Unlocking n ‐Propanol Electrosynthesis From CO 2 via Constructing *CO─H 2 O Reaction Microregion

ABSTRACT Selective electroreduction of CO 2 (CO 2 RR) to n ‐propanol represents a promising route for low‐carbon chemical synthesis. However, achieving high selectivity at industrially relevant current densities remains challenging due to inefficient *CO utilization and strong competition from C 2 products. Herein, we demonstrate that a Cu 2 O/CeO 2 interfacial catalyst overcomes these limitations by constructing a *CO─H 2 O reaction microregion that facilitates selective C 1 ─C 2 coupling. Isotope‐competitive in situ differential electrochemical mass spectrometry (DEMS) reveals that the CeO 2 ‐induced interfacial structure shifts protonation pathway of activated CO 2 from adsorbed hydrogen to solvent hydrogen, thereby generating high local *CO flux. Under CO 2 RR conditions, the *CO─H 2 O reaction microregion arises from non−covalent interaction between high‐density *CO and loosely H‐bonded water molecules. Time‐resolved pulsed spectroscopy and theoretical calculations confirmed that this microregion dynamically confines *CO and reduces their molecular orbital degeneracy, enhancing *CO availability for C─C coupling reaction. Site‐specific kinetics isotope effect experiments further indicate the reaction microenvironment promotes *CO attack on the α carbon of *C 2 intermediates, effectively steering reaction pathway toward n ‐propanol. As a result, the catalyst achieves n ‐propanol Faradaic efficiency (FE) of 26.1%. These findings underscore the significance of non‐covalent interactions between intermediates and electrolyte in controlling proton‐related surface reaction, offering opportunities for steering electrocatalytic pathways toward valuable products.