Nanoconfinement and tandem catalysis over yolk-shell catalysts towards electrochemical reduction of CO2 to multi-carbon products.

Electrocatalytic materials in the electrochemical reduction of carbon dioxide (CO2ER) provide an effective strategy to mitigate CO2 emissions, enable carbon recycling, and synthesize high-value multi-carbon (C2+) chemicals, thereby supporting long-term renewable energy storage. Recent advances highlight that yolk-shell nanostructures, which regulate adsorbed CO intermediates (*CO), offer a promising tandem catalysis pathway to convert CO2 to C2+ products. In this study, we designed Pd@Cu2O/Cu2S yolk-shell catalysts, which demonstrated a Faradaic efficiency (FE) of 81.7 % for C2 products at -0.8 V vs. RHE, with an FE of 44.7 % for ethanol (C2H5OH). This performance is attributed to the synergistic interplay between Pd, which efficiently generates *CO intermediates, and Cu surfaces, which facilitate rapid CC coupling to form C2 products. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), X-ray absorption spectroscopy (XAS), and density functional theory (DFT) calculations further reveal that Pd and S modulate the reaction energy barrier of the *OCCOH intermediate, steering selectivity toward C2 products and enabling partial C1-to-C2 conversion. This research offers a strategy for synthesizing Cu-based tandem catalysts and improving C2 product selectivity of CO2ER.