A one-step synthesis procedure at elevated temperature was used to prepare Ti 3+ -containing blue titania. The prepared material was characterized by X-ray powder diffraction (XRD), UV−vis, Raman, and X-ray photoelectron spectroscopy (XPS), and N 2 adsorption and desorption measurements. The blue titania sample was found to be crystalline, with a surface area of 22 m 2 /g. Its phase composition consists of 85% rutile and 15% anatase with a multitude of defect surface V O -Ti 3+ sites. The blue titania showed an absorption red-shifted as compared to that of rutile, with a calculated bandgap of 2.93 eV. The photocatalytic performance of the blue titania was evaluated in the liquid phase selective photo-oxidation of methylcyclohexane (MCH) by illumination at 375 ± 10 nm (UV) and 425 ± 10 nm (visible light). The activity was monitored by attenuated total reflectance− Fourier transform infrared analysis. A high activity was observed for blue TiO 2 , remarkably equal in magnitude at both investigated wavelengths. The activity of the blue titania surpassed the activity of other (commercial) titania catalysts (rutile and P25), in particular at 425 nm, and the obtained selectivity for ketones was also greater. The activity data are discussed in relation to the properties of the three catalysts investigated, i.e., the texture, phase composition, and presence or absence of surface defects, of which the latter appears to be dominant in explaining the performance of the blue titania.

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The photocatalytic reduction of CO2 by water vapor to produce light hydrocarbons was studied over a series of catalysts consisting of variable loading of Ti incorporated in TUD-1 mesoporous silica, either modified by ZnO nanoparticles or isolated Cr-sites. Unexpectedly, the performance of ZnO-Ti-TUD-1 and Cr-Ti-TUD-1 was inferior to the parent Ti-TUD-1. An explanation can be found in experiments on the photocatalytic degradation of a mixture of hydrocarbons (i.e., CH4, C2H4, C2H6, C3H6, and C3H8) under the same illumination conditions. Ti-TUD-1 exhibits the poorest activity in hydrocarbon degradation, while ZnO-Ti-TUD-1 and Cr-Ti-TUD-1 showed very significant degradation rates. This study clearly demonstrates the importance of evaluating hydrocarbon conversion over photocatalysts active in converting CO2 to hydrocarbons (in batch reactors).