9°. This suggests the phase transition from Ca2NH (440, 2-theta = 51.0°) to CaNH (220, 2theta = 50.1°). This phase transition scenario was confirmed by evaluating the chemical composition using Rutherford backscattering spectroscopy (RBS), elastic recoil detection analysis (ERDA), and nuclear reaction analysis (NRA). As a result, the chemical compositions of thin films fabricated under PH2 = 0.016 and 0.074 Pa were CaN0.55H0.37 (~Ca2N1.1H0.73) and CaN0.85H0.82, respectively. These values are consistent with the phase transition scenario, indicating PH2 plays an important role in selective control of the Ca2NH/CaNH phases. To the best of our knowledge, this study is the first report of metal-nitrogen-hydrogen epitaxial thin films.  M. Kitano et al., Chem. Sci., 2016, 7, 4036.  P. Yu et al., J. Energy Chem., 2020, 46, 16-21.  K. Ogasawara et al., Proceeding of Annual/Fall meetings of the Japan Petroleum Institute, 2019, 26, (in Japanese).
Authors : Alexander Stangl (1), Adeel Riaz (1), Juan de Dios Sirvent (2), Federico Baiutti (2), Albert Tarancón (2,3), Mónica Burriel (1)
Affiliations : (1) Univ. Grenoble Alpes, CNRS, Grenoble INP*, LMGP, 38000 Grenoble, France * Institute of Engineering Univ. Grenoble Alpes; (2) Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy, 08930 Barcelona, Spain; (3) ICREA, 23 Passeig Lluís Companys, Barcelona 08010, Spain
Resume : Energy conversion and storage systems based on solid oxide fuel cells (SOFCs) are promising candidates for future power solutions due to their high efficiency, low cost, hazard-free and sustainable material components. Miniaturisation and portabilisation require low operation temperatures (≤500°C). However, this leads to decreased electrochemical performance and increased polarization resistance, with sluggish cathode surface activity being the major source. Engineering structural characteristics on a nanoscale is key for improved ionic properties and advanced performance. In this study we investigate the Ruddlesden-Popper phase La2NiO4, a highly interesting electrode material for micro-SOFCs, due to its low activation energy of the surface exchange activity. By growing La2NiO4 thin films by pulsed injection Metalorganic Chemical Vapor Deposition (PI-MOCVD) on various substrates and with different thicknesses we were able to tune the film orientation and strain and analyze its effect on the oxygen exchange activity. Microstructure, morphology and chemical composition were characterized by XRD, SEM, AFM, TEM, Raman spectroscopy and XPS. The oxygen activity was studied by electrical conductivity relaxation and electrochemical impedance spectroscopy. We found very high surface exchange coefficients and low area specific resistance (ASR) values at low temperatures (400-500°C) as compared to other cathode materials. The oxygen incorporation in these films was identified to be surface limited, in which the specific step depends on the type of crystal growth (e.g. epitaxial or polycrystalline). TEM analysis of the material revealed a largely increased surface area through the combination of vertically spaced grain growth on top of a dense layer. Hence, the remarkable high oxygen activity found in the studied thin films is likely caused or enhanced by these morphological features, pointing towards a possible pathway to further foster the electrochemical performance of this promising cathode material.  Connor, P. A. et al. Tailoring SOFC Electrode Microstructures for Improved Performance. Adv. Energy Mater. 8, 1–20 (2018).  Kilner, J. A. & Burriel, M. Materials for Intermediate-Temperature Solid-Oxide Fuel Cells. Annu. Rev. Mater. Res. 44, 365–393 (2014). Acknowledgment: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 824072 (Harvestore).
Authors : Melanie Maurer, Harald Summerer, Christoph Riedl, Alexander K. Opitz
Affiliations : TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria, TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria;
Resume : In recent times, an alternative method to conventional catalyst preparation has gained significant interest: the exsolution of catalytically active metal species from perovskite-type host oxides, thus obtaining oxide-supported catalysts with superior properties. In a recent study we showed that this type of catalysts shows the interesting feature of being electrochemically switchable between a very active metallic state and a less active oxidic state . However, a better understanding of the electrochemical switching behavior of the exsolved catalyst particles is of major interest. In the present study, the switching point between high and low activity states was investigated on different perovskite electrode materials. Electrodes were subjected to different electrochemical polarization and atmospheres (mixtures of H2/H2O in argon) and the electrochemical behavior was studied via impedance measurements and current-voltage characteristics. Furthermore, changes in the surface species were detected by near ambient pressure photoelectron spectroscopy (NAP-XPS). These measurements were carried out on La0.6Sr0.4FeO3-δ (LSF) and Nd0.6Ca0.4FeO3-δ(NCF) thin film electrodes, which were grown by pulsed laser deposition on yttria stabilized zirconia crystals. In addition, further experiments were conducted to reveal how doping with elements easier reducible than iron (e.g. Co or Ni on the B site of the perovskite) influences the current voltage characteristics and how they alter the electrochemical switchability of the studied exsolution catalysts.  A. K. Opitz et al. Understanding electrochemical switchability of perovskite-type exsolution catalysts. Nat. Communications. 2020, 11, 1-10.
Authors : Kirsten Rath, Harald Summerer, Christoph Riedl, Jürgen Fleig , Alexander Karl Opitz
Affiliations : TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9, 1060 Vienna, Austria TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9, 1060 Vienna, Austria; TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9, 1060 Vienna, Austria;
Resume : In solid oxide fuel cells (SOFCs) oxygen reduction is one of the major factors limiting cell performance. Improving the mechanistic understanding of the oxygen exchange reaction is thus of high importance. Even though platinum is not a typical SOFC cathode material, platinum microelectrodes on yttria-stabilised zirconia (YSZ) electrolyte offer an excellent model system for investigation of triple phase boundary (TPB) dominated cathode kinetics and have thus been extensively investigated in the past . Despite this long and extensive history of inquiry, the exact reaction mechanism of oxygen exchange on Pt/YSZ is not completely understood until now. The goal of this study was to achieve a more detailed mechanistic understanding of the oxygen exchange on the free YSZ surface close to the TPB. Especially the possibility of an electron transfer via the electrolyte and thus a significant role of the YSZ defect chemistry is in the focus of this work. Dense and geometrically well-defined microelectrodes were prepared by magnetron sputter deposition of Pt on YSZ single crystals followed by micro-structuring via photolithography and ion-beam etching. The electrodes were electrochemically characterised by impedance and current voltage curve measurements at different temperatures and oxygen partial pressures. In addition, buried hetero-layers with different electronic conductivity are applied to alter the lateral electronic conductivity of the electrolyte, thus being able to modify the decay length of electrochemical activity at the TPB.
