Adsorption and reaction of sub-monolayer films of an ionic liquid on Cu(111)

Uhl, Benedikt; Büchner, Florian; Gabler, Stephan; Bozorgchenani, Maral; Behm, R. Jürgen

doi:10.1039/c4cc03203a

Cited by 49 publications

(83 citation statements)

References 17 publications

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“…Many established UHV-based surface science techniques have successfully contributed to an increasingly detailed understanding not only of the IL/ vacuum interface, but also of IL bulk properties. The applied methods include X-ray photoelectron spectroscopy (XPS) [106,107,, UV photoelectron spectroscopy [138,139,165,166], inverse photoelectron spectroscopy (IPES) [165,166], X-ray absorption spectroscopy (NEXAFS) [165], soft X-ray emission spectroscopy (SXES) [166], low energy ion scattering (LEIS) [141], metastable ion spectroscopy (MIES) [138,139], time-offlight secondary mass spectroscopy (TOF-SIMS) [140], Rutherford backscattering [167][168][169][170][171], high resolution electron energy loss spectroscopy (HREELS) [138], reflection absorption infrared spectroscopy (RAIRS) [172][173][174][175], direct recoil spectroscopy (DRS) [176], and scanning tunneling microscopy [177][178][179][180][181], to name only a few. In addition, an increasing number of theoretical studies and simulations have been conducted [101,[182][183][184][185][186][187][188][189][190].…”

Section: Molecular Insights Into Il/gas and Il/support Interfacesmentioning

confidence: 99%

Ionic Liquids in Catalysis

2014

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Ionic liquids (ILs), salts with melting points below 100°C, represent a fascinating class of liquid materials typically characterized by an extremely low vapor pressure. Besides their application as new solvents or as electrolytes for electrochemical purposes, there are two important concepts of using ILs in catalysis: Liquid-liquid biphasic catalysis and IL thin film catalysis. Liquid-liquid biphasic catalysis enables either a very efficient manner to apply catalytic ILs, e.g. in Friedel-Crafts reactions, or to apply ionic transition metal catalyst solutions. In both cases, phase separation after reaction allows an easy separation of reaction products and catalyst re-use. One problem of liquidliquid biphasic catalysis is mass transfer limitation. If the chemical reaction is much faster than the liquid-liquid mass transfer the latter limits the overall reaction rate. This problem is overcome in IL thin film catalysis where diffusion pathways and thus the characteristic time of diffusion are short. Here, Supported Ionic Liquid Phase (SILP) and Solid Catalyst with Ionic Liquid Layer (SCILL) are the two most important concepts. In both, a high surface area solid substrate is covered with a thin IL film, which contains either a homogeneously dissolved transition metal complex for SILP, or which modifies catalytically active surface sites at the support for SCILL. In each concept, interface phenomena play a very important role: These may concern the interface of an IL phase with an organic phase in the case of liquidliquid biphasic catalysis. For IL thin film catalysis, the interfaces of the IL with the gas phase and with catalytic nanoparticles and/or support materials are of critical importance. It has recently been demonstrated that these interfaces and also the bulk of ILs can be investigated in great detail using surface science studies, which greatly contributed to the fundamental understanding of the catalytic properties of ILs and supported IL materials. Exemplary results concerning the IL/vacuum or IL/gas interface, the solubility and surface enrichment of dissolved metal complexes, the IL/support interface and the in situ monitoring of chemical reactions in ILs are presented.

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Section: Molecular Insights Into Il/gas and Il/support Interfacesmentioning

confidence: 99%

Ionic Liquids in Catalysis

2014

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“…Focussing on applications of ILs as solvent in electrochemistry, the potential dependent interaction of bulk ILs with a single crystal metal surface was investigated combining in situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV). [28][29][30][31][32] In that work it was possible to gain insight into the structure formation on a molecular scale, combining high resolution STM imaging and XPS, which in combination with density functional calculations allowed us 3 to derive detailed information on the nature and order of magnitude of substrate -adsorbate interactions and the interactions between adjacent adsorbed IL species (adsorbateadsorbate interactions). Due to their extremely low vapour pressure, even thicker IL films can be investigated this way.…”

Section: Introductionmentioning

confidence: 99%

Interaction of ionic liquids with noble metal surfaces: structure formation and stability of [OMIM][TFSA] and [EMIM][TFSA] on Au(111) and Ag(111)

Uhl

Huang

Alwast

et al. 2015

Phys. Chem. Chem. Phys.

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102

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Aiming at a comprehensive understanding of the interaction of ionic liquids (ILs) with metal surfaces we have investigated the adsorption of two closely related ILs, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSA] and 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide [OMIM][TFSA], with two noble metal surfaces, Au(111) and Ag(111), under ultrahigh vacuum (UHV) conditions using scanning tunneling microscopy (STM). At room temperature, the ILs form a 2D liquid on either of the two surfaces, while at lower temperatures they condense into two-dimensional (2D) islands which exhibit ordered structures or a short-range ordered 2D glass structure. Comparison of the adlayer structures formed in the different adsorption systems and also with those determined recently for n-butyl-n-methylpyrrolidinium [TFSA](-) adlayers on Ag(111) and Au(111) (B. Uhl et al., Beilstein J. Nanotechnol., 2013, 4, 903) gains detailed insight into the adsorption geometry of the IL ions on the surface. The close similarity of the adlayer structures indicates that (i) the structure formation is dominated by the tendency to optimize the anion adsorption geometry, and that (ii) also in the present systems the cation adsorbs with the alkyl chain pointing up from the surface.

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“…Owing to its high decomposition temperature, very low vapor pressure, and a large stability window ranging from −2.5 to 3.0 V versus Ag/AgCl (about 0–5 V vs. Li/Li + ), [BMP][TFSI] is a very promising candidate for LIBs. Special interest was placed on the interactions at the substrate|IL interface under UHV conditions by using several model substrates, for example, single‐crystalline metal surfaces, oxide surfaces, and highly oriented pyrolytic graphite . The above studies, which were conducted in the absence of an applied potential and which focused on the structure formation and the decomposition of the ionic liquid, clearly demonstrated that the chemical interaction with the substrate surface and/or with the added lithium is sufficient to cause decomposition of the IL.…”

Section: Introductionmentioning

confidence: 99%