Mechanistic Insights into Aldehyde Production from Electrochemical CO2 Reduction on CuAg Alloy via Operando X-ray Measurements

CO2 electrolysis convertsthe greenhouse gasCO(2) into valuable fuels and chemicals, such as carbon monoxide,ethylene, ethanol, etc. Currently, Cu is the onlyknown monometallic catalyst capable of producing multicarbon productsfrom electrochemical CO2 reduction reaction (eCO2RR), whilethe poor selectivity limits its further use. It has been found thatintroducing Ag atoms into the Cu lattice can modulate product preference.However, the synergistic effects between Cu and Ag, and thus, thecatalytic performance, are strongly influenced by catalyst morphology,electrolyzer configuration, reaction conditions, etc. Operando measurements can provide explicit informationon the catalyst dynamic variation during the reaction, but their operationand analysis are challenging. Herein, we prepared CuAg multiphasealloy catalysts by magnetron sputtering, which allowed for investigatingthe intrinsic interaction between Cu and Ag. eCO2RR performance exhibitedan improved selectivity toward carbonyls at the expense of hydrogenand hydrocarbons. The partially alloyed Cu and Ag phases were confirmedby operando X-ray diffraction. By means of combining operando X-ray measurements and density functional theory(DFT) calculations, the preferred carbonyl production is attributedto the reduced electron density and compressive strain of Cu due toAg incorporation, which leads to a deeper d-band center and thereforeweakened intermediate adsorption and oxophilicity. This work providesevidence of the intrinsic structural and electronic interaction betweenCu and Ag during eCO2RR. The obtained information will facilitatethe design of bi/multi-phase metallic or alloy electrocatalysts.

Automated summary

CO2 electrolysis converts CO2 into valuable fuels and chemicals, and adding Ag atoms to the Cu catalyst can modulate product preference. However, catalyst morphology, electrolyzer configuration, and reaction conditions strongly affect the synergistic effects and catalytic performance. This study prepared CuAg alloy catalysts and found that the interaction between Cu and Ag influenced the selectivity towards carbonyl production during CO2 reduction reaction.