Ultrasound-Driven Contact-Electro-Catalysis Activates a Non-Radical Pathway for the Degradation of Metronidazole.

The core challenge in contact-electro-catalysis (CEC) for antibiotic degradation is its reliance on exogenous oxidants and low efficiency under additive-free conditions. To address this, a catalytic strategy without external oxidants was developed based on ultrasound-driven contact electrification (CE) at the polytetrafluoroethylene (PTFE) interface. The degradation and mineralization of metronidazole (MNZ) were investigated without any chemical oxidants. Near-complete MNZ removal (>97%) and deep mineralization (85% TOC removal) were achieved within 180 min. Singlet oxygen (1O2) was identified as the dominant reactive oxygen species (ROS), contributing nearly 50% with a generation rate of 0.118 μmol/L/min-significantly higher than other ROS. Dissolved oxygen was revealed as the key oxygen source, and an optimal concentration window was identified. Three MNZ degradation pathways were elucidated, with 1O2-mediated selective oxidation as the predominant route, characterized by high efficiency, minimal byproduct formation, and significantly reduced ecotoxicity. Additionally, excellent catalytic stability and environmental resistance were demonstrated. After five consecutive cycles, the catalytic activity was retained above 90%. Furthermore, good tolerance was exhibited toward common inorganic anions and natural organic matter. This work eliminates the dependence on exogenous oxidants in conventional CEC and offers theoretical insights for efficient removal of recalcitrant antibiotics in water.