Dual Oxygen Supply Floating Cathode-Enabled On-Site Electro-Fenton System for Highly Efficient Online Antibiotics Degradation

On-site electroproduction and activation of hydrogen peroxide (H₂O₂) via the electro-Fenton (EF) process holds significant interest for sustainable wastewater treatment. However, limitations in oxygen diffusion and high energy consumption have hampered the efficiency of 2e^– oxygen reduction reaction (ORR) for H₂O₂ production. This study addresses these challenges with a novel EF system that combines a dual oxygen-supply floating cathode with an oxygen evolution reaction (OER) anode for oxygen supply. The cathode is fabricated with the resorcinol–formaldehyde (RF) resins integrated into carbonized wood (CW) material with well-aligned vertical channels, enabling synergistic utilization of atmospheric and anode-evolved O₂ gases. The abundant internal vertically aligned channels within the EF system resulted in enhanced O₂ gas transportation efficiency and achieving a high H₂O₂ production rate of 483.3 mg·L^–1·h^–1 with the state-of-the-art low electrolysis energy consumption (EEC) of 4.48 kWh·kg^–1 free of aeration. Subsequently, a hydroxyl radical (^•OH) concentration of 31 mg·L^–1 has been achieved within the on-site Fenton activation process, enabling an impressive 96.3% removal efficiency for the degradation of representative antibiotic tetracycline (TC) within 5 min. In addition, the main catalytic active sites for 2e^– ORR on RF resin were further investigated by density functional theory calculations. The dual oxygen supply and active ORR catalyzed by RF resins within the confined channels synergistically contribute to the highly efficient H₂O₂ production and degradation of antibiotics. This novel EF system design demonstrates a promising integrated approach for efficient and sustainable on-site H₂O₂ production and online emergency organic pollutant degradation, which could be extended to design other wastewater treatment devices.