F-modified Cu/electrolyte interface boosts CO2 electroreduction into C2H4 and C2H5OH products via an alternative CC coupling mechanism

A F⁻-modified Cu(111) electrocatalysts exhibited an ultrahigh Faradaic efficiency and product selectivity towards CO₂ electroreduction into C₂ products. Thus, CO₂ electroreduction mechanisms towards C₂H₄ and C₂H₅OH products at F⁻-modified Cu(111)/H₂O interface based on DFT calculations are studied in this work, by which the influencing mechanism of specifically adsorbed F⁻ on electroreduction activity, product selectivity and a alternative CC coupling mechanism can be revealed. Our present studies indicate that the presence of F⁻ can notably enhance CO₂ electroreduction activity towards key intermediate CO because of significantly changed CO₂ adsorption configuration and weakening effect of F⁻ on COOH adsorption strength. CO dimerization into dimer OCCO through Langmuir-Hinshelwood mechanism is more favorable than CHO formation in the presence of the F⁻. Thus, it can be concluded that CC coupling reaction occurs via CO dimerization. More CO adsorption strength because of modification of F⁻ can explain easier occurrence of CC coupling reaction, thus leading to change of product selectivity. The parallel OCCOH and OCCHO pathways are proposed for CO₂ electroreduction into C₂H₄ and C₂H₅OH products at F⁻-modified Cu(111)/H₂O interface, in which CO dimerization is regarded as the rate-determining step. Ou present studies can unveil CO₂ electroreduction mechanisms and significant role of the specifically adsorbed F⁻ at Cu/electrolyte interface for promoting CO₂ electroreduction activity and improving product selectivity towards C₂ products.