Synthesis and photocatalytic activity of stable nanocrystalline TiO2 with high crystallinity and large surface area

Superior photoactive TiO2 nanopowders with high crystallinity and large surface area were synthesized by a hydrothermal process in the presence of cetyltrimethylammonium bromide and a post-treatment with ammonia. The prepared photocatalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption-desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectra (DRS) and surface photovoltage spectroscopy (SPS). The prepared nanocrystallites were highly resistant to thermal sintering, and the calcinations up to 900 °C were shown to enhance the crystallinity of the anatase phase without any rutile phase and the separation rate of photoinduced charges of TiO2 particles. It remained as large as 196 and 125 m2/g even after calcinations at 700 and 800 °C, respectively. The photocatalytic activity of prepared photocatalysts was obviously higher than that of commercial Degussa P25 on the photodegradation of methylene blue and phenol in water under ultraviolet-light irradiation, and the sample calcined at 800 °C afforded the highest photocatalytic activity.