Authors : K. Khuu1, G. Lefèvre3, C. Jiménez1, H. Roussel1, S. Blonkowski2, E. Jalaguier2, A. Bsiesy3 and M. Burriel1
Affiliations : 1: Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, 38000 Grenoble, France 2: Univ. Grenoble Alpes, CEA, LETI, 38000 Grenoble, France 3: Univ. Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, 38000 Grenoble, France
Resume : Resistive switching (RS) is the change in resistance of a Metal-Insulator (or Semiconductor)-Metal (MIM) capacitor-like structure under an external electric field. This topic has attracted researchers’ attention for its application in Non-Volatile Memories (Resistive Random Access Memories, or ReRAMs) and neuromorphic computing systems due to their simple structure, high operation speed and low power consumption . This work uses La2NiO4+δ (L2NO4), a mixed ionic electronic oxide well known for its highly mobile oxygen interstitial ions, as a memristive layer. It has also been reported that the oxygen content in the L2NO4 structure, which influences the memory characteristics, can be tuned by thermal treatments in different gas atmospheres . Some recent studies reported very promising results on nickelate memristive devices grown as epitaxial thin films [2,3]. However, they still present shortcomings, such as the impossibility of building L2NO4-based memristors in cross-bar array architectures and their integration into Complementary Metal Oxide Semiconductor (CMOS) technology. Thus, we focused on using Pt/TiO2/SiO2/Si, a CMOS-compatible substrate, to build Ti/L2NO4/Pt heterostructures as memristive devices in a “top-bottom” vertical configuration. The L2NO4 films were grown using Pulsed Injection Metal-Organic Chemical Vapour Deposition (PI-MOCVD). The deposition temperature and precursor ratio were optimized to obtain highly dense and thin films suitable for memristive devices. The successful growth of polycrystalline L2NO4 films on Pt was confirmed by the Grazing Incidence X-ray Diffraction (GI-XRD). Moreover, to study the interaction between the electrodes, L2NO4 film and substrate layers, Scanning Transmission Electron Microscopy (STEM) cross-section analyses were carried out after the electrodes’ evaporation on top of the film, showing sharp interfaces and the absence of interdiffusion between the layers. An analogue-type bipolar resistive switching behavior has been demonstrated for the first time in the Ti/L2NO4/Pt devices in top-bottom configuration. Besides, highly reproducible RS with well-defined resistance states is observed when cycling the devices multiple times. These results open the door to the use of L2NO4-memristors in cross-bar architectures in CMOS integrated circuits and to their testing as novel elements for neuromorphic computing.  Z. B. Yan and J. M. Liu, “Resistance switching memory in perovskite oxides,” Ann. Phys. (N. Y)., vol. 358, pp. 206–224, 2015.  K. Maas et al., “Tuning Memristivity by Varying the Oxygen Content in a Mixed Ionic – Electronic Conductor,” vol. 1909942, pp. 1–10, 2020.  K. Maas et al., “Using a mixed ionic electronic conductor to build an analog memristive device with neuromorphic programming capabilities,” J. Mater. Chem. C, 2019.
Authors : Dominika A. Buchberger a, Maciej Boczar a, Jacek B. Jasinski b, Meghnath Jaishi b, Badri Narayanan b, Bartosz Hamankiewicz a, Andrzej Czerwiński a
Affiliations : a Faculty of Chemistry, University of Warsaw, Pasteura 1, Warsaw Poland b Conn Center for Renewable Energy Research, University of Louisville, Louisville, USA
Resume : In situ techniques are advanced and important experimental methods to study lithium battery materials and full cell batteries [1-2]. Among various approaches, in situ Raman spectroscopy was recently used to investigate such promising cathode materials as LixNi0.8Co0.15Al0.05O2 , LixNi0.8Mn0.1Co0.1O2 , LiNi0.5Mn0.5O2 , xLi2MnO3·(1–x)LiMO2 , a commercial composite of NMC811&NMC111 . Thanks to this method we can obtain information about their local structural changes at the surface due to lithium deintercalation/intercalation and study the phase transitions due to electrochemical reaction. In this work, we performed in situ Raman spectroscopy on a commercial NMC111 material to study the structural changes upon first cycles. Additionally, we completed ex situ XRD and Raman experiments to further explore the structural transformations. The first cycle shows the most significant changes once lithiated to high potentials vs. Li+/Li (Fig. 1). The spectral evolution during the delithiation and lithiation exhibits four major changes (new modes development and intensity variations). Based on data collected from in situ Raman and ex situ methods, a further theoretical approach will be employed to study Raman mode positions to improve a recent interpretation of peak evolution. This work helps to extend the knowledge on the structural changes and reversibility at the high voltage charging and deep discharging of NMC-type materials especially atractive for a solid-state battery designs. D.A.Z. and M.B. thank the support through the Homing program of the Foundation for Polish Science (POIR.04.04.00-00-5EC3/18-00) co-financed by the European Union under the European Regional Development Fund. References:  S. Hwang et al. J. Phys. D: Appl. Phys. 2020, 53, 113002  P.P.R.M.L.Harks et al. J. Power Sources 288 (2015) 92-105  E. Flores et al. Chem. Mater. 2018, 30, 14, 4694-4703  C. Ghanty et al. ChemElectroChem 2015, 2, 1479 – 1486  S. Hy et al. J. Am. Chem. Soc. 2014, 136, 3, 999-1007  P. Lanz et al. Electrochimica Acta 2014, 130, 206-212  C.-Y. Li et al. J. Phys. Chem. C 2020, 124, 7, 4024-4031
Authors : Andreas Nenning, Jürgen Fleig, Alexander Opitz
Affiliations : TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria
Resume : In comparison to bulk properties of Gd-doped ceria (GDC), little is known about the electrical grain boundary properties in thin films. This lack of knowledge arises from the small cross-sectional area of thin films, which makes separation of impedance features rather challenging. Here, we use embedded interdigitating Pt electrodes with spacing of few micrometres to separate grain and grain boundary conductivity of GDC thin films and characterise the effect doping and atmosphere . Since the used embedded Pt thin film electrodes are blocking for oxygen ions and reversible for electrons, they allow determination of partial electronic and ionic conductivities by comparison of the high frequency and low frequency intercepts of the impedance arcs. Surprisingly, the ionic conductivity of the films increases by up to one order of magnitude when going from oxidising to reducing atmosphere, although the concentration of oxygen vacancies is dominated by the p(O2) independent extrinsic vacancies. We find the largest effect for films with low doping concentration and low temperature, where the grain boundary blocking factor is highest. Preliminary results also indicate a strong p(O2) dependence of the ion conduction in porous GDC-based SOFC anodes, which can only be explained by grain boundary effects. After defect chemical modelling, we find that the p(O2) dependence of the grain boundary resistance is in line with the widely accepted grain boundary space charge model. The results are of high relevance for optimising the properties of GDC in anodes and electrolytes for solid oxide fuel cells, as well as for understanding electrostrictive and memristive devices, for which oxygen partial pressure dependent ionic conductivity is an important new aspect.  Nenning, A.; Opitz, A. Low Oxygen Partial Pressure Increases Grain Boundary Ion Conductivity in Gd-Doped Ceria Thin Films. J. Phys. Energy 2019, 2, 014002, doi:10.1088/2515-7655/ab3f10.
Authors : Abdessalem Aribia, Jordi Sastre, Xubin Chen, Ayodhya N. Tiwari, Yaroslav E. Romanyuk
Affiliations : Laboratory for Thin Films and Photovoltaics, Empa, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
Resume : Layered oxide cathode materials are used in modern Li-ion batteries. However, during prolonged device operation they suffer from surface degradation, transition metal dissolution and destructive phase transitions at the cathode-electrolyte interface. One way to suppress the chemical instability and reactivity of the cathode with the electrolyte is to coat the cathode surface with inert oxides such as niobium oxide (Nb2O5). To investigate the effect of oxide coatings, all functional battery layers can be deposited as thin films, which offers a flexible platform for investigating interfacial phenomena. The anode, electrolyte and cathode layers are clearly distinct over a large area, isolating interfacial phenomena and simplifying their investigation. An ALD process for Nb2O5 is presented, which acts as a coating for the thin-film LiCoO2 cathode fabricated by magnetron sputtering. Impedance measurements showed that it was necessary to lithiate the niobium oxide coating for an adequate ion transport, which was achieved by annealing the coated cathode at 700 °C for 1 hour. To investigate the electrochemical performance, liquid electrolyte half-cells were assembled with Li foil as anode. In this first step, the focus lies on the power density of the modified cathodes. By investigating cathode and coating thickness, increased rate performance could be demonstrated. Such Nb2O5-coated LiCoO2 cathodes showed at 20 C charge rate, 80% capacity retention relative to 1 C, which for uncoated cathodes, no capacity remained at that rate. Detailed elemental analysis with TOF-SIMS and XPS revealed both bulk and surface effects of the niobium oxide coating. These results suggest that ALD as a coating method can stabilize the cathode-electrolyte interface and improve the long-term performance of layered transition-metal oxide cathodes.
