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Materials and devices for energy and environment applications


Functional hydride materials

Introduction and scope:

The proposed symposium will highlight the recent advances and new opportunities in hydride materials. In particular, the fundamental understanding and potential emerging applications of metal and non-metal hydrides as a function of their structure and stability will be discussed.

During the last two decades a vast amounts of investment and research has been placed into hydrides for vehicular and stationary hydrogen storage, battery, sensorial, energy-storage applications, and heterogeneous catalysis. As such a hydrogen economy has begun to flourish; hydrogen vehicles have been released to general public and off-grid hydrogen storage is widely available (ranging from individual power packs to community based power). Most recently, there has been a surge of scientific interest on the development of hydride-based tanks for the storage of hydrogen produced by renewable energy sources and for thermal energy storage, which can both produce electricity and supplement demand during times of short supply. Solid-state electrolytes and cells based on metal hydrides have thrived with the exploration of fast-ion conductors of which will shortly rival current battery technology in both voltage and capacity. Meanwhile, researchers are continuing to discover novel potential applications of hydrides and also conducting fundamental studies which further our understanding into hydrogen mobility, thermodynamic and kinetic processes and catalytic activity in metastable hydrides, etc.

Symposia at major international conferences, such as the E-MRS, enable the world’s leading researchers to network and present their work in front of their peers in a multi-disciplinary environment. The broad base of this conference offers researchers to listen to other state-of-the-art topics which allows them to identify new research areas and also provide input to other studies that would not be possible at niche conferences. 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 nanotechnological development. As such, the talks given by world-leading researchers in this symposium are bound to captivate a wide audience.

Hot topics to be covered by the symposium:

  • Fundamentals of hydride stability and hydride formation, nanostructuration of hydrides
  • Hydrides for hydrogen storage: theory and recent advances
  • Hydrides for energy storage applications: solid electrolytes, heat storage
  • Hydrides in catalysis, heterogeneous catalysis and photocatalysts
  • Changes in hydrides: sensors and photochromism
  • New and emerging applications: photovoltaics, thermoelectrics, etc.
  • Enabling applications: engineering challenges and perspectives

List of invited speakers:

  • Metal Hydride Based Optical Hydrogen Sensors - Bernard Dam
  • Understanding hydrogen storage properties of metal hydrides - Hyunjeong Kim
  • Table top time-resolved photoemission for hydride thin films and membranes  - Andreas Borgschulte
  • Hydrogen-induced phase transformations in single nanocrystals - Andrea Baldi
  • Metal hydrides in magnetism - Martin Sahlberg
  • New Perspectives in Multi-Component Hydrides - Anna-Lisa Chaudhary
  • Light metal hydride nanocomposites as room temperature solid electrolytes - Petra deJongh
  • Complex hydrides as fast ion conductors - Duncan Gregory

List of scientific committee members:

  • Craig Buckley (Curtin University, Australia)
  • Maximilian Fichtner (Universty of Ulm, Germany)
  • Bjørn Hauback (Institute for Energy Technology, Norway)
  • Michael Hirscher (Max Planck Institute for Intelligent Systems, Germany)
  • Björgvin Hjörvarsson (University of Uppsala, Sweden)
  • Andreas Züttel (Ecole Polytechnique Fédérale de Lausanne, Switzerland)
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Welcome and Keynote : Terry Humphries, Julia Rinck & Petra Agota Szilagyi
Authors : C. Boelsma, L. Bannenberg, M. J. van Setten*, A. A. van Well, P. Ngene^, R. Westerwaal, and B. Dam
Affiliations : Materials for Energy Conversion and Storage, Delft University of Technology, Delft, Netherlands; *Catholic University of Leuven, Louvain-la-Neuve, Belgium; ^Debye Institute of nanomaterials Science,Utrecht University, Netherlands

Resume : Pd films are classical materials for optical fiber hydrogen sensing due to the fact that hydrogen easily dissociates on Pd surfaces, while the optical bulk properties change on hydrogen absorption. These two functionalities are divided in Pd-capped metal hydride films, where the Pd takes care of the dissociative hydrogen adsorption while the optical change due to hydrogen chemisorption by the underlying layer is used as a measure for the surrounding hydrogen pressure. In this way, making use of the wide variability in the thermodynamic hydrogenation properties, both hydrogen sensors and hydrogen threshold detectors can be designed covering a wide range of pressures. Both plastic and elastic effects can be used to further modify the pressure range. In most cases, the sensors feature a large hysteresis due to the presence of first order phase transitions during hydrogenation. Only within a solid solution the optical response can be taken as a continuous, hysteresis-free measure of the hydrogen pressure. Still, due to the enthalpy of hydrogenation, the temperature dependent calibration is a complex matter. Here, we focus on Pd-capped transition metals showing an hysteresis-free, reproducible change in optical properties in response to a hydrogen exposure ranging over >6 orders of magnitude in pressure. In Hafnium, we find that a change in temperature results in a shift of the optical signal which is uniform over the whole pressure range. This unique feature indicates that the hydrogenation enthalpy is independent of the hydrogen concentration. In contrast, the large pressure range attained within a small hydrogen fraction range suggest a strong dependence of the entropy of hydrogenation on the hydrogen content. While this effect is poorly understood it allows for the development of a sensitive, hysteresis-free and calibration-free hydrogen sensor. The sensing materials are implemented in various layouts ranging from optical fiber micro-mirrors, to surface plasmon based and even include eye-readable disposables. Finally, to use these materials in practical applications, the Pd has to be protected against poisoning. We will show that such protection layers enhance the lifetime of these sensors and even allow for the measurement of the fraction of dissolved hydrogen in liquids.

Changes in hydrides: sensors and photochromism i : Andreas Borgschulte
Authors : F. Nafezarefi, S. Cornelius, E. ten Have, H. Schreuders and B. Dam
Affiliations : Delft University of Technology, Department of Chemical Engineering, Materials for Energy Conversion and Storage, Julianalaan 136, NL-2628BL Delft, The Netherlands

Resume : Approximately 40% of the global energy consumption is spent on purposes of heating, cooling and lighting of buildings. Windows account for the vast proportion of the energy losses associated with the solar heat influx surplus through the façade area. Therefore, there is a huge potential for energy saving by means of smart window technology having the ability to adapt to the change of external conditions during the day. A possible way to realize such windows is the use of photochromic materials. Photochromism by definition is a reversible change of optical properties on exposure to light. Recently, a new material, Yttrium-oxy-hydride (YOxHy), has been added to the family of inorganic photochromic materials. Thin films of YOxHy show color-neutral switchable optical properties upon illumination by UV and/or visible light at ambient conditions. In our study, we have developed a setup of optical filters and different light sources to evaluate the temporal and spectral behaviour of YOxHy. The results indicate that the photochromic activation process requires photon energies above the band gap, indicating that the creation of an electron-hole pair plays an important role in the photochromic mechanism. Furthermore, we find that illumination of a photo-darkened sample with photons having an energy lower than the band gap enhances the speed of relaxation. Consequently, the spectral shape of the light source determines the activation rate and magnitude. Accordingly, we will discuss the reproducibility of the photochromic effect and estimate the maximum performance.

