Coexisting Chloride Ion for Boosting the Photoelectrocatalytic Degradation Efficiency of Organic Dyes

Photoelectrocatalytic (PEC) degradation of organic dyes molecules has been proved to be an effective strategy to remove organic dyes from environment and wastewater. However, improving the degradation efficiency so far is still a challenging. Here, a simple and stable photoanode based on TiO2 film on indium tin oxide (TiO2/ITO) was constructed and used for PEC degradation of methyl violet (MV), as an organic dye model. The influences of photoirradiation, applied bias voltage and types of electrolytes on PEC degradation of MV are mainly investigated. The results proves that the PEC degradation performance of TiO2/ITO system can be greatly enhanced by the applied bias voltage on photoanode and the presence of chloride ions. When using potassium chloride (KCl) as electrolyte, the degradation ratio of MV can reach to over 95% in 60 min with a bias voltage of 1.5 V (vs. Ag/AgCl), and a degradation rate constant of 0.053 min−1 can be achieved, which is 17 times higher than that using KNO3 as electrolyte (0.00305 min−1), indicating the applied bias voltage and Cl− play very important roles in the PEC degradation process. In addition, the mechanism for enhanced MV degradation based on applied bias voltage and Cl− was also studied in detail. This work opens the avenue for enhancing the PEC degradation of organic pollutants in aqueous solution, especially that with chloride ions contained, indicating its potential application in industrial dyeing wastewater treatment.Graphical AbstractThe photoelectrocatalytic (PEC) efficiency can be enhanced with the presence of Cl− and the PEC system also has good degradation effect on other dyes which indicating it has practical application potential.