| Recent years, the housing conditions have been improved and decorate materials have been widely used. However, the pollution problem caused by volatile organic compands (VOCs), which are released from decorate materials, become serious increasingly. The photocatalytic technology is the most promising one in the current VOCs goverance solution. Formaldehyde and benzene are the main indoor pollution introduced by decorating materials. It is easy to increase the risk of diseases such as cancer and luekimia when people expose in the pollution for a long time. Formaldehyde has the simplest molecular structure, but it is released slowly. Benzene is very stable and difficult to be decomposed due to its ring’s structure which contains delocalized π chemical bond. In present investigation, many problems exist in the degradation of formaldehyde and benzene by TiO2nano photocatalyst, including low initial concentration of benzene, high consumption of photocatalyst, long duration of photocatalytic reaction and photocatalyst deactivation. In addition, it rarely studies how to decompose formaldehyde in special environment such as in the night time or in the submarine. In order to solve above problems, we have prepared two kinds of nometal doped TiO2nanomaterials. Meanwhile, the degradation of formaldehyde without light irradiation at room temperature and the degradation of high concentration of benzene under visible light illumination have been investigated, the results show below:1. We used ammonia as nitrogen source, and the doping site of nitrogen atom was controlled successfully by adjusting the calcination atmosphere. As a result, the oxygen played important role in the doping site of nitrogen atom located in lattice. At the same calcination temperature, the nitrogen atom occupied the substitutional site and interstitial site of the obtained TiO2which was annealing in ammonia. When oxygen was added in the annealing process, the nitrogen atom only occupied the interstitial site. The degradation of benzene on the prepared samples under visible light illumination displayed that the photocatalytic activity of substitutional nitrogen doped TiO2was2-fold higer than that of interstitial nitrogen doped TiO2due to the interstitial nitrogen atom tended to be recombination center.2. A modular method to prepare TiO2nanomaterial with high visible light driven photocatalytic activity was proposed. The effect of various factors such as temperature, calcination order and calcination time on photocatalytic activity was investigated. The most active sample was prepared by annealing in ammonia for2hours firstly, then in vacuum for2hours at600℃. The enhanced photocatalytic activity was attributed to strong light harvesting, fast speration of electrons and holes and more surface electron scavengers. The conversion of phenol is the rate limiting step of degradation of benzene.3. The modified TiO2nanomaterial which can decompose formaldehyde without light irradiation at room temperature was prepared by annealing in hydrogen. The synergetic effect between carbon dopant and oxygen vacancy was not obvious without light irradiation. The mechanism of decomposing formaldehyde without light irradiation was ascribed to the oxygen vacancy, which enhanced the electron concentration of TiO2. The oxygen adsorbed on surface was transformed into active oxygen radical anion, which could react with formaldehyde.4. The hierarchical porous TiO2nanotube was prepared by hydrothermal method. We found that when we used solid TiOSO4as precursor, the obtained TiO2was tubular structure, and the structure evolution with reaction time displayed that the structure was tunable from rod, rod in tube, to tube. However, the liquid precursor either tetrabutyl titanate or TiOSO4was used, the obtained TiO2was sphere structure and the evolution of structure showed the same trend, from solid, sphere in sphere to hollow. We also compared the photocatalytic property towards degradation of benzene under UV light irradiation of all samples with different morphology. It showed the photocatalytic activity of TiO2with rod in tube structure was4-fold higher than that of TiO2with sphere in sphere structure. That was because the rod in tube structure had larger specific surface area and low recombination of electrons and holes. |
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