Hydrogen storage performance of MgH2 under catalysis by highly dispersed nickel-nanoparticle–doped hollow spherical vanadium nitride

Abstract

Magnesium hydride (MgH₂) is an exceptional material for hydrogen storage, but its high desorption temperature and slow kinetics limit its applicability. In this study, the hydrogen storage performance of MgH₂ was enhanced using highly dispersed Ni-nanoparticle–doped hollow spherical vanadium nitride (Ni/VN), which was synthesized via a solvothermal process. The MgH₂ system doped with the synthesized Ni/VN exhibited an outstanding hydrogen-storage capability. Specifically, 5.6 wt.% of H₂ was released within 1 h at a relatively low temperature of 513 K, whereas 6.4 wt.% of H₂ was released within 180 s at 598 K, followed by an almost complete dehydrogenation after 10 min at 598 K. At 423 K, the developed material absorbed ∼6.0 wt.% of H₂ within 5 min. The activation energy for dehydrogenation was determined to be 78.07 ± 2.91 kJ·mol⁻¹, which was considerably lower than that of MgH₂ produced by ball milling (120.89 ± 5.74 kJ·mol⁻¹), corresponding to a reduction of 35.4%. It was deduced that the formation of Mg₂Ni/Mg₂NiH₄ (hydrogen pump) through the reaction of Ni nanoparticles during dehydrogenation/hydrogenation facilitated hydrogen transport and synergistically catalyzed hydrogen absorption and desorption by MgH₂, improving its hydrogen storage capability. These findings offer novel perspectives for the utilization of MgH₂ in large-scale applications.