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 a high current density of 320 mA cm⁻², corresponding to 60 mol% of the liquid products. Mechanistic investigations combining CO₂RR and CO reduction (CORR) measurements suggest that Ag sites act as local CO generators, creating high *CO coverage that spills over to adjacent Cu domains. This interfacial synergy establishes a unique CO-rich microenvironment that, together with high local alkalinity, promotes acetate-selective pathways resembling those typically observed during the CORR. These results highlight how nanoscale alloy engineering can tailor catalytic microenvironments and redirect CO₂RR pathways toward oxygenated C₂ products, providing new insights for selective CO₂-to-chemical conversion at high current densities.