The frequency factor for outer-sphere electrochemical reactions

Joseph T Hupp, Michael J. Weaver

Research output: Contribution to journalArticle

136 Citations (Scopus)

Abstract

The conventional formulation of the frequency factor Ae n for outer-sphere electrochemical reactions based on a "collisional" model is compared with an alternative "encounter preequilibrium" treatment whereby Ae n is determined by the effective frequency of surmounting the free energy barrier within a previously assembled precursor state. The latter model is shown to provide a more appropriate description for electrochemical reactions under most conditions, in harmony with analogous considerations for homogeneous redox processes. Noticeably (ca. 20-fold) larger values of Ae n are derived from the encounter preequilibrium as compared to the collisional model. Numerical relationships between the kinetics of corresponding electrochemical and homogeneous reactions and of competing inner- and outer-sphere electrochemical pathways that are significantly different from the conventional relations are also predicted on the basis of the encounter preequilibrium model. The relationships between Ae n and experimental frequency factors obtained from the temperature dependence of electrochemical rate constants are also considered in the light of these considerations.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalJournal of Electroanalytical Chemistry
Volume152
Issue number1-2
Publication statusPublished - Aug 25 1983

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Energy barriers
Free energy
Rate constants
Kinetics
Temperature
Oxidation-Reduction

ASJC Scopus subject areas

  • Electrochemistry
  • Analytical Chemistry
  • Chemical Engineering(all)

Cite this

The frequency factor for outer-sphere electrochemical reactions. / Hupp, Joseph T; Weaver, Michael J.

In: Journal of Electroanalytical Chemistry, Vol. 152, No. 1-2, 25.08.1983, p. 1-14.

Research output: Contribution to journalArticle

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