Synthesis of NaOH-modified TiOF2 and its enhanced visible light photocatalytic performance on RhB

Abstract

NaOH-modified TiOF2 was successfully prepared using a modified low-temperature hydrothermal method. Scanning electron microscopy shows that NaOH-modified TiOF2 displayed a complex network shape with network units of about 100 nm. The structures of NaOH-modified TiOF2 have not been reported elsewhere. The network shape permits the NaOH-modified TiOF2 a SBET of 36 m2·g-1 and a pore diameter around 49 nm. X-ray diffraction characterization shows that TiOF2 and NaOH-modified TiOF2 are crystallized with a pure changed cubic phase which accords with the SEM results. Fourier transform infrared spectroscopy characterization shows that NaOHmodified TiOF2 has more O-H groups to supply more lone electron pairs to transfer from O of O-H to Ti and O of TiOF2. UV-vis diffuse reflectance spectroscopy (DRS) shows that the NaOH-modified TiOF2 sample has an adsorption plateau rising from 400 to 600 nm in comparison with TiOF2, and its band gap is 2.62 eV, lower than that of TiOF2. Due to the lower band gap, more O-H groups adsorption, network morphologies with larger surface area, and sensitization progress, the NaOH-modified TiOF2 exhibited much higher photocatalytic activity for Rhodamine B (RhB) degradation. In addition, considering the sensitization progress, O-H groups on TiOF2 not only accelerated the degradation rate of RhB, but also changed its degradation path. As a result, the NaOH-modified TiOF2 exhibited much higher photocatalytic activity for RhB degradation than the TiOF2 in references under visible light. This finding provides a new idea to enhance the photocatalytic performance by NaOH modification of the surface of TiOF2.