Magnesium-based hydrogen storage materials (MgH₂) are promising hydrogen carrier due to the high gravimetric hydrogen density; however, the undesirable thermodynamic stability and slow kinetics restrict its utilization. In this work, we assist the de/hydrogenation of MgH₂ via in situ formed additives from the conversion of an MgNi₂ alloy upon de/hydrogenation. The MgH₂–16.7 wt%MgNi₂ composite was synthesized by ball milling of Mg powder and MgNi₂ alloy followed by a hydrogen combustion synthesis method, where most of the Mg converted to MgH₂, and the others reacted with the MgNi₂ generating Mg₂NiH₄, which produced in situ Mg₂Ni during dehydrogenation. Results showed that the Mg₂Ni and Mg₂NiH₄ could induce hydrogen absorption and desorption of the MgH₂, that it absorbed 2.5 wt% H₂ at 473 K, much higher than that of pure Mg, and the dehydrogenation capacity increased by 2.6 wt% at 573 K. Besides, the initial dehydrogenation temperature of the composite under the promotion of Mg₂NiH₄ decreased greatly by 100 K, whereas it is 623 K for MgH₂. Furthermore, benefiting from the catalyst effect of Mg₂NiH₄ during dehydrogenation, the apparent activation energy of the composite reduced to 73.2 kJ mol⁻¹ H₂ from 129.5 kJ mol⁻¹ H₂.

镁基储氢材料（MgH ₂）由于具有很高的重量氢密度，因此有望成为氢的载体。但是，不良的热力学稳定性和缓慢的动力学限制了其利用。在这项工作中，我们通过原位形成的添加剂通过MgNi ₂合金在脱氢后的转化来协助MgH ₂ 脱氢。MgH ₂ -16.7 wt％MgNi ₂复合材料是通过对Mg粉末和MgNi ₂合金进行球磨，然后通过氢燃烧合成法合成的，其中大部分Mg转化为MgH ₂，其他与MgNi ₂反应生成Mg ₂NiH ₄，在脱氢过程中原位生成Mg ₂ Ni。结果表明，Mg ₂ Ni和Mg ₂ NiH ₄可以诱导MgH ₂吸收和解吸氢，在473 K下吸收了2.5 wt％的H ₂，远高于纯Mg，脱氢能力提高了2.6另外，在Mg ₂ NiH ₄的促进下，复合材料的初始脱氢温度下降了100 K，而MgH ₂为623K 。此外，得益于Mg ₂ NiH _4的催化作用脱氢过程中，该复合材料的表观活化能降低到73.2千焦摩尔^-1 ħ ₂从129.5千焦摩尔^-1 ħ ₂。