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2019 Fall Meeting



Beyond hydrogen storage – Metal hydrides as multifunctional materials for energy storage and conversion

Metal hydrides are of special interest for a diverse range of applications e.g. electrochemical, hydrogen, and thermal energy storage materials. The goal is to provide energy storage solutions for the intermittent renewable but sustainable energy production pathway for future generations.


The urgent need for energy storage materials for a sustainable and carbon-free society is the main stimulant for the new dawn in the development of metal hydrides in batteries, hydrogen storage materials and thermal energy storage. One application is batteries based on metal hydrides with alternative cations including Na+ and Mg2+, which are considered as cheaper, and more abundant, while potentially higher energy density compared to Li-ion batteries are achievable. Another application is to address the intermittent supply from renewable energy sources with a hydrogen-fuel cell system to provide an uninterrupted sustainable supply of energy for stationary systems and benign zero-emission vehicles, with clean water as the only reaction by-product. Renewable energy combined with efficient ways of energy storage will be a key enabler to future technologies. Metal hydrides clearly offer an attractive and versatile platform of materials, which encompass a broad array of structures and combine interesting and tuneable properties useful for a breadth of energy applications spanning from solid-state hydrogen storage, to solid-state ion conductors for batteries or fuel cells and thermal energy storage. The proposed symposium aspires to bring together ambitious young and established scientists from around the world to not only present the latest advances of the intense worldwide research but also exchange ideas as well as identify major challenges and hot-topics for future developments towards efficient solutions for energy applications.

Hydride materials display a broad range of chemical, structural and physical features. This diversity in turn yields an unrivalled breadth and scope of possible applications, particularly with the advent of nano-technological development. As such, the talks given by enthusiastic-young and world-leading researchers in this symposium are bound to captivate a wide audience. 

Hot topics to be covered by the symposium

  • Fundamental hydride structures, reaction mechanisms and thermodynamics
  • Fundamental aspects of solid state ion conductors
  • Hydrides for battery electrodes and energy conversion
  • Hydrides for solar thermal energy storage
  • Hydrogen storage material development
  • Computational methods for hydride materials
  • Design and application of hydride based systems
  • Towards application: sensors, batteries and engineering challenges
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Fundamental aspects of solid state ion conductors I : Michel Latroche
Authors : Wolfgang Zeier
Affiliations : Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen, Germany.

Resume : The advent of solid-state batteries has spawned a recent increase in interest in lithium conducting solid electrolytes, especially in the lithium thiophosphates. While current lithium electrolytes provide fast-ionic conduction to fundamentally study solid-state batteries, their ionic conductivities are not sufficient for thick electrode configurations, which will really allow high energy densities to be achieved.1 In this presentation, we show how an understanding of the structure-transport properties of the lithium argyrodites Li6PS5X can help tailor the ionic conductivity. We show that an anion site-disorder between S2- and X- is beneficial for the activation barrier2 and that an induction of the site disorder in Li6PS5I leads to a significant improvement of the conductivity.3 Further, we will show how tuning the lattice polarizability in ionic conductors affects the ionic transport due to a softening of the lattice. Our work shows that the idea of “the softer, the better” needs to be revisited.2,4,5 Lastly, we show how volume changes, induced by electrochemical (de-)intercalation, affect the performance in solid state batteries providing an understanding of the underlying mechanochemical influences in solid-state batteries.6,7 (1) Janek, J.; Zeier, W. G. A Solid Future for Battery Development. Nat. Energy 2016, 16141. (2) Kraft, M. A.; Culver, S. P.; Calderon, M.; Böcher, F.; Krauskopf, T.; Senyshyn, A.; Dietrich, C.; Zevalkink, A.; Janek, J.; Zeier, W. G. Influence of Lattice Polarizability on the Ionic Conductivity in the Lithium Superionic Argyrodites Li6PS5X (X = Cl, Br, I). J. Am. Chem. Soc. 2017, 139, 10909–10918. (3) Kraft, M. A.; Ohno, S.; Zinkevich, T.; Koerver, R.; Culver, S. P.; Senyshyn, A.; Indris, S.; Morgan, B. J.; Zeier, W. G. Inducing High Ionic Conductivity in the Lithium Superionic Argyrodites Li6 xP1-xGexS5I for All-Solid-State Batteries. J. Am. Chem. Soc. 2018, 140, 16330–16339. (4) Krauskopf, T.; Muy, S.; Culver, S. P.; Ohno, S.; Delaire, O.; Shao-Horn, Y.; Zeier, W. G. Comparing the Descriptors for Investigating the Influence of Lattice Dynamics on Ionic Transport Using the Superionic Conductor Na3PS4-XSex. J. Am. Chem. Soc. 2018, 140, 14464–14473. (5) Krauskopf, T.; Pompe, C.; Kraft, M.; Zeier, W. G. Influence of Lattice Dynamics on Na -Transport in the Solid Electrolyte Na3PS4−xSex. Chem. Mater. 2017, 29, 8859–8869. (6) Zhang, W.; Schröder, D.; Arlt, T.; Manke, I.; Koerver, R.; Pinedo, R.; Weber, D. A.; Sann, J.; Zeier, W. G.; Janek, J. (Electro)Chemical Expansion during Cycling: Monitoring the Pressure Changes in Operating Solid-State Lithium Batteries. J. Mater. Chem. A 2017, 5, 9929–9936. (7) Koerver, R.; Zhang, W.; de Biasi, L.; Schweidler, S.; Kondrakov, A.; Kolling, S.; Brezesinski, T.; Hartmann, P.; Zeier, W.; Janek, J. Chemo-Mechanical Expansion of Lithium Electrode Materials – On the Route to Mechanically Optimized All-Solid-State Batteries. Energy Environ. Sci. 2018, 11, 2142–2158.

Authors : Brandon C. Wood, ShinYoung Kang, Patrick Shea, Kyoung Kweon, Joel Varley, Tae Wook Heo
Affiliations : Lawrence Livermore National Laboratory, USA

Resume : Metal borohydrides have long been considered as promising candidates for solid-state hydrogen storage, due to the intrinsically high capacity and attractive thermodynamics of several of the variants. Recently, similar compounds have been investigated for use as electrolytes in solid-state batteries due to their unusually high ionic conductivity. Within these materials, the BxHy anions can exhibit complex reorientation dynamics at elevated temperatures that can affect thermodynamic and kinetic properties. To better understand the anion dynamics, we have been investigating the finite-temperature properties of Mg, Li, and Na compounds with BH4-, B12H122-, and B10H102- anions using extensive ab initio molecular dynamics simulations. Our simulations reveal that anion reorientations are closely connected to hydrogen and cation mobility in these materials. I will show how superionic conductivity in Li and Na borohydrides is connected to intrinsic frustration between the BxHy molecular and lattice symmetries. I will also discuss our findings concerning the relationship between the anion rotations and entropy, which has profound implications for understanding and predicting the thermodynamics of hydrogen-storage reactions. The simulations reveal the importance of considering explicit finite-temperature properties in simulations of borohydrides, and suggest general strategies for improving their performance in solid-state batteries and hydrogen storage.

Authors : Petra de Jongh and Peter Ngene
Affiliations : Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands;;

Resume : A central goal in current battery research is to increase the safety and energy density of Li-ion batteries. Electrolytes nowadays typically consist of lithium salts dissolved in organic solvents. Solid electrolytes could facilitate safer batteries with higher capacities, as they are compatible with Li metal anodes, prevent Li dendrite formation and sulphur shuttling, and eliminate risks associated with flammable organic solvents. About 10 years ago, LiBH4 was proposed as a solid state electrolyte. It showed a high ionic conductivity, but only at elevated temperatures. Since then strategies have been developed to extend the high ionic conductivity of LiBH4 down to room temperature, and other light metal hydrides have been explored as solid electrolytes. Using LiBH4 as an example we will discuss how the properties of solid electrolytes can be modified by forming nanocomposites with metal oxides, leading to an enhancement of the room temperature ionic conductivity of more than three orders of magnitude. DSC measurements combined with solid state NMR allow to identify how the nanoconfinement and presence of interfaces modify the phase stability and the Li+ mobility. Systematic studies show how the ionic conductivity can be optimized by tuning the nanostructure and interfaces in these nanocomposites. Promising results have been obtained in using these materials as solid-state electrolytes in next generation all-solid state lithium-sulphur batteries. FInally we will highlight the latest developments on extending the strategy to other metal hydride compounds, and combining nanoconfinement and anion-substitution

13:00 Lunch break    
Fundamental aspects of solid state ion conductors II : Matteo Brighi
Authors : Dorthe B. Ravnsbæk
Affiliations : Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

Resume : The conversion between electrical and chemical energy inside a battery inherently leads to both chemical and structural transformation in the functional battery materials, i.e. the electrodes and electrolyte. Understanding these transformations in detail and over a wide range of length scales is of vital importance for practical applications as the reversibility and stability of these transformations determine the energy, power, and lifetime of the system. Moreover, to understand how the phase transformations, occur during battery operation, it is essential that these studies are carried out operando under dynamic electrochemical conditions. This talk will demonstrate how a combination of electrochemical analysis, ex situ and operando diffraction as well as total scattering can be utilized to elucidate reaction pathways during battery charge and discharge for a series of material systems and how this provide insight into the origins of capacity fade. Among other systems, we have investigated the conversion pathway and electrochemistry in an all-solid-state battery comprised of a Mg2FeH6 conversion type anode with LiBH4 as solid-state electrolyte. In the solid-state battery, Mg2FeH6 exhibits improvements in the capacity retention and initial Coulombic efficiency of> 3 and> 2.5 times, respectively, compared to the conventional liquid-electrolyte battery.1 [1] Priscilla Huen, Dorthe B. Ravnsbæk, Electrochemistry Communications 87 (2018) 81–85

Authors : Torben R. Jensen
Affiliations : iNANO and Department of Chemistry Langelandsgade 140 DK-8000 Aarhus C Aarhus University Denmark

Resume : Hydrogen is recognized as a potential and extremely interesting energy carrier [1,2], which can facilitate efficient utilization of unevenly distributed renewable energy. Furthermore, hydrogen has also an extremely interesting chemistry and form compounds with most elements in the periodic table and with a variety of different types of bonds [3]. Here we report on selected recent investigations of multi-functional hydrides utilised as battery materials and as potential hydrogen storage materials [4]. The variety of different boron-based anions provide new inspiration for rational materials design of ion conducting materials. In particular di-hydrogen bonds provides structural diversity and flexibility. Here we demonstrate the close connection between hydrogen storage and battery materials. References [1] Ley, et al, Mater. Today, 2014, 17(3), 122. [2] K. T. Møller, et al, Energies, 2017, 10(10), 1645; doi:10.3390/en10101645. [3] M. Paskevicius, Chem. Soc. Rev. 2017, 46, 1565 [4] M. Paskevicius, Nature Comm., 2017, 8, 15136, 1-6. DOI: 10.1038/ncomms15136

