Electrochemical degradation of dye on TiO₂ nanotube array constructed anode

A high oxygen evolution potential (2.6V) and conductivity of Ti/TiO₂ NTs/Ta₂O₅-PbO₂ anode was fabricated by mixed metal oxide. A well-aligned TiO₂ nanotubes was successfully prepared by using 1-butyl-3-methylimidazolium tetrafluoroborate as the electrolyte. The surface structure of anodes were characterized by scanning electron microscope, X-ray diffraction and energy dispersive X-ray spectroscopy. During the electrochemical degradation experiments, the effects of different anodes, current density, initial pH value and concentration were discussed. The results showed that co-doped Ta₂O₅ coating is an effective method to improve the surface morphology and the electrochemical characterization of Ti/TiO₂ NTs/PbO₂. At the initial pH value of 3 and current density of 12 mA cm^-2, the removal rates of Acid Orange 7 and total organic carbon with Ti/TiO₂ NTs/Ta₂O₅-PbO₂ anode were almost 100% and 98.3%. Comparing with Ti/PbO₂ anode at the same charge consumption (3 A h L^-1), the instantaneous current efficiency of the Ti/TiO₂ NTs/Ta₂O₅-PbO₂ anode and Ti/TiO₂ NTs/PbO₂ anode increased by 40.0% and 27.1%, respectively. The highest rate of k_.OH on Ti/TiO₂ NTs/Ta₂O₅-PbO₂ anode was 12.4 μmol (L min)^-1. The organic dyes are oxidized into CO₂ and H₂O by ^.OH radical. The reaction process and mechanism during the electrochemical degradation were discussed.