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Effects of the dipolar double layer on elemental electrode processes at micro- and macro-interfaces

Abstract

Determination of heterogeneous rate constants of redox reactions or charge transfer resistances always involves ambiguities due to participation in double layer (DL) capacitances and solution resistances. The rate constants determined by the steady-state voltammograms at ultra-microelectrodes are inconsistent with time-dependent voltammograms, implying participation of the DL impedance. We examine controlling factors of DLs through the frequency-dependence of the capacitance on the basis of the definition of the current and the capacitance. The capacitance is obeyed by the power law of the frequency. It is controlled by orientation of limited amount of solvent dipoles, independent of salts. Redox species, of which dipoles are oriented oppositely to the solvent dipoles, decrease the DL capacitance and make the value negative at high concentration of the specie. The decrease in the capacitance increases the real impedance, as predicted from the phase angle, yielding an extra resistance. This may be a ghost charge transfer resistance. However, there are a number of actually well-defined charge transfer resistances, which are observed as transferring rates through films on electrodes.

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Publication details

The article was received on 16 Dec 2017, accepted on 29 Jan 2018 and first published on 29 Jan 2018


Article type: Paper
DOI: 10.1039/C7FD00212B
Citation: Faraday Discuss., 2018, Accepted Manuscript
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    Effects of the dipolar double layer on elemental electrode processes at micro- and macro-interfaces

    J. Chen and K. Aoki, Faraday Discuss., 2018, Accepted Manuscript , DOI: 10.1039/C7FD00212B

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