Authors : Junxian Zhang a; A. Lacoste b; N. Berti a; E. Hadjixenophontos c; F. Cuevas a; G. Schmitz c; M. Latroche a
Affiliations : a ICMPE (UMR7182), CNRS, UPEC, F-94320 Thiais, France b LPSC, Université Grenoble-Alpes, CNRS/IN2P3, 53 rue des Martyrs, 38026 Grenoble Cedex, France c Institut für Materialwissenschaft, Lehrstuhl Materialphysik (IMW), University of Stuttgart, Heisenbergastrasse 3, 70569 Stuttgart, Germany

Resume : Li-ion batteries are today largely used as energy storage systems for mobile electronics and electrical vehicles. However, insertion compounds that are currently used for this technology reach intrinsic limitations. Improved battery performances are expected from novel reaction schemes or new technologies, such as conversion reactions or metal-air batteries. In this context, Metal Hydrides (MH) have been proposed as potential candidates for negative electrode in Li-ion batteries. Several families of nanocristalline hydrides (MgH2, TiH2, Mg2TmHx, Tm = Fe, Co and Ni) have been synthetized by mechanochemistry of the elements under hydrogen gas. During electrochemical lithiation, all these hydrides fully react with lithium at low potentials (< 0.7 vs. Li+/Li°) and provide capacities over 1000 mAh/g. However, reversibility at room temperature of this conversion reaction is poor. To solve this issue, better understanding of the limiting mechanisms in these systems is required. In this context, we have recently focused our efforts on the study of MgH2 thin films as well-defined 2D systems [1]. MgH2 thin films were deposited on Cu current collectors by means of reactive plasma sputtering and Al-coated to minimize formation of passivating MgO native oxide layer. Their properties as negative electrodes have been investigated. Structural and chemical properties of the electrodes were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS). The influence of the thickness of MgH2 thin films on the reversibility will be discussed and interpretation of the limiting reaction mechanisms will be proposed. [1] N. Berti, E. Hadjixenophontos, F. Cuevas, J. Zhang, A. Lacoste, P. Dubot, G. Schmitz, M. Latroche, J. Power Sources, 402 (2018) 99-106.

Authors : M. B. Amdisen, T. R. Jensen
Affiliations : Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University

Resume : Utilizing renewable energy efficiently can be difficult as the energy production from most renewable energy sources is intermittent. Efficient use of renewable energy then depends on energy storage capabilities. One way to store energy is by the use of batteries. Not only can more efficient batteries help us reach some of the environmental goals set by the United Nations, but they can generally improve our daily lives. A wide variety of appliances in today’s society depend on batteries, including laptops, smartphones and multiple other mobile devices. The most common batteries used today are based on liquid electrolytes that consist of Li salts in organic solvents. These electrolytes can be corrosive and flammable and there is a nonnegligible risk of puncturing the outermost layers of batteries, exposing the electrolyte. In Li-ion batteries there is also a risk of dendrite formation, which can lead to self-perpetuating exothermic reactions ultimately resulting in the battery exploding. Designing a solid-state electrolyte that can compete with current electrolytes can resolve the safety issues related to the battery composition. Solid-state electrolytes are not corrosive, they do not leak, and less dendrite formation occurs, hence the desire to develop solid-state electrolytes that compare to and even surpass the ionic conductivity of current electrolytes. A lot of known solid materials display decent ionic conductivities and the versatility of borohydrides also encompasses such properties. In search of better, novel solid-state electrolytes the alkaline earth metals have captured attention as they carry twice the charge of alkali metals and Mg and Ca are more abundant than the most commonly used diffusive species, namely Li. This study is concerned with the ionic conductivities of Ca(BH4)2·nNH3 (n = 1, 1.5, 2). Preliminary results do not display promising ionic conductivities, but hopefully further studies, including characterization by solid-state nuclear magnetic resonance spectroscopy and neutron scattering, will provide insight into the possible ionic conductivity mechanism and contribute to future rational solid-state electrolyte design. L. H. Jepsen et al., ChemSusChem, 2015, 8, 3472–3482 H. Chu et al., Chem. Mater., 2010, 22, 6021–6028 B. R. S. Hansen et al., Coordination Chemistry Reviews, 2016, 323, 60–70

15:30 Coffee break    
Hydride-based [battery] materials : Hai-Wen Li
Authors : Léo Duchêne, Dong Hyeon Kim, Romain Moury, Ruben-Simon Kühnel, Arndt Remhof, Hans Hagemann, Yoon Seok Jung, Corsin Battaglia
Affiliations : Léo Duchêne; Arndt Remhof; Ruben-Simon Kühnel;Corsin Battaglia - Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland Léo Duchêne; Romain Moury; Hans Hagemann - Département de Chimie-Physique, Université de Genève, 1211 Geneva 4, Switzerland Dong Hyeon Kim; Yoon Seok Jung - Department of Energy Engineering, Hanyang University, 04763 Seoul, Republic of Korea

Resume : Na4(B12H12)(B10H10) is a promising solid electrolyte in the hydro-closo-borate family. Owing to the dynamics and stability of the closo-borate anions, it combines superionic Na+ conductivity at room temperature with high thermal and electrochemical stability including stability towards sodium metal.[1,2] Here, we discuss the implementation of this solid electrolyte in all-solid-state batteries following two approaches. First, we use dry powder stacking and compacting of the electrolyte and a NaCrO2 cathode composite, and using a sodium metal foil as the anode.[3] We show that the solution impregnation of the solid electrolyte onto the cathode particles is instrumental to achieve high cycling stability of the battery at 60 °C (85% capacity retention after 250 cycles at C/5). Second, we extend this approach and discuss the solution infiltration of Na4(B12H12)(B10H10) into porous sheet-type electrode prepared by a conventional slurry process.[4,5] Using this approach, room temperature cycling with remarkable stability is achieved. We also demonstrate the first full cell using a closo-borate electrolyte with capacity balanced electrodes. [1] L. Duchêne et al., Chem. Commun., 53, 4195 (2017). [2] L. Duchêne et al., Chem. Mat., 31, 3449, (2019). [3] L. Duchêne et al., Energy Environ. Sci., 10, 2609 (2017). [4] D. H. Kim et al., Nano Lett., 17, 3013 (2017). [5] L. Duchêne et al., submitted

Authors : Ronan LE RUYET (ad), Romain BERTHELOT (bd), Elodie SALAGER (cd), Pierre FLORIAN (c), Benoît FLEUTOT (ad), Raphaël JANOT (ad)
Affiliations : a Laboratoire de Réactivité et Chimie des Solides (LRCS), Université de Picardie Jules Verne, UMR 7314 CNRS, Amiens 80039, France; b Institut Charles Gerhardt Montpellier (ICGM), Université de Montpellier, UMR 5253 CNRS, Montpellier 34095, France; c Conditions extrêmes et Matériaux : Haute Température et Irradiation (CEMHTI), UPR 3079 CNRS, Université d’Orléans, Orléans 45071, France; d Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR 3459 CNRS, Amiens 80039, France.

Resume : Rechargeable Mg batteries could become a serious alternative to Li-ion batteries thanks to the possibility to reach higher volumetric energy density. Yet, their development is hindered by the difficulty to find non-corrosive and stable liquid electrolytes. Our work is focused on the identification of solid electrolytes that could tackle this issue. The first targeted material was Mg(BH4)(NH2) due to its good Mg2+ ionic conductivity. Its synthesis parameters were investigated and a conductivity of 3x10-6 at 100°C was obtained.[1] This conductivity is three orders of magnitude higher than the one previously reported.[2] To understand this result, powder X-ray diffraction was coupled for the first time with 11B solid state MAS-NMR spectroscopy to study this material. The results present the signature of crystalline Mg(BH4)(NH2) and an amorphous additional phase was also observed by NMR. The presence of this amorphous phase, considered as a Mg(BH4)x(NH2)2-x compound, leads to a composite material with enhanced Mg2+ ionic conductivity. Following, to investigate the existence of other Mg(BH4)x(NH2)2-x phases, the Mg(BH4)2-Mg(NH2)2 binary system has been studied. Syntheses with different stoichiometries were performed and resulted in the identification of unreported crystalline phases. Interestingly, all of these new phases feature Mg2+ ionic conduction. One of them is attractive in terms of ionic conductivity and thermal stability (no thermal phenomena detected neither by DSC nor TGA below 190°C). Indeed, its ionic conductivity measured by AC impedance spectroscopy was 2x10-5 at 100°C. This is one of the highest measured values for a Mg2+ inorganic solid-state conductor at such low temperature. The good mobility of the Mg2+ ions in this phase was confirmed by 25Mg solid state MAS-NMR spectroscopy.[3] Therefore, the different new Mg(BH4)x(NH2)2-x crystalline phases will be presented emphasizing the relationship between compositions, structures and transport properties. Additionally, tests were performed to evaluate the electrochemical stability of these new possible solid electrolyte materials. References : [1] R. Le Ruyet, R. Berthelot, E. Salager, P. Florian, B. Fleutot, R. Janot. Investigation of Mg(BH4)(NH2) Based Composite Materials with Enhanced Mg2+ Ionic Conductivity. J. Phys. Chem. C, 2019, 123, 10756−10763. [2] S. Higashi, K. Miwa, M. Aoki, K. Takechi. A novel inorganic solid state ion conductor for rechargeable Mg batteries. Chem. Commun. Chem. Commun, 2014, 50, 1320–1322. [3] R. Le Ruyet, R. Berthelot, E. Salager, P. Florian, B. Fleutot, R. Janot. In preparation.

Authors : Magda P?ska1*, Julita Dworecka-Wójcik1, Marek Pola?ski1
Affiliations : 1Department of Advanced Materials and Technologies, Military University of Technology, Kaliskiego 2 St., 00-908 Warsaw, Poland

Resume : AB5 type alloys are one of the most commonly used hydrogen storage alloys, mainly due to their ability to work at pressure and temperature close to atmospheric conditions. This material group includes LaNi5 alloy, which is characterized by hydrogen capacity of 1.4% but those alloys have often been subjected to modifications to improve the kintetics of the absorption / desorption process, cyclic stability, activation and equilibrium pressures at room temperature. For this purpose the La or Ni atoms were replaced or partially replaced by other elements like La, Ce, Pr and Nd. In this work, the substitution of lanthanum atoms with cerium atoms was performed. Five alloys of different chemical compositions were obtained. Synthesized alloys were characterized in terms of unit cell volume, equilibrium absorption and desorption pressures and hardness. Obtained results were correlated with chemical compositionand chemical composition distribution within the particles. Obtained data proved that cerium substitution changes the properties of material significantly. Pressure ? composition isotherms were collected, and basing on them, enthalpies of absorption and desorption of hydrogen were calculated.

