Dynamic oxygen vacancy engineering on CuO via refreshable catalytic surface for high-efficient water decontamination

Oxygen vacancies (O_v) on metal oxide surfaces exhibit high catalytic activity for activating peroxymonosulfate (PMS) in wastewater decontamination, yet their in-situ regeneration remains a significant challenge. This study successfully achieves in-situ real-time regeneration of O_v on CuO surfaces through simple alkali etching without interrupting the contaminant removal process. The surface hydroxyl groups introduced by alkali treatment significantly reduce the formation energy of O_v on CuO surfaces from 1.60 eV to 0.38 eV. Both experimental results and density functional theory calculations reveal that the high activity of CuO relies on the synergy of surface hydroxyl groups and O_v. This synergy increases the antibonding states below the Fermi level and the electron spin density of Cu near O_v, thereby promoting electron transfer from CuO to PMS. As a result, by just adding an equimolar amount of alkali relative to PMS in CuO/PMS system, the degradation rate constant of sulfamethoxazole (SMX) greatly increases by 42 times. The primary reactive oxygen species in this system are sulfate radicals and hydroxyl radicals. Furthermore, OH^-/CuO/PMS system exhibits a long-term stability (> 300 h) for SMX removal in a real water matrix. This work provides a highly executable method to in-situ real-time regenerate O_v on CuO surfaces, representing significant progress in the critical yet underappreciated field of catalyst regeneration.