Evidence for product-specific active sites on oxide-derived Cu catalysts for electrochemical CO2 reduction

Carbon dioxide electroreduction in aqueous media using Cu catalysts can generate many different C2 and C3 products, which leads to the question whether all products are generated from the same types of active sites or if product-specific active sites are responsible for certain products. Here, by reducing mixtures of 13CO and 12CO2, we show that oxide-derived Cu catalysts have three different types of active sites for C–C coupled products, one that produces ethanol and acetate, another that produces ethylene and yet another that produces 1-propanol. In contrast, we do not find evidence of product-specific sites on polycrystalline Cu and oriented (100) and (111) Cu surfaces. Analysis of the isotopic composition of the products leads to the prediction that the adsorption energy of *COOH (the product of the first step of CO2 reduction) may be a descriptor for the product selectivity of a given active site. These new insights should enable highly selective catalysts to be developed. Copper-based catalysts, especially the so-called oxide-derived copper, are capable of producing multicarbon species from electrochemical CO2 reduction. However, little is known about their active sites despite intensive research efforts. Now, Lum and Ager show that oxide-derived copper catalysts have three distinct product-specific sites for the formation of C2+ chemicals, unlike polycrystalline copper or (111)- and (100)-oriented copper films which show no evidence of product specific sites.