Symposium FB
Hydrogen Production and Storage

Session FB-1 - Hydrogen Production

FB-1:IL01  Solar Fuels from H2O and CO2 via Thermochemical Redox Cycles
M.E. GALVEZ, P. FURLER, D. MARXER, J. SCHEFFE, M. GORBAR, U. VOGT, A. STEINFELD, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland; Laboratory for Hydrogen & Energy, Empa, Dübendorf, Switzerland; Solar Technology Laboratory, Paul Scherrer Institute, Villigen PSI, Switzerland

Solar thermochemical cycles for the production of synthetic fuels make use of concentrated solar radiation as the source of high-temperature process heat. These processes inherently operate at high temperatures and utilize the entire solar spectrum, and as such provide thermodynamic favorable paths to efficient and clean fuel production. Considered is the ceria-based redox cycle for splitting H2O and CO2.
A 3kW solar cavity-receiver containing a reticulated porous ceramic (RPC) foam made of CeO2 has been experimentally investigated [1-3]. The RPC was directly exposed to mean solar flux concentrations exceeding 3000 suns. The solar-to-fuel energy conversion efficiency, defined as the ratio of the calorific value of the fuel produced to the solar radiative energy input, was 1.73% average and 3.53% peak [2]. These are the highest solar-to-fuel energy conversion efficiency values reported to date for a solar-driven device converting CO2 to CO. The simultaneous splitting of H2O and CO2 in consecutive ceria redox cycles yielded high-quality syngas suitable for the catalytic conversion to liquid hydrocarbons [3].
References:
1. Science 330, pp. 1797-1801, 2010.
2. Energy & Fuels 26, pp. 7051-7059, 2012.
3. Energy & Environmental Science 5, pp. 6098-6103, 2012.


FB-1:IL02  Solar Thermochemical Water Splitting: Advances in Materials and Methods
A.H. McDANIEL, M.D. ALLENDORF, Sandia National Labs, Livermore, CA, USA; I. ERMANOSKI, A. AMBROSINI, E.N. COKER, J.E. MILLER, Sandia National Labs, Albuquerque, NM, USA; W.C. CHUEH, Stanford University, Palo Alto, CA, USA; R. O'HAYRE, J. TONG, Colorado School of Mines, CO, USA

It is estimated that population growth and continued industrialization of developing countries will double global energy consumption by 2035. And in so doing, increase the anthropogenic carbon content in the atmosphere furthering the deleterious effects of climate change. Developing technologies that covert solar energy into simple chemical fuels is therefore a societal imperative. This talk will describe efforts to directly convert highly-concentrated thermal energy from the sun into hydrogen fuel via a two-step thermochemical water-splitting reaction. We focus on the use of perovskite oxides and our efforts to derive key relationships between composition and functionality. In addition, there is no clear answer to which of the many materials proposed for this chemistry will ultimately lead to the highest overall process efficiency. Therefore, design principles for achieving optimal solar-to-fuel conversion efficiency will be reviewed and create a framework for discussing the desired material properties within the context of an advanced particle-bed receiver reactor.
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.


FB-1:IL03  Hydrogen Production via Thermochemical Water-splitting by Alkali Metal Cycle
H. MIYAOKA¹, T. ICHIKAWA², Y. KOJIMA², ¹Institute for Sustainable Sciences and Development, Hiroshima University, Higashi-Hiroshima, Japan; ²Institute for Advanced Materials Research, Hiroshima University, Higashi-Hiroshima, Japan

Thermochemical water-splitting is attractive as an energy conversion technique from renewable energy to hydrogen. We focus on the alkali metal cycles composed of four processes, which are the H2 generation (1)2MOH+2M→2M2O+H2, the metal separation (2)2M2O→M2O2+2M, the hydrolysis (3)M2O2+H2O→2MOH+1/2O2, and the phase transition of alkali metal (4)2M(g)→2M(l), as hydrogen production technique via thermochemical water-splitting operated at lower temperature than conventional methods. If the temperature is reduced down to 600 °C, the choice of heat sources are expanded and heat storage materials can be used for long time operation. In this work, the feasible reaction conditions of the cycles are systematically investigated, where nonequilibrium techniques are utilized to reduce the reaction temperature for thermodynamically difficult process. The operating temperature of the Li cycle is 800 °C due to large endothermic of the metal separation reaction (2). The Na cycle is possibly operated below 400 °C. The K cycle is difficult to be operated due to the strong corrosion for the reactor. Therefore, the Na cycle is recognized as a promising hydrogen production technique utilized at lower temperature than 600 °C.


FB-1:IL04  Solar Fuels from Thermochemical Gas Splitting
B. MEREDIG, A. EMERY, H. HANSEN, C. WOLVERTON, Northwestern University, Evanston, IL, USA

Metal oxide materials may be used in two-step solar thermochemical water-splitting cycles to renewably produce hydrogen. Here, we use first-principles density functional calculations to investigate promising oxide materials for use in these cycles. We present a general analysis of the equilibrium thermodynamics of a two-step metal oxide water splitting cycle, and survey a large number (more than 100) binary oxide redox couples. This analysis strongly suggest the use of non-stoichiometric oxides in gas splitting cycles. Hence, we perform a kinetic and thermodynamic analysis of the mechanism for water splitting on reduced CeO2-x (111). We show the unreactive behaviour at low temperature is caused by kinetically limited diffusion of vacancies from the subsurface to the surface, while the remarkable reduction of reduced CeO2-x(111) at high temperature, where only H2 desorption is slow, may be explained by the formation of a thermodynamically stable hydroxyl layer.


FB-1:IL06  Hydrogen Generation by Electrolysis of Liquid Ammonia
N. HANADA, Graduate School of Systems and Information Engineering, University of Tsukuba, Tsukuba, Ibaraki, Japan

Ammonia (NH₃) has a high volumetric hydrogen density of 107.3 kg H₂ m⁻³ and a high gravimetric hydrogen density of 17.8 mass% compared with the solid state hydrogen storage materials. NH₃ is one of the most promising methods for storing and transporting hydrogen. We have performed the direct electrolysis of liquid ammonia for hydrogen generation. This method would be able to decompose ammonia itself by keeping high hydrogen density at room temperature. The reaction of liquid ammonia electrolysis occurs with amide ion (NH₂−), and theoretically produce hydrogen at 0.077 V. However, the experimental electrolysis voltage of more than 1 V by using Pt plate electrode is too high for practical use [1].
To investigate the over potential properties, cyclicvoltammetry measurement by using a reference electrode of a Pt wire as a pseudo electrode is performed. For anode reaction of N₂ desorption, the potential at current density of 1 mA/cm² is 1.05V (vs Pt). On the other hand, for cathode reaction, that of H₂ desorption is 0.22 V (vs Pt). It indicates that the anode over potential is five times of the cathode one. Therefore, the anode reaction of nitrogen desorption is rate-determining step of over ammonia electrolysis.
To decrease over potential of anode reaction, effects of 3d transition metal electrode of Fe, Co and Ni plate on ammonia electrolysis are investigated. As a result, Ni plate is the best electrode among 3d transition metals and decreases the potential at 1mA/cm² current density of anode reaction to 0.75 V(vs. Pt).
As a different approach to decrease electrolysis voltage, an electrode of Pt black electrodeposited on Pt plate to increase surface area is adapted for anode and cathode electrode of ammonia electrolysis. The electrolysis voltage at 1 mA/cm² decreases to 0.44 V from 1.0 V of Pt plate electrode. The hydrogen generation at 0.5 V is observed by gas chromatography after the electrolysis for 10 hours.
[1] N. Hanada, S. Hino, T. Ichikawa, H. Suzuki, K. Takai and Y. Kojima, Chem. Commun., 2010, 46, 7775-7777


FB-1:L07  Ceria Based Materials with Enhanced OSC Properties for H2 Production by Water Splitting Reaction
A. PAPPACENA, M. BOARO, L. BARDINI, A. TROVARELLI, Università degli Studi di Udine, Udine, Italy

Cerium based oxides have recently emerged as highly attractive choice for two-steps thermochemical water splitting cycles for H2 production because of their ability to reversibly store and release lattice oxygen in inert conditions between 1573-1773 K. A novel surfactant-assisted method was developed in our laboratory to enhance OSC (oxygen storage capacity) properties and thermo stability of Ce0.15Zr0.79Nd0.04La0.02O2-δ composition. The developed procedure was used to prepare other compositions with differents amount of CeO2, pure and doped with La and Nd. All prepared compositions were subjected to different aging treatments at different temperature under air and N2 atmosphere. The textural, structural and OSC properties were studied and the reactivity versus water splitting at 1073K was tested. The results obtained highlight that the reactivity depends on the temperature of treatments and on the composition. The best result was obtained for Ce0.5Zr0.5O2 composition treated at 1673K in N2 (308 µmol H2/g of CeO2). Further studies are in progress to investigate the correlation between the structure and the reactivity of these oxides.


