A coupling mechanism of anodic oxygen evolution reaction during organic pollutants oxidation

In this work, β-PbO₂/Ti and RuO₂-IrO₂/Ti anodes and Ti cathodes were employed to conduct electrocatalytic phenol degradation experiments at various current densities. The difference in degradation rates between the two anodes indicated that the oxygen evolution reaction (OER) is related to the organic matter concentration. Consequently, a coupling mechanism “active-site competition mechanism (ACM) + adsorbate evolution mechanism (AEM)” for anodic oxygen evolution was described. Based on this mechanism and experimental results, it can be concluded that the ACM influences the initial degradation rate, and the AEM affects final organic matter concentrations. DFT calculations showed that RuO₂-IrO₂ exhibits excellent AEM activity attributed to the lower OER overpotential (0.7 V) and stronger adsorption energies of *O oxygenated intermediate (-1.52 eV). At the same time, RuO₂-IrO₂ possesses slight thermodynamic reaction energy of ACM, which are 103.3, 31.6 and 89.5 kJ/mol. Therefore, the slower degradation rates and lower removal efficiency on RuO₂-IrO₂/Ti are owing to the better ACM and AEM activity. Then, electrocatalytic experiments at various pH were conducted to verify the conclusion that AEM affects final organic matter concentrations. Finally, this work has implications for a better understanding of the OER mechanism and provides theoretical guidance for improving the removal efficiency of organic pollutants.