Influence of CO adsorption on the structure of electric double layer on Cu surface.

[Display omitted] • The impact of CO adsorption on electric double layer on Cu. • In situ spectroscopic and electrochemical impedance characterizations. • CO adsorption reduces electric double layer capacitance and local cation density. • CO adsorption leads to thicker electric double layer and lower dielectric constant. Understanding the interplay between reactant adsorbate and structure of the electric double layer (EDL) is crucial as it plays a key role in determining the efficiency and kinetics of heterogeneous electrocatalytic reactions. In this context, our study presents a comprehensive experimental analysis of the EDL structure and its interaction with CO adsorption on Cu surfaces. Utilizing in situ surface-enhanced infrared absorption spectroscopy (SEIRAS) and electrochemical impedance characterizations, we investigate the impact of CO adsorption on EDL properties at various CO pressures. Our findings demonstrate a significant decrease in EDL capacitance with increased CO adsorption, linked to reduced cation density, increased EDL thickness, and weakened interfacial electric field strength. Additionally, we observed a considerable decline in the relative dielectric constant of the EDL, which is likely attributable to the influence of adsorbed CO altering the dielectric properties of the medium. These results emphasize the critical role of adsorbate-EDL interactions in electrocatalytic processes, providing new insights into these complex dynamics. [ABSTRACT FROM AUTHOR]