Research Of The Preparation Process And Use Behavior Of Nano-TiO₂ Photocatalyst

It is well known that TiO2 has been widely used in the field of photocatalysis, solar cells, purification of water and air, because of its chemical stability, nontoxicity, and anti-photocorrosion, low cost and other advantages. Hence, nano-TiO2 photocatalyst has important effect and extensive prospect in the improvement of environmental pollution and energy development. However, the wide band gap of TiO2(Anatase ~ 3.2eV, Rutile ~3.0eV) leads to its light absorption only account for 3% ~5% of sunlight, which greatly hinders the quantum yield of TiO2. Thus, it is meaningful to improve the photocatalytic activity of TiO2 under visible light irradiation to overcome its limitation.In this study, according to change the conditions of annealing process, such as treating atmosphere, duration of ventilation, especially alter the annealing sequence in NH3 and H2; we obtained a series of nano-TiO2 photocatalyst, named as H-TiO2,N-TiO2,N-H-TiO2, and H-N-TiO2 respectively. After that, we made a thorough inquiry in the difference of structure, composition, light absorption and defects of TiO2 samples prepared by different processes, and then explained the experimental phenomena by characterizations and discussion. The testing parameters in the photocatalytic process, like the dosage of Ti O2 photocatalyst and the initial concentration of benzene, also have been investigated to study their effects in practical application. Cycle test of visible light activity of N-H-TiO2 was also conducted to access its stability.In this study, for the first time, we have investigated the preparation and behavior of TiO2 photocatalyst from a new prospective. The photocatalytic activity test shows that benzene with the concentration of 200 ppm can be completely decomposed by 100 mg N-H-TiO2 photocatalyst in 3 hours under visible light irradiation, which behaves better than H-N-TiO2, H-TiO2 or N-TiO2 obtained by annealing in H2 then NH3 or treated in H2 or NH3. The origin of the distinct photocatalytic performance of N-H-TiO2 and H-N-TiO2 could be attributed to the different annealing order of NH3 and H2.It was demonstrated that the amazing photocatalytic activity of N-H-TiO2 under visible light irradiation can be attributed to comprehensive effect of the highcrystallinity, small particle size, strong light absorption, fast separation of photo-generated carriers, and strengthened surface adsorption capability induced by the special surface structure and oxygen vacancies. In addition, the different annealing order of NH3 and H2 also contributed to the distinct concentration and position of nitrogen-doping species in N-H-TiO2 and H-N-TiO2 photocatalyst. The visible light activity as well as the mineralization rate of TiO2 increase with the extension of hydrogenation time. Furthermore, N-H-TiO2 exhibits substantial activity and stability which will produce great practical value in the future.