Ni-based catalyst assisted by MnO to boost the hydrogen storage performance of magnesium hydride

Abstract

Magnesium hydride (MgH2) stands out as a promising solid-state material for high-density hydrogen storage, offering enormous potential for applications in hydrogen transportation and storage. However, the stable thermodynamics and sluggish kinetics of dehydrogenation/hydrogenation of MgH2 impede its practical use in on-board hydrogen storage. In this study, the nanocomposite of nickel/manganese oxide (Ni/MnO) was successfully synthesized through the hydrogenation of nickel-manganese two-dimensional layered double hydroxide (NiMn-LDH) and then introduced into MgH2 by ball milling to form BM-MgH2-Ni/MnO composite. Notably, BM-MgH2-Ni/MnO-10 displayed excellent hydrogen absorption/dehydrogenation properties. For example, its onset hydrogen release temperature was remarkably reduced to 175.6 °C, 84 °C lower than that of BM-MgH2. At a temperature of 250 °C, it could desorb about 6.2 wt% of H2 within 60 min. The fully dehydrogenated product could absorb 5.5 wt% of H2 within 10 min at 150 °C. Moreover, BM-MgH2-Ni/MnO-10 exhibited excellent cycling performance. Throughout the cycling process, the in-situ formation of Mg2Ni/Mg2NiH4 and metal Mn was detected, leading to a synergistic effect that significantly enhanced the hydrogen storage capability of MgH2. This study presents innovative concepts for designing active catalysts to enhance the kinetics of de-/hydrogenation reactions of MgH2.