X-ray Absorption Spectroscopy and X-ray Diffraction Studies of the Thermal and Li-Driven Electrochemical Dehydrogenation of Nanocrystalline Complex Hydrides Mg2MHx (M = Co

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• 作者：K. Provost ; J. Zhang ; W. Za茂di ; V. Paul-Boncour ; J.-P. Bonnet ; F. Cuevas ; S. Belin ; L. Aymard ; M. Latroche
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：December 26, 2014
• 年：2014
• 卷：118
• 期：51
• 页码：29554-29567
• 全文大小：785K
• ISSN：1932-7455

文摘

The conversion reaction of Mg₂MH_x (M = Co, Ni) complex hydrides with lithium has been investigated by in and ex situ X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD). The structural properties of the involved products are compared to those obtained by thermal decomposition as well as to the results of previous studies on the Mg₂FeH₆ hydride. For all complex hydrides, M鈥揌 bonding is clearly evidenced by XAS. Whatever the decomposition reaction (thermal or electrochemical), Mg鈥揗 alloys (MgCo and Mg₂Ni) are obtained for Mg₂CoH₅ and Mg₂NiH₄, respectively, whereas hydrogen depletion from Mg₂FeH₆ leads to decomposition into elemental Mg and Fe. A significant disorder is observed for all M-containing phases, which increases as Fe < MgCo < Mg₂Ni; affects mainly the transition-metal sites; and is more pronounced for the electrochemical route. The consequences of these structural properties on the expected reversibility of the conversion reaction of Mg-based complex hydrides with lithium are discussed.