1
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Wang J, Li H, Warr GG, Chen F, Atkin R. Nanostructure and Dynamics of Aprotic Ionic Liquids at Graphite Electrodes as a Function of Potential. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2311353. [PMID: 38573945 DOI: 10.1002/smll.202311353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 03/05/2024] [Indexed: 04/06/2024]
Abstract
Atomic force microscope (AFM) videos reveal the near-surface nanostructure and dynamics of the ionic liquids (ILs) 1-butyl-3-methylimidazolium dicyanamide (BMIM DCA) and 1-hexyl-3-methylimidazolium dicyanamide (HMIM DCA) above highly oriented pyrolytic graphite (HOPG) electrodes as a function of surface potential. Molecular dynamics (MD) simulations reveal the molecular-level composition of the nanostructures. In combination, AFM and MD show that the near-surface aggregates form via solvophobic association of the cation alkyl chains at the electrode interface. The diffusion coefficients of interfacial nanostructures are ≈0.01 nm2 s-1 and vary with the cation alkyl chain length and the surface potential. For each IL, the nanostructure diffusion coefficients are similar at open-circuit potential (OCP) and OCP + 1V, but BMIM DCA moves about twice as fast as HMIM DCA. At negative potentials, the diffusion coefficient decreases for BMIM DCA and increases for HMIM DCA. When the surface potential is switched from negative to positive, a sudden change in the direction of the nanostructure motion is observed for both BMIM DCA and HMIM DCA. No transient dynamics are noted following other potential jumps. This study provides a new fundamental understanding regarding the dynamics of electrochemically stable ILs at electrodes vital for the rational development of IL-based electrochemical devices.
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Affiliation(s)
- Jianan Wang
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Hwy, Perth, WA, 6009, Australia
| | - Hua Li
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Hwy, Perth, WA, 6009, Australia
- Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, 35 Stirling Hwy, Perth, WA, 6009, Australia
| | - Gregory G Warr
- School of Chemistry and Sydney Nano Institute, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Fangfang Chen
- Institute for Frontier Materials (IFM), Deakin University, Waurn Ponds, Geelong, VIC, 3216, Australia
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Hwy, Perth, WA, 6009, Australia
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2
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Park S, McDaniel JG. Generalized Helmholtz model describes capacitance profiles of ionic liquids and concentrated aqueous electrolytes. J Chem Phys 2024; 160:164709. [PMID: 38651812 DOI: 10.1063/5.0194360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Accepted: 03/21/2024] [Indexed: 04/25/2024] Open
Abstract
In this work, we propose and validate a generalization of the Helmholtz model that can account for both "bell-shaped" and "camel-shaped" differential capacitance profiles of concentrated electrolytes, the latter being characteristic of ionic liquids. The generalization is based on introducing voltage dependence of both the dielectric constant "ϵr(V)" and thickness "L(V)" of the inner Helmholtz layer, as validated by molecular dynamics (MD) simulations. We utilize MD simulations to study the capacitance profiles of three different electrochemical interfaces: (1) graphite/[BMIm+][BF4-] ionic liquid interface; (2) Au(100)/[BMIm+][BF4-] ionic liquid interface; (3) Au(100)/1M [Na+][Cl-] aqueous interface. We compute the voltage dependence of ϵr(V) and L(V) and demonstrate that the generalized Helmholtz model qualitatively describes both camel-shaped and bell-shaped differential capacitance profiles of ionic liquids and concentrated aqueous electrolytes (in lieu of specific ion adsorption). In particular, the camel-shaped capacitance profile that is characteristic of ionic liquid electrolytes arises simply from combination of the voltage-dependent trends of ϵr(V) and L(V). Furthermore, explicit analysis of the inner layer charge density for both concentrated aqueous and ionic liquid double layers reveal similarities, with these charge distributions typically exhibiting a dipolar region closest to the electrode followed by a monopolar peak at larger distances. It is appealing that a generalized Helmholtz model can provide a unified description of the inner layer structure and capacitance profile for seemingly disparate aqueous and ionic liquid electrolytes.
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Affiliation(s)
- Suehyun Park
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
| | - Jesse G McDaniel
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
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3
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Bühlmeyer H, Talwar T, Eschenbacher R, Barreto J, Hauner J, Knörr L, Steinrück HP, Maier F, Libuda J. Surface Chemistry of a [C 2C 1Im][OTf] (Sub)Wetting Layer on Pt(111): A Combined XPS, IRAS, and STM Study. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 38652177 DOI: 10.1021/acsami.4c02239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
The concept of a solid catalyst with an ionic liquid layer (SCILL) is a promising approach to improve the selectivity of noble metal catalysts in heterogeneous reactions. In order to understand the origins of this selectivity control, we investigated the growth and thermal stability of ultrathin 1-ethyl-3-methylimidazolium trifluormethanesulfonate [C2C1Im][OTf] films on Pt(111) by infrared reflection absorption spectroscopy (IRAS) and X-ray photoelectron spectroscopy (XPS) in time-resolved and temperature-programmed experiments. We combined these spectroscopy experiments with scanning tunneling microscopy (STM) to obtain detailed insights into the orientation and adsorption geometry of the ions in the first IL layer. Furthermore, we propose a mechanism for the thermal evolution of [C2C1Im][OTf] on Pt(111). We observe an intact IL layer on the surface at temperatures below 200 K. Adsorbed [C2C1Im][OTf] forms islands, which are evenly distributed over the surface. The [OTf]- anion adsorbs via the SO3 group, with the molecular axis perpendicular to the surface. Anions and cations are arranged next to each other, alternating on the Pt(111) surface. Upon heating to 250 K, we observe changes in geometry and structural distribution. Whereas at low temperature, the ions are arranged alternately for electrostatic reasons, this driving force is no longer decisive at 250 K. Here, a phase separation of two different species is discernible in STM. We propose that this effect is due to a surface reaction, which changes the charge of the adsorbates. We assume that the IL starts to decompose at around 250 K, and thus, pristine IL and decomposition products coexist on the surface. Also, IRAS and XPS show indication of IL decomposition. Further heating leads to increased IL decomposition. The reaction products associated with the anions are volatile and leave the surface. In contrast, the cation fragments remain on the surface up to temperatures above 420 K.
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Affiliation(s)
- Hanna Bühlmeyer
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Timo Talwar
- Chair of Physical Chemistry II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Roman Eschenbacher
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Jade Barreto
- Chair of Physical Chemistry II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Jonas Hauner
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Lukas Knörr
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Hans-Peter Steinrück
- Chair of Physical Chemistry II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Florian Maier
- Chair of Physical Chemistry II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Jörg Libuda
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
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4
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Avirdi E, Paumo HK, Kamdem BP, Singh MB, Kumari K, Katata-Seru L, Bahadur I. Imidazolium-Based Ionic Liquid-Assisted Silver Nanoparticles and Their Antibacterial Activity: Experimental and Density Functional Theory Studies. ACS OMEGA 2023; 8:42976-42986. [PMID: 38024669 PMCID: PMC10652719 DOI: 10.1021/acsomega.3c06171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Accepted: 09/13/2023] [Indexed: 12/01/2023]
Abstract
The exclusive properties of ionic liquids (ILs) offer various opportunities to develop advanced materials with appreciable therapeutic applications. Imidazolium-based ILs have been frequently used as reaction media and stabilizers for the development and surface functionalization of noble metal nanoparticles (NPs). This study reports the citrate-mediated reduction of silver ions in three different ILs, that is, 1-ethyl-3-methylimidazolium methyl sulfate ([EMIM][MS]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][OTf]), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]). The resulting Ag-ILs NPs were characterized using many analytical techniques, including UV-visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction (XRD). DLS and XRD characterization revealed the negatively charged Ag-[EMIM][MS] NPs, Ag-[BMIM][OTf] NPs, and Ag-[BMIM][TFSI] NPs with mean hydrodynamic sizes of 278, 316, and 279 nm, respectively, and a face-centered cubic structure. These hybrid nanomaterials were subjected to in vitro antibacterial screening against three bacterial strains. The Ag-[BMIM][OTf] NPs exhibited significant activities against Escherichia coli, Staphylococcus aureus, and Enterobacter cloacae. The lowest inhibition concentration of 62.5 μg/mL was recorded against E. coli using Ag-[EMIM][MS] and Ag-[BMIM][OTf] NPs. Further, the density functional theory calculations carried out on the computed Ag-ILs in the gas phase and water showed relatively stable systems. Ag-[BMIM][TFSI] exhibited the lowest Gibbs free energy change of -34.41 kcal/mol. The value of the global electrophilicity index (ω = 0.1865 eV) for the Ag-[BMIM][OTf] correlated with its good antibacterial activity.
