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2015 Fall

Materials and devices for energy and environment applications


Hydrogen storage in solids: materials, systems and application trends

H2 storage is one of the main challenges towards a viable hydrogen economy. Materials-based storage offers distinct advantages compared to technologies using compressed gas or cryogenic liquid, and has clearly paved the way for other important energy storage applications (e.g. secondary batteries).



Over the last decade, intensive efforts have been devoted worldwide to the research and development of materials with suitable hydrogen storage properties. Enormous progress has been accomplished and the scope of materials has expanded greatly: from traditional metal hydrides to complex and chemical hydrides, and from carbon structures to metal organic frameworks, and nanoconfined composite materials. The rapid progress in nanoscience has opened groundbreaking directions and has guided the tailoring of materials’ microstructures from bulk crystalline to amorphous state and nanostructures, while advanced characterization and simulation methods have contributed to the elucidation of key mechanisms, the in-silico assessment/design of materials and the optimization of hydrogen storage systems. The accumulated knowledge has greatly inspired and promoted research in other leading edge energy storage technologies such as secondary Ni-MH and Li-ion batteries.

This symposium is organized by one of the largest networks currently aiming to push the limits in solid-state hydrogen storage, the COST Action MP1103 ( bringing together a large number of leading groups (more than 250 researchers) from within and outside Europe.


Hot topics to be covered by the symposium:


  1. Hydrogen storage materials
    • Metallic, complex, chemical hydrides
    • Nanoporous sorbents
    • Nanocomposites
    • Thin films
  2. Hydrogen storage fundamentals
    • Thermodynamics and Kinetics
    • Catalytic properties, reaction mechanisms, diffusion and transport phenomena
    • Advanced structural characterization
    • Modeling approaches for the description of materials and processes at different scales
  3. Applications
  • Trends & insights
  • Stand-alone and integrated hydrogen storage systems
  • Electrochemical applications: batteries and fuel cells components
  • Metal hydride compressors
  • Thermal storage




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Session 1 : Amelia Montone
Authors : Andreas Züttel, Elsa Callini, Shunsuke Kato, Philippe Mauron, Marco Holzer
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, Sion, Switzerland

Resume : The storage of renewable energy is the greatest challange for the transition from the fossil aera to a sustainable future. The world economy can only continue to grow if renewable energy i.e. solar energy becomes the major source of energy and if the materials cycles will be closed in the near future. Hydrogen produced from renewable energy leads to a closed cycle, because the water relesed from the combustion condenses in the atmosphere. The challenge in the large scale application of hydrogen is the storage with a high gravimetric and volumetric density. Based on todays knowledge hydrogen storage is limited to about 20 mass% and 70 kg/m3. Therefore the maximum energy density of a hydrogen based energy storage is limited to approx. 50% of that in fossil fuels. In order to achieve a comparable energy density of fossil fuels, hydrogen has to be stored in hydrocarbons (synthetic fuels), where the CO2 is extracted from the atmosphere. The latter requires energy in order to increase the concentration from 400 ppm to pure CO2, corresponding about 5% of the heating value of the hydrocarbon. However, the process working close to the thermodynamic limit is not know yet. Furthermore, the reduction of CO2 to hydrogen is based on the Sabatier to Methane or on the reversed water gas shift reaction and Fischer-Tropsch synthesis to an unspecific hydrocarbon. The surface of metal hydrides can offer new reaction paths and catalytic centers with atomic hydrogen.

Authors : Francois Aguey-Zinsou
Affiliations : MERLin, School of Chemical Engineering, The University of New South Wales, Sydney, Australia

Resume : Storing hydrogen in materials is based on the observation that metals can reversibly absorb hydrogen, however practical application of such a finding is found to be rather challenging especially for vehicular applications. The ideal material should reversibly store a significant amount of hydrogen under moderate conditions of pressures and temperatures. To date, such a material does not exist, and the high expectations of achieving the scientific discovery of a suitable material simultaneously with engineering innovations are out of reach. Of course, major breakthroughs have been achieved in the field, but the most promising materials still bind hydrogen too strongly and often suffer from poor hydrogen kinetics and/or lack of reversibility. Herein, progress made toward the practical use of hydrides as a hydrogen store and the barriers still remaining are reviewed. In this context, the new approach of tailoring the properties of hydrides through size restriction at the nanoscale is discussed. Such an approach already shows great promise in leading to further breakthroughs because both thermodynamics and kinetics can be effectively controlled at molecular levels. The effects of size restriction on the storage properties of magnesium and other complex hydrides such as LiBH4 would be discussed as well as potential core-shell strategies to design practical store based on these nanosized hydrides.

