Selective CO 2 Reduction to Ethylene Mediated by Adaptive Small‐molecule Engineering of Copper‐based Electrocatalysts

Electrochemical CO 2 reduction reaction (CO 2 RR) over Cu catalysts exhibits enormous potential for efficiently converting CO 2 to ethylene (C 2 H 4 ). However, achieving high C 2 H 4 selectivity remains a considerable challenge due to the propensity of Cu catalysts to undergo structural reconstruction during CO 2 RR. Herein, we report an in situ molecule modification strategy that involves tannic acid (TA) molecules adaptive regulating the reconstruction of a Cu‐based material to a pathway that facilitates CO 2 reduction to C 2 H 4 products. An excellent Faraday efficiency (FE) of 63.6 % on C 2 H 4 with a current density of 497.2 mA cm −2 in flow cell was achieved, about 6.5 times higher than the pristine Cu catalyst which mainly produce CH 4 . The in situ X‐ray absorption spectroscopy and Raman studies reveal that the hydroxyl group in TA stabilizes Cu δ+ during the CO 2 RR. Furthermore, theoretical calculations demonstrate that the Cu δ+ /Cu 0 interfaces lower the activation energy barrier for *CO dimerization, and hydroxyl species stabilize the *COH intermediate via hydrogen bonding, thereby promoting C 2 H 4 production. Such molecule engineering modulated electronic structure provides a promising strategy to achieve highly selective CO 2 reduction to value‐added chemicals.