Hydrogen storage properties of core-shell structured Mg@TM (TM = 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 (Delta H-abs = 70.02 kJ/mol H-2) and activation energy (E-a = 67.66 kJ/mol H-2) 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 degrees C, about 60 degrees 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 Mg Co hydrides (Mg2CoH5&Mg3CoH5) acting as hydrogen pump and V2H accelerating the dissociation of H-2 might also contribute to the improved hydrogen sorption properties of Mg. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.