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.