Authors : Peter Ngene (1), Suwarno (1), Angeloclaudio Nale (1), Tejs Vegge (2), Didier Blanchard (2), Petra de Jongh (1)
Affiliations : (1) Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands (2) Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde, Denmark

Resume : LiBH4 is a so-called ?complex hydride?, a solid consisting of a lattice of Li cations and BH4- anions. It is potentially interesting for reversible solid state hydrogen storage (containing 18.5 wt% hydrogen) and as a solid state Li-ion battery electrolyte. However, in macrocrystallline LiBH4, high hydrogen and lithium ion mobilities are only found at relatively high temperatures. For instance hydrogen can only be released at an appreciable rate above the melting point (280 oC), while appreciable Li ion mobility is only found in the high temperature hexagonal phase (above 110 oC). Nanoconfinement of LiBH4 in mesoporous scaffolds (2-20 nm pores) greatly changes its properties. [1] Confinement in turbostratic carbon led to an altered hydrogen release pathway of LiBH4 to B and LiCx, releasing the full content hydrogen at 375 ?C under Ar. Under 1 bar H2, decomposition started at 150 ?C lower than the equilibrium decomposition temperature. Confinement into SiO2 nanoscaffolds led to high hydrogen and Li local mobilities at room temperature, dominated by LiBH4 within 1-2 nm from the SiO2 pore walls [2]. Conductivity measurements show that the Li-ion conductivity of LiBH4 at room temperature is increased by more than three orders of magnitude upon nanoconfinement, making it a promising electrolyte for all solid-state batteries [3]. References: [1] Ngene, Chem. Comm. 46 (2010), 8201; [2] Verkuijlen, JPCC 116 (2012); [3] Blanchard, Adv. Funct. Mater. 25 (2015), 182

Session 2 : Jose Ares
Authors : Fermin Cuevas, Zhinian Li, Junxian Zhang, Michel Latroche
Affiliations : ICMPE/CNRS-UPEC UMR 7182, 2-8 rue Henri Dunant, 94320 Thiais, France; GRINM, 2 Xinjiekou Wai Street, Beijing 100088, China

Resume : Efficient storage of hydrogen is widely recognized as a key challenge in the transition towards a hydrogen-based energy economy. We here explore the mechanochemistry under hydrogen gas of the light-weight systems Li-N-H and Li-Mg-N-H. Starting reactants were Li3N and 2Li3N+Mg, respectively, and hydrogen gas at 80 atm. In-situ hydrogen absorption curves were monitored during mechanochemical synthesis. The reaction paths were elucidated by means of ex-situ X-ray (XRD) and neutron diffraction. Starting from Li3N, hydrogen absorption of 9.8 wt.% H occurs in 2 h following two steps of equal hydrogen uptake: Li3N + 2H2 -> Li2NH + LiH +H2 -> LiNH2 + 2LiH. Interestingly, the second step entails the formation of non-stoichiometric imide phases. Starting from 2Li3N+Mg powder mixture, two reactions steps of 3.9 and 4.7 wt.% were noticed during 4 h of milling. The reaction path also entails two steps: 2Li3N + Mg + 5H2 -> Li3MgN2H + 3LiH +3H2 -> Mg(NH2)2 + 6LiH. The metastable mixed-cation imide Li3MgN2H is formed as intermediate and magnesium amide is obtained in amorphous state. The structural and hydrogenation properties of the metastable Li3MgN2H and amorphous Mg(NH2)2 phases where further studied by in-situ neutron diffraction using deuterated samples. Results will be unveiled during the conference. Mechanochemistry under hydrogen gas is an efficient method for fast synthesis of light-weight hydrides leading to the formation of novel metastable phases with unexplored properties.

Authors : L. H. Jepsen 1, M. B. Ley 1, R. Černý 2, Y. S. Lee 3, Y. Filinchuk 4, D. Ravnsbæk 5, Y. W. Cho 3, T. R. Jensen 1
Affiliations : 1 iNANO and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark; 2 Laboratory of Crystallography, DQMP, University of Geneva, Switzerland; 3 High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea; 4 Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Place L. Pasteur 1, Louvain-la-Neuve, Belgium; 5 Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

Resume : Ammine metal borohydrides, M(BH4)m∙nNH3, have recently received significant attention owing to their promising hydrogen storage properties [1] We present more than 30 new halide-free and solvent-free ammine metal borohydrides based on M = Mg, Ca, Sr, Mn, Y, La, Ce, Gd and Dy. The compounds are synthesized by combining solvent-based techniques, mechanochemistry, solid-gas reactions and thermal treatment. This allows to efficiently control the NH3/BH4 (n/m) ratio, e.g. the first long series of Y(BH4)3∙nNH3 (n = 1, 2, 4, 5, 6 and 7) is presented,2 where an increased hydrogen purity is obtained for lower n/m ratios [2,3]. The structures of all new compounds are solved from powder X-ray diffraction and subsequently optimized by DFT calculations. Interestingly, destabilization is observed for most metal borohydrides with low electronegativity, while metal borohydrides with high electronegativity are stabilized by NH3 [1,4]. We propose a new mechanism for gas release, which depends on the ammonia release temperature and the stability of the metal borohydride, which will be discussed in more detail. References [1] L. H. Jepsen. Mater. Today 2014, 17, 129–135. [2] L. H. Jepsen. Submitted 2015. [3] L. H. Jepsen. ChemSusChem 2015. [4] L. H. Jepsen. Submitted 2015.

