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A classical density functional study of clustering in ionic liquids at electrified interfaces

Ma, Ke ; Forsman, Jan LU and Woodward, Clifford E. (2017) In Journal of Physical Chemistry C 121(3). p.1742-1751
Abstract

Ion association, leading to the formation of clusters in ionic liquids, is investigated within the framework of classical density functional theory. Clusters are incorporated into a generic coarse-grained model for imidazolium-based ionic liquids confined by planar charged surfaces. We find that the short-ranged structure adjacent to surfaces is remarkably unaffected by the degree of ion association. The physical implications of ion clustering only become apparent in equilibrium properties that depend upon the long-range screening of charge, such as the asymptotic behavior of forces between charged surfaces and the differential capacitance around low surface potentials. Surface forces show a longrange exponential decay, which depends... (More)

Ion association, leading to the formation of clusters in ionic liquids, is investigated within the framework of classical density functional theory. Clusters are incorporated into a generic coarse-grained model for imidazolium-based ionic liquids confined by planar charged surfaces. We find that the short-ranged structure adjacent to surfaces is remarkably unaffected by the degree of ion association. The physical implications of ion clustering only become apparent in equilibrium properties that depend upon the long-range screening of charge, such as the asymptotic behavior of forces between charged surfaces and the differential capacitance around low surface potentials. Surface forces show a longrange exponential decay, which depends primarily on the concentration of nonassociated ions, while the differential capacitance seems to be a sensitive function of the internal structure of clusters. Furthermore, the size of the ion clusters only slightly influences surface forces, but has a significant effect on the differential capacitance. These behaviors would be difficult to observe in simulations due to the system sizes required.

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publication status
published
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in
Journal of Physical Chemistry C
volume
121
issue
3
pages
10 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85022195719
ISSN
1932-7447
DOI
10.1021/acs.jpcc.6b11491
language
English
LU publication?
yes
id
15ad5c21-a4ec-4c45-957a-9f5b3bd0e8b4
date added to LUP
2019-05-27 12:21:59
date last changed
2020-09-23 07:43:21
@article{15ad5c21-a4ec-4c45-957a-9f5b3bd0e8b4,
  abstract     = {<p>Ion association, leading to the formation of clusters in ionic liquids, is investigated within the framework of classical density functional theory. Clusters are incorporated into a generic coarse-grained model for imidazolium-based ionic liquids confined by planar charged surfaces. We find that the short-ranged structure adjacent to surfaces is remarkably unaffected by the degree of ion association. The physical implications of ion clustering only become apparent in equilibrium properties that depend upon the long-range screening of charge, such as the asymptotic behavior of forces between charged surfaces and the differential capacitance around low surface potentials. Surface forces show a longrange exponential decay, which depends primarily on the concentration of nonassociated ions, while the differential capacitance seems to be a sensitive function of the internal structure of clusters. Furthermore, the size of the ion clusters only slightly influences surface forces, but has a significant effect on the differential capacitance. These behaviors would be difficult to observe in simulations due to the system sizes required.</p>},
  author       = {Ma, Ke and Forsman, Jan and Woodward, Clifford E.},
  issn         = {1932-7447},
  language     = {eng},
  month        = {01},
  number       = {3},
  pages        = {1742--1751},
  publisher    = {The American Chemical Society (ACS)},
  series       = {Journal of Physical Chemistry C},
  title        = {A classical density functional study of clustering in ionic liquids at electrified interfaces},
  url          = {http://dx.doi.org/10.1021/acs.jpcc.6b11491},
  doi          = {10.1021/acs.jpcc.6b11491},
  volume       = {121},
  year         = {2017},
}