Preparation, characterization and photocatalytic performance of TiO2 prepared by using pressurized fluids in CO2 reduction and N2O decomposition

TiO2 photocatalyst was prepared unconventionally, using the sol–gel process controlled within the reverse micelles and the processing by pressurized hot fluids as an alternative to standard calcination. Conventional calcined TiO2 was prepared as well. Textural, microstructural and optical properties of prepared photocatalysts were characterized by using nitrogen physisorption, powder X-ray diffraction and DR UV–Vis spectroscopy. The photocatalytic properties of developed TiO2 catalysts were investigated in the photocatalytic reduction of CO2 and photocatalytic decomposition of N2O. It was revealed that TiO2 processed by pressurized hot fluids shows significantly improved textural properties and different crystallinity compared to its calcined analog. Yields of both reaction products (H2 and CH4) of CO2 photoreduction were higher for the extracted TiO2 photocatalyst. The same result was achieved in N2O photodecomposition. The maximum N2O conversion (83 % after 20 h of illumination) in inert gas was reached also over the TiO2 extracted photocatalyst, and it can be attributed to simultaneous N2O photocatalytic decomposition and N2O photolysis. Reaction kinetics of N2O-photoinduced decomposition was described well by the pseudo-first-rate law. The surface heterojunction of bicrystalline anatase–brookite phase corresponded to better catalytic activity of TiO2 processed by pressurized hot fluids in both reactions, in a consequence of reduced electron–hole pair recombination.