Tailoring Dual-Functional Ionomers for Efficient CO 2 Electroreduction to Ethanol

Alcohols production through the electrochemical CO 2 reduction reaction (CO 2 RR) provides a sustainable route for resource utilization and energy storage. However, achieving sustained and efficient CO 2 -to-ethanol conversion with long-term performance remains a challenge. Here, we propose an ionomer microenvironment engineering strategy that demonstrates that the functionalized ionomer effectively boosts the performance toward ethanol conversion in the CO 2 RR for the first time. The poly[2-acrylamido-2-methylpropanesulfonic acid- co -(2-methyl-2-(trifluoromethylsulfonamido)propyl methacrylate)- co -(1-vinyl-3-butylimidazolium hexafluorophosphate)] ionomer (PAMV) is designed and synthesized, which contains both hydrophilic and CO 2 -philic structural units, thus creating a microenvironment to enhance the adsorption of both water and CO 2 . Using commercial copper nanoparticles as the catalyst, 57.3% ethanol faradaic efficiency (FE) and 29.3% cathodic energy efficiency (CEE) are achieved over PAMV-Cu based gas diffusion electrodes in bicarbonate electrolyte. This performance is approximately 4 times that of the commonly used commercial Nafion ionomer under the same conditions. Long-term electrolysis demonstrates its prominent ability to inhibit salt precipitation and H 2 evolution. Experimental and theoretical studies reveal that the functionalized structural units in PAMV modulate the mass transfer of CO 2 and H 2 O on the interface of the Cu catalyst, promoting the formation of *CO intermediate and enhancing the thermodynamic competitiveness of the ethanol production pathway. This work provides a novel ionomer-engineered approach for modulating electrocatalytic reactions, which offers a robust and convenient solution for the efficient conversion of CO 2 to value-added products.