FB-1:IL08  Efficient Solar Water Splitting with a BiVO4-Based Heterojunction Photoanode
R. VAN DE KROL, F.F. ABDI, Helmholtz-Zentrum Berlin für Materialien und Energie Gmbh, Institute for Solar Fuels, Berlin, Germany

Multinary metal oxides are promising candidates for the conversion of solar energy to chemical fuels. They combine reasonable semiconducting properties with excellent chemical stability and low cost. Bismuth vanadate (BiVO4) is a promising member of this class. It has a bandgap of 2.4 eV, and can be prepared by a low-cost, simple spray pyrolysis technique. Photoelectrochemical measurements were used to identify its performance-limiting processes. The slow surface reaction kinetics can be enhanced by applying a cobalt phosphate water oxidation co-catalyst, while the poor conductivity of the material can be improved by doping with tungsten. Moreover, the charge carrier separation efficiency can be improved by introducing a gradient in the dopant concentration, effectively creating a distributed n+-n homojunction. These improvements have resulted in AM1.5 photocurrents of 3.6 mA/cm2 at 1.23 V vs RHE, which is the highest photocurrent ever reported for a metal oxide photoanode. Combination with an amorphous silicon tandem cell resulted in a stand-alone water splitting device with a solar-to-hydrogen (STH) efficiency of 4.9% [1].
[1] F.F. Abdi et al., Nat. Commun. 4, 2195 (2013)


FB-1:IL09  The Productivity of Photobiological Water Splitting: Trading Time for Efficiency
H.J.M. DE GROOT, Leiden Institute of Chemistry, Leiden University, The Netherlands

In this invited contribution it will be explained how photosynthesis is engineered with a nanostructured chemical conversion chain, where reaction time is traded for better efficiency by eliminating kinetic losses through integration of conversion and storage. To achieve this, three hurdles need to be overcome, 1) charge separation occurs efficiently upon irradiation with visible light, regulated by tunneling barriers and facilitated by lowering of transition states through vibrational coherence of semi-synthetic dye molecules in a responsive matrix; 2) water oxidation occurs efficiently using a molecular water oxidation catalyst with proton and electron management in the second shell for efficient operation at relevant time scales for four-electron water oxidation catalysis; and 3) the energy levels of the charge separation device and the water oxidation complex are properly matched for photocatalysis by shaping of semi-synthetic molecules. In photosynthesis this is achieved with a remarkably limited set of components: dye molecules are mainly chlorophylls, there are only two types of reaction centers, with very similar protein scaffolding, and water is oxidized from a catalytic cluster that is highly conserved in evolution and consists of four Mn, bridged by oxygen.


FB-1:L10  TiSx Nanoribbons: Hydrogen Storage and Photoelectrochemical Properties
M. BARAWI MORAN¹, M. PONTHIEU², J.R. ARES¹, F. CUEVAS², I.J. FERRER¹, J.F. FERNÁNDEZ¹, C. SÁNCHEZ¹, ¹Grupo MIRE, Dpto. Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain; ²Equipe de Chimie Métallurgique des Terres Rares (CMTR) Institut de Chimie et des Matériaux, Paris Est (ICMPE) CNRS-UMR 7182, Thiais Cedex, France

Nowadays, finding cheap and non-toxic materials able to generate and store hydrogen in a clean way is a challenge in renewable energy field. Many compounds are investigated for this purpose. Metal sulfides seem to be very attractive, and specifically, TiSx shows adequate transport, optical* and photoelectrochemical properties** as well as particular morphology (2D nano-layers) to generate and store hydrogen.
TiSx nanoribbons were synthesized by sulfur reaction with titanium discs and powder at temperatures between 450-550 °C. Obtained materials were characterized by SEM-FEG and XRD. Photoelectrochemical measurements were made with a 3-electrode quartz cell using TiSx samples as photo-anodes. Hydrogen evolution of μmolsH2/min flow was produced. To investigate H-storage properties, thermodynamic and kinetic measurements have been performed at isothermal conditions. Possibilities to use TiSx like hydrogen generation and storage will be discussed.
*I.J.Ferrer, J.R.Ares, J.M.Clamagirand, M.Barawi, C.Sánchez. Thin Solid films(2013)535, 398-401.
**I.J.Ferrer,M.D.Maciá,V.Carcelén,J.R.Ares,C.Sánchez,Energy procedia (2012) 22,48-52.


Session FB-2 - Hydrogen Storage

FB-2.1  Metal Hydrides

FB-2.1:IL01  Transition from Metal Hydrides to Complex Hydrides
SHIN-ICHI ORIMO, WPI Advanced Institute for Materials Research (WPI-AIMR) / Institute for Materials Research (IMR), Tohoku University, Sendai, Japan

We are focusing on transition between bonding states of hydrogen in hydrides, as a phenomenon specific to hydrides.
An example was found in YMn2 hydrides, that is, the hydrides showed the continuous transition from the metal hydride YMn2Hx to the complex hydride YMn2H6 with [MnH6]5- complex anion, even under rather mild conditions (5 MPa, 423 K). Some computational and experimental studies including EXAFS have been carried out in order to extend the novel property to the other systems. The transition between the bonding states of hydrogen provides us a new guideline on the energy-related (especially, hydrogen storage) functions of the hydrides; "increasing hydrogen densities of metal hydrides by using continuous transition into complex hydrides".
It was also demonstrated that the addition of Li (or LiH) enabled the formation of the novel complex hydride YLiFeH6 with the [FeH6]4− complex anion from YFe2 which has not been considered to transform into a complex hydride on its own. The method can be applied to many other intermetallic compounds even if they are composed of only elements that do not form intermetallic compounds or solid solution alloys with Li, which will greatly contribute to the increase in the variety of hydrides.


FB-2.1:L04  Hydrogen Storage of Nanocrystalline Mg-Ni alloy Processed by Equal-channel Angular Pressing and Cold Rolling
A. REVESZ, Dept. Mater. Physics, Eötvös University, Budapest, Hungary

Ball-milled (BM) nanocrystalline Mg2Ni powders were subjected to intense plastic straining by cold rolling (CR) and equal-channel angular pressing (ECAP). Convolutional whole profile fitting analysis of X-ray diffractograms has shown that ECAP deformation of the BM powders results in a moderate crystallite size reduction (D=13), while the distribution of the coherently scattering domains preserves its homogeneity. On the contrary, the CR specimens undergoes different evolution, i.e. considerable broadening of the crystallite-size distribution is realized after 4 CR passes accompanied with a rapid crystallite size increase up to D=37 nm. Scanning electron microscope experiments of the ECAP samples confirmed considerable compaction, while the original powder particles still can be observed after CR. Hydrogen absorption measurements revealed that both ECAP and CR reduces the storage capacity of the HEBM Mg2Ni powders, however, the broader crystallite size distribution of the CR 4x sample is coupled with an enhanced kinetics. In addition, it was shown that the amount of equivalent strain of the different techniques, the deformation geometry, and the resulting nanostructure and microstructure are together responsible for the H-storage behavior of nanocrystalline Mg2Ni alloys.


FB-2.1:L05  Size Reduction in Mg and Mg rich Intermetallics for Hydrogen Storage
A. AYDINLI¹, B. AKTEKIN¹, S. TAN², G. ÇAKMAK³, T. ÖZTÜRK¹, ¹Middle East Technical University, Ankara; ²Akdeniz University, Antalya; ³Bulent Ecevit University, Zonguldak, Turkey

With a view to develop efficient hydrogen storage materials, we investigated size reduction in Mg and Mg rich intermetallics through several means. First, size reduction in Mg was investigated by milling. In addition to the conventional milling, powders were also milled with MgH2 addition or by predeforming the powders by ECAP. These enable the production of particulates of 10 μm in size. An alternative mean in obtaining a size reduction is to synthesize hydrogen storage alloys directly from their oxides. In this process, oxides mixed and sintered at the required stoichiometry are deoxidized in a molten salt yielding a porous residue where the particles are of 1-3 μm. Hydrogen decrepitation is another processing technique where it is possible to obtain submicron particles. Two intermetallics were selected for the current study; Mg2Ni and Mg2Cu. The study showed that Mg2Ni with three or more cycles was refined drastically reaching sub-micron sizes. In the case of Mg2Cu, however, the behavior was different. Here a greater portion of particles remained with almost the same size as the starting powder. It is concluded that Mg2Ni is suitable for decrepitation processing so that they can be refined to submicron sizes. Reasons why Mg2Cu is resistant to pulverization are discussed.


