Electrocatalytic Oxidation of p-Nitrophenol by Different Metals (Ce, Bi, and La) Modified CF/PbO2 Anodes

In this study, carbon felt-supported PbO2 (CF/PbO2) anodes were modified via doping Ce, Bi and La. The incorporation of these metal dopants significantly refined the β-PbO2 grain size, increased the oxygen evolution overpotential, and reduced the charge transfer resistance of CF/PbO2 anodes. Among the modified anodes, the CF/La–PbO2 anode exhibited superior electrocatalytic oxidation performance, achieving a p-nitrophenol (p-NP) degradation efficiency of exceeding 99% within 90 min of electrolysis. Even after 10 consecutive cycles, the CF/La–PbO2 anode maintained excellent stability, with a p-NP efficiency over 96%. The results of quenching experiments and electrochemical characterizations revealed that the degradation behaviour of p-NP on the modified anodes was dominated by direct electron transfer, but not active species-mediated oxidation. Furthermore, GC–MS analysis identified several intermediates, and a plausible degradation pathway involving hydroxylation, ring cleavage, and mineralization was proposed. Overall, the incorporation of La, Ce, and Bi—particularly La—significantly enhanced both the electrocatalytic activity and stability of CF/PbO2 anodes, showing their potential as promising anode material for treatment of organic pollutants.