Enhancement of the Hydrogen-Storage Properties of MgH2 by the Addition of Ni, NaAlH4, Ti, and CNT via Reactive Mechanical Grinding

MgH2 was used as the starting material in this study. A sample with the composition of 84 wt% MgH2 + 10 wt% Ni + 2 wt% NaAlH4+ 2 wt% Ti + 2 wt% CNT (named MgH2-10Ni-2NaAlH(4)-2Ti-2CNT) was prepared by the reactive mechanical grinding. Hydriding and dehydriding property measurements, X-ray diffraction (XRD) analyses, and microstructural observations were then performed. The activation of the sample was not required. At the first cycle (n = 1), the sample absorbed 2.84 wt% H for 5 min, 3.75 wt% H for 10 min, 4.09 wt% H for 15 min, and 4.17 wt% H for 60 min at 593 K under 12 bar H-2. The MgH2-10Ni-2NaAlH(4)-2Ti-2CNT sample showed quite a high hydriding rate at a relatively low temperature of 423 K under 12 bar H-2 (at n = 4), absorbing 2.81 wt% H for 5 min, 3.23 wt% H for 10 min, and 3.56 wt% H for 60 min. The reactive mechanical grinding of MgH2 with Ni, NaAlH4, Ti, and CNT is considered to create defects on the surface and in the interior of MgH2 as well as decrease the particle size of MgH2.