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.