Silica-copper catalyst interfaces enable carbon-carbon coupling towards ethylene electrosynthesis

Membrane electrode assembly (MEA) electrolyzers offer a means to scale up CO₂-to-ethylene electroconversion using renewable electricity and close the anthropogenic carbon cycle. To date, excessive CO₂ coverage at the catalyst surface with limited active sites in MEA systems interferes with the carbon-carbon coupling reaction, diminishing ethylene production. With the aid of density functional theory calculations and spectroscopic analysis, here we report an oxide modulation strategy in which we introduce silica on Cu to create active Cu-SiO_x interface sites, decreasing the formation energies of OCOH* and OCCOH*-key intermediates along the pathway to ethylene formation. We then synthesize the Cu-SiO_x catalysts using one-pot coprecipitation and integrate the catalyst in a MEA electrolyzer. By tuning the CO₂ concentration, the Cu-SiO_x catalyst based MEA electrolyzer shows high ethylene Faradaic efficiencies of up to 65% at high ethylene current densities of up to 215 mA cm^-2; and features sustained operation over 50 h.