The deposition of ultrafine single-atom nickel particles on Nb₂C (MXene) was successfully achieved using a wet chemistry method to synthesize Ni@Nb₂C composite. This study explored the effect of Ni@Nb₂C on the hydrogen absorption and desorption properties of MgH₂ through theoretical calculations and experimental investigations. Under the catalytic action of Ni@Nb₂C, the initial dehydrogenation temperature of MgH₂ was reduced by 121°C, with approximately 4.26 wt.% of H₂ desorbed at 225°C in 100 min. The dehydrogenation activation energy of the MgH₂ + Ni@Nb₂C composite dropped to 86.7 kJ·mol⁻¹, a reduction of 60.5 kJ·mol⁻¹ compared to pure MgH₂. Density functional theory calculations indicated that the incorporation of Ni@Nb₂C enhanced the performance of MgH₂ performance by improving interactions among Nb₂C, Ni, Mg, and H atoms. In the Ni@Nb₂C + MgH₂ system, the lengths of Mg-H bonds (1.91–1.99 Å) were found to be longer than those observed in pure MgH₂ (1.71 Å). The dehydrogenation energy for this system (1.08 eV) was lower than that for Nb₂C (1.52 eV). These findings suggest that the synergistic effect of Ni and Nb₂C significantly enhances the hydrogenation/dehydrogenation kinetics of MgH₂, thereby introducing a novel approach for catalytic modification of solid hydrogen storage materials through synergistic actions.

Carbon materials have excellent catalytic effects on the hydrogen storage performance of MgH₂. Here, carbon-supported Ni₃S₂ (denoted as Ni₃S₂@C) was synthesized by a facile chemical route using ion exchange resin and nickel acetate tetrahydrate as raw materials and then introduced to improve the hydrogen storage properties of MgH₂. The results indicated the addition of 10wt.% Ni₃S₂@C prepared by macroporous ion exchange resin can effectively improve the hydrogenation/dehydrogenation kinetic properties of MgH₂. At 100 ℃, the dehydrogenated MgH₂-Ni₃S₂@C-4 composite could absorb 5.68wt.% H₂. Additionally, the rehydrogenated MgH₂-Ni₃S₂@C-4 sample could release 6.35wt.% H₂ at 275 ℃. The dehydrogenation/hydrogenation enthalpy changes of MgH₂-Ni₃S₂@C-4 were calculated to be 78.5 kJ mol⁻¹/−74.7 kJ mol⁻¹, i.e., 11.0 kJ mol⁻¹/7.3 kJ mol⁻¹ lower than those of MgH₂. The improvement in the kinetic properties of MgH₂ was ascribed to the multi-phase catalytic action of C, Mg₂Ni, and MgS, which were formed by the reaction between Ni₃S₂ contained in the Ni₃S₂@C catalyst and Mg during the first hydrogen absorption–desorption process.