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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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08:50 Opening    
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 : Gavin S Walker
Affiliations : University of Nottingham

Resume : An attraction to concentrated solar thermal power plants, is that the thermal energy that is collected during the day can be stored and released when required to generate steam for a turbine generator. Chemical storage of heat offers a more compact solution than either phase change materials or the current state-of-the-art: sensible heat storage in molten salts. Magnesium is a cheap metal which offers much potential as a chemical thermal energy storage medium. The hydrogenation of magnesium is a very exothermic reaction, releasing 2850 kJ kg-1 (an energy density which is an order of magnitude greater than that for sensible heat storage). A challenge is the design and efficient operation of the thermal energy store. A prototype thermal energy store based on magnesium has been developed which has helped identify critical performance criteria which affect the bed formulation and store architecture. This prototype has also been used to validate modelling work which predicts the performance of the energy store

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

10:30 Coffee Break    
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 : F.Peru1, A. Santoru2, C. Pistidda2, G. Charalambopoulou1, C. Milanese3, S. Garroni4, M. Dornheim2, Th. Steriotis1
Affiliations : 1. National Center for Scientific Research “Demokritos”, 15341 Ag. Paraskevi Attikis, Athens - Greece; 2. Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Strasse 1, D-21502 Geesthacht, Schleswig-Holstein, Germany; 3. Pavia H2 Lab, C.S.G.I. & Dipartimento di Chimica, Sezione di Chimica Fisica, Università di Pavia, Viale Taramelli 16, I-27100 Pavia, Italy; 4. Department of Chemistry and Pharmacy, University of Sassari and INSTM, Via Vienna 2, I-07100 Sassari, Italy

Resume : Among metal imides-based composites, systems that have been proven to have interesting hydrogen storage properties [1], Mg(NH2)2-LiH appears to be a promising material due to its relatively good reversibility, moderate operating temperatures and high hydrogen storage capacity.[2] The dehydrogenation/hydrogenation of Mg(NH2)2+2LiH involves the formation of an intermediate ternary imide, i.e. Li2Mg2(NH)3 [3], which also forms from the decomposition of an equimolar Mg(NH2)2 / LiNH2 mixture at 375°C. This particular mixture, before decomposing to Li2Mg2(NH)3, exhibits eutectic melting at 350°C. In an attempt to investigate, but also modify, the thermodynamic and kinetic behavior of Li2Mg2(NH)3, a 1:1 Mg(NH2)2 / LiNH2 mixture was infiltrated in mesoporous templated carbons with distinctively different pore properties. The obtained composites were systematically studied using a wide range of techniques: N2 adsorption/desorption at 77K, Raman, SEM, H2 absorption/desorption but also in situ synchrotron radiation powder X-ray diffraction and coupled manometric - high pressure calorimetric measurements, in order to elucidate the effect of (a) nanoconfinement and (b) the contact with the carbonaceous surface on their hydrogen storage performance. [1] P. Chen et al., Nature, 2002, 420, 302. [2] Z. T. Xiong et al., Advanced Materials, 2004, 16, 1522. [3]. J. J. Hu et al., J. Phys. Chem. C, 2007, 111, 18439

Authors : A.Wolczyk*, E.Pinatel, E.Marano, M.Chierotti, C.Nervi, R.Gobetto, M.Baricco
Affiliations : Department of Chemistry and NIS, University of Turin via P.Giuria 9, I-10126 Torino, Italy

Resume : Hydrogen sorption reactions with an equilibrium close to ambient conditions need specific thermodynamic requirements. Complex hydrides are of special interest for electrochemical energy storage, as novel solid state ion conductors and anode conversion materials. The combination of different complex hydrides (e.g. LiBH4 and LiNH2) exceed the gravimetric hydrogen density of transition metal hydrides by one order of magnitude [1]. Moreover, it provides to the stabilization of the high conducting phase or the development of new crystal structures, characterized by open channels for fast Li-ion mobility. In this work, Li4(NH2)3(BH4) and Li2(NH2)(BH4) compounds have been investigated. Various synthesis techniques have been considered (i.e. ball milling, thermal treatment, wet chemistry). Long annealing time as well as high ball-to-powder ratio decrease the presence of secondary phases, leading to the formation of 1:3 as a single phase. 1:1 compound is metastable and it can be formed only by suitable thermal treatments. Results on wet chemistry synthesis, based on dissolution of parent compounds in various solvents (i.e. diethyl ether, THF, DMF, diglyme) followed by crystallization, will be reported. Currently, the LiBH4-LiNH2 phase diagram is not fully described [1], [2]. Thermodynamic assessments concerning eutectic point and melting of the compounds will be presented. Measurements of Li-conductivity confirmed superionic features of the studied compounds. [1] A.Borgschulte, M.O. Jones, E.Callini, B.Probst, S.Kato, A.Zuttel, W.I.F. David, S.Orimo, Energy Environ. Sci. 5 (2012) 6823. [2] P.A.Anderson, P.A.Chater, W.I.F.David, I.C. Evans, A.L.Kresting, Mater. Res. Soc. Symp.Proc. Vol. 1216 (2010) 1216-W09-05.

12:30 Lunch Break    
Session 3 : Torben R. Jensen
Authors : M. Dornheim, C. Pistidda, F. Karimi, N. Bergemann, S. Boerries, H. Cao, A.-L. Chaudary, A. Santoru, L. Thi Tu, G. Gizer, G. Capurso, C. Horstmann, O. Metz, J. Bellosta von Colbe, J. Jepsen, K. Taube, M. Wetegrove, N. Aubrift, N. Grove, N. Gupta, N. Benliman, T. Klassen
Affiliations : Department of Nanotechnology, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, 21502 Geesthacht Germany

Resume : Light weight metal or complex hydrides offer the potential for a safe and energy efficient hydrogen storage alternative for stationary as well as mobile applications. Highest energy efficiencies, however, are achievable only if both working temperature and the reaction enthalpy of the respective hydrogen sorption process can be attuned to the accompanying hydrogen consuming process in such a way that the required heat for hydrogen release of the hydride can be provided by the corresponding waste heat. Since the tailoring of reaction enthalpies is an important research task. One way to do this is to combine different hydrides which react during decomposition in an exothermal way with each other and thereby reduce the total value of reaction enthalpy while maintaining the average of the hydrogen capacities of the single hydrides. In this presentation, results concerning reaction mechanism, sorption behaviour, cycling stability of light weight hydrides and Reactive Hydride Composites in lab-size and tank-size are presented. The progress in tailoring reaction enthalpies and the optimisation of kinetics will be described.

Authors : O. Zavorotynska, S. Deledda, B. C. Hauback
Affiliations : Physics Department, Institute for Energy Technology, P.O. Box 40, NO-2027, Kjeller, Norway

Resume : Magnesium borohydride is a particularly interesting material for hydrogen storage due to its light weight and 14.9 wt% of hydrogen. Up to about 4 wt% was found to desorb reversibly below 300oC and at a moderate pressure [1]. For rehydrogenation of the completely dehydrogenated material, however, much harsher conditions are needed [2]. In order to improve hydrogen sorption performance of Mg(BH4)2, a wide range of approaches have been explored, including high energy reactive ball-milling, preparation of composite materials, dispersion in porous matrix, and addition of catalysts [3]. In this presentation the recent findings on hydrogen storage properties of Mg(BH4)2 will be summarized, including the results obtained in BOR4STORE [4,5]. Acknowledgements This work was financed by the European Fuel Cells and Hydrogen Joint Undertaking ( under collaborative project “BOR4STORE” (Grant agreement no.: N° 303428). References [1] G.L. Soloveichik, M. Andrus, Y. Gao, J.C. Zhao, S. Kniajanski, Int. J. Hydrog. Energy, 34 (2009) 2144-2152. [2] E. Rönnebro, 15 (2011) 44-51. [3] H.-W. Li, Y. Yan, S.-i. Orimo, A. Züttel, C.M. Jensen, Energies, 4 (2011) 185-214. [4] [O. Zavorotynska, I. Saldan, S. Hino, T.D. Humphries, S. Deledda, B.C. Hauback, J Mat Chem A, 3 (2015) 6592-6602. [5] I. Saldan, S. Hino, T.D. Humphries, O. Zavorotynska, M. Chong, C.M. Jensen, S. Deledda, B.C. Hauback, J. Phys. Chem. C, 118 (2014) 23376-23384.

Authors : Bo Richter, Mark Paskevicius, Torben R. Jensen
Affiliations : Center for Materials Crystallography, Interdisciplinary Nanoscience Center & Dept. of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark

Resume : An array of metal borohydrides are synthesized using a new protocol. Elemental metals are hydrogenated, yielding the corresponding metal hydrides (MHn) that are further reacted with a source of borane. We employ either the dimethylsulfide borane (DMSB) or tetrahydrofuran borane (THFB) complex as solutions in toluene and THF respectively. The reactions proceed to varying degrees of completion depending on specific reaction conditions and reagents, i.e. the influence of temperature, concentration and the type of reagents are evaluated. All reactions are performed near room temperature (RT to 40 C), thus avoiding the formation of undesired higher temperature polymorphs. Hence, we claim to achieve full ?polymorphic control? since we only form room temperature polymorphs. From these, other polymorphs can be synthesized using post-synthesis treatments. If impurities are present in the immediate reaction products, extraction of the desired metal borohydride can be achieved using an appropriate organic solvent, e.g. THF, Et2O, Me2S. Accordingly, this provides the solvate of the metal borohydride of interest, i.e. Ca(BH4)2∙2THF, Sr(BH4)2∙2THF, Mg(BH4)2∙?Me2S, etc. Reaction progress and final metal borohydride purity is assessed using X-ray diffraction and Rietveld refinement to establish the relative ratios between crystalline residual metal hydrides and the borohydride products.