Authors : J. Montero, F. Martinsen, S. Zh. Karazhanov , E. S. Marstein
Affiliations : Institute for Energy Technology, P.O. Box 40, NO-2027 Kjeller, Norway

Resume : Oxygen containing yttrium hydride (YHx) thin films exhibit photochromic (PC) behaviour, i.e., the reversible change in their optical properties when illuminated with light of adequate wavelength and intensity. This feature has attracted much attention due to its wide range of technological applications including smart windows, sensors or any other device in which a response to energetic light is required. However, the mechanism responsible for the PC change in YHx is still not well understood. The objective of the present work is to shed some light on the photochromic mechanism by using an optical approach. On this basis, oxygen containing YHx thin films exhibiting different stoichiometry and different optical and electrical properties have been prepared onto glass substrates by pulsed magnetron sputtering. Then, the obtained films were characterized by optical measurements (transmittance, reflectance and ellipsometry) in both, their clear and photodarkened state. Additional characterization by XRD, SEM and EDS was also performed. A detailed study of the optical properties of the photodarkened films suggested the formation, upon illumination, of optically-absorbent domains diluted within the transparent YHx matrix.

Authors : S. Cornelius1), F. Nafezarefi1), E. ten Have1), H. Schreuders1), and B. Dam1)
Affiliations : 1) Delft University of Technology, Department of Chemical Engineering, Materials for Energy Conversion and Storage, Julianalaan 136, NL-2628BL Delft, The Netherlands

Resume : Among the class of chromogenic materials, photochromic materials offer the possibility of passive reversible switching of optical properties in direct response to changes in solar irradiance in the course of the day. Photochromic devices are inherently more simple than electrochromic ones and they can outperform thermochromic VO2 based materials in terms of modulation of visible light transmittance. Therefore, photochromic materials are interesting candidates for smart window and solar control applications. However, most established photochromic materials are organic compounds with narrow absorption bands and susceptibility to humidity/oxygen, which requires blending of multiple compounds and additional encapsulation to achieve color-neutrality and enhance the lifetime. Recently, it was demonstrated that Yttrium-oxy-hydride (YOxHy) based thin films show an unusual visible-light-induced and nearly color-neutral photochromic effect at ambient conditions. However, the material properties, performance limits and the nature of the reversible photochromic effect of YOxHy are not well understood until now. These aspects will be addressed based on a combination of magnetron sputter deposition with dynamic UV/VIS optical spectroscopy, X-ray diffraction as well as ion beam analysis methods. Despite the structural similarity between metallic Y-dihydride and YOxHy, the latter is found to be a wide band gap insulator where the photon energy threshold for the photochromic effect is related to the optical band gap. Experimental concepts of bandgap engineering leading to a tunable photochromic response will be introduced.

Changes in hydrides: sensors and photochromism ii : Bernard Dam
Authors : S.W.H. Eijt (1), M.P. Plokker (1), H. Schut (2), F. Naziris (1), S. Cornelius (3), F. Nafezarefi (3), H. Schreuders (3), E.F.E. ten Have (3), and B. Dam (3)
Affiliations : (1) Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft, The Netherlands; (2) Neutron and Positron Methods in Materials, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft, The Netherlands; (3) Materials for Energy Conversion and Storage, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, NL-2628 BL Delft, The Netherlands

Resume : The addition of oxygen during reactive magnetron sputter deposition of yttrium hydride films leads to photochromism in the resulting YOyHx films, exhibiting pronounced changes in the optical, electronic and structural properties upon illumination with UV light. In order to unravel the mechanism of the photochromic effect, positron annihilation Doppler broadening spectroscopy was applied to probe the electronic structure and the presence of vacancies in thin film yttrium oxyhydrides and related materials as a function of composition, UV illumination and thermal annealing. The Doppler S and W parameter depth profiles of a series of Y, YH2, Y2O3 and YOyHx thin films on f-SiO2 or c-Si substrates show strong systematic changes in S and W, caused by distinct differences in the electronic structure of Y, YH2 (metals), Y2O3 (insulator) and YOyHx (semiconductor with a bandgap of 2.5 eV). Thermal annealing for 16 hours at 375 K leads to a substantial increase in the Doppler S parameter, pointing to either the formation of vacancies by hydrogen release or the formation of metallic yttrium clusters. Simultaneously, the optical band gap increases. This indicates a direct correlation between the changes in optical properties and the structural properties. The sample chamber of the Doppler broadening setup was redesigned and tested in order to enable positron annihilation studies of the photochromic effect in YOyHx films during in-situ UV illumination, and first results will be reported.

Authors : F. A. Martinsen, J. Montero, S. Zh. Karazhanov, E. S. Marstein, B. C. Hauback
Affiliations : Institute for Energy Technology, P.O. Box 40, NO-2027 Kjeller, Norway - All Department of Material Science, National Research Nuclear University, Moscow, Russia - S. Zh. Karazhanov

Resume : Oxygen containing YHx-based thin films have been shown to possess photochromic (PC) properties. Upon illumination with highly energetic light (UV), the material transforms from its transparent state into an opaque state, a transition that reverses upon removal of the light. This property makes the material highly attractive for incorporation in smart fenestration where is can be used to control the solar heat gain through the windows - allowing for a reduction of unwanted heating in buildings from direct sunlight - but also to reduce glare on sunny days. In this work we have studied the optical as well as photochromic properties of oxygen containing yttrium hydride prepared on glass using reactive magnetron sputtering. The dynamics of the photodarkening process have been studied where films were shown to darken as much as 30-40 % absolute upon illumination, with a darkening and recovery time dependent on light intensity. Stability measurements have been conducted where photochromic films under cyclic illumination over a period of 72 hours show no measurable degradation in their photochromic properties. Our tests conclude that photochromic oxygen containing yttrium hydride is a good candidate for achieving low cost high performance photochromic coating for the next generation of smart windows.

New methods of analysis : Stephan Eijt
Authors : Hyunjeong Kim
Affiliations : National Institute of Advanced Industrial Science and Technology

Resume : Among many types of currently available hydrogen storage materials, metal hydrides are the only materials that can reversibly absorb a large amount of hydrogen in ambient conditions. However, for practical applications, several material challenges still remain to be tackled. Various new ideas and approaches have been proposed and tested in an effort to improve the properties of currently available metal hydrides. To develop highly efficient materials it is important to thoroughly understand what, especially which structural feature, really gives rise to material properties of interest. Many interesting properties often arise from nano or heavily disordered structural features that are difficult to characterize using the conventional crystallographic technique alone. By using the atomic pair distribution function (PDF) analysis, a powerful local structural probing technique, we have investigated various types of metal hydrides to elucidate structural features closely linked to their properties. Some of the examples include heavily disordered vanadium-based alloys, Mg-Ti thin films and nano-confined materials. These materials possess an intricate structure and it is quite challenging to obtain structural information. In this talk, I will show how their structural information is extracted from the PDFs and how it is used to understand the hydrogen storage properties of these materials.

