Iodine-doping-assisted tunable introduction of oxygen vacancies on bismuth tungstate photocatalysts for highly efficient molecular oxygen activation and pentachlorophenol mineralization

Abstract

In this work, the tunable introduction of oxygen vacancies in bismuth tungstate was realized via a simple solvothermal method with the assistance of iodine doping. With the predictions afforded by theoretical calculations, the as-prepared bismuth tungstate was characterized using various techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, electron spin resonance spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The different concentrations of the oxygen vacancies on bismuth tungstate were found to be intensely correlated with iodine doping, which weakened the lattice oxygen bonds. Owing to the sufficient oxygen vacancies introduced in bismuth tungstate as a result of iodine doping, the molecular oxygen activation was remarkably enhanced, thus endowing bismuth tungstate with high activity for the photocatalytic degradation of sodium pentachlorophenate. More encouraging is the total organic carbon removal rate of sodium pentachlorophenate over iodine-doped bismuth tungstate that exceeded 90% in only 2 h and was 10.6 times higher than that of the pristine bismuth tungstate under visible light irradiation. Moreover, the mechanism, through which the degradation of sodium pentachlorophenate over iodine-doped bismuth tungstate is enhanced, was speculated based on the results of radical detection and capture experiments. This work provides a new perspective for the enhanced photocatalytic degradation of organochlorine pesticides from the oxygen vacancy-induced molecular oxygen activation over iodine-doped bismuth tungstate.