Authors : J-Ph. Soulié (1), B.E. Hayden(1),(2)
Affiliations : (1) Ilika Technologies Ltd., Kenneth Dibben House, Enterprise Road, Chilworth, Southampton SO16 7NS, UK; (2) School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK

Resume : Lithium-magnesium alloys are the lightest metallic alloy with a density of 1.35-1.65 g/cm3. Hydrogenation of lithium-magnesium alloy appears difficult and is rarely reported in the literature. An attempt to synthesize LiMgH3 was made by substitution of Na by Li in LixNa1-xMgH3 but there was no evidence of the perovskite phase LiMgH3 [1]. The authors suggested that LiMgH3 is impossible to form under solid state conditions due to geometric restrictions. The synthesis of a series of novel Lithium-Magnesium hydride compounds is reported using a unique ultra-high vacuum high throughput physical vapour deposition, HT-PVD [2], [3]. The behaviour of the alkali-earth binary hydride has been characterized by Temperature Programmed Desorption (TPD) analysis and an optimum composition with a high gravimetric capacity (> 10 wt.%) was identified. This system shows a reversibility under very mild condition (10 bar H2, room temperature). A high-energy reactive milling of a Li-Mg alloy was subsequently attempted and the result of the trial will be discussed. References [1] K. Ikeda, Y. Nakamori, S. Orimo, Acta Mater. 53 (2005) 3453 [2] Patent WO 2009/101046 [3] B.E. Hayden, J-Ph. Soulié et al., Faraday Discuss. 151 (2011) 369

Authors : A. Gotzias, A. Ampoumogli, D. Giasafaki, G. Charalambopoulou, Th. steriotis
Affiliations : National Center for Scientific Research “Demokritos”, 15310 Ag. Paraskevi Attikis, Athens, Greece

Resume : The interaction of H2 with carbon-based materials has been studied intensively for the adsorption-based characterisation of nanoporous adsorbents but also as a result of the interest in using such substrates for hydrogen storage. Porous carbon materials can in general achieve adequate gravimetric storage but only at cryogenic conditions (e.g. 77 K) due to the weak interactions involved. Physisorption forces may be enhanced in narrow micropores, with a size close to the kinetic diameter of H2 molecules. H2 molecules, confined in very narrow spaces at low temperatures, cannot be treated as classical Lennard-Jones particles, as quantum effects become significant. Indeed, the quantum nature of H2 (and its isotopes) gives rise to the so-called quantum molecular sieving, which can be exploited for e.g. the separation of H2/D2 mixtures. We herein aim at providing additional insight into the crucial effect of pore size and pressure on the adsorption of H2 (and D2) in porous carbons by Grand Canonical Monte Carlo simulations in model slit micropores at 77 K. GCMC results are also coupled with experimental high pressure H2 (and D2) adsorption data at 77K for different nanoporous carbons.

Authors : Burak Aktekin, Tayfur Öztürk
Affiliations : Middle East Technical University

Resume : There is a considerable interest in carbon coating of metal hydrides for energy storage purposes. This might result in improved thermal conductivity of metal hydrides, an aspect which is of considerable interest in Mg based hydrogen storage tanks. In batteries, such coatings might improve the electrical conductivity, thus obviating the need for the special additives used for such purposes in the electrode make-up. In the current work, following a successful synthesis of Mg2Ni and Mg nanoparticles using thermal plasma [1], we investigate whether in-situ encapsulation of such particles with carbonaceous material would be possible with the same method. [1] B Aktekin, G Çakmak and T Öztürk, Induction thermal plasma synthesis of Mg2Ni nanoparticles. Int. J of Hydrogen Energy, 39, 2014,9859.