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Affiliation(s)
- Elham Avirdi
- Department
of Chemistry, Material Science Innovation & Modelling (MaSIM)
Research Focus Area, North-West University, Private Bag X2046, Mmabatho 2735, South Africa
| | - Hugues Kamdem Paumo
- Department
of Chemistry, Material Science Innovation & Modelling (MaSIM)
Research Focus Area, North-West University, Private Bag X2046, Mmabatho 2735, South Africa
| | - Boniface Pone Kamdem
- Laboratory
for Phytobiochemistry and Medicinal Plants Study, Department of Biochemistry,
Faculty of Science, University of Yaoundé
1, P.O. Box 812, Yaoundé 05508-000, Cameroon
| | - Madhur Babu Singh
- Department
of Chemistry, Atma Ram Sanatan Dharma College,
University of Delhi, New Delhi 110021, India
| | - Kamlesh Kumari
- Department
of Zoology, University of Delhi, Delhi 110007, India
| | - Lebogang Katata-Seru
- Department
of Chemistry, Material Science Innovation & Modelling (MaSIM)
Research Focus Area, North-West University, Private Bag X2046, Mmabatho 2735, South Africa
| | - Indra Bahadur
- Department
of Chemistry, Material Science Innovation & Modelling (MaSIM)
Research Focus Area, North-West University, Private Bag X2046, Mmabatho 2735, South Africa
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5
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Massicot S, Gezmis A, Talwar T, Meusel M, Jaekel S, Adhikari R, Winter L, Fernández CC, Bayer A, Maier F, Steinrück HP. Adsorption and thermal evolution of [C 1C 1Im][Tf 2N] on Pt(111). Phys Chem Chem Phys 2023; 25:27953-27966. [PMID: 37655794 DOI: 10.1039/d3cp02743k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
In the context of ionic liquid (IL)-assisted catalysis, we have investigated the adsorption and thermal evolution of the IL 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([C1C1Im][Tf2N]) on Pt(111) between 100 and 800 K by angle-resolved X-ray photoelectron spectroscopy and scanning tunneling microscopy. Defined amounts of IL in the coverage range of a complete first wetting layer were deposited at low temperature (100-200 K), and subsequently heated to 300 K, or directly at 300 K. At 100 K, the IL adsorbs as an intact disordered layer. Upon heating to 200 K, the IL stays intact, but forms an ordered and well-oriented structure. Upon heating to 250 K, the surface order increases, but at the same time STM and XPS indicate the onset of decomposition. Upon heating to 300 K, decomposition progresses, such that 50-60% of the IL is decomposed. The anion-related reaction products desorb instantaneously, and the cation-related products remain on the surface. Thereby, the surface is partly passivated, enabling the remaining IL to still be adsorbed intact at 300 K. For IL deposition directly at 300 K, a fraction of the IL instantaneously decomposes, with the anion-related products desorbing, opening free space for further deposition of IL. Hence, cation-related species accumulate at the expense of anions, until one fully closed wetting layer is formed. As a consequence, a higher dose is required to reach this coverage at 300 K, compared to 100-200 K.
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Affiliation(s)
- Stephen Massicot
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Afra Gezmis
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Timo Talwar
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Manuel Meusel
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Simon Jaekel
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Rajan Adhikari
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Leonhard Winter
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Cynthia C Fernández
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Andreas Bayer
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Florian Maier
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
| | - Hans-Peter Steinrück
- Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany.
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6
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Bühlmeyer H, Hauner J, Eschenbacher R, Steffen J, Trzeciak S, Taccardi N, Görling A, Zahn D, Wasserscheid P, Libuda J. Structure Formation in an Ionic Liquid Wetting Layer: A Combined STM, IRAS, DFT and MD Study of [C 2 C 1 Im][OTf] on Au(111). Chemistry 2023; 29:e202301328. [PMID: 37277680 DOI: 10.1002/chem.202301328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 06/02/2023] [Accepted: 06/05/2023] [Indexed: 06/07/2023]
Abstract
In a solid catalyst with ionic liquid layer (SCILL), ionic liquid (IL) coatings are used to improve the selectivity of noble metal catalysts. To understand the origins of this selectivity control, we performed model studies by surface science methods in ultrahigh vacuum (UHV). We investigated the growth and thermal stability of ultrathin IL films by infrared reflection absorption spectroscopy (IRAS). We combined these experiments with scanning tunneling microscopy (STM) to obtain information on the orientation of the ions, the interactions with the surface, the intermolecular interactions, and the structure formation. Additionally, we performed DFT calculations and molecular dynamics (MD) simulations to interpret the experimental data. We studied the IL 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [C2 C1 Im][OTf] on Au(111) surfaces. We observe a weakly bound multilayer of [C2 C1 Im][OTf], which is stable up to 390 K, while the monolayer desorbs at ∼450 K. [C2 C1 Im][OTf] preferentially adsorbs at the step edges and elbows of the herringbone reconstruction of Au(111). The anion adsorbs via the SO3 group with the molecular axis perpendicular to the surface. At low coverage, the [C2 C1 Im][OTf] crystallizes in a glass-like 2D phase with short-range order. At higher coverage, we observe a phase transition to a 6-membered ring structure with long-range order.
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Affiliation(s)
- Hanna Bühlmeyer
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
| | - Jonas Hauner
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
| | - Roman Eschenbacher
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
| | - Julien Steffen
- Chair of Theoretical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
| | - Simon Trzeciak
- Computer Chemistry Center, CCC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße 25, 91052, Erlangen, Germany
| | - Nicola Taccardi
- Chair of Chemical Engineering I, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
| | - Andreas Görling
- Chair of Theoretical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
| | - Dirk Zahn
- Chair of Theoretical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
- Computer Chemistry Center, CCC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße 25, 91052, Erlangen, Germany
| | - Peter Wasserscheid
- Chair of Chemical Engineering I, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
| | - Jörg Libuda
- Interface Research and Catalysis, ECRC, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
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7
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Nucleation, Coalescence, and Thin-Film Growth of Triflate-Based Ionic Liquids on ITO, Ag, and Au Surfaces. COLLOIDS AND INTERFACES 2022. [DOI: 10.3390/colloids6030046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study investigates the nucleation and growth of micro-/nanodroplets of triflate-based ionic liquids (ILs) fabricated by vapor deposition on different surfaces: indium tin oxide (ITO); silver (Ag); gold (Au). The ILs studied are constituted by the alkylimidazolium cation and the triflate anion—[CnC1im][OTF] series. One of the key issues that determine the potential applications of ILs is the wettability of surfaces. Herein, the wetting behavior was evaluated by changing the cation alkyl chain length (C2 to C10). A reproducible control of the deposition rate was conducted employing Knudsen cells, and the thin-film morphology was evaluated by high-resolution scanning electron microscopy (SEM). The study reported here for the [CnC1im][OTF] series agrees with recent data for the [CnC1im][NTf2] congeners, highlighting the higher wettability of the solid substrates to long-chain alkylimidazolium cations. Compared to [NTf2], the [OTF] series evidenced an even more pronounced wetting ability on Au and coalescence processes of droplets highly intense on ITO. Higher homogeneity and film cohesion were found for cationic groups associated with larger alkyl side chains. An island growth was observed on both Ag and ITO substrates independently of the cation alkyl chain length. The Ag surface promoted the formation of smaller-size droplets. A quantitative analysis of the number of microdroplets formed on Ag and ITO revealed a trend shift around [C6C1im][OTF], emphasizing the effect of the nanostructuration intensification due to the formation of nonpolar continuous domains.
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8
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Costa JCS, Alves A, Bastos M, Santos LMNBF. The impact of the cation alkyl chain length on the wettability of alkylimidazolium-based ionic liquids at the nanoscale. Phys Chem Chem Phys 2022; 24:13343-13355. [PMID: 35608141 DOI: 10.1039/d2cp01868c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ionic liquids (ILs) have been widely used for energy storage and conversion devices due to their negligible vapor pressure, high thermal stability, and outstanding interfacial properties. Notably, the interfacial nanostructure and the wettability of thin ionic liquid films on solid surfaces are of utmost relevance in nanosurface science and technology. Herein, a reproducible physical vapor deposition methodology was used to fabricate thin films of four alkylimidazolium bis(trifluoromethylsulfonyl)imide ILs. The effect of the cation alkyl chain length on the wettability of ILs was explored on different surfaces: gold (Au); silver (Ag); indium-tin oxide (ITO). High-resolution scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to evaluate the morphology of the produced micro- and nanodroplets and films. SEM and AFM results revealed an island growth for all the ILs deposited on ITO and Ag surfaces, with a lower minimum free area to promote nucleation (MFAN) in Ag and higher wettability for ILs having larger non-polar domains. The low wettability of ITO by the studied ILs was highlighted. For long-chain ILs, nucleation and growth mechanisms were strongly conditioned by coalescence processes. The results also supported the higher affinity of the ILs to the Au surface. The increase in the length of the cation alkyl chain was found to promote a better film adhesion inducing a 2D growth and higher wetting ability.