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 : E. Callini,a,f,* P. Á. Szilágyi,b,c M. Paskevicius,c,d N. P. Stadie,a J. Réhault,e C. E. Buckley,c A. Borgschulte a and A. Züttel a,f
Affiliations : a Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory 505 Hydrogen & Energy, Überlandstrasse 129, 8600 Dübendorf, Switzerland; b University of Greenwich, Central Avenue, Medway Campus, Chatham Maritime ME4 4TB, United Kingdom; c Department of Imaging and Applied Physics, Fuels and Energy Technology Institute, Curtin University, GPO Box U1987, Perth WA 6845, Australia; d Department of Chemistry & iNANO, Aarhus University, Langelandsgade 140, Aarhus 8000, Denmark; e Politecnico di Milano, Piazza L. Da Vinci, 32, 20133 Milano, Italy; f EPFL, Swiss Federal Institute of Technology, Laboratory of Materials for Renewable Energy, Rue de l’Industrie 17, 1950 Sion, Switzerland.

Resume : Catalysis and energy conversion processes often involve the formation of thermodynamically unstable, transient and rapidly evolving species. Their detection and characterization are fundamental to understanding and controlling the underlying physical and chemical phenomena. The difficulties in storing and structurally characterizing these species limit their evaluation and exploitation for applications. In our recent work, the stabilisation of a gaseous, thermodynamically unstable species is achieved by incorporation in the nanocavities of a robust metal-organic framework. While the gas-phase molecules decompose rapidly after formation in inert atmosphere at ambient conditions [1], the adsorbed species are stable for months in the same conditions and even up to 350 K in vacuum. This novel approach opens new possibilities for the preparation, characterisation and storage of metastable compounds. [1] E. Callini, et al., JPCC 118 (1), 77 (2014).

15:30 Coffee Break    
Session 4 : Dag Noréus
Authors : Daniele Mirabile Gattia, Amelia Montone, Ilaria Di Sarcina
Affiliations : Materials Technology Unit, ENEA, Casaccia Research Centre, 00123 Rome, Italy

Resume : Application of solid compounds in tank for hydrogen storage requires suitable systems for heat management and correct gas flow. In the past it has been demonstrated that filling cylindrical tank with powder is detrimental for its continuous operation. The powder packs and sinters with increasing number of cycles and gas could not flow through it causing a reduction of mass of material which reacts with hydrogen. Consequently the storage capacity of the system decreases and kinetics become slower. In order to enhance heat management and gas contact the powder could be compressed in the form of pellets. Even if some agents, like carbon-based compounds, are used to enhance compressibility and mechanical properties of the pellets, a continuous increase of their dimensions takes place upon repeated cycling [2]. Increasing the pressure of compaction of the pellets demonstrated to reduce swelling effects [3]. For these reasons a new procedure of preparation has been developed in order to reduce the effects of cycling and to obtain a more stable system to be applied in tank for hydrogen storage. Light and Electron Microscopy, X-Ray diffraction have been used for the analysis of samples prepared before and after cycling, performed in a Sievert’s type apparatus. [1] H-P. Klein, M. Groll, Int J Hydr En, 29, 1503 (2004); [2] D. Mirabile Gattia, A. Montone, L. Pasquini, Int J Hydr En 38, 1918 (2013); [3] D. Mirabile Gattia, G. Gizer, A. Montone, Int J Hydr En, 39, 9924 (2014)

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 : Marco Calizzi, Domizia Chericoni, Luca Pasquini
Affiliations : Alma Mater Studiorum - University of Bologna, Department of Physics and Astronomy

Resume : Magnesium hydride (MgH2) is a material of great interest in the field of hydrogen (H) storage because it is abundant, low-cost and light. However, MgH2 is too stable for practical H desorption and suffers from slow kinetics. Reduction of the crystallite size down to the nanoscale and addition of titanium (Ti), a catalyst known to improve both dissociation of H2 molecules and diffusion of H atoms in the material, are two strategies that can improve MgH2 performances. For the synthesis we used a bottom-up physical vapor deposition technique, the Inert Gas Condensation, to produce Mg-Ti nanoparticles employing a modified set-up that also allows in situ hydrogenation. Multiple samples with Ti content varying over a wide range, from 3 to 53 at.%, were synthesized. Morphological and structural characterization of the as prepared samples was carried out by Scanning Electron Microscopy and X-Ray Diffraction. H-storage properties such as capacity, kinetics and cycling stability were investigated with a Sievert apparatus and a High Pressure Differential Scanning Calorimeter. This work focuses on the study of H-sorption properties in the low temperature range for Mg-based materials, between 200 and 300 °C, reporting greatly enhanced kinetics and reduction of activation energy while keeping high storage capacities, up to 5.2 wt.%. From the analysis of pressure-composition isotherms we obtained enthalpy and entropy of hydride formation compatible with the values determined in bulk MgH2.

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 : Larissa Popilevsky , Vladimir Skripnyuk , Michael Beregovsky , Yaron Amouyal , Meltem Sezen , Eugen Rabkin
Affiliations : Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa, Israel;Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa, Israel;Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa, Israel;Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa, Israel;Sabanci University Nanotechnology Research and Application Center, Tuzla, Turkey;Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa, Israel

Resume : Magnesium is considered as one of the most attractive materials for hydrogen storage because of its high hydrogen storage capacity and abundance. One of the drawbacks of Mg as a hydrogen storage material is its high hydride formation enthalpy. For the hydrogenation reaction to proceed, the heat should be quickly removed, while for the endothermic desorption process, the heat supply is crucial. Thus, the ability of Mg-based matrix to conduct heat often represents the kinetic “bottleneck” determining the hydrogenation kinetics. Among various carbonaceous additives to Mg, carbon nanotubes exhibit one of the best catalytic effects. They are also excellent thermal conductors: thermal conductivity of the individual multi-wall carbon nanotube (MWCNT) can reach up to ~3000 W/mK at the ambient temperature [1]. However, the mass-produced MWCNTs are randomly oriented and entangled inside the agglomerates. Numerous junctions between the nanotubes segments inside these agglomerates turn them into thermal insulator rather than conductors. Ball-milling is a processing method that can easily disperse the undesired agglomerates, while tuning morphologies and properties of the MWCNTs and their derivatives. In this work we studied the influence of ball-milling conditions on the obtained morphology, hydrogenation kinetics and thermal conductivity of Mg admixed with MWCNTs. It was shown that it is possible to produce mechanically stable pelletized magnesium-carbon composite with improved hydrogenation kinetics, while minimizing thermal conductivity loss. The microstructure of the porous pelletized composites was determined and it was found that prolonged ball milling leads to a partial destruction of the MWCNTs. The role of carbonaceous derivatives of the MWCNTs in enhancing the hydrogen storage properties and thermal conductivity of the pelletized composites was discussed. This work was supported by the Israel Strategic Alternative Energy Foundation (I-SAEF). 1. P. Kim, L. Shi, A. Majumdar, and P. L. McEuen, Phys. Rev. Lett. 2001, 87, 215502..

Authors : Janis Kleperis, Peteris Lesnicenoks, Liga Grinberga, Georg Chikvaidze
Affiliations : Institute of Solid State Physics of University of Latvia

Resume : Natural and synthetic zeolites (clinoptilolite group) as nanoporous material and few layer graphene layers as nanostructured material are subjects of research for reversible hydrogen adsorbtion/desorption. For enhancement of hydrogen storage the chemical, electrochemical and extraction pyrolysis methods for intercalation of materials are performed with metal and non-metal species (Pd, Pt, Li, Mg, NH3 etc). Spectroscopic (FTIR, Raman) methods are applied to detect hydrogen in atomic (bond O-H or C-H) or molecular (H2) form on the surface (and in the bulk) of material. Sievert type volumetric method in temperature region 100-500 K is applied to study an amount of adsorbed/desorbed hydrogen. As it is concluded from results, intercalation of nanoporous zeolite materials is increasing amount of bounded hydrogen. Two types to bind hydrogen with substrate material are proposed – strongly and weakly bonded to material, accordingly next mechanisms: (a) splitting of molecular hydrogen onto catalytic centers (introduced metals) into atomic hydrogen, spillover to specific surface states on substrate material (defects, dopants); and (b) physical adsorption of molecular hydrogen. Synergy between both adsorption mechanisms could increase amount of adsorbed hydrogen.

C.C I.1
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 : Keith Linehan, Darragh Carolan, Hugh Doyle
Affiliations : Tyndall National Institute, University College Cork, Lee Maltings, Cork, Ireland

Resume : The development of highly efficient hydrogen storage materials is one of the main challenges that must be tackled in a widely expected hydrogen economy. Physisorption in nanoscale materials with high surface areas and chemisorption in hydrides are the two main options for solid state hydrogen storage, and both options possess their inherent advantages and drawbacks. Carbon-based materials are the most intensively studied candidates for reversible H2 storage due to their low density, high surface area and pore volume, high thermal and chemical stability, and they are easy to manufacture in large quantities with low cost. Here we report the preparation and characterisation of high surface area carbon quantum dots (CQDs) synthesised with high size monodispersity using a simple room temperature, solution-phase synthesis. Regulation of the quantum dot size is achieved by using surfactants used to form the inverse micelles, while covalently bound capping molecules (ligands) chemically passivate the CQD surface to prevent oxidation. The excellent CQD size monodispersity observed allows for highly efficient packing of CQDs in confined dimension, while maximising available surface area. Varying the capping ligands allowed the CQDs to be dispersed in either hydrophobic or hydrophilic solvents. CQDs were stable under ambient atmospheric and lighting conditions over a period of months, with no evidence of oxidation.

