Fe3O4/FeNi3 heterojunction modified MgH2 as a high-performance hydrogen storage material: Catalytic mechanism and kinetic enhancement

Hydrogen is regarded as an attractive secondary energy carrier because of its high gravimetric energy density and environmentally benign conversion products. However, the practical application of hydrogen energy is still strongly limited by the lack of safe and efficient hydrogen storage materials. Among various solid-state hydrogen storage candidates, MgH 2 has attracted extensive attention due to its high theoretical hydrogen capacity, natural abundance, and low cost. Nevertheless, its practical use is hindered by high thermodynamic stability and sluggish hydrogen absorption/desorption kinetics. In this work, a rod-like Fe 3 O 4 /FeNi 3 heterointerface catalyst regulated by multivalent Mo and V species was synthesized via a one-step hydrothermal route followed by calcination, and its catalytic effect on the hydrogen storage behavior of MgH 2 was systematically investigated. The results show that the addition of the catalyst markedly improves the hydrogen sorption performance of MgH 2 . In particular, the MgH 2 + 5 wt% catalyst composite absorbs 5.70 wt% H 2 within 1 min and desorbs 6.52 wt% H 2 within 10 min at 593 K, indicating a substantial enhancement in sorption kinetics. Meanwhile, the onset dehydrogenation temperature is significantly reduced from 570 K for pristine MgH 2 to 463 K for the catalyst-containing sample, and the apparent dehydrogenation activation energy decreases from 132.66 to 69.85 kJ mol −1 H 2 . Structural and kinetic analyses suggest that the enhanced performance mainly originates from the synergistic effect of the Fe 3 O 4 /FeNi 3 heterointerface, which facilitates H 2 dissociation, interfacial hydrogen transfer, and Mg–H bond activation. The Mo/V species are considered to act primarily as electronic regulators at the surface/interface region rather than as separate bulk crystalline phases. This work provides useful insight into oxide-metal heterointerface engineering for improving the hydrogen storage properties of MgH 2 .