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Affiliation(s)
- José C S Costa
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, P4169-007, Porto, Portugal.
| | - Alexandre Alves
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, P4169-007, Porto, Portugal.
| | - Margarida Bastos
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, P4169-007, Porto, Portugal.
| | - Luís M N B F Santos
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, P4169-007, Porto, Portugal.
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9
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Massicot S, Sasaki T, Lexow M, Maier F, Kuwabata S, Steinrück H. On‐Surface Metathesis of an Ionic Liquid on Ag(111). Chemistry 2022; 28:e202200167. [PMID: 35363397 PMCID: PMC9321566 DOI: 10.1002/chem.202200167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Indexed: 11/17/2022]
Abstract
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 ([C8C1Im][PF6]) 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]− anions at the Ag(111) surface are exchanged by [PF6]− anions and enriched together with [C8C1Im]+ cations at the IL/vacuum interface. Upon further heating, [dema][PF6] and [OMIm][PF6] desorb selectively at ∼235 and ∼380 K, respectively. Hereby, a wetting layer of pure [C8C1Im][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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Affiliation(s)
- Stephen Massicot
- Lehrstuhl für Physikalische Chemie II Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 3 91058 Erlangen Germany
| | - Tomoya Sasaki
- Department of Applied Chemistry Graduate School of Engineering Osaka University Yamada-oka 2–1, Suita Osaka 565-0871 Japan
| | - Matthias Lexow
- Lehrstuhl für Physikalische Chemie II Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 3 91058 Erlangen Germany
| | - Florian Maier
- Lehrstuhl für Physikalische Chemie II Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 3 91058 Erlangen Germany
| | - Susumu Kuwabata
- Department of Applied Chemistry Graduate School of Engineering Osaka University Yamada-oka 2–1, Suita Osaka 565-0871 Japan
| | - Hans‐Peter Steinrück
- Lehrstuhl für Physikalische Chemie II Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 3 91058 Erlangen Germany
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10
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Wang Y, He H, Wang C, Lu Y, Dong K, Huo F, Zhang S. Insights into Ionic Liquids: From Z-Bonds to Quasi-Liquids. JACS AU 2022; 2:543-561. [PMID: 35373210 PMCID: PMC8965826 DOI: 10.1021/jacsau.1c00538] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Indexed: 05/26/2023]
Abstract
Ionic liquids (ILs) hold great promise in the fields of green chemistry, environmental science, and sustainable technology due to their unique properties, such as a tailorable structure, the various types available, and their environmentally friendly features. On the basis of multiscale simulations and experimental characterizations, two unique features of ILs are as follows: (1) strong coupling interactions between the electrostatic forces and hydrogen bonds, namely in the Z-bond, and (2) the unique semiordered structure and properties of ultrathin films, specifically regarding the quasi-liquid. In accordance with the aforementioned theoretical findings, many cutting-edge applications have been proposed: for example, CO2 capture and conversion, biomass conversion and utilization, and energy storage materials. Although substantial progress has been made recently in the field of ILs, considerable challenges remain in understanding the nature of and devising applications for ILs, especially in terms of e.g. in situ/real-time observation and highly precise multiscale simulations of the Z-bond and quasi-liquid. In this Perspective, we review recent developments and challenges for the IL research community and provide insights into the nature and function of ILs, which will facilitate future applications.
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Affiliation(s)
- Yanlei Wang
- Beijing
Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory
of Multiphase Complex Systems, CAS Key Laboratory of Green Process
and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
- University
of Chinese Academy of Sciences, Beijing 100049, People’s
Republic of China
| | - Hongyan He
- Beijing
Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory
of Multiphase Complex Systems, CAS Key Laboratory of Green Process
and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
- University
of Chinese Academy of Sciences, Beijing 100049, People’s
Republic of China
| | - Chenlu Wang
- Beijing
Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory
of Multiphase Complex Systems, CAS Key Laboratory of Green Process
and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
- University
of Chinese Academy of Sciences, Beijing 100049, People’s
Republic of China
| | - Yumiao Lu
- Beijing
Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory
of Multiphase Complex Systems, CAS Key Laboratory of Green Process
and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
| | - Kun Dong
- Beijing
Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory
of Multiphase Complex Systems, CAS Key Laboratory of Green Process
and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
| | - Feng Huo
- Beijing
Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory
of Multiphase Complex Systems, CAS Key Laboratory of Green Process
and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
| | - Suojiang Zhang
- Beijing
Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory
of Multiphase Complex Systems, CAS Key Laboratory of Green Process
and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
- University
of Chinese Academy of Sciences, Beijing 100049, People’s
Republic of China
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11
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Wang C, Wang Y, Gan Z, Lu Y, Qian C, Huo F, He H, Zhang S. Topological engineering of two-dimensional ionic liquid islands for high structural stability and CO 2 adsorption selectivity. Chem Sci 2021; 12:15503-15510. [PMID: 35003578 PMCID: PMC8654070 DOI: 10.1039/d1sc05431g] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 10/29/2021] [Indexed: 11/21/2022] Open
Abstract
Ionic liquids (ILs) as green solvents and catalysts are highly attractive in the field of chemistry and chemical engineering. Their interfacial assembly structure and function are still far less well understood. Herein, we use coupling first-principles and molecular dynamics simulations to resolve the structure, properties, and function of ILs deposited on the graphite surface. Four different subunits driven by hydrogen bonds are identified first, and can assemble into close-packed and sparsely arranged annular 2D IL islands (2DIIs). Meanwhile, we found that the formation energy and HOMO–LUMO gap decrease exponentially as the island size increases via simulating a series of 2DIIs with different topological features. However, once the size is beyond the critical value, both the structural stability and electrical structure converge. Furthermore, the island edges are found to be dominant adsorption sites for CO2 and better than other pure metal surfaces, showing an ultrahigh adsorption selectivity (up to 99.7%) for CO2 compared with CH4, CO, or N2. Such quantitative structure–function relations of 2DIIs are meaningful for engineering ILs to efficiently promote their applications, such as the capture and conversion of CO2. Multi-scale simulations reveal the structure and properties of the two-dimensional ionic liquid islands supported by graphite, and the island edges show an ultrahigh adsorption selectivity for CO2 compared with CH4, CO, or N2.![]()
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Affiliation(s)
- Chenlu Wang
- Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences Beijing 100190 China .,University of Chinese Academy of Sciences Beijing 100049 China
| | - Yanlei Wang
- Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences Beijing 100190 China .,University of Chinese Academy of Sciences Beijing 100049 China
| | - Zhongdong Gan
- Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences Beijing 100190 China
| | - Yumiao Lu
- Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences Beijing 100190 China
| | - Cheng Qian
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology Ulsan 44919 South Korea
| | - Feng Huo
- Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences Beijing 100190 China
| | - Hongyan He
- Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences Beijing 100190 China .,University of Chinese Academy of Sciences Beijing 100049 China.,Innovation Academy for Green Manufacture, Chinese Academy of Sciences Beijing 100190 China.,Dalian National Laboratory for Clean Energy Dalian 116023 Liaoning China
| | - Suojiang Zhang
- Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences Beijing 100190 China .,University of Chinese Academy of Sciences Beijing 100049 China
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12
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Hohner C, Fromm L, Schuschke C, Taccardi N, Xu T, Wasserscheid P, Görling A, Libuda J. Adsorption Motifs and Molecular Orientation at the Ionic Liquid/Noble Metal Interface: [C 2C 1Im][NTf 2] on Pt(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:12596-12607. [PMID: 34661413 DOI: 10.1021/acs.langmuir.1c01900] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In solid catalysts with ionic liquid layers (SCILLs), ionic liquid (IL) thin films are used to modify the activity and selectivity of catalytic materials. In this work, we investigated the adsorption behavior of the IL 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [C2C1Im][NTf2] on Pt(111) by combining experimental and theoretical studies. Under ultrahigh vacuum (UHV) conditions, the IL was deposited onto a Pt(111) single crystal surface by physical vapor deposition (PVD) at different surface temperatures (200, 300, and 400 K). The adsorption process was monitored by in situ infrared reflection absorption spectroscopy (IRAS). Complementary to the IRAS studies, we performed density functional theory (DFT) calculations and analyzed the adsorption motifs and orientation of the IL ions. In total, we calculated four different systems: (a) [C2C1Im]+ and [NTf2]- ions in the gas phase; [NTf2]- anions in (b) small (4 × 4) and (c) large (6 × 6) Pt(111) supercells; and (d) a complete ion pair of [C2C1Im][NTf2] in a (6 × 6) Pt(111) supercell. Based on DFT, we simulated IR spectra and compared them to the experimental data. Our results suggest that the binding motif and orientation of the IL is strongly dependent on the actual IL coverage. In the monolayer (ML), [NTf2]- interacts strongly with the metal surface and adopts a specific orientation in which it interacts with the Pt surface via the SO2 groups. Also the [C2C1Im]+ cations adopt a preferential orientation up to coverages of 1 ML. Upon transition to the multilayer region, the specific orientation of the ions is gradually lost.