C.C I.3
Authors : Maria Baikousi,1 Theodore Tsoufis,1 Dimitra Giasafaki,1 Georgia Charalambopoulou,2 Fotios Katsaros,1 and Theodore Steriotis.1
Affiliations : 1. Institute of Nanoscience & Nanotechnology, National Center for Scientific Research “Demokritos”, 15341, Athens, Greece. 2. Institute of Nuclear & Radiological Sciences and Technology Energy & Safety, National Center for Scientific Research “Demokritos”, 15341, Athens, Greece.

Resume : Carbon based nanostructures are particularly attractive for hydrogen storage since carbon is a light element. In particular, graphene-based nanostructures show the most favorable gravimetric density among known carbon based materials. Very interestingly, the hydrogen storage capacity of graphene based nanostructures increases sharply in the case of 3D, multilayered conformations where the graphene sheets are spaced by guest molecules leading to pillared graphenes. Carbon NanoDiscs (CND) can be described as discshaped graphene sheets stacked atop each other, resulting to welldefined (in terms of size distribution, shape and structure) graphitic nanostructures. We report the development of CND based multilayered, nanostructured materials exhibiting tailored interlayer spaces. Well established chemical strategies were employed for the introduction of functional chemical groups along the graphitic framework of starting CND. Next, a series of guest species (i.e. adamantylamine, dendritic polymers, silsesquioxanes) were successfully introduced within the interlayer space of the modified CND, resulting to an increased interlayer distance along caxis, and yielding pillared, “sandwichlike” hybrid CND structures. In certain cases, the final pillared CND structures were further decorated with Pd nanoparticles (grown insitu) towards further increasing their hydrogen storage capacity.

C.C I.4
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
Poster Session I : -
Authors : † I. Bratsos,† Ch. Tampaxis, ‡ I. Spanopoulos, § N. Demitri, † D. Vourloumis, † G. Charalambopoulou, ‡ P. Trikalitis, † Th. Steriotis
Affiliations : † National Center for Scientific Research “Demokritos”, 15341 Agia Paraskevi Attikis, Athens, Greece ; ‡ Department of Chemistry, University of Crete, Voutes 71003 Heraklion, Greece ; § Elettra – Sincrotrone Trieste, S.S. 14 Km163.5 in Area Science Park, 34149 Basovizza, Trieste, Italy

Resume : Metal-organic frameworks (MOFs) are currently an extremely active area in materials research mainly because of their remarkable attributes, which make them potential candidates for numerous applications including hydrogen storage. The development of porous MOFs combining open metal sites with organic linkers of predetermined shape, bearing functional groups, can lead to specific and selective recognition of guest molecules which is crucial for the gas sorption properties of such materials. Herein, we report on the synthesis of a novel heterobimetallic In(III)-Pd(II) MOF, formulated as [In3O(Pd2(PDC)2Cl2)1.5(H2O)3][Cl] (PDC = 3,5-pyridine dicarboxylate), with rare soc (square octahedron) topology, following the “metalloligand” approach (i.e. a metal-organic complex serves as linker instead of a pure organic ligand). The novel mixed metal organic framework was characterized by a wide range of methods (elemental analysis, TGA, SEM/EDS, FT-IR spectroscopy, powder and single-crystal X-ray diffraction analysis, as well as N2 and Ar sorption studies), which revealed a highly ionic framework (due to its open metal sites and localized charge density) and relatively narrow pores (< 1nm), important features for hydrogen storage applications. Hydrogen adsorption measurements over a range of temperatures (77-100K) and up to 1bar, showed that the new MOF material has interesting H2 uptake properties, both in terms of gravimetric capacity and isosteric heat of adsorption values.

C.C I.6
Authors : Andrzej Aksenczuk, Andrzej Calka
Affiliations : University of Wollongong, Australia

Resume : The conventional hydrogen storage approaches of compressed hydrogen gas and cryogenic hydrogen liquid are not capable of meeting the targets for commercial applications. Hydrogen storage via metal hydride materials have the advantages of high volumetric and gravimetric capacities and safety. So far, many kinds of hydrogen storage materials have been developed, but all of these materials fail to satisfy all the necessary requirements due to one or more drawbacks, including unfavorable thermodynamics, poor kinetics, irreversibility, and release of undesirable by-products. In this study for the first time we use electric discharge assisted mechanical milling (EDAMM) method to synthesis metal hydrides in hydrogen plasma. In our process, under electric discharge hydrogen forms free radicals that penetrate the metal structure with very low entry energy barrier. Hydrogenation solubility in zirconium, niobium and magnesium powders was studied using EDAMM method. It is shown that the hydrogen solubility in Zr powder was 1.92 wt% for niobium 0.426 wt% and for magnesium 1.5 wt%. The composition, phase component, and hydrogen storage properties were analyzed by using XRD, and CHN microanalysis. The above results indicated that Zr and Nb have a good hydrogen sorption and the effect can be better achieved after fine tuning of the discharge conditions.

C.C I.7
Authors : Dmytro Korablov a,b, Flemming Besenbacher c, Torben R. Jensen a
Affiliations : a Center for Materials Crystallography (CMC), Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Denmark,; b Institute for Problems of Materials Science, NASU, Kyiv, Ukraine; c Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, Denmark

Resume : Last decades of research in the field of new materials for hydrogen storage were directed to a large degree towards magnesium and Mg-based alloys, which can reversibly store ~ 7.6 wt% of hydrogen. Such sorption capacity combined with low cost suggests that magnesium and its alloys may have advantages in the systems for hydrogen storage. However, the cyclic stability of these materials and their performance at mild temperature conditions are far from satisfactory. Hydrogenation / dehydrogenation properties of the Mg-MgH2 system can be improved by mechanochemical treatment of magnesium with the addition of transition metals (TM). In this study the influence of TM additives on the room temperature (RT) hydrogen absorption characteristics of nanocomposites based on magnesium, obtained by reactive ball milling under hydrogen in a high energy planetary mill, was explored. On the base of calculated values of the Gibbs free energy for reaction of hydrogen absorption (ΔG < 0) it can be concluded that hydrogenation reaction could thermodynamically proceed at room temperature, which was experimentally confirmed for all of the studied composites. Comparative analysis of the Mg-Ti, Mg-V and Mg-Nb systems makes it possible to establish that the most effective additive facilitating hydrogen uptake at RT is vanadium. It provides the degree of conversion into hydride phase α = 0.86 for the first minute of hydrogenation. In contrast, additives of Nb and Ti provide only α = 0.62 and 0.36, respectively, indeed after 30 min of exposure. The observed effect is associated with the exceptional hydrogen permeability of vanadium that minimizes the role of hydrogen diffusion in the formation of magnesium hydride.

C.C I.8
Authors : E. Kościuczyk, T. Czujko, M. Norek
Affiliations : Department of Advanced Materials and Technologies, Military University of Technology, Kaliskiego 2, 00-908 Warsaw, Poland

Resume : Comparative study of the commercially available hydrides have been done. Well known magnesium hydride and titanium hydride have been characterized using stereological and thermodynamic methods to see if there are some similarity. The particle size and the shape of the MgH2 and TiH2 powders have been checked using various methodology (SEM, NIS, IPS, BET). These results have been compared with raw and milled state. The powders were milled by planetary ball mill in a sequence time of milling (from 15 to 300 minutes). In addition, thermodynamic measurements of each of samples have been made. Differential scanning calorimetry results shows that significant changes occur upon relative short time of milling. Furthermore, X-ray method has enabled to obtain the crystallite size of the powders after the ball milling process. The particle size of the powders and the surface area has direct impact to hydrogen storage capacity. The research were made for two thermodynamically different hydrides to prove the trend of changes.

C.C I.9
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
Authors : Efrat Ruse, Svetlana Pevzner, Ilan Pri-Bar, Vladimir M. Skripnyuk, Eugen Rabkin and Oren Regev
Affiliations : Department of Chemistry, Nuclear Research Center Negev, P.O.B.9001, 84190 Beer Sheva, Israel Department of Chemical Engineering, Ben-Gurion University of the Negev, 84105 Beer Sheva, Israel Department of Materials Science & Engineering, Technion - Israel Institute of Technology, Haifa 32000, Israel

Resume : Hydrogen storage kinetics is significantly improved by utilizing hydrogen spillover agents such as carbonaceous additives in the presence of transition metal catalyst. We define a figure of merit (FOM) to quantify the de/hydriding performance and catalyst concentration of various reported studies, and found that the fastest kinetics is obtained for our Pd-decorated carbon nanotubes. Our findings may help to design an efficient hydrogen storage system.

C.C I.12
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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 : Sheng Guo, Daniel Reed, David Book
Affiliations : School of Metallurgy and Materials, University of Birmingham, Birmingham, B15 2TT, United Kingdom

Resume : Mixed borohydride compounds, offer the prospect of more favourable thermodynamic properties and lower decomposition temperatures, and so have been considered as hydrogen storage media. In the binary LiBH4-Ca(BH4)2 system, samples prepared by ball milling were found to exist as physical mixtures, which exhibited eutectic melting at around 200 ?C [1]. An in situ NMR study demonstrated that the LiBH4-Ca(BH4)2 mixture can form a solid solution below the eutectic melting point [2]. However, both the mechanism of the exchange of the cations between the borohydrides, and the reaction pathways during decomposition at higher temperatures, need further exploration. In this work, the thermal stability and decomposition pathway of an eutectic mixture LiBH4-Ca(BH4)2 was studied by DSC-TGA-MS, in situ XRD and Raman measurements. A new phase is observed when heating and cooling the sample between phase changes and eutectic points for three cycles. The identification of this phase is ongoing, however, it does not appear to correspond to known borohydrides or borohydride-borates. In which case, this phase may be tentatively ascribed to a metastable dual-cation borohydride. A series of phase and melting reactions, and the formation of CaB6, Li2B12H12, amorphous boron and an unknown compound are observed in the Raman spectra as a function of temperature. Ref. [1] J.Y. Lee et al., J. Phys. Chem. C, 2009, 113, 15080. [2] Y.Yan et al., J. Phys. Chem. C 2013, 117, 8878.

