文摘
The kinetics and hydrogen storage capacity of Ti-doped sodium alanate prepared by ball milling of an AlxTi(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 AlxTi(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.