Improving MgH2 formation kinetics and its effect on NaBH4 synthesis

Mg and Mg-based alloys are not only promising hydrogen storage materials due to their high storage capacities, but also potential reducing agents in the synthesis of sodium borohydride NaBH4, an attractive hydrogen source with 10.6 wt% hydrogen content. In this study, the MgH2 formation kinetics in pure Mg and Mg–23.5 wt% Ni was studied and correlated with NaBH4 synthesis kinetics. It was found that the hydriding kinetics of Mg–23.5 wt% Ni was significantly improved owing to the fine laminar Mg/Mg2Ni structure. Ballmilling and surface treatment made the eutectic alloy absorb 2.0 wt% hydrogen at 353 K. When these materials were applied for the NaBH4 synthesis, it was found that the eutectic Mg–Ni alloy enhanced the NaBH4 formation kinetics at high temperatures. However, NaBH4 was not produced at 353 K although MgH2 could be formed.