FB-2.1:IL06  Investigating the Reaction Pathways when Cycling Multicomponent Metal Hydride Systems
G.S. WALKER, Energy and Sustainability Research Division, University of Nottingham, Nottingham, UK

Although light metal binary hydrides like MgH2 and LiH have high hydrogen storage capacities, these materials have too high an enthalpy of dehydrogenation, resulting in temperatures in excess of 300°C being required to dehydrogenate these materials. However, it is known that the thermodynamics controlling the temperature of dehydrogenation can be tuned for a hydride-based system by adding a destabilisation agent which reduces the enthalpy of dehydrogenation through the formation of a new alloy species. Incorporating group 14 elements such as Si and Ge has a dramatic effect on reducing the temperature of dehydrogenation. In situ neutron diffraction has been used to elucidate the reaction pathway and these systems have been characterised to determine the thermodynamics, kinetics and the effect of stoichiometry.


FB-2.1:IL07  Hydrogen Storage Properties of Mg-based Materials
E. AKIBA, J. MATSUDA, International Institute for Carbon-Neutral Energy Research, Fukuoka, Japan

The Mg-hydrogen system has a potential to store hydrogen up to 7.6 mass % but its realistic application seems to be an issue because hydrogenation/dehydrogenation temperature is around 623 K and reaction rate without catalyst is slow. We have been exploring Mg-based materials to develop those can desorb hydrogen at ambient temperature and pressure.
We found Mg-based Laves phase alloys such as (Mg, M)Ni2 (M=Ca and rare earth) with C15 structure absorb and desorb hydrogen around room temperature but the capacity does not reach to H/M=1.0. We have investigated the hydrogen occupation sites of this system and compared other Laves phase hydrides consisted of transition metals.
Mg-based meta-stable phases such as Mg-Ti and Mg-Co systems have been synthesized using the ball milling method. These phases absorb hydrogen but the hydrides synthesized from both Mg-Ti and Mg-Co alloys are stable for applications. Crystal structures and local structures of Mg-Co hydride phases were investigated in detail using X-ray and neutron PDF analysis.
Mg-based thin films with the Pd cover layer show extremely fast kinetics of hydrogenation and dehydrogenation at room temperature and moderate hydrogen pressure. The morphology of the layers has been observed using in-situ High Resolution (HR) TEM. We successfully observed crystallization of Mg2NiH4 in atomic scale under hydrogen pressure.
The potential of Mg-based materials for hydrogen storage application will be discussed.


FB-2.1:L08  Electrochemical and Solid/Gas Investigation of Nb4MSi (M=Co, Ni) Hydrides
J. ANGSTROM, M. SAHLBERG, Dept. of Chemistry, Angström Laboratory, Uppsala Universitet, Uppsala, Sweden

Nb4MSi (M= transition metal) is a group of intermetallic hydrogen storage materials which have not been very well investigated, except for the structure of the deuterides of Nb4CoSi and Nb4NiSi. The materials were synthesised using high temperature techniques, arc melting and heat treatment, and characterised using powder X-ray diffraction. Phase analysis of the resulting samples was performed by refinement using the Rietveld method.
The hydrogen storage properties were evaluated using Pressure Composition Isotherms (PCI) of the materials and chronopotentiometric cycling of electrodes prepared from the materials. Both techniques reveal a very low equilibrium pressure, for both Nb4CoSi and Nb4NiSi. This is expressed in the fact that once the material is hydrogenated only hydrogen from the β-phase could be desorbed electrochemically from the Nb4CoSi sample (and none at all from the Nb4NiSi sample). The PCI also reveal slow kinetics for both Nb4MSi samples. To address both the kinetic and thermodynamic shortcomings of the material a number of partial or full substitutions of the constituent elements was tried.


FB-2.1:L09  The Preparation of Carbon-confined Mg Nanoparticles from Vapor
S. SUWARNO, P.E. DE JONGH, Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands

Magnesium hydride is a promising material for energy storage applications such as for solid-state hydrogen storage or batteries. However, practical use has been hindered because of kinetics, thermodynamic, and cycle life limitations. Nanosizing is an effort to tackle some of the problems. Nanosizing enlarges specific surface areas and reduces hydrogen diffusion distances, and thus improves the kinetics. However, magnesium nanoparticles sinter during hydrogen absorption-desorption cycling. This can be prevented by confining nanoparticles on porous matrices[1]. In this respect, a simple method to prepare carbon-confined Mg nanoparticles was developed[2].
In the present work, a new development on the preparation of carbon-confined MgH2 will be presented. The carbon-confined nanoparticles have been prepared by vapor-solid growth taking advantage of the high vapor pressure of Mg. The method consists of heating a mixture of porous carbon and MgH2 (or Mg) to mild temperatures, e.g. 616 °C, below the melting point of magnesium. The temperature programmed desorption profiles show that hydrogen desorption peaks of the carbon-confined MgH2 occur at 275-285°C depending on the pore size of the supports, yet these peak temperatures are lower than that of bulk MgH2. Remarkable is that the hydrogen desorption from the nano-phase and the bulk-phase hydrides are clearly distinct, with up to 70% of the deposited MgH2 confined within the pores. The nanoparticles yield depends on the pore size of the support, which underlines the role of porosity for the nucleation of Mg. Understanding the mechanism of vapor-solid nucleation and growth is vital to obtain high Mg nanoparticle loading on porous matrices.
References
1. de Jongh PE., Adelhelm P, Chem. Sus. Chem. 3 (2010) 1332-1348
2. de Jongh PE, et al., Chem. Mater.19 ( 2007) 6052-6057


FB-2.1:L10  Cyclability of Compacted MgH2 Composites under Hydrogen Pressure
D. MIRABILE GATTIA, A. MONTONE, ENEA, Materials Technology Unit, Casaccia Research Centre, Rome, Italy; G. GIZER, Hacettepe University, Nanotechnology and Nanomedicine Department, Beytepe Ankara, Turkey

Hydrogen storage represents a bottleneck in the diffusion of hydrogen driven technologies. Technological problems are related to the use of compressed and liquid hydrogen while safer and cheaper methods for storing hydrogen are required. Magnesium hydride (MgH2) is an attractive material for hydrogen storage (7.6 wt% H2 capacity).
Nanostructuring and catalyst dispersion through high-energy ball milling has emerged as a relatively simple and scalable technique to produce Mg-based materials with faster hydrogen sorption kinetics respect to pristine material. Nb2O5 revealed to be one of the most efficient catalyst to improve MgH2 kinetics of reaction with hydrogen. The use of compacted materials instead of powders enhances the heat management inside a tank. In order to better investigate the application of these compounds inside tanks for hydrogen storage, the powders prepared by ball milling MgH2 with 5wt% of Nb2O5 have been compacted at different pressures in presence of carbon-based materials. Carbon nanostructured materials have been used as agents for compaction and for their higher thermal conductivity respect to MgH2. The mechanical stability of these compacted systems during repeated cycling under hydrogen pressure is discussed together with the modifications of the microstructure. Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and volumetric Sievert's type apparatus have been used for characterizing the samples.


FB-2.1:L11  Hydrogenation Properties of Zirconium-doped TiFe and TiFe0.9Mn0.1 Alloys
J. HUOT, C. GOSSELIN, P. JAIN, Universite du Quebec a Trois-Rivieres, Canada; J. ECKSTEIN, Helmut Schmidt University, Germany

The goal of this investigation is to improve the first hydrogenation (the so-called activation) of TiFe alloy. This alloy has a relatively low hydrogen storage capacity (1.86 wt.%) but its low cost and capacity to reversibly store hydrogen at room temperature makes it an attractive material for some applications. However the biggest disadvantage of TiFe alloy synthesized by conventional metallurgical method is its poor activation characteristics. The alloy reacts with hydrogen only after complicated activation procedure involving exposure to high temperature (~400° C) and high pressure for several days. We recently found that by doping TiFe with Zr and Zr-Ni alloys the activation could be performed rapidly at room temperature. Microstructure shows the presence of a Zr-rich intergranular phase inside the TiFe rich matrix which is responsible for improved hydrogenation characteristics observed in modified TiFe alloy. In order to fully understand the activation mechanism the doping amount was changed and crystal structure and hydrogen sorption properties of TiFe alloys were investigated. We also studied the composition TiFe0.9Mn0.1 because the presence of manganese may change the interdiffusion of elements from the matrix to the intergranular phase.