Authors : D. Mirabile Gattia1*, M.Jangir1,2, IP Jain2
Affiliations : 1 Department for Sustainability, ENEA, Via Anguillarese 301, 00123 Rome, Italy; 2 Centre for Non-Conventional Energy Resources, University of Rajasthan, Jaipur, India * corresponding author:

Resume : Energy storage is one of the main challenges to be faced out in the near future due to extensive installation of renewable energy production plants. In particular the peaks of energy production deriving from the use of these intrinsically intermittent energy sources could cause grid destabilization. For this reason energy storage will represent a critical issue. Among other energy storage systems, the use of hydrides present some positive aspects. In these systems hydrogen and thermal energy both are involved considering that absorption and desorption reactions are generally strongly exothermic and endothermic respectively. It has to be considered also their potential use for waste heat recovery. Moreover further research on hydrides as materials for batteries has to be carried out as they demonstrated in some cases to be suitable for this application. In this scenario, the realization of large reactors containing hydrides considers to use material in the form of compacted powders in order to avoid detrimental effects of loose powder. In this work Magnesium hydride has been ball milled in presence of catalysts, in particular Fe and its oxides, and successively compacted under an uniaxial press. The materials have been cycled in a Sievert’s type apparatus at 310°C and 8 bar, for studying kinetics and stability to cycling, Scanning electron Microscopy, in order to investigate their microstructure and failure phenomena, X-Ray diffraction, for crystalline phases identification and Differential Scanning Calorimetry, for evaluating the effect of the catalyst toward onset and peak temperature during desorption. The pellets demonstrated suitable stability to cycling in terms of total hydrogen storage capacity and kinetics.

Authors : R. Martínez-Casado1, M. García-Carrión1, J. García-Fernández2, A. Torres-Pardo2, J. Ramírez-Castellanos2, E. Nogales1, J.M. González-Calbet2 and B. Méndez1
Affiliations : 1 Department of Physics of Materials, Faculty of Physical Sciences, University Complutense Madrid, 28040, Madrid, Spain 2 Department of Inorganic Chemistry, Faculty of Chemical Sciences, University Complutense Madrid, 28040, Madrid, Spain

Resume : Beta-gallia-rutile (BGR) intergrowths are interesting materials because of their 1-D tunnels, which are suitable hosts for cations. This type of structure is often found in materials for electrochemical devices such as batteries, fuel cells, and sensors. The theoretical analysis of the sodium titanogallate (Na-Ti-Ga-O) compounds, corresponding to three terms of the BGR series n = 5, 6 and 7 has been assisted by the use of ab initio calculations of the structure. The oxides; represent a challenge for standard implementations of Density Functional Theory (DFT). Generalized gradient approximations (GGA) functionals often underestimate the band gap, but the use of hybrid exchange functionals provides a qualitatively correct description of the structure, energetics and electronic properties for many different materials, and in particular, for oxides [1]. The method adopted here is DFT using the screened hybrid exchange functional HSE. The HSE functional has the advantage that, partially corrects for electronic self-interaction and so yields qualitatively correct fundamental band gaps in wide band gap semiconductors [2,3]. The structure of the three terms of sodium gallium titanate have been characterized from an experimental and theoretical point of view for the first time. DFT calculations confirms the band gap obtained experimentally. [1] A. V. Krakau, O. A. Vydrov, A.F. Izmaylov, and G.E. Scuseria. J. Chem. Phys. 2006, 125, 224106. [2] B. G. Janesko, T.M. Henderson, G.E. Scuseria. Phys. Chem. Chem. Phys. 2009, 11, 443. [3] P. Pernot, B. Civalleri, D. Presti, A. Savin. J. Chem. Phys. A 2015, 119, 5288

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Hydrides for Solar Thermal Energy Storage : Torben R. Jensen
Authors : Claudio Corgnale(1), Shaun Sullivan(2), Ragaiy Zidan(3), Bruce Hardy(3), Theodore Motyka(1)
Affiliations : (1) Greenway Energy (2) Brayton Energy (3) Savannah River National Laboratory

Resume : Solar driven plants can produce electric power efficiently and at low cost only if equipped with suitable thermal energy storage systems. Thermal energy storage systems based on metal hydrides have several advantages over other systems comprised of molten salt or phase change materials, namely low costs, high exergetic efficiencies and high volumetric energy densities [1]. A recent techno-economic analysis demonstrated that some of the high temperature metal hydrides have the potential to closely approach the US Department Of Energy (DOE) SunShot program targets for thermal energy storage [1]. For solar driven steam power plants, one of the most promising and appealing metal hydrides, working at temperatures of about 400-500 °C, is Mg2FeH6. A system comprised of Mg-Fe material, coupled with a suitable inexpensive low temperature hydride, represents a very promising economic energy storage concept. Results of modeling analysis of the proposed concept will be shown and discussed, demonstrating the technical feasibility of the proposed concept under several operating conditions and scenarios. A new project within the DOE SunShot program is aiming to demonstrate a prototype integrated solar receiver-thermal energy storage system for a high temperature s-CO2 solar driven power plant. The overall system is comprised of a novel Ca-based metal hydride material, coupled with a novel solar receiver concept. The initial outcomes of the novel prototype tests will be shown and discussed. Results of a detailed techno-economic performance analysis of the system, operating at large scale, will also be presented and discussed. [1] Corgnale C, et al. Renewable and Sustainable Energy Reviews 38(2014)821-833

Authors : Sabrina Sartori
Affiliations : University of Oslo, Department of Technology Systems, Norway

Resume : Solid state hydrogen storage in metal hydrides is a promising form of energy storage for stationary energy storage. TiFe alloy is a promising candidate because of its low price, reasonable storage capacity, low operation temperature and good reversibility. However, the first hydrogenation (activation) of TiFe alloy is usually difficult. In order to overcome this problem, different approaches have been investigated, among them the element substitution for Fe or Ti with transition metals (TMs), including Mn, Cr, Ni and Zr. In this talk we will present the effect of mechanochemistry (ball milling and cryomilling) on TiFeZr-type alloys with respect to their hydrogenation properties, their microstructure and element distribution. Ball milling and cryomilling showed a completely different behavior in respect to hydrogenation. Ball milling improved the initial kinetics of processed powders compared with the as-cast sample but reduced the H-storage capacity. The faster kinetics is likely due to the reduction of the crystallite sizes and formation of new grain boundaries. The reduced hydrogen storage capacity may be explained by the formation of grain boundaries that enhance the hydrogen diffusion but do not store hydrogen in their structures. Following measurements at ESCA microscopy beamline (Elettra), we found phase separations which are more pronounced during hydrogenation. This indicates that the variation of composition at the interface matrix/secondary phase may play an important role in the transfer of hydrogen from the secondary phase to the matrix.

Authors : Inga Bürger, Mila Kölbig, Christoph Weckerle, Marc Linder
Affiliations : German Aerospace Center

Resume : Metal hydrides are perfectly suitable for high thermal power devices as they show two important properties: high rates of reactions even at temperatures well below 0 °C and high enthalpies of reaction with values of 20-30 kJ/molH2. However, due to the low intrinsic thermal conductivity of the powder material, it remains a challenge to transfer the produced heat (or cold) of reaction to the required component or heat transfer fluid. Thus, as for many applications the sensible mass of the final reactor is also an important characteristic, the reactor design is always a compromise between heat transfer enhancement measurements and system weight. In the presentation, the focus will be on two main thermal applications for metal hydrides: air-conditioning systems as well as pre-heating devices. For the corresponding boundary conditions, the performance of conventional commercial reactor designs based on plate heat exchanger and tubular heat exchanger will be presented and discussed. Furthermore, a complete new reactor design based on additive manufacturing will be presented and discussed in the context of new opportunities for reactor design in the future!

Authors : Carlos A. Castilla-Martinez, Umit B. Demirci
Affiliations : Institut Européen des Membranes, IEM – UMR 5635, ENSCM, CNRS, Univ Montpellier, Montpellier, France

Resume : Hydrazine borane N2H4BH3 (HB) and its derivatives are boron and nitrogen-based compounds that have been studied as potential hydrogen storage materials. Hydrazine borane stores 15.4 wt % of hydrogen but it presents some issues during its dehydrogenation like a high dehydrogenation temperature and the formation of hazardous by-products. Derivatives of hydrazine borane, named hydrazinidoboranes, overcome some of the issues present in HB thermolysis. To date, some alkaline hydrazinidoboranes have been synthesized (lithium, sodium, potassium), but the others are still missing. Obtaining new derivatives could shed some light on the chemistry of these B-N-based compounds. Rubidium hydrazinidoborane RbN2H3BH3 (RbHB) and cesium hydrazinidoborane CsN2H3BH3 (CsHB) have been synthesized for the first time. The obtention of these compounds was achieved by the reaction of metallic rubidium/cesium with HB in THF. The characterization of the materials was done by FTIR, 11B MAS-NMR, PXRD and molecular modeling. RbHB was found as a new crystalline compound and its structure was solved, the evaluation of its dehydrogenation properties and analyses of the solids residues were carried out and compared to those of other alkali hydrazinidoboranes. On the other hand, CsHB has shown an unexpected behavior compared to the other derivatives. The analyses of these compounds open up prospects on the chemistry of B-N-based materials for chemical hydrogen storage.

10:30 Coffee break    
Computational methods for hydride materials : Brandon Wood
Authors : M.P. Ariza, X. Sun, K.G. Wang, M. Ortiz
Affiliations : - Escuela Técnica Superior de Ingeniería, Universidad de Sevilla, Sevilla 41092, Spain - Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, United States - Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States - Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, United States

Resume : Understanding the transport of hydrogen within metallic nanomaterials is crucial for the advancement of energy storage and the mitigation of hydrogen embrittlement. Using nanosized palladium particles as a model, recent experimental studies have revealed several highly nonlinear phenomena that occur over long time periods. The time scale of these phenomena is beyond the capability of established atomistic models such as molecular dynamics. In this work, we present a new approach, referred to as diffusive molecular dynamics (DMD), to the simulation of long-term diffusive mass transport at the atomic scale. The basic assumption underlying DMD is that the time scale of diffusion is much larger than that of microscopic state transitions. In terms of numerical implementation, our approach involves the numerical integration of the master equation, and the numerical solution of a highly nonlinear optimization problem at every time-step. By working with atomic fractions, the characteristic time-step size of our DMD simulations can be much larger than those based on either AMD and KMC methods. Thus, the time-step size in our calculations is only limited by the diffusive time scale, e. g., by the speed of the propagation of a phase boundary, which can be as slow as 1 nm/s. The ability of DMD to predict the propagation of atomically-sharp phase boundaries over a time window of more than 30 s with full atomistic realism is particularly noteworthy. We also note that the scope of DMD is not limited to metal hydrides and a broad range of multi-species systems of practical interest suggest themselves as worthwhile foci for future studies.

