Photocatalytic Degradation of RhB by Fluorinated Bi2WO6 and Distributions of the Intermediate Products

Abstract

Fluorinated Bi₂WO₆ catalyst was synthesized by a simple hydrothermal process. The effects of fluorine doping on crystal structure, optical property, photoinduced hydrophilicity, surface acidity, and photocatalytic activity of the as-prepared sample were observed in detail. Fluorinated Bi₂WO₆ presented the enhanced photoactivity for the RhB degradation under the simulative sunlight (λ > 290 nm), which could be a synergetic effect of the surface fluorination and the doping of crystal lattice. To get a better handle on the mechanistic details of this photocatalytic system, the photodegradation process of RhB was examined. In the fluorinated Bi₂WO₆ system, five intermediates, namely, N,N-diethyl-N′-ethylrhodamine, N,N-diethylrohodamine, N-ethyl-N′-ethylrhodamine, N-ethylrhodamine, and rhodamine were thus identified, whereas the first three intermediates could only be identified in the case of the Bi₂WO₆ system. This result indicated that more RhB molecules were degraded via the deethylation process in the fluorinated Bi₂WO₆ system. It was proposed that the F⁻-containing function on the catalyst surface could serve as an electron-trapping site and enhance interfacial electron-transfer rates by tightly holding trapped electrons. On the basis of the experimental results, a photocatalytic mechanism was discussed in detail.