Different Nitrogen Was Doped With Nano-titanium Dioxide Comparative Study

TiO2 is actived only by irradiating with ultraviolet light due to its large band gap of 3.2 eV, corresponding to wavelengths shorter than 388 nm. This means that TiO2 could make use of only a small fraction (~5%) of the sun's energy compared to the visible region (45%). So it is important to look for a method that can shift the optical response of TiO2 and make it be able to photocatalyze oxidation of organic in low energy light such as visible light.An effective approach to shifting the optical response of TiO2 from the ultraviolet to the visible spectral range is the doping of TiO2 with nonmetal nitrogen. In this paper,N-doped TiO2 photocatalysts, which can respond to visible light, were prepared by a sol–gel procedure using urea and chloride as nitrogen source. The structural and photoelectric properties of such photocatalyst were characterized by XRD, DSC, elemental analyzer and XPS.The results showed: (1) The N-doped TiO2 had obviously visible-light-activity. When urea is used as nitrogen source , under the conditions of the pH of sol was 1.3, the N/Ti proportioning was 35% and the calcination temperature was 500℃, the N-doped TiO2 could decompose 4-chlorophenol best under visible light,and the degradation ratio is 55.3%. When chloride is used as nitrogen source , under the conditions of the pH of sol was 2.6, the N/Ti proportioning was 35% and the calcination temperature was 500℃, the N-doped TiO2 could decompose 4-chlorophenol best under visible light,and the degradation ratio is 40.4%.(2) The pH of sol, content of N and calcining temperature had important effect on the crystal phase and particle size of N-doped TiO2.The higher or lower pH value and the content of N all leads to a lower visible-light activity.(3)The results showed that the crystal structure of N/TiO2 calcination at 400~500℃were all anatase, ehich was maturity with increase of calcinations temperature, and changed into rutile at 600℃. The crystal structure of N/TiO2 calcination at 800℃were all rutile. But, when chloride is used as nitrogen source, the particle size and rutile content are all bigger than the catalyst using urea as nitrogen source.(4)The samples prepared in the above two experiments ,N1s owns binding energy at 399.3 eV and 399.6eV, suggest that some N atoms substitute O atoms in TiO2 lattice.(5) The same material has some different degradation effect at different pollutants. This material had a higher visible- light photocatalytic activity in the decolouration of methylene blue than the formaldehyde , methyl orange and p-chlorophenol. As far as the same pollutants, the degradation rate of TOC is obviously lower than that of pollutants itself. The pollutants can not be mineralized. The kinetics of p-chlorophenol degradation reaction can be described by Langmuir- HinsheLlwood model.