Fotokatalytická redukce CO2 na modifikovaném TiO2

Abstract

The dissertation thesis deals with the influence of titanium dioxide modification by cerium, platinum, cooper and graphitized carbon nitride on photocatalytic reduction of carbon dioxide. A total of 4 sets of photocatalysts were investigated. The first set consisted of cerium-doped photocatalysts, which were produced by sol-gel method followed by calcination. These photocatalysts contained 0.3 – 0.8 mol. % cerium. A second set of cerium-doped photocatalysts was prepared by sol-gel method followed by a high pressure treatment. Here, 0.6 – 5.5 wt. % cerium was used. The third set included photocatalysts modified with copper and platinum, which were prepared by sol-gel method. The photocatalysts were prepared with different contents of copper and platinum (0.5; 1 and 2 wt. %). One photocatalyst was prepared which contained both metals with 1 wt. % and all photocatalysts were compared with the TiO2 prepared in the same way. The last photocatalyst series consisted of TiO2/g-C3N4, which were prepared by heating of melamine followed by calcination of the mechanical mixture with TiO2. Photocatalysts were prepared in ratios: TiO2/g-C3N4 2/1; 1/1; 0.5/1; 0.3/1 and compared with commercial TiO2 (Evonik P25) and pure g-C3N4. The prepared photocatalysts were characterized by analytical methods: X-ray fluorescence spectroscopy, X-ray diffraction analysis, UV-Vis, physical nitrogen adsorption, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and photoelectrochemical spectrometry. The physicochemical properties of the used photocatalysts were found using the analytical methods and they were compared with their photoactivity in the reduction of carbon dioxide. The photocatalytic reactions were carried out in the presence of cerium, platinum and copper photocatalysts in a stirred batch reactor in the liquid phase. In the case of TiO2/C3N4photocatalysrs, a batch reactor was used which was saturated with wet CO2, and the reaction was in the gas phase. As the radiation source was chosen 8 W Hg lamp with a wavelength of 254 nm. The physicochemical properties of each of the most active photocatalysts of each set were compared to each other and commercial TiO2 Evonik P25. Furthermore, photoactivity of photocatalytic decomposition of CO2 in the liquid and gaseous phases were compared. All the most active photocatalysts exhibited higher activity than Evonik P25 in photocatalytic CO2 reduction.