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 CnF2n+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.