Authors : Olga Sambalova, Renaud Delmelle, Francesco Barbato, Claudio Cirelli, Bruce D. Patterson, Davide Bleiner, Peter Ngene, Bernard Dam, Andreas Borgschulte
Affiliations : Laboratory for Advanced Analytical Technologies, Swiss Federal Laboratories for Materials Science and Technology (Empa), Überlandstrasse 129, CH-8600 Dübendorf, Switzerland; Inorganic Chemistry and Catalysis Debye Institute for Nanomaterials Science, Utrecht University Universiteitsweg 99, 3584 CG Utrecht (The Netherlands); Department of Chemical Engineering Materials for Energy Conversion and Storage, Delft University of Technology Julianaweg 136, 2628 BL Delft (The Netherlands)

Resume : In order to improve materials for technical heterogeneous catalysis, one requires analytical tools capable of giving insights into the surface chemistry of a multiplicity of molecular systems. Time-resolved photoemission at near-ambient pressure (20 mbars), typically performed at synchrotron sources, can provide these insights. Its application is usually reserved to ”flagship” projects, due to the huge effort of the corresponding instrumentation and operation. Here we present a new experimental approach to study materials exposed to high hydrogen “pressures” by means of XPS, which is compatible with a small, laboratory-based installation. Instead of exposing the sample under investigation to gaseous hydrogen, the sample is in contact with a hydrogen permeation membrane, through which hydrogen is transported from the outside to the sample as atomic hydrogen. Thereby, we can reach local hydrogen concentrations at the sample inside a UHV chamber, which correspond to hydrogen pressures up to 1 bar, without affecting the sensitivity or energy resolution of the attached electron spectrometer. A success story of the method is the development of new hydrogen-selective membranes. We have demonstrated that the hydrogen desorption from Pd is significantly improved by a nm PTFE layer, which dramatically enhances the overall permeability of the membrane. The measured time-dependence of the atomic hydrogen flux is interpreted by models of surface reac-tions, but need to be experimentally confirmed by an equally fast time-resolved probe of the surface chemistry. For this we are developing a table-top pulsed laser-plasma source providing EUV-photons for (ns) time-resolved photoemission. We discuss the concept in particular in the frame of hydride thinfilms. References [1] R. Delmelle, B. Probst, R. Alberto, A. Züttel, D. Bleiner, A. Borgschulte, Rev. Sci. Instrum. 2015, 86, 053104. [2] R. Delmelle, P. Ngene, B. Dam, D. Bleiner, and A. Borgschulte, ChemCatChem, in press (2016).

Poster session : Petra Agota Szilagyi
Authors : Soung Soo Yi, Kiwan Jang, Dong-Soo Shin, Jong Won Jeong, Jung Hyun Jeong
Affiliations : Silla University; Changwon National University; Changwon National University; Changwon National University;Pukyong National University

Resume : A novel POSS type monomer ligand ‘‘2,6-pyridinediaminebis-(propanylheptaisobutyl POSS)’’ (PDC-POSS) were prepared and utilized in the preparation of potential luminescent hybrid complex Er-PDC-POSS with an inner transition metal Er3+ ions. The solubility and photoluminescence properties of new Er-PDC-POSS hybrid material were studied. The precursor PDC-POSS was synthesized by treating (3-aminopropyl) heptaisobutyl POSS with PDC (2,6-pyridinedicarboxylic acid chloride), and then coordinated with Er3+ using erbium nitrate to afford Er-PDC-POSS hybrid material. The erbium-doped hybrid material was characterized using fourier transform infrared spectroscopy, and scanning electron microscopy along with energy dispersive X-ray analysis. The photoluminescence properties were studied using a fluorescence spectrophotometer in which, the results showed enhancement in emission peaks at 545 and 656 nm for Er-PDC-POSS, when compared to that of a known solgel-based material Er-PDC-solgel.

Authors : M. Szkoda(1), A. Lisowska-Oleksiak(1), J. Karczewski(2), J. Ryl(3), K. Siuzdak(4)
Affiliations : (1) Faculty of Chemistry, Gdansk University of Technology, Narutowicza 11/12, 80-233, Gdansk, Poland; (2) Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland; (3) Department of Electrochemistry, Corrosion and Materials Engineering, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland (4) Center for Plasma and Laser Engineering, The Szewalski Institute of Fluid Flow Machinery, ul. Fiszera 14, 80-231 Gdansk, Poland

Resume : Over the last several years, there has been a great deal of interest in conducting polymer films on meatal oxide support due to the prospects of their applications as intercalating systems in advanced batteries, supercapacitors, gas separating membranes, sensors and microelectronic devices. Conductive polymers are characterized by high electrical capacitance and cyclability, however, they have a narrow potential range of electrochemical activity and stability. The increase of potential window and improvement of specific capacitance can be achieved e.g. by fabrication of organic-inorganic heterojunction with TiO2 or by the introduction of Prussian blue analogues acting as a redox center. Here, the method of preparation of inorganic-organic heterojunction where hydrogenated titania nanotubes are infiltrated by poly(3,4-ethylenedioxythiophene) containing redox centres formed by various transition metals hexacyanoferrates network Mehcf (Me: Fe, Ni, Cu, Co) is presented. Inorganic-organic hybrids were characterized using Raman spectroscopy technique and FTIR-ATR measurements. The morphology of obtained materials were inspected using SEM and the presence of transition metal was confirmed by XPS. The composite material exhibits reversible redox activity and much higher photoactivity in comparison to pristine H-TiO2. Financial support from the National Science Center (2012/07/D/ST5/02269) is gratefully acknowledged.

Authors : Andreas Züttel, Jeremie Berard, Mariana Spodaryk
Affiliations : Laboratory of Materials for Renewable Energy (LMER) Institute of Chemical Sciences and Engineering (ISIC) Basic Science Faculty (SB) École polytechnique fédérale de Lausanne (EPFL) Valais/Wallis Energypolis Rue de l’Industrie 17, CP 440 CH-1951 Sion, Switzerland

Resume : A small scale demonstrator was built in order to demonstrate the closed hydrocarbon cycle for the storage of renewable energy. Solar energy is converted with four different types of photovoltaic cells (single crystal Si, polycryst. Si, CGIS thin film, and Grätzel cells) in horizontal (10°) and in 30° inclination mounted on the roof of Energypolis.The electricity is stored in metal hydride and lead acid batteries. An electrolyzer converts electricity into hydrogen and a metal hydride compressor increases the pressure of the hydrogen gas and submits the hydrogen to a metal hydride storage. Finally the hydrogen reduces CO2 absorbed from the atmosphere to methane and methanol. The demonstrator is used as a platform for the investigation of new materials and processes on a lab scale. Furthermore, the demonstrator creates a database of energy flows and energy stored under real conditions as an empirical basis used for the system modeling. Last but not least the demonstrator is virtually presented on the web where all the data collected becomes public.