Authors : Anna-Lisa Chaudhary,1,2 Drew A. Sheppard,2 Mark Paskevicius,2,3 Claudio Pistidda,1 Craig E. Buckley,2 Martin Dornheim1
Affiliations : 1 Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Geesthacht , Germany 2 Department of Physics, Astronomy and Medical Radiation Sciences, Curtin University, Perth, Australia 3 Institute for Kemi, Aarhus University, Aarhus C, Denmark

Resume : The Mg-Si-H system could be used for a range of practical applications including mobile transport since thermodynamic calculations indicate that it has equilibrium conditions of 1 bar of hydrogen pressure at room temperature. Experimentally, these conditions have never been met, for either absorption or desorption, indicating that reaction kinetics play a dominant role in the reaction. Presented here is a kinetic hydrogen desorption study involving MgH2 with Si prepared using different methods to obtain different crystallite sizes (or grain size in the case of amorphous Si nanoparticles). An empirical understanding of the relationship between crystallite size and reaction kinetics for the dehydrogenation of MgH2 in the presence of Si was determined. It was found that there is a strong correlation between crystallite size and activation energy for the growth of the Mg2Si phase and the three dimensional Carter-Valensi (or contracting volume) diffusion model could be used to describe the rate limiting step of the reactions. A reaction mechanism has been proposed showing that nucleation occurs at the surfaces/interfaces at a fast rate followed by slow diffusion of H out of the Mg matrix whilst Mg bonds with the Si as it moves through the Si matrix to form Mg2Si.

Authors : Efi Hadjixenophontos, Guido Schmitz
Affiliations : University of Stuttgart Institute for Materials Science Chair of Materials Physics

Resume : Magnesium hydride (MgH?2) is noteworthy because of its dual use as both a hydrogen storage material and as a potential battery electrode material. This work focuses specifically on characterizing the hydrogenation of Mg thin films (≈200nm) deposited by ion beam sputtering. Hydrogenation of the Mg layer was studied in the temperature range of 100 to 300?C in a H2 atmosphere up to 100bar. Monitoring the lattice structure by XRD allowed us to gain insight into the sorption of hydrogen and the subsequent hydride formation. TEM measurements before and after hydrogenation demonstrated the changes in microstructure. It is known that the creation of MgH2 creates a ?blocking effect? that slows down hydrogenation kinetics. In the presented experiment, complete hydrogenation of a 200nm Mg layer was achieved after 3 hours at 300?C under a 10bar H2 atmosphere. Performing the hydrogenation in smaller steps we determined the hydrogenation kinetics. In order to accelerate the absorption/desorption process, small amounts of Pd catalyst (5-20nm of Pd) were also deposited on top of the Mg layer. The observed kinetics were compared with volume diffusion and interface diffusion models.

Authors : Borysiuk V.I., Hizhnyi Yu.A., Nedilko S.G.
Affiliations : Taras Shevchenko National University of Kyiv, Volodymyrska Street 64/13, 01601, Kyiv, Ukraine

Resume : Mixes of carbon nanotubes (CNT) are generally recognized as perspective materials for adsorption of gas molecules. However, application of such materials for efficient hydrogen storage is under question since it was found that materials based on undoped CNTs possess low hydrogen sorption capacity [1]. An intensive search for modifications of the CNT structures that can improve hydrogen uptake by materials, in particular by doping the CNTs with non-isovalent ions, is currently in progress. In this search, using the first-principles computational studies of molecular adsorption on the CNT surfaces is a very advantageous approach since the calculations can independently predict sorption capabilities of the CNT-based materials. In this work, computational studies are applied to estimate the hydrogen storage capabilities of two types of doped CNT-based materials, namely the boron-doped and the nitrogen-doped ones. Adsorption of hydrogen molecules on the surfaces of undoped and B(N)-doped various chiralities CNTs as well as on graphene surface is studied by the DFT-based electronic structures quantum-chemical calculations. The relaxed geometries, binding energies of the molecules to the CNTs, density contours of electronic vawefunctions, dependencies of binding energies on tube- molecule distance are obtained and analyzed in view of studied materials potential application for hydrogen storage. [1] S.H. Barghi, T.T. Tsotsis, M. Sahimi, Int. J. of Hyd

C.C I.2
Authors : Banu Ozturk, Zeynel Ozturk, Goksel Ozkan, Abdurrahman Asan, Dursun Ali Kose
Affiliations : Hitit University, Department of Chemical Engineering; Hitit University, Department of Chemical Engineering; Hitit University, Department of Chemistry

Resume : The main aim of new metal-organic material investigation was to set alternative adsorbent for hydrogen storage. It is why, mono anionic mono dentate oratato complex of Co(II) was synthesized. The final molecular formula of the compound is Co(H3Or)2.nH2O which was synthesized according to room temperature method. The characterization process carried out Uv-vis, FT-IR, elemental and thermal analysis. Also the crystal structure was refined by using single crystal XRD data. Hydrogen storage property of the compound was measured by using HPVA at 77 K and up to 100 bars pressure. In the other hand, final crystal structure was used to simulate hydrogen storage property theoretically. GCMC ensemble with LJ potentials was used to simulate hydrogen storage property of the material. In addition, HOMO and LUMOs were determined for repeated molecular structure for clarification of adsorption process. It is found that the compound could uptake 2.2 wt. % hydrogen at 77 K and 85 bars pressure experimentally. It is also found, the hydrogen molecules placed close to LUMOs and the most important factor for storage process was accessible surfaces according to simulations.

