In situ formation of highly dispersed LaH₃ and Mg₂Ni derived from 3DOM LaNiO₃ for the hydrogen storage kinetics enhancement of MgH₂

(3DOM) LaNiO₃ catalysts were successfully synthesized and significantly improved the hydrogen storage kinetics of MgH₂. MgH₂-5 wt% 3DOM LaNiO₃ can rapidly absorb 5.91 wt% H₂ at 175 °C within 500 s and desorb 6.37 wt% H₂ within 500 s at 300 °C, its hydrogen absorption and desorption rates are 10 and 11 times higher than MgH₂-5 wt% Nano LaNiO₃, respectively. This remarkable enhancement is primarily due to its unique 3DOM structure and the synergistic effect of highly dispersed LaH₃ and Mg₂Ni/Mg₂NiH₄ 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 Mg₂Ni/LaH₃ heterostructure can greatly reduce the hydrogen adsorption energy to −0.768 eV and the heterogeneous interface induces the charge redistribution between Mg₂Ni and LaH₃, resulting in a small amount of negative charge accumulating on the surface of Mg₂Ni. Moreover, highly dispersed LaH₃ and Mg₂Ni/Mg₂NiH₄ in the MgH₂ 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 LaH₃ and Mg₂Ni/Mg₂NiH₄ on MgH₂. 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 MgH₂.