Switching the Formation of Intermediates through Inherent Cu+-OH Structures over Cu-Based Catalysts for Enhanced Electrochemical CO2 Reduction to Ethylene

Due to the high energy barrier of C-C coupling and the intense competition from by-products, achieving superior ethylene selectivity in electrochemical CO2 reduction reaction (eCO2RR) remains challenging. Herein, we reported a distinctive Cu-based electrocatalyst fabricated from a three-dimensional (3D) tentacle-like Cu2(OH)2CO3 precursor. After electrochemical activation, abundant surface structural hydroxyls chemically bonded to Cu+ species (Cu+-OH structures) formed on the resulting Cu-based electrocatalyst. Such structural hydroxyl-rich Cu-based catalyst exhibited excellent eCO2RR performance, with a Faradaic efficiency (FE) of 43.7% for ethylene (partial current density up to 130.6 mA·cm-2) and a FE of ~70% for C2+ products at -1.5 V vs RHE in a flow cell, far exceeding those over the hydroxyl-deficient Cu-based one. By combining operando spectroscopic analysis with density functional theory calculations, it was unveiled that inherent surface Cu+-OH structures over Cu-based electrocatalysts could result in the electron loss of neighboring active Cu0 sites, which was favorable for the creation of crucial *COH and *OCCOH intermediates and thus the formation of ethylene product. Consequently, dual reaction pathways for the eCO2RR based on both key *COH and *CHO intermediates coexisting on the Cu-based electrocatalyst with abundant Cu+-OH structures powerfully boosted electrochemical CO2 reduction to produce ethylene. This work presents an innovative strategy for the construction of Cu-based electrocatalyst rich in structural hydroxyls and highlights the crucial role of inherent Cu+-OH structures in switching the formation of intermediates to boost ethylene production in the eCO2RR.