Hydrogen‐Bonding‐Guided Interfacial Water Engineering for Selective CO ₂ ‐to‐C ₂₊ Conversion at Industrial Current Densities

Abstract The electroreduction of CO 2 to multi‐carbon (C 2+ ) products offers a sustainable route for chemicals production. However, the competing hydrogen evolution reaction (HER), especially at high current densities where proton transport dominates, remains a major challenge to achieving high C 2+ selectivity. In this study, an interfacial water engineering strategy guided by hydrogen bonding is reported to construct a dual‐functional Cu‐based catalyst that simultaneously enhances C 2+ selectivity and suppresses HER. By co‐assembling cobalt tetraaminated phthalocyanine (CoTAPc) and perfluorosulfonic acid (PFSA) onto Cu surface, a hydrophobic, hydrogen‐bond‐rich microenvironment is formed. This interfacial network reorganizes water molecules into spatially confined clusters, enabling directional proton transport and accelerating water dissociation. Such dual modulation of CO 2 availability and proton dynamic effectively decouples C─C coupling from HER, leading to selective C 2+ formation. The resulting CoTAPc/Cu catalyst exhibits a C 2+ Faraday efficiency (FE) of 90.7% with only 3.5% H 2 FE at 1.1 A cm −2 . Moreover, it maintains 81% C 2+ selectivity at 30 A in a 100 cm 2 membrane electrode assembly (MEA) electrolyzer. Operando spectroscopic analyses and density functional theory (DFT) calculations reveal that CoTAPc‐PFSA interface lowers the *CO dimerization barrier while facilitating water dissociation and increasing *H adsorption energy, thus suppressing HER and enabling efficient CO 2 conversion.