Defect-Tuned Carbon Layer Thickness Modulates Intermediate Confinement for Enhanced Carbon–Carbon Coupling in CO₂ Electroreduction to Ethanol

The carbon-layer-induced intermediate escape confinement effect improves electrocatalytic C–C coupling by reducing the diffusion of C 1 intermediates, thereby maintaining a high local concentration of these intermediates. Guided by finite element analysis simulations, CuSn(OH) 6 @C was synthesized with varying carbon layer thicknesses. The findings demonstrate that the thickness of the carbon layer significantly influences the diffusion behavior of C 1 intermediates within the catalyst’s internal space during the CO 2 electroreduction reaction (CO 2 RR). A catalyst with a defective carbon layer measuring 21 nm achieved a Faradaic efficiency of 65.8% for ethanol in a flow cell operating at a current density of 300 mA cm –2 . In situ FTIR, EIS, and time-relaxation distribution analyses revealed that the carbon layer suppresses CO* escape, enhancing the coverage of CO* within the catalyst and limiting early-stage reaction kinetics. This study provides valuable insights for the design of efficient catalysts to promote C–C coupling.