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

The electrochemical reduction of CO₂ to ethylene (C₂H₄), 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 CO₂ to C₂H₄ 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 C₂H₄ 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 H₂O dissociation on La(OH)₃-Cu interface for supplying active hydrogen (*H) species, which promoted multiple protonation steps in the process of CO₂-to-C₂H₄ 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 C₂H₄ production under ampere-level operation.