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

Abstract

Despite being desirable high-value products of the electrochemical 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 (Cuoh), enclosed by (111) facets, and ethylene-selective Cu nano-cubes (Cucub), enclosed by (100) facets, are mixed with CO-selective Ag nanospheres (Agsph) to form Cuoh-Ag and Cucub-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 Agsph . Conversely, on Cucub-Ag ethanol is selectively produced via the same pathway at the edges and corners of Cucub while ethylene continues to be produced at the terraces. 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.