Synergistic Photocatalytic Oxidation and Reductive Activation of Peroxymonosulfate by Bi-Based Heterojunction for Highly Efficient Organic Pollutant Degradation

Organic pollutants present a substantial risk to both ecological systems and human well-being. Activation of peroxymonosulfate (PMS) have emerged as an effective strategy for the degradation of organic pollutants. Bi-based heterojunction is commonly used as a photocatalyst for reductively activating PMS, but single-component Bi-based heterojunction frequently underperforms due to its restricted absorption spectrum and rapid combination of photogenerated electron-hole pairs. Herein, BiVO₄ was selected as the oxidative semiconductor to form an S-type heterojunction with CuBi₂O₄-x-CuBi₂O₄/BiVO₄ (x = 0.2, 0.5, and 0.8) for PMS photoactivation. The built-in electric field (BEF) in x-CuBi₂O₄/BiVO₄ promoted electron transfer to effectively activate PMS. The x-CuBi₂O₄/BiVO₄ heterojunctions also demonstrate stronger adsorption of the polar PMS than pure CuBi₂O₄ or BiVO₄. In addition, the BEF prompts photoelectrons able to reduce O₂ to •O₂^- and photogenerated holes in the valence band of BiVO₄ able to oxidize H₂O to generate •OH. Therefore, under visible light irradiation, 95.1% of ciprofloxacin (CIP) can be degraded. The 0.5-CuBi₂O₄/BiVO₄ demonstrated the best degradation efficiency and excellent stability in cyclic tests, as well as a broad applicability in degrading other common pollutants. The present work demonstrates the high-efficiency S-type heterojunctions in the coupled photocatalytic and PMS activation technology.