Dual-redox cycling driven charge transfer in CuxO/CeO2 heterojunction for photocatalytic activation of peroxymonosulfate toward tetracycline degradation

The efficient removal of antibiotic residues such as tetracycline (TC) from water remains challenging. Research has demonstrated that heterogeneous systems utilizing photocatalysis to activate peroxymonosulfate (PMS) exhibit exceptional performance. However, preparing materials with strong charge transfer capabilities and stability still poses certain challenges. This study developed a Cu x O/CeO 2 heterojunction composite with abundant oxygen vacancies (O V ) for visible-light-driven activation of peroxymonosulfate (PMS). The hierarchical flower-sphere structure of CeO 2 provides ample adsorption sites and mass transfer channels, while the synergy between the heterojunction interface and the dual redox cycles of Cu + /Cu 2+ and Ce 3+ /Ce 4+ significantly enhances visible-light absorption and accelerates the separation and transfer of photogenerated carriers. Femtosecond transient absorption (fs-TA) spectroscopy further confirms that the formation of the heterojunction effectively regulates the direction of carrier transfer and prolongs the charge lifetime. Density functional theory (DFT) calculations reveal that O V markedly promote the adsorption and activation of PMS. Under visible light irradiation, the system achieves a TC degradation efficiency of 99.2% within 60 min, primarily driven by sulfate radicals (SO 4 •− ) and hydroxyl radicals (•OH), with the intermediates exhibiting generally low toxicity. In addition, in-situ infrared spectroscopy (in-situ FT-IR) further confirmed the outstanding TC adsorption capacity and degradation activity of the Cu x O/CeO 2 heterojunction composite. This work provides insightful perspectives for designing efficient and stable heterojunction catalysts through defect and interface engineering for water purification.