Mechanistic aspects of the electron and ion transport processes across the electrode | solid | solvent (electrolyte) interface of microcrystalline decamethylferrocene attached mechanically to a graphite electrode

Alan M. Bond; Frank Marken

doi:10.1016/0022-0728(93)03257-P

Mechanistic aspects of the electron and ion transport processes across the electrode | solid | solvent (electrolyte) interface of microcrystalline decamethylferrocene attached mechanically to a graphite electrode

Alan M. Bond
, Frank Marken

La Trobe University

Research output: Contribution to journal › Article › peer-review

Abstract

The oxidation of water-insoluble microcrystalline decamethylferrocene attached mechanically to a basal plane pyrolytic graphite electrode and then placed in aqueous media has been studied voltammetrically under a wide range of conditions. When dissolved in dichloromethane, the solution-phase voltammetry corresponds to an ideal chemically reversible one electron oxidation process: Fe(ν⁵ - C₅(CH₃)₅)₂ ⇌ [Fe(ν⁵ - C₅(CH₃)₅)₂]⁺ + e^- In contrast, the voltammetry of the solid is far more complex and exhibits a wide range of electrolyte, surface coverage, solvent composition and temperature dependences. Electron probe X-ray measurements show that anions are added to the surface of the solid when Fe(ν⁵ - C₅(CH₃) ₅)₂ is oxidized and expelled on reduction of [Fe(ν⁵ - C₅(CH₃)₅)₂]⁺ so that chemically reversible ion transport across the solvent (electrolyte) boundary provides the mechanism to achieve charge neutralization. The potentials of the reduction and oxidation component of cyclic voltammograms vary considerably with the hydrophobicity of the electrolyte anion, but not the cation, and are also solvent dependent. If the electrolyte contains two anions, it is possible to observe two voltammetric processes. Increasing the scan rate or changing the surface coverage may lead to peak splitting so that both "thin layer" and "thick layer" type voltammetric responses are observed under some conditions. It is concluded that the mechanism for oxidation of microcrystalline decamethylferrocene mechanically attached to an electrode consists of electron transfer from the electrode into the solid|solution interface via the self-exchange mechanism coupled with ion transport across the solution|solid boundary.

Original language	English
Pages (from-to)	125-135
Number of pages	11
Journal	Journal of Electroanalytical Chemistry
Volume	372
Issue number	1-2
DOIs	https://doi.org/10.1016/0022-0728(93)03257-P
Publication status	Published - 8 Jul 1994

Funding

We thank the Alexander von Humboldt foundation and the Australian ResearchC ouncil for financial support of this project. Ulli Englert (Institut fur Anorgan-ische Chemie, RWTH Aachen) is gratefully acknowl-edgedf or providing a sampleo f decamethylferrocene, as is Christopher Reed (Institute of Inorganic Chemistry of the University of Southern California) for sug-gestinga nd offering the carbaboranes alt CsCB,,H,, for use in these investigationsD. enise R. Fernando (School of Agriculture, La Trobe University) and Fred Daniels (Departmento f Botany, La Trobe University) providedt echnicala ssistancea nd advicew hich allowed the electron microscopya nd the electron probe analysis investigationsF.i nally, the authorsa cknowledgeth at valuble and extensived iscussionsw ith Ray Colton and Jan Mocak contributedt o someo f the ideas contained in this paper.

ASJC Scopus subject areas

Analytical Chemistry
General Chemical Engineering
Electrochemistry

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Mechanistic aspects of the electron and ion transport processes across the electrode | solid | solvent (electrolyte) interface of microcrystalline decamethylferrocene attached mechanically to a graphite electrode. / Bond, Alan M.; Marken, Frank.
In: Journal of Electroanalytical Chemistry, Vol. 372, No. 1-2, 08.07.1994, p. 125-135.