C.C I.5
Authors : Efi Hadjixenophontos, Lukas Michalek, Guido Schmitz1
Affiliations : University of Stuttgart Institute for Materials Science Chair of Materials Physics

Resume : Magnesium and titanium hydrides (MgH¬2, TiH2) are good candidate materials for hydrogen storage. Furthermore, MgH2 shows promise as a potential battery electrode material. In thin film geometry, both materials may also be used as optical switches. In our work, we used thin films with a defined thickness in order to quantitatively determine diffusion coefficients and measure kinetic barriers at the interfaces. Mg and Ti thin films (≈200 nm) were deposited using ion beam sputtering. Hydrogenation of these layers was studied at temperatures up to 300°C under 10bars of H2 atmosphere for different durations. Microstructural changes were studied by TEM and hydrogen sorption was quantified by XRD, with emphasis on quantitatively comparing the behavior of both materials.

C.C I.10
Authors : R.Vujasin1, S.Milošević1 B. Paskaš Mamula1, M.Lelis2, D.Milčius2, R.Zostautiene3 J.R.Ares Fernandez4,F.Leardini4, C. Sanchez4, J.Grbović Novaković1
Affiliations : 1Vinča Institute of Nuclear Sciences, University of Belgrade, Laboratory for Material Sciences, Belgrade, Serbia 2Center for Hydrogen Energy Technologies, Lithuanian Energy Institute, Kaunas, Lithuania 3Department of Physics, Faculty of Mathematics and Natural Sciences, Kaunas University of Technology, Kaunas, Lithuania 4Dpto. de Física de Materiales M-04 Facultad de Ciencias Universidad Autónoma de Madrid

Resume : Among various nanostructures used as potential material for hydrogen storage, MgH2 thin films attract attention for several reasons, easy way of synthesis and low reactivity not being least important. Moreover, thin films offer the possibility to study influence of microstructure and additives on hydrides sorption properties in controlled way. The mechanism of desorption from thin films the is described by nucleation and growth process, but in capped films an interface mechanism is proposed as well. To clarify the mechanism of reaction, in situ desorption from MgH2-TiO2 films coupled with optical microscopy were used, followed by numeric simulations. On the other hand, titania draws a lot of interest because of its non-toxicity, safe usage and low cost. Further, it has the same (rutile) structure as MgH2, with similar lattice parameters. The interaction of hydrogen with catalyst (TiO2- (110) – (1x1) surface were investigated using PAW method as implemented in Abinit code. The hydrogen diffusion behavior and the thermodynamic properties were calculated by means of the full relaxation of the structure in every step of bulk diffusion, followed by activation energies calculations using NEB method. The results show the existence of potential barriers close to every atomic layer and the trends of barriers and overall system energy lowering away from surface. In-situ optical study shows that nucleation process depends on sample thickness.

C.C I.11
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Session 5 : Petra de Jongh
Authors : Radovan Černý*, Pascal Schouwink, Yolanda Sadikin, Matteo Brighi, Emilie Didelot
Affiliations : Laboratory of Crystallography, DQMP, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211, Geneva, Switzerland

Resume : Powder diffraction at modern high brilliance X-ray sources is the most useful tool to investigate 'real life' energy-related materials because it is easy, fast and extremely versatile. However, it rapidly reaches its limits due to the bad crystallinity of samples as well as due to the method itself. We will show how a complementary approach combining powder diffraction with non-diffraction methods such as vibrational spectroscopy, thermal analysis and supported by ab initio solid state calculations allows overcoming these limitations [1]. A deeper understanding of the building principles of metal borohydrides in the past years has provided means of going beyond hydrogen storage and making use of further properties specific to the borohydride anion. We wish to present new developments in the field of borohydride perovskites [2], targeting energy-related applications such as hydrogen-storage, solid state lighting or magnetic refrigeration. The BH4 anion is prone to vivid structural dynamics which have recently been made use of in the development of solid state electrolytes. Very recently, the focus has moved to compounds based on higher boranes, such as B12H12. We have extended this concept to mixed-anion compounds and will present the ionic conductivity results in Na3BH4B12H12 showing RT ionic conductivity close to 10-3 S/cm [3]. 1 P. Schouwink et al. Chimia, 68 (2014) nr. 1/2 2 P. Schouwink et al. Nat. Comm., 2014, 5, 5706 3 Y. Sadikin et al. Adv. Energy Mat., submitted

