Hydrogen release of catalyzed lithium aluminum hydride by a mechanochemical reaction

The effects of various catalysts on the H-2 release characteristics of LiAlH4 were studied. It was established that the catalytic activity defined by the H-2 desorption capacity by a mechanochemical reaction decreased in the series TiCl3 > ZrCl4 > VCl3 > NiCl2 > ZnCl2. Transition metal trialummides Al3X (X = Ti, Zr, V, Ni) were prepared by the mechanochemical reaction of LiAlH4 and the metal chlorides, while the reaction of LiAlH4 and ZnCl2 yields Zn. The high catalytic activity was attributed to the lower percentage d-character and the electronegativity of those transition metals. The catalytic activity of Ni was also improved with decreasing the Ni particle size. Those catalysts were classified to two groups (1: TiCl3, ZrCl4; 2: VCl3, NiCl2, Ni, nano-Ni) from the viewpoint of the H-2 desorption mechanism. (C) 2007 Published by Elsevier B.V.