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. Graphical TOC Entry

Unified Approach to Implicit and Explicit Solvent Simulations of Electrochemical Reaction Energetics

“…For example, a Volmer reaction event where a constant continuum charge q impl or an additional co-adsorbate with a significant dipole moment is added to the two states considered. As we illustrated in a previous work, 91 the energetics obtained with such a constant charge setup, when considered as a function of Φ between the states considered, are equivalent to the grand canonical energy difference at constant potential. The latter method of charging the interface to achieve constant potential has been applied to a wide variety of surface electrochemical reactions, 75,[103][104][105] since it allows a simple way to probe energetics across a large range of work functions.…”

Double layer charging driven carbon dioxide adsorption limits the rate of electrochemical carbon dioxide reduction on Gold

“…Supplementary Information for a detailed explanation and rationalization of our approach). Implicit solvation schemes have become extremely popular, in particular in electrochemistry 20,[48][49][50][51][52][53] , not only due to their efficiency in treating solvation effects, but also the ability to incorporate simplified representations of countercharges. Here, we obtain the dependence of the reaction states on σ by fitting σ-dependent implicit solvent DFT calculations using a planar countercharge representation via the Environ module 54 of the DFT program package QUANTUM ESPRESSO 55 .…”

Implications of the Fractional Charge of Hydroxide at the Electrochemical Interface

“…The partial ion charge has implications for the potential dependence of reactions involving the ion; for example, coupled proton-electron transfer reactions which can utilize both hydronium and hydroxide as a donor. As we outlined in recent works, 39,40…”