Extra C-doping induced shallower defect states in g-C₃N₄ with maximized photocarrier transfer benefits toward H₂ evolution

Defect control is acknowledged as an ‘all-in-one’ approach to enhance g-C₃N₄ photocatalytic performance, yet improper defect modulation inevitably compromises charge transfer benefits. Herein, we developed a dual-solvent-assisted strategy to incorporate extra C into defective g-C₃N₄ with pre-existing N vacancies and S dopants (CN-300ES), rendering the shallower defect states with maximized photocarrier transfer behaviors. Compared to g-C₃N₄ without extra C dopants, CN-300ES exhibited a defect-states-elevation by 0.24 eV and faster charge transfer kinetics with an average lifetime (τ_ave) of only 13.23 ps. Notably, extra C is critical to induce an optimized electron-trapping ability of shallower defect states, as revealed by the lower ratio of deeply trapped electrons of only 6.46% with a significantly reduced τ₃ of 188.59 ps. Furthermore, theoretical calculations elucidated that both the asymmetrical distributions of charge density for HOMO/LUMO and boosted electronic polarized field aroused by C dopants contributed to the maximized photocarrier separation and charge transfer dynamics, which might be the root of the benefits of shallower defect states. Therefore, CN-300ES delivered an excellent solar-driven H₂ evolution performance at around 11 513.7 μmol g⁻¹ h⁻¹, far exceeding pristine g-C₃N₄ and CN-ES, which paves a new insight into the maximization of photocarrier transfer behaviors via designing shallower defect states.