Poster session 2 : Terry Humphries
Authors : Y. Solonin 1, O. Galiy 1, K. Pershina 2, K. Kazdobin 2
Affiliations : 1- Frantsevich Institute for Problems of Material Sciences, NAS Ukraine 3, Krzhyzhanovsky str., Kyiv, 03680, Ukraine 2 -Vernadsky Institute of General and Inorganic Chemistry NAS Ukraine 32/34 Palladin avenue, Kyiv, 03680, Ukraine e-mail:

Resume : The AB2 type Zr- based multicomponent Laves phase alloys have very promising properties in the nickel-metal hydride batteries due to their large discharge capacity and relatively long cycle life. The possibility of reducing the activation period and increase the electrochemical capacity of zirconium alloy electrodes of AB2 type via oxidation on air is proved by the methods of X-ray Photoelectron Spectroscopy, Voltammetry and Electrochemical Impedance Spectroscopy on the example of ZrMnCrNiV alloy. The improvement of charge - discharge characteristics of zirconium alloys results from the fine distribution of nickel oxide forms in the surface of the composite and increase of the alloy interface. It results in better homogeneity of the oxide film, providing the formation of quasi-homogeneous reaction space at the electrode - electrolyte interface.

Authors : Petra Agota Szilagyi
Affiliations : University of Greenwich

Resume : Pressure-induced structural changes in ammonia borane analogues as potential hydrogen-storage materials Petra Ágota Szilágyi University of Greenwich With the increasing demands on fossil fuels, many industrialised nations are turning towards alternative sources of energy. The “hydrogen economy”, in which hydrogen is used as a “green” feedstock in fuel cells to power motor vehicles, homes, etc., has been highlighted as a potential solution to the energy problem. Challenges to be faced before this becomes a reality include the development of sustainable methods of hydrogen production that do not involve fossil fuels, and the safe and reversible storage of hydrogen. This second aspect has been highlighted in a recent article that reviews the methods currently being developed for hydrogen storage.[1] Several promising areas have been identified, especially in the use of solid hydrogen-containing materials. The performance and properties of these materials can depend heavily on structure and so the correlation of structural studies with physico-chemical properties is of key importance. Some of the B-N hydrides [2,3] contain very high hydrogen content. For instance, ammonia borane (NH3BH3) contains 19.6 wt% hydrogen, which can be partially delivered at temperatures up to 130 ˚C.[4] Other B-N hydrides include the NH3BH3 analogues of methyl- and dimethylamine borane[5,6], the hydrazine monoborane and the explosive hydrazine diborane[7,8]. Because of the interest in ammonia borane as a potential hydrogen-storage material and the presence of both protic N-H and hydridic B-H bonds, forming N-H…H-B dihydrogen bonds, this system has been extensively studied under pressure with a range of spectroscopic, structural and computational methods and several phase transitions have been identified.[9-16] In spite of the similar structural features present in the solid state of the ammonia borane analogues, they have never been studied under pressure. The behaviour of some of the ammonia borane analogues under external pressure is discussed in this work: our Raman spectroscopy and powder X-ray diffraction studies led us to identify a pressure-induced phase transition for the dimethylamine borane and structural changes triggered by the compression of the methylamine borane have also been observed. 1 A.W.C. van den Berg and C. Otero Areán, Chem. Commun. 2008, 668 2 T. B. Marder et al. Angew. Chem. Int. Ed. 2007, 46, 8116 3 F. H. Stephens et al. Dalton Trans. 2007, 2613 4 F. Baitalow et al. Thermochim. Acta 2002, 391, 159 5 D. J. Grant et al. J. Phys. Chem. A, 2009, 113, 6121 6 C-H. Sun et al. Phys. Chem. Chem. Phys. 2008, 10, 6104 7 N. Vinh-Son et al. Phys. Chem. Chem. Phys. 2009, 11, 6339 8 T. Hügle et al. J. Am. Chem. Soc. 2009, 131, 7444 9 S. Trudel, D.F.R. Gilson, Inorg. Chem. 2003, 42, 2814 10 Y. Lin et al. J. Chem. Phys. 2008, 129, 234509; 11 Ravhi S. Kumar et al., Bull. Am. Phys. Soc. 2009, 54(1), W23.0001 12 Y. Filinchuk et al. Phys. Rev. 2009, B 79, 214111 13 P. Vajeeston et al. J. Alloy. Compd. 2005, 387, 97 14 Ravhi S. Kumar et al., Chem. Phys. Lett. 2010, 495, 203 15 Ravhi S. Kumar et al. Chem. Phys. Lett. 2008, 460, 442 16 Ravhi S. Kumar et al. J. Phys. Chem. B, 2008, 112, 8452

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Hydrides for thermal energy storage : Petra Agota Szilagyi
Authors : Patrick A. Ward, Joseph A. Teprovich Jr., Ted Motyka, Claudio Corgnale, Bruce Hardy, Ragaiy Zidan
Affiliations : Savannah River National Laboratory Patrick A Ward; Joseph A. Teprovich Jr.; Ted Motyka; Bruce Hardy; Ragaiy Zidan; Claudio Corgnale Greenway Energy LLC Patrick A. Ward; Claudio Corgnale

Resume : Solar electromagnetic radiation is a highly underutilized sustainable energy source capable of providing large amounts of energy if appropriately exploited. Concentrated solar thermal power plants aim at utilizing the majority of the solar irradiance spectrum by concentrating the solar energy to produce heat. In order to maintain electricity generation overnight, an appropriate thermal energy storage system is required. Practical thermal energy storage systems require low cost which in turn demands high efficiencies, low cost materials, and long term stability of the thermal energy storage system. In order to achieve high efficiencies of the thermal energy storage system, high operating temperatures are desired (≥ 600 °C). Thermal energy storage systems for concentrated solar power fall into three different categories including sensible heat, latent heat, and thermochemical heat. Thermochemical heat storage systems have the advantage of much higher energy densities than systems based on sensible or latent heat materials. Metal hydrides have recently gained interest as thermochemical energy storage materials due to the high enthalpy associated with hydrogenation of many hydrides. Herein, we describe a metal hydride based thermal energy storage system based on Calcium Aluminum alloys. Calcium Aluminum alloys provide a solution to many of the challenges associated with the high temperature metal hydride required for metal hydride base thermal energy storage systems. Calcium aluminum can be operated at 600 °C to reversibly produce CaH2/Al and the CaAlx alloy by manipulation of the hydrogen overpressure. The use of calcium hydride for this application is impractical due to corrosion of the molten hydride, very low equilibrium pressures, and volatility of calcium at the desorption temperatures. The addition of aluminum allows for the tuning of the thermodynamic properties to give appropriate equilibrium pressures for pairing with a suitable low temperature metal hydride and also prevents the corrosion associated with molten CaH2. The thermodynamic properties of CaAlx alloys and appropriate low temperature metal hydride pairs are presented.

