H2 storage efficiency and sorption kinetics in composite materials

We have prepared two different kinds of composite materials for hydrogen storage and studied their H2 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 H2 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 μm) distributed in a polymeric matrix. The H2 storage capacity is negligible at low metal content (50 wt%) when the metal particles are completely embedded in the polymeric matrix. The H2 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.