Role of oxygen in copper-based catalysts for carbon dioxide electrochemical reduction

Abstract Among various studied catalysts, copper-based electrocatalysts can convert CO2 into hydrocarbons. Two main challenges in this research area are low selectivity, especially for value-added C2+ products and the high overpotentials required to initiate carbon dioxide reduction reaction (CO2RR). The interaction between copper and oxygen has always been inevitable in the design of copper-based catalysts owing to the intrinsic activity of copper and the oxygen-rich environment we live in. Recently, due to the unprecedented development of in-situ characterization, continuously increasing attention has been paid to oxygen species, which is usually accounting for the highest proportion of metalloid composition in copper-based catalysts. Herein, we have summarized the research progress on oxygen-containing copper catalysts, both experimentally and theoretically, and revealed the evolution of oxygen and the relationship between catalytic performance and oxygen species. It is found that the existence of subsurface oxygen in the electrochemical interface of copper-based electrodes has been proved both by in-situ characterization and theoretical simulation, which is also essential for efficient CO2RR to C2+ products. Additionally, selectivity to C2+ products is basically boosted in three ways: facilitating the conversion of CO2 from physical adsorption to chemical adsorption, strengthening intermediate binding and optimizing the adsorption configuration of CO2. It is expected that this review will provide clue for utilizing oxygen to enhance C2+ selectivity in the design of copper-based catalysts.