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

Photoelectrocatalytic reduction of CO2 to fuels has great potential for reducing anthropogenic CO2 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 CO2 to methanol,comprising a copper catalyst modified with flower-like cerium oxide nanoparticles(CeO2 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 CeO2 NPs/CuO NPs/Cu catalyst yielded methanol at a rate of 3.44μmol cm^−2 h^−1,which was approximately five times higher than that of a CuO NPs/Cu catalyst(0.67μmol cm^−2 h^−1).The carrier concentration increased by^108 times when the flower-like CeO2 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 CeO2,which enhanced both photocatalytic and photoelectrocatalytic CO2 reduction on the CeO2 NPs.The facile migration of photoexcited electrons and holes across the p–n heterojunction that formed between the CeO2 and CuO components was thus critical to excellent light-induced CO2 reduction properties of the CeO2 NPs/CuO NPs/Cu catalyst.Results encourage the wider application of composite semiconductor electrodes in carbon dioxide reduction.