Research output: Contribution to journal › Article › peer-review

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abstract = "The oxidation of water-insoluble microcrystalline decamethylferrocene attached mechanically to a basal plane pyrolytic graphite electrode and then placed in aqueous media has been studied voltammetrically under a wide range of conditions. When dissolved in dichloromethane, the solution-phase voltammetry corresponds to an ideal chemically reversible one electron oxidation process: Fe(ν5 - C5(CH3)5)2 ⇌ [Fe(ν5 - C5(CH3)5)2]+ + e- In contrast, the voltammetry of the solid is far more complex and exhibits a wide range of electrolyte, surface coverage, solvent composition and temperature dependences. Electron probe X-ray measurements show that anions are added to the surface of the solid when Fe(ν5 - C5(CH3) 5)2 is oxidized and expelled on reduction of [Fe(ν5 - C5(CH3)5)2]+ so that chemically reversible ion transport across the solvent (electrolyte) boundary provides the mechanism to achieve charge neutralization. The potentials of the reduction and oxidation component of cyclic voltammograms vary considerably with the hydrophobicity of the electrolyte anion, but not the cation, and are also solvent dependent. If the electrolyte contains two anions, it is possible to observe two voltammetric processes. Increasing the scan rate or changing the surface coverage may lead to peak splitting so that both {"}thin layer{"} and {"}thick layer{"} type voltammetric responses are observed under some conditions. It is concluded that the mechanism for oxidation of microcrystalline decamethylferrocene mechanically attached to an electrode consists of electron transfer from the electrode into the solid|solution interface via the self-exchange mechanism coupled with ion transport across the solution|solid boundary.",

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N2 - The oxidation of water-insoluble microcrystalline decamethylferrocene attached mechanically to a basal plane pyrolytic graphite electrode and then placed in aqueous media has been studied voltammetrically under a wide range of conditions. When dissolved in dichloromethane, the solution-phase voltammetry corresponds to an ideal chemically reversible one electron oxidation process: Fe(ν5 - C5(CH3)5)2 ⇌ [Fe(ν5 - C5(CH3)5)2]+ + e- In contrast, the voltammetry of the solid is far more complex and exhibits a wide range of electrolyte, surface coverage, solvent composition and temperature dependences. Electron probe X-ray measurements show that anions are added to the surface of the solid when Fe(ν5 - C5(CH3) 5)2 is oxidized and expelled on reduction of [Fe(ν5 - C5(CH3)5)2]+ so that chemically reversible ion transport across the solvent (electrolyte) boundary provides the mechanism to achieve charge neutralization. The potentials of the reduction and oxidation component of cyclic voltammograms vary considerably with the hydrophobicity of the electrolyte anion, but not the cation, and are also solvent dependent. If the electrolyte contains two anions, it is possible to observe two voltammetric processes. Increasing the scan rate or changing the surface coverage may lead to peak splitting so that both "thin layer" and "thick layer" type voltammetric responses are observed under some conditions. It is concluded that the mechanism for oxidation of microcrystalline decamethylferrocene mechanically attached to an electrode consists of electron transfer from the electrode into the solid|solution interface via the self-exchange mechanism coupled with ion transport across the solution|solid boundary.

AB - The oxidation of water-insoluble microcrystalline decamethylferrocene attached mechanically to a basal plane pyrolytic graphite electrode and then placed in aqueous media has been studied voltammetrically under a wide range of conditions. When dissolved in dichloromethane, the solution-phase voltammetry corresponds to an ideal chemically reversible one electron oxidation process: Fe(ν5 - C5(CH3)5)2 ⇌ [Fe(ν5 - C5(CH3)5)2]+ + e- In contrast, the voltammetry of the solid is far more complex and exhibits a wide range of electrolyte, surface coverage, solvent composition and temperature dependences. Electron probe X-ray measurements show that anions are added to the surface of the solid when Fe(ν5 - C5(CH3) 5)2 is oxidized and expelled on reduction of [Fe(ν5 - C5(CH3)5)2]+ so that chemically reversible ion transport across the solvent (electrolyte) boundary provides the mechanism to achieve charge neutralization. The potentials of the reduction and oxidation component of cyclic voltammograms vary considerably with the hydrophobicity of the electrolyte anion, but not the cation, and are also solvent dependent. If the electrolyte contains two anions, it is possible to observe two voltammetric processes. Increasing the scan rate or changing the surface coverage may lead to peak splitting so that both "thin layer" and "thick layer" type voltammetric responses are observed under some conditions. It is concluded that the mechanism for oxidation of microcrystalline decamethylferrocene mechanically attached to an electrode consists of electron transfer from the electrode into the solid|solution interface via the self-exchange mechanism coupled with ion transport across the solution|solid boundary.

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Mechanistic aspects of the electron and ion transport processes across the electrode | solid | solvent (electrolyte) interface of microcrystalline decamethylferrocene attached mechanically to a graphite electrode

Abstract

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