Highly efficient electrochemical degradation of perfluorooctanoic acid (PFOA) by F-doped Ti/SnO₂ electrode

Highlights: • A novel SnO₂ electrode is prepared by F doping instead of the traditional Sb doping. • SnF₄ as single-source precursor is used to fabricate the long-life Ti/SnO₂–F anode. • F-doped Ti/SnO₂ anode possesses high OEP and decomposition ability for PFOA. • Further mechanistic detail of PFOA degradation on Ti/SnO₂–F electrode is proposed. - Abstract: The novel F-doped Ti/SnO₂ electrode prepared by SnF₄ as the single-source precursor was used for electrochemical degradation of aqueous perfluorooctanoic acid (PFOA). Higher oxidation reactivity and significantly longer service life were achieved for Ti/SnO₂–F electrode than Ti/SnO₂–X (X = Cl, Br, I, or Sb) electrode, which could decomposed over 99% of PFOA (50 mL of 100 mg L⁻¹) within 30-min electrolysis. The property of Ti/SnO₂–F electrode and its electrooxidation mechanism were investigated by XRD, SEM–EDX, EIS, LSV, and interfacial resistance measurements. We propose that the similar ionic radii of F and O as well as strong electronegativity of F caused its electrochemical stability with high oxygen evolution potential (OEP) and smooth surface to generate weakly adsorbed ·OH. The preparation conditions of electrode were also optimized including F doping amount, calcination temperature, and dip coating times, which revealed the formation process of electrode. Additionally, the major mineralization product, F⁻, and low concentration of shorter chain perfluorocarboxylic acids (PFCAs) were detected in solution. So the reaction pathway of PFOA electrooxidation was proposed by intermediate analysis. These results demonstrate that Ti/SnO₂–F electrode is promising for highly efficient treatment of PFOA in wastewater.