Selective alcohols production through CO2 photoreduction using Co3O4 /TiO2 photocatalyst exploiting synergetic interactions between Ti3+, Co2+ and Co3+

In general, CO2 photoreduction to produce alcohols has shown low conversion efficiency and low selectivity of the products. In this investigation, Co3O4/TiO2 photocatalysts were used for efficient alcohols production during CO2 photoreduction with H2O, using UV or visible light. Photocatalysts characterization by XPS, HTEM, and UV–vis spectroscopy suggested that the high activity of the photocatalysts for ethanol, propanol and iso-propanol production can be attributed to the presence of Ti3+, Co2+ and Co3+ which, decrease the TiO2 band-gap energy and the photogenerated electron-hole recombination probability. Ti3+, Co2+ and Co3+ improve adsorption of CO2 and of generated CO, on the photocatalyst surface, increasing the formyl-radical formation rate, which is the essential step for alcohols production. The effect of CO2 photoreduction factors, on alcohol production was evaluated, considering different cobalt concentrations and irradiance intensities, through a design experiment. Results revealed that cobalt concentration and irradiation intensity have a significant effect for the reaction.