Efficient PFOA decontamination using photoelectrocatalytic coupled PMS activation: Unleashing electrons and superoxide radicals for rapid degradation

Direct oxidation of per- and polyfluoroalkyl substances (PFAS) necessitates excessive energy or prolonged treatment, while reductive defluorination effectively cleaves C-F bonds. However, strict anaerobic requirements hinder its practical implementation. Herein, a photoelectrocatalytic-peroxymonosulfate (PEC-PMS) integrated system was developed for perfluorooctanoic acid (PFOA) degradation under ambient conditions. The PEC-PMS system with the sophisticated MoSe₂/TiO₂ photoelectrode demonstrated 93.6 % PFOA removal within 40 min. Density functional theory (DFT) calculations revealed enhanced PFOA adsorption on MoSe₂/TiO₂ (E_ads = -4.25 eV) compared to TiO₂ (E_ads = -0.89 eV). Furthermore, the Mo⁴⁺/Mo⁵⁺ redox pairs promoted PMS activation to accelerate reaction kinetics. The quenching experiments and electron paramagnetic resonance spectra elucidated the crucial role of electrons (63.7 %) and superoxide radicals (42.2 %) during the degradation. Moreover, DFT calculations and intermediate product analyses clarified the main degradation pathway of PFOA. PFOA reacted with electrons to generate C₇H₁₅· (Gibbs free energy, ΔG = -0.267 eV/mol), which was subsequently oxidized by superoxide radicals (ΔG = -4.379 eV) to form short-chain PFAS. Overall, our investigations achieved efficient PFOA elimination under air conditions and clarified their degradation mechanisms, providing a new perspective for the treatment of PFAS-contaminated wastewater.