Electrosynthesis of Ethylene from Syngas via Functionalized Carbon

Electrochemical CO reduction (COR) to ethylene (C₂H₄) offers a carbon- and energy-efficient route to chemical production. However, the use of pure CO as feedstock limits scalability, whereas syngas—produced at ~250 times the volume of pure CO globally—is the more practical industrial feedstock. Achieving high single-pass carbon efficiency (SPCE) in syngas-fed COR systems is essential, as high inlet flow rates E introduce H₂ dilution, increasing downstream separation costs. However, under SPCE-optimized conditions, we observed a decline in C₂H₄ Faradaic efficiency (FE) as CO is mass transport-limited on Cu due to a combination H₂ dilution and insufficient CO supply to the cathode. Here, we address this challenge by introducing a COOH-functionalized active carbon layer that selectively captures and enriches CO near Cu catalyst sites. Guided by operando Raman spectroscopy and DFT analysis, this functional interface enhances CO adsorption and enables sustained C₂H₄ selectivity under CO-diluted conditions. We demonstrate a C₂H₄ FE of 72% and SPCE of 73% in syngas (H₂/CO = 2:1), achieving an energy cost of 203 GJ/ton—comparable to leading systems operating with pure CO.