Unraveling the Dual-Capture Strategy in Surface-Grafted −NH2 on N-Defected g-C3N5 for Enhanced Photocatalytic Hydrogen Production

N-rich carbon nitride (g-C3N5) became a promising photocatalyst due to its narrower band gap, larger π-conjugate network, and better visible light responsive hydrogen precipitation activity compared with g-C3N4. However, the inherent shortcomings still limited the development of g-C3N5. To reasonably address this issue, N defects and surface amino groups were successfully introduced into pristine g-C3N5 through facile one-step calcination. Systematical characterizations and theoretical calculation confirmed that the synergy of N defects and the surface-grafted amino group achieved a dual-capture strategy, endowing g-C3N5 with higher hydrophilicity and faster photogenerated carrier separation and transfer efficiency. With the modification of urea, the as-prepared samples exhibited a larger specific surface area to further provide more active sites during photocatalysis. The experimental results proved that the photocatalytic hydrogen evolution (PHE) performance of the novel material was significantly enhanced, with the optimal results reaching 5000.6 μmol·h–1·g–1, which was 24.5 and 4.5 times higher than that of the pristine g-C3N5 and the comparison sample, respectively. The stability and reusability of the N-defected g-C3N5 with surface-grafted amino groups were verified by the recycling tests without an obvious decrease after continuous 30 h visible light irradiation. This work provided perspective insight for designing and fabricating the surface functionalized g-C3N5 photocatalysts.