Fotokatalytický rozklad oxidu dusného na tenkých filmech TiO2 připravených prostřednictvím různých sol-gel technik.

Abstract

This diploma thesis focuses on photocatalytic decomposition of nitrous oxide in presence of TiO2 catalysts prepared by various sol-gel techniques and having different number of applied layers. The aim of the thesis is to find out if an application of different preparation methods and different number of applied layers has an effect on photocatalytic decomposition of nitrous oxide. The thin layers of TiO2 were prepared by ZSG method (i.e. acidly catalyzed sol-gel process) and by MSG method (i.e. sol-gel process regulated in reverse micellar environment). Catalysts were prepared with three and four layers in both cases. The surface morphology and the roughness differences of particular types of the layers were studied by the method of atomic force microscopy. Optical properties of the layers were evaluated by UV-Vis spectroscopy and the layers thickness was evaluated by X-ray diffraction. Before the photocatalytic decomposition of nitrous oxide the photolytic decomposition of nitrous oxide (i.e. the reaction without the catalysts) was performed. The reaction was performed in two types of annular batch reactors, which differed by their geometry. The aim was to determine which geometry is more suitable for the photocatalytic decomposition of nitrous oxide. In the process of photolysis two different radiation sources – the 8 W Hg lamp with 254 nm wavelength and the 8 W Hg lamp with 365 nm wavelength were used. After the photolysis results evaluation the R3 reactor and the 365 nm wavelength lamp were used for subsequent activity measuring of prepared thin layers of TiO2. The activity of tested catalysts decreased in the order 3V MSG < 4 V MSG < 4V ZSG < 3V ZSG. It was obvious that the more active thin layers were those prepared by the process regulated in reverse micellar environment. Finally, it was found out that the process of photocatalytic decomposition of nitrous oxide is influenced by chosen method of catalyst’s preparation, by the number of the layers, by the reactor geometry and also by radiation source.