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Affiliation(s)
- Chantal Hohner
- Interface Research and Catalysis, Erlangen Center for Interface Research and Catalysis, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Lukas Fromm
- Lehrstuhl für Theoretische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Christian Schuschke
- Interface Research and Catalysis, Erlangen Center for Interface Research and Catalysis, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Nicola Taccardi
- Lehrstuhl für Chemische Reaktionstechnik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Tao Xu
- Interface Research and Catalysis, Erlangen Center for Interface Research and Catalysis, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Peter Wasserscheid
- Lehrstuhl für Chemische Reaktionstechnik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Andreas Görling
- Lehrstuhl für Theoretische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Jörg Libuda
- Interface Research and Catalysis, Erlangen Center for Interface Research and Catalysis, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
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13
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Meusel M, Gezmis A, Jaekel S, Lexow M, Bayer A, Maier F, Steinrück HP. Time- and Temperature-Dependent Growth Behavior of Ionic Liquids on Au(111) Studied by Atomic Force Microscopy in Ultrahigh Vacuum. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:20439-20449. [PMID: 34594432 PMCID: PMC8474146 DOI: 10.1021/acs.jpcc.1c06613] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Indexed: 06/13/2023]
Abstract
We deposited defined amounts of [C1C1Im][Tf2N] on Au(111) at different temperatures and investigated the morphology and wetting behavior of the deposited films by atomic force microscopy. For multilayer coverages, we observe a drastically different growth behavior when comparing deposition at room temperature (RT) and deposition below 170 K followed by slow annealing to RT. Upon deposition at RT, we find the formation of 2-30 nm high and 50-500 nm wide metastable 3D droplets on top of a checkerboard-type wetting layer. These droplets spread out into stable 2D bilayers, on the time scale of hours and days. The same 2D bilayer structure is obtained after deposition below 170 K and slow annealing to RT. We present a statistical analysis on the time-dependent changes of the shape and volume of the 3D droplets and the 2D bilayers. We attribute the stabilization of the 2D bilayers on the wetting layer and on already formed bilayers to the high degree of order in these layers. Notably, the transformation process from the 3D droplets to 2D bilayer islands is accelerated by tip effects and also X-ray radiation.
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14
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Lu Y, Xu Y, Lu L, Xu Z, Liu H. Interfacial interactions and structures of protic ionic liquids on a graphite surface: A first-principles study and comparison with aprotic ionic liquids. Phys Chem Chem Phys 2021; 23:18338-18348. [PMID: 34612375 DOI: 10.1039/d1cp02100a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Protic ionic liquids (PILs) have currently been indicated as promising alternative electrolytes in electrical storage devices, such as lithium-ion batteries and supercapacitors. However, compared with the well-studied aprotic ionic liquids (AILs), the knowledge of the interface between PILs and electrode material surfaces is very rare to date. In this work, the adsorption behaviors of three groups of PILs, i.e. pyrrolidinium-based, imidazolium-based, and ammonium-based, on graphite was systematically investigated using first-principles calculations. The corresponding AILs were also taken into account for comparison. The adsorption mechanism of these ILs on the surface is controlled by the interplay of strong electrostatic interactions between adsorbed ions, weak vdW forces between ILs and substrate, and many aromatic interactions including π-π stacking and C-H/N-Hπ contacts. PILs do show quite different preferential interfacial interactions and structures on the graphite surface with respect to AILs, arising mainly from the anion-substrate interactions. Particularly, proton transfer takes place in the PILs consisting of the imidazolium/ammonium cation and the nitrate anion in the gas phase, but it tends to be attenuated or even disappears on graphite caused by interfacial interactions.
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Affiliation(s)
- Yunxiang Lu
- Key Laboratory for Advanced Materials, School of Chemistry & Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, China.
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15
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Elbourne A, Meftahi N, Greaves TL, McConville CF, Bryant G, Bryant SJ, Christofferson AJ. Nanostructure of a deep eutectic solvent at solid interfaces. J Colloid Interface Sci 2021; 591:38-51. [PMID: 33592524 DOI: 10.1016/j.jcis.2021.01.089] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 01/26/2021] [Accepted: 01/27/2021] [Indexed: 12/24/2022]
Abstract
HYPOTHESIS Deep eutectic solvents (DESs) are an attractive class of tunable solvents. However, their uptake for relevant applications has been limited due to a lack of detailed information on their structure-property relationships, both in the bulk and at interfaces. The lateral nanostructure of the DES-solid interfaces is likely to be more complex than previously reported and requires detailed, high-resolution investigation. EXPERIMENTS We employ a combination of high-resolution amplitude-modulated atomic force microscopy and molecular dynamics simulations to elucidate the lateral nanostructure of a DES at the solid-liquid interface. Specifically, the lateral and near-surface nanostructure of the DES choline chloride:glycerol is probed at the mica and highly-ordered pyrolytic graphite interfaces. FINDINGS The lateral nanostructure of the DES-solid interface is heterogeneous and well-ordered in both systems. At the mica interface, the DES is strongly ordered via polar interactions. The adsorbed layer has a distinct rhomboidal symmetry with a repeat spacing of ~0.9 nm comprising all DES species. At the highly ordered pyrolytic graphite interface, the adsorbed layer appears distinctly different, forming an apolor-driven row-like structure with a repeat spacing of ~0.6 nm, which largely excludes the chloride ion. The interfacial nanostructure results from a delicate balance of substrate templating, liquid-liquid interactions, species surface affinity, and packing constraints of cations, anions, and molecular components within the DES. For both systems, distinct near-surface nanostructural layering is observed, which becomes more pronounced close to the substrate. The surface nanostructures elucidated here significantly expand our understanding of DES interfacial behavior and will enhance the optimization of DES systems for surface-based applications.
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Affiliation(s)
- Aaron Elbourne
- School of Science, RMIT University, Melbourne, VIC 3000, Australia.
| | - Nastaran Meftahi
- ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Tamar L Greaves
- School of Science, RMIT University, Melbourne, VIC 3000, Australia
| | - Christopher F McConville
- School of Science, RMIT University, Melbourne, VIC 3000, Australia; Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216, Australia
| | - Gary Bryant
- School of Science, RMIT University, Melbourne, VIC 3000, Australia
| | - Saffron J Bryant
- School of Science, RMIT University, Melbourne, VIC 3000, Australia.
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16
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Lu Y, Chen W, Wang Y, Huo F, Dong Y, Wei L, He H. Research Progress on the Preparation and Properties of Two Dimensional Structure of Ionic Liquids. ACTA CHIMICA SINICA 2021. [DOI: 10.6023/a20100475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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17
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Meusel M, Lexow M, Gezmis A, Bayer A, Maier F, Steinrück HP. Growth of Multilayers of Ionic Liquids on Au(111) Investigated by Atomic Force Microscopy in Ultrahigh Vacuum. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:13670-13681. [PMID: 33156635 PMCID: PMC7676296 DOI: 10.1021/acs.langmuir.0c02596] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 10/20/2020] [Indexed: 06/11/2023]
Abstract
Understanding the growth of ultrathin films of ionic liquids (ILs) on metal surfaces is of highest relevance for a variety of applications. We present a detailed study of the growth of the wetting layer and successive multilayers of 1,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C1C1Im][Tf2N]) on Au(111). By atomic force microscopy (AFM) in ultrahigh vacuum, we follow the temperature-dependent behavior between 110 and 300 K at defined coverages. We initially observe the formation of a wetting layer with a thickness of ∼0.37 nm with anions and cations arranged in a checkerboard structure. Stable AFM imaging up to 280 K allows us to follow the IL growing on top of the wetting layer in bilayers with an average thickness of ∼0.71 nm, that is, double the height of the wetting layer, in a bilayer-by-bilayer fashion. This growth behavior is independently confirmed from the surface morphology, as deduced from AFM and angle-resolved X-ray photoelectron spectroscopy. High-resolution AFM images at 110 K allow for identifying the molecular surface structure of the bilayers as a striped phase, which is one of the phases also seen for the wetting layer (Meusel, M.; Lexow, M.; Gezmis, A.; Schotz, S.; Wagner, M.; Bayer, A.; Maier, F.; Steinrück, H. P. Atomic Force and Scanning Tunneling Microscopy of Ordered Ionic Liquid Wetting Layers from 110 K up to Room Temperature. ACS Nano 2020, 14, 9000-9010).
