Engineering Cu-Ag Interfaces for Selective Acetate Production in CO2 Electroreduction

Abstract

Controlling product selectivity in electrochemical CO2 reduction (CO2RR) remains a major challenge, particularly in steering C-C coupling toward specific high-value liquid products. Here, we demonstrate that nanoscale Cu-Ag alloying, synthesized by magnetron co-sputtering, can fundamentally reshape the reaction pathway, redirecting the intrinsic C2+ selectivity of Cu toward acetate formation. In a gas diffusion electrode (GDE) flow cell reactor, the optimized Cu40Ag60 catalyst achieves an acetate Faradaic efficiency of 31.1% at an industrially relevant current density of -320 mA cm-2, corresponding to 60 mol% in liquid products. Mechanistic investigations combining CO2RR and CO reduction (CORR) reveal that Ag sites act as local CO generators, creating a high *CO coverage that spills over to adjacent Cu domains. This interfacial synergy establishes a unique reaction microenvironment that, together with high local alkalinity, promotes acetate formation via an asymmetric *CO-*CHO coupling pathway. These results highlight how atomic-scale alloy design can be used to engineer catalytic microenvironments and unlock selective pathways toward otherwise minor products, offering a powerful strategy for advancing CO2-to-chemicals conversion at industrially relevant rates.