A First‐Principles Study on the Synergistic Enhancement of HER Catalytic Performance of g‐C 3 N 4 by P Doping and N Vacancy Modification

Density functional theory (DFT) calculations were performed to investigate the synergistic enhancement mechanism of P doping and N vacancy modification on the hydrogen evolution reaction (HER) catalytic performance of g‐C 3 N 4 . Single modification offers only limited improvement in HER activity. The combination of P doping and N vacancy exhibits a synergistic effect. This synergy tunes the hydrogen adsorption free energy to ΔG H* = 0.05 eV, comparable to that of Pt(111) (ΔG H* = −0.09 eV). Electronic structure and charge analysis reveal the electron‐rich region from P doping and the electron‐deficient region from N vacancy undergo charge compensation. This process regulates the C 2p band center at the active site and balances the hydrogen adsorption‐desorption. The synergistic system narrows the bandgap and reduces the carrier effective mass. The H* diffusion barrier decreases to 0.42 eV, and the theoretical overpotential reaches 0.18 V, indicating a substantial improvement in kinetic performance. Phonon spectrum calculations show no imaginary frequencies, confirming dynamic stability of the system. Ab initio molecular dynamics (AIMD) simulations verify that the structure remains stable at 300 K and 500 K. This work provides a reliable theoretical foundation for designing efficient non‐metal catalysts for the hydrogen evolution reaction via water electrolysis.