Dual Site Mo-Mg2Ni Catalyst Enhanced De/hydrogenation Kinetics in Magnesium with High Phase Stability

Abstract

The potential applications of magnesium hydride (MgH2) have hindered due to its sluggish reaction kinetics. While Mg2Ni phase drastically improves reactions rates, further enhancement of catalytic activity was limited due to relatively weak catalyst-hydrogen interactions. Here, we report the catalyst-hydrogen interaction strength of Mg2Ni can be systematically controlled by Mo-doping (Mo-Mg2Ni). The doped Mo sites are characterized by the higher d-band center than Ni and 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 the 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, achieving high cycling stability in Mo-Mg2Ni/MgH2 composite. These results demonstrate the effectiveness of heterometallic bonding in controlling the microstructure and chemical properties of intermetallic catalysts for Mg-based hydrogen storage materials.