Photocatalytic Reduction of CO 2 to Methanol by Cu 2 O/TiO 2 Heterojunctions

The conversion of CO 2 to low-carbon fuels using solar energy is considered an economically attractive and environmentally friendly route. The development of novel catalysts and the use of solar energy via photocatalysis are key to achieving the goal of chemically reducing CO 2 under mild conditions. TiO 2 is not very effective for the photocatalytic reduction of CO 2 to low-carbon chemicals such as methanol (CH 3 OH). Thus, in this work, novel Cu 2 O/TiO 2 heterojunctions that can effectively separate photogenerated electrons and holes were prepared for photocatalytic CO 2 -to-CH 3 OH. More visible light-active Cu 2 O in the Cu 2 O/TiO 2 heterojunctions favors the formation of methanol under visible light irradiation. On the other hand, under UV-Vis irradiation for 6 h, the CH 3 OH yielded from the photocatalytic CO 2 -to-CH 3 OH by the Cu 2 O/TiO 2 heterojunctions is 21.0–70.6 µmol/g-catalyst. In contrast, the yield of CH 3 OH decreases with an increase in the Cu 2 O fraction in the Cu 2 O/TiO 2 heterojunctions. It seems that excess Cu 2 O in Cu 2 O/TiO 2 heterojunctions may lead to less UV light exposure for the photocatalysts, and may decrease the conversion efficiency of CO 2 to CH 3 OH.