• DFT calculations reveal that transition metal (Ti, Ni, Zr, Nb) modification of V2C MXene improves MgH2 adsorption and lowers dehydrogenation energy.
• Ni@V2C shows the highest adsorption energy and the greatest reduction in dehydrogenation energy (by 1.60 eV compared to pure MgH2).
• Orbital hybridization between H and TM atoms enhances electronic interactions and catalytic activity.
• TM@V2C combinations offer a promising catalyst design for experimentally improving MgH2 hydrogen storage performance.