Nanoconfinement Effects of Yolk–Shell Cu2O Catalyst for Improved C2+ Selectivity and Cu+ Stability in Electrocatalytic CO2 Reduction

Electrocatalytic conversion of carbon dioxide (CO2) to value-added hydrocarbon products provides an industrially viable approach to utilizing carbon resources and the storage of renewable energy. Monovalent copper (Cu+) has been demonstrated to be indispensable for the formation of C2+ products via C–C coupling. However, the C2+ selectivity and stability of Cu+ at the cathodic potential remain a great challenge. In this work, we investigated the electrochemical properties of three Cu-based catalysts with different structures in the electrocatalytic reduction of the CO2 reaction (eCO2RR). Results showed that a Cu2O catalyst with a yolk–shell microstructure having a distance between the shell internal surface and the core external surface of 25 nm displays the best performance. It exhibits a C2+ Faradaic efficiency of 80.2% and a FEC2+ to FEC1 ratio of ∼8.9. Both in situ ATR-SEIRAS and ex situ XPS characterization results reveal that Cu+ is stable under the experimental conditions, and the coverage of adsorbed carbon monoxide (*CO) on the Cu+ active site is enhanced due to nanoconfinement effects. The increased *CO surface coverage significantly promotes C–C coupling, leading to enhanced C2+ selectivity.