SIPS 2018

DETAILLED PROGRAM OVERVIEW

X-ray Photoelectron Spectroscopy of Ionic Liquids – From Half-cell Measurements to In-situ Electrochemical XPS
Annette Foelske Schmitz¹;
¹TU WIEN, 1060 Vienna, Austria;
PAPER: 6/Molten/Invited (Oral)
SCHEDULED: 16:20/Tue./Bossa (150/3rd)

ABSTRACT:
X-ray Photoelectron Spectroscopy (XPS) is widely accepted to be a powerful tool to study electrochemically induced changes of the electrode/electrolyte interface as it is very surface sensitive, allows for quantitative analysis and assignment of oxidation states or chemical environment of the detected species. As electrochemical experiments are commonly performed under atmospheric pressure using liquid electrolytes that are not ultrahigh vacuum (UHV) compatible, XPS can usually not be applied directly in the analyser chamber of the spectrometer and one may distinguish three experimental approaches, that are (i) transfer of the electrode into the UHV system via air contact, also referred to ex situ analysis, (ii) transfer of the electrode under inert conditions, also referred to as quasi in situ approach, and (iii) performing electrochemistry directly in the analyser chamber of the spectrometer, also referred to as in situ EC XPS [1]. The in situ approach may be realized using ambient pressure XPS or UHV compatible electrolytes such as ionic liquids (IL). Ionic liquids are also known to provide large electrochemical stability windows making them attractive for electrochemical applications such as electrochemical double layer capacitors (EDLC) [2]. In order to elucidate the electrochemical stability windows of carbon/IL systems in detail, quasi in situ [3] and in situ [4] EC XPS setups were realized. The setups and results as well as recently performed XPS half-cell measurements of IL [5] will be presented and discussed with respect to their opportunities and limits, interfacial processes and interpretation of XPS data.

References:
[1] A. Foelske-Schmitz, X-Ray Photoelectron Spectroscopy in Electrochemistry Research, Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, Elsevier, ISBN: 978-0-12-409547-2, (2017)
[2] D. Weingarth, H. Noh, A. Foelske-Schmitz, A. Wokaun, R. Kötz, Electrochim. Acta 103 119 (2013)
[3] A. Foelske-Schmitz, D. Weingarth, R. Kötz, Electrochim. Acta 56 1032 (2011)
[4] D. Weingarth, A. Foelske-Schmitz, A. Wokaun, R. Kötz, Electrochem. Commun. 13 619 (2011)
[5] A. Foelske-Schmitz, M. Sauer, J. Electron Spectrosc. Relat. Phenom. (2017) in press