Switching the formation of intermediates through inherent Cu+–OH structures over Cu-based catalysts for enhanced electrochemical CO2 reduction to ethylene

Abstract

Due to the high energy barrier of C–C coupling and the intense competition from by-products, achieving superior ethylene selectivity in the electrochemical CO₂ reduction reaction (eCO₂RR) remains challenging. Herein, we have 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 a 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 the 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 a 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.