Nanocrystalline alanates -: Phase transformations, and catalysts

X-ray absorption in combination with powder X-ray diffraction and surface analytical studies were performed in order to investigate the chemical state, local order and spatial distribution of Ti in sodium alanate doped with TiCl3 and small Ti clusters. Kinetic investigations of the different hydrogenation and dehydrogenation steps of doped NaAlH4 indicate a nucleation and growth mechanism as rate limiting step in the transformation of the material. The results support a mechanism where Ti has an accelerating effect on the phase transformation, probably by introducing non-thermal defects into the material. (c) 2005 Elsevier B.V.. All rights reserved.