Surface Enrichment and Depletion Effects of Ions Dissolved in an Ionic Liquid: An X‐ray Photoelectron Spectroscopy Study

Maier, Florian; Gottfried, J. Michael; Rossa, Jürgen; Gerhard, Dirk; Schulz, Peter S.; Schwieger, Wilhelm; Wasserscheid, Peter; Steinrück, Hans‐Peter

doi:10.1002/anie.200602756

Cited by 119 publications

(133 citation statements)

References 24 publications

Supporting

Mentioning

124

Contrasting

Order By: Relevance

“…In a simplified picture, the same core level of a given atom exhibits a higher BE if it is positively charged compared to a more negatively charged one. However, up to now, most XPS studies of pure ILs have concentrated on the surface composition and molecular orientation of the ions, [38,39,41,43,[50][51][52] while few have addressed the electronic structure in terms of ion-ion interactions. [53] To provide a more detailed understanding of the specific interactions within imidazolium-based ILs, we present here a systematic XPS and NMR study in combination with theoretical calculations.…”

Section: Introductionmentioning

confidence: 99%

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Cremer

Kolbeck

Lovelock

et al. 2010

Chemistry A European J

Self Cite

279

335

View full text Add to dashboard Cite

Ten [C(8)C(1)Im](+) (1-methyl-3-octylimidazolium)-based ionic liquids with anions Cl(-), Br(-), I(-), [NO(3)](-), [BF(4)](-), [TfO](-), [PF(6)](-), [Tf(2)N](-), [Pf(2)N](-), and [FAP](-) (TfO=trifluoromethylsulfonate, Tf(2)N=bis(trifluoromethylsulfonyl)imide, Pf(2)N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C(8)C(1)C(1)Im](+) (1,2-dimethyl-3-octylimidazolium)-based ionic liquids with anions Br(-) and [Tf(2)N](-) were investigated by using X-ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While (1)H NMR spectroscopy is found to probe very specifically the strongest hydrogen-bond interaction between the hydrogen attached to the C(2) position and the anion, a comparative XPS study provides first direct experimental evidence for cation-anion charge-transfer phenomena in ionic liquids as a function of the ionic liquid's anion. These charge-transfer effects are found to be surprisingly similar for [C(8)C(1)Im](+) and [C(8)C(1)C(1)Im](+) salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions.

show abstract

Section: Introductionmentioning

confidence: 99%

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Cremer

Kolbeck

Lovelock

et al. 2010

Chemistry A European J

Self Cite

279

335

View full text Add to dashboard Cite

show abstract

“…Hence, our data provide an unambiguous proof for a surface enrichment of the Pt complex on expense of the IL cation. Since the atomic ratio N [ 51 ] ). It is interesting to note that until now only one transition metal complex with such a pronounced enrichment effect has been observed.…”

mentioning

confidence: 98%

“…Indeed, by ARXPS it could be demonstrated that a Pt catalyst, [Pt(NH 3 ) 4 ]Cl 2, with a nominal concentration below 0.1 mol-% in [C 2 C 1 Im][EtOSO 3 ] is indeed enriched in the surface region by a factor of 200! [ 51 ] The corresponding N 1s XP spectra are shown in Figure 6 a. For the pure IL, the two nearly equivalent imidazolium nitrogens lead to a single peak N Imid at 401.8 eV.…”

mentioning

confidence: 99%

Surface Science and Model Catalysis with Ionic Liquid‐Modified Materials

et al. 2011

View full text Add to dashboard Cite

Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy.

show abstract

“…31,47 First XPS work on ILs was performed in 2005 by the group of Peter Licence, 48 quickly followed by further XPS publications in 2006 by other groups, including that of the authors. [49][50][51][52][53] Since then, this new field of "Ionic Liquid Surface Science" has established itself as an important discipline in ongoing IL research and many surface science techniques have successfully contributed to an increasingly detailed understanding not only of the IL/vacuum interface but also of the IL/support interface of ultrathin IL layers and of IL bulk properties. 29 In these initial studies, [48][49][50][51][52][53] it was confirmed that vapor pressures of ILs are indeed sufficiently low to allow for the application of UHV conditions for a prolonged time without either damage to the IL or any severe impact onto the base pressure of the UHV chamber.…”

Section: Introductionmentioning

confidence: 99%

Perspective: Chemical reactions in ionic liquids monitored through the gas (vacuum)/liquid interface

Maier

Niedermaier

Steinrück

2017

The Journal of Chemical Physics

View full text Add to dashboard Cite

This perspective analyzes the potential of X-ray photoelectron spectroscopy under ultrahigh vacuum (UHV) conditions to follow chemical reactions in ionic liquids in situ. Traditionally, only reactions occurring on solid surfaces were investigated by X-ray photoelectron spectroscopy (XPS) in situ. This was due to the high vapor pressures of common liquids or solvents, which are not compatible with the required UHV conditions. It was only recently realized that the situation is very different when studying reactions in Ionic Liquids (ILs), which have an inherently low vapor pressure, and first studies have been performed within the last years. Compared to classical spectroscopy techniques used to monitor chemical reactions, the advantage of XPS is that through the analysis of their core levels all relevant elements can be quantified and their chemical state can be analyzed under well-defined (ultraclean) conditions. In this perspective, we cover six very different reactions which occur in the IL, with the IL, or at an IL/support interface, demonstrating the outstanding potential of in situ XPS to gain insights into liquid phase reactions in the near-surface region.

show abstract

Surface Enrichment and Depletion Effects of Ions Dissolved in an Ionic Liquid: An X‐ray Photoelectron Spectroscopy Study

Cited by 119 publications

References 24 publications

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Surface Science and Model Catalysis with Ionic Liquid‐Modified Materials

Perspective: Chemical reactions in ionic liquids monitored through the gas (vacuum)/liquid interface

Contact Info

Product

Resources

About