Authors : Terry D. Humphries, Drew A. Sheppard, Matthew R. Rowles, M. Veronica Sofianos and Craig E. Buckley
Affiliations : Hydrogen Storage Research Group, Fuels and Energy Technology Institute, Curtin University, GPO Box U1987, Perth, WA 6845, Australia

Resume : Metal hydrides have long been explored for their potential application in a variety of technological applications including hydrogen storage materials for energy applications, fast-ion conductors and sensors. For thermal energy storage, such as concentrating solar thermal energy storage, metal hydrides are required to operate at temperatures in excess of 500 °C [1]. This temperature is too high for even the more stable, reversible hydrogen storage materials, and as such, work has been undertaken to synthesise metal hydrides that are stable and reversible at these high temperatures. One proven strategic method to stabilise these materials is to substitute fluorine atoms for hydrogen [2]. Fluorides are more stable than their hydride equivalents and this can be exploited to increase the stability of various metal hydrides by partially substituting hydrogen for fluorine. One recent example is the NaMgH3-xFx system, where pure NaMgH3 releases H2 at ~400 °C, whereas NaMgH2F decomposes at ~478 °C [3]. More recently, NaH1−xFx solid solutions have been synthesised from stoichiometric mixtures of NaH and NaF and their physical properties determined by in situ powder XRD, pressure-composition-isotherm (PCI) and temperature-programmed-desorption (TPD) measurements [4]. Decomposition, under reduced pressure, is observed at 443 °C for NaH0.5F0.5 compared to 408 °C for pure NaH, while a ΔHdes of 106 ± 5 kJ/mol.H2 and ΔSdes of 143 ± 5 J/mol.H2/K was established by PCI analysis (compared to ΔHdes of 117 kJ/mol.H2 and ΔSdes of 167 J/mol.H2/K for pure NaH [5]). This indicates that the reduced operating pressure/temperature of NaH1-xFx is primarily driven by changes in entropy induced by fluorine substitution). Theoretically, these materials may operate between 470 − 775 °C and as such, these low-cost materials show great potential as thermal energy storage materials for concentrating solar thermal power applications. To demonstrate their viability, cycling studies prove that NaH0.5F0.5 is stable over at least seven hydrogen sorption cycles, with only a slight decrease in capacity while operating between 470 and 520 °C. References 1. D. A. Sheppard, M. Paskevicius, T. D. Humphries, M. Felderhoff, G. Capurso, J. Bellosta von Colbe, M. Dornheim, T. Klassen, P. A. Ward, J. A. Teprovich, C. Corgnale, R. Zidan, D. M. Grant and C. E. Buckley, Appl. Phys. A, 2016, 122, 395. 2. D. A. Sheppard, T. D. Humphries and C. E. Buckley, Mater. Today, 2015, 18, 414. 3. D. A. Sheppard, C. Corgnale, B. Hardy, T. Motyka, R. Zidan, M. Paskevicius and C. E. Buckley, RSC Adv., 2014, 4, 26552. 4. T. D. Humphries, D. A. Sheppard, M. R. Rowles, M. V. Sofianos and C. E. Buckley, 2016, Unpublished results. 5. F. D. Manchester and A. San-Martin, Phase Diagrams of Binary Hydrogen Alloys, ASM International, Ohio, 2000.

Hydrogen storage in composites and alloys : Torben R. Jensen
Authors : C. Milanese, A. Girella, G. Valsecchi, A. Marini, M. Gaboardi, D. Pontiroli, G. Magnani, M. Riccò
Affiliations : Pavia Hydrogen Lab, C.S.G.I. & Chemistry Department, University of Pavia, Viale Taramelli 16, 27100 Pavia, Italy Carbon Nanostructures Lab, Department of Physics and Earth Sciences, University of Parma, Parco Area delle Scienze 7/A, 43124 Parma, Italy

Resume : Alkali-cluster intercalated fullerides 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. The structural properties were clarified by means of in-situ neutron diffraction and the analysis of the Pair Distribution Function (PDF) obtained from high-energy synchrotron diffraction. The mechanism of hydrogenation was unveiled by Muon Spin Relaxation spectroscopy (μSR). By coupled manometric - calorimetric analyses and thermogravimetric measurements, we proved that C60 covalently binds up to 5 wt% H2 at moderate temperature and pressure, thanks to the catalytic effect of the intercalated alkali clusters. Recently, we also identified some strategies to further improve the absorption performance in this class of materials. For example, we succeeded to catalyze Li-fullerides with Pt and Pd nanoparticles, whose known activity towards hydrogen dissociation allows increasing the H2 absorption up to 5.9 wt% H2 and the absorption rate of about 35 % with respect to the pure compound.

Authors : Adlane SAYEDE1, Gauthier LEFEVFRE1 and Holger Kohlmann2
Affiliations : 1Université d’Artois, Unité de Catalyse et de Chimie du Solide (UCCS), UMR CNRS 8181, Rue Jean Souvraz, SP 18, 62307 Lens Cedex, France 2Inorganic Chemistry, Leipzig University, Johannisallee 29, 04103 Leipzig, Germany

Resume : Hydrogen is a promising energy carrier, compatible with the sustainable energy concept. Generally, hydrogen is stored either in high pressure tanks or in liquid form in cryogenic tanks. These forms of storage are not suitable for widespread commercial application. For example, a hydrogen fuel cell car needs to store at least 4 kg hydrogen to match the range of a gasoline-powered car! The promising alternative is to use solid materials for hydrogen storage. Indeed, it has been known for more than a century that hydrogen can be stored reversibly in metals such as Pd. Knowledge about the ground-state crystal structure is a prerequisite for the rational understanding of solid-state properties of hydrogen storage materials. To act as an efficient energy carrier, hydrogen should be absorbed and desorbed in materials easily and in high quantities. Owing to the complexity in structural arrangements and difficulties involved in establishing hydrogen positions by x-ray diffraction methods, the structural information of hydrides are very limited compared to other classes of materials (like oxides, etc.). This can be overcome by conducting computational simulations combined with selected experimental study which can save environment, money, and man power. In this work, the results of evolutionary algorithm calculations, within the first-principles framework of density functional theory (DFT), performed on palladium-arsenic system and their hydrides are presented. The obtained results show excellent correlation with the experimental results. Moreover, new hypothetic stable hydride structure, experimentally unknown, was predicted.

