A semiclassical Thomas-Fermi model to tune the metallicity of electrodes in molecular simulations

TL;DR

This paper introduces a semiclassical Thomas-Fermi model to adjust electrode metallicity in molecular simulations, enabling better analysis of interfacial electrochemical properties relevant to energy storage devices.

Contribution

It presents a novel application of the Thomas-Fermi model to differentiate metallic screening effects in electrode/electrolyte interfaces within molecular dynamics simulations.

Findings

Screening significantly affects interfacial capacitance.

Electrode metallicity influences electrolyte structure and dynamics.

Model enables quantitative predictions of capacitive properties.

Abstract

Spurred by the increasing needs in electrochemical energy storage devices, the electrode/electrolyte interface has received a lot of interest in recent years. Molecular dynamics simulations play a proeminent role in this field since they provide a microscopic picture of the mechanisms involved. The current state-of-the-art consists in treating the electrode as a perfect conductor, precluding the possibility to analyze the effect of its metallicity on the interfacial properties. Here we show that the Thomas-Fermi model provides a very convenient framework to account for the screening of the electric field at the interface and differenciating good metals such as gold from imperfect conductors such as graphite. All the interfacial properties are modified by screening within the metal: the capacitance decreases significantly and both the structure and dynamics of the adsorbed electrolyte are affected. The proposed model opens the door for quantitative predictions of the capacitive properties of materials for energy storage.