Authors : Erika M. Dematteis(a), Nicola Berti(b), Nils Bornemann(c), Bettina Neumann(c), Marcello Baricco(b), Fermin Cuevas(a), Michel Latroche(a)
Affiliations : (a) ICMPE (UMR7182), CNRS, UPEC, 2 Rue Henri Dunant, 94320 Thiais, France; (b) Department of Chemistry and Inter-departmental Center Nanostructured Interfaces and Surfaces (NIS), University of Turin, Via Pietro Giuria 7, 10125 Torino, Italy;(c) GKN Sinter Metals Engineering GmbH, Krebsöge 10, D-42477 Radevormwald, Germany

Resume : Hydrogen, as an efficient energy carrier, can be used for storing and managing the energy produced from intermittent renewable sources, facilitating the transition towards CO2-free energy. Metal hydrides are safe materials for hydrogen storage under mild conditions of pressure and temperature. Among them, TiFe can efficiently store up to 1.86 wt.% H2 through consecutive formation of a monohydride β-FeTiH and dihydride, γ-FeTiH2. 1 However, FeTi exhibits difficult activation towards first hydrogen absorption and the presence of two plateau pressures.1 Elemental substitutions in intermetallic FeTi can solve activation issues and tune its hydrogen storage properties. In this work, characteristics of substituted FeTi alloys will be discussed, featuring their homogeneity domain, structures and hydrogen storage properties, i.e. both thermodynamics and kinetics, activation issues and cycling properties. In fact, FeTi substituted alloys, as in the case of Mn and Cu substitutions, can be tailored to tune plateau pressures to the specifications required by the final application.2–4 Their activation conditions, kinetic and thermodynamic properties, in relation to phase formation and stabilities will be discussed. This study enables remarkable understanding on hydrogen storage, structural knowledge and support to the industrial application of FeTi-type alloys for the development of large-scale hydrogen storage. References (1) Cuevas, F.; Burzo, E. Materials for Hydrogen Storage: AB Compounds. In Hydrogen Storage Materials, vol. 8; Springer-Verlag Berlin Heidelberg, 2018; pp 45–78. (2) Guéguen, A.; Latroche, M. Influence of the Addition of Vanadium on the Hydrogenation Properties of the Compounds TiFe0.9Vx and TiFe0.8Mn0.1Vx (X=0, 0.05 and 0.1). J. Alloys Compd. 2011, 509 (18), 5562–5566. (3) Challet, S.; Latroche, M.; Heurtaux, F. Hydrogen Storage in TiFe(0.70+x)Mn(0.20-x) (0 <= x <= 0.15) and TiFe(0.70)Mn(0.20-y)Ni(y) (0 <= y <= 0.08) Metallic Alloys. Mater. Sci. Technol. 2005, 13–21. (4) Ali, W.; Hao, Z.; Li, Z.; Chen, G.; Wu, Z.; Lu, X.; Li, C. Effects of Cu and Y Substitution on Hydrogen Storage Performance of TiFe0.86Mn0.1Y0.1−xCux. Int. J. Hydrogen Energy 2017, 42 (26), 16620–16631.

Authors : C. Milanese, A. Girella, P. Cofrancesco, M. Gaboardi, D. Pontiroli, G. Magnani, M. Riccò, A. Marini
Affiliations : Pavia Hydrogen Lab, Chemistry Department, University of Pavia (Italy); Carbon Nanostructures Lab, Department of Mathematical, Physical and Computer Sciences, University of Parma (Italy)

Resume : Alkali cluster-intercalated fullerides (ACIF) consist in crystalline nanostructures in which positively charged metal clusters are ionically bond to negatively charged C60 molecules, forming charge-transfer salts. These compounds have been recently investigated with renewed interest, appearing as a novel class of materials for hydrogen storage, thanks to their proved capability to uptake reversibly high amounts of hydrogen via a complex chemisorption mechanism. In this presentation, the synthesis, the structural investigation and the hydrogen storage properties of Li, Na and mixed Li-Na clusters intercalated fullerides belonging to the families NaxLi12-xC60 (0 ≤ x ≤ 12) and NaxLi6-xC60 (0 ≤ x ≤ 6) will be presented. By manometric and thermal analyses it has been proved that C60 covalently binds up to 5.5 wt% H2 at moderate temperature and pressure, thanks to the catalytic effect of the intercalated alkali clusters. Moreover, the destabilizing effect of Na in the co-intercalated NaxLi(6-x)C60 compounds leads to an improvement of the hydrogen-sorption kinetics by about 70%, linked to a decrease in the desorption enthalpy from 62 to 44 kJ/mol H2. The addition of Pt and Pd nanoparticles to Li fullerides increases up to 5.9 wt% H2 the absorption performances and of about 35 % the absorption rate. The ammonia storage properties of Li6C60 have also been investigated, resulting quite appealing. Being the price of C60 quite high for large scale practical applications, new cheaper C based materials are under examination. In particular, porous biochar from agricultural waste are giving interesting results as electrode materials for high-performance supercapacitors.

Authors : Nicola Patelli (1), Andrea Migliori (2), Vittorio Morandi (2), Luca Pasquini (1)
Affiliations : (1) Department of Physics and Astronomy, University of Bologna, 40127 Bologna, Italy; (2) Unit of Bologna, Institute for Microelectronics and Microsystems, National Research Council, 40129 Bologna, Italy

Resume : The holy grail for efficient seasonal and onboard hydrogen storage is a system that makes use of light and cheap materials and exchanges H2 at temperature and pressure close to the ambient ones. Mg-based H2 storage systems partly fulfill these requirements showing high volumetric and gravimetric H2-storage capability. The main drawbacks of MgH2 are the high stability and the sluggish sorption kinetics. Nanostructuring and mixing with catalytic additives (such as Nb2O5, Pd, TiH2) has been successfully demonstrated to accelerate H2 exchange kinetics, but still in the 200-350°C range. In this work, we present a detailed study of the thermodynamics and kinetics of H2 sorption by Mg/MgH2 in the 100-150°C range. We are able to investigate this unexplored range thanks to a novel concept of nanocomposite (Mg-Ti-H) in which TiH2 and MgH2 coexist at the single nanoparticle level, determining remarkably fast H2 sorption kinetics. Mg-Ti-H nanoparticles can complete the H2 absorption in minutes (up to 4.8 wt%) and fully release it in 1-2 hours in the <150°C range without the addition of expensive noble metal catalysts [2]. We critically evaluate the influence of nanostructure and phase mixing at the single nanoparticle level on the equilibrium and kinetic properties of H2 sorption. The proposed nanocomposite opens an unexpected window for Mg-based reversible H2 storage close to ambient temperature, even if the equilibrium pressures are just slightly above those of bulk Mg/MgH2.

12:30 Lunch break    
Design and application of hydride based systems : Chiara Milanese
Authors : Gavin S Walker, Alastair Stuart, Marcus Adams, David M Grant
Affiliations : Advanced Materials Research Group, University of Nottingham, Nottingham, UK.

Resume : There is an increasing interest in using the favourable thermodynamic properties of metal hydrides for thermal applications, either as a thermal energy store, to provide cooling, or for compression of hydrogen. The Mg/MgH2 system operating between 350 and 400oC offers opportunities as a thermal store for parabolic trough concentrated solar thermal power plants and for process heat in industrial plants. The use of the endothermic dehydrogenation can be used to provide cooling for refrigeration and air conditioning, in a solar thermal cycle. The last application, compression, capitalises on the van't Hoff relationship between pressure and temperature, in order to provide an effective heat powered solid state compressor. This presentation will explore some of the technical challenges in the design of vessels that can rapidly transfer heat in out of a powdered bed and the advantages of using a metal hydride slurry instead of a packed powdered bed. The presentation will also investigate the impact of non-idealised thermodynamic properties on the performance of the metal hydride and the selection of high temperature and low temperature metal hydride couples that most of these applications require.

Authors : Junxian Zhang, Nicolas Madern, Véronique Charbonnier, Judith Monnier and Michel Latroche
Affiliations : ICMPE (UMR7182), CNRS, UPEC, F-94320 Thiais, France

Resume : Metallic hydrides (MH) are widely studied and used as materials for energy storage due to their high reversible gas sorption capacity, and their potential application as negative electrode in Ni-MH or Li-ion batteries. LaNix (2 ≤ x < 5) compounds exhibit attractive hydrogen sorption properties by partial Mg substitution of lanthanum [1]. They adopt either a rhombohedral 3R (space group R-3m) or hexagonal 2H (space group P63/mmc) structure and can be described by the stacking along the c axis of two different subunits [La2Ni4] and [LaNi5]. The La-Mg-Ni system has been largely studied, but other ANix (A = rare earths) systems have been barely reported [2]. In this study, binary A2Ni7 alloys were synthesized, for A = La, Sm, Gd or Y. Their structural and hydrogen sorption properties have been studied. Furthermore, optimized alloy compositions by A-site substitution have been achieved. The influence of the A composition on the structural and H2 sorption properties will be discussed. References [1] Kohno, T.; Yoshida, H.; Kawashima, F.; Inaba, T.; Sakai, I.; Yamamoto, M.; Kanda, M. Journal of Alloys and Compounds 2000, 311, L5-L7. [2] Zhang, J.; Latroche, M, Magén, C.; Serin, V.; Hÿtch, M. J.; Knosp, B.; Bernard, P. J. Phys. Chem. C, 2014, 118, 27808

Authors : Shahrouz Nayebossadri David Book
Affiliations : University of Birmingham

Resume : Intermetallic alloys such as AB, AB2, and AB5 type have been studied due to their capability to reversibly store hydrogen. These alloys exhibit varying hydrogen storage properties depending on the crystal structure and composition. Compositional modification is commonly known as an effective method to modify the alloys thermodynamic and kinetics for various applications such as metal hydride batteries, metal hydrides hydrogen storage and compression. However, the effects of the compositional modification on the cyclic stability of these alloys are not usually well studied. Here, the hydrogen cycling stabilities of Ti-Mn based alloys with C14 type structure are studied. Hyper-stoichiometry, stoichiometry and hypo-stoichiometry alloys were prepared accordingly: Ti30.6V16.4Mn48.7 (Zr0.7Cr0.8Fe2.8) (B/A=2.19), Ti32.8V15.1Mn47.1 (Zr0.9Cr1.2Fe2.9) (B/A=1.97) and Ti34.5V15.4Mn44.7 (Zr0.9Cr1.3Fe3.2) (B/A=1.87). Whilst the hyper-stoichiometry alloy showed almost a stable (about 9 % capacity reduction) hydrogen capacity after 1000 cycles of hydrogenation and dehydrogenation, the stoichiometry and hypo-stoichiometry alloys failed to hydrogenate after about 950 and 500 cycles respectively. A limited reduction in the calculated crystalline size of the alloys was observed before and after the hydrogen cycling, denoting that pulverisation plays a less significant role on the observed hydrogen capacity loss. In addition, a reduction in the B/A ratio from 2.19 to 1.82 (hyper to hypo-stoichiometry) encouraged the formation of more stable hydride and a higher level of heterogeneous lattice strain. Whilst a small loss of hydrogen capacity (9%) in the hyper-stoichiometry alloy was attributed to the trapped hydrogen, the complete loss of hydrogen capacity in the stoichiometry and hypo-stoichiometry alloys seemed to originate from the formation of stable hydride and the lattice distortion.

