Iodide/triiodide electrochemistry in ionic liquids: Effect of viscosity on mass transport, voltammetry and scanning electrochemical microscopy

► Electrochemical behavior of I −/I 3 − was studied in ionic liquids using a range of electrochemical techniques. ► The ionic liquid viscosity has a drastic effect on the electrochemical behavior of the system. ► Mass transport properties of the ionic liquid electrolytes depend on viscosity. ► Stead...

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Bibliographic Details
Published in:Electrochimica acta 2011-12, Vol.56 (28), p.10313-10320
Main Authors: Ejigu, Andinet, Lovelock, Kevin R.J., Licence, Peter, Walsh, Darren A.
Format: Article
Language:English
Subjects:
Dye-sensitised solar cell
Electrochemistry
Ionic liquid
Ionic liquids
Joining
Microscopy
Oxidation
Scanning
Scanning electrochemical microscopy
Ultramicroelectrode
Viscosity
Voltammetry
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Summary:► Electrochemical behavior of I −/I 3 − was studied in ionic liquids using a range of electrochemical techniques. ► The ionic liquid viscosity has a drastic effect on the electrochemical behavior of the system. ► Mass transport properties of the ionic liquid electrolytes depend on viscosity. ► Steady-state electrochemical responses can be obtained in ionic liquids if the experimental parameters are carefully controlled. The electrochemistry of I −/I 3 − was studied in ionic liquids using a combination of cyclic voltammetry, chronoamperometry and scanning electrochemical microscopy (SECM). The electrolytes were 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C n C 1Im][Tf 2N], ionic liquids (where n = 2, 4 and 8) and I − was typically added at a concentration of approximately 11 mM. During cyclic voltammetry, two sets of peaks were observed in each ionic liquid due to oxidation and reduction of the I −/I 3 − redox couple and oxidation/reduction of the I 3 −/I 2 redox couple. The diffusion coefficients of I − and I 3 −, as determined using chronoamperometry, increased with increasing temperature and decreased with increasing ionic liquid viscosity. The effect of ionic liquid viscosity on ultramicroelectrode (UME) voltammetry was also determined using the I −/I 3 − redox couple. Steady-state behaviour was observed at 1.3 μm UMEs at slow voltammetric scan rates and steady-state SECM feedback approach curves were also obtained at a 1.3 μm Pt SECM tips, provided that the tip approach speed was sufficiently low.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2011.03.108