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TiO2 as nanostructured powders were prepared by (1) sol-gel process and (2) hydrothermal method in combination with (A) the processing by pressurized hot water and methanol or (B) calcination. The subsequent synthesis step was the modification of prepared nanostructured TiO2 with nitrogen using commercial urea. Textural, structural, surface and optical properties of prepared TiO2 and N/TiO2 were characterized by nitrogen physisorption, powder X-ray diffraction, X-ray photoelectron spectroscopy and DR UV-vis spectroscopy. It was revealed that TiO2 and N/TiO2 processed by pressurized fluids showed the highest surface areas. Furthermore, all prepared materials were the mixtures of major anatase phase and minor brookite phase, which was in nanocrystalline or amorphous (as nuclei) form depending on the applied preparation method. All the N/TiO2 materials exhibited enhanced crystallinity with a larger anatase crystallite-size than undoped parent TiO2. The photocatalytic activity of the prepared TiO2 and N/TiO2 was tested in the photocatalytic reduction of CO2 and the photocatalytic decomposition of N2O. The key parameters influencing the photocatalytic activity was the ratio of anatase-to-brookite and character of brookite. The optimum ratio of anatase-to-brookite for the CO2 photocatalytic reduction was determined to be about 83 wt.% of anatase and 17 wt.% of brookite (amorphous-like) (TiO2-SG-C). The presence of nitrogen decreased a bit the photocatalytic activity of tested materials. On the other hand, TiO2-SG-C was the least active in the N2O photocatalytic decomposition. In the case of N2O photocatalytic decomposition, the modification of TiO2 crystallites surface by nitrogen increased the photocatalytic activity of all investigated materials. The maximum N2O conversion (about 63 % after 18 h of illumination) in inert gas was reached over all N/TiO2.

The aim of this study was to remove ammonia from an aqueous solution by its decomposition to valuable products such as H2 and harmless N2 under UV light. The decomposition of ammonia by photocatalytic process represents an emerging and interesting way of its removal since beside the need of its reduction from the drinking and wastewaters with the respect to its negative impact on human and mammals health, it can lead to generation of hydrogen as an alternative fuel. A laboratory-synthesized Pt/TiO2-ZrO2 photocatalyst was studied and its photocatalytic activity was compared with the activity of commercial TiO2 Evonik P25. The Pt/TiO2-ZrO2 photocatalyst was prepared by combining a sol-gel process controlled within reverse micelles of nonionic surfactant Triton X-114 in cyclohexane, impregnation under vacuum and calcination. Explored photocatalysts were characterized by organic elementary analysis, nitrogen physisorption, XRD, FESEM and UV-Vis spectroscopy. The real platinum content in the Pt/TiO2-ZrO2 photocatalyst was determined by ICP-MS. The photocatalytic decomposition of ammonia was investigated in the time range of 0-12 h. During the first two hours the generation of hydrogen was almost negligible. The generation of hydrogen increased after 4 h of irradiation. Based on time dependences of ammonia decomposition the kinetic rate constants for Pt/TiO2-ZrO2 and TiO2 Evonik P25 photocatalysts were calculated. The ammonia photocatalytic decomposition was described well by the first order kinetic equation. The photocatalytic ammonia decomposition over the platinized TiO2-ZrO2 photocatalyst was proving 2 times higher photocatalytic performance than Evonik P25 (1241 μmol/g(cat) and 665 μmol/g(cat), respectively).