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Affiliation(s)
- Manuel Meusel
- Lehrstuhl für Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany
| | - Matthias Lexow
- Lehrstuhl für Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany
| | - Afra Gezmis
- Lehrstuhl für Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany
| | - Andreas Bayer
- Lehrstuhl für Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany
| | - Florian Maier
- Lehrstuhl für Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany
| | - Hans-Peter Steinrück
- Lehrstuhl für Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany
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18
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Ayatollahi SF, Bahrami M, Ghatee MH, Ghaed-Sharaf T. Simulating the Effect of Anions on Spreading of Nanodroplets and the Monolayer Behavior of Quaternary Ammonium-Based Ionic Liquids on Li(100) and Li(110) Metal Facets. Ind Eng Chem Res 2020. [DOI: 10.1021/acs.iecr.0c02442] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Maryam Bahrami
- Department of Chemistry, Shiraz University, Shiraz 71946, Iran
| | - Mohammad Hadi Ghatee
- Department of Chemistry, Shiraz University, Shiraz 71946, Iran
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
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19
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Meusel M, Lexow M, Gezmis A, Schötz S, Wagner M, Bayer A, Maier F, Steinrück HP. Atomic Force and Scanning Tunneling Microscopy of Ordered Ionic Liquid Wetting Layers from 110 K up to Room Temperature. ACS NANO 2020; 14:9000-9010. [PMID: 32609482 PMCID: PMC7391993 DOI: 10.1021/acsnano.0c03841] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 07/01/2020] [Indexed: 05/31/2023]
Abstract
Ionic liquids (ILs) are used as ultrathin films in many applications. We studied the nanoscale arrangement within the first layer of 1,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C1C1Im] [Tf2N]) on Au(111) between 400 and 110 K in ultrahigh vacuum by scanning tunneling and noncontact atomic force microscopy with molecular resolution. Compared to earlier studies on similar ILs, a different behavior is observed, which we attribute to the small size and symmetrical shape of the cation: (a) In both AFM and STM only the anions are imaged; (b) only long-range-ordered but no amorphous phases are observed; (c) the hexagonal room-temperature phase melts 30-50 K above the IL's bulk melting point; (d) at 110 K, striped and hexagonal superstructures with two and three ion pairs per unit cell, respectively, are found. AFM turned out to be more stable at higher temperature, while STM revealed more details at low temperature.
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Affiliation(s)
- Manuel Meusel
- Lehrstuhl
für Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Matthias Lexow
- Lehrstuhl
für Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Afra Gezmis
- Lehrstuhl
für Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Simon Schötz
- Lehrstuhl
für Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Margareta Wagner
- Lehrstuhl
für Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
| | - Andreas Bayer
- Lehrstuhl
für Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Florian Maier
- Lehrstuhl
für Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Hans-Peter Steinrück
- Lehrstuhl
für Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen, Germany
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20
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Wang YL, Li B, Sarman S, Mocci F, Lu ZY, Yuan J, Laaksonen A, Fayer MD. Microstructural and Dynamical Heterogeneities in Ionic Liquids. Chem Rev 2020; 120:5798-5877. [PMID: 32292036 PMCID: PMC7349628 DOI: 10.1021/acs.chemrev.9b00693] [Citation(s) in RCA: 192] [Impact Index Per Article: 48.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 12/11/2022]
Abstract
Ionic liquids (ILs) are a special category of molten salts solely composed of ions with varied molecular symmetry and charge delocalization. The versatility in combining varied cation-anion moieties and in functionalizing ions with different atoms and molecular groups contributes to their peculiar interactions ranging from weak isotropic associations to strong, specific, and anisotropic forces. A delicate interplay among intra- and intermolecular interactions facilitates the formation of heterogeneous microstructures and liquid morphologies, which further contributes to their striking dynamical properties. Microstructural and dynamical heterogeneities of ILs lead to their multifaceted properties described by an inherent designer feature, which makes ILs important candidates for novel solvents, electrolytes, and functional materials in academia and industrial applications. Due to a massive number of combinations of ion pairs with ion species having distinct molecular structures and IL mixtures containing varied molecular solvents, a comprehensive understanding of their hierarchical structural and dynamical quantities is of great significance for a rational selection of ILs with appropriate properties and thereafter advancing their macroscopic functionalities in applications. In this review, we comprehensively trace recent advances in understanding delicate interplay of strong and weak interactions that underpin their complex phase behaviors with a particular emphasis on understanding heterogeneous microstructures and dynamics of ILs in bulk liquids, in mixtures with cosolvents, and in interfacial regions.
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Affiliation(s)
- Yong-Lei Wang
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Bin Li
- School
of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, P. R. China
| | - Sten Sarman
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Francesca Mocci
- Department
of Chemical and Geological Sciences, University
of Cagliari, I-09042 Monserrato, Italy
| | - Zhong-Yuan Lu
- State
Key Laboratory of Supramolecular Structure and Materials, Institute
of Theoretical Chemistry, Jilin University, Changchun 130021, P. R. China
| | - Jiayin Yuan
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Aatto Laaksonen
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
- State
Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China
- Centre of
Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry Aleea Grigore Ghica-Voda, 41A, 700487 Iasi, Romania
- Department
of Engineering Sciences and Mathematics, Division of Energy Science, Luleå University of Technology, SE-97187 Luleå, Sweden
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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21
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Weber I, Kim J, Buchner F, Schnaidt J, Behm RJ. Surface Science and Electrochemical Model Studies on the Interaction of Graphite and Li-Containing Ionic Liquids. CHEMSUSCHEM 2020; 13:2589-2601. [PMID: 32196973 PMCID: PMC7317785 DOI: 10.1002/cssc.202000495] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Indexed: 06/10/2023]
Abstract
The process of solid-electrolyte interphase (SEI) formation is systematically investigated along with its chemical composition on carbon electrodes in an ionic liquid-based, Li-containing electrolyte in a combined surface science and electrochemical model study using highly oriented pyrolytic graphite (HOPG) and binder-free graphite powder electrodes (Mage) as model systems. The chemical decomposition process is explored by deposition of Li on a pre-deposited multilayer film of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSI]) under ultrahigh vacuum conditions. Electrochemical SEI formation is induced by and monitored during potential cycling in [BMP][TFSI]+0.1 m LiTFSI. The chemical composition of the resulting layers is characterized by X-ray photoelectron spectroscopy (XPS), both at the surface and in deeper layers, closer to the electrode|SEI interface, after partial removal of the film by Ar+ ion sputtering. Clear differences between chemical and electrochemical SEI formation, and also between SEI formation on HOPG and Mage electrodes, are observed and discussed.
