Mechanistic Insights into the Selective Electroreduction of Carbon Dioxide to Ethylene on Cu2O-Derived Copper Catalysts

In this work, we made a comprehensive investigation to unravel the underlying causes for the selectivity of CO2 electroreduction toward ethylene on Cu2O-derived Cu catalysts. Scanning electron microscopy, X-ray diffraction, cyclic voltammetry, chronoamperometry, chronopotentiometry, online gas chromatography, nuclear magnetic resonance spectroscopy, and numerical simulations of local pH were used toward this end. Ten Cu2O-derived Cu films of different thicknesses and morphologies were prepared and extensively characterized. Aqueous 0.1 M KHCO3 was used as the electrolyte. We report here, for the first time, a remarkably strong correlation between the statistically relevant crystallite sizes of the Cu2O-derived Cu particles and selective CO2 electroreduction to C2H4. Specifically, as the crystallite size of the particles decreased from 41 to 18 nm, the Faradaic efficiency (FE) of C2H4 formation increased from 10 to 43%. Using cyclic voltammetry, samples with smaller particle crystallite sizes were found to...