Visible-light photocatalytic oxygen activation by oxygen vacancies-rich BiOI for enhanced removal of bisphenol A in water

Abstract

Bisphenol A (BPA) is a persistent endocrine disruptor that poses high ecological and healthy risks. Photocatalytic oxygen (O₂) activation has emerged as a promising technology for water decontamination, but its efficiency is often hindered by sluggish interfacial electron transfer between photocatalysts and O₂ molecules. In this study, a Zn/S co-doping defect engineering strategy was developed to introduce oxygen vacancies (OVs) into BiOI for enhancing visible-light photocatalytic O₂ activation and BPA removal. The OVs-rich BiOI with sub-band near the conduction band provided electron and reactant trapping sites that facilitated spatial separation of photogenerated electrons (e⁻) and holes (h⁺). The localized electrons at OVs reduced O₂ via single-electron transfer to generate superoxide radicals (•O₂⁻), which were further oxidized to singlet oxygen (¹O₂) by h⁺. Synergistic oxidation of ¹O₂ and h⁺ significantly enhanced BPA degradation, achieving approximately 90 % removal within 120 min. The reaction rate constant (0.01829 min⁻¹) was nearly double that of pure BiOI (0.00948 min⁻¹). Furthermore, the OVs-rich BiOI catalyst demonstrated excellent stability and reusability, maintaining >90 % BPA removal efficiency after five cycles of test. This study offers a new strategy for developing visible-light photocatalyst to remove recalcitrant emerging organic contaminants in water.