The structure of the electric double layer: Atomistic versus continuum approaches

Sung Sakong,Axel Groß,Jun Huang,Michael Eikerling

doi:10.1016/j.coelec.2022.100953

Abstract

This article reviews recent forays in theoretical modeling of the double layer structure at electrode/electrolyte interfaces by current atomistic and continuum approaches. We will briefly discuss progress in both approaches and present a perspective on how to better describe the electric double layer by combining the unique advantages of each method. First-principles atomistic approaches provide the most detailed insights into the electronic and geometric structure of electrode/electrolyte interfaces. However, they are numerically too demanding to allow for a systematic investigation of the electric double layers over a wide range of electrochemical conditions. Yet, they can provide valuable input for continuum approaches that can capture the influence of the electrochemical environment on a larger length and time scale due to their numerical efficiency. However, continuum approaches rely on reliable input parameters. Conversely, continuum methods can provide a preselection of interface structures and conditions to be further studied on the atomistic level.

Highlights

Electrochemistry is concerned with structures and processes at the interface between an electron conductor, the electrode, and an ion conductor, the electrolyte [1, 2]
At the interface between a solid electrode and liquid electrolyte, an electric double layer (EDL) is formed by rearranging the electronic charges and ions according to the electrochemical conditions
Because of the large numerical effort associated with the explicit modeling of the atomistic structure, the representative properties of the EDL are usually described by statistically averaged values

Summary

INTRODUCTION

Electrochemistry is concerned with structures and processes at the interface between an electron conductor, the electrode, and an ion conductor, the electrolyte [1, 2]. At the interface between a solid electrode and liquid electrolyte, an electric double layer (EDL) is formed by rearranging the electronic charges and ions according to the electrochemical conditions. One of the most important properties is the electrostatic potential governed by the polarization distribution in the EDL area, created by the electronic and ionic charges. The traditional classical approaches assume a Boltzmann distribution of the ions in the electrolyte and derive the effective electric potential by solving the Poisson equation. There are atomistic approaches which in combination with density functional theory (DFT) can highly accurately evaluate the charge polarization and the electrostatic potential when a suitable atomic configuration is known. We will compare the recent progress of the atomistic and semiclassical continuum approaches and present a perspective of how to integrate findings from both methods for advances of the EDL models in the future

SEMICLASSICAL DENSITY-POTENTIAL FUNCTIONAL THEORY

AIMD SIMULATIONS

BRIDGING AIMD AND SEMICLASSICAL METHODS

CONCLUSION