Improve the Photo-Activity of TiO2 from a Dual Modification via Tungsten-Doping and Fluorination

Abstract

Transition metal doping is a proven feasible and practical modification technique to extend the absorption range of TiO2 from ultraviolet to visible light while retard the recombination of photogenerated electron and hole and facilitate rapid interfacial charge transfer. Surface modification also greatly influence the adsorption and reaction rate. Fluorination has become one of the most effective methods for surface acidification due to the strong electronegativity of fluorine. The ≡Ti-F group transfers electrons to the O atoms on the surface of fluorinated TiO2 to capture photoelectrons. The general modification approaches utilizing insoluble tungstic acid or highly toxic hydrofluoric acid to improve charge separation and transfer in TiO2 result in considerable issues such as uneven doping, significant impact on morphology and size, as well as serious environmental hazards. In this work, we have developed an environmental benign simple one-pot dual-modification approach that using sodium tungstate of high solubility and trace-level sodium fluoride as replacements. The combined characteristic analyses and density functional calculation (DFT) suggest that the remarkable improvement of the photo-activity of TiO2 can be attributed to the rapid charge separation and transfer due to the bandgap narrowing from tungsten doping and localized spatial charge separation from fluorination.