Authors : Jonas Deuermeier(1), Maria Pereira(1), Jorge Martins(1), Carlos Silva(1), Philipp Wendel(2), Dominik Dietz(2), Andreas Klein(2), Rodrigo Martins(1), Elvira Fortunato(1), Asal Kiazadeh(1)
Affiliations : 1: i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa and CEMOP/UNINOVA, Campus de Caparica, 2829-516 Caparica, Portugal; 2: Technische Universität Darmstadt, Institute of Materials Science, 64287 Darmstadt, Germany
Resume : Amorphous oxide semiconductors (AOS) based on mixtures of transition metal cations (zinc, indium, gallium, tin) are widely used in thin film optoelectronics. Memristors with AOS are typically reported based on ion migration. The charge-trapping type switching in thin film diodes is less explored. However, it offers certain advantages for passive crossbar applications, such as area-scaling, low-power programming, and self-rectification without requiring electroforming. The common switching characteristic is a set in the diode’s forward polarity. In this poster, an overview is presented of charge-trapping type resistive switching in diodes of the most common AOS (indium-gallium-zinc oxide and zinc-tin oxide). All devices were crosspoint structures, patterned by photolithography. The state-dependent conduction mechanisms are discussed and compared to pure barrier height switching observed in crystalline ZnO thin film diodes.
Authors : Juan de Dios Sirvent (1), Aitor Hornés (1), Guilhem Dezanneau (2), Pascale Gemeiner (2), Iria Monterroso (1), Alex Morata (1), Federico Baiutti (1), Albert Tarancón (1,3)
Affiliations : (1) Catalonia Institute for Energy Research (IREC), Jardins de Les Dones de Negre 1, 08930 Sant Adrià Besos, Barcelona, Spain; (2) Université Paris-Saclay, CentraleSupélec, CNRS, Laboratoire SPMS, 91190, Gif-sur-Yvette, France; (3) ICREA, 23 Passeig Lluís Companys, Barcelona 08010, Spain.
Resume : In a context where the Internet of Things technologies will be needing a great deal of self-powered devices, the development of sustainable and efficient energy microdevices becomes critical in order to meet the energy demand of wireless electronic systems and low-power grid nodes. Reversible, full-ceramic micro solid oxide cells (-SOCs) represent a compelling approach for harvesting ambient energy in chemical form (electrolysis mode) and to release it as electric power (fuel cell mode). In the present study, we present an investigation on the structural and electrochemical properties of full-ceramic hydrogen and air electrodes. One of the limiting areas that -SOCs face is given by the selection of the hydrogen electrode, as it must present mixed ionic-electronic conductivity and high thermal stability in reducing conditions, while keeping the catalytic activity for the hydrogen oxidation reaction. In this work, results on the synergistic behavior of different hydrogen electrode materials (Ce- and Cr/Mn-based) are presented. The architectures studied consist in both dense and partially porous films, fabricated either as a nanocomposite or following a bilayer configuration. The films were fabricated by pulsed laser deposition (PLD) and characterized by complementary structural and electrochemical techniques (X-ray diffraction, electron microscopy, atomic force microscopy, and electrochemical impedance spectroscopy). We propose heterostructures based on (La,Sr)(Cr,Mn)O3 and samarium-doped-ceria, which present high electrochemical performance and overcome the limitations in terms of sheet conductivity of state-of-art doped-ceria. To shed light on the properties of oxygen ceramic electrodes, a high throughput screening methodology based on combinatorial PLD was designed for the analysis of the La0.8Sr0.2CoxFeyMnzO3 (x=1-y-z) perovskite family. This method allows to fabricate, in a single deposition process, a wafer containing the composition of the parent compounds together with a gradient distribution of the intermediate stoichiometries. The multicomponent sample was characterized by X-ray diffraction, Raman spectroscopy and spectroscopic ellipsometry, leading to a mapping of the structural and optical properties. The electrochemical properties were measured sequentially along the wafer by electrochemical impedance spectroscopy. The study provides a general method for the full characterization of a library of materials fabricated in a single run and measured under the exact same conditions.
Authors : Maritta Lira (1)*, Lucile Bernadet (1), Simone Anelli (1), Alex Morata (1), Marc Torrell (1), Albert Tarancon (1,2)
Affiliations : (1) IREC, Catalonia Institute for Energy Research, Jardins de les Dones de Negre 1, 2º, Sant Adrià del Besós, Barcelona, 08930, Spain. (2) ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain.
Resume : Solid Oxides Cells (SOC) has been playing a fundamental role in the green and sustainable energy businesses due to the possibility of integrating the direct usage of carbon-based fuels and renewable energies to convert by-products into valuable fuels. Through all the components of these devices, electrodes are a key part in terms of the efficiency and durability. Studies have been carried on for decades in order to improve the matrix of chemical composition, microstructure, and performance. Moreover, research on efficient synthesis and exsolution of nanostructured perovskite oxides are attracting intensive attention nowadays. Surfaces decorated with consistently catalytically active nanoparticles assume a crucial role in numerous fields, such as sustainable power source, photocatalysis, conversion, and in high-temperature catalysis applications such as in solid oxide cells as electrodes. Hence, to implement this strategy in practical electrodes for solid oxide fuel cells, understanding the exsolution process in terms of synthesis temperature and the atmosphere is a prerequisite. Herein, we demonstrate the study of synthesis and characterization of different perovskite electrode materials based on the exsolution of catalytically active dopants by the solid precipitation of the functional active elements, such as: Ni on the Ni doped Gd0.1Ce0.9O2-δ (GDC) perovskite (Ni-GDC) as anode materials and Ag doped La0.8Sr0.2MnO3 (Ag-LSM) to lower the cathode operation temperatures. Both electrode materials can - under determined conditions of temperature and reducing atmosphere - exsolve the dopant element that remains exposed on the surface, increasing the catalytic activity of the former material. Insights into the exsolution mechanism are also derived from both experiments. Microstructural and morphological characterization of the electrode materials with exsolved active phases was carried out by X-ray diffraction, differential scanning calorimetry (DSC), temperature-programmed reduction (TPR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Electrochemical impedance spectroscopy (EIS) was carried out at operating temperature to evaluate the performance of the exsolved materials as electrodes for SOFC.
Authors : A.G. Sabato (1), M. Nuñez (1), S. Anelli (1), M. Torrell (1), A. Morata (1), A. Tarancón (1,2)
Affiliations : (1) Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy, Jardins de les Dones de Negre 1, 2nd Floor, 08930 Sant Adria de Besos, Barcelona, Spain (2) ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain
Resume : Many efforts in the field of Li-ion batteries are focusing on the development and implementation of solid electrolytes in order to overcome the drawback related to their liquid counterparts such as: flammability, complex encapsulation requirements, high cost and complexity manufacturing processes. Li-conducting glass-based materials gained attention in the last years as solid state electrolytes for lithium batteries, thanks to their good ionic conductivity at room temperature (10-3-10-4 S cm-1) and their wide electrochemical stability windows. In the present work, Li1.5Al0.5Ge1.5P3O12 (LAGP) glass was 3D-printed by robocasting and stereolitography (SLA) in free-form robust self-standing structures with the main target to obtain 3D batteries with high active area (allowing high specific energy and power per unit volume). The use of 3D printing techniques allowed the fabrication of simple as well as complex architectures, with enhanced contact area with the electrodes. The inks and the printing processes were both optimized in order to reach an accuracy up to ≈100 µm. The printed structures demonstrated an excellent densification after the firing/sintering treatment, as a result of the optimization of the inks formulation, printing process and sintering conditions. Furthermore, ionic conductivity of 3D-printed LAGP electrolyte resulted to be 1.8 10-4 S cm-1 at room temperature, in accordance with the values measured on the same material processed with conventional methods. No detrimental reaction products or degradation phenomena were detected by chemical analyses after the sintering. The successful implementation of 3D printing techniques in LAGP processing represents an innovative approach that will push further the development of all solid state Li-ion batteries with enhanced energy density, thanks to the easy fabrication of 3D structured solid electrolytes.
