Constraining CO Coverage on Copper Promotes CO Electroreduction to Multi-carbon Products in Strong Acid.

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