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Potential dependent capacitance of [EMIM][TFSI], [N1114][TFSI] and [PYR13][TFSI] ionic liquids on glassy carbon

Abstract

Differential capacitance of the ionic liquids (ILs) butyl-trimethylammonium bis(trifluoromethyl sulfonyl)imide, [N1114][TFSI], methyl-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [PYR13][TFSI], and ethyl-methylimidizolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI], were measured by electrochemical impedance spectroscopy (EIS) over the entire electrochemical window determined by cyclic voltammetry (CV). Distinct fast charging and discharging process frequencies were obtained from the complex capacitance plane extracted from EIS. The onset frequencies of the charging processes were found to be independent of the bulk viscosity of the liquid. [N1114][TFSI] showed the largest relative increase in capacitance with respect to point of zero charge with applied potential as a result of ‘crowding’ effect. This is attributed to a larger degree of rotational freedom associated with the independent alkyl chains and the accessibility of larger potentials with the more stable cation. The largest overall capacitance among the ILs studied was observed for [PYR13][TFSI] at its anodic maximum which occurs due to ‘overscreening’. The interpretation of the measured differential capacitance according to the extended mean field theory of Goodwin-Kornyshev [Goodwin, Z. A.; et al. Electrochim. Acta. 2017, 225, 190−197] reveal that the ILs with increased ion associations demonstrate the largest relative increase in capacitance with potential.

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Publication details

The article was received on 21 Jul 2018, accepted on 02 Oct 2018 and first published on 02 Oct 2018


Article type: Paper
DOI: 10.1039/C8CP04631J
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Potential dependent capacitance of [EMIM][TFSI], [N1114][TFSI] and [PYR13][TFSI] ionic liquids on glassy carbon

    J. M. Klein, E. A. Panichi and B. Gurkan, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP04631J

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