Hydrogen sorption properties of magnesium particles decorated with metallic nanoparticles as catalyst

Both hydrogen absorption and desorption, in the range 200-300 and 260-330 degrees C, respectively, of magnesium particles decorated with metallic nanoplots elaborated by Supercritical Fluid Chemical process are studied. The absorption data are fitted using Avrami-Erofeev model to first order. Unexpectively, magnesium decorated with copper nanoparticles lead to relatively high rates of sorption (absorption rate at 300 degrees C and desorption rate at 330 degrees C of about 0.4wt%H min(-1)) but its activation energy remains high (similar to 70 kJ mol(-1)). The presence at the interface of MgCu2, acting as a chemical link between the nanoCu and the magnesium particle could be responsible for such behavior. Palladium nanoparticles react with magnesium during cycling so that the catalytic effect is decreasing with cycling and finally does not exist anymore after 10 cycles. Finally, the best results are obtained for the nanocomposite of magnesium with nickel nanoparticles for which the sorption rates are comparable with the ones obtained for optimized BM samples with catalysts, but with a lower energy cost of the process. (C) 2008 Elsevier B.V. All rights reserved.