Synthesis and hydrogen storage behavior of Mg-Co-H system at nanometer scale

There are few reports on the hydrogen storage behavior study of Mg-Co-H system in the literature, although Mg2CoH5 has a much higher hydrogen capacity than Mg2NiH4. This is due to the great difficulty in the synthesis of Mg2CoH5 and Mg2Co in convenient conditions. Here we successfully synthesized the nanostructured Mg2CoH5 and Mg2CO from Mg and Co nanoparticles prepared by hydrogen plasma-metal reaction method. The reaction mechanism of the synthesis of the Mg-Co-H system was studied. The morphology of the Mg-Co-H system in nanometer scale was observed. The hydrogen absorption curves and the pressure-composition isotherm (P-C-T) properties of the Mg-Co-H system were studied. The van't Hoff equations and the formation enthalpies and entropies of the produced Mg2CoH5 and Mg3CoH5 were obtained. The results were discussed by comparing with the corresponding ones of Mg-Co-H system by other groups and the ones of nanostructured Mg-H and Mg-Ni-H systems by our group. (C) 2004 Published by Elsevier Inc.