 
FB-2.2  Complex Hydrides

FB-2.2:IL01  Materials and Systems for Hydrogen Storage
M. DORNHEIM, J. JEPSEN, F. KARIMI, N. BERGEMANN, C. PISTIDDA, S. BÖRRIES, J. BELLOSTA VON COLBE, A.-L. CHAUDHARY, K. TAUBE, G. SAHLMANN, N. BUSCH, O. METZ, C. HORSTMANN, T. KLASSEN, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany

In this presentation results concerning reaction mechanism and sorption behaviour of complex hydrides and Reactive Hydride Composites are presented. The progress in the optimisation of reaction kinetics and the potential of different hydrides and hydride composites is discussed.
Possible low cost routes for hydrogen storage materials production will be shown. Results of hydrogen storage compacts and tank testing based on selected hydride materials are shown.


FB-2.2:L02  Role of Gas Back Pressure in Dehydrogenation Reaction of LiBH4-based Reactive Hydride Composites
KEE-BUM KIM, J.-H. SHIM, I.-S. CHOI, Y.W. CHO, Korea Institute of Science and Technology, Seoul, Republic of Korea; K.-B. KIM, K.H. OH, Seoul National University, Seoul, Republic of Korea

Dehydrogenation reactions of LiBH4-based reactive hydride composites were verified in various gas pressure atmospheres. As a result, the application of gas back pressure determines the dehydrogenation reaction pathways and improves the reaction kinetics in 2LiBH4-MgH2, 4LiBH4-YH3 and 6LiBH4-CeH2 composite. In this enhancement, it was found out that the pressure atmosphere applied in the early stage of dehydrogenation reaction plays a crucial role to control the subsequent reaction pathways and the application of inert gas back pressures as well as hydrogen back pressure positively influences on the reaction. Since there is no additives, there is less degradation of H2 capacity and it will be effective to achieve a high reversible hydrogen storage capacity with enhanced reaction kinetics. In this study, we addresses the role of gas back pressures to determine the dehydrogenation reactions of various LiBH4-based reactive hydride composites in detail.


FB-2.2:L03  In-situ Temperature Dependent Infrared Spectroscopy of Ammonia Borane Dehydrogenation
N. BILISKOV, Rudjer Boskovic Institute, Division of Materials Chemistry, Laboratory of Solid State and Complex Compounds Chemistry, Zagreb, Croatia; D. Vojta, Rudjer Boskovic Institute, Division of Organic Chemistry and Biochemistry, Laboratory of Molecular Spectroscopy, Zagreb, Croatia

Infrared spectroscopy (IR) is one of the commonly employed experimental methods for the study of hydrogen sorption performance of complex hydrides, but its full power is not well recognised. It is used almost exclusively as supporting routine. However, infrared spectra give a unique insight into the system at molecular level and they are very rich in contained information. Furthermore, it enables a simple and accurate insight in changes at molecular level. For example, detection of phase changes is enabled by simple and straightforward analysis of perturbation-dependent (where perturbation can be temperature, pressure etc.) transmission baseline, while molecular background of these transitions are obtained by the analysis of other spectral features. An elegant way to identify mutual changes among the involved functional groups is 2D correlation analysis, which enables more focused and detailed insight into particular process. Also, IR spectroscopy is well recognised as one of the most powerful experimental techniques for investigation of hydrogen bonding.
The power of this technique will be illustrated here on the example of dehydrogenation of ammonia borane, where dihydrogen bonding plays a crucial role and some important mechanistic aspects remained still unexplained.


FB-2.2:IL04  Potential and Limitation of Complex hydrides for Hydrogen Storage
A. ZÜTTEL, EMPA, Dübendorf, Switzerland; SHIN-ICHI ORIMO, Tohoku University, Sendai, Japan

Hydrogen production and storage is the key technology for the storage of renewable energy. The most used storage methodes, i.e. compressed hydrogen storage and liquid hydrogen are based on established technologies and store hydrogen in its molecular form. However, compressed hydrogen requires high pressures and liquid hydrogen exists only at a temperature below 32K. The storage of hydrogen in metal hydrides exhibits volumetric hydrogen density twice the density of liquid hydrogen. Due to the mass of the metals compared to hydrogen the gravimetric density is limited to less than 3 mass%. Complex hydrides exhibit a volumetric hydrogen density of up to 150 kg/m3 and gravimetric density of up to 20 mass%. This corresponds to approx. half the energy density of hydrocarbons. Therefore, reducing CO2 from the atmosphere with hydrogen produced from renewable energy leads to a synthetic fuels (hydrocarbon) with the same energy density as the fossil fuels. The potential of hydrogen storage materials will be reviewed and the limitations will be elaborated.


FB-2.2:IL05  Improved Dehydrogenation Properties of the Mg(NH2)2-2LiH System
H.J. CAO, J.H. WANG, Z.T. XIONG, G.T. WU, PING CHEN, Dalian Institute of Chemical Physcis (CAS), Dalian, China

A number of amide-hydride systems have been investigated in the past 10 years, among which LiNH2-2LiH and Mg(NH2)2-2LiH are the most studied. Experimental results show that ~ 10.5 and 5.5 wt.% of hydrogen can be stored reversibly in those systems through the reactions (1) and (2), respectively.
LiNH2 +2 LiH = Li3N + 2 H2 (1)
Mg(NH2)2 + 2LiH = Li2Mg(NH)2 + 2 H2 (2)
Comparatively, Mg(NH2)2-2LiH possesses suitable thermodynamic properties which allow hydrogen desorption at 1.0 bar equilibrium pressure to occur at temperatures below 363K. However, relatively high operating temperature is needed which is due to the existence of severe kinetic barrier. Conventional transition metals have limited catalytic effect. Interestingly, LiBH4 or KH of 3 mol% works well which can significantly enhance the rate of dehydrogenation. In the meanwhile, by adding proper compounds which can form more stable intermediate with imide, the Mg(NH2)2-2LiH can thermodynamically desorb 1.0 bar hydrogen at temperatures below 323K.


FB-2.2:IL06  Structural Characterisation of Complex Hydrides
B.C. HAUBACK, C. FROMMEN, M.H. SORBY, Institute for Energy Technology, Physics Department, Kjeller, Norway

One of the greatest barriers of widespread introduction of hydrogen in global energy systems is an efficient and safe storage method. Complex hydrides based on the elements aluminium, boron, magnesium and nitrogen have recently been extensively studied for hydrogen storage.
In order to understand the properties and to determine new compounds, detailed knowledge about the position of the atoms is of major importance. Neutron diffraction is a unique tool for studies of hydrogen in hydrogen storage materials. For studies of compounds with both light and heavier elements the combination of powder neutron diffraction (PND) and X-rays diffraction is crucial. For complicated structural features and in-situ experiments the use of synchrotron radiation powder X-ray diffraction (SR-PXD) is important. The PND experiments are performed with the PUS diffractometer at the JEEP II reactor at IFE and the SR-PXD experiments at SNBL, ESRF. IR, Raman and NMR methods have contributed to the understanding of structural features.
Detailed structural studies of novel transition metal and mixed borohydrides with anion and/or cation substitution will be presented.
Financial support from Research Council of Norway and European Commission FP7 projects are acknowledged.


FB-2.2:IL07  Interface Reactions Influences the Reaction Path of Hydride Composite
A. BORGSCHULTE, S. KATO, A. ZÜTTEL, E. CALLINI, Empa, Laboratory Hydrogen & Energy, Dübendorf, Switzerland

The use of the interaction of two hydrides is a well-known concept used to increase the hydrogen equilibrium pressure of composite mixtures in comparison to that of pure systems. The thermodynamics and reaction kinetics of such hydride composites are reviewed and experimentally verified using the example NaBH4 + MgH2. Particular emphasis is placed on the measurement of the kinetics and stability using thermodesorption experiments and measurements of pressure-composition isotherms, respectively. The interface reactions in the composite reaction were analysed by in situ X-ray photoelectron spectroscopy and by simultaneously probing D2 desorption from NaBD4 and H2 desorption from MgH2. The observed destabilisation is in quantitative agreement with the calculated thermodynamic properties, including enthalpy and entropy. The results are discussed with respect to kinetic limitations of the hydrogen desorption mechanism at interfaces. General aspects of modifying hydrogen sorption properties via hydride composites are given.