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Affiliation(s)
- Isabella Weber
- Helmholtz-Institute Ulm (HIU) Electrochemical Energy StorageHelmholtzstraße 1189081UlmGermany
- Institute of Surface Chemistry and CatalysisUlm UniversityAlbert-Einstein-Allee 4789081UlmGermany
- Karlsruhe Institute of Technology (KIT)P.O. Box 364076021KarlsruheGermany
| | - Jihyun Kim
- Institute of Surface Chemistry and CatalysisUlm UniversityAlbert-Einstein-Allee 4789081UlmGermany
| | - Florian Buchner
- Institute of Surface Chemistry and CatalysisUlm UniversityAlbert-Einstein-Allee 4789081UlmGermany
| | - Johannes Schnaidt
- Helmholtz-Institute Ulm (HIU) Electrochemical Energy StorageHelmholtzstraße 1189081UlmGermany
- Institute of Surface Chemistry and CatalysisUlm UniversityAlbert-Einstein-Allee 4789081UlmGermany
- Karlsruhe Institute of Technology (KIT)P.O. Box 364076021KarlsruheGermany
| | - R. Jürgen Behm
- Helmholtz-Institute Ulm (HIU) Electrochemical Energy StorageHelmholtzstraße 1189081UlmGermany
- Institute of Surface Chemistry and CatalysisUlm UniversityAlbert-Einstein-Allee 4789081UlmGermany
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22
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Wang C, Qian C, Li Z, Wei N, Zhang N, Wang Y, He H. Molecular Insights into the Abnormal Wetting Behavior of Ionic Liquids Induced by the Solidified Ionic Layer. Ind Eng Chem Res 2020. [DOI: 10.1021/acs.iecr.0c00439] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chenlu Wang
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling 712100, People’s Republic of China
| | - Cheng Qian
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling 712100, People’s Republic of China
| | - Zhen Li
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling 712100, People’s Republic of China
| | - Ning Wei
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling 712100, People’s Republic of China
- Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, Jiangnan University, Wuxi 214122, People’s Republic of China
| | - Ning Zhang
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling 712100, People’s Republic of China
| | - Yanlei Wang
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
| | - Hongyan He
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
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23
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Lexow M, Massicot S, Maier F, Steinrück HP. Stability and Exchange Processes in Ionic Liquid/Porphyrin Composite Films on Metal Surfaces. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2019; 123:29708-29721. [PMID: 31867088 PMCID: PMC6913898 DOI: 10.1021/acs.jpcc.9b08531] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 11/12/2019] [Indexed: 06/10/2023]
Abstract
In light of increasing interest in the development of organic-organic multicomponent heterostructures on metals, this molecular-scale study investigates prototypical composite systems of ultrathin porphyrin and ionic liquid (IL) films on metallic supports under well-defined ultrahigh vacuum conditions. By means of angle-resolved X-ray photoelectron spectroscopy, we investigated the adsorption, stability, and thermal exchange of the resulting films after sequential physical vapor deposition of the free-base porphyrin 5,10,15,20-tetraphenylporphyrin, 2H-TPP, and the IL 1-methyl-3-octylimidazolium hexafluorophosphate, [C8C1Im][PF6], on Ag(111) and Au(111). 2H-TPP shows two-dimensional growth of up to two closed molecular layers on Ag(111) and Au(111) and three-dimensional island growth for thicker films. IL films on top of a monolayer of 2H-TPP exhibit Stranski-Krastanov-like growth and are stable up to 385 K. The 2H-TPP layer leads to destabilization of the IL films, compared to the IL in direct contact with the bare metals, by inhibiting the specific adsorption of the ions on the metal surfaces. When the porphyrin is deposited on top of [C8C1Im][PF6] at low temperature, the 2H-TPP molecules adsorb on top of the IL film at first but replace the IL at the IL/metal interfaces upon heating above 240 K. This exchange process is most likely driven by the higher adsorption energy of 2H-TPP on Ag(111) and Au(111) surfaces, as compared to the IL. The behavior observed on Ag(111) and Au(111) is identical. The results are highly relevant for the stability of porphyrin/IL-based thin film catalyst systems and molecular devices, and more generally, stacked organic multilayer architectures.
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24
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Liu S, Peng J, Chen L, Sebastián P, Feliu JM, Yan J, Mao B. In-situ STM and AFM Studies on Electrochemical Interfaces in imidazolium-based ionic liquids. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.04.066] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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25
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Lexow M, Heller BSJ, Partl G, Bhuin RG, Maier F, Steinrück HP. Cation Exchange at the Interfaces of Ultrathin Films of Fluorous Ionic Liquids on Ag(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:398-405. [PMID: 30540199 PMCID: PMC6377181 DOI: 10.1021/acs.langmuir.8b03517] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In the context of applications with thin ionic liquid (IL) films on solid supports, we studied the ion distribution within mixed thin IL films by angle-resolved X-ray photoelectron spectroscopy. After the deposition of 1-methyl-3-octylimidazolium hexafluorophosphate, [C8C1Im][PF6], on top of a wetting layer (WL) of 3-methyl-1-(3,3,4,4,4-pentafluorobutyl)imidazolium hexafluorophosphate, [PFBMIm][PF6], on Ag(111) at room temperature (RT), we find a preferential enrichment of the [PFBMIm]+ cation at the IL/vacuum interface. In a similar deposition experiment at 82 K, this cation exchange at the IL/solid interface does not occur. Upon heating the film from 82 K to RT, we observe the replacement of [C8C1Im]+ by [PFBMIm]+ at the IL/vacuum interface between ∼160 and ∼220 K. No further changes in the surface composition were observed between 220 K and RT. Upon further heating the mixed IL film, we find the complete desorption of [PFBMIm][PF6] from the mixed film below 410 K, leaving a WL of pure [C8C1Im][PF6] on Ag(111), which desorbs until 455 K.
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Affiliation(s)
- Matthias Lexow
- Lehrstuhl
für Physikalische Chemie 2, Friedrich-Alexander-Universität
Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
- M.L.: E-mail,
| | - Bettina S. J. Heller
- Lehrstuhl
für Physikalische Chemie 2, Friedrich-Alexander-Universität
Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
| | - Gabriel Partl
- Institut
für Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universität Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
| | - Radha G. Bhuin
- Lehrstuhl
für Physikalische Chemie 2, Friedrich-Alexander-Universität
Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
| | - Florian Maier
- Lehrstuhl
für Physikalische Chemie 2, Friedrich-Alexander-Universität
Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
| | - Hans-Peter Steinrück
- Lehrstuhl
für Physikalische Chemie 2, Friedrich-Alexander-Universität
Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
- H.-P.S.: E-mail,
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26
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Kamalakannan S, Prakash M, Chambaud G, Hochlaf M. Adsorption of Hydrophobic and Hydrophilic Ionic Liquids at the Au(111) Surface. ACS OMEGA 2018; 3:18039-18051. [PMID: 31458392 PMCID: PMC6643406 DOI: 10.1021/acsomega.8b02163] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 12/06/2018] [Indexed: 05/26/2023]
Abstract
Electrode-electrolyte microscopic interfacial studies are of great interest for the design and development of functional materials for energy storage and catalysis applications. First-principles-based simulation methods are used here to understand the structure, stability, energetics, and microscopic adsorption mechanism of various hydrophilic and hydrophobic ionic liquids (ILs; 1-butyl 3-methylimidazolium [BMIm]+[X]-, where X = Cl, DCA, HCOO, BF4, PF6, CH3SO3, OTF, and TFSA) interacting with a metallic surface. We have selected the Au(111) surface as a potential electrode model, and our computations show that ILs (anions and cations) adsorb specifically at some selective adsorption sites. Indeed, hydrophilic anions of ILs are strongly adsorbed on the gold surface (via Au-Cl and Au-N bonds at Au(111)), whereas hydrophobic anions are weakly bonded. The [BMIm]+ is always found to be stabilized parallel to the metal surface, irrespective of the nature of the anion, through various kinds of noncovalent interactions. Mulliken, Löwdin, and Hirshfeld charge analyses reveal that there is significant charge transfer between ILs and the surface that may enhance the charge transfer mechanism between the surface and electrolytes for electrochemical applications. Our study shows that the electrostatic and van der Waals interactions are in action at these interfaces. Moreover, we show that there are several covalent and noncovalent interactions between ILs and the metal surface. These interactions play an essential role to maintain the electrostatic behaviors at the solid-liquid interface. The present findings can be helpful to predict specific selectivity and subsequent design of materials for energy harvesting and catalysis applications.
