The ClO⋅ generation and chlorate suppression in photoelectrochemical reactive chlorine species systems on BiVO4 photoanodes

Photoelectrochemical generation of reactive chlorine species (PEC-RCS) is a promising approach for wastewater treatment. However, the inevitable byproduct of harmful oxychloride (such as ClO3- and ClO4- ) severely limits the practical applications of full-spectrum solar-driven PEC-RCS systems. Herein, we investigated three typical photoelectrodes including TiO2, WO3 and BiVO4 for PEC-RCS system and the formation of RCS and toxic oxychlorides. In BiVO4 photoelectrochemical cell, the concentration of ClO3- was lower than 0.2 mg/L and the ClO4was undetectable within 2 h of reaction. In contrast, the concentrations of ClO3- were 2.3 mg/L and 2.7 mg/L in the widely used WO3 and TiO2 PEC-RCS processes, respectively, which exceeded the health standard of 0.7 mg/L raised by the European Food Safety Authority (EFSA). We proposed that the valence band dependent photoelectrochemical properties of BiVO4 photoelectrodes could lead to the restricted HO radical production and the non-HO-mediated RCS generation, which synergistically inhibited the ClO3- formation in the RCS activation process.

Automated summary

This study investigated three typical photoelectrodes for PEC-RCS systems and found that BiVO4 demonstrated superior performance in inhibiting the formation of harmful oxychlorides compared to TiO2 and WO3. By utilizing valence band dependent photoelectrochemical properties, BiVO4 could effectively restrict the production of ClO3- and ClO4-, making it a promising candidate for PEC-RCS applications.