Phosphorus doping to boost the electro-Fenton degradation of sulfamethoxazole using mixed-valence copper(I and II) phosphate/etched graphite felt cathode

Non-metallic atom doping is a good strategy to promote the cathode performance in the electro-Fenton process. Therefore, a mixed-valence copper (I and II) phosphate (Cu2PO4) catalyst on P-doped etched graphite felt (EGF), with a strip-groove rough surface, was prepared in this study. The P-doped Cu2PO4/EGF electrode completely removed sulfamethoxazole (SMX) from contaminated water within 90 min over a wide pH range of 5.6–9 and removed 99.6 % of SMX at pH 11. Quenching experiments showed that the main reactive oxygen species (ROS) was O2–. According to density functional theory calculations, the adsorption reaction energy (EP = -2.149) of P atoms doped on the EGF surface was lower than that of pyrrolic nitrogen atoms (EN = −0.434), indicating that they were more conducive to oxygen adsorption. Finally, we investigated the mechanism of P-doped Cu2PO4/EGF adsorption and the catalytic production of O2– from O2. Four main degradation pathways were identified based on the intermediates identified during degradation. Toxicity analysis of the intermediates showed that electro-Fenton degradation reduced the ecotoxicity of SMX. The enhanced electrocatalytic activity obtained by P doping of heterogeneous catalysts provides a new method for preparing efficient and stable composite electrodes for pollutant degradation.