H2 storage efficiency and sorption kinetics in composite materials

We have prepared two different kinds of composite materials for hydrogen storage and studied their H-2 storage capacity and desorption kinetics. The first composite material consists of magnesium-containing transition metal nanoclusters distributed in the Mg matrix (Mg:TM): this composite material shows better H-2 desorption performances than pure Mg. This improvement is attributed to the role of the MgH2-TM nanocluster interface as preferential site for hexagonal Mg (h-Mg) nucleation and to the rapid formation of interconnected h-Mg domains where H diffusion during desorption occurs. The second composite material consists of LaNi5 particles (size<30 mu m) distributed in a polymeric matrix. The H-2 storage capacity is negligible at low metal content (50 wt%) when the metal particles are completely embedded in the polymeric matrix. The H-2 storage capacity is comparable to that of the pure LaNi5 powders at high metal content (80 wt%) when a percolative distribution is assumed by the LaNi5 particles: this evidence points out the role of metal-metal interfaces and of interconnected metallic networks for H transport. (C) 2008 Elsevier Ltd. All rights reserved.