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The electrical double layer (EDL) has long been known to influence observed rates of electrocatalysis, but a complete understanding of its role has been elusive due to the complex, multicomponent interactions that dictate double layer structure. To resolve these effects, we bridge electrochemical transport theory and Marcus–Hush–Chidsey theory from the nano- to mesoscale to model the EDL structure and its effects during the electroreduction of CO2 to CO over Ag catalysts. The model exhibits strong agreement between predicted and experimental CO2 reduction rates as a function of cation identity, CO2 partial pressure, and electrolyte concentration, along with spectroscopic measurements of the microenvironment at the Ag surface (e.g., local pH and CO2 activity), all without the need for empirical fit parameters. The model reveals that small, hydrated cations (Cs+ and K+) pack tightly in the EDL and enable large electric fields, which polarize water molecules in the Stern layer. This polarization reduces the energy for water reorganization and, in turn, the transition state barrier for reductive CO2 adsorption. These findings implicate solvent reorganization as a principal phenomenon that governs the impact of EDL structure on catalysis, emphasizing the need for multiscale understanding in the study of complex catalytic interfaces.
King et al. (Thu,) studied this question.