Design and electrochemical study of SnO2-based mixed oxide electrodes

For the electrochemical treatment of wastewater, it is critical to develop electrodes with a high activity for the oxidation of pollutants, long lifetimes, and low cost. In the present study, we have fabricated four different SnO2-based electrodes (Ti/SnO2–Sb2O5, Ti/SnO2–Sb2O5–PtOx, Ti/SnO2–Sb2O5–RuO2 and Ti/SnO2–Sb2O5–IrO2) using the thermal decomposition method and, for the first time, systemically studied their stability and electrocatalytic activity towards the degradation of 2-nitrophenol (2-NPh), 3-nitrophenol (3-NPh) and 4-nitrophenol (4-NPh). Scanning electron microscope (SEM) and X-ray energy dispersive spectrometry (EDS) were used to characterize the morphology and composition of the four different SnO2-based electrocatalysts. Lifetime tests show that doping IrO2 or RuO2 greatly improves the stability of the SnO2-based electrodes. The electrochemical activities of the prepared SnO2-based electrodes were characterized using the degradation of 2-NPh, 3-NPh and 4-NPh. In situ UV/vis spectroscopy was used to monitor the concentration changes of the nitrophenols with time showing that the rate constants for the electrochemical oxidation of the nitrophenols decrease in the order of: 2-NPh > 4-NPh > 3-NPh. The effect of the applied current densities and initial concentrations of nitrophenols have also been investigated. Our study has shown that the fabricated Ti/SnO2–Sb2O5–IrO2 electrodes are very promising for the electrochemical treatment of wastewater.