Authors : Yong Seok Choi (1,2), Kyu Hwan Oh (1), Young-Su Lee (2), Young Whan Cho (2)
Affiliations : (1) Department of Materials Science and Engineering, Seoul National University, Seoul 151-742, Republic of Korea (2) High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea

Resume : In this study, we introduce a LiBH4-Ca(BH4)2 composite infiltrated into mesoporous scaffolds (SBA-15, MCM-41) as a fast lithium ionic conductor. It has been known that the eutectic composition of LiBH4-Ca(BH4)2 (LC) composite shows low melting temperature, and the potential for high Li ion mobility has been revealed by previous NMR studies. We therefore systematically investigate the ionic mobility of the eutectic LC composite melt-infiltrated into a mesoporous silica scaffold, as a candidate for a fast Li ionic conductor. The melt-infiltration of LiBH4-Ca(BH4)2 into mesoporous silica scaffolds was conducted under hydrogen atmosphere and was confirmed by X-ray diffraction analysis. The ionic conductivity was measured by electrochemical impedance spectroscopy as a function of temperature. Infiltrated LC composite exhibits much enhanced conductivity at room temperature, which is two orders of magnitude higher than that of bulk LiBH4, and the conductivity reaches ~10-3 S/cm at 400 K. We believe that such kind of composite material can be further engineered to be applicable for a solid electrolyte of lithium ion battery.

Authors : S. Garroni, L. Fernández Albanesi, P. Arneodo Larochette, P. Nolis, C. Pistidda, E. Napolitano, P. Moretto, M. Dornheim, C. Milanese, G. Mulas, S. Enzo, M. D. Baró, F. C. Gennari
Affiliations : 1) S. Garroni, G. Mulas, S. Enzo: Departament of Chemistry and Pharmacy, University of Sassari and INSTM, Via Vienna 2, I-07100 Sassari, Italy 2)L. Fernandez Albanesi, P. Arneodo Larochette and F.C. Gennari: 2Centro Atómico Bariloche (CNEA) e Instituto Balseiro (UNCu), R8402AGP Bariloche, Río Negro, Argentina 4) P. Nolis: Servei de Ressonància Magnètica Nuclear (SeRMN), Universitat Autònoma de Barcelona, E-08193. Bellaterra, Spain 5) M.D. Barò: Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain 6) E. Napolitano, P. Moretto: European Commission – DG Joint Research Centre-Institute for Energy and Transport, Westerduinweg 3, NL-1755 Petten, The Netherlands. 7) C. Pistidda, M. Dornheim: Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht, Max-Planck-Straße 1, D-21502 Geesthacht, Germany 8) C. Milanese: Pavia H2 Lab, Department of Chemistry, Physical Chemistry Division, University of Pavia, Viale Taramelli 16, I-27100 Pavia, Italy

Resume : In the field of the hydrogen-based storage technology, large interest is addressed towards a class of materials based on metal amides, due to their high hydrogen gravimetric densities and good reversibility [1]. Among them, although the very promising thermodynamic properties of the these systems are close to the target for practical applications, the release of hydrogen can be achieved only after long time due to the severe kinetic barrier of the sorption reactions. To this, different strategies have been inspected to improve the hydrogen sorption performance of the LiNH2-LiH system, although kinetic constraints have been partially alleviated but not totally overcome. In particular, AlCl3 addition seems to improve significantly the hydrogen storage properties of the LiNH2-1.6LiH composite [2]. In this work we investigated structural and hydrogen storage properties of different LiNH2-1.6LiH systems doped by Al-based dopants. Particular emphasis will be addressed to the formation of a new halide Li-N-H phase formed by the interaction of the starting reactants and which plays a key role in the reversible hydrogen storage of the system. The reaction pathways and the possible intermediates formed during milling, posterior heating under hydrogen pressure and hydrogen desorption/absorption, were investigated by differential scanning calorimetry (DSC), in situ and ex-situ X-ray powder diffraction (XPRD), solid-state MAS nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared analysis (FTIR). References: [1] - J. Wang, W.H. Li, P. Chen, MRS BULLETIN 38 (2013) 480. [2] - Fernández Albanesi, L.; Arneodo Lorochette, P.; Gennari, F.C. Destabilization of the LiNH2–LiH hydrogen storage system by aluminum incorporation. Int. J. Hydrogen Energy 2013, 38, 12325–12334.

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.

10:30 Coffee Break    
Session 6 : David Book
Authors : A.V. Skripov
Affiliations : Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg 620990, Russia

Resume : Two basic types of atomic jump motion are known to exist in complex hydrides: reorientational motion of complex anions (BH4, NH2, AlH4, B12H12, B10H10,…) and translational diffusion of metal cations and complex anions. Both these types of motion will be addressed in our work presenting a review of recent nuclear magnetic resonance (NMR) studies of the mechanisms and parameters of atomic jump motion in complex hydrides. In favorable cases, the NMR appoach allows us to trace the atomic jump rates over the dynamic range of 8 orders of magnitude (10^4 – 10^12 s^-1). Another experimental technique that is effective for studies of atomic motion at the microscopic level is quasielastic neutron scattering (QENS). Although QENS measurements probe the atomic jump rates over more limited dynamic range (10^9 – 10^12 s^-1), they can give indispensable information on the spatial aspects of atomic motion. Examples of complementarity between NMR and QENS approaches to studies of dynamic properties of complex hydrides will be discussed. We shall focus on the systems exhibiting high cation diffusivities (bimetallic borohydrides, borohydride-amides, B12H12- and B10H10-based compounds). We shall also address the relation between the reorientational motion of complex anions and the translational diffusion of metal cations.

Authors : Michael Hirscher, Julia Teufel, Hyunchul Oh, Ingrid Weinrauch and Margarita Reschke
Affiliations : Max Planck Institute for Intelligent Systems, Stuttgart, Germany

Resume : In microporous materials hydrogen isotopes can be separated by either confinement in small pores i.e. “Quantum Sieving” or by strong adsorption sites i.e. “Chemical Affinity Quantum Sieving”. MOFs are excellent candidates for studying these quantum effects due to their well-defined pore structure and the possibility to introduce strong adsorption sites directly into the framework. Doped or functionalized samples of the robust MFU-4 series possessing optimized pore aperture or open metal sites, respectively, have been investigated for their hydrogen separation capability. The samples have been exposed to an isotope mixture and the adsorbed quantity of each isotope was detected by low-temperature thermal desorption spectroscopy (TDS). The ratio of the desorbed amount of deuterium and hydrogen leads directly to the selectivity (separation factor). The selectivity is determined as a function of exposure time and temperature and exhibits the highest value observed at temperatures well above the boiling point of liquid nitrogen. The results will be discussed regarding possible technical applications.

Authors : Magnus H. Sørby, Henrik Mauroy, Bjørn C. Hauback
Affiliations : Institute for Energy Technology (IFE), Kjeller, Norway

Resume : The high cost of vanadium is a major drawback for hydrogen storage in V-based bcc alloys. The cost can be greatly reduced by replacing pure vanadium with ferrovanadium (V~0.8Fe~0.2) with the penalty of lower hydrogen capacity. The high degree of atomic disorder in multi-metal bcc alloys and their hydrides makes it challenging to understand structure-property relations by regular powder diffraction or computational methods alone. Still, such relations are crucial to understand in order to intelligently improve the properties of these alloys. Total neutron scattering measurements coupled with pair-distribution function (PDF) analysis and Reverse Monte Carlo modelling is a powerful tool to extract information about short-range atomic order in disordered hydrides. Such measurements have been performed at ISIS (UK) and Budapest Neutron Center (Hungary) on a series of Ti-V-Fe-based bcc-deuterides. The obtained structural information is presented with special emphasis on the local structure around Fe which provides a clear structural reason for the iron-induced loss of hydrogen capacity.

Authors : F. Leardini1, J.R. Ares1, C. Granero1, A. Martin1, A.R. Galvis E1, M. Barawi1, M. Montiel2, C. Zlotea3, F. Cuevas3, J.F. Fernandez1, C. Sanchez1
Affiliations : 1 Dpto. de Fisica de Materiales. Universidad Autonoma de Madrid, 28049, Madrid, Spain / 2 Dpto. de Quimica Fisica Aplicada, Universidad Autonoma de Madrid, 28049, Madrid, Spain / 3 CMTR/ICMPE/CNRS-UPEC, UMR 7182, 2-8 rue Henri Dunant, 94320 Thiais Cedex, France.

Resume : There are numerous reports investigating the size effects on the solubility of hydrogen in metals [1], in particular in Pd. However, little is known about the corresponding solubility for deuterium and the related influence of particle size on the thermodynamic and kinetic isotope effects. In this work, we investigate the thermodynamic and kinetic properties of Pd-H and Pd-D systems of four Pd samples with different sizes ranging from bulk to nano (< 3nm) scale. The samples have been structurally, compositionally and morphologically characterized by different techniques (XRD, FTIR, SEM, TEM). Absorption and desorption pressure composition isotherms (PCI) have been obtained in a Sieverts reactor with H and D isotopes at 23, 50 and 70 ºC for all the samples. These measurements provide the enthalpies and entropies of H(D) absorption and desorption in Pd. A drastic change of the thermodynamic properties induced by size effects is observed for Pd nano-particles with sizes below 3 nm. Moreover, kinetic isotope effects have been investigated both in absorption and desorption. The obtained results provide useful information about the fundamental aspects of H and D absorption/desorption in Pd at the nano-scale as well as the influence of size effects on the isotope separation factor in Pd. [1] C. Zlotea, M. Latroche, Colloids and Surfaces A: Physicochem. Eng. Aspects, 439 (2013) 117-130

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.

