Abstract
Nanocrystalline MgH 2 with fine and evenly dispersed Nb hydride was prepared by ball milling a mixture of MgH 2 and 1 mol.% NbF 5. This NbH-catalyzed MgH 2 desorbed 6.3 wt.% H 2 in 15 min and absorbed more than 90% of its initial hydrogen capacity within 5 min at 573 K. Moreover, this fast sorption kinetics was maintained after 10 cycles. Based on X-ray diffraction and transmission electron microscopy/energy-dispersive spectroscopy analyses, it is suggested that NbF 5 melts during high-energy ball milling and this promotes the formation of extremely fine, film-like Nb hydride preferentially along the grain boundaries of nanocrystalline MgH 2 by a liquid/solid reaction. This unique nanostructured Nb hydride is believed to suppress the grain growth of MgH 2 quite effectively and thus maintain its initial catalytic effect throughout repeated hydrogenation–dehydrogenation cycles.
Published Version
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