Nanoconfinement Engineering over Hollow Multi‐Shell Structured Copper towards Efficient Electrocatalytical C−C coupling

Abstract Nanoconfinement provides a promising solution to promote electrocatalytic C−C coupling, by dramatically altering the diffusion kinetics to ensure a high local concentration of C 1 intermediates for carbon dimerization. Herein, under the guidance of finite‐element method simulations results, a series of Cu 2 O hollow multi‐shell structures (HoMSs) with tunable shell numbers were synthesized via Ostwald ripening. When applied in CO 2 electroreduction (CO 2 RR), the in situ formed Cu HoMSs showed a positive correlation between shell numbers and selectivity for C 2+ products, reaching a maximum C 2+ Faradaic efficiency of 77.0±0.3 % at a conversion rate of 513.7±0.7 mA cm −2 in a neutral electrolyte. Mechanistic studies clarified the confinement effect of HoMSs that superposition of Cu shells leads to a higher coverage of localized CO adsorbate inside the cavity for enhanced dimerization. This work provides valuable insights for the delicate design of efficient C−C coupling catalysts.