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Electron spectroscopy of ionic liquids : Experimental identification of atomic orbital contributions to valence electronic structure

Fogarty, Richard M. ; Palgrave, Robert G. ; Bourne, Richard A. ; Handrup, Karsten LU ; Villar-Garcia, Ignacio J. ; Payne, David J. ; Hunt, Patricia A. and Lovelock, Kevin R.J. (2019) In Physical Chemistry Chemical Physics 21(35). p.18893-18910
Abstract

The atomic contributions to valence electronic structure for 37 ionic liquids (ILs) are identified using a combination of variable photon energy XPS, resonant Auger electron spectroscopy (RAES) and a subtraction method. The ILs studied include a diverse range of cationic and anionic structural moieties. We introduce a new parameter for ILs, the energy difference between the energies of the cationic and anionic highest occupied fragment orbitals (HOFOs), which we use to identify the highest occupied molecular orbital (HOMO). The anion gave rise to the HOMO for 25 of the 37 ILs studied here. For 10 of the ILs, the energies of the cationic and anionic HOFOs were the same (within experimental error); therefore, it could not be determined... (More)

The atomic contributions to valence electronic structure for 37 ionic liquids (ILs) are identified using a combination of variable photon energy XPS, resonant Auger electron spectroscopy (RAES) and a subtraction method. The ILs studied include a diverse range of cationic and anionic structural moieties. We introduce a new parameter for ILs, the energy difference between the energies of the cationic and anionic highest occupied fragment orbitals (HOFOs), which we use to identify the highest occupied molecular orbital (HOMO). The anion gave rise to the HOMO for 25 of the 37 ILs studied here. For 10 of the ILs, the energies of the cationic and anionic HOFOs were the same (within experimental error); therefore, it could not be determined whether the HOMO was from the cation or the anion. For two of the ILs, the HOMO was from the cation and not from the anion; consequently it is energetically more favourable to remove an electron from the cation than the anion for these two ILs. In addition, we used a combination of area normalisation and subtraction of XP spectra to produce what are effectively XP spectra for individual ions; this was achieved for 10 cations and 14 anions.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Chemistry Chemical Physics
volume
21
issue
35
pages
18 pages
publisher
Royal Society of Chemistry
external identifiers
  • pmid:31441923
  • scopus:85072025519
ISSN
1463-9076
DOI
10.1039/c9cp02200g
language
English
LU publication?
yes
id
7a6fe5a3-40e5-4194-91a2-ead3f77eb20c
date added to LUP
2022-03-29 15:53:15
date last changed
2024-06-05 16:57:26
@article{7a6fe5a3-40e5-4194-91a2-ead3f77eb20c,
  abstract     = {{<p>The atomic contributions to valence electronic structure for 37 ionic liquids (ILs) are identified using a combination of variable photon energy XPS, resonant Auger electron spectroscopy (RAES) and a subtraction method. The ILs studied include a diverse range of cationic and anionic structural moieties. We introduce a new parameter for ILs, the energy difference between the energies of the cationic and anionic highest occupied fragment orbitals (HOFOs), which we use to identify the highest occupied molecular orbital (HOMO). The anion gave rise to the HOMO for 25 of the 37 ILs studied here. For 10 of the ILs, the energies of the cationic and anionic HOFOs were the same (within experimental error); therefore, it could not be determined whether the HOMO was from the cation or the anion. For two of the ILs, the HOMO was from the cation and not from the anion; consequently it is energetically more favourable to remove an electron from the cation than the anion for these two ILs. In addition, we used a combination of area normalisation and subtraction of XP spectra to produce what are effectively XP spectra for individual ions; this was achieved for 10 cations and 14 anions.</p>}},
  author       = {{Fogarty, Richard M. and Palgrave, Robert G. and Bourne, Richard A. and Handrup, Karsten and Villar-Garcia, Ignacio J. and Payne, David J. and Hunt, Patricia A. and Lovelock, Kevin R.J.}},
  issn         = {{1463-9076}},
  language     = {{eng}},
  number       = {{35}},
  pages        = {{18893--18910}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Physical Chemistry Chemical Physics}},
  title        = {{Electron spectroscopy of ionic liquids : Experimental identification of atomic orbital contributions to valence electronic structure}},
  url          = {{http://dx.doi.org/10.1039/c9cp02200g}},
  doi          = {{10.1039/c9cp02200g}},
  volume       = {{21}},
  year         = {{2019}},
}