Authors : Henrietta W. Langmi1, Nicholas M. Musyoka1, Sonwabo Bambalaza1, Jianwei Ren1, Mkhulu Mathe1, Dmitri Bessarabov2
Affiliations : 1HySA Infrastructure Centre of Competence, Materials Science and Manufacturing, Council for Scientific and Industrial Research (CSIR), PO Box 395, Pretoria 0001, South Africa 2HySA Infrastructure Centre of Competence, Faculty of Engineering, North-West University (NWU), P. Bag X6001, Potchefstroom 2520, South Africa

Resume : The attractiveness of metal-organic frameworks (MOFs) for hydrogen storage is derived from the high surface area and tunability of their pore structure. Carbon materials such as templated carbons and graphene have also been identified as having attractive properties for hydrogen storage. For instance, graphene is considered promising for hydrogen storage due to its many interesting features such as high mechanical strength, lightweight, and high thermal and electrical conductivity. Synthesis of MOF/carbon composite materials has the potential of tapping into the attractive properties of the individual carbon and MOF materials. In this study, hybrid composites of zeolite templated carbon (ZTC) and Cr-MOF (MIL-101), as well as reduced graphene oxide (rGO) and Zr-MOF (UiO-66) were synthesised and analysed using various techniques such as SEM, XRD, BET, and also tested for hydrogen uptake. Rather than follow the conventional method of physical mixing, our synthesis strategy involved an in situ method of incorporating the carbon material into the synthesis mixture of the MOF. The results showed that the surface areas and the hydrogen uptake capacities of individual MIL-101, ZTC, and UiO-66 could be enhanced when the hybrids MIL-101/ZTC composite and UiO-66/rGO composite were synthesized. The incorporation of ZTC and rGO was found not to interfere with the crystallization of the MOF materials. While some MIL-101 crystals were observed to have grown on the surface of the ZTC, in the other hybrid material, Zr-MOF crystals were able to form between the graphene sheets. This intergrowth characteristic is expected to induce graphene’s intrinsic properties to the MOF materials such as enhanced thermal conductivity which is a favorable property during the design of a hydrogen storage system.

Hydrides: fundamentals : Andreas Zuttel
Authors : Andrea Baldi, Tarun Narayan, Ai Leen Koh, Robert Sinclair, Jennifer Dionne
Affiliations : Dutch Institute for Fundamental Energy Research (DIFFER); Stanford University; Stanford University; Stanford University; Stanford University;

Resume : Many energy and information storage processes rely on phase changes of nanostructured materials in reactive environments. In ensemble studies of these materials, it is however often difficult to discriminate between intrinsic size-dependent properties and effects due to sample size and shape dispersity. Here, we use in-situ transmission electron microscopy to show the first direct measurement of hydrogen-induced phase transitions in colloidally-synthesized palladium nanocrystals, both at the single particle level [1] and within individual nanosized particles [2]. The combination of nanoscale spectroscopy and imaging with single-particle diffraction in an environmental TEM offers unprecedented insight into the phase transition of nanomaterials and can be extended to the study of a variety of processes, from ion intercalation in battery materials to nanoparticle degradation in heterogeneous catalysis. [1] A. Baldi, T. C. Narayan, A. L. Koh, and J. A. Dionne, Nature Materials 13, 1143-1148 (2014) [2] T. C. Narayan, A. Baldi, A. L. Koh, R. Sinclair, and J. A. Dionne, Nature Materials AOP (2016)

Authors : Martin Sahlberg
Affiliations : Department of Chemistry - Angström Laboratory, Uppsala University, Sweden e-mail:

Resume : The use of hydrogen absorption to tune the magnetic properties of alloys and compounds has a long and prosperous history. From the use of hydrogen processing of high performance permanent magnets [1] to tuning the Curie temperature of magnetocaloric materials [2], hydrogen absorption has been important in the development of the modern magnetic material. The magnetic properties of a material are given by the electronic structure. The interaction between unpaired electrons in different ways can yield different magnetic behaviour from the simple ferromagnets to more complex interaction like magnetic frustration and spin ice. Hydrogen incorporation in magnetic materials provides a unique possibility to probe the electronic structure and provide insight into the interplay between chemical bonding and magnetic properties. In particular, itinerant electrons may be localized as H- through the formation of interstitial hydrides. This generally leads to a change of the strength and possibly also the sign of the magnetic interaction. During this lecture, I will give a general introduction to magnetism in general as well as the field of metal hydrides in magnetism, followed by a discussion of some recent results from my group [3] and others. The talk will finish with some perspectives, challenges and the future prospects of this research field. References 1. Harris, I.R. and P.J. McGuiness, Hydrogen: its use in the processing of neodymium-iron-boron-type magnets. J Less-Common Met, 1991. 174(1-2): p. 1273-1284. 2. Fukamichi, K., A. Fujita, and S. Fujieda, Large magnetocaloric effects and thermal transport properties of La(FeSi)13 and their hydrides. Journal of Alloys and Compounds, 2006. 408–412: p. 307-312. 3. Angström, J., et al., Hydrogenation-Induced Structure and Property Changes in the Rare-Earth Metal Gallide NdGa: Evolution of a [GaH]2– Polyanion Containing Peierls-like Ga–H Chains. Inorganic Chemistry, 2016. 55(1): p. 345-352.

Complex hydrides i : Anna-Lisa Chaudhary
Authors : Torben R. Jensen
Affiliations : Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark.

Resume : Hydrogen is recognized as a potential and extremely interesting energy carrier [1], which can facilitate efficient utilization of unevenly distributed renewable energy. Furthermore, hydrogen has an also an extremely interesting chemistry and form compounds with most elements in the periodic table and with a variety of different types of bonds. Here we report selected recent results within new hydrogen containing materials: (i) synthesis of novel metal borohydrides and studies of their properties for hydrogen storage or as ion conductors, (ii) tailoring materials properties by formation of eutectic melting systems, and (iii) in situ powder X-ray diffraction studies of hydrogen release and uptake reactions. We also demonstrate that structural dynamics in the solid state, i.e. entropy effects, are of extreme importance for detailed material property analysis. We present a ‘paddle wheel’ mechanism, which may be responsible for fast ionic conductivity [2]. Entropy effects may also be responsible for anion substitution, which mainly occur in some polymorphs. We conclude that the chemistry of hydrides is very divers, towards rational design of multi-functional materials [3], including new ion-conductors for batteries, hydrogen storage materials, and possibly materials with new types of optical properties. [1] Ley, et al, Mater. Today 17(3), 122 (2014) [2] Skripov, et al., J. Phys. Chem. C 117, 14965 (2013) [3] Schouwink, et al, Nature Comm., 5, 5706 (2014)

Authors : C. Milanese, I. Saldan, A. Girella, G. Valsecchi, P. Cofrancesco, A. Marini M. Rueda Noriega, Luis Miguel Sanz-Moral, A. Martin, D. Pontiroli, M. Gaboardi, G. Magnani, M. Riccò
Affiliations : Pavia Hydrogen Lab, Chemistry Dept., C.S.G.I. & University of Pavia, Italy; High Pressure Processes Group, Chemical Engineering and Environmental Technology Dept., University of Valladolid, Spain; Carbon Nanostructures Lab, Physics and Earth Science Dept., University of Parma, Italy

