Interfacial Diffusion‐Reaction Coupling Strategy for CO ₂ Reduction on Copper Surface in Acidic Medium

Abstract

Abstract CO 2 electroreduction reaction in acid medium to produce multicarbon (C 2+ ) products has gained attention as an alternative to the traditional processes in neutral or alkaline solutions which often suffer from low single‐pass conversion efficiency due to (bi)carbonate accumulation at the cathode. However, the CO 2 conversion efficiency in acid remains unsatisfactory. Herein, a strong‐polarized layer‐covered Cu catalyst is developed as electrode for CO 2 reduction reaction (CO 2 RR) in acid. Such a strong dipole moment layer is a sp 3 ‐hybridized nitrogen ( sp 3 ‐N)‐enriched azulene‐based polymer, which acts as Lewis base to boost the CO 2 ‐diffusion kinetics in inner Helmholtz plane. Such unique electrode delivers nearly 84% C 2 Faradaic efficiency at 200 mA cm −2 , and demonstrates long‐term stability over 40 h, which is the record for CO 2 RR in acidic media. In situ experiments manifest the moderate azulene‐polarized sp 3 ‐N‐enriched micro‐environment can increase the local CO 2 /H 2 O ratio at electric double‐layer to further stabilize the key intermediate atop‐bound *CO. Theoretical calculations reveal that the strong‐polarized layer decreases the reaction energy barrier for C–C coupling. This study not only uncovers the units with strong dipole moment on tuning sp 3 ‐N‐enriched micro‐environment, but also provides an interfacial diffusion‐reaction coupling strategy to enhance the selectivity of CO 2 RR by decorating polycrystalline Cu with strong‐polarized polymers.