Multifunctional surface engineering of copper for enhanced C₂₊ production in CO₂ electroreduction

Electrocatalytic CO₂ reduction to high-value multi-carbon (C₂₊) products is pivotal for sustainable carbon utilization. Copper (Cu)-based catalysts are promising for promoting electrocatalytic CO₂ reduction to yield C₂₊ products. However, their performance is hindered by the competitive hydrogen evolution reaction (HER) and non-optimal *CO adsorption, which severely limit both selectivity and efficiency. Here, we report a surface modification strategy employing 3-aminopropyltriethoxysilane (APTES) to functionalize Cu nanosheets. The resulting APTES/Cu-5% catalyst achieves a superior faradaic efficiency of 79.4% and high partial current density of −714.6 mA cm⁻² toward C₂₊ products, significantly outperforming unmodified Cu and the majority of state-of-the-art Cu catalysts. Mechanistic studies reveal that this enhanced performance arises from the dual functinality of APTES. Its –NH₂ groups facilitate CO₂ activation, while its hydrophobic siloxane backbone suppresses HER by impeding H₂O transport. The synergistic effect enriches *CO intermediates on the Cu surface, facilitating C−C coupling and enabling high-rate C₂₊ production.