Crystal Chemistry of Hydrogen Storage Materials
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1098-HH02-05
Crystal Chemistry of Hydrogen Storage Materials Martin O. Jones1, William I. F. David1,2, Simon R. Johnson1, Marco Sommariva2, Rebecca L. Lowton1, Elizabeth A. Nickels1, and Peter P. Edwards1 1 Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom 2 ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, United Kingdom ABSTRACT We review here work on two classes of compounds that have been promoted as potential hydrogen storage materials; alkali metal amides and borohydrides, highlighting how their crystal structure and chemical properties may be used to influence the key hydrogen absorption and desorption parameters in these materials. INTRODUCTION The use of hydrogen as an energy vector has the potential, in conjunction with fuel cells, to address a number of barriers to a sustainable energy future, such as the intermittency of sustainable energy sources and the mass production of vehicles that offer only water as an exhaust product. Hydrogen may also be used, again with fuel cells, for highly efficient and extremely long lived battery applications. Viable hydrogen storage is often cited as the key to the development of these technologies1-3. While the most likely short-term solution to the hydrogen storage problem is the use of composite pressure vessels for both stationary power plants and for vehicular power systems, the development of new solid-state hydrogen storage systems using advanced materials would have a major impact on the transition to a hydrogen economy. Substantial efforts4 worldwide now focus on obtaining a detailed understanding of the chemical and physical processes governing the all-important hydrogen-solid interactions. For vehicle based solid state hydrogen stores, a strict, and onerous, set of criteria have been established by the US department of energy. These state that a material should be able to store a high gravimetric (0.06Kg H2 / kg System) and volumetric (0.045kg H2 / L System) density of hydrogen and, absorb and desorb hydrogen at close to room temperature and pressure, possess rapid absorption (28 g / s) and desorption kinetics (0.02g / s / kW), be able to reversibly store hydrogen at these levels for 1000 cycles, be made from a cheap (4$ / kW hr) and readily available source and meet or exceed applicable environmental health and safety standards (targets for 2010)5. Efforts to identify materials capable of meeting some, or all, of these criteria have identified a number highly promising materials families, although it will come as no surprise to learn that, at present, no single material meets all of these requirements. A detailed understanding of the chemical and physical processes governing the hydrogen-material interactions is required for existing materials to allow their hydrogen absorption / desorption properties to be optimization, and, more importantly, to facilitate the discovery of new, more technologically appropriate materials. We present here the results of our studies into two promisin
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