12:30 Lunch Break    
Session 7 : Tayfur Öztürk
Authors : Umit B. Demirci
Affiliations : IEM (Institut Europeen des Membranes), UMR5635 (CNRS, ENSCM, UM), Université de Montpellier, Place Eugene Bataillon, CC047, F-34095, Montpellier, France

Resume : Among the solid- and liquid-state chemical hydrogen storage materials, B- and N-based compounds have attracted much attention owing to high theoretical gravimetric hydrogen densities (15-20 wt%) and “low” dehydrogenation temperatures (<200°C, by presence of both protic and hydridic hydrogens). Ammonia borane H3N-BH3 (AB) is a typical example. It has been much investigated, particularly through the development of strategies to improve its dehydrogenation properties. One of the strategies is chemical modification (towards derivatives), and hydrazine borane H2N-(H2)N-BH3 (HB), another example of B- and N-based compound, can be seen as a derivative also, where the NH3 moiety in AB has been substituted by a N2H4 group. However, HB in pristine state is not suitable for solid-state chemical hydrogen storage. Like for AB, derivatives have been then considered. First examples of derivatives are alkaline hydrazinidoboranes H2N-(HM)N-BH3, obtained by reaction (exothermic) of HB and an alkaline hydride MH (M = Li, Na, K). Another example of derivative of HB is hydrazine bisborane H3B-(H2)N-(H2)N-BH3 (HBB), where the H2N-(H2N)-BH3 entity is complexed with an additional BH3 group. However, the suitability of HBB for chemical hydrogen storage has shown to be controversial… The E-MRS Fall Meeting 2015 will be the opportunity to give a specific overview of the potential of such boranes in the field of chemical hydrogen storage while distinguishing solid- and liquid-state storage.

Authors : C. Pistidda,*,1 A. Santoru,1 S.Garroni,2 N. Bergemann,1 A. Rzeszutek,1 C. Horstmann, 1C. D. Thomas,3 T. Klassen,1 M. Dornheim 1
Affiliations : 1Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Strasse 1, D-21502 Geesthacht, Schleswig-Holstein, Germany; 2Department of Chemistry and Pharmacy and INSTM, Via Vienna 2, I-07100 Sassari, Italy; 3MAX IV Laboratory, Lund University, Römers väg 1, 22363 Lund, Sweden;

Resume : In this work we report on the first in situ synchrotron radiation powder X-ray diffraction study (SR-PXD) of the ammonolysis reaction of selected alkaline and alkaline earth metal hydrides (i.e. LiH, NaH, KH, MgH2 and CaH2). The investigation was performed using an in situ SR-PXD pressure cell at an initial NH3 pressure of 6.5 bar in a range of temperature between room temperature (RT) and 350 °C. The results of this work give new important insights into the formation of metal amides and imides starting from the corresponding metal hydrides. LiH was observed to react with NH3 to form LiNH2 already at RT, then, it decomposes into Li2NH at 310 °C through the formation of non-stoichiometric intermediates of the Li1+xNH2-x form. The formation of NaNH2 takes place nearly at RT (28 °C) and it melts at 180 °C. As for LiH, KH reacts with NH3 at RT to surprisingly form, what it seems to be, cubic KNH2. However, we believe this phase to be a solid solution of KH in KNH2. At high temperature, the possible formation of several solid solutions of K(NH2)1-yHy with defined composition is also observed. The formation of Mg(NH2)2 was observed to starts at around 220 °C, from the interaction γ-MgH2 and NH3. At 350 °C, when all γ-MgH2 is consumed, the formation of Mg(NH2)2 stops and MgNH is formed by the reaction between β-MgH2 and NH3. Our results indicate that the formation of the γ-MgH2 is a key step in the synthesis of Mg(NH2)2 at low temperature (e.g. via ball milling technique). CaH2 was observed to react with NH3 at around 140 °C to form CaNH. At higher temperature the appearance of new reflections of possible Ca1+xNH phases, with the same crystalline structure of CaNH but with a smaller cell parameter was observed.

Authors : Miriam Rueda, Luis Miguel Sanz-Moral, Angel Martin
Affiliations : Department of Chemical Engineering and Environmental Technology, University of Valladolid c/ Doctor Mergelina s/n 47011 Valladolid (Spain)

Resume : The application of hydrogen as energy vector is attracting more attention as solution to mitigate the problems related to the depletion of fossil fuels and their non desirable emmisions. However, it requires the development of new hydrogen storage systems. Among the different solid hydrogen storage alternatives, ammonia borane (AB) is a promising hydride due to both the large gravimetric capacity (19.6%wt H2) and volume (140 g/L), moderate decomposition temperature, its non-toxicity and stability at room temperature. However, this hydride still presents kinetic limitations due to long induction times and the emission of volatiles byproducts. The objective of this work is to develop a new solid state hydrogen storage material based on AB nanoparticles stabilized in low-density aerogels. For this purpose, AB has been confined in the pores of microparticles of hydrophilic silica aerogel by wet impregnation using sub critical carbon dioxide as drying method. It was found that more than 60%AB can be stored in the pores of the support enhancing the final properties, both structural and textural, of the hydrogen storage material. It has been obtained a high improvement in the H2 release kinetic, a high reduction (70ºC) of onset and peak temperature decomposition and a supression of volatile subproducts in contrast to neat AB. This fact is due to a significant reduction in the mean size of AB after confinement and the presence of SiOH and SiOSi groups related to silica aerogel.

Authors : A. Laikhtman (1), A. Fruchtman (1), G. Makrinich (1), A. Zak (1), T. K. Kim (2), H. R. Moon (2), M. Sezen (3), J. I. Martinez (4), J. A. Alonso (5), D. Dinescu (6), M. Enachescu (6)
Affiliations : (1) Holon Institute of Technology (HIT), Holon, Israel; (2) Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea; (3) Sabanci University, Istanbul, Turkey; (4) Instituto de Ciencia de Materiales de Madrid, Madrid, Spain; (5) University of Valladolid, Valladolid, Spain; (6) University Politehnica of Bucharest, Bucharest, Romania

Resume : Inorganic nanotubes (INT) and inorganic fullerene-like (IF) nanoparticles (NP) of WS2 are exploited as media for hydrogen storage. Exposure to high pressure unactivated hydrogen at room and high temperatures (300-573 K) resulted in measurable but low absorption concentration. Lowing the hydrogen temperature to 77-196 K doubled the absorption rate. But it was the usage of hydrogen activated by radiofrequency (RF) and microwave plasmas that dramatically increased the efficiency of its absorption. Chemical configuration of the absorbed hydrogen is of primary importance as it affects its absorption efficiency as well as stability and possibility of release. Micro-Raman spectroscopy was applied to elucidate chemical bonding of hydrogen and to distinguish between chemi- and physisorption. To provide stronger confirmation for hydrogenation by plasma treatment, deuterium was used instead of hydrogen in some treatments. It was proved that in all plasma-hydrogenated samples of WS2 NP, hydrogen was absorbed in its molecular form, H2, being intercalated, owing to the layered structure of the WS2. It was shown that hydrogen is mostly stable under high vacuum conditions at room temperature, which supposed its stability at the ambient atmosphere. To explain our experimental results we present here a model simulating the absorption of hydrogen in the WS2 NP. This model elaborates on the absorption sites and the preferential location of the absorbed hydrogen.

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.

15:30 Coffee Break    
Symposia A & C Joint Session : Main building, Room 134 - Chair: Theodore Steriotis
Authors : Gour P. Das
Affiliations : Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata-700032, INDIA

Resume : In search of the right material for hydrogen storage, complex hydrides involving light metals, such as Alanates, Imides, Borates, Amidoboranes etc. [1,2] show impressive gravimetric efficiencies, although the hydrogen desorption temperatures turn out to be rather high. Nanostructuring (via ball milling) is expected to improve the desorption enthalpy as well as the desorption temperature due to the higher diffusivity of hydrogen and higher surface to volume ratios of the nanoclusters [3]. Apart from hydrides, there are other kinds of novel materials that have been investigated, e.g. carbon based materials activated with nano-catalysts, metal-organic complexes, and more recently nanostructured cages viz. fullerenes, nanotubes and graphene-like 2D sheets decorated with simple or transition metals that serve to attract hydrogen in molecular form [4-6]. In this talk, I shall discuss the results of our first principles density functional theory (DFT) based investigation of the structure, stability and desorption kinetics of H2 focus on both the two above mentioned classes of materials. Some outstanding issues and challenges, like how to circumvent the problem of metal clustering on surface, or how to bring down the hydrogen desorption temperature etc. will be discussed. Finally, I shall present a comparative study of the different kinds of stable nanostructured materials with large surface area, from the point of view of their promise and practicability for hydrogen storage. [1] S. Bhattacharya et al, J. Phys. Chem. C Letter 112, 11381 (2008); J. Phys. Chem C 116, 8859 (2012). [2] S. Bhattacharya and G.P. Das, Review Article in ‘Concepts and Methods in Modern Theoretical Chemistry’, Eds. S.K .Ghosh and P.K. Chattaraj (CRC Press, 2013) pp. 415-430. [3] P. Banerjee, K.R.S. Chandrakumar and G.P. Das, communicated (2015). [4] S. Barman et al, J. Phys. Chem. C 112, 19953 (2008). [5] S. Bhattacharya et al, J. Phys. Chem. C Letter 112, 17487 (2008); Bull. Mater. Sci. 32, 353 (2009); J. Phys. Chem. C 113, 15783 (2009); J. Phys. Chem. C 116, 3840 (2012). [6] A. Bhattacharya et al, J. Phys. Chem. C 114, 10297 (2010).

