Preparation Of N-Doped TiO₂Nanotubes And Its Photocatalytic Activity In Removing NO_x

As environmental issues become prominent increasingly, people’s consciousness of environmental protection strengthens gradually, as one of the major atmospheric pollutants, nitrogen oxides have attracted extensive attentions due to its numerous harm.At present, catalytic decompose and catalytic reduction are the prime processing technologies,but these technologies have some defects about high operating costs, high energy consumed and so on, whereas photocatalytic technology have a broad development prospects due to mild reaction conditions, low energy costs and little secondary pollution. At present, TiO2is the most efficient photocatalyst, But it only absorbs Ultraviolet light (about8%of solar light) because of its wide band-gap.Moreover,it lead to low Light quantum efficiency that high recombination rate of electrons and holes, All of these limits the application of TiO2in the actual greatly. TiO2nanotubes have a larger specific surface area, specific surface area, high stability,is a kind of special structure of TiO2. Studies have found that we can improve the response value of photocatalyst of nanotubes in the visible light region and reduce the risk of recombination of electrons and holes through the element doping modification.As a result, it will improve the visible light photocatalytic activity and potential application of TiO2greatly that modified TiO2nanotubes. TiO2nanotubes were synthetize using amorphous TiO2as raw material with the hydrothermal method in this study,in addition,we investigated the effect of hydrothermal time,hydrothermal temperature, temperature and time of calcination on nanotubes formation. The results of TEM show that:the length of nanotubes is60～160nm mainly, the diameter of the tube is7～15nm and the thickness of the wall is about1.5nm. we designed a Gas-solid catalytic reaction set,and investigated the effects of nitrogen oxides concentration and flow rate, moisture, oxygen content, catalyst load, particle size of the carrier on photocatalytic removal rate of NOx with the device.Non-metallic can introduce lattice oxygen vacancy in TiO2, or replace parts of oxygen vacancy to form TiO2-xAx(A represent non-metallic elements) crystal, reduce the width of forbidden band, thus broaden the range of light response. N-doped TiO2nanotubes were fabricated using the nanotubes of hydrothermal synthesis as raw material and NH4F as nitrogen source with impregnation method in this paper. Moreover, N-doped TiO2were fabricated using tetrabutyl titanate as titanium source and NH4F as nitrogen source with Sol-gel method,and then N-doped TiO2nanotubes were preparated using the TiO2as raw material with hydrothermal method. XRD results show that the calcined nanotubes are anatase almost; TEM results show that N-doped TiO2nanotubes have good tubular structure; DRS results show that N doped can reduce width of forbidden band of TiO2, lead to the obvious red shift of absorption spectra, as a result,it can enhances the response in the visible light region. Catalytic performance test results show that the sample with impregnation method mixed with15%ammonium fluoride and calcined in500℃for2hours showed the best degradation rate of NOx regardless of in ultraviolet or visible light, the degradation rate of NOx is95.73%under ultraviolet light and93.16%under visible light, respectively. The sample with Sol-gel hydrothermal method mixed with30%ammonium fluoride and calcined in500℃for2hours showed the best degradation rate of NOx regardless of in ultraviolet or visible light, the degradation rate of NOx is95.71%under ultraviolet light and93.04%under visible light, respectively.