Solvent-regulated synthesis of S-scheme BiOBr/TiO2 heterojunctions: Mechanism and pathway analysis for efficient photocatalytic degradation of sodium pentachlorophenate

• An S-scheme heterojunction BiOBr/TiO 2 was prepared via a one-step solvothermal method. • EG proportion could greatly affect its microstructure and photocatalytic performance. • 95% of PCP-Na at environmental concentration level could be degraded within 90 min. • The reactive species ∙O 2 − and h + played crucial roles in the photodegradation process. • Dechlorination and single-electron coupling reaction were main degradation pathways. In this study, a high-performance S-scheme heterojunction BiOBr/TiO 2 photocatalyst composite was obtained within 1h through adjusting the key factors of one-step solvothermal method for degradation of sodium pentachlorophenate (PCP-Na). Particluarly, ethylene glycol proportion in solvent significantly influenced the morphology and crystalline phase of BiOBr/TiO 2 composite. The optimized composite featured a unique mulberry-like structure composed of densely arranged microspheres, which enhanced its specific surface area and provided abundant active sites. Compared to pure BiOBr and TiO 2 , the BiOBr/TiO 2 composite exhibited a broader visible-light absorption range, more efficient charge separation and transfer, and a stronger photocurrent response. Under visible light irradiation, BiOBr/TiO 2 degraded 93.09% of PCP-Na within 120 minutes, which was approximately 15 times higher than that of pure TiO 2 . Mechanistic investigations indicated that ·O 2 − and h + were the primary active species involved in the photocatalytic process. The main degradation pathways invloved dechlorination and single-electron coupling reaction. Moreover, the composite exhibited high degradation efficiency for PCP-Na in real water sample under visible light and maintained good stability.