CNTs/Ce co-doped PbO2 anode for electro-oxidation of triclosan: Fabrication, kinetics, and degradation mechanism based on DFT calculations

Abstract

In this study, an efficient Ti/SnO2-Sb2O3/CNT-Ce-PbO2 electrode was fabricated for triclosan electro-oxidation by co-doping the transition metal Ce and carbon nanotubes (CNTs) into the PbO2 active layer. Characterization results show that the co-doped Ce and CNTs present a synergistic effect on covering the obvious cracks on the Ti/SnO2-Sb2O3 surface, decreasing the PbO2 crystal size, increasing the electrode oxygen evolution potential from 1.60 to 2.17 V vs SCE, and reducing the charge transfer resistance by 66 %. Consequently, Ti/SnO2-Sb2O3/CNT-Ce-PbO2 was the most effective and energy-efficient electrode for hydroxyl radical (•OH) generation and triclosan electro-oxidation in this study. Compared with other two electrodes (Ti/SnO2-Sb2O3 and Ti/SnO2-Sb2O3/Ce-PbO2), triclosan removal by Ti/SnO2-Sb2O3/CNT-Ce-PbO2 was accelerated by 1.8–2.6 times, with the energy demand for abating 90 % triclosan (EEO) decreased by 49 %–67 %. Furthermore, triclosan degradation pathways were proposed based on density functional theory (DFT) calculation and transformation product (TP) identification, with •OH addition at C14 and C11 sites being the most thermodynamically favorable pathway. In addition, the estimated acute and chronic toxicities of TPs were generally decreased than their mother compound. Therefore, the results of this study suggest the feasibility and effectiveness of the Ti/SnO2-Sb2O3/CNT-Ce-PbO2 electrode for triclosan electro-oxidation.