Enhancing hydrogen storage performances of MgH₂ by Ni nano-particles over mesoporous carbon CMK-3

Nano-dispersed Ni particles over mesoporous carbon material CMK-3 (Ni/CMK-3) was fabricated by means of impregnation-reduction strategy using precursor NiCl₂ · 6H₂O, which is beneficial to improving the de/rehydrogenation performances of MgH₂. The dehydrogenation onset temperature of MgH₂–Ni/CMK-3 is significantly lowered by 170 K from that of pristine MgH₂ (around 603 K). Totally 5.9 wt% of hydrogen absorption capacity is liberated within 1 h at a temperature of 423 K under a pressure of 3 MPa. This composite can absorb 3.9 wt% hydrogen even at a temperature of 328 K under 3 MPa H₂. Activation energy values of both dehydrogenation (43.4 kJ mol⁻¹) and rehydrogenation (37.4 kJ mol⁻¹) for MgH₂–Ni/CMK-3 are greatly enhanced from those of as-milled MgH₂. Ni/CMK-3 also slightly destabilizes the dehydrogenation of MgH₂ by 1.5 kJ mol ${H_2}^{-1}.$ The enhanced performances can be attributed to the synergistic effects of both destabilization and activation from nano-dispersed Ni particles. (paper)