Improved hydrogen storage properties of MgH by nickel@nitrogen-doped carbon spheres.

Magnesium hydride is considered to be one of the most desirable hydrogen storage materials due to its high weight capacity (7.6 wt% H) and low price. However, its relatively high operating temperatures and slow dynamics have always hampered its commercial applications. In this paper, nano-nickel particle coated nitrogen-doped carbon spheres (Ni@NCS) were synthesized by a chemical reduction method and then introduced into Mg to form an MgH-Ni@NCS composite via hydriding combustion and subsequent high-energy ball milling processes. The results showed that the MgH-Ni@NCS composite possessed high hydrogen storage capacity and fast absorbing/desorbing kinetics, absorbing 5.7 wt% H and desorbing 4.3 wt% H within 8 min at 623 K. Moreover, the capacity shows negligible degradation after 10 cycles, indicating that the MgH-Ni@NCS composite has good cycling stability. Even at relatively low temperature (373 K), the MgH-Ni@NCS composite still absorbed 4.2 wt% H within 60 min compared to 0.9 wt% H for milled MgH. The improvement in hydrogen storage properties is ascribed to the in situ formed MgNiH induced dehydrogenation of MgH and effective prevention of the agglomeration of magnesium during the hydriding/dehydriding reaction by the carbon material.