Oxygen Vacancy-Engineered FeP/BiOBr Heterojunction for Enhanced Photo-Fenton Degradation of Tetracycline Hydrochloride: Synergistic Catalysis and Mechanistic Insights

In this study, oxygen vacancy-engineered FeP/BiOBr heterojunction composites (FB-3) were synthesized via a facile hydrothermal method to achieve enhanced tetracycline hydrochloride (TCH) degradation through a visible-light-driven photo-Fenton process. Systematic characterizations (SEM, XRD, XPS, and EPR) confirmed the successful integration of FeP with BiOBr, which modulated the band structure, introduced abundant oxygen vacancies (OVs), and suppressed photogenerated carrier recombination. Under the optimized conditions (0.2 g L^-1 catalyst, 10 mM H₂O₂, and pH 4.2), the FB-3 composite achieved 94.2% TCH removal at an initial concentration of 40 mg L^-1 within 90 min, with 73.9% TOC mineralization and minimal iron leaching of only 0.21 mg L^-1. Mechanistic studies revealed that OVs acted as electron traps, accelerating Fe²⁺/Fe³⁺ redox cycling and synergistically activating H₂O₂ to generate dominant reactive radicals (•OH and •O₂^-). Radical trapping experiments and EPR analysis validated the critical roles of photogenerated carriers and OVs in enhancing surface kinetics. The composite exhibited robust performance in diverse water matrices, demonstrating potential for antibiotic wastewater treatment.