@article{cb87915433c84d0cbf9e9d000152abc4,
title = "The prediction of electrochemical reactivities from contemporary theory: some comparisons with experiment",
abstract = "The application of current theoretical treatments of electron transfer to outer-sphere electrochemical reactions are considered with regard to the numerical prediction of rate parameters from thermodynamic and structural data. Formalisms based on a {"}semiclassical{"} treatment for the Franck-Condon barrier together with an {"}encounter preequilibrium{"} model for the preexponential factor are summarized and related to the more widely considered treatments for homogeneous redox reactions. Comparisons are made between the theoretical predictions and experimental rate parameters for representative inorganic outer-sphere reactions at electrode surfaces, and with relative reactions in homogeneous solution. The effects of altering the electrode material and the outer-shell solvent are also considered. Although the measured rate parameters for several reactions at mercury electrodes are in reasonable agreement with the theoretical predictions, significant and even large discrepancies are seen for a number of cases. Likely reasons for these findings are discussed, including nonadiabaticity and specific solvation effects.",
author = "Hupp, {J. T.} and Liu, {H. Y.} and Farmer, {J. K.} and T. Gennett and Weaver, {M. J.}",
note = "Funding Information: Although-not particularly extensive, the foregoing comparisons illustrate some major virtues of undertaking absolute as well as relative tests <of_ electron-transfer theory for electrochemical reactions: Despite..the provocative assertions of-some C347, contemporary theory can yield reasonable agreement with experimental data .at least for some outer-sphere reactions at mercury electrodes-Nevertheless, a number of interesting discrepancies remain-The commonf inding.that kCOrr -= kc,,, and A,,,, < Acalc probably-arises in part from nonadiabaticity, i.e.. ke, < 1. The relative importance of other factors is difficult to gauge at present; The solvent reorganization barrier may often be significantly larger than that predicted from the dietectric continuum model_ The observed discrepancies between experiment and theory may be associated as much with the limitations of electrostatic models in estimating the work terms (i.e., {"}double-layer{"} effects) as with the deficiencies of the electron-transfer model itself. However, paral 1 el discrepancies between experiment and theory are also seen with ferricinium-ferrocene redox couples at electrodes in solution for which the work terms are liable to be small [35]_ It would clearly be desirable to refine the theoretical they pertain to electrochemical as well as homogeneous outer-sphere reactions, especially with regard to the electron-tunneling aspects. Hever-theless, the kinetic formalisms underlying the present theoretical treatment offer considerable, so far unexploited, opportunities for examining the fundamental features of electrochemical and homogeneous processes on a commonb asis. In turn, such activities should spur the acquisition of the further electrochemical kinetic data, including activation parameters as well as rate constants, that is critical to the development of a truly molecular-based understanding of electrode processes_ ACKNOWLEDGMENTS We are grateful to Dr_ J_ I:_ Beattie for conununicating some vibrational spectroscopic data c40]. This work Is supported in part by the Air Force of Scientific Research and the Office of Naval Research-M.J.W. acknowledges a fellowship from the Alfred P. Sloan Foundation.",
year = "1984",
month = may,
day = "25",
doi = "10.1016/0368-1874(84)87107-5",
language = "English (US)",
volume = "168",
pages = "313--334",
journal = "Journal of Electroanalytical Chemistry",
issn = "0368-1874",
publisher = "Elsevier Sequoia",
number = "1-2",
}