 
FB-2.3  Chemical Hydrides

FB-2.3:IL01  Hydrogen Production from Sodium Borohydride Hydrolysis: A Density Functional Theory Study
PING LI, G. HENKELMAN, J.K. JOHNSON, University of Pittsburgh, Pittsburgh, PA, USA; University of Texas at Austin, USA

NaBH4 is a promising hydrogen storage material due to its high hydrogen content, relative safety, and low cost. Hydrolysis of NaBH4 has found application in niche markets such as portable energy generation. Recently, Matthews and coworkers demonstrated that steam hydrolysis of NaBH4 can be used to release hydrogen with both fast kinetics and high extent of reaction without the use of any catalyst and with reduced water consumption. However, the basic mechanism of NaBH4 hydrolysis is not understood on a molecular level. We have performed first-principles density functional theory calculations to investigate the elementary reaction steps in aqueous NaBH4 hydrolysis. Detailed understanding of these steps would be useful for reaction condition optimization, catalyst design, and ultimately for precise control of the reaction in practical applications. We identified energy barriers and reaction intermediates for each elementary step. Taken together, these steps provide a full picture of the NaBH4 hydrolysis reaction at the molecular level. We have identified unexpected reaction mechanisms that are relevant to a larger class of reactions involving coupled proton and hydride transfer events and agostic interactions in the absence of any transition metal species.


FB-2.3:L03  Mixed Metal Ammine Complexes for Hydrogen Storage
D. BLANCHARD, P. B. JENSEN, T. VEGGE, Department of Energy Conversion and Storage, DTU, Roskilde, Denmark; A. KLUKOWSKA, U. QUAADE, Amminex Emissions Technology A/S, Søborg, Denmark

Metal amine complexes are essential materials for storage and delivery of Nh3 and thus H2. NH3 has a high H2 density compared to other hydrogen storage materials, its synthesis and distribution relies on well-developed technologies. It can be used in Co2 free power generation, easy catalytic decomnposition, and for deNOx of diesel exhaust.
Metal ammine have been extensively studied and alkaline earth metal halides are commonly used due to their availability and high NH3 contents. Among them, SrCl2 is especially interesting with its high content and optimal desorption temperatures. It binds 8 NH3 molecules, and 7 are easily available (< 100 °C). The 8th rarely desorbed because it requires higher temperatures (> 120 °C), above standard operating conditions.
To increase the amount of NH3 available below 100 °C we investigated the possibillity to destabillize Sr(NH3)8Cl2 while keepping the equilibrium pressure at a resonable level, ~1 bar RT. We have been successful in synthesizing solid solution, bi and tri-cation mixed salts, with very good properties. We have subsituted Sr by alcaline earth metals and/or others. We have isolated pure phases with very good and stable properties for ammonia cycling.

 
FB-2.4  Carbon Based Materials and Other High Surface Area Adsorbents

FB-2.4:IL01  Nanoconfined Complex Metal Hydrides
P.E. DE JONGH, Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands

LiBH4 is a so-called "complex hydride", a solid consisting of a lattice of Li+ cations and BH4- anions, with the boron and hydrogen covalently bound within the complex anion. It is potentially a very interesting material for reversible solid state hydrogen storage (containing 18.5 wt% hydrogen) and as a solid state Li-ion battery electrolyte. However, 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 °C), while appreciable Li+ ion mobility is only found in the high temperature hexagonal phase (above 110 °C). It is well known that confining matter to small sizes, for instance by encapsulation in nanopores, can shift phase transition temperatures. We explored how confining LiBH4 in nanopores of carbon and silica scaffolds influences the phase transition temperatures and induces high mobilities at low temperatures, as evidenced by calorimetric, quasi-elastic neutron scattering, and solid state NMR measurements.[1,2]
[1] A. Remhof, P.E. de Jongh, et al. J. Phys. Chem. C 117 (2013), 3789-3798.
[2] M.H.W. Verkuijlen, P.E de Jongh et al. , J. Phys. Chem. C 116 (2012) 22169-22178.


FB-2.4:L03  Cycling, Kinetic and Structural Hydrogenation Properties of MgH2-TiH2 Nanocomposites
F. CUEVAS, M. PONTHIEU, M. LATROCHE, ICMPE, CNRS, Thiais, France; J.M. BELLOSTA VON COLBE, M. DORNHEIM, HZG, Centre for Materials and Coastal Research, Geesthacht, Germany; J.F. FERNÁNDEZ, Dpto. Física de Materiales, Universidad Autónoma de Madrid, Madrid, Spain

MgH2-TiH2 nanocomposites can be easily synthesized by reactive ball milling of elemental powders under hydrogen pressure [1]. They consist of a homogeneous mixture of MgH2 and TiH2 phases with crystallite sizes ranging from 4 to 12 nm. Hydrogenation and structural properties during reversible H-loading have been measured by the Sievert's method, by high-pressure differential scanning calorimetry and by neutron diffraction for the representative composite 0.7MgH2-0.3TiH2. This material exhibits outstanding sorption kinetics with reaction time below 200 s at 573 K and cycling stability over 100 cycles. Reversible hydrogen storage occurs through the MgH2/Mg phase transformation whereas fast sorption kinetics are promoted by the TiH2 phase. Neutron studies demonstrate that TiH2 inhibits MgH2 crystal growth and allows for fast H-mobility thanks to the formation of coupled TiH2/MgH2 interfaces as well as sub-stoichiometric hydrides [2]. The study of hydrogen storage properties of 0.7MgH2-0.3TiH2 nanocomposite in medium-size storage tanks (sample mass ~ 50 g) is in progress and results will be reported at the conference.
References
[1] F. Cuevas et al. Phys. Chem. Chem. Phys., 14 (2012) 1200.
[2] M. Ponthieu et al. J. Phys. Chem. C, 117 (2013) 18851.


FB-2.4:L04  Hydrogen Storage Properties of Decorated Fullerides
C. MILANESE, A. GIRELLA, A. MARINI, Pavia H2 Lab, Chemistry Department, University of Pavia, Italy; M. ARAMINI, M. GABOARDI, D. PONTIROLI, M. RICCO', Carbon Nanostructures Lab, Department of Physics and Earth Science, University of Parma, Italy

C-based materials, such as fullerene and graphene derivatives, are fascinating systems for solid state H2 storage. Recent experimental works showed very interesting gravimetric capacity for Li6C60 and Na10C60, i.e. 5 wt% and 3.5 wt% (at T > 250 °C and 100 bar), thanks to the formation of a hydrogenated phase of C60. In this work, the H2 sorption characteristics of Li and Mg intercalated fullerenes were explored. Moreover, we tried to improve the kinetic and thermodynamic properties of this class of materials by decoration with different transition metals and lanthanides (Pt, Pd, Ni, Eu, .). In particular, we developed ad hoc syntheses depending on the chemical nature of the metal used for the decoration. Different amounts of metals were used in order to explore a possible correlation between the stoichiometry of the compounds and the sorption properties. Coupled calorimetric - manometric analyses and PCI measurements were performed, for the first time in literature, allowing the determination of the kinetic and thermodynamic features of all the sorption steps. X-Ray powder diffraction studies, Raman and MuSR spectroscopies were used to describe the hydrogenation mechanism of the compounds. Very promising results were obtained for the Li6C60 decoration with Pt and Pd.


FB-2.4:IL05  Activated Carbon Fibre Monoliths for Hydrogen Storage
M. KUNOWSKY, J.P. MARCO-LOZAR, A. LINARES-SOLANO, University of Alicante, Alicante, Spain

Porous adsorbents are currently investigated for hydrogen storage application. From a practical point of view, in addition to high porosity developments, high material densities are required, in order to confine as much material as possible in a tank device. Here, we study activated carbon fibres and nanofibres (ACF) which were obtained by activation with suitable activation agents (e.g., KOH and CO2). Their density can be improved in two ways: By packing under mechanical pressure, or by synthesising monoliths from them. Hydrogen adsorption isotherms are measured for all of the adsorbents at room temperature and under high pressures (up to 20 MPa). The gravimetric H2 adsorption is directly related to the porosity of the adsorbent. In volumetric terms, H2 adsorption depends on both, porosity and material density. Thus, the results for the original ACFs can be significantly increased by packing under mechanical pressure. However, under practical conditions their packing may not be feasible, due to engineering constrains. Here, ACF monoliths are beneficial: On the one hand, they significantly increase the volumetric H2 adsorption and, on the other hand, they provide the additional advantages of high mechanical resistance and easy handling.


