Stable and selective electrochemical reduction of carbon dioxide to ethylene on copper mesocrystals

Abstract

Stable and selective electrochemical reduction of carbon dioxide to ethylene was achieved using copper mesocrystal catalysts in 0.1 M KHCO₃. The Cu mesocrystal catalysts were facilely derived by the in situ reduction of a thin CuCl film during the first 200 seconds of the CO₂ electroreduction process. At −0.99 V vs. RHE, the Faradaic efficiency of ethylene formation using these Cu mesocrystals was ~18× larger than that of methane and forms up to 81% of the total carbonaceous products. Control CO₂ reduction experiments show that this selectivity towards C₂H₄ formation could not be replicated by using regular copper nanoparticles formed by pulse electrodeposition. High resolution transmission electron microscopy reveals the presence of both (100)_Cu facets and atomic steps in the Cu mesocrystals which we assign as active sites in catalyzing the reduction of CO₂ to C₂H₄. CO adsorption measurements suggest that the remarkable C₂H₄ selectivity could be attributed to the greater propensity of CO adsorption on Cu mesocrystals than on other types of Cu surfaces. The Cu mesocrystals remained active and selective towards C₂H₄ formation for longer than six hours. This is an important and industrially relevant feature missing from many reported Cu-based CO₂ reduction catalysts.