Standard electrode potential, Tafel equation, and the solvation thermodynamics

Journal Article · Sun Jun 21 00:00:00 EDT 2009 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3152847· OSTI ID:21559734

Matyushov, Dmitry V ^[1]

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1. Center for Biological Physics, Arizona State University, P.O. Box 871504, Tempe, Arizona 85287-1504 (United States)

Equilibrium in the electronic subsystem across the solution-metal interface is considered to connect the standard electrode potential to the statistics of localized electronic states in solution. We argue that a correct derivation of the Nernst equation for the electrode potential requires a careful separation of the relevant time scales. An equation for the standard metal potential is derived linking it to the thermodynamics of solvation. The Anderson-Newns model for electronic delocalization between the solution and the electrode is combined with a bilinear model of solute-solvent coupling introducing nonlinear solvation into the theory of heterogeneous electron transfer. We therefore are capable of addressing the question of how nonlinear solvation affects electrochemical observables. The transfer coefficient of electrode kinetics is shown to be equal to the derivative of the free energy, or generalized force, required to shift the unoccupied electronic level in the bulk. The transfer coefficient thus directly quantifies the extent of nonlinear solvation of the redox couple. The current model allows the transfer coefficient to deviate from the value of 0.5 of the linear solvation models at zero electrode overpotential. The electrode current curves become asymmetric in respect to the change in the sign of the electrode overpotential.

• OSTI ID: 21559734
• Journal Information: Journal of Chemical Physics, Vol. 130, Issue 23; Other Information: DOI: 10.1063/1.3152847; (c) 2009 American Institute of Physics; ISSN 0021-9606
• Country of Publication: United States
• Language: English

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37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CHARGE EXCHANGE
ELECTROCHEMISTRY
ELECTRODES
ELECTRON TRANSFER
ELECTRONIC STRUCTURE
EQUATIONS
EQUILIBRIUM
FREE ENERGY
METALS
NONLINEAR PROBLEMS
OXIDATION
POTENTIALS
REACTION KINETICS
REDUCTION
SOLUTES
SOLUTIONS
SOLVATION
SOLVENTS
STANDARDS
THERMODYNAMICS
CHEMICAL REACTIONS
CHEMISTRY
DISPERSIONS
ELEMENTS
ENERGY
HOMOGENEOUS MIXTURES
KINETICS
MIXTURES
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES