Titanium-halide catalyst-precursors in sodium aluminum hydrides

The kinetics of absorption and desorption of hydrogen from NaAlH4 have previously been shown to improve upon the addition of a catalyst-precursor such as TiCl3. In this paper we demonstrate that TiCl2, TiF3, and TiF3, all effectively improve sorption kinetics. Arrhenius data indicate that the catalyst precursors behave in essentially the same manner. Evidently the valency of Ti in the catalyst-precursor is inconsequential to the role of Ti in altering the kinetic mechanism. The formation of TiAl3 on doping with TiCl3 has been observed. The presence of TiAl3 appears to contribute in part to the enhanced kinetics in these systems. (C) 2003 Elsevier B.V. All rights reserved.