Hydrogen storage properties of core-shell structured Mg@TM (TMÂ =Â Co, V) composites

Target improving the hydrogen sorption properties of Mg, core-shell structured Mg@TM (TM = Co, V) composites were synthesized via an approach combining arc plasma method and electroless plating. The core-shell structures with the MgH2 core and V or Co containing hydride shells for hydrogenated Mg@TM particles were observed through HAADF-STEM and HRTEM techniques. The measured hydrogenation enthalpy (ΔHabs = −70.02 kJ/mol H2) and activation energy (Ea = 67.66 kJ/mol H2) of the ternary Mg@Co@V composite were lower than those of binary composites and the pure Mg powder. In addition, the onset dehydrogenation temperature for the hydrogenated ternary composite measured from DSC was 323 °C, about 60 °C lower than that of pure MgH2. On one hand, these improved properties can be attributed to the core-shell structure which may introduce more contacts between catalysts and Mg, thus providing more nucleation sites for hydrogen sorption. On the other hand, the co-effect of MgCo hydrides (Mg2CoH5&Mg3CoH5) acting as “hydrogen pump” and V2H accelerating the dissociation of H2 might also contribute to the improved hydrogen sorption properties of Mg.