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

• MXene supported Ultrafine single-atom nickel (Ni@Nb 2 C)nanocomposites was prepared. • The addition of Ni can enhance the catalytic activity of Nb 2 C. • Ni@Nb 2 C reduces the hydrogen uptake/release temperature of MgH 2 . • The Ni@Nb 2 C-doped MgH 2 composite exhibits excellent hydrogen storage kinetics. The deposition of ultrafine single-atom nickel particles on Nb 2 C (MXene) was successfully achieved using a wet chemistry method to synthesize Ni@Nb 2 C composite. This study explored the effect of Ni@Nb 2 C on the hydrogen absorption and desorption properties of MgH 2 through theoretical calculations and experimental investigations. Under the catalytic action of Ni@Nb 2 C, the initial dehydrogenation temperature of MgH 2 was reduced by 121°C, with approximately 4.26 wt.% of H 2 desorbed at 225°C in 100 min. The dehydrogenation activation energy of the MgH 2 + Ni@Nb 2 C composite dropped to 86.7 kJ·mol −1 , a reduction of 60.5 kJ·mol −1 compared to pure MgH 2 . Density functional theory calculations indicated that the incorporation of Ni@Nb 2 C enhanced the performance of MgH 2 performance by improving interactions among Nb 2 C, Ni, Mg, and H atoms. In the Ni@Nb 2 C + MgH 2 system, the lengths of Mg-H bonds (1.91–1.99 Å) were found to be longer than those observed in pure MgH 2 (1.71 Å). The dehydrogenation energy for this system (1.08 eV) was lower than that for Nb 2 C (1.52 eV). These findings suggest that the synergistic effect of Ni and Nb 2 C significantly enhances the hydrogenation/dehydrogenation kinetics of MgH 2 , thereby introducing a novel approach for catalytic modification of solid hydrogen storage materials through synergistic actions.