Authors : Moritz L. Weber (a, b, c, d), Marek Wilhelm (e), Lei Jin (c, f), Uwe Breuer (g), Regina Dittmann (b, c), Rainer Waser (b, c, h), Olivier Guillon (a, d, i), Christian Lenser (a), Felix Gunkel (b, c)
Affiliations : a Institute of Energy and Climate Research (IEK-1), Forschungszentrum Juelich GmbH, 52425 Juelich, Germany b Peter Gruenberg Institute (PGI-7), Forschungszentrum Juelich GmbH, 52425 Juelich, Germany c Juelich-Aachen Research Alliance (JARA-FIT), 52425 Juelich, Germany d Institute of Mineral Engineering (GHI), RWTH Aachen University, 52062 Aachen, Germany e Peter Gruenberg Institute (PGI-6), Forschungszentrum Juelich GmbH, 52425 Juelich, Germany f Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Juelich GmbH, 52425 Juelich, Germany g Central Institute for Engineering, Electronics and Analytics (ZEA-3), Forschungszentrum Juelich GmbH, 52425 Juelich, German h Institute for Electronic Materials II (IWE II), RWTH Aachen University, 52056 Aachen, Germany i Juelich-Aachen Research Alliance (JARA-Energy), 52425 Juelich, Germany
Resume : Metal exsolution has evolved as an efficient synthesis route for supported nanoparticles with great potential for diverse applications in the field of catalysis and electrochemistry. Catalytically active dopants are released to the perovskite oxide surface in the form of metallic nanoparticles via a thermal treatment in reducing atmosphere. This allows for the fabrication of nanostructured composite materials, which is particularly interesting for the in-situ activation of fuel electrodes for solid oxide cells (SOCs). In the present study, we employ SrTi0.9Nb0.05Ni0.05O3-ẟ (STNNi) thin films fabricated by pulsed laser deposition (PLD) as model systems for the systematic study of the mechanistic processes governing nickel exsolution. Here, the growth of nanoparticles at the (001) crystal facet is observed and the release of nickel to the perovskite surface is monitored by chemical and structural analysis of the thin films. Microscopic investigations reveal spontaneous phase separation and the presence of Ni-rich nanostructures embedded within the perovskite host lattice, which serve as centers for the formation of metallic nanoparticles in the perovskite bulk. Based on the specific structural characteristics of the material system, a modified exsolution pathway needs to be considered which is shown to result in a considerably different exsolution behaviour compared to exsolution from solid solutions. Using a defect engineering approach, the interplay of exsolution behaviour and lattice defects is studied, where the defect structure of the perovksite host lattice is controlled and systematically varied based on the laser fluence applied for thin film growth. Here, a limitation of the exsolution dynamics for non-stoichiometric thin films is found to be correlated to a distortion of the perovskite host lattice.
Authors : Jacob M. Dean, Samuel W. Coles, William R. Saunders, Matthew J. Wolf, Andrew R. McCluskey, Alison B. Walker, Benjamin J. Morgan
Affiliations : Department of Chemistry, University of Bath and The Faraday Institution; Department of Chemistry, University of Bath and The Faraday Institution; Department of Physics, University of Bath; Department of Physics, University of Bath; Department of Chemistry, University of Bath and “Data Management and Software Centre, European Spallation Source ERIC”; Department of Physics, University of Bath; Department of Chemistry, University of Bath and The Faraday Institution
Resume : Grain boundaries are known to impact ionic conductivities in solid electrolytes, with mobile ions often possessing reduced ion mobilities in grain boundary regions. The resistive properties of grain boundaries can generally be separated into two contributions: 1) an increased potential energy barrier caused by the structural rearrangement of bulk crystals at the grain boundary core, and 2) the formation of space-charge regions, areas of bulk electrolyte adjacent to the core where charged defect concentrations are altered due to an accumulation or depletion of charged defects at the core. Conventional approaches to investigating space-charge formation use one-dimensional, continuum mean-field models, such as the Mott-Schottky and Gouy-Chapman models. These mean-field, dilute limit models predict an exponential decay of charged defects away from the interface. However, these models have been shown to perform less well outside of the dilute limit, where defect interactions are unlikely to be well described by the simple mean-field approach. To test the performance and validity of the Mott-Schottky model beyond the dilute limit, we use kinetic Monte Carlo simulations on a simple, model grain boundary system, and extract resultant space-charge profiles for a number of concentrations and relative permittivities. We find the Mott-Schottky model performs well in a dilute regime but deteriorates quickly for concentrated systems. We propose an analytical form for the deviated charged defect profiles at high concentrations. This study improves our understanding of the behaviour of charged defects at interfaces in concentrated systems. This improved understanding could help facilitate the generation of methods to reduce the interfacial resistances in solid electrolytes.
Authors : Alexander Gutsche, Sebastian Siegel, Jinchao Zhang, Sebastian Hambsch, Regina Dittmann
Affiliations : Peter Grünberg Institut (PGI-7&10), Forschungszentrum Jülich Gmbh, 52428 Jülich, NRW, Germany
Resume : The most common resistive switching memory systems show filamentary switching, which stochastic filament formation process causes a high variability. In this work, we studied in detail heterostructures of the mixed valence managnite PrxCa1-xMnO3 and insulating interface tunnel barrier layers. This type of memory devices show area-dependentn currents, a gradual SET and RESET and suffer less from device variability. This provides analog-switching and the possibility to adept the device current to a given circuit requirement. We will present the impact of different interface layers and their processing conditions on the switching characteristics of polycrystaline PrxCa1-xMnO3 thin films grown on Pt substrates. The difference between an oxide (TaOx, WOx and AlOx) and a metal (Ta, W, Al and Mo) as interface layer will be presented and the underlying mechanisms will be explained. The gradual switching type enables us to demonstrate learning algorithms, such as Spike Timing Dependent Plasticity or Long Term Potentiation/Depression. Furthermore, we investigated the influence of pulse height and length variations during the LTD/LTP measurement and perceptron simulations with the measured variations will be presented.
Authors : I. Kogut (1), I. Gamov (2), K. Irmscher (2), M. Bickermann (2), H. Fritze (1)
Affiliations : (1) Clausthal University of Technology, Am Stollen 19B, 38640 Goslar, Germany (2) Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489, Berlin, Germany
Resume : Single crystalline aluminum nitride (AlN) shows attractive properties if used as piezoelectric resonator at temperatures above 500 °C. The covalent bonds present in the material are favorable as they enable low acoustic losses. Application of AlN resonators as robust pressure or temperature sensor in harsh environments appears to be feasible. However, high quality bulk crystals and understanding of the defect mechanisms are required to take advantage of these properties. AlN crystals are initially grown by physical vapor transport under varying conditions to achieve samples that exhibit different doping concentrations for carbon, oxygen and silicon. They exhibit, for example, a wide range of electrical conductivity. The determination of electrical and acoustic properties and their correlations are the focus of this work. Beside fundamental crystal properties, the temperature dependences of electrical and resonant properties are determined from room temperature up to about 900 °C. The resonance spectra are acquired by resonant piezoelectric spectroscopy and used to extract the acoustic loss. The latter is of particular interest and in general caused by several mechanisms that dominate commonly in certain temperature ranges and that depend on the type and/or concentration of the defects. The investigations include intrinsic phonon-phonon interaction (minor contribution at high temperatures), anelastic relaxation of point defects and losses related to electrical conductivity. The temperature dependences of the latter two mechanisms can be described by Debye functions using materials parameters such as relaxation times and electrical conductivity. Superposition of several Debye functions is applied to model the overall loss and to obtain indications about the dominant mechanisms. At low and medium temperatures, high contributions of anelastic relaxation of point defects are observed in oxygen-dominated AlN samples. The origin is assumed to be point defect complexes (Al vacancies and oxygen defects) and possibly electrically inactive defects. The lowest overall losses are found for lowest concentration of oxygen impurities. At higher oxygen concentration ([O]/[C] = 4.0 and 1.7), a relatively high background governs the total losses up to about 250 °C. For high C or O concentrations the relaxation of charge carriers dominates at temperatures of from about 650 to 900 °C. Further, the long-term stability of AlN crystals at 900 °C and low oxygen partial pressure of 10-17 bar is investigated over 22 days. Within this period of time, the resonance frequency decreases by only 0.36%. The losses are low and remain virtually unchanged. Finally, the losses in AlN are compared with those of other high temperature stable piezo-electric crystals. Above about 500 °C and at a given resonance frequency, AlN exhibits lower losses than the high-temperature stable piezoelectric oxide crystal langasite (La3Ga5SiO14).
