Enhancing Electrochemical Degradation of Perfluorooctanoic Acid with Nitrogen-Containing Compounds

Electrochemical advanced oxidation processes are promising for perfluorooctanoic acid (PFOA) degradation; however, strategies for enhancing degradation performance through rational regulation of the reaction medium remain insufficiently understood. In this study, systematic screening of nitrogen-containing compounds showed that discrete inorganic nitrogen species (e.g., ammonium and nitrate) failed to induce any measurable degradation or defluorination of PFOA. In contrast, nitrogen-containing compounds with lone-pair electrons (e.g., glycine and nitrilotriacetic acid) acted as effective promoters, enabling a maximum PFOA removal efficiency of 88.4% within 300 min. Using glycine as a representative additive, mechanistic investigations demonstrated that cooperative coordination among glycine, PFOA, and the Pt electrode surface promotes anodic direct electron transfer. In parallel, glycine-assisted electrochemical processes generate reactive oxidizing species, particularly reactive nitrogen species (e.g., ^•NO₃) and hydroxyl radicals (^•OH), which contribute to indirect oxidation pathways. These two processes act synergistically to govern the PFOA degradation. Fluorine mass balance analysis further revealed that stepwise defluorination via C_nF_2n+1^• and COF₂ formation dominated mineralization, accounting for 85.4-97.9% of fluorine release, whereas short-chain intermediates constituted only a minor route. Overall, this study elucidates the coupled roles of interfacial coordination regulation and reactive nitrogen chemistry in electrochemical PFAS degradation, providing mechanistic guidance for effective electrochemical treatment systems.