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Abstract

The production of multicarbon products (C₂₊) from CO₂ electroreduction reaction (CO₂RR) is highly desirable for storing renewable energy and reducing carbon emission. Here we report the electrochemical synthesis of CO₂RR catalysts that are highly selective for C₂₊ products via electrolyte‐driven nanostructuring. Nanostructured Cu catalysts synthesized in the presence of specific anions can selectively convert CO₂ to ethylene and multicarbon alcohols in aqueous 0.1 M KHCO₃ solution, with the iodine‐modified catalyst displaying the highest Faradaic efficiency of ~80% and partial current density of ~31.2 mA cm^-2 for C₂₊ products at −0.9 V vs RHE. Operando X‐ray absorption spectroscopy and quasi in situ X‐ray photoelectron spectroscopy measurements revealed that the high C₂₊ selectivity of these nanostructured Cu catalysts can be attributed to the highly roughened surface morphology induced by our synthesis, the presence of subsurface oxygen and Cu⁺ species, and the adsorbed halides. This work provides new insight into the parameters that should be tuned in order to rationally design C₂₊‐selective CO₂RR catalysts.