Interactive oxidation of photoelectrocatalysis and electro-Fenton for azo dye degradation using TiO2–Ti mesh and reticulated vitreous carbon electrodes

A crystallized TiO2 thin film was prepared by electrolytic anodization of a pure Ti mesh in sulfuric acid–phosphoric acid–hydrogen peroxide and hydrofluoric acid–sodium fluorid–hydrogen peroxide electrolyte solutions. The TiO2 particles directly grown on the Ti mesh surface had the regular anatase crystal structure. The TiO2 thin film showed a multiporous structure and the mean micropore size was about 260 nm. The azo dye orange-G degradation reaction was studied in an undivided cell by using the air-diffusion reticulated vitreous carbon as the cathode for the H2O2 electrogeneration and TiO2–Ti mesh as the photoanode for the photoelectrocatalysis under ultraviolet light irradiation. The heterogeneous photoelectrocatalysis and the homogeneous electro-Fenton reaction simultaneously occurred in one reaction system, while H2O2 was produced by a two-electron reduction of oxygen and the ferrous ion was supplied by the dosing or electrogeneration method. In the photo-electro-integrated oxidation reaction system, both the degradation rate and the removal ratio of total organic carbon were enhanced for orange-G dye which was ascribed to interactive oxidation processes of photoelectrocatalysis, electro-Fenton and electrooxidation reaction. Ion chromatogram results indicate that the total mineralization reaction was much delayed to produce inorganic ions and groups although the complete decolorizing degradation could be achieved for orange-G dye.