Authors : Etsuo Akiba, Rika Hayashi
Affiliations : International Research Center for Hydrogen Energy, Kyushu University

Resume : Ti is the lightest and richest among metals that form reversible metal hydrides under ambient temperature and hydrogen pressure. Ti based hydrogen absorbing alloys are the most suitable candidates for stationary energy storage in the form of hydrogen. TiFe that was reported in 1974 has the hydrogen capacity of ~1.8 wt%. TiFe is the most cost-effective hydrogen absorbing alloy but activation and control of equilibrium hydrogen pressure are issues. Ti-based BCC solid solution alloys are developed by one of the authors in 1996. The hydrogen capacity reaches to ~4 wt% but absorbed hydrogen is reversible up to 75% of their content. To solve the roadblocks of TiFe, the third elements (M=V, Cr, Mn, Co, Ni, Zr, Nb and Sn) were added and TiFe0.8M0.2 were successfully synthesized. Every TiFe-based alloy could be activated under moderate conditions. In addition, hydrogen equilibrium pressure was controlled to some extent with substitution of the third elements. Ti-based BCC solid solution alloys contain hydrogen up to 4 wt% but reversible hydrogen is less than 3 wt%. The residual hydrogen in the hydride is very stable for desorption at room temperature. In addition, equilibrium pressure is more sensitive to lattice parameter than conventional intermetallic compounds. To reduce the amount of residual hydrogen and control equilibrium pressure, metal elements were added to Ti-based BCC alloys. The results of addition of the fourth (fifth) elements may be introduced at the conference.

15:30 Coffee break    
Design and application of hydride based systems II : Olena Zavorotynska
Authors : Yaroslav Filinchuk
Affiliations : Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium

Resume : Firstly, I will show recent attempts to design a molecular system capable to store hydrogen reversibly. We have developed systems based on Al with complex and chemical hydrides coordinated to it, such as ammonia borane NH3BH3 (AB), amidoborane NH2BH3– and borohydrides BH4– [1]. We showed [2] that the ability of the strong Lewis acid Al3+ to coordinate both the initial hydrogenated species as well as their dehydrogenation products makes it a good template for chemical transformations of hydrides. In particular, AB coordinated to Al3+ in Al(BH4)3∙NH3BH3 endothermically dehydrogenates to a single product identified as Al(BH4)3∙NHBH, with a potential for a direct rehydrogenation of AB. More recent work explores the possibility to substitute the anions coordinated to Al, as well as modify AB by a substitution on the N-side [3]. Secondly, porous materials can be also made of hydrides [4]. We investigated gas sorption in the porous γ-Mg(BH4)2 using neutron powder diffraction to accurately localize the guests and synchrotron X-ray powder diffraction to collect data along the adsorption isobars. We are trying to extend the family of hydridic porous solids by combining imidazolates (ligands known to build stable frameworks) and complex hydrides (should be responsible for the unusual functionality). The approach and recent results will be presented. [1] Dovgaliuk, I. et al. (2017). ChemSusChem 10, 4725-4734. [2] Dovgaliuk, I. & Filinchuk, Y. (2016). Int. J. Hydr. Energy 41, 15489-15504. [3] Dovgaliuk, I., Møller, K.T., Robeyns, K., Louppe, V., Jensen, T.R. & Filinchuk, Y. (2019) Inorg. Chem. DOI: 10.1021/ acs.inorgchem.8b02630 [4] Filinchuk, Y. et al. (2011). Angew. Chem. Int. Ed. 50, 11162-11166. [5] Burazer, S., Morelle, F., Filinchuk, Y., Černý, R. & Popović J. (2019) Inorg. Chem. DOI: 10.1021/ acs.inorgchem.9b00446

16:30 L.5.6
Authors : Valerio Gulino, Matteo Brighi, Fabrizio Murgia, Carlo Nervi, Radovan ?erný and Marcello Baricco
Affiliations : (V. Gulino, Presenting Author, Department of Chemistry and Inter-departmental Center Nanostructured Interfaces and Surfaces (NIS), University of Turin, Via Pietro Giuria 7, 10125 Torino, Italy; (M. Brighi) Laboratoire de Cristallographie, DQMP, Universite? de Gene?ve, quai Ernest-Ansermet 24, CH-1211 Geneva 4, Switzerland; (F. Murgia) Laboratoire de Cristallographie, DQMP, Universite? de Gene?ve, quai Ernest-Ansermet 24, CH-1211 Geneva 4, Switzerland; (C. Nervi) Department of Chemistry and Inter-departmental Center Nanostructured Interfaces and Surfaces (NIS), University of Turin, Via Pietro Giuria 7, 10125 Torino, Italy; (R. ?erný) Laboratoire de Cristallographie, DQMP, Universite? de Gene?ve, quai Ernest-Ansermet 24, CH-1211 Geneva 4, Switzerland; (M. Baricco) Department of Chemistry and Inter-departmental Center Nanostructured Interfaces and Surfaces (NIS), University of Turin, Via Pietro Giuria 7, 10125 Torino, Italy.

Resume : This study of shows a flexible system that offers promising candidates for Li-based solid state electrolyte. In this work, the effect of the halogenation on the electrochemical properties in the LiBH4-LiBr-LiCl system has been investigated. The LiBH4-LiBr-LiCl ternary phase diagram has been determined at RT by X-ray Powder Diffraction, coupled with Rietveld refinement. For the first time, a ternary hexagonal solid solution containing chloride anion was stabilized at RT, decreasing the weight of the electrolyte and hence increasing the energy density. The effect of the halogenation on the Li-ion conductivity and electrochemical stability has been investigated by Electrochemical Impedance Spectroscopy and Cyclic Voltammetry. The h-Li(BH4)0.7(Br)0.2(Cl)0.1 sample showed the highest value of Li ion conductivity at RT (1.3 × 10^-5 S/cm), suggesting possible applications of these fast ion conductors as solid-state electrolyte in Li-ion batteries. The values of Li-ion conductivity at room temperature depend only on the BH4- content in the solid solution, suggesting that the Br/Cl ratio does not affect the defect formation energy in the structure. The chloride anion substitution in the hexagonal structure increases the activation energy, moving from about 0.45 eV for sample without Cl-, up to about 0.63 eV for h-Li(BH4)0.6(Br)0.2(Cl)0.2. In addition, a wide electrochemical window of 4.04 V vs. Li+/Li is reached in the Li-Br system, while the further addition of Cl is a trade-off between oxidative stability and weight reduction.

Authors : Filippo Peru1, SeyedHosein Payandeh GharibDoust2-3, Georgia Charalambopoulou1, Torben R. Jensen3, Theodore Steriotis1
Affiliations : 1. National Center for Scientific Research “Demokritos”, Neapoleos 27, 15341 Ag. Paraskevi, Attikis, Athens, Greece 2. aEmpa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland 3. Center for Materials Crystallography, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark

Resume : Alkali metal and alkali earth borohydrides, due to their high hydrogen content and availability, are interesting materials for hydrogen storage in stationary or mobile systems. However, the high thermal stability and the limited cyclability are obstacles to an efficient and large-scale application. Eutectic melting and nanoconfinement can affect and improve kinetics and hydrogen reversibility. The eutectic mixture of 0.71 LiBH4 − 0.29 NaBH4 melts at 219°C and can be easily infiltrated in carbon scaffolds.1,2 The presence of carbon has a catalytic effect on the release of hydrogen, lowering decomposition temperatures and improving the desorption rate. On the other hand, the nanoconfinement of the eutectic mixture in small mesopores makes the system reversible, unlike the bulk material. In an attempt to investigate the thermodynamic and kinetic behaviour of nanoconfined LiBH4/NaBH4 and make a comparison with the bulk borohydrides, the study included mesoporous and non-porous carbons. All composites were systematically studied with several techniques such as N2 adsorption/desorption at 77K, X-ray diffraction, TPD-MS and H2 absorption/desorption cycles. (1) Dematteis, E. M.; Roedern, E.; Pinatel, E. R.; Corno, M.; Jensen, T. R.; Baricco, M. A Thermodynamic Investigation of the LiBH4-NaBH4 System. RSC Adv. 2016, 6, 60101–60108. (2) Javadian, P.; Sheppard, D. A.; Buckley, C. E.; Jensen, T. R. Hydrogen Storage Properties of Nanoconfined LiBH4-NaBH4. Int. J. Hydrogen Energy 2015, 40 (43), 14916–14924.

Poster Session : Olena Zavorotynska
Authors : Moon-Sun Chung
Affiliations : Principal researcher of Hydrogen energy research team, KIER

Resume : Hydrogen storage is one of the key obstacles to the commercialization as well as market acceptance of hydrogen fueled vehicle. Besides the efficiency of power system, it is an extremely challenging technology to store sufficient hydrogen on the vehicle without compromising consumer requirement such as safety, space, driving range, and fuel cost. There are three main hydrogen storage methods including compression, liquefaction and hydrogen storage materials. Among the technologies currently under development, the hydrogen storage as a highly pressurized gas is the most prominent candidate for the hydrogen powered vehicle now. The advanced automobile industries have already demonstrated the highly pressurized hydrogen system on fuel cell vehicles for past several years. The hydrogen storage materials in solid state have some advantages such as high volumetric storage capacity, little energy loss, longer storage time and highest safety. Various carbonaceous and non-carbonaceous hydrogen storage materials have been studied over the past few years in Korea. To improve the adsorption/desorption performance of hydrogen storage alloys in hydrogen storage device, it is advantageous to use a hydrogen storage alloy having a highly effective thermal conductivity. Sodium aluminum hydride NaAlH4 (SAH) is one type of promising hydrogen storage alloys, and used in powder or compacted pellet forms. In order to increase the volumetric storage density in the hydrogen storage device, a compacted pellet shape having a high effective density of the hydrogen storage alloy is used. The enthalpy change of SAH due to adsorption and desorption of hydrogen is approximately 40 kJ/mole of H2. The hydrogen storage alloy should be heated and cooled rapidly to adsorb and desorb hydrogen within a short time. In this case, it is highly advantageous to increase the effective thermal conductivity of the hydrogen storage alloy. In this presentation, we would like to introduce our new developing hydrogen storage system including a internal heat exchanger for FCV based on a SAH.

