Variation and Influence of the Local Structure around Ti in NaAlH4 Doped with a Ti-Based Precursor

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• 作者：Aline L&eacute ; on ; J&ouml ; rg Rothe ; Maximilian Fichtner
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：November 8, 2007
• 年：2007
• 卷：111
• 期：44
• 页码：16664 - 16669
• 全文大小：134K
• 年卷期：v.111,no.44(November 8, 2007)
• ISSN：1932-7455

文摘

The kinetics and hydrogen storage capacity of Ti-doped sodium alanate prepared by ball milling of an Al_xTi_(1-x)nanocomposite as Ti-containing starting material with NaH remain comparably stable upon cycling underhydrogen. The reaction rate of this material is comparable to that of TiCl₃-doped samples. Extended X-rayabsorption fine structure (EXAFS) analysis revealed that forming an Al_xTi_(1-x) nanocomposite by the reductionof TiCl₄ by Al and subsequent annealing stabilizes the short-range order around Ti. The presence of stableAl-Ti phases at the beginning of the reaction prevents the subsequent formation of a Ti-Al cluster uponcycling under hydrogen, which is found in the case of doping with TiCl₃. When the atomic-scale behavior ofthis new material is compared with that of the TiCl₃- or Ti colloid-doped sodium alanates, it is found that thechemical state of Ti as well as its local structure seem to be relevant for the stability of the storage capacityand desorption/absorption reaction rate upon cycling under hydrogen.