Photocatalytic hydrogenation and reduction of CO2 over CuO/ TiO2 photocatalysts

Photocatalytic hydrogenation of carbon dioxide is one of the promising technologies which can convert carbon dioxide under ambient condition to sustainable fuels, such as methane and methanol. The pure TiO2 and copper doped TiO2 photocatalysts with 1, 3 and 5 wt.% CuO were prepared by sol-gel processing within reverse micelles and characterized by N2 physisorption, UV–Vis, XRD, TPR, Raman spectroscopy, photoelectrochemical measurement and analysis of work function. Two types of experimental photocatalytic hydrogenation and reduction of CO2 in the liquid phase and gas phase, respectively, were carried out under hydrogen. In the case of reaction in liquid phase, the highest yield of CH4 was found in the presence 5 wt.% CuO/TiO2 and pure TiO2. Activity of photocatalysts was affected mainly by two factors: the availability of active sites (SBET) and the work needed to move the electron from surface (work function). In gas reaction, the most CH4 and CO were generated in order: TiO2 > 3 wt.% CuO/TiO2 > 5 wt.% CuO/TiO2 > 1 wt.% CuO/TiO2. In the gas phase, the enhanced photocatalytic performance was connected with better separation of the generated charge carriers.