Built-in Electric Field-Driven Charge Separation in BiOI/TiO2 p-n Heterojunctions for Robust Visible-Light Degradation of Oxytetracycline in Simulated Wastewater

The pervasive contamination of water bodies by antibiotics necessitates the development of efficient remediation technologies. Herein, A visible-light-responsive BiOI/TiO 2 p-n heterojunction photocatalyst was engineered through a facile solvothermal approach, achieving exceptional oxytetracycline (OTC) degradation in simulated complex aquatic environments. The optimized BiOI/TiO 2 (2:1) composite degraded 92.8% of 20 mg/L OTC within 90 min––2.3-fold and 3.1-fold faster than pristine BiOI and TiO 2 , respectively––while exhibiting a record-high specific degradation rate ((SDR): 5.16×10⁻ 5 mg/(g·W·min)). Systematic characterizations (XPS/EIS/EPR) revealed that the built-in electric field at the p-n interface spatially separates charges, suppresses recombination by 54.5%, and extends carrier lifetime. Crucially, the composite maintained >85% efficiency in saline (0.1 M NaCl) and organic-rich water (20 mg/L HA), with <6% activity loss after 5 cycles due to Bi-O-Ti interfacial stabilization (XRD/ICP-MS). Mechanistic studies identified dual reactive pathways: h + -directed oxidation (primary) and ·O 2 ⁻-mediated cleavage (secondary), achieving >70% mineralization (TOC). This work provides a scalable interfacial engineering strategy for designing robust photocatalysts applicable to antibiotic-contaminated wastewater.