FB-2.4:IL08  Hydrogen Storage in Metal-organic Frameworks
MYUNGHYUN PAIK SUH, Department of Chemistry, Seoul National University, Seoul, Republic of Korea

Development of hydrogen storage materials has attracted great attention because of the need to replace current carbon-based energy sources and the implication of carbon dioxide emission in the global warming. Metal-organic frameworks (MOFs) can be applied in hydrogen storage due to their high surface areas and tunable pore properties. MOFs can store large amount of hydrogen at 77 K, but their storage capacities at ambient temperature drop down to very low values since the interaction energy between MOFs and H2 gas is very weak.
To enhance hydrogen storage capabilities of MOFs, we synthesized MOFs and modified their pore spaces. The H2 uptake capacities of MOFs could be increased by creation of vacant coordination sites at the metal ions, incorporation of crown ethers, and fabrication of metal (Pd, Mg) nanoparticles in the pores. A Zn-MOF having a crown ether moiety provides the binding sites for K+, NH4+, and methylviologen (MV2+), and the MOF incorporating K+ ion exhibits significantly enhanced isosteric heat (Qst) of the H2 adsorption. A MOF embedded with Mg nano crystals is stores H2 gas by physical adsorption at low temperatures and by chemical absorption at high temperatures, and the MOF and Mg exhibit synergistic effects on H2 adsorption.

 
FB-2.5  Theoretical Modelling, New Characterization Methods and Storage Testing

FB-2.5:IL01  Analyzing Pure and Doped Aluminum Clusters as Potential Hydrogen Storage Materials
A. GOLDBERG, M.D. HALLS, Schrodinger Inc., San Diego, CA, USA

In this paper we explore the interaction of hydrogen with Al13 and Al12 clusters, related super-assemblies and doped AlnBm clusters. Density Functional Theory (DFT) as implemented in Jaguar code of Materials Science Suite provided by Schrodinger Inc. is employed to analyze the structural stability, kinetic barriers for external to internal hydrogen atom transitions, dissociation of an H2 molecule in a cage and between the clusters. A dependence on Al-cluster stoichiometry is predicted, leading to different preferred hydrogen reaction channels. DFT simulations predict that Al13 clusters absorb hydrogen atoms on hollow and bridge positions,while Al12 clusters adsorb hydrogen by in-cage displacement. Furthermore, B12 clusters interact with hydrogen by having H-atoms bonded to all surface atoms forming a B12H12 cluster. As the percentage of hydrogen atoms inside or outside of the cluster increases those clusters become unstable. Using a virtual screening computational technique a cluster library of AlnBm structures with n+m=12, that is without a central atom, and with n+m=13 including a central atom were generated and analyzed using DFT. The most energetically stable mixed clusters are identified and analyzed to estimate the highest internal and external hydrogen absorption capacity


FB-2.5:L02  Thermodynamic Modelling of Borohydrides for Hydrogen Storage
E.R. PINATEL, E. ALBANESE, B. CIVALLERI, M. BARICCO, Dipartimento di Chimica and NIS, Università di Torino, Torino, Italy

A full understanding of thermodynamic properties is fundamental for hydrogen storage materials, not only because a dehydrogenation enthalpy of 30-35 kJ/molH2 is required for reversible hydrogen sorption at ambient conditions, but also to predict, and possibly avoid, the occurrence of competitive reactions that could limit hydrogen sorption to few cycles.
The Calphad method is a valuable tool, able to provide a full picture of the thermodynamic properties. It is based on a parametric description of the Gibbs free energy of each phase as a function of temperature, pressure and composition. Parameters are evaluated on the basis of experimental data as well as outputs of ab initio calculations.
In the present work, thermodynamic properties for different borohydride based materials (Ca(BH4)2, LiBH4, Mg(BH4)2, 2LiBH4+MgH2 and Mg(1-x)Znx(BH4)2 ) have been calculated and compared to experimental data. Thermodynamic databases obtained according to this method can be used to predict stable and metastable equilibrium phases and to calculate a variety of property diagrams useful for the interpretation of experiments and to provide input for thermo-fluido-dynamic modelling. Moreover databases can be coupled in order to extend the description to more complex systems.


FB-2.5:L04  Theoretical Study of the SmCo5Hx Compounds: Cohesive and Magnetic Properties
G.I. MILETIC, Laboratory for Solid State and Complex Compounds Chemistry, Division of Materials Chemistry, Institute Rudjer Boskoviæ, Zagreb, Croatia

DFT calculations were performed for SmCo5Hx compounds to investigate their stability, structural and magnetic properties. Different interstitial sites were considered for hydrogen atoms to investigate their site preference. α-solid solution and β-phase were modeled and energetics of their formation through, respectively, reactions SmCo5→α and α→β was investigated. Magnetic moments and their dependence on hydrogen content and positions of hydrogen atoms were investigated. Obtained results were compared with the previously obtained experimental and theoretical data.


FB-2.5:L05  Nanoconfined Complex Hydrides via Inverse Atomistic Calculations
Z. LODZIANA, P. BLOÑSKI, Polish Academy of Sciences, Institute of Nuclear Physics, Kraków, Poland

Thermodynamic destabilization of metal borohydrides via nano-confinement opens new directions of tuning their thermodynamic properties. Nano-confinement pose difficulties for experimental and theoretical characterization of nano-sized compounds.
We show that density functional theory calculations of measurable properties like NMR parameters and dynamical properties when compared to experimental data acquired for nano-confined LiBH4 allow formulation of the atomistic model of this system. Matching measured NMR chemical shift to this resulting from the atomic structure of nano-clusters provides insight into relevant properties of confined compound. The properties of nano-size lithium borohydride clusters are governed by the low surface energy that cause alteration of thermodynamic properties, while dynamical features are similar as for the high temperature phase of this compound.
This method applied for other complex hydrides provides firm theoretical support for future studies of nano-confined systems for hydrogen storage.


FB-2.5:IL06  Nanomaterials for Hydrogen Storage
P. JENA, Virginia Commonwealth University, Richmond, VA, USA

A fundamental understanding of the interaction of hydrogen with materials is necessary to develop efficient hydrogen storage materials for applications in the mobile industry. This talk will deal with firstprinciples calculations aimed at elucidating the novel properties of materials at the nanoscale and how they can improve the thermodynamics and kinetics of hydrogen. In particular, I will discuss how carbon based nanostructures such as nanotubes and fullerenes can not only be used as catalysts to improve hydrogen uptake and release in complex light metal hydrides such as alanates, borohydrides, and imides but also how they can be functionalized with alkali metal atoms to adsorb hydrogen in a novel quasi-molecular form. The role of electric fields in reversible hydrogen storage will also be discussed. Studies on clusters that can lead to synthesis of safe materials for hydrogen dtorage will be highlighted. These results, based upon density functional theory and quantum molecular dynamics, provide a fundamental understanding of the interaction of molecular hydrogen with hosts consisting of light elements.


FB-2.5:L08  Computational Search for Improved Ammonia Storage Materials
P.B. JENSEN, S. LYSGAARD, T. VEGGE, DTU Energy Conversion, Technical University of Denmark, Kgs. Lyngby, Denmark; U. QUAADE, Amminex Emissions Technology, Soeborg, Denmark

Metal halide ammines, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, can reversibly store ammonia, with high volumetric hydrogen storage capacities. The storage in the halide ammines is very safe, and the salts are therefore highly relevant as a carbon-free energy carrier in future transportation infrastructure. In this project we are searching for improved mixed materials with optimal desorption temperatures and kinetics, optimally releasing all ammonia in one step.
We apply Density Functional Theory, DFT, calculations on mixed compounds selected by a Genetic Algorithm (GA), relying on biological principles of natural selection. The GA is evolving from an initial (random) population and selecting those with highest fitness, a function based on e.g. stability, release temperature, storage capacity and the price of the elements. The search space includes all alkaline earth, 3d and 4d metals in combination with chloride, bromide or iodide, and mixtures thereof. In total the search space consists of thousands of combinations, which makes a GA ideal, to reduce the number of necessary calculations. We are screening for a one step release from either a hexa or octa ammine, and we have found promising candidates, which will be further investigated - both computationally and experimentally.


FB-2.5:L09  Novel FIB-SEM Methodologies for 3D Nanostructuring and Nanoanalysis of Hydrogen Storage Materials
M. SEZEN¹, F. BAKAN¹, M.A. GULGUN², E. RABKIN³, ¹Sabanci University Nanotechnology Research and Application Center, Orhanli-Tuzla, Istanbul, Turkey; ²Sabanci University; Faculty of Engineering and Natural Sciences; Orhanli-Tuzla, Istanbul, Turkey; ³Department of Materials Science and Engineering, Technion, Haifa, Israel

Focused Ion Beams (FIB) technology is based on structuring, modification and prototyping from micro- to nanometer scales. The versatility of dual-beam platforms leads to flexibility on developing new methodologies of nanostructuring and nanoanalysis upon the properties of diverse materials and systems. In particular; in order to reveal the geometric and elemental distribution of material systems that are based on nano-features, electron tomography applications are being widely used. Specific samples preparation techniques that keep the original structures of the sections to be investigated at the TEM are often required. The recent work focuses on the FIB-based development of TEM specimen preparation and structuring techniques for novel Hydrogen Storage materials that have 3D-network-structures. Moreover in-situ electron beam imaging in 3D on the related materials is performed using the ‘slice and view’ technique which is available by dual-beam instruments. By this means, while the samples to be investigated in the TEM provide 3D information at the nanometer-scale and below; via FIB tomography sectioning, the information in the scale ranging from micrometers to tens of nanometers are collected from the identical sample and the data are comparatively and complimentarily evaluated.
Acknowledgements:
112M195 TUBITAK Carrier Development Grant is gratefully acknowledged for the financial support. The authors also would like to thank the support by COST Action MP1103, in which Dr. Sezen is currently participating.


