Item

Abstract

Although progress has been made in producing multi-carbon products from the electrochemical reduction of CO₂ the modest selectivity for ethylene (C₂H₄) leads to low energy efficiency and high downstream separation costs. Here we functionalize Cu catalysts with a variety of substituted aryl diazonium salts to improve selectivity towards multi-carbon products. Using computation and operando spectroscopy, we find that Cu surface oxidation state (δ⁺ where 0 < δ < 1) can be tuned by functionalization and that it influences the selectivity to C₂H₄. We report a Faradaic efficiency and a specific current density for C₂H₄ as large as 83 ± 2% and 212 mA cm⁻², respectively, on partially oxidized Cu^0.26+. Using a CO gas feed, we demonstrate an energy efficiency of ~40% with a C₂H₄ Faradaic efficiency of 86 ± 2%, corresponding to a low electrical power consumption of 25.6 kWh Nm⁻³ for the CO to C₂H₄ conversion reaction. Our findings provide a route towards practical electrosynthesis of C₂H₄ using valence engineering of copper.