LaVO4 prepared by a high–yield method for superior catalysis to the hydrogen storage of MgH2

Abstract

MgH₂ 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 LaVO₄ fabricated by a low-cost method of spraying dry followed by a calcination is used as a catalytic additive for the hydrogen storage of MgH₂. With an optimized addition of LaVO₄, the overall hydrogen storage performances of MgH₂ 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% H₂ at 250°C within 10 min and maintains a dehydrogenation capacity of 5.0 wt% H₂ after 50 cycles. It is found that LaVO₄ 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 MgH₂ 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 MgH₂.