Potential modulation strategy on bismuth vanadate-based semiconductor to enhance antibiotic degradation in heterogeneous electro-Fenton system

This work proposed the novel Co-doped bismuth vanadate bismuth/ graphite felt (Co-BiVO4/GF, Co-BVO for short) cathode with reduced metal reduction overpotential (OPMRR) for effective decomposition of antibiotic in heterogeneous electro-Fenton (EF) system. Results showed that Co doping into the BVO reduced the metal reduction overpotential and allowed the system to operate at lower cell voltages. The overpotential of cobalt reduction reaction (OPCRR) for the 3Co-BVO/GF was only 270 mV, much lower than that of bismuth reduction reaction (OPBRR) for the BVO/GF (930 mV), which allowed much higher current of cobalt reduction reaction (CRR) (15.23 mA) than that of bismuth reduction reaction (BRR) (6.51 mA) under OP, facilitating more efficient generation of H2O2 and ·OH on the 3Co-BVO/GF cathode. Moreover, the EF system with the 3Co-BVO/GF cathode achieved Levofloxacin (LEV) removal of 97.2 % within 60 min at pH 3, aeration rate of 60 mL·min−1, and voltage of −0.60 V vs. saturated calomel electrode (SCE) with LEV initial concentration of 20 mg·L−1. Density functional theory (DFT) calculations demonstrated that Co doping effectively modulated electronic structure of the BVO, accelerating electron transfer through Co-O bond and accumulation at Co active sites for reactive species production. At least 12 degradation intermediates with generally lower ecotoxicity were identified during LEV degradation, and three possible degradation routes of LEV were proposed. This study offers insights into regulating overpotential of bismuth-based cathodes for efficient pollutants elimination in EF system.