Abstract
A series of TiO2 photocatalysts loaded with various metals (Pt, Pd, Ni, and Cu) were prepared by using the wet impregnation method. Their physicochemical properties were studied by using XRD, BET, TPR-H2, FTIR and TPD-NH3/CO2 techniques. The photocatalytic activity of samples was investigated in the gas-phase reduction of carbon dioxide under continuous flow operation mode. Among all investigated catalysts, the Pt and Ni were the most active in terms of the formation rate of methanol. In general, the photocatalytic activity of modified TiO2 decreased with increasing metal loading and reaction time. The reversible deactivation of photocatalysts was associated with the covering of TiO2 surface by the reaction products.
Highlights
IntroductionThe process itself is similar to natural photosynthesis wherein C O2 and H2O are converted by plants to oxygen and carbohydrates
The photocatalytic conversion of carbon dioxide into valueadded chemicals is recognized as a promising approach to address both energy and environmental issues
– photoinduced charge recombination and transportation; – oxidation of water caused by the hole in the valence band; – reduction of C O2 caused by the electron in the conduction band; As a result, the carbon dioxide can be reduced to various chemicals, such as methane ( CH4), methanol ( CH3OH)
Summary
The process itself is similar to natural photosynthesis wherein C O2 and H2O are converted by plants to oxygen and carbohydrates. It basically consists of several steps which are [1]:. It is worth mentioning that the formation of CO2− species can occur without the illumination of the surface of photocatalyst but it significantly increases their concentration [4]. The another important step is the formation of electron–holes pairs when the light strikes the photocatalyst. The C O2− radicals can further be converted to CO
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