Hydrogen Storage Capabilities Enhancement of MgH2 Nanocrystals

The limited practical application of commercial MgH2 is hindered by its sluggish hydrogen absorption and desorption kinetics. In this paper, MgH2 particles with smaller sizes were successfully prepared by mechanical ball milling, and the microstructure of ball-milled MgH2 was analyzed by XRD, SEM, and TEM. The addition of ball milling energy increases the surface energy of the material and the fracture of the Mg–H bond. As a result, the surface activation energy of the material is reduced. Furthermore, extending the milling duration results in a notable expansion of the nanocrystalline domains present on the surface of MgH2 powder. At 613 K, the MgH2 ball milled for 15 h can absorb 5.512 wt% H2 in 7.8 min, and it takes 75 min to release 5.124 wt% H2 and its dehydrogenation activation energy is reduced from 136.0 to 126.69 kJ/mol H2. The initial dehydrogenation temperature of the MgH2 sample milled for 15 h was 81 K lower than that of the original MgH2 sample, and the initial dehydrogenation temperature was only 447 K. This work can provide theoretical guidance for the use value of commercial MgH2.