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Affiliation(s)
- Shanmugasundaram Kamalakannan
- Department
of Chemistry and SRM Research Institute, SRM Institute of
Science and Technology, Kattankulathur 603203, Tamil Nadu, India
| | - Muthuramalingam Prakash
- Department
of Chemistry and SRM Research Institute, SRM Institute of
Science and Technology, Kattankulathur 603203, Tamil Nadu, India
| | - Gilberte Chambaud
- Laboratoire
Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, Université Paris-Est, 77454 Marne la
Vallée Cedex 2, France
| | - Majdi Hochlaf
- Laboratoire
Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, Université Paris-Est, 77454 Marne la
Vallée Cedex 2, France
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27
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Buchner F, Uhl B, Forster-Tonigold K, Bansmann J, Groß A, Behm RJ. Structure formation and surface chemistry of ionic liquids on model electrode surfaces-Model studies for the electrode | electrolyte interface in Li-ion batteries. J Chem Phys 2018; 148:193821. [PMID: 30307189 DOI: 10.1063/1.5012878] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Ionic liquids (ILs) are considered as attractive electrolyte solvents in modern battery concepts such as Li-ion batteries. Here we present a comprehensive review of the results of previous model studies on the interaction of the battery relevant IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]+[TFSI]-) with a series of structurally and chemically well-defined model electrode surfaces, which are increasingly complex and relevant for battery applications [Ag(111), Au(111), Cu(111), pristine and lithiated highly oriented pyrolytic graphite (HOPG), and rutile TiO2(110)]. Combining surface science techniques such as high resolution scanning tunneling microscopy and X-ray photoelectron spectroscopy for characterizing surface structure and chemical composition in deposited (sub-)monolayer adlayers with dispersion corrected density functional theory based calculations, this work aims at a molecular scale understanding of the fundamental processes at the electrode | electrolyte interface, which are crucial for the development of the so-called solid electrolyte interphase (SEI) layer in batteries. Performed under idealized conditions, in an ultrahigh vacuum environment, these model studies provide detailed insights on the structure formation in the adlayer, the substrate-adsorbate and adsorbate-adsorbate interactions responsible for this, and the tendency for chemically induced decomposition of the IL. To mimic the situation in an electrolyte, we also investigated the interaction of adsorbed IL (sub-)monolayers with coadsorbed lithium. Even at 80 K, postdeposited Li is found to react with the IL, leading to decomposition products such as LiF, Li3N, Li2S, LixSOy, and Li2O. In the absence of a [BMP]+[TFSI]- adlayer, it tends to adsorb, dissolve, or intercalate into the substrate (metals, HOPG) or to react with the substrate (TiO2) above a critical temperature, forming LiOx and Ti3+ species in the latter case. Finally, the formation of stable decomposition products was found to sensitively change the equilibrium between surface Li and Li+ intercalated in the bulk, leading to a deintercalation from lithiated HOPG in the presence of an adsorbed IL adlayer at >230 K. Overall, these results provide detailed insights into the surface chemistry at the solid | electrolyte interface and the initial stages of SEI formation at electrode surfaces in the absence of an applied potential, which is essential for the further improvement of future Li-ion batteries.
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Affiliation(s)
- Florian Buchner
- Helmholtz Institute Ulm Electrochemical Energy Storage (HIU), Helmholtzstraße 11, D-89081 Ulm, Germany
| | - Benedikt Uhl
- Institute of Surface Chemistry and Catalysis, Ulm University, Albert-Einstein-Allee 47, D-89081 Ulm, Germany
| | - Katrin Forster-Tonigold
- Helmholtz Institute Ulm Electrochemical Energy Storage (HIU), Helmholtzstraße 11, D-89081 Ulm, Germany
| | - Joachim Bansmann
- Institute of Surface Chemistry and Catalysis, Ulm University, Albert-Einstein-Allee 47, D-89081 Ulm, Germany
| | - Axel Groß
- Helmholtz Institute Ulm Electrochemical Energy Storage (HIU), Helmholtzstraße 11, D-89081 Ulm, Germany
| | - R Jürgen Behm
- Helmholtz Institute Ulm Electrochemical Energy Storage (HIU), Helmholtzstraße 11, D-89081 Ulm, Germany
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28
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Lexow M, Heller BSJ, Maier F, Steinrück HP. Anion Exchange at the Liquid/Solid Interface of Ultrathin Ionic Liquid Films on Ag(111). Chemphyschem 2018; 19:2978-2984. [PMID: 30193005 PMCID: PMC6282575 DOI: 10.1002/cphc.201800773] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Indexed: 11/24/2022]
Abstract
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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Affiliation(s)
- Matthias Lexow
- Lehrstuhl für Physikalische Chemie 2, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Bettina S J Heller
- Lehrstuhl für Physikalische Chemie 2, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Florian Maier
- Lehrstuhl für Physikalische Chemie 2, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
| | - Hans-Peter Steinrück
- Lehrstuhl für Physikalische Chemie 2, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany
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29
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Lexow M, Talwar T, Heller BSJ, May B, Bhuin RG, Maier F, Steinrück HP. Time-dependent changes in the growth of ultrathin ionic liquid films on Ag(111). Phys Chem Chem Phys 2018; 20:12929-12938. [PMID: 29701209 PMCID: PMC5944385 DOI: 10.1039/c8cp01411f] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Time dependent changes of IL film morphology depend on their molecular structure.
Various amounts of the ionic liquids (ILs) [C1C1Im][Tf2N] and [C8C1Im][Tf2N] were deposited in vacuo by physical vapour deposition (PVD) on single crystalline Ag(111) at room temperature and subsequently monitored by angle-resolved X-ray photoelectron spectroscopy (ARXPS) as a function of time. For very low coverages of up to one closed molecular layer, an initial wetting layer was rapidly formed for both ILs. Deposition of higher amounts of [C1C1Im][Tf2N] revealed an initial three-dimensional film morphology. On the time scale of hours, characteristic changes of the XPS signals were observed. These are interpreted as island spreading and a transformation towards a nearly two dimensional [C1C1Im][Tf2N] film as the final state. In contrast, a film morphology close to 2D was found from the very beginning for [C8C1Im][Tf2N] deposited on Ag(111) demonstrating the influence of the alkyl chain length on the growth kinetics. These studies also highlight the suitability of time-resolved ARXPS for the investigation of IL/solid interfaces, which play a crucial role in IL thin film applications such as in catalysis, sensor, lubrication, and coating technologies.
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Affiliation(s)
- Matthias Lexow
- Lehrstuhl für Physikalische Chemie 2, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany.
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30
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Wang YL, Golets M, Li B, Sarman S, Laaksonen A. Interfacial Structures of Trihexyltetradecylphosphonium-bis(mandelato)borate Ionic Liquid Confined between Gold Electrodes. ACS APPLIED MATERIALS & INTERFACES 2017; 9:4976-4987. [PMID: 28099800 DOI: 10.1021/acsami.6b14429] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Atomistic molecular dynamics simulations have been performed to study microscopic the interfacial ionic structures, molecular arrangements, and orientational preferences of trihexyltetradecylphosphonium-bis(mandelato)borate ([P6,6,6,14][BMB]) ionic liquid confined between neutral and charged gold electrodes. It was found that both [P6,6,6,14] cations and [BMB] anions are coabsorbed onto neutral electrodes at different temperatures. The hexyl and tetradecyl chains in [P6,6,6,14] cations lie preferentially flat on neutral electrodes. The oxalato and phenyl rings in [BMB] anions are characterized by alternative parallel-perpendicular orientations in the mixed innermost ionic layer adjacent to neutral electrodes. An increase in temperature has a marginal effect on the interfacial ionic structures and molecular orientations of [P6,6,6,14][BMB] ionic species in a confined environment. Electrifying gold electrodes leads to peculiar changes in the interfacial ionic structures and molecular orientational arrangements of [P6,6,6,14] cations and [BMB] anions in negatively and positively charged gold electrodes, respectively. As surface charge density increases (but lower than 20 μC/cm2), the layer thickness of the mixed innermost interfacial layer gradually increases due to a consecutive accumulation of [P6,6,6,14] cations and [BMB] anions at negatively and positively charged electrodes, respectively, before the formation of distinct cationic and anionic innermost layers. Meanwhile, the molecular orientations of two oxalato rings in the same [BMB] anions change gradually from a parallel-perpendicular feature to being partially characterized by a tilted arrangement at an angle of 45° from the electrodes and finally to a dominant parallel coordination pattern along positively charged electrodes. Distinctive interfacial distribution patterns are also observed accordingly for phenyl rings that are directly connected to neighboring oxalato rings in [BMB] anions.
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Affiliation(s)
- Yong-Lei Wang
- Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-106 91 Stockholm, Sweden
| | - Mikhail Golets
- Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-106 91 Stockholm, Sweden
| | - Bin Li
- Theoretical Chemistry, Chemical Center, Lund University , P.O. Box 124, SE-221 00 Lund, Sweden
| | - Sten Sarman
- Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-106 91 Stockholm, Sweden
| | - Aatto Laaksonen
- Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-106 91 Stockholm, Sweden
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31
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Biedron AB, Garfunkel EL, Castner EW, Rangan S. Ionic liquid ultrathin films at the surface of Cu(100) and Au(111). J Chem Phys 2017; 146:054704. [DOI: 10.1063/1.4975101] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Aleksandra B. Biedron
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, USA
| | - Eric L. Garfunkel
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, USA
| | - Edward W. Castner
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, USA
| | - Sylvie Rangan
- Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA
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32
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Liu Z, Li G, Cui T, Lahiri A, Borodin A, Endres F. Tuning the electronic environment of zinc ions with a ligand for dendrite-free zinc deposition in an ionic liquid. Phys Chem Chem Phys 2017; 19:25989-25995. [DOI: 10.1039/c7cp05345b] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dendrite-free zinc was obtained by tuning the electronic environment of zinc ions and the interfacial structure at the interface with a ligand.
