Facile preparation of nitrogen and fluorine codoped TiO2 mesocrystal with visible light photocatalytic activity

摘要

N-doped TiO2 mesocrystal was prepared through simple hydrothermal treatment with triethanolamine, while F-doped TiO2 mesocrystal was easily prepared by simple stirring of TiO2 mesocrystal with NaF at room temperature. The crystal structure and surface area of TiO2 mesocrystal were not affected by the N- and F-doping. The prepared samples were characterized by X-ray diffraction (XRD), N-2 adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy. N,F-codoped TiO2 mesocrystal showed the highest photocatalytic activity for the degradation of Rhodamine B (RHB) and 4-nitrophenol (4-NP) under the visible light irradiation in 90% and 62% yield, respectively, suggesting the importance of the midgap level due to N 2p above the valence band, and the synergetic effect of N and F doping. Femtosecond time-resolved diffuse reflectance (TDR) spectroscopy was used to clarify the charge-separation, trapping and recombination mechanism, indicating an important role of F for increasing the photocatalytic activity. (C) 2016 Elsevier B.V. All rights reserved.