Authors : Frida Paulsen Danmo, Benjamin A. D. Williamson, Didrik R. Småbråten, Sandra H. Skjærvø, Sathya P. Singh, Kjell Wiik, Tor Grande, Julia Glaum, Sverre M. Selbach
Affiliations : Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
Resume : Hexagonal rare earth manganites, h-RMnO3 δ (R=Sc, Y, Lu-Ho), are known to accommodate large amounts of interstitial oxygen  at intermediate temperatures of 200-400 °C , making them applicable as catalysts and oxygen carriers in chemical looping combustion (CLC) . As these materials are highly refractory, nanocrystalline particles can withstand harsh operating conditions and are stable against grain growth at higher temperatures . The magnitude of δ, as well as the thermal stability of these interstitial defects, can be fine-tuned by aliovalent doping and particle size, but these effects are not well understood. Here, we study the effects of R-cation, crystallite size and donor doping on oxygen absorption in h-RMnO3 δ (R=Y, Ho, Dy). Thermogravimetry and high temperature X-ray diffraction show that oxygen absorption increases from R=Y through R=Ho, Dy, and with decreasing crystallite size. Donor doping with Ti further enhances oxygen absorption for all R and stabilize excess oxygen to significantly higher temperatures, extending the operation temperature window for catalysis and CLC. Density functional theory (DFT) calculations reveal trends in the effects of R-cation and donor doping on the enthalpy of oxidation and oxygen migration through the lattice.  Skjærvø et al. Nature Commun. 7 (2016) 13745.  Remsen et al. Chem. Mater. 23 (2012) 3818.  Fossdal et al. Int. J. Greenhouse Gas Control 5 (2011) 483.  Bergum et al. Dalton Trans. 40 (2011) 7583.
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Solid State Electronic Devices: Resistive Switching : Mónica Burriel
Authors : Venkata R. Nallagatla, Thomas Heisig, Christoph Baeumer, Vitaliy Feyer, Matteo Jugovac, Giovanni Zamborlini, Claus M. Schneider, Rainer Waser, Miyoung Kim, Chang Uk Jung, Regina Dittmann
Affiliations : V. R. Nallagatla; T. Heisig; Dr. C. Baeumer; M. Jugovac; Dr. G. Zamborlini; Dr. V. Feyer; Prof. Dr. C. M. Schneider; Prof. Dr. R. Waser; Prof. Dr. R. Dittmann Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany V. R. Nallagatla; Prof. Dr. C. U. Jung Department of Physics and Oxide Research Centre, Hankuk University of Foreign Studies, Yong-in 449-791, South Korea T. Heisig; Dr. C. Baeumer; Prof. Dr. R. Waser Institute of Electronic Materials, IWE2, RWTH Aachen University, 52056 Aachen, Germany Prof. M. Kim Department of Material Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 151-747, South Korea Dr. V. Feyer; Prof. Dr. C. M. Schneider Fakultat f. Physik and Center for Nanointegration Duisburg-Essen (CENIDE), Universitat Duisburg-Essen, 47048 Duisburg, Germany Dr. G. Zamborlini Technische Universitat Dortmund, Experimentelle Physik VI, 44227 Dortmund, Germany
Resume : Redox-based based memristive devices are one of the most attractive candidates for future non-volatile memory applications and neuromorphic circuits. For the most common memristive band insulators, resistive switching is induced by the formation of oxygen vacancies and the resulting valence change on the cation sublattice. However, manganites, cobaltites and ferrates undergo a topotatic phase transition between the perovskite and the brownmillerite structure upon reduction that might also be induced during resistive switching. Due to the spatially confined redox-process, experimental proofs of topotactic phase transitions in memristive devices are very rare. By employing X-ray absorption spectromicroscopy, we demonstrate that the reversible topotactic phase transition between the insulating brownmillerite phase, SrFeO2.5, and the conductive perovskite phase, SrFeO3, gives rise to resistive switching of SrFeOx memristive devices. Interestingly, we found that the electric field induced phase transition spreads over a large area in (001) oriented SrFeO2.5 devices, where oxygen vacancy channels are ordered along the in-plane direction of the device. In contrast, (111) grown SrFeO2.5 devices with out-of-plane oriented oxygen vacancy channels, reaching from bottom to the top electrode, show a localized phase transition. We attribute this difference in the extension of the topotactic phase transition to the anisotropic oxygen ionic conduction in the brownmillerite structure.
Authors : Alejandro Fernández-Rodríguez1, Jordi Alcalà1, Jordi Suñe2, Anna Palau1 and Narcis Mestres1
Affiliations : 1. Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain 2. Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
Resume : Memristive devices are attracting a great deal of attention for memory, logic and sensing applications due to their simple structure, high density integration, low-power consumption, and fast operation. In particular, multi-terminal structures controlled by active gates would certainly provide novel concepts for reconfigurable electronic systems with engineered functionality. In this work we will show the potential of reversible field-induced metal-insulator transition (MIT) in strongly-correlated metallic oxides for the design and obtention of multi-terminal memristive transistor-like devices [1, 2]. We have studied the highly correlated cuprate YBa2Cu3O7-δ as a model system, which is able to display non-volatile volume MIT, driven through local oxygen migration. In this way, vertical and lateral oxygen mobility may be modulated, at the micro- and nano-scale, by tuning the applied bias voltage and operating temperature. The key advantage of this material is the possibility to homogeneously modulate the oxygen vacancy diffusion not only in a confined filament or interface, as observed in widely explored insulating strongly correlated oxides, but also toward the whole film thickness. We will show different device configurations in which the lateral conduction of a bridge is controlled by active gate-tunable volume resistance changes. Large design flexibility can be obtained by changing the switching performance of different gates, thus offering the possibility to locally adjust the conductance response as required for non volatile memories and neuromorphic functionalities. References  A. Palau et al. ACS Applied Materials & Interfaces. 10, 30522, 2018  J.C. Gonzalez-Rosillo et al. Adv. Elect. Mater. 1800629, 2019
Authors : Jacqueline M. Börgers, Joe Kler, Regina Dittmann, Roger A. De Souza
Affiliations : Institute of Physical Chemistry, RWTH Aachen University, Aachen, Germany and Peter Grünberg Institut 7, Forschungszentrum Jülich GmbH, Jülich, Germany ; Institute of Physical Chemistry, RWTH Aachen University, Aachen, Germany ; Peter Grünberg Institut 7, Forschungszentrum Jülich GmbH, Jülich, Germany; Physical Chemistry, RWTH Aachen University, Aachen, Germany
Resume : Mixed-valence manganites are very promising candidate materials for resistive-switching devices due to the possibility to generate multilevel resistance states as well as area-dependent switching. This enables their use in future non-volatile memories or novel neuromorphic circuits. The aim of our work is to gain a deeper understanding of the microscopic mechanisms of resistive switching in mixed valence manganites with the focus on Sr-doped LaMnO3 (LSMO). It is widely accepted that ionic transport, especially oxide-ion transport, plays an important role in the field of resistive switching. Nevertheless, the role played by dislocations (one dimensional lattice defects) in the switching process is unknown. LSMO is unusual amongst the perovskite oxides, since it is the only system to show fast diffusion of oxygen along dislocations. The reasons for this behaviour are however not understood. To this end, we studied the ionic transport in bulk LSMO as well as along low-tilt grain boundaries (that consist of a periodic array of dislocation) by Molecular Dynamics simulations, employing empirical pair potentials. Additionally, we studied the ionic transport experimentally in comparable thin films, grown by Pulsed Laser Deposition (PLD), using Secondary-Ion Mass Spectrometry (SIMS).
