Remarkable hydrogen storage properties and mechanisms of the shell-core MgH2@carbon aerogel microspheres

Carbon aerogel (CA) microspheres with highly crumpled graphene-like sheets surface and network internal structure have been successfully prepared by an inverse emulsion polymerization routine, subsequently ball milled with Mg powder to fabricate Mg@CA. The Mg change into MgH2 phases, decorating on the surface of the CA forming MgH2@CA microspheres composite after the hydrogenation process at 400 °C. The MgH2@CA microspheres composite displays MgH2-CA shell-core structure and shows enhanced hydrogenation and dehydrogenation rates. It can quickly uptake 6.2 wt% H2 within 5 min at 275 °C and release 4.9 wt% H2 within 100 min at 350 °C, and the apparent activation energy for the dehydrogenation is decreased to 114.8 kJ mol−1. The enhanced sorption kinetics of the composite is attributed to the effects of the in situ formed MgH2 NPs during the hydrogenation process and the presence of CA. The nanosized MgH2 could reduce the hydrogen diffusion distance, and the CA provides the sites for nucleation and prevents the grains from agglomerating. This novel method of in situ producing MgH2 NPs on zero-dimensional architecture can offer a new horizon for obtaining high performance materials in the hydrogen energy storage field.