| Photocatalysis is a promising catalytic method. In many semiconductor photocatalysts, titanium dioxide(TiO2) has been rapidly developed in recent years for possessing characteristics such as high photocatalytic activity, non-toxic, non-pollution, low cost and so on. The traditional preparation method requires high temperature calcination, easy to cause a variety of adverse effects and consumes large amounts of energy. Besides, the band gap of TiO2 is relatively wide, thus requiring ultraviolet light to stimulate, and having almost no response to the dominant visible light in the sunlight.In order to solve these two major problems, NCC was put forward as crystal inducing agent to promote the crystallization and crystal growth of TiO2 precursor, eventually synthesized high-crystallinity TiO2 without high temperature treatment. Two kinds of preparation methods were used, by which the effect of different dosage of the precursor on the morphology, structure and photocatalytic activity of the catalyst was separately studied. The more optimal preparation method was selected to further dope nitrogen in the catalyst. The main research contents and conclusions were as follows:A series of TiO2/NCC composits were prepared by hydrolysis precipitation method with TiCl4 at the reaction temperature of 70℃. The catalyst prepared by this method showed spherical structure, formed by nanocrystalline cellulose and anatase phase TiO2 as well as a small amount of rutile phase TiO2, which were well crystallized. There existed Ti-O-C bond between TiO2 and NCC. The catalytic performance under UV light increased first and then decreased with the increase of the amount of TiCl4.A series of TiO2/NCC composites were prepared using sol-gel method with Ti(OC4H9)4 at the reaction temperature of 40℃. The catalyst synthesized by this method was spherical agglomeration as well, with more cracks on the surface. The agglomerate size was smaller and more uniform. TiO2 were mixed crystals of anatase and rutile with high degree of crystallinity, and interacted with NCC by Ti-O-C chemical bond. The samples showed good catalytic activity under UV light, and the degradation efficiency of the samples all surpassed P25. With the increase of the amount of Ti(OC4H9)4, the catalytic activity increased first and then decreased.After comparison of these two kinds of preparation methods, sol-gel method with tetrabutyl titanate as precursor was chosen, by which a series of N-doped catalysts were prepared using concentrated ammonia as nitrogen source under the reaction temperature of 40℃. The catalysts prepared showed a honeycomb like structure with high specific surface area, consisted of both nanocystalline cellulose and TiO2 crystals. TiO2 was mainly composed of rutile with high degree of crystallinity and interacted with NCC by Ti-O-C chemical bond. In the photocatalytic test, the catalysts exhibited excellent catalytic avtivity under UV light, and were able to respond to visible light. All samples performed far beyond P25. The photocatalytic efficiency roughly increased with the increase of ammonia dosage. The reasons for the remarkable improvement of photocatalytic property were the excellent morphology which improved the catalyst utilization efficiency and the lattice structure modification caused by nitrogen doping. |
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