Investigating the Electrochemical Double Layer with Quantum-Chemical Simulations and Implicit Solvation Models

TL;DR

This study evaluates the DRISM implicit electrolyte model for electrochemical double layer simulation, comparing it with other models and emphasizing the importance of pair-specific parameters for accuracy.

Contribution

It introduces the use of pair-specific metal-ion parameters in DRISM, improving model accuracy over traditional mixing rules.

Findings

Lorentz-Berthelot rules lead to excessive Na+ accumulation.

Pair-specific parameters yield more symmetric charging behavior.

Using pair-specific parameters enhances model flexibility and accuracy.

Abstract

We assess the dielectrically consistent reference interaction site model (DRISM) as an implicit electrolyte framework for modeling the electrochemical double layer, and compare it with the Poisson-Boltzmann model and explicit molecular dynamics results from the literature. We use the gold-electrolyte interface as the main test case and analyze solvent and ionic density profiles, the differential capacitance, and the solvation contribution to CO adsorption. The results show a strong sensitivity to the Lennard-Jones parametrization of metal-ion and metal-water interactions. In particular, we find that the default Lorentz-Berthelot mixing rules to be inadequate and lead to excessive Na+ accumulation at the interface, which results in an increase of the differential capacitance at negative electrode potentials. We demonstrate that introducing pair-specific metal-ion parameters yields more symmetric charging behavior and provides greater flexibility. Our findings suggest that using pair-specific parameters, rather than relying on Lorentz-Berthelot mixing rules, improves the accuracy of the model and opens the way for future studies with this improved yet equally performant model.