Collaboration of oxygen vacancy and piezo-polarization enable orientational activation of peroxymonosulfate for high-performance water decontamination

Piezo-polarization and oxygen vacancy (OV) are recently attracting extensive interest in heterogeneous peroxymonosulfate (PMS) activation due to their properties of regulating electron transfer. However, there is a lack of comprehensive analysis on the interaction of piezo-polarization and OV for PMS activation. In this study, we developed an OV-containing piezocatalyst, Bi₂Fe₄O₉, to piezo-activate PMS for carbamazepine (CBZ) degradation. 100% of CBZ was degraded within 5 min, significantly outperforming that of Bi₂Fe₄O₉ piezocatalysis, PMS activation by ultrasonic, and PMS activation by Bi₂Fe₄O₉ itself. This high performance was attributed to the synergistic collaboration of piezo-polarization and OV via strengthening PMS adsorption, prolonging PMS O-O bond, boosting charge transfer, finally orientationally generating ¹O₂ as the dominant reactive species. Systematic mechanistic studies revealed that as the crucial precursor to ¹O₂, SO₅rad⁻ was generated from the oxidation of PMS after donating an electron, and further converted into ¹O₂ via multiple pathways, including metal-mediated and O₂rad⁻-mediated routes. This work offers profound insight into the mechanism of oxygen vacancy-containing piezo-activated PMS process, and provides an excellent reference for developing high-efficiency and environmentally benign PMS-based advanced oxidation processes.