FB-2.5:L10  Thin Film Based Fiber Optic Hydrogen Sensor for Continuously Monitoring the Health Status of Power Transformers
M. VICTORIA, R.J. WESTERWAAL, T. MAK, H. SCHREUDERS, C. BOELSMA, B. DAM, Materials for Energy Conversion and Storage (MECS), Faculty of Applied Sciences, Dept. Chemical Engineering, Delft University of Technology, Delft, The Netherlands

To fulfil the world's ever-increasing energy needs, a reliable electric network is necessary. In this grid the power transformer plays a key role. Malfunction of power transformers is often related to failures in their insulating system. These failures are accompanied by gas generation, especially hydrogen, in the oil. Therefore monitoring the hydrogen dissolved in the insulating oil gives an insight in the transformer's health condition and provides information on the type of fault occurring.
A promising fiber optic hydrogen sensing system is based on using a MgTi thin film as a sensing layer. The concentration of hydrogen dissolved in oil can be determined by measuring the changes in reflection of the thin film as it absorbs hydrogen. We will show that, based upon this principle, MgTi thin films are able to measure quantitatively the hydrogen concentration in oil in a reliable way in the concentration range of interest above 80C. This remote measurement technique has the major advantage of being intrinsically safe in an explosive environment due to the lack of electric leads in the sensing area. Furthermore, it allows the combination of several sensors into one sensing system. We will also show an outlook on new materials to expand the detection range at lower temperatures.
 
 
Poster Presentations

FB:P01  The Effect of Doping of Fe into TiO2 Layer in Fe2O3/TiO2/FTO System for High Performance of Water Splitting
A. AZAD¹, EUL NOH¹, HYO JIN OH¹, BO RA KIM¹, KANG SEOP YUN¹, HEE JUNE JEONG¹, WOO SEUNG KANG², SANG CHUL JUNG³, SUN JAE KIM¹, ¹Institute/Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul, Korea; ²Dept. of Metallurgical & Materials Engineering, Inha Technical College, Incheon, Korea; ³Dept. of Environmental Engineering, Sunchon National University, Suncheon, Jeonnam, Korea

Hydrogen has unique physical and chemical properties which present benefits and challenges to its successful widespread adoption as a fuel. The photoelectrochemical (PEC) water splitting process with semiconductor metal oxides can be a promising solution to the global energy problem. Although amongst metal oxides Fe2O3 by 2.2 e.v bang gap energy is more applicable, for reducing the recombination of electron and hole Fe was doped into TiO2.In this study Fe-doped TiO2 photocatalysts were prepared by hydrothermal method and by using titanium isopropoxide (TTIP) as a precursor, acetyl acetone as a stabilizer and luryl-amine hydrcholoride(LAHC) as a surfactant for producing hydrogen under visible light, then it was coated by Fe2O3 for demonstration the best results and for comparing with Fe2O3/TiO2/FTO structures by using LBL-SA method and dipping process on FTO glass according to our previous report.The microstructure, crystallinity and optical absorbance were investigated by using scanning electron microstructure SEM, X-ray diffraction and UV-vis spectroscopy respectively,and also to obtain higher photocurrent for water splitting I-V curves of both samples were analysed. According to diagrams the Fe2O3 coated on Fe -doped TiO2 has been shown best results.


FB:P02  Synthesis of Macroporous Materials as the Immobilizing Agent for Photosynthetic Bacteria in Photobiological Hydrogen Generation
K. DYBA, R. ZAGRODNIK, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland

Macroporous materials in theirs monolithic and membrane form can find many applications in science and industry. In recent years, generation of photobiological hydrogen has raised great interest in the area of alternative methods of hydrogen production. Immobilization of photosynthetic bacteria improves process parameters what leads to increase of bacteria activity and consequently better hydrogen yield.
The main research object was to conceive materials which can be used as the immobilizing agent for photosynthetic bacteria in photobiological hydrogen generation, because of their compatibility, transparency and interconnected porous structure.
This communication describes synthesis of two types of macroporous materials - inorganic and organic. Inorganic alumina was synthesized in a simple way by the sol-gel method, organic trimethylene carbonate and L-lactide copolymer was achieved during ring-opening polymerization. Macroporous structure of materials was obtained during impregnation of sugar template plates with dimension of the sugar particles of 300-400 micrometers.
Both materials exhibit appropriate thermomechanical and physical properties what gives opportunity to use received materials as the immobilizing media for bacteria used in photobiological hydrogen generation.


FB:P03  Optimization of Hydrogen Production by Co-culture of Clostridium Beijerinckii and Rhodobacter Sphaeroides Bacteria
R. ZAGRODNIK, Faculty of Chemistry, Adam Mickiewicz University, Poznan, Poland

The biological methods of hydrogen generation have attracted a significant interest recently. In this work the hybrid system applying both dark fermentation bacteria in co-culture was tested. Objective of this work was to investigate the optimization of different parameters on co-culture of Clostridium beijerinckii DSM-791 and Rhodobacter sphaeroides O.U.001. The effect of glucose concentration (1 – 5 g/L), temperature and initial pH (6,5 – 7,5) was analyzed. Moreover the influence of organic nitrogen sources were tested for their capacity to support hydrogen production (yeast extract, peptone, glutamic acid). Fermentations were conducted in batch tests with glucose as sole substrate. Hydrogen production in mixed culture was compared with pure cultures. The process was greatly affected by pH and light/dark bacteria ratio. Liquid metabolites, namely acetic and butyric acids, from the dark fermentation step were the source of organic carbon for photosynthetic bacteria. This increased the hydrogen yield in comparison to single-step dark fermentation to over 4 mol H₂/mol glucose. Obtained results showed that combination of photo and dark fermentation may increase hydrogen production and conversion efficiency of complex substrates or wastewaters.


FB:P04  The Effect of Gas Compositions on the Performance and Durability of SOECs
SUN-DONG KIM, DOO-WON SEO, JI-HAENG YU, SANG-KUK WOO, Korea Institute of Energy Research, Daejeon, Korea

High temperature electrolysis (HTE) was performed to produce hydrogen using cathode supported tubular solid oxide electrolysis cells. The single cell composed of Ni-YSZ cathode support, YSZ electrolyte, LSM anode and, especially, ceramic interconnector. The advantages of these all-in-one type single cells are that the volumetric power densities are very high and metallic interconnectors are unnecessary. The current-voltage characteristics and the hydrogen producing rate were investigated between 750 and 850°C. The cathode supported cell showed the hydrogen evolution rate over 8.0 cc/min∙cm2 (@ 1.2A/cm2), which was ~95% of the theoretical value calculated from Faraday's law. When the content of water vapor was over 30 vol%, the efficiency and stability of steam electrolysis was acceptable. The EIS study confirmed that sufficient steam content enhances the electrochemical splitting of water and decreases the activation energy for water electrolysis at high temperatures. In our 3-cell stack test, the hydrogen production rate was 4.1 lh-1, and the total hydrogen production was 144.32 l during 37.1 h of operation.


FB:P05  Distillery Waste Waters in Photofermenative Hydrogen Generation
K. SEIFERT, R. ZAGRODNIK, M. STODOLNY, K. DYBA, M. LANIECKI, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland

Distillery waste waters remaining after alcohol production from corn were tested as the source of organic carbon in photofermentative hydrogen production in presence of Rhodobacter sphaeroides bacteria.
Two types of wastes were tested: remaining after first distillation (A) and condensed syrup (B) (condensation of A). Both wastes indicated relatively low pH (3.4 and 3.8). Both the COD value (325 g2/l) as well as content of glycerol (36 g/l), lactic acid (13g/l) and methanol (11.5 g/l) in syrup were higher than in those originating from 1st distillation (COD- 250 gO2/l, glycerol 4 g/l, lactic acid 1.3 g/land methanol 1.6 g/l).
Tests with different concentration of wastes replacing organic compounds in Biebl and Pfenning medium under illumination of 9 klx showed that maximum value of hydrogen was reached for syrup (B) - 1.6 lH2/l medium. An increase of waste concentration in medium resulted in the decrease of hydrogen yield. Lower values were also observed for waste A.
The HPLC measurements showed after fermentation the total reduction of VOC after photofermentation. The amount of photogenerated hydrogen is very high, however the necessity of dilution of the original wastes represent some disadvantage because of the large volumes required in this process.


