Oxygen Vacancy-Enhanced S-Scheme C-ZnO/B-g-C3N4 Heterostructure for Efficient Photocatalytic Degradation of Methylene Blue

Developing porous-structured organic semiconductor photocatalysts with high charge transfer efficiency is crucial for solar energy utilization, yet remains challenging in pollutant remediation. Herein, an S-scheme C-ZnO/B-g-C₃N₄ photocatalyst with oxygen vacancies was fabricated through modified biomass-derived C doping for methylene blue (MB) degradation. The optimized catalyst achieved 97.8% degradation efficiency within 70 min under visible light. UV-DRS analysis revealed that C doping narrowed the bandgap and enhanced visible-light absorption. XPS results confirmed the S-scheme charge transfer pathway in C-ZnO/B-g-C₃N₄. The synergistic effects of C doping and oxygen vacancies significantly improved charge separation and facilitated S-scheme heterojunction formation. The catalyst exhibited superior photocatalytic performance in alkaline conditions and maintained excellent recyclability. Radical trapping experiments identified the primary reactive species as h⁺ > ·O₂⁻ > ·OH in descending order of contribution. This work provides a promising strategy for solar-driven pollutant remediation by combining biomass-derived carbon modification with S-scheme heterojunction engineering.