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 C1 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 C1 intermediates within the catalyst's internal space during the CO2 electroreduction reaction (CO2RR). 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.