Practical Considerations for Continuum Models Applied to Surface Electrochemistry

Abstract

Modelling the electrolyte at the electrochemical interface remains a major challenge in ab initio simulations of charge transfer processes at surfaces. Recently, the development of hybrid polarizable continuum models/ab initio models have allowed for the treatment of solvation and electrolyte charge in a computationally efficient way. However, challenges remain in its application. Recent literature has reported that large cell heights are required to reach convergence, which presents a serious computational cost. Furthermore, calculations of reaction energetics require costly iterations to tune the surface charge to the desired potential. In this work, we present a simple capacitor model of the interface that illuminates how to circumvent both of these challenges. We derive a correction to the energy for finite cell heights to obtain the large cell energies at no additional computational expense. We furthermore demonstrate that the reaction energetics determined at constant charge are easily mapped to those at constant potential, which eliminates the need to apply iterative schemes to tune the system to a constant potential. These developments together represent more than an order of magnitude reduction of the computational overhead required for the application of polarizable continuum models to surface electrochemistry.

Solvation at metal/water interfaces: An ab initio molecular dynamics benchmark of common computational approaches

“…Geometry optimizations are conducted on symmetric slabs of four layers with the two central layers fixed. The symmetric cells are used to ensure a reliable determination of the workfunction if continuum solvation is applied 18 . To avoid interactions across periodic images, a vacuum spacing of 10 A on each side of the slab is included.…”

“…If not sampled consistently, the computed solvation energies may not be reliable 16 . Through the combination of static water bilayers with implicit/electrolyte models, a potential control can be introduced [17][18][19][20][21] . AIMD represent a highly accurate, but also a very computationally costly approach.…”

Using pH dependence to understand mechanisms in electrochemical CO reduction

“…Second, no explicit ions have been used in the determination of the reaction barriers, hence we do not include any local interactions between ions and transition states that could potentially be present at the electrode-electrolyte interface. 71 Finally, the calculation of electrochemical barriers on the basis of grand-canonical DFT with a combination of implicit and explicit solvation is still a fairly new concept and further improvements and shortcomings of these methods have already been pointed out in previous work [72][73][74] .…”

Using pH dependence to understand mechanisms in electrochemical CO reduction

“…Second, no explicit ions have been used in the determination of the reaction barriers, hence we do not include any local interactions between ions and transition states that could potentially be present at the electrode-electrolyte interface. 66 Finally, the calculation of electrochemical barriers on the basis of grand-canonical DFT with a combination of implicit and explicit solvation is still a fairly new concept and further improvements and shortcomings of these methods have already been pointed out in previous work 65,67,68 .…”