Authors : Seyed Hossein Payandeh GharibDoust (a), Michael Heere (b), Magnus H Sørby (b), Christoph Frommen (b), Bjørn C. Hauback (b), Dorthe B. Ravnsbæk (c), Torben R. Jensen (a)
Affiliations : (a)Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark - (b) Physics Department, Institute for Energy Technology, P.O. Box 40, NO-2027 Kjeller, Norway - (c) Department of Physics, Chemistry and Pharmacy, University of Southern Denmark (SDU), 5320 Odense M, Denmark

Resume : Recently, considerable efforts have been devoted to the rare-earth metal borohydrides caused by their hydrogen storage properties. Here we report on the synthesis and characterization of a new series of bimetallic borohydrides MRE(BH4)3X, where RE=La, Gd, M=Cs, K and X=Cl, Br. These compounds are formed using RE(BH4)3 free of halide by-products, which leads to removal of any inactive mass. Thermogravimetric analysis and differential scanning calorimetry measurements of these compounds showed decomposition in the temperature range of 230-250 °C followed by weight loss of 2-3 wt%. In-situ powder X-ray diffraction (PXD) studies of the La(BH4)3 + KCl sample suggest formation of a high temperature polymorph upon further annealing of the compound. However, when KBr was used, formation of high temperature polymorph was not observed and the compound formed at room temperature was stable till decomposition. Mass spectroscopy showed hydrogen release starting from 191, 195 and 185 °C for La(BH4)3 + KCl, La(BH4)3 + KBr and La(BH4)3 + CsCl samples respectively, which were lower than the H2 release starting temperature in pure La(BH4)3 at 205 °C. In addition, mass spectroscopy confirmed that no diborane is released during the decomposition and H2 is the only released gas. In-situ PXD of the samples were measured at European Synchrotron Radiation Facility and their structure solution in addition to studying their reversible hydrogen storage properties are in process.

Authors : D. P. Broom
Affiliations : Hiden Isochema Ltd, 422 Europa Boulevard, Warrington WA5 7TS, UK

Resume : Hydrogen sorption measurements performed on materials can be subject to a range of experimental errors, and are thus technically demanding. This has led, in part, to problems with the reproducibility of some of the results that have appeared in the literature, including hydrogen storage studies of carbon nanotubes and nanofibres, boron nitride nanotubes, conducting polymers, metal-organic frameworks, and the proposed use of spillover to enhance the capacity of different porous materials. In this presentation, we provide an overview of these problems, the most significant sources of errors, particularly for low density samples at high pressures, and look at some of the recent developments in the area.

Authors : Cengiz Baykasoglu, Mesut Kirca, Zeynel Ozturk
Affiliations : Department of Mechanical Engineering, Hitit University; Faculty of Mechanical Engineering, Istanbul Technical University; Department of Chemical Engineering, Hitit University

Resume : Hydrogen storage in a novel carbon based hybrid material that is composed of fullerene units covalently sandwiched between parallel graphene sheets is investigated. The proposed sandwich-structured material has high surface area, tunable pore size and superior structural properties. The three-dimensional nano-sandwiched material structure is generated by fusing fullerenes randomly dispersed on different graphene layers. At this point, the heat welding method is applied to create the covalently bonded fullerene-graphene couplings via molecular dynamic simulations. After that, grand canonical Monte Carlo calculations are performed to calculate hydrogen physisorption in hybrid material at 77 K, in a broad range of pressure from 0.1 to 100 bars by using LJ 12-6 pair potential. As a result, the uptake capacities at 77 K are calculated as 3.73 and 5.40 wt.% under the pressures of 1 bar and 100 bars, respectively. These results are better than the most of carbon based structures; thus, the proposed sandwiched fullerene-graphene composite are potential candidates for future hydrogen storage applications.

Authors : Zbigniew Łodziana
Affiliations : Institute of Nuclear Physics PAN, Department of Structural Research, ul. Radzikowskiego 152, 31-342 Kraków, Poland.

Resume : Metal borohydride complexes and their derivatives are of interest due to their potential as an energy storage materials. Tuning of their thermodynamic and kinetic properties is achieved via formation of mixed-metal borohydride complexes; ammonia-containing metal borohydrides; confinement in small nanopores. Any of such procedures leads to materials with complex crystalline structure that is difficult to study due to large fraction of light elements. This complexity is a challenge for theoretical description. Challenges in theoretical description of tuned complex hydrides will be presented, and simple descriptor of their stability based on ionic potential will be introduced. Such descriptor is related to well-known relation between stability and Pauling electronegativity, however it can be accurately calculated for crystalline materials.

