MgH 2 is a promising solid–state hydrogen storage material. However, its high thermodynamics and sluggish kinetics hinder its practical application. Catalytic strategy is effective in improving its kinetic performance. Nevertheless, the highly efficient catalysts or additives are normally of low-yield in fabrication with high cost. In this work, a novel structural LaVO 4 fabricated by a low-cost method of spraying dry followed by a calcination is used as a catalytic additive for the hydrogen storage of MgH 2 . With an optimized addition of LaVO 4 , the overall hydrogen storage performances of MgH 2 are significantly improved. An onset dehydrogenation temperature of only 183°C is obtained after an initial activation of dehydrogenation and hydrogenation. The system can desorb 5.7 wt% H 2 at 250°C within 10 min and maintains a dehydrogenation capacity of 5.0 wt% H 2 after 50 cycles. It is found that LaVO 4 is transferred to lanthanum hydride and metallic vanadium in the initial dehydrogenation process, the former acts as a highly effective catalyst for the hydrogen storage of MgH 2 and the latter undergoes reversible hydrogenation and dehydrogenation in the subsequent cycles. The structural design of the catalyst and its scalable fabrication are highly valuable in realizing the practical application of catalytic strategy for the hydrogen storage of MgH 2 .
Yana Liu,Yu Zhu,Qinke Tang,Xinkang Shen,Yunfeng Zhu,Jiguang Zhang,Jun Wang,Zhixin Ba,Wenrong Cai,Yuting Huang,Xiaohui Hu
(3DOM) LaNiO 3 catalysts were successfully synthesized and significantly improved the hydrogen storage kinetics of MgH 2 . MgH 2 -5 wt% 3DOM LaNiO 3 can rapidly absorb 5.91 wt% H 2 at 175 °C within 500 s and desorb 6.37 wt% H 2 within 500 s at 300 °C, its hydrogen absorption and desorption rates are 10 and 11 times higher than MgH 2 -5 wt% Nano LaNiO 3 , respectively. This remarkable enhancement is primarily due to its unique 3DOM structure and the synergistic effect of highly dispersed LaH 3 and Mg 2 Ni/Mg 2 NiH 4 formed in situ during the ball milling and first de/re-hydrogenation process. 3DOM structure catalysts are fragile which can make the catalyst distribution more uniform during ball milling process, giving rise to the significantly improved catalytic activity. The theoretical calculation results show that Mg 2 Ni/LaH 3 heterostructure can greatly reduce the hydrogen adsorption energy to −0.768 eV and the heterogeneous interface induces the charge redistribution between Mg 2 Ni and LaH 3 , resulting in a small amount of negative charge accumulating on the surface of Mg 2 Ni. Moreover, highly dispersed LaH 3 and Mg 2 Ni/Mg 2 NiH 4 in the MgH 2 matrix create a multiphase interface, which can provide more active sites and a variety of pathways for hydrogen diffusion. Above reasons contribute to the excellent synergistic catalytic performance of in situ formed LaH 3 and Mg 2 Ni/Mg 2 NiH 4 on MgH 2 . These discoveries hold scientific value for the design and preparation of highly active catalysts using 3DOM materials for hydrogen storage in light-metal hydrides, especially in MgH 2 .
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