Weak CO binding sites induced by Cu-Ag interfaces promote CO electroreduction to multi-carbon liquid products.

Electrochemical reduction of carbon monoxide to high-value multi-carbon (C 2+ ) products offers an appealing route to store sustainable energy and make use of the chief greenhouse gas leading to climate change, i.e., CO 2 . Among potential products, C 2+ liquid products such as ethanol are of particular interest owing to their high energy density and industrial relevance. In this work, we demonstrate that Ag-modified oxide-derive Cu catalysts prepared via high-energy ball milling exhibit near 80% Faradaic efficiencies for C 2+ liquid products at commercially relevant current densities (>100 mA cm -2 ) in the CO electroreduction in a microfluidic flow cell. Such performance is retained in an over 100-hour electrolysis in a 100 cm 2 membrane electrode assembly (MEA) electrolyzer. A method based on surface-enhanced infrared absorption spectroscopy is developed to characterize the CO binding strength on the catalyst surface. The lower C and O affinities of the Cu-Ag interfacial sites in the prepared catalysts are proposed to be responsible for the enhanced selectivity for C 2+ oxygenates, which is the experimental verification of recent computational predictions.