Electrocatalytic Degradation of Phenol by Sn-Sb Co-doped Ti/SnO2 Electrode: Performance and Mechanism
To optimize the anode structure of Ti/SnO2-based electrodes in electrochemical advanced oxidation processes (EAOPs) and enhance their electrocatalytic activity and stability, Sn-Sb co-doped Ti/SnO2 electrodes were fabricated via a sol-gel method. The degradation performance and mechanism were evaluated using phenol as a model pollutant. Three electrodes were prepared with different Sn/Sb molar ratios: Ti/SnO2 (10:0), Ti/Sb (0:10), and Ti/SnO2-Sb (9:1). Characterization by XRD, SEM, and electrochemical tests revealed that the Sn-Sb co-doped electrode exhibited a dense surface, higher oxygen evolution potential (OEP), larger electrochemically active surface area, and lower charge transfer resistance compared to single-doped counterparts. In constant-current electrolysis experiments (20 mA·cm−2, pH=5, 0.1 mol·L−1 Na2SO4), the co-doped electrode achieved superior phenol and TOC removal efficiencies and higher apparent rate constants, with the lowest specific energy consumption per unit TOC removal. Radical quenching and intermediate analysis indicated that hydroxyl radicals (·OH) were the dominant reactive species. The degradation pathway involved aromatic ring hydroxylation, ring opening, and further mineralization of short-chain carboxylic acids. Sn-Sb co-doping enhanced the generation of ·OH by increasing surface adsorbed oxygen and defect site density. This synergistic doping strategy significantly improved the electrocatalytic activity and service life of Ti/SnO2-based anodes, providing a basis for the rational design of anode materials for EAOPs in treating refractory organic wastewater.