Authors : Robert Johansson, Rajeev Ahuja, Olle Eriksson, Björgvin Hjörvarsson, Ralph H. Scheicher
Affiliations : Department of Physics & Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden

Resume : The site occupancy of hydrogen atoms in strained body-centered cubic vanadium is investigated using density functional theory. Predominant occupancy of either the tetrahedral or the octahedral interstitial sites results from the different effect by the strain state of the material. Interstitially absorbed hydrogen will itself give rise to local strain fields in the material. For large enough hydrogen concentrations, the sum of these local strain fields will combine to give rise to a change in volume which in turn alters the energetic landscape of the absorbed hydrogen. We predict that a change in site occupancy from tetrahedral to octahedral will occur at a critical strain at which the energetics of hydrogen site occupancy becomes equal. We also predict hysteresis behavior in the site occupancy during the loading and unloading of hydrogen in the system. This phenomenon has been experimentally observed and theoretical calculations that will be presented provide an atomistic insight to the underlying process.

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 : Didier Blanchard (1), Agata Bialy (2), Peter B. Jensen (1), Tejs Vegge (1), Ulrich J. Quaade (2)
Affiliations : 1- DTU Energy Conversion, 2800 Kgs. Lyngby, Denmark; 2- Amminex Emissions Technology A/S, Gladsaxevej 363, 2860 Soeborg, Denmark

Resume : Metal halide ammines are very attractive materials for ammonia absorption and storage1. Applications include thermochemical heat pumps2, NH3 separation3, storage4 for fuel cells5 and selective catalytic reduction of NOx from combustion processes6. However, the release of NH3 from metal halides often occurs in multiple steps and at too high temperatures for these applications. Therefore, there is a need for new materials and to search for new mixed metal halide chlorides, we use Density Functional Theory calculations, guided by a genetic algorithm to expedite the search (the defined search space contains more than 100,000 different structures). We search for materials releasing ammonia below 100 ?C. The efficiency of the implemented algorithm is verified by 3 trial runs capable of finding the same optimal mixtures starting from different random populations, testing < 5% of the candidates. Some of the best candidates are already confirmed experimentally and others offer a record high, accessible hydrogen capacity exceeding 9 wt%. Among the identified materials is the first known high-capacity ternary metal halide ammine, which has been synthesized and its NH3 storage properties using temperature programmed desorption. References 1- T. Vegge et al. Walker, G., Woodhead Publishing Ltd, Cambridge, 2008 2- E.S. Lepinasse et al. Int. J. of Refrigeration 17(1994) 309 3- C. Liu et al. Bull. Chem. Soc. Jpn. 77(2004) 123 4- C.H. Christensen et al. J. Mater. Chem. 15, 4106(2005) 4106 5- D. Chakraborty et al. Fuel Cells Bull. 12 (2009) 6- T. Elm?e et al. Chem. Eng. Sci. 61 (2006) 2618

Authors : Ali Zeaiter, David Chapelle, Philippe Nardin
Affiliations : FEMTO-ST, Department of Applied Mechanics, 24 rue de l’épitaphe 25000 Besançon France

Resume : A macro-scale thermodynamic study [1, 2] was performed in order to describe the hydriding reaction abs/des inside a cylindrical tank. To set off an absorption or desorption reaction, several type of solicitations can be applied to the tank such as: Applied Hydrogen pressure, external temperature, inlet and outlet flux. The predicted output variables attached to the hydride reaction will have a time-space profile and can be cited as follow: local temperature, local reaction rate, local equilibrium pressure, and the local heat generated or needed. Two outputs variables have the most important weight when talking about the efficiency of the hydride reaction, they are: the desorption reaction rate and the output flux. Interactions between a full cell, and a hydrogen cylindrical tank in the stage of desorption are defined by these two output variables, the impact of the non-uniformity according to time of the output flux on the full cell power was identified, in order to establish the optimum working regime of such a system. References: 1] B.A. Talaganis, G.O. Meyer, P.A. Aguirre ‘’ Modeling and simulation of absorption-desorption cyclic processes for hydrogen storage-compression using metal hydrides ‘’ International Journal of hydrogen energy 2011:36:13621-31 [2] A.Zeaiter, D.Chapelle, P. Nardin ‘’searching out the hydrogen absorption/desorption limiting reaction factors, Journal of alloys and compounds (In press)

Authors : Yi Zhang, Xiaoming Wen, Yu Feng, Shujuan Huang, Santosh Shrestha, Tran Smyth, Gavin Conibeer
Affiliations : University of New South Wales

Resume : The concepts of third generation solar cells depend critically on the dynamics of ultrafast carrier relaxation and electron-phonon interactions on very short times scales. The hot carrier solar cell as one of the third generation cells especially depend on the reduction in the energy relaxation rate in an absorber material. Here we investigated the ultrafast carrier dynamics in 1 µm bulk In26.5GaN thin film grown by a new thin-film growth technique called energetic neutral atom-beam lithography/epitaxy (ENABLE) which was done by our collaborators in the Los Alamos national laboratory(LANL), US. The spectroscopies including steady state-photoluminescence (PL), time-resolved PL and transient absorption in the time scale of picoseconds have been measured and analysed. It indicates the relaxation time of our sample is about 22ps through the Maxwell-Boltzmann approximation. This indicates mechanisms, and that variation of Indium content can mediate these. Moreover, the indium fluctuation introduced extrinsic energy state in forbidden energy was observed through tr-PL. Keywords: third generation solar cells, hot carrier solar cell, InGaN, bulk thin film, carrier dynamics, ultrafast spectroscopy, time-resolved photoluminescence, transient absorption.

C.C II.1
Authors : S. Eugénio U.B. Demirci T.M. Silva M.J. Carmezim M.F. Montemor
Affiliations : Centro de Química Estrutural-CQE, Departament of Chemical Engineering, Instituto Superior Técnico, Universidade de Lisboa,1049-001 Lisboa, Portugal. IEM (Institut Europeen des Membranes), UMR 5635 (CNRS-ENSCM-UM), Universite de Montpellier, Place E. Bataillon, F- 34095, Montpellier, France. Department of Mechanical Engineering, GI-MOSM, Instituto Superior de Engenharia de Lisboa, 1950-062 Lisboa, Portugal. ESTSetúbal, Instituto Politécnico de Setúbal, 1959-007 Setúbal, Portugal

Resume : Cobalt has been reported as being an ideal catalyst for hydrolysis of sodium borohydride (NaBH4) as it offers high reactivity, similar to noble metals, while being much less expensive. However, it invariably deactivates by strong adsorption of borates. An alternative is copper, what we have demonstrated for the first time to be highly efficient when doped with small amount of cobalt. A one-step low-cost approach for the fabrication of porous metallic structures is electrodeposition. By taking advantage of the dynamic hydrogen bubble template (DHBT), it is possible to develop 3D hierarchical foam-like architectures consisting of two metals. Further, electrodeposition does not require chemical reducing agents that can hinder the metal catalysts stability. At the E-MRS, we will present our very recent works on the production of highly porous Cu- and Co-based bimetallic foams, CuxCo100-x, by electrodeposition using DHBT. The foams were tailored to enhance specific surface area, improve catalytic activity and increase stability towards deactivation. The foams were evaluated as heterogeneous catalysts in hydrolysis of NaBH4 at 80°C. Among the tested foams, the copper-rich samples, e.g. Cu85Co15, are slightly more active than Co100 and above all they are less sensitive to deactivation by borates adsorption. Thus, porous Cu-rich foams offer an alternative to Co as cheap, active and stable catalysts for hydrogen generation by hydrolysis of NaBH4.

C.C II.2
Authors : Lamprini Boutsika†*, Apostolos Enotiadis†‡, Georgia Charalambopoulou†, Theodore Steriotis†, Ritu Sahore‡, Emmanuel Giannelis‡
Affiliations : †National Center for Scientific Research “Demokritos”, 15310, Ag. Paraskevi Attikis, Athens, Greece; *Department of Chemistry, University of Crete, Voutes, 71003 Heraklion, Greece; ‡Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA

Resume : Mesocellular Carbon Foams have attracted much attention because of their use as catalyst supports, adsorbents and electrode materials. In this work, mesocellular carbon foams were synthesised using different carbon precursor (furfuryl alcohol): silica (MSU-F) ratios, in order to study the effect of the composition on the structure of the final composite materials. MSU-F silica exhibits high surface area, controlled morphology and tunable porosity providing an ideal template for the final carbon foams (designated as C-MSU-Fs). The as-synthesized C-MSU-Fs were characterized systematically using a wide range of methods (Powder X-ray Diffraction, nitrogen adsorption/desorption, IR Spectroscopy, Scanning Electron Microscopy, Thermogravimetric Analysis), and were further assessed as the conducting phase in carbon–sulfur composite cathodes for Li–Sulfur batteries. A carbon–sulfur cathode containing approximately more than 50 wt% of sulfur was prepared by melt infusion of sulfur into the carbon foams. The obtained results showed that the new C-MSU-Fs exhibit promising performance (in terms of discharge capacity and stability over several cycles) as support materials for battery electrodes.