Authors : Michael Heere1,2, D.R. Sørensen2,3, M. Knapp1, H. Ehrenberg1 & A. Senyshyn2
Affiliations : 1 Institute for Applied Materials—Energy Storage Systems (IAM-ESS), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein, Germany & 2 Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1 85748 Garching b. München, Germany. 3 Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

Resume : The development of the ErwiN – Energy research with Neutrons – neutron powder diffraction (NPD) beamline is presented with three possible advancements: Firstly, the primary beam optics will be replaced to bring this diffractometer to the same level as the high flux and high resolution instrument D20 at the ILL. The ErwiN instrument will be used for the investigation of energy storage materials, also integrated in complete components and under real operating conditions. Thus, it is possible to scan a large parameter space (e.g. temperature, state of charge, charge rate, fatigue degree) for the investigation of modern functional materials in kinetic and time-resolved experiments. Diffraction data will be obtained from the entire sample volume or in a spatially resolved mode from individual parts of the sample. ErwiN is designed for different scenarios: for very fast measurements at medium resolution, for medium fast measurements at higher resolution and for very high resolution still at a reasonable time frame. The final commissioning and integration of ErwiN is the second important objective which will be addressed, while thirdly, the integration of newly developed and strongly needed sample environment, e.g. H2-gas system, will enhance the attractiveness for a wider community in energy research as well as materials science while furthermore developing novel methods for the neutron science community.

Authors : Kasper T. Møller, Mark Paskevicius, Jacob G. Andreasen, Junqiao Lee, Nigel Chen-Tan, Jacob Overgaard, SeyedHosein Payandeh, Debbie S. Silvester, Craig E. Buckley, Torben R. Jensen
Affiliations : Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus, DK-8000 Aarhus, Denmark. Department of Imaging and Applied Physics, Fuels and Energy Technology Institute, Curtin University, GPO Box U1987, Perth 6845, WA, Australia. Curtin Institute for Functional Molecules and Interfaces, School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth 6845, WA, Australia.

Resume : Metal closo-hydridoborates, e.g. M2B12H12, have received increased attention as ion conductors due to extraordinary ionic conductivity in their high-temperature structural polymorphs. Recently, nanoconfinement of Li2B12H12 was achieved via a solid-gas reaction inside a nanoporous SiO2 (SBA-15) scaffold between LiBH4 and gaseous B2H6. However, the reaction yields moderate purity (94 mol%) Li2B12H12 with 6 mol% Li2B10H10. The ionic conductivity of the nanoconfined sample was 1.0 x 10-7 S·cm-1 at room temperature, which is similar to bulk Li2B12H12. In this work, solvated lithium closo-dodecaborate, Li2B12H12·Solv. (Solv. = tetrahydrofuran, acetonitrile), show unexpected melting at low temperature (T < 145 °C) and subsequent recrystallisation of the parent compound at higher temperature. This feature has been explored to melt infiltrate Li2B12H12 into a nanoporous scaffold (SBA-15), which ensures a 100% purity. Small-angle X-ray scattering confirms that melt infiltration occurred, while the ionic conductivity of the nanoconfined and molten Li2B12H12 was measured by EIS.

Authors : Eli Grigorova1, Diana Nihtianova2, Boyko Tsyntsarski3, Pavel Markov1 and Ivanka Stoycheva3
Affiliations : 1Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria; 2Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 107, 1113 Sofia, Bulgaria; 3Institute of Organic Chemistry, Bulgarian Academy of Sciences, bl. 9, Acad. G. Bonchev str., 1113 Sofia, Bulgaria

Resume : Magnesium-based materials are promising as hydrogen storage media due to their high hydrogen absorption capacity and low price. The subject of this study are the hydrogen sorption characteristics of the composites 80wt.% MgH2-15 wt. % Ni- 5wt.% activated carbon (synthesized from polyolefin wax, a waste product of polyethylene production at low pressure- POW) and 90 wt% MgH2-5 wt. % Ni- 5wt.% POW prepared by ball milling under argon atmosphere. The polyolefin wax was submitted to pyrolysis and steam activation, in order to prepare nanoporous carbon POW and used as additive in the preparation of MgH2-Ni composites. Structure, phase and surface composition of the starting compounds and the sample before and after hydriding are determined by XRD and TEM. The maximum achieved absorption capacity of the composites at 573 K and after 60 min of hydriding are 5.3 wt. % H2 for the material with higher Ni content and 5.5 wt % H2 for the other sample. The presence of both additives - nickel and activated carbon derived from POW has a positive impact on hydrogenation kinetics and the capacity achieved. The results from TEM characterization e. g. the polycrystalline SAED show the presence of graphite, Mg and monoclinic Mg2NiH4. Keywords: Mg- based composites, sorption kinetics, hydrogen storage, activated carbon Acknowledgments: Financial support from Bulgarian Academy of Sciences and Bulgarian Ministry of Education (Project DFNI-KП-06-H27/9, 08/12/2018) is gratefully acknowledged.

Authors : Jeong-Hyun Park, Soonhyun Kim
Affiliations : Smart Textile Convergence Research Group, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Republic of Korea

Resume : In recent years, hybrid nanocrystals (HNs) have emerged as an important class of materials to tune the optical, electrical, magnetic and catalytic properties of nanocrystals. In HNs, two disparate functional material systems (i.e., metal/magnet, metal/semiconductor and magnet/semiconductor) are combined through their crystal facets, which results in the nontrivial synergetic effects including extinction enhancement due to the coupling of surface plasmon resonance and electronic doping by the intraparticle charge transfer. Among different types of HNs, metal-semiconductor HNs are of particular interest in photocatalysis because it can provide a very good light absorbing semiconductor properties and catalytically active metal nanostructure properties. In this paper, we investigated a new and simple strategy to construct Pt-CsPbBr3 HNs, and shows that light-driven CO2 reduction reaction could be enhanced by synergetic effects between CsPbBr3 and Pt as they promote enhanced light absorption and facilitate the charge separation of the photogenerated carriers.

Authors : J. Barale1, P. Rizzi1, E. Casella2, M. V. Abbas2, C. Luetto2, S. Staulo3, M. Baricco1
Affiliations : 1 Department of Chemistry and Inter-departmental Center Nanostructured Interfaces and Surfaces (NIS), University of Turin, Via Pietro Giuria 7, 10125 Torino, Italy 2 Tecnodelta S.r.l., Via Francesco Parigi 5H, 10034 Chivasso (To), Italy 3 Stones sas, Via Sacra di S. Michele 21/b, 10093, Collegno (To), Italy

Resume : The aim of this work is to realize a metal hydride (MH) compressor to provide compressed H2 for a small scale hydrogen refuelling station (HRS). In the refuelling station, H2 is produced by an electrolyser, compressed through a MH-compressor (MHC) and stored in high pressure bottles. The latter are used to supply a demonstrative PEM-FC drone, planned for a flight time of 2 hours. The use of MHs to compress H2 is an innovative and efficient way to convert energy from a heat source into compressed gas, avoiding the use of electricity. Compression is linked to the thermodynamics of the reversible reaction between H2 and a metal (M) to form MH and producing heat. Compression occurs since M can absorb H2 at low pressures and low temperatures, forming MH. Afterwards, MH is heated up and H2 is released at a significantly higher pressure. In this work, compression occurs between 20 and 150 °C, from 20 to 200 bar, using two commercial alloys (La0.9Ce0.1Ni5 and Hydralloy®) in series. Lumped simulations were performed based on experimental kinetic and thermodynamic data of hydrogen sorption reactions. Moreover, a lab-scale compressor was also realized to validate the model. The work involves also the study of a TiCr2-based alloy to reach a pressure up to 400 bar. Results of the lab-scale compressor were used for the scale-up. The design of compressor for the HRS is based on the amount of H2 necessary to supply the PEM-FC of the drone (i.e. about 83 g H2 for 2 hours of flight). For the MHC, about 1 kg of M is used in each stage and H2 is compressed and stored up to 200 bar. The integration of the compressor in the HRS, including a proper electrolyser and photovoltaic panels for its electrical supply, will be outlined.

Authors : Gracia Shokano, Supervisors: Dr. Zahir Dehouche, Dr. George Fern
Affiliations : Brunel University of London College of Engineering, Design, and Physical Sciences

Resume : Hydrogen appears to be the most attractive source of energy alternative to carbon-based fuels, it can be produced from a variety of renewable resources, e.g. biomass and water electrolysis. Hydrogen is environmentally friendly, it releases water vapour into the environment during combustion which offers near-zero emissions of pollutants and greenhouse gases. The economy of hydrogen is still under development. The major challenge is finding an effective route of storing hydrogen for vehicles applications. The conventional storage methods such as liquefaction or compression resulted in energy efficiency and safety concerns. E.g. liquid storage in term of a low boiling point -252.87 ⁰C, high-cost material is needed to maintain a cryogenic state. The focus is to develop sustainable solid-state storage materials. Magnesium hydride is considered as the potential storage medium. Mg has the highest hydrogen storage capacity of 7.6 wt. %. However, Mg has undesirable thermodynamics and kinetics. The MgH2 sorption resulted in a high temperature approximately 250⁰ C which needs to be reduced to 100⁰ C and the hydrogen sorption rate needs to be accelerated. The sorption kinetics can be improved by catalyzing the surface and nanosizing to provide a pathway for hydrogen diffusion. The thermodynamics by alloying Mg to form a new compound or phase. The MgH2 – catalyst mixture material was prepared by ball milling of pure MgH2 with nano-sizer ZrNi, where the catalyst was prepared using an innovative method. The resulted nanostructure powder was characterized by using both the EDS-SEM and X-ray Diffraction. The results determined the characteristics of the synthesized powder. More characteristic studies need to be done such as the TGA (Thermogravimetric analysis), and the XRD crystallographic and TEM to determine the actual size of the particle. Further investigations are required on the PCT isotherm of hydrogen absorption/desorption.

