Hydrothermally modified graphite felt as the electro-Fenton cathode for effective degradation of diuron: The acceleration of Fe2+ regeneration and H2O2 production

Abstract

The generation of H2O2 and the regeneration rate of Fe2+ both affect the degradation performance of the electro-Fenton (EF) process. Therefore, it is important to develop a cathode that efficiently produces H2O2 and regenerates Fe2+. In this study, graphite felt (GF) was modified via a simple hydrothermal method using ammonium persulfate as the modifier. The physicochemical and electrochemical properties of hydrothermally modified GF (H-GF) were substantially improved. The surface of H-GF was successfully doped with O and N, and its oxygen reduction reaction activity increased significantly. Compared with raw GF, the yield of H2O2 and the regeneration rate of Fe2+ of H-GFwere considerably improved. The EF system constructed with H-GF as the cathode could completely remove diuron at −0.65 V/SCE within 40 min. In the EF system, H-GF exhibited an excellent degradation effect in different types of water (tap and river water) and different pollutants (amoxicillin, atrazine, and sulfamethoxazole). After the 40th cycle, the H-GF cathode retained excellent stability. According to density functional theory calculations, H2O2 and Fe2+ were easily generated due to the low energy barrier required for the adsorption of O2 and Fe3+ on H-GF. Finally, a possible degradation path of diuron in the EF process was proposed, and the toxicity of the intermediates produced in the degradation process of diuron was analyzed.