Achieving Ambient-Temperature Fast Hydrogenation Properties in Ga-Doped Mg–Ni Alloy: Dual-Phase Synergistic Catalysis and Stacking Fault Channels

The high operating temperatures and sluggish kinetics of Mg-based hydrogen storage materials (HSMs) are urgently being addressed. In this work, a novel Mg–Ni–Ga HSM with dual-phase synergistic catalysis is developed, including the fishbone-like Mg₃Ni₂Ga₁ catalytic phase and the Mg₂Ni phase with stacking faults (SFs). The spheroidization of Mg grains is inhibited by the pinning effect of the Mg₃Ni₂Ga₁ phase, and the high-energy Mg grain boundaries are obtained. High-density SFs are induced in the Mg₂Ni phase via Ga dissolution. It is worth noting that Mg_94.5Ni₅Ga_0.5 alloy absorbs 0.37 wt% H₂ merely at 25°C, and absorbs 2.71 wt% H₂ at 150°C under even 0.1 MPa. The dehydrogenation activation energy is significantly decreased from 81.86 kJ mol⁻¹ in Mg₉₅Ni₅ alloy to 67.68 kJ mol⁻¹. The room temperature and low-pressure hydrogenation performance are achieved through these multiphase synergistic catalysis: H₂ molecule dissociation facilitated by the Mg₃Ni₂Ga₁ phase, hydride nucleation promoted by high-energy Mg grain boundaries, additional rapid diffusion channels for H atoms, and the enhanced “hydrogen pump” effect provided by the Mg₂Ni phase with SFs structure.