Electrochemical electron transfer: Accounting for electron–hole excitations in the metal electrode

Abstract

The transfer of an electron from a metal electrode to an ion in a polar liquid is probably the most important process in electrochemistry. As the electrons in the metal have a continuum of allowed energy levels, this transfer may be accompanied by the creation/annihilation of electron–hole excitations in the metal. Calculation of the rate of electron transfer, with these excitations and the solvent accounted for properly is a difficult problem to treat using the usual approaches of molecular reaction dynamics, as one now has a continuum of potential energy surfaces, on which the dynamics has to be considered. We suggest an approach in which the electron–hole excitations are treated as bosons. Using this, we have derived an expression for the rate, which accounts both for solvent dynamics and electron–hole excitations. Our analysis amounts to a solution of the problem of calculating the electronic transmission coefficient κ, for a continuum of crossing diabatic surfaces. Calculations of the rate using our expression are reported.

Key findings

• ▸The transfer of an electron from a metal electrode to an ion in a polar liquid is a complex process that involves the creation/annihilation of electron-hole excitations in the metal.
• ▸The usual approaches of molecular reaction dynamics are insufficient to treat this process, as they do not account for the continuum of potential energy surfaces.
• ▸The proposed approach treats electron-hole excitations as bosons and derives an expression for the rate of electron transfer that accounts for both solvent dynamics and electron-hole excitations.

Keywords

Identifiers

DOI

10.1063/1.456547

Journal

The Journal of Chemical Physics

Year

1989