Cu/CuFe2O4 integrated graphite felt as a stable bifunctional cathode for high-performance heterogeneous electro-Fenton oxidation

The development of transition metal oxide-based integrated carbonaceous materials for use as bifunctional electrodes of high stability and activity in the heterogeneous electro-Fenton (EF) process is supposed to have great potential in environmental governance. Herein, Cu/CuFe2O4 (CCFO) with different Cu-0 ratios were synthesized by a facile one-step solvothermal approach. These materials were subsequently used to fabricate modified graphite felt through the polytetrafluoroethylene (PTFE)-bonding technique. Importantly, with its hydrophobicity PTFE effectively inhibited metal leaching from the thus obtained cathodes and improved the oxygen utilization rate. Cathode performance in EF-based tetracycline (TC) degradation was found to increase with Cu-0 ratio. The observed increase in activity was attributed to Cu-0 enhancing the 2-electron oxygen reduction reaction selectivity (i.e., H2O2 production) and endowing the cathode with abundant electron-rich centers that accelerated active Fe(II) regeneration, causing rapid conversion of H2O2 to hydroxyl radical ((OH)-O-center dot). The possible TC mineralization pathway was inferred by liquid chromatography-mass spectrometry (LC-MS) analysis, and a catalytic mechanism of the heterogeneous EF process was proposed. The most effective cathode fabricated displayed high stability even at pH 3 (0.84 +/- 0.11 mg/L Fe and 1.35 +/- 0.17 mg/L Cu leaching) and exhibited nearly 80% TC removal efficiency after five oxidation cycles, demonstrating its potential use in heterogeneous EF technology for efficient and durable wastewater treatment.