Molecule–Copper Interface for Efficient Electrochemical CO ₂ -to-Ethylene in Acidic Media

Acidic electrochemical CO₂ reduction reaction (CO₂RR) offers an attractive route to store intermittent renewables as valuable chemicals with high carbon efficiency but suffers from low selectivity due to predominant hydrogen evolution reaction. Utilizing concentrated alkali cations steers the acidic CO₂RR to multicarbon (C₂₊) products but leads to salt precipitation. Here we report a molecular tuning strategy to facilitate acidic CO₂RR to ethylene under a low K⁺ concentration by modifying tetraphenylporphyrin-based molecules onto a Cu surface. At 200 mA cm⁻², we achieve a record ethylene Faradaic efficiency (FE) of 53% on 5,10,15,20-tetraphenyl-21H,23H-porphine zinc functionalized Cu catalysts (a 1.2× improvement compared to the best reports at above 100 mA cm⁻² under an acidic electrolyte having a low alkali cation concentration) and a high C₂₊ FE of 85%, as well as a high CO₂ single-pass utilization of 72%. This work presents a catalyst design strategy for efficient acidic CO₂-to-ethylene electrolysis under low alkali-cation availability.