Enhanced photocatalytic removal of sodium pentachlorophenate with self-doped Bi2WO6 under visible light by generating more superoxide ions.

In this study, we demonstrate that the photocatalytic sodium pentachlorophenate removal efficiency of Bi2WO6 under visible light can be greatly enhanced by bismuth self-doping through a simple soft-chemical method. Density functional theory calculations and systematical characterization results revealed that bismuth self-doping did not change the redox power of photogenerated carriers but promoted the separation and transfer of photogenerated electron-hole pairs of Bi2WO6 to produce more superoxide ions, which were confirmed by photocurrent generation and electron spin resonance spectra as well as superoxide ion measurement results. We employed gas chromatography-mass spectrometry and total organic carbon analysis to probe the degradation and the mineralization processes. It was found that more superoxide ions promoted the dechlorination process to favor the subsequent benzene ring cleavage and the final mineralization of sodium pentachlorophenate during bismuth self-doped Bi2WO6 photocatalysis by producing easily decomposable quinone intermediates. This study provides new insight into the effects of photogenerated reactive species on the degradation of sodium pentachlorophenate and also sheds light on the design of highly efficient visible-light-driven photocatalysts for chlorophenol pollutant removal.