A comparative electrochemical study of diffusion in room temperature ionic liquid solvents versus acetonitrile

Russell G. Evans, Oleksiy V. Klymenko, Paul D. Price, Stephen G. Davies, Christopher Hardacre, Richard G. Compton

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Measurements on the diffusion coefficient of the neutral molecule N,N,N′,N′-tetramethyl-para-phenylenediamine and the radical cation and dication generated by its one- and two-electron oxidation, respectively, are reported over the range 298-348 K in both acetonitrile and four room temperature ionic liquids (RTILs). Data were collected using single and double potential step chronoamperometry at a gold disk electrode of micrometer dimension, and analysed via fitting to the appropriate analytical expression or, where necessary, to simulation. The variation of diffusion coefficient with temperature was found to occur in an Arrhenius type manner for all combinations of solute and solvent. For a given ionic liquid, the divisional activation energies of each species were not only closely equivalent to each other, but also to the RTIL's activation energy of viscous flow. In acetonitrile supported with 0.1 M tetrabutylammonium perchlorate, the ratio in diffusion coefficients of the radical cation and dication to the neutral molecule were calculated as 0.89±0.05 and 0.51±0.03, respectively. In contrast, amongst the ionic liquids the same ratios were determined to be on average 0.53±0.04 and O.33± 0.03. The consequences of this dissimilarity are considered in terms of the modelling of voltammetric data gathered within ionic liquid solvents.

    Original languageEnglish
    Pages (from-to)526-533
    Number of pages8
    JournalChemPhysChem
    Volume6
    Issue number3
    DOIs
    Publication statusPublished - Mar 2005

    Keywords

    • Activation energy
    • Diffusion coefficient
    • Electrochemistry
    • Ionic liquids
    • N,N,N′,N′-tetramethyl-para-phenylenediamine

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