Preparation of TiO2-based catalysts with supercritical fluid technology: characterization and photocatalytic activity in CO2 reduction

BACKGROUNDTitanium dioxide is the photocatalyst par excellence in environmental applications. Nevertheless, over the years various methods aiming to improve its efficiency have been presented. Herein, we report that TiO2 synthesis in supercritical medium can result in a significant enhancement in the rate of CO2 photocatalytic conversion. RESULTSSpecifically, catalysts obtained from two titanium precursors (titanium tetraisopropoxide and diisopropoxititanium bis(acetylacetonate)) and two alcohols (ethanol and isopropyl alcohol) by hydrothermal synthesis in supercritical CO2 are shown to exhibit improved properties in comparison with the standard reference catalyst (Degussa P-25, Evonik). CONCLUSIONIn particular, upgraded characteristics are related to reactants adsorption (higher specific surface areas, presence of surface hydroxyl groups), light absorption and excitation (better absorbance in visible range, lower band gap energy), and charge separation (appropriate morphology and crystallinity). Furthermore, when these catalysts are tested in the photocatalytic reduction of CO2, CO and CH4 production rates 3- and 15.7-fold higher than those corresponding to the commercial catalyst have been found. (c) 2016 Society of Chemical Industry