Nature and role of Ti species in the hydrogenation of a NaH/Al mixture

A mixture of TiF3-doped NaH/Al was directly used as the starting material, and hydrogenated singly in order to study the chemical state and role of Ti species in hydrogenation. X-ray absorption spectroscopy shows that Ti3+ was essentially reduced to Ti-0 and formed Ti-Al clusters during the doping, i.e. the ball-milling process. The local environment around Ti atoms in the clusters became homogeneous and ordered after hydrogenation at 100-140 degrees C. The Ti-Al clusters are believed to be the catalyzing agent for the dissociation of the hydrogen molecule and the subsequent formation of the hydride.