Constraining CO2 Coverage on Copper Promotes CO2 Electroreduction to Multi‐carbon Products in Strong Acid

Abstract

Electrocatalytic CO2 reduction (CO2R) to multi‐carbon (C2+) products in strong acid presents a promising approach to mitigate the CO2 loss commonly encountered in alkaline and neutral systems. However, this process often suffers from low selectivity for C2+ products due to the competing C1 (e.g., CO and HCOOH) formation and complex C‐C coupling kinetics. In this work, we report a CO2 coverage constraining strategy by diluting CO2 reactant feed to modulate the intermediate distribution and C‐C coupling pathways for an enhanced electrosynthesis of C2+ products in strong acid. Lowering the CO2 feed concentration reduces CO2 coverage on copper catalyst, enriching the surface coverage and optimizing the adsorption configuration of the key CO intermediate for C‐C coupling. This approach efficiently suppresses the formation of undesired C1 products. By employing a 20% CO2 feed, we achieved a significant improvement in C2+ Faradaic efficiency, reaching 68% at 100 mA cm‐2, approximately 1.7 times higher than the 41% obtained using pure CO2. We demonstrated the direct electroreduction of a 30% CO2 feed – representative CO2 concentration of typical industrial flue gases – in a full electrolyzer, achieving a C2+ selectivity of 78% and an energy efficiency of 23% at 200 mA cm‐2.