Photocatalytic reduction of CO₂ to methanol by Cu₂ O/TiO₂ heterojunctions

The conversion of CO₂ 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 CO₂ under mild conditions. TiO₂ is not very effective for the photocatalytic reduction of CO₂ to low-carbon chemicals such as methanol (CH₃ OH). Thus, in this work, novel Cu₂ O/TiO₂ heterojunctions that can effectively separate photogenerated electrons and holes were prepared for photocatalytic CO₂-to-CH₃ OH. More visible light-active Cu₂ O in the Cu₂ O/TiO₂ heterojunctions favors the formation of methanol under visible light irradiation. On the other hand, under UV-Vis irradiation for 6 h, the CH₃ OH yielded from the photocatalytic CO₂-to-CH₃ OH by the Cu₂ O/TiO₂ heterojunctions is 21.0–70.6 µmol/g-catalyst. In contrast, the yield of CH₃ OH decreases with an increase in the Cu₂ O fraction in the Cu₂ O/TiO₂ heterojunctions. It seems that excess Cu₂ O in Cu₂ O/TiO₂ heterojunctions may lead to less UV light exposure for the photocatalysts, and may decrease the conversion efficiency of CO₂ to CH₃ OH.