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Issue 15, 2012
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New insights into the interface between a single-crystalline metal electrode and an extremely pure ionic liquid: slow interfacial processes and the influence of temperature on interfacial dynamics

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Abstract

Ionic liquids are of high interest for the development of safe electrolytes in modern electrochemical cells, such as batteries, supercapacitors and dye-sensitised solar cells. However, electrochemical applications of ionic liquids are still hindered by the limited understanding of the interface between electrode materials and ionic liquids. In this article, we first review the state of the art in both experiment and theory. Then we illustrate some general trends by taking the interface between the extremely pure ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and an Au(111) electrode as an example. For the study of this interface, electrochemical impedance spectroscopy was combined with in situ STM and in situ AFM techniques. In addition, we present new results for the temperature dependence of the interfacial capacitance and dynamics. Since the interfacial dynamics are characterised by different processes taking place on different time scales, the temperature dependence of the dynamics can only be reliably studied by recording and carefully analysing broadband capacitance spectra. Single-frequency experiments may lead to artefacts in the temperature dependence of the interfacial capacitance. We demonstrate that the fast capacitive process exhibits a Vogel–Fulcher–Tamman temperature dependence, since its time scale is governed by the ionic conductivity of the ionic liquid. In contrast, the slower capacitive process appears to be Arrhenius activated. This suggests that the time scale of this process is determined by a temperature-independent barrier, which may be related to structural reorganisations of the Au surface and/or to charge redistributions in the strongly bound innermost ion layer.

Graphical abstract: New insights into the interface between a single-crystalline metal electrode and an extremely pure ionic liquid: slow interfacial processes and the influence of temperature on interfacial dynamics

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Publication details

The article was received on 07 Dec 2011, accepted on 03 Feb 2012 and first published on 08 Mar 2012


Article type: Discussion
DOI: 10.1039/C2CP40288B
Phys. Chem. Chem. Phys., 2012,14, 5090-5099

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    New insights into the interface between a single-crystalline metal electrode and an extremely pure ionic liquid: slow interfacial processes and the influence of temperature on interfacial dynamics

    M. Drüschler, N. Borisenko, J. Wallauer, C. Winter, B. Huber, F. Endres and B. Roling, Phys. Chem. Chem. Phys., 2012, 14, 5090
    DOI: 10.1039/C2CP40288B

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