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 C-2 and C-3 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 (CO)-C-13 and (CO2)-C-12, 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.