Defect-Tuned Carbon Layer Thickness Modulates Intermediate Confinement for Enhanced Carbon-Carbon Coupling in CO₂...

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.