Resume : Magnesium borohydride is a very high-capacity hydrogen complex hydrides (14.84 wt% of H2) although its H2 sorption reversibility remains a challenge. Thermodynamics of Mg(BH4)2 dehydrogenation is calculated to be near ideal for effective hydrogen storage, but experiments reveal competing decomposition pathways with the formation of very stable intermediates limiting the lifecycle. In practice, 11 wt% H2 reversibility was demonstrated for very high pressures and temperatures, while only 2.5 wt% H2 at reasonable conditions. In this work, the composites made of commercial γ-Mg(BH4)2 and synthesized silica aerogel microparticles were prepared by thermal treatment in hydrogen under 120 bar H2 and 200 ºC for 3 h. As a result, calorimetric measurements showed a decrease in decomposition temperature by 60 ºC with respect to the pure hydride, and a single step decomposition in range of 220-400 ºC in the prepared composite. The kinetic of the first dehydrogenation at 300 ºC for Mg(BH4)2–SiO2 composites was two times faster compared to that of the bulk γ-Mg(BH4)2. Experimental results suggested that silica aerogel acting as scaffold for γ-Mg(BH4)2 nanoconfinement resulted in an inherent mechanism of reversible hydrogen sorption: for bulk γ-Mg(BH4)2 and the prepared Mg(BH4)2–SiO2 composite 42 % of reversible hydrogen sorption was experimentally observed for the first time at 390 ºC and 110 bar H2 during the 2-nd and 3-rd cycles.

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Authors : Kasper T. Moller, Morten B. Ley, Alexander S. Fogh, Torben R. Jensen
Affiliations : Interdisciplinary Nanoscience Centre and Department of Chemistry, Aarhus University

Resume : Bimetallic borohydrides synthesized from alkali, alkali earth and/or transition metal borohydrides by mechanochemical treatment have received significant attention, because of their structural diversity and very high volumetric density of hydrogen [1-3]. Recently, new bimetallic compounds were found in the KBH4-M(BH4)2 (M = Mg or Mn) system. Particularly, the perovskite structure of KMn(BH4)3 is interesting, as it initiated a thorough study of novel perovskite-type metal borohydrides [4]. Recently, strontium borohydride, Sr(BH4)2, and halide free Sm(BH4)2 has been reported [5,6]. Thus, we here study the formation and properties of new MM’(BH4)3 from MBH4-M’(BH4)2, M = Na, K, Rb and Cs; M’ = Sr, Sm mixtures using mechanochemical treatment i.e. ball milling. We discovered new bimetallic compounds, KM’(BH4)3, RbM’(BH4)3 and CsM’(BH4)3, M’ = Sr, Sm, which have an orthorhombic perovskite crystal structure, similar to KMn(BH4)3. These new bimetallic compounds have been investigated by in situ synchrotron radiation X-ray powder diffraction (SR-PXD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Sieverts’ method [7]. The new bimetallic compounds, MSr(BH4)3, behaves similar to Sr(BH4)2 as the decomposition is very complex, thus decomposition products have been determined ex situ. Additionally, reversiblity has been tested using a Sieverts apparatus by conducting a desorption-absorption-desorption cycle. However, thermal stability of solid borohydride compounds owing to strong covalent and ionic bonding often provides high decomposition temperatures alongside slow kinetics and poor reversibility [8]. Indeed, high thermal stability might be an advantage in respect to other applications e.g. ion conductors or magnetic compounds, exsemplified by gadolinium borohydrides, AnGd(BH4)n+3 (A = K, Cs) with interesting magnetic refrigeration properties [9]. References [1] L. H. Rude et al., Phys. Status Solidi A, 208 (2011) 1754 – 1773. [2] P. Schouwink et al, J. Phys. Chem. C 116 (2012) 10829–10840. [3] R. Černý and P. Schouwink, Acta Cryst. B71 (2015), 619-640. [5] D.B. Ravnsb?k et al. Inorg. Chem. 52 (2013), 10877–10885. [6] T. Humphries et al., J. Mater. Chem. A 3 (2014), 691–698. [7] K. T. M?ller, Dalton Trans. 45 (2015), 831-840. [8] L. George, Int. J. Hydrog. Energy 35 (2010), 5454–5470. [9] P. Schouwink, J. Alloys Compd. 664 (2016), 378-384.

Authors : Anna-Lisa Chaudhary, Claudio Pistidda, Thomas Klassen and Martin Dornheim
Affiliations : Department of Nanotechnology, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Geesthacht , Germany

Resume : Hydrogen technology can be incorporated into intermittent renewable energy systems to realise a complete clean, green energy harvesting and storage cycle. An efficient hydrogen storage system based on solid state hydrogen requires optimised material properties for each particular application. There are several approaches to tailoring material properties towards particular applications including the alloying additions to change the thermodynamic properties, additives to improve reaction kinetics and combining hydrides together to form so call ‘’reactive hydride composite’’ (RHC) systems. The mixture of two or more phases has vastly improved properties in terms of reaction kinetics and thermodynamics compared to their individual counterparts, however, the reaction mechanisms are complex and particular to each individual system and some of these issues will be presented here. In all of these approaches aiming to tailor thermodynamics, high capacity at moderate temperatures as a critical application requirement has not been met by any of the investigated systems so far. Complex hydrides are very promising hydrogen-storage materials, due to their high gravimetric and volumetric capacities. At moderate temperatures and pressures both borohydride and alanate systems have increased functionality when used in multi-component systems. The most state-of-the-art multicomponent systems will be presented with respect to several complex hydride systems and their potential towards application. This technology can provide compact and efficient energy solutions to reduce climate change and in turn, improve the global environment.

Advances in the properties of borohydrides : Petra de Jongh
Authors : Drew A. Sheppard 1, Leslie Glasser 2, Terry D. Humphries 1, Craig E. Buckley 1
Affiliations : aHydrogen Storage Research Group, Fuels and Energy Technology Institute, Department of Physics and Astronomy, 1 Curtin University, GPO Box U1987, Perth, WA 6845, Australia. 2 Nanochemistry Research Institute, Department of Chemistry, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.