Authors : S. Nayebossadri*a, L. Pickeringa, David Booka, E.I. Gkanasb, A.D. Stuartb, D.M. Grantb and G.S. Walkerb
Affiliations : a University of Birmingham b University of Nottingham

Resume : The developments both in passenger and commercial hydrogen vehicles necessitate a rapid expansion in the centrally developed hydrogen distribution infrastructure. Easy on-site generation of hydrogen will make it attractive for domestic hydrogen generation and distribution. The required high hydrogen pressure (>350 bar) for refuelling the hydrogen vehicles can be achieved by a reliable Metal Hydride thermal sorption compression (MH compressor). However, design and the alloy selection of the MH compressor has an immediate impact on performance and efficiency of the system. In particular, the performance of a multi-stage MH compressor is governed by the alloys thermodynamic and kinetic properties. In addition, other requirements, such as: acceptable hydrogen capacity, plateau slope, hysteresis and the alloy stability during cycling. This study focuses on the alloys selection process for a domestic two-stage MH compressor capable of compressing 600 g hydrogen within 10 h to over 350 bar. A combination of an AB5 (LaNi5) and an AB2 (Ti-V-Mn) alloy is proposed to meet the required conditions. The plateau pressure of the commercially available Ti-V-Mn alloy was shown to be dependent on the unit cell volume of C14 laves phase. Hence, its plateau pressure was tuned by modifying the Mn content of the alloy to achieve the MH compressor operation temperature of RT-130 °C. Effective improvement in the hydrogen sorption kinetics of the Ti-V-Mn alloy was achieved by Mn addition and heat treating at 850 °C for 120 h. Whilst, a full hydrogen cycle (based on 80 % of hydrogen capacity) in the as-received Ti-V-Mn takes more than 45 min, it takes less than 20 min for the modified sample. This will result in a considerable reduction in the required amount of alloy.

C.C II.10
Authors : V.K. Michalis (1), J. Costandy (1), I.N. Tsimpanogiannis (1,2), I.G. Economou (1), A.K. Stubos (2)
Affiliations : (1) Chemical Engineering Program, Texas A&M University at Qatar, P.O. Box 23847, Doha, Qatar; (2) Environmental Research Laboratory, National Center for Scientific Research “Demokritos”, 15310 Aghia Paraskevi, Attikis, Greec

Resume : Solid hydrates have been investigated for several years for storage and transportation of H2, due to their ability to incorporate/store large volumes of gases, bearing a number of advantages compared to other materials, including reversibility, low cost, minimal environmental hazards, and safety (in terms of toxicity, flammability). For properly designing storage processes involving gas hydrates it is essential to know accurately the three phase equilibrium conditions. We herein focus on their calculation based on molecular dynamics (MD) simulations. For this, it is essential to describe accurately gas solubility in the aqueous phase as we showed in our previous work [1]. We thus aim at fine-tuning the water/hydrogen models in order to predict accurately H2 solubility in water. This is the first step towards using the direct phase coexistence methodology, as described in detail in [1], in order to calculate the hydrogen hydrate phase equilibria. [1] V.K. Michalis, J. Costandy, I.N. Tsimpanogiannis, A.K. Stubos and I.G. Economou, “Prediction of the Phase Equilibria of Methane Hydrates Using the Direct Phase Coexistence Methodology”, J. Chem. Phys., 142(4), 044501 (2015).

C.C II.12
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Authors : Carolina Picasso, Iurii Dovgaliuk, Yaroslav Filinchuk
Affiliations : Institute of Condensed Matter and Nanosciences Université Catholique de Louvain Place L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium

Resume : We investigate the solid-gas non-catalytic reaction between potassium borohydride and CO2 mediated by two different synthetic methods: mechanochemical and thermal. We present the first crystal structure known in the KBH4-CO2 system: K[H(OCHO)3], potassium triformatoborohydride, obtained by ball milling KBH4 under CO2 pressure at ambient temperature. The crystal structure was solved from synchrotron X-ray powder diffraction data in a monoclinic system with space group P21/c, where the central boron atom adopts tetrahedral coordination to three formate groups and one hydrogen. The evolution of the reaction between KBH4 and CO2 was monitored by a combination of thermogravimetric analysis (TGA) coupled with mass spectrometry (MS) and infrared spectroscopy (IR) in the temperature range between RT and 500 °C, revealing the generation of hydrogen, methylformate and trimethyl borate in a three step mass increase reaction. In situ synchrotron X-ray powder diffraction under CO2 pressure and variable temperature reveals the formation of a new crystalline phase, with unidentified composition, and KBO2 during the second and third steps of mass increase, respectively. The aim of our project is to establish the best and more effective conditions for a selective and sustainable generation of hydrogen and organic fuels from the recycling of CO2 with metal complex hydrides.

