Hydrogen‐Bonding‐Guided Interfacial Water Engineering for Selective CO2‐to‐C2+ Conversion at Industrial Current Densities

The electroreduction of CO2 to multi‐carbon (C2+) 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 C2+ 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 C2+ 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 CO2 availability and proton dynamic effectively decouples C─C coupling from HER, leading to selective C2+ formation. The resulting CoTAPc/Cu catalyst exhibits a C2+ Faraday efficiency (FE) of 90.7% with only 3.5% H2 FE at 1.1 A cm−2. Moreover, it maintains 81% C2+ selectivity at 30 A in a 100 cm2 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 CO2 conversion.