Built‐In Electric Field Triggered Interfacial Water Activation for Industrial‐Level Electrosynthesis of Ethylene from CO ₂

Abstract The electrochemical reduction of CO 2 to ethylene (C 2 H 4 ), as opposed to traditional industrial methods, stands out as an environmentally friendly benign and promising technical solution for producing value‐added chemicals using renewable electricity. Here, we introduce a built‐in electric field in La(OH) 3 ‐Cu (BEF@La(OH) 3 ‐Cu) electrocatalyst that can exclusively convert from CO 2 to C 2 H 4 with a maximum Faradaic efficiency of 84.2% and high intrinsic activity exceeding 842.0 mA cm −2 , while maintaining robust stability of 110 h. Furthermore, the corresponding C 2 H 4 formation rate and energy efficiency can reach 2618.0 µmol cm −2 h −1 and 31.2%, respectively. The BEF@La(OH) 3 ‐Cu electrocatalyst was constructed by stacking La(OH) 3 and Cu layers, forming a built‐in electric field induced by electron transfer between La→O←Cu. The electric field effectively triggered H 2 O dissociation on La(OH) 3 ‐Cu interface for supplying active hydrogen (*H) species, which promoted multiple protonation steps in the process of CO 2 ‐to‐C 2 H 4 conversion. The *H species then easily migrate to Cu sites, reducing the energy barrier for the conversion from *CO to *COH, thus enhancing the efficient asymmetric *CO−*COH coupling and ultimately boosting the C 2 H 4 production under ampere‐level operation.