Authors : Carlos Moncasi, Raquel Rodríguez-Lamas, Odette Chaix-Pluchery, Hervé Roussel, Laetitia Rapenne, Carmen Jiménez, Mónica Burriel
Affiliations : Univ. Grenoble Alpes, CNRS, Grenoble INP (Institute of Engineering Univ. Grenoble Alpes), LMGP, F-38000 Grenoble, France
Resume : Manganite thin films exhibit interesting properties for applications such as resistive switching (RS) memories , Micro Solid Oxide Fuel Cell cathodes, spintronic sensors and micro solar cells . In thin films, the functional properties depend on the microstructure and composition. In particular, for valence change memories (VCM) the resistance change relies on the oxygen vacancies drift, so RS phenomena are expected to be tunable by varying the film nanostructure. Strontium substituted LaMnO3 (La1-xSrxMnO3±δ, LSM) was selected as a potential candidate to improve the performance and reliability of VCMs. 20% Sr-substituted LSM thin films were grown by Pulsed Injection Metal-Organic Chemical Vapour Deposition under optimized conditions. Different nanostructures were obtained by growing epitaxial LSM thin films on LaAlO3 (LAO) and SrTiO3 (STO) single crystals, which results in compressive and tensile in-plane strain, respectively. Devices of Ti/LSM\Pt in top-top configuration were microfabricated on both types of films to assess the role of the nanostructure on the RS phenomena. Whereas the devices on both types of films show reproducible, counter-8-wise (C8W) and analog response, HRS/LRS ratios one order of magnitude higher as well as much larger retention times were measured for the LAO substrate-devices. The RS response was related to the nanostructure characteristics of the manganite films. These results allow further comprehension of the LSM nanoionic properties and can lead to the optimization of manganite memristive devices with high storage capacity and fast operation time.  R. Rodriguez-Lamas, D. Pla, O. Chaix-Pluchery, B. Meunier, F. Wilhelm, A. Rogalev, L. Rapenne, X. Mescot, Q. Rafhay, H. Roussel, M. Boudard, C. Jiménez, M. Burriel, Beilstein J. Nanotechnol. 2019, 10, 389.  D. Pla, C. Jimenez, M. Burriel, Adv. Mater. Interfaces 2017, 4, 1600974.
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Defects & Transport Phenomena (II) : Felix Gunkel
Authors : George F. Harrington
Affiliations : Kyushu University; Massachusetts Institute of Technology
Resume : Perturbing the crystal lattice away from the equilibrium structure via an applied lattice strain has been investigated from some time as a method to realise considerable improvements in oxygen-ion conductivity. Interest in this approach has, however, waned over recent years for two primary reasons: (i) a lack of consistency and reproducibility in the reported experimental findings and (ii) typically only modest changes in ionic transport are observed. In this presentation, we will address both reasons and make the case for lattice strain still being a promising route to enhanced oxygen transport. By using an unconventional method of thermally annealing out strain which occurs during deposition of epitaxial rare earth-substituted films grown by PLD, we were able to tailor the strain with no influence from grain boundaries or interfaces. Through careful analysis of the literature, we managed, for the first time, to develop a quantitative consensus on the variation of the transport properties of ceria as a function of lattice strain. We also experimentally demonstrate the effects of migration direction with respect to the biaxially strained plane. Surprisingly, we find that the change in activation energy with strain is dependent on the size of the dopant cation. Combined with computational calculations of the same system, we show that the strain-modified conductivity is dependent both on the migration edge barrier and the defect-association. These findings give unique insights into the atomistic interaction of strain on the ionic transport of oxygen in substituted CeO2, and suggest that substantially improved conductivity in strained oxides may yet still be achieved if migration direction and defect association are optimised.
Authors : Andreas Nenning(1), Harald Summerer(1), Raffael Rameshan(2), Lorenz Lindenthal(2), Stefan Reuter(1), Richard Schlesinger(3), Tobias Huber(1), Christoph Rameshan(2), Jürgen Fleig(1), Alexander K. Opitz(1)
Affiliations : (1) TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria (2) TU Wien, Institute of Materials Chemistry, Getreidemarkt 9/165, 1060 Vienna, Austria (3) ETH Zürich, Deptartment of Information Technology and Electrical Engineering, Physikerstrasse 3, CH-8092 Zürich
Resume : The performance of mixed conducting porous SOC electrodes depends on the concentration and mobility of electronic and ionic defects in the bulk, as well as the surface structure and chemistry, which determines the reactivity for oxygen exchange reactions. The simultaneous characterization of SOC electrodes with electrochemical impedance spectroscopy (EIS) and ambient pressure XPS (APXPS) delivers detailed insight into the reaction mechanism. Since the bulk and surface defect chemistry vary with atmosphere and overpotential of the investigated electrode, precise knowledge of these parameters is an important, but highly non-trivial experimental requirement, especially when the investigated electrode is porous and thus has a low polarization resistance. Therefore, combined EIS and APXPS studies were so far mostly performed on model cells with thin film electrodes. In the presented study we use a novel three electrode solid oxide cell design with three porous electrodes. This allows precise control of half-cell overpotentials and measurement of virtually artefact free half-cell impedance spectra in an APXPS chamber. We exemplify the strength of this design on porous La0.6Sr0.4FeO3 (LSF) electrodes. Equivalent circuit fitting of the half-cell impedance spectra reveals defect chemistry, surface reactivity and ion conductivity of the LSF phase, also when a DC bias is applied. Another important aspect of the cell design is the current collecting layer of the LSF electrode, which is realized in form a of a thin film Pt grid between electrode and electrolyte. Therefore, the LSF phase is accessible to ambient pressure XPS (APXPS) measurements at various bias and atmosphere conditions. The combination of these methods reveals a consistent picture about the relation of bulk and surface defect chemistry, mixed ion/electron conduction and redox kinetics. Specifically, we can show that in oxidizing atmosphere, overpotential drastically changes concentration of oxygen vacancies in LSF. By impedance fitting with a transmission line type equivalent circuit we find an according bias dependence of the ionic conductivity and chemical capacitance. Since oxygen vacancies are not directly detectable by APXPS, the surface chemistry depends only moderately on the overpotential. In reducing (H2+H2O) atmosphere, the vacancy concentration is high, irrespective of the applied overpotential. Still, the I-V curve is strongly asymmetric and much steeper in electrolysis direction. There, the overpotential has a strong effect on the oxidation states of Fe. We find Fe3+, Fe2+ and Fe0 states, depending on the overpotential. When cathodic bias is applied, metallic iron is present in form of exsolved nanoparticles, which explain the excellent H2O electrolysis kinetics. Therefore we deliver direct proof that Fe exsolutions strongly accelerate the water splitting kinetics also on porous electrodes.
Authors : A. R. Genreith-Schriever
Affiliations : Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
Resume : Ion transport across grain boundaries in diverse polycrystalline ionic conductors is often found to be hindered. Such behaviour is commonly attributed to the presence of a highly resistive second phase or to the presence of space‐charge zones, in which mobile charge carriers are strongly depleted. One other possible cause – the severe perturbation of the crystal structure within the grain‐boundary core – is widely ignored. Employing molecular dynamics (MD) simulations of the model Σ5(310) grain boundary in fluorite‐structured ceria, we demonstrate an approach to extract the intrinsic structural resistance of a grain boundary (to ionic transport across it), and we determine this excess resistance as a function of temperature. Compared with space‐charge resistances predicted for a dilute solution of charge carriers the structural resistance of this interface is orders of magnitude smaller at temperatures below T≈1000 K but at T>1200 K it is no longer negligible.
|12:30||OPEN DISCUSSION SESSION|
New Phenomena and Devices : TBC
Authors : Vincenzo Esposito
Affiliations : Department of Energy Conversion and Storage, Technical University of Denmark (DTU), Kgs. Lyngby 2800, Denmark
Resume : Highly oxygen defective ionic metal oxides fluorites such, as ceria and bismuth oxides, are sustainable, non-classical electrostrictors with properties that are superior to lead-based piezoelectric metal oxides. Here, we report recent findings underlying the exceptional electromechanical performances of such materials, both as bulk ceramics and thin films. We especially highlight the effect of dopants, microstructure, and crystallography on low-temperature actuation. We also show how the materials perform in the nanoscale and how these impact micro/nano-electromechanical system´s design and some related technologies.
