Improving MgH 2 formation kinetics and its effect on NaBH 4 synthesis

Abstract

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 NaBH 4, an attractive hydrogen source with 10.6 wt% hydrogen content. In this study, the MgH 2 formation kinetics in pure Mg and Mg–23.5 wt% Ni was studied and correlated with NaBH 4 synthesis kinetics. It was found that the hydriding kinetics of Mg–23.5 wt% Ni was significantly improved owing to the fine laminar Mg/Mg 2Ni structure. Ballmilling and surface treatment made the eutectic alloy absorb 2.0 wt% hydrogen at 353 K. When these materials were applied for the NaBH 4 synthesis, it was found that the eutectic Mg–Ni alloy enhanced the NaBH 4 formation kinetics at high temperatures. However, NaBH 4 was not produced at 353 K although MgH 2 could be formed.