The Preparation And Photocatalytic Activity Of TiO₂ Photonic Crystals

Nowadays the whole world is focusing on environmental pollution issues. Relatively cheap TiO2 can remove these pollutants under ultra-violet radiation, without any poisoning by-products; thus it is now taking on more and more attentions. However, photo-catalyzed/oxidization technology still has many problems unsolved in the practical realization, for example, the electrons/vacuums produced by catalyzed TiO2 under light are very easy to recombine, leading to low efficiency and underperformed photo-canalization effect.Photonic crystal is special material with outstanding properties, among which the inverse-opal's photonic crystal structure possesses better specific surface area than normal nano TiO2, thanks to is porous structure. Therefore, we expect to fabricate this type of TiO2 catalysts, on one hand it is photonic crystal structured, on the other hand, the crustal type should be a combination of anatase and rutile. This structure has 3 advantages in comparing to nano-TiO2:1. bigger specific surface area; 2. bigger hole volume; 3. it is hetero-crystal. Big specific surface area is in favor of the absorption of more reagents on the surface of catalysts, and big hole volume can help to quickly diffuse all reagents and products during the catalyzing process, which facilitates the quicker decays of the organic. Moreover, some studies show, the compounding of two semi-conductors or two phases in one semiconductor are good for reducing the speed of the recombination of photo-produced electrons and vacuums, thus promote the activity of photo-catalysts.In this principle, the content of the thesis is trying to prepare TiO2 catalyst with special structure, and to test whether this special structure can improve its catalytic activity by doing the decomposition experiment. Using PS as raw material we successfully prepared colloidal crystal templates with several different PS radius, and infiltrated the TiO2 precursor into the PS colloidal crystal by sol-gel method, after aging and thermal treatment, the TiO2 inverse-opal photonic crystal material was successfully fabricated, and then tested the catalytic activity of TiO2 inverse-opal photonic crystal by decomposing methylene blue and methyl orange.The key point of our thesis is the preparation of PS colloidal crystals, the technique control of the infiltration of TiO2 precursor, the thermal treatment of composite and the test of the catalytic activity of TiO2 verse opal photonic crystal.From the result of the experiment, we can see that the special structure have enhanced the catalytic activity, and the enhancing mechanism needs further investigation.