Elucidating the Facet-Dependent Selectivity for CO2 Electroreduction to Ethanol of Cu-Ag Tandem Catalysts

Despite being desirable high-value products of the electro-chemical CO2 reduction reaction (CO2RR), alcohols are still obtained with lower selectivity compared to hydrocarbons and the reaction pathways leading to their formation are still under debate. In this joint experimental-computational work, we exploit structural sensitivity effects to elucidate the ethanol-producing active sites on Cu-Ag CO2RR tandem catalysts. Specifically, methane-selective Cu nano-octahedra (Cu-oh), enclosed by (111) facets, and ethylene-selective Cu nanocubes (Cu-cub), enclosed by (100) facets, are mixed with CO-selective Ag nanospheres (Ag-sph) to form Cu-oh-(A)g and Cu-cub-Ag bimetallic catalysts. Ethanol is selectively enhanced via the *CHx-*CO coupling pathway at the terraces of Cuoh-Ag in the CO-enriched environment generated by the Ag-sph. Conversely, on Cu-cub-Ag, ethanol is selectively produced via the same pathway at the edges and corners of Cu-cub, while ethylene continues to be produced at the terraces. The terraces being the predominant surfaces on the catalysts, such facet dependence explains the higher ethanol-to-ethylene ratio on the Cuoh-Ag. These findings illustrate how tandem catalysis and structure-sensitive effects can be combined to obtain notable changes in the selectivity of electrochemical reactions.

Automated summary

This study elucidates the active sites for ethanol production on Cu-Ag CO2RR tandem catalysts using structural sensitivity effects, showing how ethanol and ethylene formation pathways exhibit selectivity differences in a CO-enriched environment. The findings highlight the potential of tandem catalysis and structure-sensitive effects to significantly alter the selectivity of electrochemical reactions.