Fabrication Of Adsorptive SnO₂ Electrode And Characterization Of Electrocatalytic Properties

Electrochemical advanced oxidation processes (EAOPs) has been considered as a promising approach for the treatment of refractory organic wastewater due to its high efficiency, simple equipment, ease of operation, fast reaction rate, adding no catalyst and environmental friendliness. It is investigated that the properties of anodes is the key factor in the effectiveness of electrochemical oxidation. In this work, a new anode with designed microstructure was prepared to improve electrocatalytic performance.A novel Sb-doped SnO2 electrode with adsorption properties (TiO2-NTs/m-SnO2-Sb) has been fabricated through electrodeposition method with Pluronic F127 as a template agent. The preparation conditions was confirmed that the mole ratio of template agent for F127:Sn (Sb) was 0.0055:1, electroplating current density was 2 mA·cm-2, and calcination temperature was 450 ℃. The morphology, composition and structure of TiO2-NTs/m-SnO2-Sb electrodes were characterized by SEM, EDS, XRD and BET test technologies compared with TiO2-NTs/SnO2-Sb electrode prepared by electrodeposition and Ti/SnO2-Sb electrode prepared by thermal decomposition. The results revealed that TiO2-NTs/m-SnO2-Sb electrode possessed well-distributed particles and better coverage of substrate. Mesoporous structure was preserved with 87.9 m2g-1surface area and 3.8 nm most probable pore size. LSV and CV curves showed that TiO2-NTs/m-SnO2-Sb electrode had higher oxygen evolution potential and greater electrochemical active area.TiO2-NTs/m-SnO2-Sb electrode was used in benzoic acid degradation. The reaction accorded with first order kinetics and benzoic acid removal rate reached 90.3%. The corresponding kinetic constant was 2.5 times of TiO2-NTs/SnO2-Sb and 1.5 times of Ti/SnO2-Sb electrode, and energy consumption was lower. The effects on electrochemical oxidation by TiO2-NTs/m-SnO2-Sb electrode were investigated. It was indicated that the removal rate of 20 mg-L"1 benzoic acid reached maximum under the conditions that Na2SO4 concentration was 7 g-L-1, current density was 20 mA·cm-2 and initial pH was 5.The degradation of benzoic acid was studied. Both benzoic acid and its intermediate could be degraded by electrocatalytic oxidation. It was speculated that benzoic acid was oxidized to hydroxyl benzoic acid and phenol, then further be degraded after opening of benzene ring, and finally regenerated into small molecular organic acid or complete mineralization. The electrosorption equilibrium quantity of electrodes was tested under 1 V voltage and that of TiO2-NTs/m-SnO2-Sb electrode was 45.1 μg·cm-2. But the contribution of electrosorption on pollutant removal was limited and electrocatalytic oxidation process was mainly approach for degradation of benzoic acid.