In-Situ Diffraction Studies of Gas Storage Materials on a Laboratory X-Ray System
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In-Situ Diffraction Studies of Gas Storage Materials on a Laboratory X-Ray System Marco Sommariva1, Harald van Weeren1, Olga Narygina1, Jan-André Gertenbach1, Christian Resch2, Andreas Pein2, Vincent J. Smith3, Leonard J. Barbour3 1 PANalytical B.V., Lelyweg 1, Almelo 7602 EA, The Netherlands 2 Anton Paar GmbH, Anton-Paar-Strasse 20, 8054 Graz, Austria 3 Stellenbosch University, Corner of De Beer and Merriman streets, Stellenbosch 7602, Republic of South Africa ABSTRACT The sorption processes for hydrogen and carbon dioxide are of considerable, and growing interest, particularly due to their relevance to a society that seeks to replace fossil fuels with a more sustainable energy source. X-ray diffraction allows a unique perspective for studying structural modifications and reaction mechanisms that occur when gas and solid interact. The fundamental challenge associated with such a study is that experiments are conducted while the solid sample is held under a gas pressure. To date in-situ high gas pressure studies of this nature have typically been undertaken at large-scale facilities such as synchrotrons or on dedicated laboratory instruments. Here we report high-pressure XRD studies carried out on a multi-purpose diffractometer. To demonstrate the suitability of the equipment, two model studies were carried out, firstly the reversible hydrogen cycling over LaNi5, and secondly the structural change that occurs during the decomposition of ammonia borane that results in the generation of hydrogen gas in the reaction chamber. The results have been finally compared to the literature. The study has been made possible by the combination of rapid X-ray detectors with a reaction chamber capable of withstanding gas pressures up to 100 bar and temperatures up to 900 °C. INTRODUCTION Hydrogen storage and carbon dioxide sequestration have been topical research areas for a number of years due to concerns about climate change and with a desire of reduce the global reliance of society on fossil fuels. Hydrogen fuel cells promise a clean alternative, but with the limitations associated with the challenge of handling elemental hydrogen fuel safely. Materials that chemically bond hydrogen in a solid matrix, but that are capable of rapidly sorbing and desorbing large quantities of hydrogen gas offer a promising solution, particularly if such a material is also of low molecular weight to reduce mass and is able to achieve the uptake and release of hydrogen at temperatures below 180 °C. Light-element hydrides satisfy these criteria [1-3] and often exist in crystalline forms that undergo reversible structural modification during the uptake and release of hydrogen. For this reason these processes can be conveniently followed by X-ray diffraction studies, in spite of the low scattering power of the solid state matrix and the fact that hydrogen is essentially invisible to X-rays. The challenge is to observe the phase transitions of interest while the gas is simultaneously subjected to a gas pressures up to 100 bar so that deeper insights int
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