BiOBr-Modified SrTiO3 Heterojunction for Efficient Antibiotic Degradation and Bacterial Inactivation

In this work, we aim to enhance the photocatalytic performance of SrTiO3 by constructing a heterojunction with photoactive BiOBr. The novelty of this study lies in demonstrating the dual functionality of the SrTiO3/BiOBr heterojunction in both photocatalytic tetracycline degradation and antibacterial applications and correlating its performance with its interfacial electronic properties. A SrTiO3/BiOBr (50STO) heterojunction was successfully synthesized by combining microwave-assisted sol–gel-derived SrTiO3 with co-precipitated BiOBr via solid-state calcination. XRD analysis revealed that the synthesized composite consisted of crystalline cubic SrTiO3 and tetragonal BiOBr, confirming the successful formation of a 50STO heterojunction while preserving the crystal structures of both components. PL and EIS analyses revealed modified charge-carrier behavior, further supporting the successful formation of the 50STO heterojunction. XPS confirmed the chemical states of the constituent elements and revealed changes in the surface chemical environment following the coupling of SrTiO3 with BiOBr. SEM, elemental mapping, and UV–Vis DRS analyses demonstrated uniform elemental distribution, enhanced visible-light absorption, suppressed electron–hole recombination, and improved interfacial charge transfer. Consequently, the optimized 50STO composite achieved 45% tetracycline degradation under visible-light irradiation within 150 min, whereas pristine SrTiO3 degraded only 2%. The apparent reaction rate constant increased from 6.11 × 10−7 to 3.2 × 10−3 min−1, while the heterojunction remained stable over five reuse cycles. Radical scavenging and LC–MS analyses identified h+ and •OH as the dominant reactive species and revealed successive tetracycline degradation. The composite also exhibited excellent antibacterial activity against E. coli under white-light irradiation.