Enhanced hydrogen storage kinetics of magnesium hydride enabled by graphene-supported Pd–Ni bimetallic nanocatalysts

To address the sluggish hydrogen sorption kinetics of MgH₂, a novel Mg-PdNi@rGN composite is prepared by integrating graphene nanosheet–supported Pd-Ni bimetallic catalysts via a combined hydriding combustion synthesis (HCS) and mechanical milling (MM) strategy. The composite exhibits exceptional hydrogen storage performance, with a dehydriding onset temperature of ~140 °C and a peak desorption of 256.9 °C (94.7 °C lower than pure Mg), and an activation energy of only 70.5 kJ mol^-1. Remarkably, the composite achieves 6.46 wt% hydrogen uptake within 100 s at 100 °C and releases 6.70 wt% H₂ in 400 s at 300 °C, maintaining 98.95% capacity retention after 15 cycles. First-principles calculations elucidate that the PdNi nanocatslyst induces interfacial electron redistribution, effectively weakening Mg-H bonding. Complementary experimental characterizations reveal that the in-situ formed Mg₂NiH₄ and MgPd phases serve as efficient hydrogen transport channels, while the graphene matrix simultaneously enhances thermal/electrical conductivity and suppresses particle agglomeration. This work establishes a new paradigm for the rational design of high-performance Mg-based hydrogen storage materials through the synergistic coupling of bimetallic catalysts with two-dimensional carbon supports.