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Biphasic electrochemistry of ionic liquids deposited on the electrode surface

Marcin Opallo 1Joanna Niedziolka-Jonsson 1Ewa A. Rozniecka 1Juliette Sirieix-Plenet 2Laurent Gaillon 2

1. Polish Academy of Sciences, Institute of Physical Chemistry, Kasprzaka 44/52, Warszawa 01-224, Poland
2. Universite Pierre et Marie Curie, Place Jussieu, Bat F Boite 39, Paris 75252, France


The room temperature ionic liquids (RTIL) already plays important role as electrochemical solvents. However biphasic electrochemical studies involving RTIL being in contact are rather scarce. This is despite their importance in extraction separation processes Here the results of the electrochemical studies of a redox probe dissolved in RTIL droplet deposited on the gold electrode immersed in an aqueous solution will be presented presented. It is shown that electrode reaction involves heterogeneous electron transfer followed by cation ejection to the aqueous solution or anion insertion to RTIL phase. The contribution of the latter process is judged from the salt concentration dependence of redox potential (E0) and anion dependence of the same parameter. It has been concluded that for most hydrophobic RTIL 1-decyl-3-methylimidazolium bis(trifluoromethyl- sulfonyl)imide insertion of less hydrophilic anion is electrogenerated. In the case of droplet of less hydrophobic 1-butyl-3-methylimidazolium (bmim) hexafluorophosphate and bis(trifluoromethylsulfonyl)imide ejection of bmim+ cation dominates. This behaviour is similar to that observed for drop or droplets undiluted and diluted organic liquid. The order or transfer potentials of anion across RTIL-water interface is similar to that observed for nitrobenzene-water interface. The electrochemical behaviour of analogous system based salt solution in hydrophobic solvent (2-nitrophenyl octyl ether) will be also presented and compared.


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Presentation: Keynote lecture at SMCBS'2005 Workshop, by Marcin Opallo
See On-line Journal of SMCBS'2005 Workshop

Submitted: 2005-07-26 08:00
Revised:   2009-06-07 00:44