Fabrication and characterization of PEG-In2O3 modified PbO2 anode for electrochemical degradation of metronidazole

An In2O3-PbO2 anode with high electrocatalytic activity was prepared in our previous study. However, the service life of In2O3-PbO2 anode needed to be further improved. Thus, a typical stabilizer of polyethylene glycol (PEG) was used to modify the In2O3-PbO2 anode in this study. Theoretical and experimental results show that a small amount of PEG promoted the doping of In2O3 into β-PbO2 film, while excessive PEG reduced the doping of In2O3. Doping a moderate amount of PEG not only reduced the PbO2 crystal size, improved the density of electrode film, reduced the charge transfer resistance, increased the oxygen evolution potential, number of active sites and capacity of •OH generation of In2O3-PbO2 anode, but also prolonged the service life of In2O3-PbO2 anode from 96 to 137 h. In the process of electrochemical degradation of metronidazole, the PEG/In2O3-PbO2 anode exhibited superior electrocatalytic activity. The degradation rate constant at the PEG/In2O3-PbO2 anode was 1.682 times higher than that at In2O3-PbO2 anode. After 60 min of electrolysis, COD and TOC removals reached up to 80.92% and 78.52%, respectively, much higher than those of In2O3-PbO2 anode (69.24% and 55.83%, respectively). Additionally, a total of 13 intermediates generated in the degradation process were identified by LC-MS, and two possible degradation pathways were proposed accordingly. Overall, this study offers a promising approach for enhancing the electrocatalytic activity and stability of the PbO2 anode.