Cascade CO 2 electroreduction enables efficient carbonate-free production of ethylene
CO 2 electroreduction provides a route to convert waste emissions into chemicals such as ethylene (C 2 H 4 ). However, the direct transformation of CO 2 -to-C 2 H 4 suffers from CO 2 loss to carbonate, consuming up to 72% of energy input. A cascade approach—coupling a solid-oxide CO 2 -to-CO electrochemical cell (SOEC) with a CO-to-C 2 H 4 membrane electrode assembly (MEA)—would eliminate CO 2 loss to carbonate. However, this approach requires a CO-to-C 2 H 4 MEA with energy efficiency well beyond demonstrations to date. Focusing on the MEA, in this study 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 C 2 H 4 faradaic efficiency of 65% at 150 mA cm –2 for 110 h. Demonstrating a cascade SOEC-MEA approach, we achieve CO 2 -to-C 2 H 4 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.