Modeling charged electrochemical interfaces requires a detailed model of the electrochemical capacitance to connect the interface charge with the applied electrode potential. However, accounting for the capacitance contributions from ion adsorption, solvent dielectric response and electrode surface polarization remains a challenge. In particular, atomistic modeling of electrochemical capacitance is complicated by the requirement of large simulation cells to contain statistically significant number of ion pairs in the electrolyte, and long simulation times for adequate equilibration. We perform large ensembles of long-time classical molecular dynamics simulations to accurately predict the equilibrium density and electrostatic potential profiles of an idealized electrochemical interface -- Ag(100) in a non-adsorbing NaF electrolyte -- as a function of electrode charge. This allows us to predict the idealized electrochemical capacitance of this interface and identify the contributions of ionic and solvent responses to the net differential capacitance. In addition to interpreting capacitance measurements, these simulations establish the requirements for reliable molecular dynamics modeling of electrochemical phenomena and inform first-principles treatment of electrochemistry based on implicit and explicit solvent models.

Capacitance of idealized aqueous electrochemical interfaces from molecular dynamics simulations

ACS Spring Meeting 2021

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