Abstract
Impedance spectra (50 kHz-1 Hz) were acquired and used to obtain the differential capacitance at the interfaces between 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6] ionic liquid and three different electrode materials (Hg, Pt, and glassy carbon (GC)) as a function of the applied potential. The electrocapillary curve for the Hg/[BMIM][PF6] interface was obtained from drop time measurements, from which the potential of zero charge was calculated to be -0.39 V (Ag wire). The potential of zero charge is 0.30 V less negative than the potential of differential capacitance minimum. This disagreement suggests that the differential capacitance minimum is not related to a classical diffuse layer minimum. Additional support to this conclusion was obtained from positive temperature coefficient for the differential capacitance in contrast to the negative temperature predicted by the classic Gouy-Chapman model. The results do not support the recent model predictions of bell shaped capacitance curves for room temperature ionic liquids, RTILs.
Original language | English |
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Pages (from-to) | 153-160 |
Number of pages | 8 |
Journal | Journal of Electroanalytical Chemistry |
Volume | 622 |
Issue number | 2 |
DOIs | |
Publication status | Published - 15 Oct 2008 |
Externally published | Yes |
Keywords
- Differential capacitance
- Double layer
- Ionic liquids
- Temperature