C.C II.3
Authors : Romain MOURY, Mariem MEGGOUH, Robert UBANCZYK, Kateryna PEINECKE, Michael FELDERHOFF
Affiliations : Romain MOURY; Mariem MEGGOUH;Kateryna PEINECKE, Michael FELDERHOFF from Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany Robert UBANCZYK from bInstitut für Energie- und Umwelttechnik, Bliersheimer Strasse 60, 47229 Duisburg, Germany

Resume : For alternative energies together with the increasing of global energy demands new efficient and environmental friendly solutions to store energy are necessary. Hydrogen storage in metal hydrides is one solution proposed and has attracted considerable interests and development of suitable hydrogen storage systems. Two different approaches could be envisaged. The first is to store the chemical potential of hydrogen in metal hydrides to produce electricity. The second approach includes the storage of thermal energy through a chemical reaction combined with the delivering of heat. Among the developed solutions to store heat, the chemical heat storage has the advantage of high energy density in long term storage duration. In our group, we are focusing in the development of Mg-Fe-H system to store thermal energy. In fact, this system presents several advantages: i/ high reaction enthalpy 77.4 kJ/mol H2, ii/ high heat storage density 1.921 kJ/kg (gravimetric) and 2.344 kJ/dm3 (volumetric) iii/ lower dissociation pressure (compared to Mg-H system) which lead to an easier tank design and iv/ low price of the raw materials. The results obtain in our group are presented, first concerning an optimization of the working parameters in order to lower the cost of the process. In a second part the thermal stability and thermodynamics of such system is discussed. In the final part, the development of a tank prototype to store heat using Mg-Fe-H system is described.

C.C II.4
Authors : A. Montone 1, B. Molinas 2, A. Pontarollo 2, M. Scapin 2, H. Peretti 3, M. Melnichuk 3, H. Corso 3, A. Aurora 1, D. Mirabile Gattia 1
Affiliations : 1 ENEA, Technical Unit Materials Technology, Research Centre of Casaccia, Via Anguillarese 301, 00123 Rome, Italy; 2 Venezia Tecnologie S.p.A., 30175 Porto Marghera (Venice), Italy; 3 Comisión Nacional de Energía Atómica, Centro Atómico Bariloche, 8400 Bariloche, Argentina

Resume : LaNi5 base alloy hydrides are among the most widely used and studied materials for solid state hydrogen storage due to their ability to react reversibly with hydrogen at moderate pressures and temperatures. It is also known that the partial substitution of La or Ni by other elements modifies the hydride stability and induces a wide range of plateau pressures, conferring them an excellent versatility. This work investigates a set of MmNi5-xAlx materials (Mm: mischmetal) with different values for the parameter x, in order to determine which composition best satisfies specific working conditions for possible employment in transportation by sea or lagoon where the water of the lagoon is used as a coolant. In the specific case of a public transportation ship (the classical "vaporetto") on the Venice Lagoon, hard restrictions are required for these conditions since hydrogen sorption pressures are a key factor when considering the lagoon average temperature variations between winter and summer seasons. Experimental results of the present study led to a map of Vant’Hoff that let select the best material according to the required conditions.

C.C II.5
Authors : Luis Miguel Sanz-Moral, Miriam Rueda, Ángel Martín
Affiliations : High Pressure Processes Group.- Chemical Engineering and Environmental Technology Department - University of Valladolid (Spain)

Resume : Hydrogen is an ideal energy carrier which is considered for future transport, such as automotive applications. The design of new systems to its storage is crucial in the success of this new technology. Complex hydrides are a good alternative. Lately Ethane 1,2-Diamineborane (EDAB) has been suggested as a good alternative due to its high hydrogen content and the absence of undesired gases during its hydrogen liberation. The decreasing of the hydrides particles and its nanoconfinement are well known technics in order to improve their kinetics. In this work silica aerogels monoliths have been used as a matrix where the EDAB has been impregnated. Silica aerogels were synthesized following the sol gel method using tetramethylorthosilicate as silica precursor and using supercritical CO2 for its drying. The complex was directly solved in the methanol used as reactant. Carbon particles have also been added to the matrix during the alcogel synthesis in order to study the influence of this dopant on the EDAB decomposition kinetic. The addition of this particles have also allow to modify the global dielectric properties of the compound. This phenomena has also been used to heat up the system by using microwave and compare the kinetic of the decomposition using traditional heating. X-Ray Diffraction was used to check the crystallinity of the impregnated EDAB. Thermal gravimetric analysis and differential scanning calorimetry were performed in order to follow the decomposition progress during the heating and the variations depending on the nanoconfinement and the carbon presence. Finally, volumetric gas burette measurements was used to measure the volume of H2 gas release from the EDAB samples by using traditional heating or microwaves.

C.C II.6
Authors : Viera Gärtnerová, Walter Guy, Martin Němec, Aleš Jäger
Affiliations : Department of Advanced Structural Materials Institute of Physics ASCR Na Slovance 2, 18221 Prague 8 Czech Republic

Resume : The use of titanium and its alloys is widening from industrial to hydrogen storage applications because of their well-known hydrogen storage capacity through titanium hydrides. The problem is how to store hydrogen efficiently on board hydrogen fuel-cell vehicles. It was experimentally shown that grain refining, especially to nanoscale, brings significant improvement of the hydrating and dehydrating kinetics of metals and alloys [1]. Bulk grain refinement in titanium and its alloys can be achieved using severe plastic deformation processing [2]. The main effort in microstructural characterisation of titanium hydrides in bulk Ti and Ti alloys was carried out more than 30 year ago. However, the incorporation of advanced imaging techniques for microstructure characterisation of all possible hydride phases, present either in one sample or in duplexalpha/beta pure titanium grade2 (cp-Ti), down to atomic resolution have not yet been shown. Present work shows three types of Ti hydride phases in cp-Ti with unique duplex alpha/beta microstructure shown in [3]. Crystal structures of the hydrides and their morphology were studied using various Transmission Electron Microscopy techniques. Association of hydride precipitation with crystal defects, orientation relationship with Ti matrix and other phases are discussed. [1] A. Zaluska, et al., Appl. Phys. A 72 (2001) 157 [2] A. V. Podolskiy, et al., J. Mater. Sci. 49 (2014) 6803 [3] K. Tesař, et al., Mat Sci Eng A (2014) 155

C.C II.7
Authors : M. Bhihi 1, M. El Khatabi 1, M. Lakhal 1, S. Naji 1, 2, H. Labrim 3, A. Benyoussef1, 4, 5, A. El Kenz 1, M. Loulidi 1
Affiliations : 1 LMPHE, (URAC), Faculté des Sciences, Université Mohammed V-Agdal, Rabat, Morocco 2 Department of Physics, Faculty of Science, Ibb University, Ibb, Yemen 3 Centre National de l'Energie, des Sciences et des Techniques Nucléaires, Rabat, Morocco 4 Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat, Morocco 5 Hassan II Academy of Science and Technology, Rabat, Morocco

Resume : Ab-initio calculations are carried out to analyze the improvement of hydrogen storage properties, in Mg-based hydrides, through a double substitution (Mg14TMAlH32 and Mg14TMLiH32 TM = Ti, Sc, Zn). The calculations are performed using the all-electron full-potential local-orbital minimum-basis scheme (FPLO9.00-34). Our results indicate a decrease of the heat of formation and desorption temperature, while preserving the gravimetric storage capacity around 7.6wt%, these outcomes are probably due to the second substitution, Al or Li, which are characterized by their light weights. Discussions of the charge exchange and the density of states are done, to offer more possible explanations of our results.

C.C II.8
Authors : M. Bhihi1, M. Lakhal1, S. Naji1,2, H. Labrim3, A. Belhaj4, A. Benyoussef1,5,6, A. El Kenz1, M. Loulidi1, B. Khalil1, O. Mounkachi5, M. Abdellaoui1, K. Hlil7
Affiliations : 1 LMPHE, (URAC), Faculté des Sciences, Université Mohammed V-Agdal, Rabat, Morocco 2 Department of Physics, Faculty of Science, Ibb University, Ibb, Yemen 3 Centre National de l'Energie, des Sciences et des Techniques Nucléaires, Rabat, Morocco. 4 Faculté Polydisciplinaire, Université Sultan Moulay Slimane, Béni Mellal, Morocco 5 Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat, Morocco 6 Hassan II Academy of Science and Technology, Rabat, Morocco 7Institut Néel, CNRS-UJF, 38042 Grenoble cedex 9, France

Resume : Using the ab initio calculations, we predict the improvement of the desorption temperature and the hydrogen storage properties of doped Mg-based hydrides such as (,Mg15AMH32 AM = Ca, Sr and Ba as a super cell 2x2x2 of MgH2 ). In particular, the electronic structure has been performed numerically using the all-electron full-potential local-orbital minimum-basis scheme FPLO9.00-34. Then, we discuss the formation energy calculations in terms of the material stabilities and the hydrogen storage thermodynamic properties improvements. Among others, we find that the stability and the desorption temperature decrease without reducing significantly the high storage capacity of hydrogen. Moreover, it has been observed that such a doping procedure does not affect the electronic behavior appearing in MgH2 including the insulator state in contrast with the transition metal hydrides modifying the electronic of pure MgH2.