Authors : Arndt Remhof (1); Léo Duchêne (1,2); Ryo Asakura (1,2); Seyedhosein Payandeh (1); Ruben-Simon Kühnel (1); Hans Hagemann (2); Corsin Battaglia (1)
Affiliations : (1) Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Swit-zerland; (2) Département de Chimie-Physique, Université de Genève, 1211 Geneva 4, Switzerland

Resume : Hydroborates are a promising alternative class of solid electrolytes that combine liquid-like ionic conductivity with high electrochemical stability, high thermal stability and favorable mechanical properties [1-3]. Using the mixed-anion compound Na4(B12H12)(B10H10) as electrolyte, we real-ized stable cycling of 3 V all-solid-state battery using sodium metal as anode and NaCrO2 as cath-ode. We achieved a capacity of 85 mAh/g at C/20 and 80 mAh/g at C/5 with more than 90% capacity retention after 20 cycles at C/20 and 85% after 250 cycles at C/5 [1,2]. Here, we discuss the implementation of this solid electrolyte in all-solid-state batteries using solution-based techniques and we elucidate the conduction mechanism of this electrolyte. We show that the fast sodium ion diffusion is correlated to the rotational and librational motions of the anions, resulting in a complex temperature dependence of the conductivity [4,5]. References [1] L. Duchêne et al., Chem. Commun., 53, 4195 (2017). [2] L. Duchêne et al., Energy Environ. Sci., 10, 2609 (2017). [3] R. Moury et al., Acta Cryst. B, in press [4] L. Duchêne et al., Chem. Mat., 31, 3449, (2019). [5] T. Burankova et al., J. Phys. Chem. Lett. 9, 6450 (2018). --------------------------------------------------------------

Authors : Marcell Gajdics, Ferenc Béke, Zoltán Novák, Ladislav Havela, Viktória Kovács Kis, Erhard Schafler, Ádám Révész
Affiliations : Department of Materials Physics, Eötvös University, P.O.B. 32, H-1518 Budapest, Hungary; Department of Organic Chemistry, Eötvös University, P.O.B. 32, H-1518 Budapest, Hungary; Department of Organic Chemistry, Eötvös University, P.O.B. 32, H-1518 Budapest, Hungary; Department of Condensed Matter Physics, Charles University, 116 36 Prague, Czech Republic; Center of Energy Research, Hungarian Academy of Sciences, H-1121 Budapest, Hungary; Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, A-1090 Vienna, Austria; Department of Materials Physics, Eötvös University, P.O.B. 32, H-1518 Budapest, Hungary

Resume : There is a pressing need for material possessing decent hydrogen storage properties. Magnesium is considered as one of the most attractive hydrogen storage materials, mainly because of its high storage capacity (7.6 wt.%), lightweight and low cost. Unfortunately the high desorption temperature of MgH2 and the slow kinetics of sorption reactions prevent its use in a wide range of applications. However there are multiple ways to improve the hydrogen sorption properties of Mg. Ball-milling and different severe plastic deformation (SPD) methods are shown to be effective techniques to enhance the kinetics of absorption and desorption. Different catalysts (like TiO2) and alloying elements are also often used to improve the hydrogen storage properties of Mg. In the present work titanate nanotubes were prepared by microwave assisted hydrothermal method. High energy ball-milling of Mg was carried out with the addition of titanate nanotubes, using different milling times. The milled powder was then subjected to high-pressure torsion for further deformation. For comparison, a sample with TiO2 addition was also prepared. In order to investigate the effect of the additives, absorption-desorption measurements were carried out. The microstructure of the material was studied by X-ray diffraction, for local analysis of the morphology of the nanotubes, transmission electron microscopy was employed.

Authors : Sina Sadigh Akbari, Ferdi Karadaş
Affiliations : Department of Chemistry, Bilkent University, Çankaya, Ankara, 06800, Turkey

Resume : Photocatalytic water splitting with colloidal suspensions has attracted considerable attention recently. The approach that involves linking a particle light absorber with a molecular catalyst combines the advantages of homogeneous and heterogeneous catalysis. Recently, layered double hydroxides (LDHs) have been widely used in photocatalysis, due to their abundant active metal centers. Inspired by the previous studies on colloidal systems, in this work, our efforts on coupling Prussian blue analogues as catalyst with other light-harvesting semiconductors such as layered-double hydroxides (LDHs) will be presented.

Authors : R. Bowman, A-L. Chaudhary, H. Cao, M. Heere, T. Klassen, M. Dornheim
Affiliations : 1. Nanotechnology Department, Helmholtz-Zentrum Geesthacht, 21502 Geesthacht, Germany 2. Institute for Applied Materials – Energy Storage Systems (IAM-ESS), Karlsruhe Institute of Technology Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany;

Resume : An efficient storage system based on solid state hydrogen requires a fundamental understanding of the material properties. Intermetallics (Ti-based) and complex hydrides (magnesium amide based) are very promising hydrogen-storage materials, due to their volumetric energy storage capacities and for their operation under moderate temperatures and pressures. These materials also have increased functionality once introduced into high pressure conditions either for compressor systems or high-pressure tanks up to 700 bar and above. Storing hydrogen in such a system would yield a significant increase in volumetric capacities and potentially reducing maintenance costs thereby allowing hydrogen powered vehicles to be more widespread. Currently, there is no single solution that meets the range of requirements, neither metal hydride nor compressed gas storage tanks. Novel high content hydrogen materials have been characterised under high pressure and will be presented here. These use of these materials will lead to breakthroughs regarding overall efficiency of either high pressure tank or non-mechanical compressor systems.

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Joint Session L&M Theory and experiment : Martin Eickhoff and Smagul Karazhanov
Authors : Su-Huai Wei
Affiliations : Beijing Computational Science Research Center, Beijing 100193, China

Resume : Transparent conducting oxides (TCOs), which combine high electrical conductivity and high optical transmission in the visible spectral range, are needed in many modern optoelectronic devices, such as solar cells, flat-panel displays, touch-screen sensors, light emitting diodes and transparent thin film transistors. In this talk, I will highlight our study on the band structure and doping control of TCOs. In particular, I will discuss (i) the fundamental band structures and defect properties for the TCOs; (ii) how to achieve simultaneously high transparency and conductivity in n-type TCOs; (iii) why p-type TCOs are difficult to achieve; (iv) how to modify the band structure or design new materials to achieve p-type TCOs or even bipolarly dopable TCOs. Based on the understanding above, we hope to provide useful guidelines for the rational design of novel TCOs that are critical for the development of the next-generation optoelectronic materials.

Authors : Marco Altomare
Affiliations : Department of Materials Science and Engineering WW4-LKO, University of Erlangen-Nuremberg, Martensstrasse 7, 91058 Erlangen, Germany. E-mail:

Resume : Photocatalytic H2 evolution on virtually any pristine semiconductor surface is characterized by low efficiencies due to trapping and recombination of charge carriers, and due to a sluggish kinetics of charge transfer (1). Thus, co-catalyst metal nanoparticles are typically decorated at the semiconductor surface to reach reasonable photocatalytic yields. For this, most common strategies involve wet chemical methods, e.g. impregnation, chemical reduction or photo-deposition. An intriguing, alternative pathway is ?solid state dewetting?: as-deposited thin (nm-thick) metal films on a given surface are usually metastable and when heated to a certain temperature tend to ?dewet?, i.e. they break up and aggregate into defined metal particles (2). Factors such as the initial metal film thickness and composition, treatment temperature, atmosphere and time, can influence morphological and physicochemical features of the dewetted particles (2,3) (e.g. shape, size, dispersion, composition and crystallinity, among others) that are key for their co-catalytic ability in photocatalytic reactions. This talk discusses the use of dewetting as a precise nanostructuring tool to form functional metal nanoparticles at highly-defined TiO2 nanotube surfaces (4), namely to engineer catalyst/semiconductor platforms for light-driven reactions. In particular, we discuss how metal dewetting, steered in size, order, and composition, and synergistically combined with additional self-ordering principles (e.g. alloying, dealloying), can enable various types of functionalization of semiconductor surfaces for photocatalytic applications (5?8). (1) Takanabe, K. ACS Catal. 2017, 7 (11), 8006?8022. (2) Thompson, C. V. Annu. Rev. Mater. Res. 2012, 42 (1), 399?434. (3) Leroy, F.; Borowik, ?.; Cheynis, F.; Almadori, Y.; Curiotto, S.; Trautmann, M.; Barbé, J. C.; Müller, P. Surf. Sci. Rep. 2016, 71 (2), 391?409. (4) Yoo, J. E.; Lee, K.; Altomare, M.; Selli, E.; Schmuki, P. Angew. Chemie Int. Ed. 2013, 52 (29), 7514?7517. (5) Nguyen, N. T.; Altomare, M.; Yoo, J.; Schmuki, P. Adv. Mater. 2015, 27 (20), 3208?3215. (6) Altomare, M.; Nguyen, N. T.; Hejazi, S.; Schmuki, P. Adv. Funct. Mater. 2018, 28 (2), 1704259. (7) Spanu, D.; Recchia, S.; Mohajernia, S.; Schmuki, P.; Altomare, M. Appl. Catal. B Environ. 2018, 237 (May), 198?205. (8) Spanu, D.; Recchia, S.; Mohajernia, S.; Tomanec, O.; Kment, ?.; Zboril, R.; Schmuki, P.; Altomare, M. ACS Catal. 2018, 8 (6), 5298?5305.

Authors : Marco Arrigoni, Georg K. H. Madsen
Affiliations : Institute of Materials Chemistry, TU Wien, A-1060 Vienna, Austria

Resume : The growing interest for environmental protection and the pursuit for renewable and clean energy sources have made the TiO2-assisted photoelectrochemical water splitting a very active research area. For such application, TiO2 nanoparticles are commonly used due to their superior performances, with anatase being the most commonly observed polymorph in small particles. The study and characterization of native point defects is of paramount importance for understanding the electronic properties of the material and the impact on the photocatalytic activity. Moreover, native defects play a fundamental role also in doped systems, where they can compensate for the defect-introduced carriers. Although several first-principles studies of native point defects in TiO2 anatase exist, they are mostly consider a few of them at a time. The different levels of theory employed in the literature do not allow for a direct calculation of the equilibrium concentrations as different formation energies are often reported with different functionals and corrections schemes.In this study, we comprehensively investigate the stability of native point defects in TiO2 anatase using the GGA+U approach. All native point defects and their ionized states are considered. We systematically compare state-of-the-art methods for obtaining reliable formation energies and correcting for finite-size-errors. Equilibrium defect and carriers concentrations are then calculated with respect to different growth conditions.

