Synergistic nitrogen vacancies boost S-scheme charge separation in CuO/carbon nitride for efficient photocatalytic hydrogen production

Carbon nitride (CN)-based S-scheme heterojunction photocatalysts are a research hotspot for photocatalytic water splitting due to their efficient charge separation capability. This study successfully constructed a CuO/CN S-scheme heterojunction via a two-step calcination method and systematically investigated the effects of CuO content and calcination temperature on the material properties. Characterization results revealed that CuO nanoparticles were uniformly loaded onto CN nanosheets. 0.28 %CuO/CN exhibited the largest specific surface area and the narrowest bandgap. Synergistic nitrogen vacancies significantly enhanced charge carrier separation efficiency. Under 100 W LED light irradiation, the photocatalytic performance showed that 0.28 %CuO/CN calcined at 550 °C under air atmosphere achieved an H 2 evolution rate of 10.4 mmol h −1  g −1 and an apparent quantum efficiency (AQE) of 11.5 %, which is 9.0 times higher than that of pure CN. Furthermore, the activity decreased by only 3.4 % after 4 cycles. Mechanistic studies confirmed by in-situ EPR and band structure analysis, demonstrated that the built-in electric field drives electrons to follow an S-scheme migration path. This work provides a new strategy for designing highly efficient and stable defect-engineered S-scheme heterojunction photocatalysts.