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

preprint
submitted on 01.07.2019 and posted on 01.07.2019 by Joseph Gauthier, Colin Dickens, Hendrik H. Heenen, Stefan Ringe, Karen Chan

One of the major open challenges in ab initio simulations of the electrochemical interface is the determination of electrochemical barriers under a constant driving force. Existing methods to do so include extrapolation techniques based on fully explicit treatments of the electrolyte, as well as implicit solvent models which allow for a continuous variation in electrolyte charge. Emerging hybrid continuum models have the potential to revolutionize the field, since they account for the electrolyte with little computational cost while retaining some explicit electrolyte, representing a “best of both worlds” method. In this work, we present a unified approach to determine reaction energetics from both fully explicit, implicit, and hybrid treatments of the electrolyte based on a new multi-capacitor model of the electrochemical interface. A given electrode potential can be achieved by a variety of interfacial structures; a crucial insight from this work is that the effective surface charge gives the true driving force of electrochemical processes. In contrast, we show that the traditionally considered work function gives rise to multi-valued functions depending on the simulation cell size. Furthermore, we show that the reaction energetics are largely insensitive to the countercharge distribution chosen in hybrid implicit/explicit models, which means that any of the myriad implicit electrolyte models can be equivalently applied. This work thus paves the way for the accurate treatment of ab initio reaction energetics of general surface electrochemical processes using both implicit and explicit electrolyte.

Funding

Energy Innovation Hub Renewal - Fuels from Sunlight

Basic Energy Sciences

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Department of Energy - DE-AC02-05CH11231

National Science Foundation - DGE-114747

VILLUM FONDEN - 9455

History

Email Address of Submitting Author

jgauth32@stanford.edu

Institution

Stanford University

Country

United States

ORCID For Submitting Author

0000-0001-9542-0988

Declaration of Conflict of Interest

no conflict of interest

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