Theory of the electrostatic surface potential and intrinsic dipole moments at the mixed ionic electronic conductor (MIEC)–gas interface

Abstract

The local activation overpotential describes the electrostatic potential shift away from equilibrium at an electrode/electrolyte interface. This electrostatic potential is not entirely satisfactory for describing the reaction kinetics of a...

New insights into the kinetics of metal|electrolyte interphase growth in solid-state-batteries via an operando XPS analysis - part II: modelling

“…The activity (a = γc) is the product of the concentration and activity coefficient which is a measure of the non-ideality of the species. 1,2 Here, we use the definition of (electro)chemical potential, meaning that if the species of interest is charged, we find the electrochemical potential, and if the species of interest is neutral, we find the chemical potential. At the electrode-electrolyte interface, the activation overpotential (η) describes the nonequilibrium shift in electrostatic potential between the electrons and ions for the general reduction reaction O n+ + ne − → R as:…”

“…The rate of electrochemical reactions is often described by the phenomenological Butler-Volmer (BV) equation, which was originally derived based on transition state theory to model the rate of ion transfer (IT). [1][2][3][4][5][6] Here, the rate of ion migration over an activation barrier is determined through classical statistical thermodynamics devised of an attempt frequency and a success probability determined by the thermal energy of the system. Marcus theory explicitly described electron transfer (ET) as a tunnelling event which occurs when the reduced and oxidised states are iso-energetic.…”

Electric Fields and Charge Separation for Solid Oxide Fuel Cell Electrodes

“…The formation of the electrostatic surface potential can be described as the difference in electrostatic potential of the electrode (ϕ ode ) and the adsorbate (ϕ ad ): 12,15 χ = ϕ ode − ϕ ad (10) Under bias, an electrostatic potential shift is defined at the surface as:…”

“…In a previous study, we determined that the electrostatic surface potential had a profound influence on the gas reduction kinetics, where a relationship |∆χ/η act | > 0 is desirable. 12 Few experiments have investigated the complex ∆χ − η act relationship, leaving this phenomenon poorly understood despite its kinetic merit. [12][13][14][15][16] By analysing the shift in outer work function using in operando X-ray photoelectron spectroscopy (XPS) over an applied overpotential range, Feng et al measured the ∆χ − η act relationship for three different electroreduction systems illustrated in Fig.…”

“…12 Few experiments have investigated the complex ∆χ − η act relationship, leaving this phenomenon poorly understood despite its kinetic merit. [12][13][14][15][16] By analysing the shift in outer work function using in operando X-ray photoelectron spectroscopy (XPS) over an applied overpotential range, Feng et al measured the ∆χ − η act relationship for three different electroreduction systems illustrated in Fig. 2 (mechanistic details given in Table 1 and Table S1).…”