| At present, environmental pollution and energy shortage have been increasingly clamping down our sustainable development strategy owing to the over-exploitation. To solve this problem, millions of people and researchers from all fields carried out varieties of work and showed great interests in solar photocatalytic oxidized degradation for its rapid degradation rate, non-second pollution, abundant energy. Among all semiconductor oxides, TiO2 is the most extensively studied and applied material in environmental pollution control owing to the strong oxidization, non-toxic property and outstanding chemical stability. Nevertheless, on account of its wide band gap of 3.2eV, the application of TiO2 as catalysis has been limited merely to ultraviolet light which only takes a 3% to 4% proportions out of the sunlight. On the other hand, high recombination rate of photogenerated electron-hole pair results in inefficient use of energy absorbed and further more restricts its realistic application.In this paper, N-TiO2-U was prepared via calcining the mixture of nanotube titanic acid (NTA) and urea. XRD and HRTEM illustrated the sample turned out a tubular structure of anatase TiO2 from 300℃to 600℃, yet the peak of rutile became equal to that of anatase when the sample was calcined at 700℃. Indicated by UV-Vis absorption, sample calcined at 500℃exhibited a highest UV-Vis absorption. NTA directly collapsed into TiO2, a great number of SETOV were created. The reaction equation are as follows: H2Ti2O5·H2O+ x NH3→(NH4)xH2-xTi2O5·H2O +(x -1)H2O ( 0≦x≦2 ,100℃) (NH4)xH2-xTi2O5·H2O→TiO2-xNy+ (x-y) NH3 + n H2O+ mVo·(0≦y≦x,>150℃) The WETOVS give rise to a better UV-Vis absorption. However, the absorption does not induce higher photocatalytic of degredation MB, the concrete reason was subject to further study.NTA was mechanical mixed with ammonium bicarbonate and then calcined at different temperatures, and then nano N-TiO2 with high photocatalytic activity was obtained. X-ray diffraction (XRD) and high-resolution electron microscopy (HRTEM) showed that sample still remained tubular amorphous under 400℃, and shifted to tubular anatase from 400℃to 600℃. As the temperature rise up to 700℃, the sample changed into particles with little rutile phases. Only the presence of interstitial N-doping and formation Ti-O-N bond as measured by XPS. With increasing temperature, the intermediate (NH4)2Ti2O4(OH)2 was formed. (NH4)2Ti2O4(OH)2 not only slowly release atom N to result in well-distributed interstitial N-doping was but also induce more oxygen vacancies during temperature rise process, As a result, its UV-Vis absorption was considerable, Meanwhile, intermediate (NH4)2Ti2O4(OH)2 was be propitious to remain the pretty tubular morphology of sample at 500℃and yielded better crystal. What's more, oxygen vacancies concentration was moderate, bringing about its photocatalytic activity 30% higher compared to non-doped sample.By comparing the process and photocatalytic activity of two kind of N precursor, we found that the photocatalytic activity of N-TiO2-A was better than N-TiO2-U. But N-TiO2-U presented a stronger absorption in visible light region, which can be contributed to more oxygen vacancies formed when NTA collapse to TiO2. The N-TiO2-U didn't show a higher photocatalytic activity, the reason of which should be studied furthermore. In addition, (NH4)2Ti2O4(OH)2 not only slowly release atom N to result in well-dispersed interstitial N-doping but also induce more oxygen vacancies during temperature rise process. Meanwhile, the intermediate is the benefit to preserving well-preserved tubular structure and better crystal of the sample, which caused a higher photocatalytic activity of MO degradation on N-TiO2-A.
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