Confinement Catalysis of Reaction Intermediates in Ag@Cu₂O Cascade Nanoreactors toward Boosted Electrochemical C–C Coupling

Cascade nanoreactors provide an ideal platform for multicomponent sequential reactions and synergistic transformations. However, the effects of morphology modulation on confinement catalysis, particularly regarding the generation, diffusion, and dimerization of reaction intermediates in CO2RR are less discerned. Herein, we synthesized a series of Ag@Cu2O cascade nanoreactors with tunable shell thicknesses by a two-step seeded growth method, observing an obvious volcano-type curve in C2+ products generation. The variant with a medium shell thickness (Ag@Cu2O-40) achieved the highest Faradaic efficiency (FE) of C2+ up to 78.5% at −1.6 V (vs RHE). In situ Raman and density functional theory (DFT) calculations indicate that CO generated on the Ag core spills over and becomes confined at the Cu2O shell, which is crucial in boosting C–C coupling rather than forming C1 products (CO, CH3OH, and CH4). Finite element method (FEM) simulations further reveal that the optimal thickness of the Cu2O shell accommodates CO2 diffusion and CO confinement capabilities, thereby maximizing CO concentration for the formation of C2+ products. Our findings exemplify the potential of rationally designed cascade nanoreactors for optimizing reaction intermediates through confinement catalysis.