In Situ Fenton Reagent Generated from TiO2/Cu2O Composite Film: a New Way to Utilize TiO2 under Visible Light Irradiation

Abstract

TiO₂/Cu₂O composite is prepared by a simple electrochemical method and coated on glass matrix through a spraying method. The obtained composite is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of TiO₂/Cu₂O composite films with different ratio of TiO₂ and Cu₂O on photodegradation of the dye methylene blue under visible light is investigated in detail. It is found that the photocatalytic activity of TiO₂/Cu₂O composite film with the presence of FeSO₄ and EDTA is much higher than that for the similar system with only TiO₂ and Cu₂O film respectively. Without the presence of FeSO₄ and EDTA, there is no degradation for methylene blue. The exploration of the optimized parameters for the degradation of methylene blue by using TiO₂/Cu₂O composite film as catalyst under visible light was also carried out. The most significant factor is the amount of TiO₂ in the composite, and the second significant factor is the concentration of FeSO₄. During the degradation of methylene blue under visible light, TiO₂/Cu₂O composite film generates H₂O₂, and Fenton regent is formed with Fe²⁺ and EDTA, which is detected in this study. The mechanism for the great improvement of photocatalytic activity of TiO₂/Cu₂O composite film under visible light is proposed by the valence band theory. Electrons excitated from TiO₂/Cu₂O composite under visible light are transferred from the conduction band of Cu₂O to that of TiO₂. The formed intermediate state of Ti ³⁺ ion is observed by X-ray photoelectron spectroscopy (XPS) on the TiO₂/Cu₂O composite film. Additionally, the accumulated electrons in the conduction band of TiO₂ are transferred to oxygen on the TiO₂ surface for the formation of O^2- or O₂^2-, which combines with H⁺ to form H₂O₂. The evolved H₂O₂ with FeSO₄ and EDTA forms Fenton reagent to degrade methylene blue. Compared to the traditional Fenton reagent, this new kind of in situ Fenton reagent generated from TiO₂/Cu₂O composite film does not need to supply H₂O₂. It is expected to be easily recycled, which may reduce second pollution and the cost of wastewater treatment. Moreover, this TiO₂/Cu₂O composite film with FeSO₄ and EDTA provides a new way to take advantage of TiO₂ under visible light.