Authors : Evgeniy Makagon, Ellen Wachtel, Lothar Houben, Sidney R. Cohen, Yuanyuan Li, Junying Li, Anatoly Frenkel, Igor Lubomirsky
Affiliations : Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel; Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel; Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, USA;
Resume : The chemo-mechanical effect in solids refers to dimensional change due to change in stoichiometry. Dimensional change due to electrochemically-induced compositional change has been termed the electro-chemo-mechanical (ECM) effect. The mechanical instability inherent in this effect is clearly deleterious for batteries or fuel cells, but, as recently suggested, has potential for use in actuation. The structure of an actuator device that operates on the ECM principle comprises a micrometer thick solid electrolyte (SE) sandwiched between two ECM-active, working body (WB) layers. An electrochemical reaction must occur in these layers, causing them to alternately expand or contract. In order to facilitate the ECM response, the WB layers should have mixed ionic and electronic conductivity and a large chemical expansion coefficient. We have constructed a 2mm diameter thin film membrane ECM actuator device comprising 20mol% Gd doped CeO2 (20GDC) as the SE and [TiO(2-δ)\20GDC] or [V2O(5-δ)\20GDC] composites as the WBs. Selected area electron diffraction measurements showed the composite to be nanocrystalline, a morphology that promotes interfacial oxygen ion diffusion. Synchrotron X-ray absorption (XAS) measurements detected a mixture of Ce3+/Ce4+ (~[0.4]/[0.6]) and Ti3+/Ti4+ (~[0.1]/[0.9]) oxidation states in the WB. XAS measurements under bias showed changes in the short-range order of Ti and V oxides supporting the presence of a redox reaction. The deformation of the ECM actuator was observed to be in the bending regime producing large vertical displacements (~3 μm) and ~4 MPa stress. The stress/voltage ratio yields a pseudo piezoelectric stress coefficient of e31=1.26 C/m2, comparable to common lead-free piezoelectrics such as lithium niobate, lithium tantalate and alkali niobates.  J. G. Swallow et al., Nat. Mater. (2017) 16, 749  E. Makagon et al. Adv. Funct. Mater. (2020), 2006712.
Authors : Sofia De Sousa Coutinho(1), Stéphane Holé(1), David Bérardan(2) , Nita Dragoe (2) and Brigitte Leridon(1)
Affiliations : (1) LPEM, ESPCI Paris, CNRS, Université PSL, Sorbonne Universités, 10 rue Vauquelin, 75005 Paris, France (2) ICMMO, Univ. Paris-Sud, Univ. Paris-Saclay, F-91405, Orsay, France
Resume : A recently discovered family of superionic conductors exhibits colossal equivalent permittivity when the material is placed between two metallic electrodes. This is remarkable because ionic conductors with comparable ionic conductivity usually do not exhibit such huge permittivity. As a matter of fact, these titanium-based lamellar perovskites of general formula M2Ti2O5 where M=Rb,K… are also found to exhibit memristive properties. Systematic measurements have allowed us to track the behavior of the permittivity as function of frequency and temperature in both the Rb and K compounds. We evidenced a maximum in the real equivalent permittivity at around 270 K for the Rb-compound and at 300K for the K-compound, together with Warburg diffusion at low frequency. The variation of the permittivity is correlated to the variation of the ionic conduction, thus pointing to a common origin for both phenomena. We will present here different investigations on the nature of the conducting ions. In particular by measuring the charge distribution inside the sample, we were able to demonstrate that the ions accumulating at the anode are of negative sign and that the material becomes locally conducting on the cathode side, creating a virtuel cathode, which accounts for all observed features. We will then present our latest results and conclusions on the nature of the migrating ions and we will discuss possible applications for this material.
Authors : Grieshammer, S.*(1), Murch, G.(2).
Affiliations : (1) Institute of Physical Chemistry, RWTH Aachen University, Germany (2) School of Engineering, University of Newcastle, Australia
Resume : Cerium oxide is a versatilely applicable ceramic, e.g. as high temperature coating material. Doped with trivalent oxides, such as gadolinium oxide, the material shows high oxygen ion conductivity exceeding that of commonly applied yttria-stabilized zirconia. In this study, we estimate thermal conductivity of pure and doped cerium oxide by equilibrium molecular dynamics simulations based on widely applied empirical pair potentials and making use of the Green–Kubo formalism. The simulations show the limitations of most of the present potentials to correctly describe the thermal expansion and thermal conductivity. Based on our results we apply the Green–Kubo formalism for Gd-doped ceria to obtain thermal and ionic conductivity. The simulations do not only yield the diagonal Onsager phenomenological coefficients but also the off-diagonal coefficients. In this way it is possible to describe the coupling between mass and heat transport, which also known as thermodiffusion or the Soret-effect.
Authors : Sebastian Steiner, Leonie Koch, An-Phuc Hoang, Max Gehringer, Karsten Albe, Till Frömling
Affiliations : Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Strasse 2, Darmstadt, Germany, 64287
Resume : Sodium bismuth titanate (NBT) based ceramics are excellent lead-free ferroelectrics and relaxor materials. The defect chemistry of these materials is, however, very complex. NBT can actually be modified from highly ionically conductive to highly resistive. For example, acceptor doping does not lead to the hardening of ferroelectric properties as it was initially expected. Instead, mobile oxygen vacancies are induced making the material an excellent oxygen ion conductor . This behavior is very interesting from a research perspective but it may be very detrimental for the transfer of NBT-ferroelectrics into application. Aging and fatigue models from other well-known ferroelectrics might not be applicable. Thus, a detailed understanding of the defect chemistry of NBT and its solid solutions is of high importance. We developed a model to elucidate the defect chemistry of NBT-ceramics . Furthermore, methods to control the ionic conductivity, ferroelectric properties and the microstructure will be discussed in this work . This will illustrate the extraordinary opportunities to alter properties of NBT-based material for multiple applications. 1. Li, M., et al., A family of oxide ion conductors based on the ferroelectric perovskite NBT. Nature Materials, 2014. 13(1): p. 31-35. 2. Koch, L., et al., Ionic conductivity of acceptor doped sodium bismuth titanate: influence of dopants, phase transitions and defect associates. Journal of Materials Chemistry C, 2017. 5(35): p. 8958-8965. 3. Steiner, S., et al., The effect of Fe-acceptor doping on the electrical properties of NBT and 0.94 NBT–0.06 BT. Journal of the American Ceramic Society, 2019. 102(9): p. 5295-5304.
