Cascade CO2 electroreduction enables efficient carbonate-free production of ethylene

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.