Refining Free-Energy Calculations for Electrochemical Reactions: Unveiling Corrections beyond Gas-Phase Errors for Solvated Species and Ions
Year: 2024
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide As much of the theory related to computational electrocatalysis has been adapted from the thermodynamics of gas-phase reactions, it demands careful treatment and the implementation of proper corrections when investigating electrochemical systems. In this article, we present a comprehensive thermodynamic framework that incorporates all potential phases (gaseous or aqueous) and different forms (molecular or ionic) of reactants and products under ambient conditions. This framework elucidates systematic relationships governing the Gibbs free energy of reactants or products across diverse phases and different chemical species, employing Henry’s volatility constant ( K H or H ), acid dissociation constant ( K a ), and pH . We introduce a method for calculating both K H and K a, detailing the associated challenges. Our study demonstrates that the calculation of free energies is influenced by K a and pH, primarily due to the occurrence of unbalanced numbers of electrons and protons transfers during adsorption or desorption of ions. Our findings also highlight that the inclusion of aqueous reactants and products, whether in molecular or ionic form, significantly modifies the free-energy landscapes. In turn, the reported solvation and ion corrections are imperative to obtain correct activity predictions by descriptors such as the thermodynamic overpotential or the span model of G max (η), as deviations of more than 0.3 eV are observed if these contributions are ignored.
Authors: Ebrahim Tayyebi, Kai S. Exner
Institution: University of Duisburg-Essen
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4401452021