Authors : Ya-Ru Wang, Gee Yeong Kim, Alessandro Senocrate, Davide Moia and Joachim Maier
Affiliations : Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany
Resume : Since the discovery of anomalous polarization phenomena in solar cells based on organic-inorganic hybrid perovskites, much attention has been devoted to the mixed ionic-electronic conducting properties of these materials.1, 2 Strikingly, investigation of mixed conduction in methylammonium lead iodide under light showed – along with the expected increase in electronic conductivity – huge enhancement of ionic conductivity.3 As mixed anion perovskites show greatest potential for achieving high-efficiency solar cells, understanding the role of anion composition on this “photo-ionic effect” is of utmost importance. In this contribution, we quantify the ionic and electronic conductivities for thin films of iodide, bromide as well as of mixed halide perovskites in devices with ion blocking electrodes. Compared with the iodide-based counterparts, bromide-based perovskites experience less enhancement of ionic conductivity. 3, 4 This corroborates the self-trapped hole model for the photo-induced ion transport owing to the fact that Br is less polarizable than the counterpart of I.5 On the basis of these observations, we propose a model explaining the photo-demixing in mixed halide perovskites where the formation of neutral iodine interstitial defects stabilizes the coexistence of I-rich and Br-rich domains. The connection between the photo-effect on iodide-based perovskites and the driving force for demixing3 represents a novel contribution to the thermodynamics of phase segregation and emphasizes the importance of the coupling between electronic and ionic defects in the phase behavior of halide perovskites. 1. T. Y. Yang, G. Gregori, N. Pellet, M. Gratzel and J. Maier, Angew Chem Int Ed Engl, 2015, 54, 7905-7910. 2. A. Senocrate, I. Moudrakovski, G. Y. Kim, T. Y. Yang, G. Gregori, M. Gratzel and J. Maier, Angew Chem Int Ed 2017, 56, 7755-7759. 3. G. Y. Kim, A. Senocrate, T.-Y. Yang, G. Gregori, M. Grätzel and J. Maier, Nature materials, 2018, 17, 445-449. 4. G. Y. Kim, A. Senocrate, Y.-R. Wang, D. Moia and J. Maier, Angewandte Chemie International Edition, 2021, 60, 820-826. 5. R. A. Evarestov, E. A. Kotomin, A. Senocrate, R. K. Kremer and J. Maier, Phys Chem Chem Phys, 2020, 22, 3914-3920.
|15:45||OPEN DISCUSSION SESSION|
Solid State Energy Devices (VI): Batteries : TBC
Authors : Hyeon Jeong Lee and Mauro Pasta
Affiliations : University of Oxford
Resume : Solid-state Li-ion conductors have received a great deal of attention in recent years due to their potential advantages compared to commercial liquid electrolytes, namely the improved safety and higher energy densities achievable through the implementation of Li-metal anodes. Unfortunately, despite their superior mechanical properties, solid state batteries are afflicted by the same short-circuiting challenges that affect their liquid electrolyte counterparts, a phenomenon broadly described as lithium “dendrites”. A fundamental, concerted understanding of the effects of mechanical, ionic and electronic transport and interfacial properties of solid electrolytes on dendrite formation and penetration is necessary to guide the development of the solid electrolytes of the future. Anti-perovskites of the Li2OHX family (X= Cl, Br) are an interesting class of Li-ion conductors with tunable properties and a low melting point that could represent an ideal model solid electrolyte system for this thorough investigation. In my talk, I will discuss the progress we have made and future steps.
Authors : Roman Zettl (1), Sarah Lunghammer (1), Bernhard Gadermaier (1), Athmane Boulaoued (2), Patrik Johansson (2,3), H. Martin R. Wilkening (1,3), Ilie Hanzu (1,3)
Affiliations : (1) Institute of Chemistry and Technology of Materials, Graz University of Technology (NAWI Graz), Stremayrgasse 9, 8010 Graz, Austria (2) Department of Physics, Chalmers University of Technology, 412 96, Gothenburg, Sweden (3) Alistore−ERI European Research Institute, CNRS FR3104, Hub de l’Energie, Rue Baudelocque, F-80039 Amiens, France
Resume : Solid-state electrolytes for battery systems is a fast developing field. Here, we focus on a new class of solid-state electrolytes based on metal organic frameworks (MOFs). An endless number of linkers and metal centres can be used to build a tremendous variety of different MOFs with tunable properties. MOFs are interesting materials to investigate as solid-state electrolytes as they are thermally stable and highly porous. In this study MIL-121 (Al centres linked by pyromellitic acid) was synthesized by a hydrothermal route  and post synthetically modified with lithium acetate and sodium acetate. After this lithiation and sodiation step samples were soaked with LiClO4 or NaClO4 in propylene carbonate in order to increase the ion content even further. X-ray powder diffraction (XRD) revealed that the structure of pristine MIL-121 could be largely maintained after lithiation or sodiation together with a small loss in crystallinity. At 303 K a conductivity of 4.6 ∙ 10−6 S/cm−1 for Li ions and 1.2 ∙ 10−4 S/cm−1 for Na ions was measured. This is in line with previous studies on MOFs as solid-state electrolytes. Interestingly, activation energies were different at higher and lower temperatures. The kink in the Arrhenius curve could not be assigned to structural changes or phase transitions. Hence, the observed non-Arrhenius behaviour was attributed to a change from correlated to uncorrelated motion as suggested in the model of Ngai. Low activation energies of 0.28 eV (above 323 K) and 0.36 eV (above 283 K) for Li and Na, respectively, were found in the higher temperature region. 7Li NMR spectroscopy confirmed the mobility of both ions and showed the vital role of the soaking electrolyte. Line shapes and spin-lattice relaxation (SLR) NMR suggested two different conduction processes: one can likely be ascribed to ions forming stronger bonds with carboxylic groups whereas the other one corresponds to weaker-bonded solvated mobile ions in MOF pores. 1H SLR NMR measurements revealed that indeed the alkali metal ion is the moving species in the material. A correlation between the alkali metal ion and hydrogen might, however, play a major role in the diffusion process at lower temperatures. The successful modifications (lithiation, sodiation) of MIL-121 lead to encouraging conductivities and proved the potential suitability in batteries of this young class of solid-state ion conductors.  C. W. Sun, J. Liu, Y. D. Gong, D. P. Wilkinson, J. J. Zhang, Nano Energy 2017, 33, 363-386.  C. Volkringer, T. Loiseau, N. Guillou, G. Ferey, M. Haouas, F. Taulelle, E. Elkaim, N. Stock, Inorg Chem 2010, 49, 9852-9862.  a) R. Ameloot, M. Aubrey, B. M. Wiers, A. P. Gomora-Figueroa, S. N. Patel, N. P. Balsara, J. R. Long, Chem-Eur J 2013, 19, 5533-5536; b) B. M. Wiers, M. L. Foo, N. P. Balsara, J. R. Long, J Am Chem Soc 2011, 133, 14522-14525.  a) K. L. Ngai, A. K. Jonscher, C. T. White, Nature 1979, 277, 185-189; b) K. L. Ngai, C. T. White, Phys Rev B 1979, 20, 2475-2486.
Authors : Ieuan D. Seymour* (1), Nicholas S. Grundish (2), Yutao Li (2), John B. Goodenough (2) and Graeme Henkelman (1)
Affiliations : (1) Department of Chemistry and the Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712, United States (2) Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA
Resume : Layered transition-metal (TM) oxides have played a central role as cathodes for Li-ion and Na-ion rechargeable batteries. Alleviating the deleterious structural transitions that occur in these materials during electrochemical cycling is still a critical challenge which requires a fundamental understanding of the mechanisms taking place at the atomistic level. In this work we investigated how Te6 doping into the AxNiO2 (A=Li and Na) family of materials leads to changes in the local structure and electrochemical performance. The Li-Ni-Te-O system provides a rich phase space in which two layered polymorphs and one disordered rock salt phase can be synthesised. Significant Ni2 migration occurs in both layered polymorphs which leads to rapid capacity fading. The disordered rock salt structure displayed the highest reversible capacity out of the three polymorphs, which could be rationalised based on the presence of fast Li-transport on the partially ordered Li/Ni sublattice. In the Na-Ni-Te-O system, the inclusion of Te6 results in the suppression of TM layer shearing during desodiation. Using a combination of X-ray diffraction, solid-state NMR and DFT calculations it can be shown that the improvement of the electrochemical cycling is related to the inclusion of Na ions into the TM layer which suppresses Na-ordering. The conclusions from this work have wider implications for the design of new Li-ion and Na-ion cathode materials.  Grundish et al. Chem. Mater. 31 (2019).
|17:15||OPEN DISCUSSION SESSION|
|17:30||CLOSING AND AWARDS|
Department of Materials - Sw7 2AZ London - U.K.+44(0)20 7594 5174
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