Synthesis Of Anti-perovskite Materials And Their Effection On Hydrogen Storage Properties Of MgH₂

The Mg-based hydrogen storage materials are considered to be one of the most promising solid-state hydrogen storage materials,however,the high thermodynamic stability and slow hydrogen absorption and desorption kinetics have become major obstacles in their practical applications.Doping additives is an effective method to improve the hydrogen storage properties of Mg-based hydrogen storage materials.In this paper,three kinds of anti-perovskite materials(MgCNi₃/MgC_0.5Co₃/MgCCo_1.5Ni_1.5)were prepared by powder metallurgy,next,the corresponding composites were prepared by ball-milling and hydriding combustion synthesis method by using the prepared different anti-perovskite materials and Mg powder as raw materials,the Mg–MgCNi₃,Mg–MgC_0.5Co₃ and Mg–MgCCo_1.5Ni_1.5 composites are included.And we also deeply studied the comprehensive properties of the composites and discussed the mechanism of action for different additive materials in the composite system.The results showed that the initial hydrogen desorption temperature of Mg–MgCNi₃,Mg–MgC_0.5Co₃ and Mg–MgCCo_1.5Ni_1.5 composites are lower than pure MgH₂ under the same conditions,by about 131 K,140 K and 160 K,respectively.In the composite system,the Mg–MgCNi₃ and Mg–MgCCo_1.5Ni_1.5 composites exhibit excellent hydrogen absorption capacity at low temperatures with the hydrogen absorption capacity of more than 4 wt%and 5.0 wt%hydrogen at 423 K.Even at 373 K,the Mg–MgCCo_1.5Ni_1.5composite can still reach the hydrogen absorption capacity of 4 wt%hydrogen.The all composites were prepared can still reach 98.0%hydrogen absorption capacity retention rate after 10 cycles in this paper.In addition,the activation energies of the three composites decreased to varying degrees,especially the activation energy of the Mg–MgCCo_1.5Ni_1.5 composite was reduced to 39.6 kJ/mol.The characterization results show in the process of hydrogen absorption of Mg–MgCNi₃ composite.The Mg₂NiH₄ and carbon materials were formed where the Mg₂NiH₄induced dehydrogenation of MgH₂ and carbon played a dispersive role during the composite reaction.Both features synergistically benefited the hydrogen storage properties of MgH₂.During the reaction,we found the MgC_0.5Co₃ material does not undergo chemical changes.But in the reaction,the MgC_0.5Co₃ can provide active sites for MgH₂particle attachment and provide a channel for diffusion of hydrogen atoms,which has a catalytic effect of the hydrogen desorption of MgH₂.The MgCCo_1.5Ni_1.5 materail combines the effects of the above two additives,which makes the Mg–MgCCo_1.5Ni_1.5composite exhibit better hydrogen storage properties.