Promoting Electroreduction CO₂ to Multi-Carbon Products by Tailoring the ^*H Availability With Optimized Interfacial...

The electroreduction of CO₂ to multi-carbon products provides a promising path for approaching carbon neutrality. H₂O is generally considered a hydrogen source in CO₂RR, tailoring the interfacial H₂O configuration is critical yet often overlooked strategy for modulating CO₂RR performance. In this work, we demonstrated that regulating the interfacial water configuration through ionomer confinement is an effective strategy for enhancing multi-carbon (C₂₊) product selectivity in CO₂RR. The optimized catalyst 15.79% A5-Cu achieves 82% Faradaic efficiency (FE) for C₂₊ products at 200 mA cm^-2 in 0.1 M KHCO₃ and operates stably for over 100 h without salt precipitation in MEA system. In situ ATR-SEIRAS and Raman spectroscopy revealed that the confined environment tunes the proportion between K⁺-H₂O and 4-HB-H₂O configuration of interfacial H₂O. This enhanced *H generation and transfer ability can improve the *H utilization efficiency. Moreover, a moderate *H availability constructed by the balanced proportion of K⁺-H₂O and 4-HB-H₂O configurations lowers the energy barrier for *CO hydrogenation and subsequently C─C coupling step at a higher *CO coverage, which was confirmed by DFT calculations. This work highlights the critical role of interfacial H₂O configuration in steering C₂₊ product selectivity for that in addition to *H generation, the hydrogen bonding network can accurately guide *H toward *CO intermediate, thereby avoiding excessive accumulation of *H species.