Resume : Over the last decade dozens of new hydride structures have been synthesised based on complex anions including [BH4]−, [B12H12]2−, [AlH4]−, [AlH6]3−, [NH2]−, [NH]2− and [FeH6]4−. Many of these new structures are comprised of combinations of cations, complex hydride anions and halide anions. In addition, a large number of complex hydride metal ammines have also been synthesised. The prediction of the decomposition pathway of these complex hydrides requires knowledge of their thermodynamic properties. This can be achieved using Density Functional Theory (DFT), but DFT has a number of limitations: functionals that are suitable for hydrides must first be chosen, the calculations are performed at 0 K and approximations need to be made to obtain estimates of the enthalpies and entropies at room temperature and above. Lastly, it cannot easily be applied if the crystal structures of reaction products are unknown or amorphous. The thermodynamics for complex hydrides can be estimated using the Thermodynamics by Difference Rules (TDR) and Volume Based Thermodynamics (VBT) method. The TDR and VBT methods achieve this by relating the unknown thermodynamic properties of a new complex hydride to the experimental thermodynamic properties of a related phase. The TDR and VBT methods are most accurate if the crystal structure or density of the new complex hydride is known, but they can also be applied to amorphous compounds and compounds where only the chemical formula might be known. Thermodynamic quantities such as enthalpy of formation, entropy and heat capacity can be readily estimated and used to predict the reaction pathways of new complex hydrides. Application of the TDR method and an improved VBT method to complex hydrides of the alkali metals shows that the calculated enthalpy of formation (per mole of formula unit) can be estimated to within 15 kJ.mol-1 of the experimental value. Similarly, the entropy can typically be estimated to within 15 J.mol-1.K-1. The extension of this technique to multi-cation and multi-anion complex hydrides will be discussed.

Authors : Michael Heere, Seyed Hosein Payandeh GharibDoust, Christoph Frommen, Magnus H. Sørby, Torben R. Jensen and Bjørn C. Hauback
Affiliations : Michael Heere; Christoph Frommen; Magnus H. Sørby; Bjørn C. Haubacka Physics Department, Institute for Energy Technology, NO-2027 Kjeller, Norway Seyed Hosein Payandeh GharibDoust; Torben R. Jensen Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Århus, Langelandsgade 140, DK-8000 Århus C, Denmark

Resume : Rare earth (RE) borohydrides have recently received attention as possible hydrogen storage materials and solid-state Li-ion conductors. They have mostly been synthesized by metathesis reactions between LiBH4 and RE halides, thus yielding Li halides as byproducts. The current syntheses for RE borohydrides with RE = La, Gd and Er were performed by a combination of a metathesis reactions and wet chemistry with removal of the LiCl byproduct. This is the first time halide free Er(BH4)3 has been synthesized. Rehydrogenation of pure decomposed Er(BH4)3 was not successful. However, a composite of decomposed Er(BH4)3 + 50 wt% LiH was rehydrogenated and resulted in formation of ErH3 and LiBH4. Furthermore, the decomposition and reversibility of composite mixtures of RE(BH4)3 with 3LiBH4 and 3LiH with hydrogen capacities up to 10 wt% were investigated during in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and during ex situ measurements in a Sieverts-type apparatus. Three desorption-absorption cycles of the 3LiBH4 + Er(BH4)3 + 3LiH composite at 400/ 340 °C and 5/ 100 bar H2, respectively, showed a reversible hydrogen capacity of 3.7 wt%. This amount corresponds to 87 % of the initially released 4.3 wt% hydrogen. The research leading to these results has received funding from the People Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7/2007-2013/ under REA grant agreement n° 607040 (Marie Curie ITN ECOSTORE) and is thankfully acknowledged.

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Hydrides for energy storage applications: solid electrolytes i : Duncan Gregory
Authors : Petra de Jongh*, Sander Lambregts*, Peter Ngene*, Margriet Verkuijlen**, Tejs Vegge*** , Arno P. M. Kentgens**, and Didier Blanchard***
Affiliations : *Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands; **Institute for Molecules and Materials, Radboud University, Nijmegen , The Netherlands; ***Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde, Denmark

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. Less than 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 [1]. 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[2]. 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 [3,4]. Systematic studies show how the ionic conductivity can be optimized by tuning the nanostructure and interfaces in these nanocomposites. Finally first results have been obtained in using these materials as solid-state electrolytes in next generation all-solid state lithium-sulphur batteries. [5] [1] de Jongh et al. J. Appl. Phys. A (2016), 122:251. [2] Blanchard et al., Adv. Funct. Mater. 25 (2015), 182. [3] Verkuijlen et al., J. Phys. Chem. C 116 (2012) 22169. [4] Suwarno et al, submitted

Authors : Arndt Remhof (1), Yigang Yan (1), Ruben-Simon Kühnel (1), Arndt Remhof (1), Daniel Rentsch (1), Zbigniew Łodziana (2), Corsin Battaglia (1)
Affiliations : (1) Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland (2) Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Kraków, Poland

Resume : All-solid-state batteries promise to overcome the safety issues related to flammable organic liquid electrolytes used in state-of-the-art lithium ion batteries. So far, no solid-state electrolyte satisfies all the requirements for a competitive solid-state battery for the mass market. We report the discovery of a new lithium borohydride based superionic phase near room temperature , enabling ionic conductivities of up to 7x10-3 S cm-1, comparable to values of common organic liquid electrolytes. The enhanced lithium ion motion results from an anion supported vacancy mechanism. A model device, using Li4Ti5O12 electrodes and the a new lithium borohydride based superionic phase as solid electrolyte exhibits good rate performance up to 5C and stable cycling over hundreds of cycles at 1C at 40 °C, indicating high bulk and interfacial stability. Our results show the potential of lithium borohydride based solid-state electrolytes for high-power lithium ion batteries.

Hydrides for energy storage applications: solid electrolytes ii : Arndt Remhof
Authors : Duncan H Gregory
Affiliations : WestCHEM, School of Chemistry, University of Glasgow

Resume : With the steady depletion of fossil fuels, concerns over climate change and the necessity for secure sources of fuel supply, the need to explore alternatives to a carbon-based economy is becoming more urgent. One could consider storing sustainably generated electrical energy directly (for example in batteries) or indirectly using an energy vector, such as hydrogen. In fact, some materials with similar origins can serve both these purposes and the release of hydrogen from a number of complex hydrides, such as lithium borohydride, is linked to a transition to a fast ion conducting state. Partial anion replacement with appropriate halides can stabilise the high temperature structures of these hydrides, engendering fast ion conductivity at room temperature and enabling the design of potential new solid state electrolyte materials for secondary batteries. This talk will consider how one might design and produce new fast ion conducting complex hydride materials, taking lithium borohydride, LiBH4, as a basis. In contrast to their use in hydrogen storage applications, the hydrides should be thermodynamically robust to allow operation over a range of working temperatures. “Soft chemistry” synthesis and the ionic conductivity of these materials will be described. Stabilisation of the high temperature and high pressure phases of LiBH4 via anion and cation substitution will be discussed and the relationships between conduction mechanism and structure elucidated. Anion and cation disorder are crucial factors in determining the fast ion conduction properties of the materials. Finally, families of complex hydrides-“chemical” hydrides, incorporating ammonia borane and derivatives will be introduced. The open structures formed by these hybrid materials create new pathways for Li+ ion conduction, which can be tailored by anion substitution.


Symposium organizers
Julia RINCKKarlsruhe Institute of Technology

Hermann-von-Helmholtz Platz 1 - 76344 Eggenstein-Leopoldshafen - Germany

+49 (0)721 608 28906
Terry HUMPHRIESCurtin University

GPO Box U1987 Perth WA 6845, Australia