The frequency factor for outer-sphere electrochemical reactions

Joseph T. Hupp, Michael J. Weaver

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Abstract

The conventional formulation of the frequency factor Ane for outer-sphere electrochemical reactions based on a "collisional" model is compared with an alternative "encounter preequilibrium" treatment whereby Ane 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 Ane 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 Ane 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
DOIs
Publication statusPublished - Aug 25 1983

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ASJC Scopus subject areas

  • Analytical Chemistry
  • Chemical Engineering(all)
  • Electrochemistry

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