Molecularly Engineered N-Heterocyclic Carbene–Copper Interfaces for Selective Ampere-Level CO2 Electroreduction to Ethanol

Abstract Electrocatalytic CO2 conversion to high-energy-density ethanol is vital for the sustainable development of society and economy, yet challenges remain in achieving high selectivity at ampere-level current densities. Herein, we rationally engineer a 1,3-dimesitylimidazol-2-ylidene (IMes)-functionalized copper hollow fiber penetration electrode (IMes-Cu HPE) for ampere-level CO2 electroreduction to ethanol. The strong electron-donating properties of N-heterocyclic carbenes (NHCs) modulate the electronic structure of the Cu active sites, effectively steering the evolution of the *CH2CHO intermediate toward the ethanol pathway to enhance selectivity. Concurrently, the unique “gas-penetration effect” inherent to the hollow fiber electrodes reinforces mass transfer and triple-phase boundary reactions, facilitating efficient ethanol synthesis. By systematically optimizing the IMes coverage and the specific adsorption of electrolyte Cl– anions, a remarkable ethanol Faradaic efficiency (FE) of 55.5% and a peak C2+ FE of 80.5% are achieved at a current density of 2.5 A cm–2. This study provides fundamental insights into the synergistic design of electrode configurations and molecular interfacial functionalization for highly efficient CO2-to-ethanol conversion.