Low Temperature Preparation Of Mesoporous Carbon-Doped Crystalline TiO₂ And Its Characterization

The application of titanium dioxide as a heterogeneous photocatalyst is attracting considerable attention for water and air purification and remediation.Unfortunately, because of its large band gap of 3.2 eV,it can be activated only under UV light irradiation of wavelength＜387 nm,which constitutes only a small fraction(about 3-5%)of the solar spectrum.So it will have a positive effect for improving the photocatalytic efficiency of TiO₂ by shifting its optical response to the visible light.A visible-light-active carbon-doped TiO₂ photocatalyst was prepared by using glucose as carbon source and amorphous TiO₂ as titanium source,respectively.Different from the previous carbon doped TiO₂ prepared at high temperature,our preparation was performed by a hydrothermal method at temperature as low as 160℃.The resulting photocatalyst was characterized by XRD,XPS,TEM,nitrogen adsorption,and UV-vis diffuse reflectance spectroscopy.The characterizations revealed that the photocatalyst possessed a homogeneous pore diameter about 8 nm and a high surface area of 126 m²/g. Comparing to undoped TiO₂,the carbon doped TiO₂ shows obvious absorption in the 400-450 nm range with a red shift in the band gap transition.It is found that the resulting carbon doped TiO₂ exhibits significantly higher photocatalytic activity than the counterpart undoped TiO₂ and Degussa P25 on the degradation of rhodamine B(RhB)in water under visible light irradiation(γ＞420 nm).In order to find out the origin of visible light photocatalytic activity and the nature of carbonaceous species in the carbon doped TiO₂,we treated the photocatalyst with different methods and evaluated the photocatalytic activities of the resulting new catalysts.Through FT-IR spectrum and solid state C¹³-NMR spectroscopy characterization,we found that HCO₃^-,CO₃^2-ions and intermediate product of reduction of glucose coexisted in the catalysts.These carbonaceous species may be embedded within the TiO₂ matrixes to form Ti-O-C structures and act as photosensitizer,resulting in the high photocatalytic activity of our carbon doped TiO₂.