The Study On Process And The Effect On Absorption Wavelength In Nitrogen-doped Nano Titanium Dioxide Powder

In the past few decades,titanium dioxide has drawn much attention from the industry as a good candidate for a large band-gap semiconducting oxide or optical semiconductor material for the photodecomposition processes in pollutant treatment because of its good physical and chemical properties,relatively inexpensive,high stability,efficient photocatalysis and non-toxic.TiO₂,however,is only photoactive under UV irradiation??<450?,which accounts for less than 5% of solar light energy.There have been various attempts dye sensitization,semiconductor coupling,and impurity doping with transition metals and non-metal elements.In an attempt to utilize visible light in a TiO₂ photocatalysis,the reduction in the bandgap energy of photocatalysts for photoexcitation is mainly focused on doping TiO₂ with both transition metals and non-metal impurities.Valentin et al.have reported that the positive and negative effects,which addressed the fact that transition metal doping decreases the bandgap energy of TiO₂,but the metal species would be the recombination centers and detrimental to the photocatalytic activity of the photocatalysts.Since then,many researchers have referred to the doping process in TiO₂ with non-metal species such as carbon?C?,sulfur?S?,fluorine?F?,and nitrogen?N?when considering a more effective approach to improve the photocatalytic activity of TiO₂ under visible light irradiation.The optimal preparation of N-TiO₂ photocatalysts by hydrolysis method and solid phase method.The photocatalytic activity of N-doped TiO₂ samples were obviously improved by test.The main content and viewpoints are as followed:?1?N-doped titanium dioxide is prepared using urea as the nitrogen source by hydrolysis method and solid phase method.After analysis,we found that the nitrogen source of nitrogen-doped TiO₂ is ammonia not is urea,and the hydrolysis of nitrogen-doped TiO₂ may be due to the small solubility of ammonia in water at high temperature,or the affinity of ammonia with water is greater than that with TiO₂ in water.Hydrolysis process is almost no doping,and mainly in the final sintering process for doping.It is found that solid phase method is more effective than hydrolysis.?2?N-doped TiO₂ was prepared at different calcination temperatures,different ratios,and different diameters by solid phase method using urea as the nitrogen source.UV-vis results indicate that the most apparent red shift of the absorption edge toward the visible light region for the prepared N-TiO₂ was achieved at 400? calcination temperature and at 5nm diameter TiO₂.