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Potential dependent capacitance of [EMIM][TFSI], [N 1114][TFSI] and [PYR 13][TFSI] ionic liquids on glassy carbon

Potential dependent capacitance of [EMIM][TFSI], [N 1114][TFSI] and [PYR 13][TFSI] ionic liquids on glassy carbon

Jeffrey M Klein, Evio Panichi, Burcu Gurkan

Phys Chem Chem Phys. 2019 Feb 13;21(7):3712-3720.

PMID: 30334051

Abstract:

Differential capacitances of ionic liquids (ILs) butyl-trimethylammonium bis(trifluoromethyl sulfonyl)imide, [N1114][TFSI], methyl-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [PYR13][TFSI], and ethyl- methylimidazolium 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 the point of zero charge with applied potential as a result of the '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 [Z. A. Goodwin, et al., Electrochim. Acta., 2017, 225, 190-197] reveals that the ILs with increased ion associations demonstrate the largest relative increase in capacitance with potential.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP258273755	Butyltrimethylammonium bis(trifluoromethylsulfonyl)imide		258273-75-5	Price

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