S-scheme Bi(C2O4)OH/Bi2WO6 heterojunction enriched with oxygen vacancies for enhanced photocatalytic degradation of rhodamine B

Limited interfacial charge separation efficiency and insufficient redox capacity severely hinder the practical application of conventional Bi 2 WO 6 -based photocatalysts. To address these issues, a novel Bi(C 2 O 4 )OH/Bi 2 WO 6 heterojunction was constructed via a facile room-temperature one-pot liquid-phase deposition method. Multiple characterizations confirm the intimate interfacial contact between Bi(C 2 O 4 )OH nanorods and uniformly anchored Bi 2 WO 6 nanoparticles, accompanied by the introduction of abundant oxygen vacancies. On the basis of radical trapping experiments, EPR measurements, and electrochemical tests, an S-scheme charge-transfer model is proposed. This model retains the strong redox potentials of both semiconductors, while oxygen vacancies are speculated to act as efficient interfacial charge-trapping and transfer sites to synergistically promote the migration and separation of photogenerated carriers. The optimized 7%Bi(C 2 O 4 )OH/Bi 2 WO 6 composite achieves an RhB removal efficiency of 97.6% within 60 min for 50 mL of RhB solution (30 mg·L -1 ) under 5-W LED lamp irradiation. Radical trapping and EPR tests confirm that ·O 2 - , h⁺, and ·OH are the dominant active species. This work presents a facile and efficient room-temperature fabrication strategy for Bi-based heterojunctions and systematically elucidates the synergistic promotion mechanism between oxygen vacancies and the proposed S-scheme charge-transfer pathway, offering new insights for designing high-performance photocatalysts for organic wastewater remediation.