Photoelectrocatalytic degradation of 4-chlorophenol at Bi2WO6 nanoflake film electrode under visible light irradiation

To efficiently utilize the solar light and improve the photooxidation technique for wastewater purification, a new type of photoelectrode, visible light responsive Bi2WO6 nanoflake film, was covered onto the indium-tin oxide glass substrate via the electrostatic self-assembly deposition. The photocatalytic oxidation, electro-oxidation, and photoelectrocatalytic (PEC) oxidation of 4-chlorophenol (4-CP) in aqueous solution using the film electrode were investigated and compared under visible light irradiation (lambda > 400 nm). The experimental results demonstrated that 4-CP could be degraded by the nanotlake film under visible light irradiation or by applying a bias potential greater than 0.8 V. Based on X-ray photoelectron spectra (XPS) analysis of the electrode after electrochemical reaction, the electropolymerization was suggested to occur in the electro-oxidation process. Furthermore, degradation efficiency of 4-CP was largely increased by combined electro-oxidation and photocatalysis. And, it is the largest at the bias potential of 2.0 V. The characteristics of the PEC degradation of 4-CP were also investigated by electrochemical impedance spectroscopy (EIS). It is shown from the EIS that the PEC degradation appears to be a simple reaction on the electrode surface, suggesting that only one step of charge transfer is involved in the electrode process. The total organic carbon analysis indicated that 4-CP could be efficiently mineralized during the PEC process. (c) 2006 Elsevier B.V. All rights reserved.