Enhanced antibiotic photodegradation by Bi24O31Cl10/BiPO4 Z-scheme photocatalyst: DFT calculation, photocatalytic mechanism insight and toxicity evolution

Abstract

Layered bismuth-rich oxyhalides exhibit broad light absorption and high electron-hole separation efficiency. However, their photocatalytic performance remains limited by high recombination rates, resulting in low quantum efficiency. These challenges in interfacial charge separation can be effectively addressed through the strategic design of heterojunctions and the introduction of surface defects. In this study, a novel Z-scheme Bi₂₄O₃₁Cl₁₀/BiPO₄ (Bi₂₄P) photocatalyst was synthesized using a straightforward stirring method, incorporating PO₄³⁻ to enhance photocatalytic degradation efficiency. The effects of various preparation conditions and application scenarios on the photocatalytic activity of Bi₂₄P were systematically investigated. Under visible light irradiation, the optimized Bi₂₄P photocatalyst (0.1 g/L dosage) achieved an 82.30 % degradation rate for 50 mL of 20 mg/L tetracycline (TC) within 2 h, with a pseudo-first-order reaction rate constant twice that of Bi₂₄ alone. The Bi₂₄P catalyst also demonstrated exceptional salt tolerance, reusability, versatility, and broad spectral response. Mechanistic studies utilizing photoelectric measurements, density functional theory (DFT) analysis, and scavenger experiments revealed that the enhanced degradation performance is primarily attributed to the synergistic coupling of semiconductor interfaces and oxygen vacancies within the composite catalyst. This structure facilitates the formation of a Z-scheme heterojunction, optimizing internal electron transfer pathways. Additionally, toxicity assessments confirmed a significant reduction in water toxicity after photodegradation. These findings offer valuable insights for the development of Bi_xO_yCl_z-based catalysts to address the challenges of antibiotic-contaminated wastewater treatment.