N-Heterocyclic Carbene-Modified Copper Hollow Fiber Electrodes for Ampere-Level CO₂ Electroreduction to Ethanol

Electrocatalytic CO₂ reduction offers a sustainable pathway to produce high-energy-density ethanol fuel. However, achieving highly selective ethanol production at ampere-level current densities remains a significant challenge. Herein, we report the development of a novel 1,3-dimesitylimidazol-2-ylidene (IMes)-modified Cu hollow fiber penetration electrode (IMes-Cu HPE) leveraging the strong σ-donating property of N-heterocyclic carbenes (NHCs) to enhance both selectivity and efficiency toward ethanol. At a current density of 2.5 A cm^-2, the IMes-Cu HPE achieves a remarkably high faradaic efficiency (FE) of 57% for ethanol and over 81% for C₂₊ products. In situ spectroscopic analysis and density functional theory (DFT) calculations reveal that IMes modification alters the microenvironment on the Cu HPE surface and enhances the electron density of Cu active sites. This regulation facilitates the lowering of energy barriers for key intermediate formation and asymmetric C─C coupling, promoting ethanol generation. This work presents a promising strategy of molecular interface engineering for efficient CO₂-to-ethanol conversion at industrially relevant current densities.