FB:P06  Performance Assessment of Solid Oxide Cells under High Steam Content Electrolysis
N.P. KOTSIONOPOULOS, G. DE MARCO, T. MALKOW, G. TSOTRIDIS, European Commission, Directorate-General Joint Research Centre, Institute for Energy and Transport, Petten, The Netherlands

High temperature steam electrolysis for hydrogen production is considered as a promising, energy efficient and sustainable technology towards a successful low carbon economy. The key advantage of this technology is that it involves less electrical energy consumption, compared to conventional low temperature water electrolysis. Optimisation of the technology is however still required, mainly involving the lowering of the operational temperature, while maintaining a satisfactory performance level.
Two candidate Solid Oxide Electrolysis Cells (SOECs) were studied in terms of performance and durability in the Intermediate Temperature operational regime under high steam content. The tested cells were planar, anode (Ni-YSZ) supported with 80 cm2 active surface area. The electrolyte was a dense 8YSZ film, while two different air electrodes were used, namely Strontium doped Lanthanum Cobaltite (LSC) and Pr2NiO4- LSC. Both cells were tested in SOFC mode (100% H2) and SOEC mode (90% H2O - 10% H2) revealing similar initial performance. Durability experiments at thermo neutral voltage (1.28 V) were performed, exhibiting similar degradation rates and patterns, with the degradation being strongly affected by the steam utilisation.


FB:P07  Application of Liquid Wastes from Sugar Industry in Photofermentative Method of Hydrogen Generation
K. SEIFERT, R. ZAGRODNIK, M. STODOLNY, M. LANIECKI, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland

Liquid wastes from sugar industry containing lactic acid (5g/l), acetic acid (1g/l) and glucose, lactose, fructose at lower concentrations, were used in photofermentation process with Rhodobacter sphaeroides towards hydrogen. Different concentrations of wastes ( 10, 20, 40, 60, 80 vol% and not diluted) were applied in experiments with fermentative medium containing macro- and microelements, iron glutamate and yeast extract. Several experiments were performed with medium containing no additional compounds. Samples in batch tests were illuminated with tungsten-mercury lamp (Ultra-Vitalux) at 25oC (light intensity - 9 klx).
It was found that amount of photogenerated hydrogen increases from 0.5 to 1.6 lH2/l medium until the waste concentration reached 60 vol.%. Simultaneously, the amount of biomass increased whereas COD value of the waste decreased. Application of higher concentration and undiluted waste did not change the efficiency reached for 60 vol.%. Concentration of hydrogen in biogas in all cases was close to 91%. The HPLC analysis of medium after photofermentation showed the total reduction of lactic and acetic acids. It was concluded that waste from sugar industry can be applied as an excellent substrate in photofermentative way of hydrogen generation.


FB:P08  Plasma Chemical Reactor for Hydrogen Production
G. PETRACONI, Technological Institute of Aeronautics, Sao José dos Campos, SP, Brazil; A.M. ESSIPTCHOUK, Luikov Heat- and Mass Transfer Institute, Minsk, Belarus

The process of carbon dioxide reforming of hydrocarbon feedstock (like natural gas, coal, petroleum coke, residual oil, glycerine, etc) for hydrogen production has attracted great attention from both environmental and industrial perspectives. The plasma chemical reactor for study the CO2 reforming of hydrocarbon gaseous feedstock is presented. The reactor consists of a DC plasma torch attached to a compact quenching chamber. The linear plasma torch with a reverse vortex flow and hollow blind-end cathode showed essentially improved performance: increased thermal efficiency and enthalpy of the plasma jet. The quenching chamber consists of a set of refrigerated discs equipped with flow turbulator. Estimated quenching rates are up to 10^7-10^8 K/s. Electrical and thermal characteristics of the plasma-chemical reactor torch as well as the energy efficiency of the process will be presented.


FB:P09  Hydrogen Production from Wind Power in Algeria
L. AICHE-HAMANE, Department of mechanics, Faculty of technology, University Saad Dahlab Blida, Algeria; M. HAMANE, Centre for Development of Renewable Energies (CDER), Algiers, Algeria; B. BENYOUCEF, Research Unit for Materials and Renewable Energies (URMER), University Aboubakr Belkaid Tlemcen, Algeria

Hydrogen can be a clean energy carrier if the resource is clean. Renewable energies are an attractive solution to this challenge. Among renewable energy sources, wind electricity in particular has become competitive in many markets around the world. Wind power has matured greatly over the last twenty years. Wind capacity has reached 282 275 MW in 2012 which represents an annual growth of 19.2%. However, the intermittency of the wind source makes necessary to develop efficient energy storage system. Hydrogen as an energy carrier, together with electrolyser and fuel cell technologies can provide a technical solution to this challenge. Furthermore, hydrogen can be used to power vehicles, replace natural gas for heating and cooking, and to generate electricity via fuel cells.
In this context, this study aims to show the potentialities of Algeria to develop wind power hydrogen systems and gives a methodology for hydrogen production by a simplified efficient system proposed in this paper. For this, a direct coupling of the wind turbine to the electrolyser via AC/ DC converter has been proposed in order to reduce power losses in the different electronically devices proposed by some systems configurations.
Algeria is the largest country in Africa, located in the northern part sharing a vast coastline of about 1200 km along the Mediterranean Sea. A wind resource assessment has been carried out in Algeria. The wind maps estimate the resource at 50 m hub height in terms of seven wind classes, ranging from the lowest class (<4 m/s), to the highest (> 9m/s) . Algeria has an interesting wind resource particularly in the southwest region which is remote area and where autonomous systems are more suitable. It is projected to install 30 MW of wind electricity in 2015.


FB:P11  Hydrogen Sorption Cycling Behaviour of MgH2 Powders and Pellets
G. DI GIROLAMO, D. MIRABILE GATTIA, A. MONTONE, ENEA, Materials Technology Unit, Casaccia Research Centre, Rome, Italy

Mg-based hydrides are promising materials for safe and easy hydrogen storage, due to their sorption capability, high capacity and low cost. The use of additives such as transition metal oxides in conjunction with the nanostructuring process allow to improve their slow kinetics.
To this purpose, in the present work the addition of different wt. % of catalyst to MgH2 powder particles was analyzed in terms of structure and kinetic performance.
The most promising nanostructured ball-milled MgH2-TiO2 powder was enriched with expanded natural graphite (ENG) to improve the thermal conductivity and then compacted in cylindrical pellets by cold pressing. Both the powder and the pellets were subjected to repeated hydrogen sorption cycles at 340 °C using a Sievert's type apparatus.
The pellets exhibited good kinetic performance and stability. The hydrogen storage capacity was not affected by long-term cycling, but the sorption kinetics decreased as the number of cycles increased, due to any microstructural changes. Indeed, hydrogen cycling promoted expansion and gradual swelling of the compacted pellet up to failure. The phase composition and the microstructural features were investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively.


FB:P14  Hydrogen Technologies and Applications: Safety
M. LLORCA, P. RUIZ, L.F. VEGA, MATGAS Research Center, Campus de la UAB, Bellaterra, Barcelona, Spain

We will present results obtained through a data gathering processes enclosed on the FCH-JU H2TRUST project (www.h2trust.eu). This project is a Coordination and Support Action created by a team of highly experienced and qualified industry and academic experts, aiming to guarantee a maximum level of safety for an accelerated deployment of the H2 economy, and to inform and prepare all industry stakeholders.
Results corresponding to the data collected by the stakeholders, recognized experts in this field, consumers and incident response bodies associated with fuel cells and hydrogen industries are included. Safety is considered in all the different hydrogen applications: production, storage, distribution, mobility, vehicles, non-vehicles and residential power generation. These results facilitate accessible information to make a risk analysis and recommendations to assure the successful and incident free development of the industry.
In the H2TRUST project, lead by MATGAS, also participate Air Products PLC, the European Hydrogen Association, SOLVAY SPECIALITY POLYMERS ITALY S.P.A., Politecnico di Milano, McPhy Energy SA, SOL S.p.A., Ciaotech S.r.l, and Technische Universiteit Eindhoven.