C.C II.9
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 : A. J. Panas1, B. Fikus1, P. Płatek1, I. Kunce2, S. Dyjak2, M. Michalska-Domanska2, K. Witek2, P. Kuziora2, A. Olejarczyk2, L. Jaroszewicz2, M. Polanski2
Affiliations : 1Faculty of Mechatronics and Aeronautics, Military University of Technology 2Faculty of Advanced Technology and Chemistry, Military University of Technology

Resume : Understanding thermal properties of metal hydride beds is critical for accurate analysis of the heat and mass transfer phenomena in hydrogen storage applications. However, this poses a challenge for routine measuring methods due to the complex interrelation of different transport mechanisms in a metal hydride bed and the fact that the effective thermal diffusivity depends on the hydrogen concentration, hydrogen pressure and the temperature of the system. Determining the effective thermophysical properties of hydrides requires a new, reliable and easy to implement approach. In this paper we present the apparatus and methodology for investigating the thermal diffusivity of metal hydride beds when exposed to a range of temperatures and pressures. For this purpose a pressurised-cell test stand has been designed and assembled. The pressure cell design accounts both for the thermophysical property measurements and for studies of the heat transfer accompanying hydrogen absorption and desorption. The effective thermal diffusivity is measured using a modified Ångström method. The system and the developed methodology have been tested by measuring the effective thermal conductivity of the powdered LaNi5 bed. In this work we present obtained results and compare them against results from similar investigations performed in open cell apparatus under atmospheric gas conditions. The results of conducted tests demonstrate both the accuracy and the effectiveness of the developed procedure.

C.C II.11
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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Session 9 : Michael Hirscher
Authors : Maximilian Fichtner, Zhirong Zhao-Karger
Affiliations : Helmholtz-Institute Ulm (HIU), Karlsruhe Institute of Technology

Resume : Magnesium has been an attractive element for various energy storage applications, mostly due to its light weight, low toxicity, low cost and good handling and safety properties. It is also the 8th most abundant element in the earth crust and the long term supply risk is low. The paper will review the application of magnesium in H storage and in battery applications, starting with the binary MgH2 and how it was enabled as H storage material since the 1980´s. In early studies, it was shown that the H exchange kinetics can be improved by finely dispersing the hydride and mixing it with catalytic additives – a concept, which was also transferred to other solid H storage materials based on binary hydrides, complex hydrides, and solid state reaction systems. The application of Mg as an anode material in Mg batteries has been investigated since the 1980s. Also here, Mg is principally attractive for the abovementioned reasons. Moreover, it offers very high theoretical volumetric energy densities for batteries and it does not form dangerous dendrites upon plating, an effect which currently prevents the use of metallic Li anodes in battery cells with liquid electrolytes. Recently, new concepts have been developed to produce electrolytes with a mild chemistry that allow the combination of Mg anode with a sulfur cathode, an electrochemical couple which is particularly attractive due to its sustainable composition, low toxicity, low cost, and a high theoretical energy density of 3200 Wh/L

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 : Daniel Reed, David Book,
Affiliations : School of Metallurgy and Materials, University of Birmingham, Birmingham, B15 2TT, UK

Resume : With relatively high gravimetric and volumetric hydrogen storage capacities, borohydrides have attracted interest as potential hydrogen storage media. Lithium borohydride has a maximum theoretical gravimetric hydrogen storage density of 18.4 wt%, and has been shown to be reversible when heated to 600°C in 350 bar hydrogen[1]. The addition of nickel and iron lithium borohydride has previously been shown to improve the dehydrogenation properties [2-6]. With the formation of metal borides upon decomposition had been shown to be advantageous to the reversibility of Lithium and calcium borohydride systems, due to the weaker B-B bonding within MgB2, YB4 and CaB6 compared to B12 cages with in amorphous boron [3, 7-9]. In this work the dehydrogenation and rehydrogenation properties and mechanisms will be studied when nanoparticles (Ni, Fe and NiFe) are added to alkali and alkali earth borohydrides. The in situ dehydrating and rehydrating mechanisms is studied by a combination of variable temperature and pressure XRD and Raman spectroscopy, supplemented by thermal gravimetric analysis with mass spectroscopy (TGA-MS) and differential scanning calorimetry (DSC). References [1] Orimo, S., Nakamori, Y., Kitahara, G., Miwa, K., Ohba, N., Towata, S., and Züttel, A. J. Alloy. Compd., 2005. 404: p. 427-430. [2] Hong, S.-H. and Song, M.Y. 2013. 48(9): p. 3453-3458. [3] Li, H.-W., Yan, Y., Akiba, E., and Orimo, S.-i. 2014. 55(8): p. 1134-1137. [4] Song, M.Y., Kwak, Y.J., Shin, H.-S., Lee, S.H., and Kim, B.-G. 2013. 38(4): p. 1910-1917. [5] Song, M.Y., Kwon, S.N., Kwak, Y.J., Park, H.R., and Kim, B.-G. 2013. 51(8): p. 615-619. [6] Xu, J., Li, Y., Cao, J., Meng, R., Wang, W., and Chen, Z. 2015. 5(3): p. 1821-1828. [7] Vajo, J.J., Skeith, S.L., and Mertens, F. J. Phys. Chem. B, 2005. 109(9): p. 3719-3722. [8] Kim, Y., Reed, D., Lee, Y.S., Lee, J.Y., Shim, J.H., Book, D., and Cho, Y.W. J. Phys. Chem. C, 2009. 113(14): p. 5865-5871. [9] Shim, J.-H., Lim, J.-H., Rather, S.-u., Lee, Y.-S., Reed, D., Kim, Y., Book, D., and Cho, Y.W. J. Phys Chem Letts, 2009. 1(1): p. 59-63.

Authors : A. J. Panas1, B. Fikus1, P. Płatek1, I. Kunce2, S. Dyjak2, M. Michalska-Domanska2, K. Witek2, P. Kuziora2, A. Olejarczyk2, L. Jaroszewicz2, M. Polanski2
Affiliations : 1Faculty of Mechatronics and Aeronautics, Military University of Technology, Poland 2Faculty of Advanced Technology and Chemistry, Military University of Technology, Poland

Resume : Hydrogen storage in solid state remains unsolved problem. Despite the fact that many different types of alloys and chemical compounds are still being investigated no real solution was found till now. Almost all of materials considered for solid state hydrogen storage generates large amounts of heat during hydrogenation in the same time being powders of very low heat conductivity - close to insulators. While in laboratory scale with samples mass usually much below 1 g this is not a problem, in real life, if one considers powering car with metal hydride, the heat exchange becomes a real challenge. During the loading process tens millions of joules of energy need to be removed from the hydrogen tank. With such low conductivity of hydride powder, for vessels being able to store several kilograms of hydrogen, this process lasts usually several hours. By that reason very effective method for improving heat exchange in the vessel is required. In this work we present innovative, different from usually used method for improving heat exchange in large scale hydrogen storage vessels.

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.

15:30 Coffee Break    
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.

Authors : Laura Bravo Diaz1,*, James M. Hanlon 2, Marek Bielewski1, Aleksandra Milewska3, Cèdric Dupuis4 and Duncan H. Gregory 2
Affiliations : 1. European Commission, Joint Research Centre (JRC), Institute for Energy and Transport, Westerduinweg 3, 1755 LE Petten, Netherlands. 2. School of Chemistry, University of Glasgow, Glasgow, G12 8QQ. 3. Institute of Power Engineering, Department of Thermal Processes, 02-981 Warsaw, Poland. 4. McPhy Energy, 26190 La Motte-Fanjas, France.

Resume : HYPER is an EU FCH JU project focused on the development of a flexible, integrated fuel cell and its H2 storage system for portable power applications. One novel aspect of HYPER is the development of a promising solid-state store based on nanostructured materials that comply with the requirements of the modular PEM FC. Two potential solutions were investigated in collaboration between the SolTeF laboratory of DG JRC, European Commission and the School of Chemistry, University of Glasgow. One of the envisaged solutions is the development of exothermic ‘one shot’ H2 release systems combined with an endothermic high capacity hydride matrix. The heat of the reaction of the exothermic filler material would initiate and propagate a reaction in the matrix hydride and additionally contribute to the H2 yield. Another solution we investigated is to confine a material with low molecular weight and high gravimetric hydrogen capacity within an inert porous matrix. The role of the inert matrix would be to improve the hydrogen release mechanism. Nanoconfinement is an efficient way of improving hydrogen desorption properties and can reduce dehydrogenation temperatures. In addition, suppression of unwanted release of by-products can be achieved. Two different synthesis methods for confining the H2 storage material will be presented. Comparison of both methods and the effect of the inert matrix will be discussed, as will the most promising approaches for further optimisation.

Authors : S. Eugénio, D.M.F. Santos, B. Šljukić, M.F. Montemor
Affiliations : CQE, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; CQE, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal

Resume : Direct borohydride/peroxide fuel cells (DBPFCs), using sodium borohydride (NaBH4) as the fuel and hydrogen peroxide (H2O2) as the oxidant, are seen as promising power sources for space, underwater, and specific terrestrial applications where O2 is not available. To push DBPFCs forward, it is necessary to develop efficient low-cost electrocatalytic materials towards hydrogen peroxide reduction reaction (HPRR) that can avoid the use of noble metal catalysts. Transition metal alloys are relatively cheap materials that have been recently reported to show good activity for HPRR. Herein, Cu-M (M=Ni,Co,Fe) foams are produced via electrodeposition using hydrogen bubble evolution as a dynamic template. This single-step process leads to the formation of nanostructured dendritic foams with high surface area. The foams are analysed by SEM/EDS to assess their morphology and chemical composition. The electrochemical performance of the 3D Cu-M foam electrodes is evaluated by cyclic voltammetry, linear scan voltammetry, chronoamperometry, and chronopotentiometry in alkaline medium. Results demonstrate that Cu-M foam electrodes possess high catalytic activity and excellent stability for HPRR. This owes from their large electrochemical surface area – a consequence of their unique open and porous architecture - that provides a fast pathway for electron transport and mass transfer. These features make these 3D Cu-M foams promising candidates as cathodes for DBPFCs and other H2O2-based fuel cells.

18:00 Best Student Presentation Awards Ceremony & Reception - Main Hall    

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 PASQUINIDepartment of Physics and Astronomy, University of Bologna

Viale C. Berti-Pichat 6/2 I-40127 Bologna Italy

+39 051 2095149
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