Authors : J. Dolado(1), P. Hidalgo(1), A. M. Sánchez(2) and B. Méndez(1)
Affiliations : 1 Department of Materials Physics. Faculty of Physics, Complutense University of Madrid, E-28040 Madrid, Spain 2 Department of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom

Resume : Semiconductor oxides nanowires (NWs) are an excellent benchmark to produce complex nanostructures, which could lead to novel architectures in a NW-heterostructure morphology with enhanced physical properties. Recently, wide band gap oxides, such as Zn2GeO4, are emerging as potential candidates for applications in high power devices or in ultraviolet-solar blind photodetectors [1]. In this work, we report the synthesis and characterization of complex nanostructures of oxide NWs in which Zn2GeO4 NWs combine with SnO2 particles, in a self-organized manner. The synthesis method is the thermal evaporation of the suitable chemical precursors on a catalyst-free basis via a vapour-solid mechanism. Electron microscopy measurements have been carried out to assess the morphology, the microstructure and determine the orientation of the NWs. The results support a model growth in which the Plateau-Rayleigh mechanism [2] would produce a pattern of germanium oxide amorphous particles along the Zn2GeO4 NW. In addition, under suitable kinetic conditions, these particles act as nucleation sites for well-faceted SnO2 crystals. The luminescence properties have been assessed by means of cathodoluminescence and photoluminescence techniques. In addition, optical confinement effects have been observed, what could be further exploited in the design of optical microcavities. References [1] H. Mizoguchi, T. Kamiya, S. Matsuishi, H. Hosono, ?A germanate transparent conductive oxide?, Nature Communications, 2, 470 (2011). [2] R. W. Day, M. N. Mankin, R. Gao, Y. No, S. Kim, D. C. Bell, H. Park and C. M. Lieber, ?Plateau?Rayleigh crystal growth of periodic shells on one-dimensional substrates? Nature Nanotechnology, 10, 345 (2015).

15:30 Coffee break    
Authors : Ulrike Boesenberg
Affiliations : European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany

Resume : Many materials for energy storage undergo phase transformations to store and release the energy in form of hydrogen, ions or electrons involving mass transport. To understand and finally overcome the rate limiting processes detailed understanding of the systems is necessary. This includes the structure of crystalline systems, the reaction pathway with possible metastable phases as well as the mesoscale to identify inhomogeneities and long term effects. Here X-rays, especially synchrotron radiation, can provide a wide range of methods spanning from XRD to characterize the crystalline phases, spectroscopy to characterize chemical species to spatially resolved techniques (X-ray microscopy) or combinations thereof. This presentation will show some examples for different techniques and results from metal hydrides for hydrogen storage, intercalation and conversion materials for Li-ion batteries and catalyst particles. With the advance of X-ray free electron lasers the door has opened to directly study ultrafast phenomena such as i.e. nucleation also in the time domain.

Joint Session L&M Advanced Characterisation Techniques for Energy Materials : Inga Bürger
Authors : Ulrike Boesenberg
Affiliations : European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany

Resume : Many materials for energy storage undergo phase transformations to store and release the energy in form of hydrogen, ions or electrons involving mass transport. To understand and finally overcome the rate limiting processes detailed understanding of the systems is necessary. This includes the structure of crystalline systems, the reaction pathway with possible metastable phases as well as the mesoscale to identify inhomogeneities and long term effects. Here X-rays, especially synchrotron radiation, can provide a wide range of methods spanning from XRD to characterize the crystalline phases, spectroscopy to characterize chemical species to spatially resolved techniques (X-ray microscopy) or combinations thereof. This presentation will show some examples for different techniques and results from metal hydrides for hydrogen storage, intercalation and conversion materials for Li-ion batteries and catalyst particles. With the advance of X-ray free electron lasers the door has opened to directly study ultrafast phenomena such as i.e. nucleation also in the time domain.

Authors : Claudia Zlotea and Jorge Montero
Affiliations : Institut de Chimie et des Matériaux de Paris Est, CNRS-UPEC

Resume : Multi-Principal-Element Alloys (MPEAs) belong to a new metallurgical paradigm based on the alloying of four or more elements with equal concentrations. Most of reports concerning these alloys describe their structure, microstructure and mechanical properties, whereas functional properties such as, hydrogen sorption, are only scarcely investigated. We present here the study of hydrogen absorption properties of MPEAs based on refractory metals. The TiVZrNbX (X = Mg, Al and Ta) alloys have been synthesized by classical high temperature methods or mechanosynthesis under inert atmosphere. To directly produce hydrides we have employed the reactive ball milling under hydrogen gas starting from the pure metal powders. The properties of materials have been studied by several experimental techniques: X-ray diffraction, electron microscopy, neutron diffraction, pressure-composition-isotherm, thermal desorption spectroscopy. All the alloys are bcc single-phased and undergo one-step reaction with hydrogen. We suggest that the lattice distortion, δ, might play an important role: larger δ would favours a single-step reaction, whereas small δ would favour a two-steps phase, as encountered for conventional bcc alloys. The hydrogen absorption/desorption is completely reversible and the capacities varies between 2 and 3 wt%. In summary, this is an original research topic in the field of solid-state hydrogen storage that might open new routes for the design of multifunctional materials.

Authors : Hai-Wen Li1, Kaveh Edalati1, Ryoko Uehiro, Yuji Ikeda2,3, Hoda Emami1, Yaroslav Filinchuk4, Makoto Arita1, Xavier Sauvage5, Isao Tanaka2, Etsuo Akiba1 and Zenji Horita1
Affiliations : 1 Kyushu University, Fukuoka 819-0395, Japan 2 Kyoto University, Sakyo, Kyoto 606-8501, Japan 3 Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany 4 Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium 5 Normandie Univ, UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, 76000, Rouen, France

Resume : MgH2 is one of the most investigated solid-state hydrides as promising hydrogen storage materials due to its large hydrogen capacity of 7.6 mass% and the high abundance of Mg in Earth's crust. The high thermodynamics (-75 kJ/mol H2) of MgH2 originated from the strong Mg-H binding energy results in the serious issue of high dehydrogenation temperature, i.e. above 300°C for pure MgH2. Forming an alloy with a hydride non-forming transition metal has been approved to be a feasible approach to destabilize MgH2. For example, when alloying with Ni to form a binary Mg2Ni, the hydride transforms from MgH2 to Mg2NiH4, and the enthalpy is reduced from -75 to -64 kJ/mol H2. Ternary alloys like RMg2Ni9 and (Mg,Ca)Ni2 can further destabilize MgH2 and can absorb and desorb hydrogen at room temperature, whereas the gravimetric hydrogen capacity is limited due to the Ni-rich composition. It is hard to produce an Mg-based ternary alloy with a homogeneous elemental distribution by melting process because of the thermodynamic immiscibility of Mg in many systems. This technical issue may be solved by the application of severe plastic deformation using high-pressure torsion (HPT). In this study, a new Mg-rich ternary alloy Mg4NiPd was designed and prepared successfully by HPT. Preliminary results indicate hydrogen absorption and desorption proceed at room temperature, suggesting a new approach to design and prepare Mg-based alloys exceed the scope of known equilibrium phase diagrams for room temperature hydrogen storage.

Authors : A.G. Kvashnin, I.A. Kruglov, D.V. Semenok, A.R. Oganov
Affiliations : Skolkovo Institute of Science and Technology, Skolkovo Innovation Center 121205, 3 Nobel Street, Moscow, Russia, Moscow Institute of Physics and Technology, 141700, 9 Institutsky lane, Dolgoprudny, Russia; Dukhov Research Institute of Automatics (VNIIA), Moscow 127055, Russia, Moscow Institute of Physics and Technology, 141700, 9 Institutsky lane, Dolgoprudny, Russia; Skolkovo Institute of Science and Technology, Skolkovo Innovation Center 121205, 3 Nobel Street, Moscow, Russia; Skolkovo Institute of Science and Technology, Skolkovo Innovation Center 121205, 3 Nobel Street, Moscow, Russia; Dukhov Research Institute of Automatics (VNIIA), Moscow 127055, Russia, Moscow Institute of Physics and Technology, 141700, 9 Institutsky lane, Dolgoprudny, Russia, Northwestern Polytechnical University, Xi'an, 710072, China;

Resume : Hydrogen-rich hydrides attract great attention due to recent theoretical [1] and then experimental discovery of record high-temperature superconductivity in H3S (TC = 203 K at 155 GPa [2]). Here we perform a systematic evolutionary search for new phases in the Fe-H [3], Th-H [4], U-H [5] and other numerous systems under pressure [6] in order to predict new materials which are unique high-temperature superconductors. We predict new hydride phases at various pressures using the variable-composition search as implemented in evolutionary algorithm USPEX [7-9]. Among the Fe-H system two potentially high-TC FeH5 and FeH6 phases in the pressure range from 150 to 300 GPa were predicted and were found to be superconducting within Bardeen-Cooper-Schrieffer theory, with TC values of up to 46 K. Several new thorium hydrides were predicted to be stable under pressure using evolutionary algorithm USPEX, including ThH3, Th3H10, ThH4, ThH6, ThH7 and ThH10. Fm3 ̅mThH10 was found to be the highest-temperature superconductor with TC in the range 221-305 K at 100 GPa. Actinide hydrides show, i.e. AcH16 was predicted to be stable at 110 GPa with TC of 241 K. To continue this theoretical study, we performed an experimental synthesis of Th-H phases at high-pressures including ThH10. Obteined results can be found in Ref. [10]. Acknowledgments: Authors thank RFBR foundation № 19-03-00100. This work was supported by RFBR foundation № 19-03-00100 and facie foundation, grant UMNIK №13408GU/2018. References [1] D. Duan et al., Sci. Rep. 2018, 4, 6968. [2] A.P. Drozdov et al. Nature. 2015, 525, 73–76. [3] A.G. Kvashnin at al. J. Phys. Chem. C 2018, 122 4731-4736. [4] A.G. Kvashnin et al. ACS Applied Materials & Interfaces 2018, 10, 43809–43816. [5] I.A. Kruglov et al. Sci. Adv. 2018, 4, eaat9776. [6] D.V. Semenok et al. J. Phys. Chem. Lett. 2018, 8, 1920-1926. [7] A.O. Lyakhov et al. Comp. Phys. Comm. 2013, 184, 1172-1182. [8] A.R. Oganov et al. J. Chem. Phys. 2006, 124, 244704. [9] A.R. Oganov et al. Acc. Chem. Res. 2011, 44 227-237. [10] D.V. Semenok et al. 2019, arXiv:1902.10206.

18:00 Graduate Student Awards Ceremony and Reception (Main Hall)    

No abstract for this day

Symposium organizers
Claudio PISTIDDAHelmholtz Zentrum Hereon

Institute of Hydrogen Technology, Max Planck Strasse 1, Geesthacht 21502, Germany

Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
Kasper MØLLERCurtin University

(Funded by the Independent Research Fund Denmark), Kent St, Bentley 6102, WA, Australia
Michael HEERETechnische Universität Braunschweig

Institute of Internal Combustion Engines, Hermann-Blenk-Straße 42, 38108 Braunschweig, Germany