New Way for CO2 Reduction under Visible Light by a Combination of a Cu Electrode and Semiconductor Thin Film: Cu2O Conduction Type and Morphology Effect

How to take advantage of CO2 has been one of the main issues to be addressed around the world. Although there are many methods to convert CO2 to organic fuel, the efficiency is still not high enough for practical application. Herein, we have accomplished better conversion of CO2 by the combination of metal electrode and semiconductor thin films responsive to visible light. First, the deposition of p-type and n-type Cu2O thin films onto a Cu substrate is successfully achieved. Then, the prepared Cu/Cu2O samples are used for catalytic reduction of CO2 in photoelectrochemical systems in comparison with that in photochemical and electrochemical systems. The results show that CH4 and C2H4 are the major hydrocarbon gas products, and the prepared Cu/Cu2O samples have much higher selectivity for C2H4 formation compared with the pure Cu electrode. The best yield for CO2 reduction is obtained in the photoelectrochemical system under visible light. Additionally, CO2 conversion efficiency over the Cu/Cu2O (p-type) electrode is much higher than that over Cu/Cu2O (n-type) with similar morphology. The morphology of Cu2O has an effect on the CO2 reduction activity in the photoelectrochemical system as well. The related mechanism is discussed in detail especially for the reaction in the beginning 15 min. The study will provide us a new way to utilize solar light for efficient conversion of CO2 into organic fuel.