Surface Analysis of Ionic Liquids with and without Lithium Salt Using X-ray Photoelectron Spectroscopy

Abstract

X-ray photoelectron spectroscopy (XPS) was applied to a neat ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [EMI(+)][Tf(2)N(-)] and its lithium salt solution at room temperature to clarify the composition and structure of its near-surface region. Core level peaks were recorded for Li 1s, N 1s, C 1s, F 1s, O 1s, S 2s, and S 2p. Valence band XPS spectra (0-40 eV binding energy) were also studied. The XPS spectra were analyzed using DV-Xα calculations. Results show that the planar type isomer of the EMI(+) cation is dominant at the near-surface region of EMI-Tf(2)N. Results of XPS measurements show a spectrum of Li 1s in Li/EMI-Tf(2)N. The proposed models for the preferred orientation of the ions exhibit good agreement with results obtained from the DV-Xα calculations.

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

“…Ouchi and co-workers used a combination of SXES and calculations to conclude that the anion HOFO for both [TfO]and [NTf2]came from O 2p, 18,19 matching our conclusions here. Kurisaki and co-workers used a combination of valence XPS and calculations to conclude that the anion HOFO for [NTf2]came from O 2p, 74 matching our conclusions here. Beenken and co-workers used a combination of valence XPS, UPS and calculations to conclude that the anion HOFO for [NTf2]came mainly from oxygen, 38 matching our conclusions here.…”

Valence electronic structure of [EMIM][BF4] ionic liquid: photoemission and DFT+D study

“…This is true for most ionic liquids. 8,17,23 It has been shown, that the spectral intensities can be described better, if the photoemission cross sections are taken into account. 8,17 This is also conrmed by our calculation (see Fig.…”

Application of pyroelectric crystal and ionic liquid to the production of metal compounds

“…The position of N 1s, C 1s, and S 2p peaks related to EMI-Tf 2 N were coincident with reported values. [10][11][12][13] This result indicates that ions such as Zn 2+ , EMI + , and Tf 2 Nwere field-emitted from EMI-Tf 2 N containing zinc ions or that EMI-Tf 2 N containing zinc ions was evaporated on the silicon substrate. F 1s peak of 684.7 eV was additionally detected on the silicon substrate after applying electric field to EMI-Tf 2 N containing zinc ions as shown in Fig.…”