Y-mediated optimization of 3DG-PbO₂ anode for electrochemical degradation of PFOS

In our previous study, the three-dimensional graphene-modified PbO₂ (3DG-PbO₂) anode was prepared for the effective degradation of perfluorooctanesulfonat (PFOS) by the electrochemical oxidation process. However, the mineralization efficiency of PFOS at the 3DG-PbO₂ anode still needs to be further improved due to the recalcitrance of PFOS. Thus, in this study, the yttrium (Y) was doped into the 3DG-PbO₂ film to further improve the electrochemical activity of the PbO₂ anode. To optimize the doping amount of Y, three Y and 3DG codoped PbO₂ anodes were fabricated with different Y³⁺ concentrations of 5, 15, and 30 mM in the electroplating solution, which were named Y/3DG-PbO₂-5, Y/3DG-PbO₂-15 and Y/3DG-PbO₂-30, respectively. The results of morphological, structural, and electrochemical characterization revealed that doping Y into the 3DG-PbO₂ anode further refined the β-PbO₂ crystals, increased the oxygen evolution overpotential and active sites, and reduced the electron transfer resistance, resulting in a superior electrocatalytic activity. Among all the prepared anodes, the Y/3DG-PbO₂-15 anode exhibited the best activity for electrochemical oxidation of PFOS. After 120 min of electrolysis, the TOC removal efficiency was 80.89% with Y/3DG-PbO₂-15 anode, greatly higher than 69.13% with 3DG-PbO₂ anode. In addition, the effect of operating parameters on PFOS removal was analyzed by response surface, and the obtained optimum values of current density, initial PFOS concentration, pH, and Na₂SO₄ concentration were 50 mA/cm², 12.21 mg/L, 5.39, and 0.01 M, respectively. Under the optimal conditions, the PFOS removal efficiency reached up to 97.16% after 40 min of electrolysis. The results of the present study confirmed that the Y/3DG-PbO₂ was a promising anode for electrocatalytic oxidation of persistent organic pollutants.