Highly enhanced hydrogen energy storage of MgH2 catalyzed by Ni/CeVO4-x@NC

A novel catalyst of Ni/CeVO 4- x @NC (nano carbon) was prepared via the coprecipitation-reduction method and then ball-milled with MgH 2 . During the precipitation process, elemental Ni was formed in situ. The catalyst was characterized to have a multiphase structure, with CeVO 3 as the main phase coexisting with the CeVO 4 phase; the latter contains abundant oxygen vacancies (denoted as CeVO 4- x ). Oxygen vacancy defects facilitate the efficient dissociation of MgH 2 and exert a synergistic catalytic effect with metallic Ni, as well as multivalent Ce and V species. The MgH 2 + 4 wt% Ni/CeVO 4- x @NC composite absorbs 5.36 wt% H 2 within 2 min at 553 K and releases 5.71 wt% H 2 within 78 min. This composite exhibits an initial hydrogen desorption temperature of 465 K, which contributes to the reduction of MgH 2 's thermodynamic stability. First-principles calculations were performed on the MgH 2  + Ni/CeVO 3 @NC model, encompassing the states of the composite both before and after hydrogen absorption and desorption. It was found that the introduction of metallic Ni provides additional quantum states and active sites for electron migration, thereby enhancing the electron transfer capability of the composite surface.