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

Abstract

CO2 electrolysis converts the greenhouse gas CO2 into valuable fuels and chemicals, such as carbon monoxide, ethylene, ethanol, etc. Currently, Cu is the only known monometallic catalyst capable of producing multicarbon products from electrochemical CO2 reduction reaction (eCO2RR), while the poor selectivity limits its further use. It has been found that introducing Ag atoms into the Cu lattice can modulate product preference. However, the synergistic effects between Cu and Ag, and thus, the catalytic performance, are strongly influenced by catalyst morphology, electrolyzer configuration, reaction conditions, etc. Operando measurements can provide explicit information on the catalyst dynamic variation during the reaction, but their operation and analysis are challenging. Herein, we prepared CuAg multiphase alloy catalysts by magnetron sputtering, which allowed for investigating the intrinsic interaction between Cu and Ag. eCO2RR performance exhibited an improved selectivity toward carbonyls at the expense of hydrogen and hydrocarbons. The partially alloyed Cu and Ag phases were confirmed by operando X-ray diffraction. By means of combining operando X-ray measurements and density functional theory (DFT) calculations, the preferred carbonyl production is attributed to the reduced electron density and compressive strain of Cu due to Ag incorporation, which leads to a deeper d-band center and therefore weakened intermediate adsorption and oxophilicity. This work provides evidence of the intrinsic structural and electronic interaction between Cu and Ag during eCO2RR. The obtained information will facilitate the design of bi/multi-phase metallic or alloy electrocatalysts.

Facet Engineering of Copper for Product Specific CO2 Electroreduction

“…The catalytic performance is significantly impacted by the morphology of the catalyst, the configuration of the electrolyzer, reaction conditions, specific active sites, reaction intermediates, and the effect of surface restructuring. Hence, operando measurements are essential for providing explicit information and supporting fundamental research …”

Preparation of Tunable Cu−Ag Nanostructures by Electrodeposition in a Deep Eutectic Solvent

“…[10][11][12][13] Among bimetallic catalysts, CuÀ Ag nanocatalysts have shown promising properties towards the oxygen reduction reaction (ORR) in alkaline media and, most commonly, the electrochemical reduction of carbon monoxide and carbon dioxide (CORR and CO 2 RR). [14][15][16][17][18][19] Controlling the size, shape, and composition of the nanoparticle (NPs) is crucial to enhance the activity and tune the selectivity towards the desired product. Multiple physical and chemical synthesis methods have been studied to prepare CuÀ Ag catalysts with controlled size, shape, and composition.…”

Composition effects of electrodeposited Cu-Ag nanostructured electrocatalysts for CO2 reduction

“… 31 , 32 , 33 , 34 In particular, Cu-Ag are promising bimetallic catalysts to reduce CO 2 to liquid and oxygenated products such as ethanol, propanol, acetaldehyde, and ethylene glycol as both tandem catalysts and alloys. 30 , 35 , 36 , 37 …”

“… 30 On the other hand, a study on Cu-Ag surface alloys presented the formation of multi-carbon oxygenates due to compressive surface strain of the Cu atoms which selectively suppresses the HER by weakening the adsorption energy of ∗ H. 39 On a similar basis, through a compressive strain and reduced electron density, Cu-Ag multi-phase alloys were also proved to be promising catalysts for the production of acetaldehyde. 36 …”