Confinement-enhanced CO₂ electroreduction: Yolk-shell Cu@HCS catalyst for high-selectivity synthesis of C₂ products

The electrochemical reduction of CO₂ to multi-carbon (C₂₊) products is a promising strategy for sustainable fuel and chemical production and CO₂ emission mitigation. However, optimizing *CO intermediate generation and utilization in complex multi-electron systems is crucial for the C₂ products, but it remains challenging. Herein, we synthesize a yolk-shell structured Cu@HCS catalyst via hydrothermal synthesis coupled with high-temperature calcination, featuring a unique copper core and hollow carbon shell nanostructure. This architecture significantly enhances the selectivity toward C₂ products during electrocatalytic CO₂ reduction. The optimized Cu@HCS-2-800 catalyst achieves a Faradaic efficiency (FE) of 69.7% for C₂ products at –1.4 V vs. reversible hydrogen electrode (RHE), markedly surpassing the 30.1% FE of conventional Cu/xc-72 catalyst. Furthermore, the yolk-shell configuration suppresses hydrogen evolution, ensuring superior stability during prolonged operation. In situ attenuated total reflectance-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory (DFT) analysis reveal that the Cu@HCS-2-800 catalyst leverages spatial confinement effects to retard CO diffusion and promote CO re-adsorption, thereby elevating *CO intermediate coverage to enhance C–C coupling. This work underscores the pivotal role of nanoscale spatial confinement in advancing CO₂ electroreduction performance and provides a guidance for designing advanced catalysts with tailored microenvironment.