Cascade CO₂ electroreduction enables efficient carbonate-free production of ethylene

Abstract

CO₂ electroreduction provides a route to convert waste emissions into chemicals such as ethylene (C₂H₄). However, the direct transformation of CO₂-to-C₂H₄ suffers from CO₂ loss to carbonate, consuming up to 72% of energy input. A cascade approach—coupling a solid-oxide CO₂-to-CO electrochemical cell (SOEC) with a CO-to-C₂H₄ membrane electrode assembly (MEA)—would eliminate CO₂ loss to carbonate. However, this approach requires a CO-to-C₂H₄ MEA with energy efficiency well beyond demonstrations to date. Focusing on the MEA, we find that an N-tolyl substituted tetrahydro-bipyridine film improves the stabilization of key reaction intermediates, while an SSC ionomer enhances CO transport to the Cu surface, enabling a C₂H₄ faradaic efficiency of 65% at 150 mA cm⁻² for 110 h. Demonstrating a cascade SOEC-MEA approach, we achieve CO₂-to-C₂H₄ with a ~48% reduction in energy intensity compared with the direct route. We further reduce the energy intensity by coupling CO electroreduction (CORR) with glucose electrooxidation.