Highly Efficient Photoelectrocatalytic Reduction of CO2 to Methanol by a p–n Heterojunction CeO2/CuO/Cu Catalyst

Abstract Photoelectrocatalytic reduction of CO 2 to fuels has great potential for reducing anthropogenic CO 2 emissions and also lessening our dependence on fossil fuel energy. Herein, we report the successful development of a novel photoelectrocatalytic catalyst for the selective reduction of CO 2 to methanol, comprising a copper catalyst modified with flower-like cerium oxide nanoparticles (CeO 2 NPs) (a n-type semiconductor) and copper oxide nanoparticles (CuO NPs) (a p-type semiconductor). At an applied potential of − 1.0 V (vs SCE) under visible light irradiation, the CeO 2 NPs/CuO NPs/Cu catalyst yielded methanol at a rate of 3.44 μmol cm −2 h −1 , which was approximately five times higher than that of a CuO NPs/Cu catalyst (0.67 μmol cm −2 h −1 ). The carrier concentration increased by ~ 10 8 times when the flower-like CeO 2 NPs were deposited on the CuO NPs/Cu catalyst, due to synergistic transfer of photoexcited electrons from the conduction band of CuO to that of CeO 2 , which enhanced both photocatalytic and photoelectrocatalytic CO 2 reduction on the CeO 2 NPs. The facile migration of photoexcited electrons and holes across the p–n heterojunction that formed between the CeO 2 and CuO components was thus critical to excellent light-induced CO 2 reduction properties of the CeO 2 NPs/CuO NPs/Cu catalyst. Results encourage the wider application of composite semiconductor electrodes in carbon dioxide reduction.