An experimental and theoretical investigation of the enhanced effect of Ni atom-functionalized MXene composite on the mechanism for hydrogen storage performance in MgH2

Abstract

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.