Promotion of the degradation perfluorooctanoic acid by electro-Fenton under the bifunctional electrodes: Focusing active reaction region by Fe/N co-doped graphene modified cathode

Abstract

In this study, Fe/N co-doped graphene electrode (Fe/N-GE@GF) was fabricated and a synergistic electrochemical process of the cathode was proposed for the efficient degradation of perfluorooctanoic acid (PFOA). The oxygen reduction reaction (ORR) capacity and hydroxyl radical (•OH) production were the key parameters for the degradation efficiency of PFOA. The ORR was enhanced due to the strong interaction between N-Fe bonds.During the electrochemical reaction, the electron transfer is accelerated due to the interaction between FeOx and N, which enhances the ORR of hydrogen peroxide (H2O2) generation. In addition, the co-doped Fe/N also enhances the adsorption capacity of the cathode such as carbon, pyridine-N, and graphene-N further hindering the desorption of PFOA, assuring controlling the reaction region. The Fe/N-GE@GF provided an adequate interaction between the •OH generation and the catalytic degradation region by improving the selectivity of the 2e-ORR and •OH generation. The region of PFOA degradation and •OH generation were both controlled near the cathode, which is referred to here as the “focused active reaction region”. PFOA is enriched by the formation of •OH and pyridine-N bonds in the focused active reaction region. The •OH generated in situ efficiently aids the degradation of PFOA. In this electrocatalytic process, the catalytic degradation efficiency of PFOA is increased to 95 % and the TOC removal rate of PFOA increased to 90 % after 3 h, indicating that the enrichment of PFOA around the cathode continuously and efficiently interacts with the •OH generated in situ with the action of Fe/N-GE@GF system.