Synthesis, Characterization, and Nitrogen Concentration Depended Visible-Light Photoactivity of Nitrogen-Doped TiO2 Nanosheets with Dominant (001) Facets

Anatase TiO2 nanosheets with dominant (001) facets were prepared by a simple hydrothermal method. Nitrogen-doped TiO2 nanosheets (TiO2-N) with different nitrogen concentration were successfully synthesized by annealing TiO2 nanosheets in NH3 atmosphere with different NH3 flow rate at 400 degrees C for 3 h. The morphology, nanostructures, and properties of TiO2-N were characterized by X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, ultraviolet-visible diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence. The effects of NH3 flow rate on the nanostructures, properties, and visible-light photoactivity in the degradation of rhodamine B (RhB) aqueous solution under visible light (lambda>400 rim) irradiation of the prepared photocatalysts were investigated. Among all the prepared photocatalysts including nitrogen modified P25 (Degussa), TiO2-N prepared with a NH3 flow rate of 40 ml/min gave the highest visible-light photoactivity because of the dominant (001) facets, visible light responsibility, the slowest photogenerated electron (C) and hole (h) pairs recombination rate, and the highest hydroxyl radicle (center dot OH) generation ability. Based on these experiments and analysis, the mechanisms of how the nitrogen concentration affects the visible-light photoactivity of TiO2-N were proposed.