Steering CO₂ Electroreduction Selectivity U-Turn to Ethylene by Cu-Si Bonded Interface

Copper (Cu), with the advantage of producing a deep reduction product, is a unique catalyst for the electrochemical reduction of CO₂ (CO₂RR). Designing a Cu-based catalyst to trigger CO₂RR to a multicarbon product and understanding the accurate structure-activity relationship for elucidating reaction mechanisms still remain a challenge. Herein, we demonstrate a rational design of a core-shell structured silica-copper catalyst (p-Cu@m-SiO₂) through Cu-Si direct bonding for efficient and selective CO₂RR. The Cu-Si interface fulfills the inversion in CO₂RR product selectivity. The product ratio of C₂H₄/CH₄ changes from 0.6 to 14.4 after silica modification, and the current density reaches a high of up to 450 mA cm^-2. The kinetic isotopic effect, in situ attenuated total reflection Fourier-transform infrared spectra, and density functional theory were applied to elucidate the reaction mechanism. The SiO₂ shell stabilizes the *H intermediate by forming Si-O-H and inhibits the hydrogen evolution reaction effectively. Moreover, the direct-bonded Cu-Si interface makes bare Cu sites with larger charge density. Such bare Cu sites and Si-O-H sites stabilized the *CHO and activated the *CO, promoting the coupling of *CHO and *CO intermediates to form C₂H₄. This work provides a promising strategy for designing Cu-based catalysts with high C₂H₄ catalytic activity.