Time-dependent changes in the growth of ultrathin ionic liquid films on Ag(111)

Lexow, Matthias; Talwar, Timo; Heller, Bettina S. J.; May, B. D.; Bhuin, Radha Gobinda; Maier, Florian; Steinrück, Hans‐Peter

doi:10.1039/c8cp01411f

Cited by 31 publications

(139 citation statements)

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“…As a first step, an equivalent of 0.5 ML [C 8 C 1 Im][Tf 2 N] was deposited (Figure ‐II). It was shown previously that this amount forms a homogeneous wetting layer (WL) on Ag(111), with the IL ions arranged in a so‐called checkerboard arrangement . In this layer, the anions are adsorbed in a cis ‐conformation, with the CF 3 groups preferentially pointing towards the vacuum, as depicted schematically in Figure ‐II.…”

Section: Figurementioning

confidence: 92%

“…The accessible coverages range from sub‐monolayers to several multilayers . In previous model studies, the properties of the liquid/solid interface of ultrathin IL films were found to depend on the structure of the IL, the nature of the solid, and temperature ,,…”

Section: Figurementioning

confidence: 99%

“…In these examples, the liquid/solid interface determines the function, performance and stability of the respective system. Therefore, and also from a fundamental interest in the structure and formation of liquid/solid interfaces, the adsorption and wetting properties of ILs on solid surfaces are studied on the molecular,, mesoscopic and macroscopic scale . Only detailed knowledge of the interface properties allows for tailoring systems for specific applications.…”

Section: Figurementioning

confidence: 99%

“…The two investigated ILs are 1‐methyl‐3‐octyl imidazolium bis[(trifluoromethyl)sulfonyl]imide, [C 8 C 1 Im][Tf 2 N], and 1‐methyl‐3‐octyl imidazolium hexafluorophosphate, [C 8 C 1 Im][PF 6 ]. While the former has been studied as neat IL on Ag(111) before,, making this system an excellent reference system, the latter is so far unexplored in this context. The different chemical environments in the two anions (top of Figure ) yield distinct chemical shifts of the respective F 1s binding energies in XPS.…”

Section: Figurementioning

confidence: 99%

“…IL coverages are given in ML, where 1 ML is defined as a closed double layer of ions irrespective of their relative arrangement ,. Based on the ILs’ molecular volume

V_{m}

, the height

h

of 1 ML was estimated to be 0.77 nm for [C 8 C 1 Im][PF 6 ] and 0.84 nm for [C 8 C 1 Im][Tf 2 N], using values for

V_{m}

from literature ,,…”

Section: Figurementioning

confidence: 99%

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Anion Exchange at the Liquid/Solid Interface of Ultrathin Ionic Liquid Films on Ag(111)

et al. 2018

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Thin ionic liquid (IL) films play an important role in many applications. To obtain a better understanding of the ion distribution within IL mixture films, we sequentially deposited ultrathin layers of two ILs with the same cation but different anions onto Ag(111), and monitored their dynamic behaviour by angle‐resolved X‐ray photoelectron spectroscopy. Upon depositing [C8C1Im][PF6] on top of a wetting layer of [C8C1Im][Tf2N] at room temperature (RT), we found a pronounced enrichment of the [Tf2N]− anions at the IL/vacuum interface, due to a rapid anion exchange at the IL/solid interface. In contrast, at 90 K, the [Tf2N]− anions remain at the IL/solid interface. Upon heating, we observe a rearrangement of the cations between 140 and 160 K, such that the octyl chains preferentially point towards the vacuum. Above 170 K, the ions start to become mobile, and at 220 K, the anion exchange is completed, with the [Tf2N]− anions enriched at the IL/vacuum interface in the same way as found for deposition at RT. The temperature range for the anion exchange corresponds well to glass transition temperatures reported in literature. We propose two driving forces to be cooperatively responsible for the replacement/exchange of [Tf2N]− at the IL/solid interface and its enrichment at the IL/vacuum interface. First, the adsorption energy of [C8C1Im][PF6] is significantly larger than that of [C8C1Im][Tf2N], and second, the surface tension of [C8C1Im][Tf2N] is lower than that of [C8C1Im][PF6].

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Section: Figurementioning

confidence: 92%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

“…IL coverages are given in ML, where 1 ML is defined as a closed double layer of ions irrespective of their relative arrangement ,. Based on the ILs’ molecular volume

V_{m}

, the height

h

of 1 ML was estimated to be 0.77 nm for [C 8 C 1 Im][PF 6 ] and 0.84 nm for [C 8 C 1 Im][Tf 2 N], using values for

V_{m}

from literature ,,…”

Section: Figurementioning

confidence: 99%

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Anion Exchange at the Liquid/Solid Interface of Ultrathin Ionic Liquid Films on Ag(111)

et al. 2018

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Emerging Applications of Solid Catalysts with Ionic Liquid Layer Concept in Electrocatalysis

Zhang

Etzold

2021

Adv Funct Materials

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The concept of solid catalysts with ionic liquid layer (SCILL) originates from the field of heterogeneous catalysis, where it offers a unique way to regulate both the catalytic activity and selectivity. In recent years, applying this concept in electrocatalysis represented a new, exciting, and growing research field. Herein, emerging applications of the SCILL concept in the context of electrocatalysis for key energy storage/conversion processes such as oxygen reduction, oxygen evolution, and CO2 reduction reactions are comprehensively reviewed. Alongside case studies highlighting the history, development and latest progress of the SCILL concept, mechanistic underpinnings on the roles of ILs in each application are critically discussed. At the same time, the key challenges and future opportunities in fully leveraging the SCILL concept for either regulating the performance of electrocatalysts or gaining mechanistic understandings for those electrocatalytic processes with complex reaction pathways are outlined.

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On‐Surface Metathesis of an Ionic Liquid on Ag(111)

Massicot

Sasaki

Lexow

et al. 2022

Chemistry A European J

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We investigated the adsorption, surface enrichment, ion exchange, and on-surface metathesis of ultrathin mixed IL films on Ag(111). We stepwise deposited 0.5 ML of the protic IL diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]) and 1.0 ML of the aprotic IL 1-methyl-3-octylimidazolium hexafluorophosphate ([C 8 C 1 Im][PF 6 ]) at around 90 K. Thereafter, the resulting layered frozen film was heated to 550 K, and the thermally induced phenomena were monitored in situ by angle-resolved X-ray photoelectron spectroscopy. Between 135 and 200 K, [TfO] À anions at the Ag(111) surface are exchanged by [PF 6 ] À anions and enriched together with [C 8 C 1 Im] + cations at the IL/vacuum interface. Upon further heating, [dema][PF 6 ] and [OMIm][PF 6 ] desorb selectively at ~235 and ~380 K, respectively. Hereby, a wetting layer of pure [C 8 C 1 Im][TfO] is formed by on-surface metathesis at the IL/metal interface, which completely desorbs at ~480 K. For comparison, ion enrichment at the vacuum/IL interface was also studied in macroscopic IL mixtures, where no influence of the solid support is expected.

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Time-dependent changes in the growth of ultrathin ionic liquid films on Ag(111)

Abstract: Time dependent changes of IL film morphology depend on their molecular structure.

Cited by 31 publications

References 38 publications

Anion Exchange at the Liquid/Solid Interface of Ultrathin Ionic Liquid Films on Ag(111)

Anion Exchange at the Liquid/Solid Interface of Ultrathin Ionic Liquid Films on Ag(111)

Emerging Applications of Solid Catalysts with Ionic Liquid Layer Concept in Electrocatalysis

On‐Surface Metathesis of an Ionic Liquid on Ag(111)

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