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A comparative AFM study of the interfacial nanostructure in imidazolium or pyrrolidinium ionic liquid electrolytes for zinc electrochemical systems

journal contribution
posted on 2016-01-01, 00:00 authored by Srdan Begic, H Li, R Atkin, A F Hollenkamp, Patrick HowlettPatrick Howlett
The electrochemical systems containing zinc dicyanamide salt (Zn(dca)2) in both 1-ethyl-3-methylimidazolium dicyanamide ([C2mim][dca]) and N-butyl-N-methylpyrrolidinium dicyanamide ([C4mpyr][dca]) ionic liquids (ILs) have been studied by atomic force microscopy (AFM) on a highly oriented pyrolytic graphite (HOPG) surface under different conditions and applied potentials. The results reveal the following: (1) interfacial layers exist in both ILs, even after the addition of 3 wt% water and 9 mol% Zn(dca)2 salt. (2) The number of layers is different for the different ILs, with the [C2mim][dca]-based samples exhibiting a much more limited interfacial structure compared to the [C4mpyr][dca] at almost all of the tested conditions. (3) For the [C4mpyr][dca]-based samples, without added zinc salt, the number of detected interfacial layers increases with negative potential. With added zinc, the [C4mpyr][dca] sample shows about the same number of layers independent of the applied potentials, namely between 5-7. Likewise, for the [C2mim][dca] samples, with the zinc added the sample shows the same number of layers at the applied potentials, but for this system only 1-2 layers are detected. And (4) the addition of Zn(dca)2 into the [C2mim][dca] IL does not cause a large change in the interfacial ordering, whereas the addition of the same salt into the [C4mpyr][dca] samples is marked by a stark increase in both the number and the consistency of the perceived interfacial layers. These results are significant because they show a marked difference in the interfacial nanostructure between two zinc-based electrochemical systems that were previously shown to have distinctly different electrochemical behaviour, despite their chemical similarity.

History

Journal

Physical chemistry chemical physics

Volume

18

Issue

42

Pagination

29337 - 29347

Publisher

Royal Society of Chemistry

Location

London, Eng.

ISSN

1463-9076

eISSN

1463-9084

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2016, Owner Societies

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