H−/e– cooperative transport mechanism for carbon supported nano hydrogen pump in MgH2

MgH2 is a promising solid hydrogen storage material, but its commercial application is limited by the poor de-/hydriding kinetics. The commonly used modification method involves first prepare the catalyst and then ball milling it with MgH2. Herein, a composite of MgH2 with in situ carbon-supported catalyst was prepared via flexible solid reaction based on cost-effective metal carbonates as precursors. Uniformly distributed Ni nanoparticles (2–5 nm) as the actively catalytic sites are attached through in situ carbon capsule to construct an efficient catalytic network. Such well-designed structure enables MgH2 with high hydrogenation capacity (4.7 wt% at 40 °C) and low dehydrogenation temperature (start as low as 180 °C). Further mechanism study reveals the nano-Mg2Ni with stronger hydrogen pump effect exhibits remarkable transmittability of H− ions and the optimized transport path by carbon capsule layer enhances the electrons transmittability, which eventually accelerates the redox reaction process of de-/hydriding. This work not only significantly improves the hydrogen storage performance of MgH2 through a one-step modification method, but also provides new insights into the catalytic mechanism of hydrogen storage materials from the perspective of ions/electrons transmittability.