Authors : V. Iosub, A. Chaise, M. Elie, O. Gillia
Affiliations : CEA, LITEN, DTBH/SCSH/LSH, 38000, Grenoble, France

Resume : Hybrid hydrogen tanks based on compressed hydrogen and metallic hydrides seem to be a good trade-off between mass and volumetric capacity for storing hydrogen reversibly within pressure conditions lower than 350 bar. Indeed, it is advantageous to use the porosity of the metal hydride powder to store more hydrogen under compressed state. Moreover, allowing more pressure permits to improve the efficiency in charging the hydride material from both capacity and kinetics points of views. Even if car application remains unreachable with this technology, some niche applications are making sense, like heavy vehicles such as agricultural tractors, forklift or maritime applications. In this work, the bcc-type metal hydride is to be integrated into a type IV composite tank based on carbon fiber with a polymer liner. In order to be competitive with compressed hydrogen tank, the charging kinetics needs to be fast: 80 % of total capacity charged in less than 5 minutes. The modelling 0D has shown that it is possible to fulfill this objective by using hydrogen as a heat transfer fluid. Significant flow rates of hydrogen are however necessary to provide cooling of the hydride. The hydrides studied within this work are based on Ti-V-Cr bcc alloy with partially substituting vanadium with molybdenum or iron. The hydrogen storage properties of Ti5V70Mo5Cr20 and Ti5V65Fe10Cr20 bcc alloys will be presented. The vanadium partial substitution with molybdenum allowed the increase of the pressure from 10 to 30 bar at room temperature. On the other side, we observed that the addition of Fe drastically diminished the hydrogen capacity with more than 20 %, whilst the plateau pressure has been reduced by almost a magnitude order. Furthermore, in order to improve the poor activation and kinetics of this alloy, we used some catalyst based on Zr-Nb-Ni.

Session 10 : Francois Aguey-Zinsou
Authors : Craig E. Buckley
Affiliations : Faculty of Science and Engineering, Department of Physics, Astronomy and Medical Radiation Sciences, Curtin University, Perth, WA, Australia

Resume : Solar energy is the most abundant renewable energy resource and therefore represents the most important renewable energy resource to focus on. The IEA roadmap for solar energy set a target of 22% of global electricity production from solar energy by 2050, with 50% being produced from concentrating solar thermal (CST) power systems. Achieving this target will be possible only if the costs of producing electricity from solar energy are significantly reduced and cost effective energy storage technologies can be developed. A major challenge is to achieve continuous, low-variability power generation from renewable energy sources, for stand-alone applications or for integration with domestic power grids. Solar mirrors can collect thermal energy during the day and run a heat engine to convert it into electricity, but cannot provide power at night. However, if some of the heat is used to remove hydrogen from a metal hydride, the reverse reaction where hydrogen absorbs back into the metal hydride can then occur at night, releasing heat for power generation. This allows solar energy to provide 24 hour power generation. By combining a high temperature (T) metal hydride with a low T hydride a coupled pair reversible hydride thermochemical solar energy storage system is created. CST coupled to a high and low T hydride has the potential to provide a continuous supply of electricity to remote areas. I will present results on the properties of hydrides suitable for CST applications.

Authors : Dag Noréus
Affiliations : Department of Material and Environmental Chemistry, Stockholm University, Sweden

Resume : The battery chemistry that so far offers the longest, both calendar and cycle life is the Ni-H2 - battery (Nickel Hydrogen battery). This battery has mainly been developed for space applications where it has reached operation times approaching 20 years and counting cycles in the order of tenths-of-thousands. It differs from its cousin the NiMH battery by the use of pressurized gaseous hydrogen in contrast to a hydrogen storage alloy as anode. The key to increase power performance and usable life time of NiMH batteries lies in the control of the surface reactions on the MH-alloy particles. This also makes the electrodes to work under as ideal conditions as possible, further increasing stability and cycle life. By building 10 cells 12.5 volt bipolar battery modules with matched electrodes combined with low cost electronic circuits help to keep the cells within a safe voltage window. This facilitates the serial and parallel arrangement of modules in the construction of larger battery packs to reach higher voltages and capacities as it is done when building battery packs with Li-batteries. With 12.5 volt modules fewer units are needed than with 3.7 volt units.


No abstract for this day

Symposium organizers
Georgia CHARALAMBOPOULOUInstitute of Nuclear & Radiological Sciences and Technology Energy & Safety, National Center for Scientific Research “Demokritos”, Patriarchou Gregoriou & Neapoleos

15341 Ag. Paraskevi Attikis, Athens Greece

+30 210 6503404
Luca PASQUINIUniversity of Bologna

Department of Physics and Astronomy, Viale Berti-Pichat 6/2, Bologna, Italy
Yaroslav FILINCHUKInstitute of Condensed Matter and Nanosciences, Université Catholique de Louvain

Place L. Pasteur 1 bte L4.01.03 1348 Louvain-la-Neuve Belgium

+32 10 47 28 13