Enhancing hydrogen storage performances of MgH ₂ by Ni nano-particles over mesoporous carbon CMK-3

Abstract Nano-dispersed Ni particles over mesoporous carbon material CMK-3 (Ni/CMK-3) was fabricated by means of impregnation-reduction strategy using precursor NiCl 2 · 6H 2 O, which is beneficial to improving the de/rehydrogenation performances of MgH 2 . The dehydrogenation onset temperature of MgH 2 –Ni/CMK-3 is significantly lowered by 170 K from that of pristine MgH 2 (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 H 2 . Activation energy values of both dehydrogenation (43.4 kJ mol −1 ) and rehydrogenation (37.4 kJ mol −1 ) for MgH 2 –Ni/CMK-3 are greatly enhanced from those of as-milled MgH 2 . Ni/CMK-3 also slightly destabilizes the dehydrogenation of MgH 2 by 1.5 kJ mol <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mo>.</mml:mo> </mml:math> The enhanced performances can be attributed to the synergistic effects of both destabilization and activation from nano-dispersed Ni particles.

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