A dual-site Mo–Mg2Ni catalyst enhances de/hydrogenation kinetics of magnesium with high phase stability

Abstract

Potential applications of magnesium hydride (MgH₂) have been hindered due to its sluggish reaction kinetics. While the Mg₂Ni phase shows drastically improved reaction rates, further enhancement of catalytic activity has been limited due to relatively weak catalyst–hydrogen interactions. Here, we report that the catalyst–hydrogen interaction strength of Mg₂Ni can be systematically controlled by Mo-doping (Mo–Mg₂Ni). The doped Mo sites are characterized by a higher d-band center than Ni, and they efficiently accelerate hydrogen adsorption and dissociation processes. As a result, the Mo–Mg₂Ni/MgH₂ composite releases 6.03 wt% H₂ within 5 min at 300 °C and 4.73 wt% H₂ within 25 min at 240 °C, with an activation energy of 96.11 kJ mol⁻¹. This performance is 2–3 times higher than that of pure Mg₂Ni-catalyzed MgH₂. The chemical and morphological properties of Mo–Mg₂Ni remain largely unchanged before and after reactions, with high cycling stability achieved in the Mo–Mg₂Ni/MgH₂ composite. These results demonstrate the effectiveness of heterometallic bonding for controlling the microstructure and chemical properties of intermetallic catalysts for Mg-based hydrogen storage materials.