Oxide-precatalyst Fe3O4/leaf-carbon enabling in-situ Fe/MgO interfaces for low-temperature and reversible hydrogen storage in MgH2

Developing efficient and scalable catalysts remains crucial for advancing practical MgH 2 -based solid-state hydrogen storage. In this work, an oxide-precatalyst strategy is proposed, where Fe 3 O 4 nanoparticles are uniformly anchored on leaf-derived porous carbon to form a Fe 3 O 4 /leaf-carbon catalyst that converts in situ into highly dispersed Fe/MgO interfaces during the initial dehydrogenation process. The resultant MgH 2 + 10 wt% Fe 3 O 4 /leaf-carbon composite exhibits a markedly improved hydrogen sorption performance, with an onset desorption temperature of 215 °C, releasing 6.41 wt% H 2 within 8 min at 350 °C, and reabsorbing 6.22 wt% H 2 at 175 °C (3 MPa) within 1 h. Notably, the activation energies for hydrogenation and dehydrogenation are drastically reduced to 53.27 kJ mol −1 and 91.45 kJ mol −1 , respectively. Furthermore, after undergoing 20 consecutive adsorption cycles, this composite material still maintained 96.3 % of its hydrogen storage capacity compared to the initial hydrogen absorption. Structural characterizations confirm that Fe 3 O 4 is reduced to Fe while forming a stable Fe/MgO heterointerface that provides abundant active sites and accelerates hydrogen diffusion. This study elucidates the oxide-to-metal interface transformation mechanism as an effective pathway to simultaneously lower thermodynamic barriers and enhance kinetic reversibility, offering a cost-effective and sustainable strategy for engineering next-generation MgH 2 -based hydrogen storage materials.