Covalent Elaboration of Confined Surfaces Steers C─C Coupling Pathway for Selective Electrochemical CO ₂ Reduction at Ampere‐Level

Abstract Microenvironmental engineering of electrocatalysts is pivotal for directing reaction pathways and stabilizing key intermediates in CO 2 reduction reaction (CO 2 RR) to multicarbon products, but it has yet to meet the industrial requirement for selectively producing a most desired product, such as ethylene or ethanol, at a steady above‐ampere current level. Herein, a topotactic conversion cum covalent functionalization strategy is invoked to craft a catalyst with confined and modulated surfaces that can bias the reaction heavily for ethylene production with a 22‐fold boost in the ethylene/ethanol ratio. The well‐tuned covalent structural motif of ─Si─O─Cu─ on PDMS‐Cu 2 O/C dramatically elevates the C 2 H 4 ‐forming activity with a faradaic efficiency reaching up to 71% and a high partial current density of 513.6 mA cm −2 . Operando infrared spectroscopy and density functional theory calculations unveil the ultralow coordination number and the upshifted d‐band center. Notably, modulating the d‐band center with the covalently elaborated surfaces allows control of the adsorption energies of CHO* and other intermediates along the ethylene path, largely lowering energy barriers for the key steps, particularly the formation of CH 2 CHO*. This work sheds light on the microenvironment modulation at the surface bonding to mesoscopic scales to precisely control catalytic processes and steer reaction pathways toward the target product.