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Affiliation(s)
- Zhen Liu
- Institute of Electrochemistry
- Clausthal University of Technology
- Arnold-Sommerfeld-Strasse 6
- Clausthal-Zellerfeld
- Germany
| | - Guozhu Li
- Institute of Electrochemistry
- Clausthal University of Technology
- Arnold-Sommerfeld-Strasse 6
- Clausthal-Zellerfeld
- Germany
| | - Tong Cui
- Institute of Electrochemistry
- Clausthal University of Technology
- Arnold-Sommerfeld-Strasse 6
- Clausthal-Zellerfeld
- Germany
| | - Abhishek Lahiri
- Institute of Electrochemistry
- Clausthal University of Technology
- Arnold-Sommerfeld-Strasse 6
- Clausthal-Zellerfeld
- Germany
| | - Andriy Borodin
- Institute of Electrochemistry
- Clausthal University of Technology
- Arnold-Sommerfeld-Strasse 6
- Clausthal-Zellerfeld
- Germany
| | - Frank Endres
- Institute of Electrochemistry
- Clausthal University of Technology
- Arnold-Sommerfeld-Strasse 6
- Clausthal-Zellerfeld
- Germany
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33
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Wagstaffe M, Jackman MJ, Syres KL, Generalov A, Thomas AG. Ionic Liquid Ordering at an Oxide Surface. Chemphyschem 2016; 17:3430-3434. [PMID: 27458919 PMCID: PMC5129479 DOI: 10.1002/cphc.201600774] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Indexed: 11/09/2022]
Abstract
The interaction of the ionic liquid [C4 C1 Im][BF4 ] with anatase TiO2 , a model photoanode material, has been studied using a combination of synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. The system is of interest as a model for fundamental electrolyte-electrode and dye-sensitized solar cells. The initial interaction involves degradation of the [BF4 ]- anion, resulting in incorporation of F into O vacancies in the anatase surface. At low coverages, [C4 C1 Im][BF4 ] is found to order at the anatase(101) surface via electrostatic attraction, with the imidazolium ring oriented 32±4° from the anatase TiO2 surface. As the coverage of ionic liquid increases, the influence of the oxide surface on the topmost layers is reduced and the ordering is lost.
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Affiliation(s)
- Michael Wagstaffe
- School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, M139PL, UK
| | - Mark J Jackman
- School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, M139PL, UK
| | - Karen L Syres
- Jeremiah Horrocks Institute, The University of Central Lancashire, Fylde Road, Preston, PR1 2HE, UK
| | | | - Andrew G Thomas
- School of Materials and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M139PL, UK
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34
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Black JM, Zhu M, Zhang P, Unocic RR, Guo D, Okatan MB, Dai S, Cummings PT, Kalinin SV, Feng G, Balke N. Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy. Sci Rep 2016; 6:32389. [PMID: 27587276 PMCID: PMC5009352 DOI: 10.1038/srep32389] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 08/03/2016] [Indexed: 11/09/2022] Open
Abstract
Atomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements are sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. The comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained.
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Affiliation(s)
- Jennifer M Black
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Mengyang Zhu
- State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Pengfei Zhang
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Raymond R Unocic
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Daqiang Guo
- State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - M Baris Okatan
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Sheng Dai
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Peter T Cummings
- Department of Chemical &Biomolecular Engineering and Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, TN, 37235, USA
| | - Sergei V Kalinin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Guang Feng
- State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Nina Balke
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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Elfassy E, Mastai Y, Pontoni D, Deutsch M. Liquid-Mercury-Supported Langmuir Films of Ionic Liquids: Isotherms, Structure, and Time Evolution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:3164-3173. [PMID: 26963651 DOI: 10.1021/acs.langmuir.6b00196] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Ionic liquids have been intensively developed for the last few decades and are now used in a wide range of applications, from electrochemistry to catalysis and nanotechnology. Many of these applications involve ionic liquid interfaces with other liquids and solids, the subnanometric experimental study of which is highly demanding, and has been little studied to date. We present here a study of mercury-supported Langmuir films of imidazolium-based ionic liquids by surface tensiometry and X-ray reflectivity. The charge-delocalized ionic liquids studied here exhibit no 2D lateral order but show diffuse surface-normal electron density profiles exhibiting gradual mercury penetration into the ionic liquid film, and surface-normal structure evolution over a period of hours. The effect of increasing the nonpolar alkyl chain length was also investigated. The results obtained provide insights into the interactions between these ionic liquids and liquid mercury and about the time evolution of the structure and composition of their interface.
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Affiliation(s)
| | | | - Diego Pontoni
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38000 Grenoble, France
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36
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Buchner F, Forster-Tonigold K, Bozorgchenani M, Gross A, Behm RJ. Interaction of a Self-Assembled Ionic Liquid Layer with Graphite(0001): A Combined Experimental and Theoretical Study. J Phys Chem Lett 2016; 7:226-233. [PMID: 26713562 DOI: 10.1021/acs.jpclett.5b02449] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The interaction between (sub)monolayers of the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide [BMP](+)[TFSA](-) and graphite(0001), which serves as a model for the anode|electolyte interface in Li-ion batteries, was investigated under ultrahigh vacuum conditions in a combined experimental and theoretical approach. High-resolution scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and dispersion-corrected density functional theory (DFT-D) calculations were employed. After vapor deposition at 300 K, XPS indicates molecular adsorbates with a 1:1 ratio of cations/anions. Cool down to ∼100 K leads to the formation of an ordered (2D) crystalline phase, which coexists with a mobile (2D) liquid. DFT-D calculations reveal that adsorbed [BMP](+) and [TFSA](-) species are arranged alternately in a row-like adsorption structure (cation-anion-cation-anion) and that adsorption is dominated by dispersion interactions between adlayer and substrate, on the one hand, and electrostatic interactions between the ions in a row, on the other hand. Simulated STM images of that structure closely resemble the experimental molecular resolved STM images and show that the resolved features mostly stem from the cations.
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Affiliation(s)
- Florian Buchner
- Helmholtz-Institute-Ulm (HIU) , Electrochemical Energy Storage, Helmholtzstraße 11, D-89081 Ulm, Germany
| | - Katrin Forster-Tonigold
- Helmholtz-Institute-Ulm (HIU) , Electrochemical Energy Storage, Helmholtzstraße 11, D-89081 Ulm, Germany
| | - Maral Bozorgchenani
- Ulm University , Institute of Surface Chemistry and Catalysis, Albert-Einstein-Allee 47, D-89081 Ulm, Germany
| | - Axel Gross
- Helmholtz-Institute-Ulm (HIU) , Electrochemical Energy Storage, Helmholtzstraße 11, D-89081 Ulm, Germany
- Ulm University , Institute of Theoretical Chemistry, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - R Jürgen Behm
- Helmholtz-Institute-Ulm (HIU) , Electrochemical Energy Storage, Helmholtzstraße 11, D-89081 Ulm, Germany
- Ulm University , Institute of Surface Chemistry and Catalysis, Albert-Einstein-Allee 47, D-89081 Ulm, Germany
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37
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Uhl B, Hekmatfar M, Buchner F, Behm RJ. Interaction of the ionic liquid [BMP][TFSA] with rutile TiO2(110) and coadsorbed lithium. Phys Chem Chem Phys 2016; 18:6618-36. [DOI: 10.1039/c5cp07433a] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The interaction of lithium, [BMP][TFSA] and their mixture with rutile TiO2(110), the thermal stability of the adlayers and the resulting reaction products are investigated under UHV conditions by STM and XPS.
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Affiliation(s)
- Benedikt Uhl
- Institute of Surface Chemistry and Catalysis
- Ulm University
- D-89081 Ulm
- Germany
- Helmholtz-Institute Ulm (HIU) Electrochemical Energy Storage
| | - Maral Hekmatfar
- Institute of Surface Chemistry and Catalysis
- Ulm University
- D-89081 Ulm
- Germany
- Helmholtz-Institute Ulm (HIU) Electrochemical Energy Storage
| | - Florian Buchner
- Institute of Surface Chemistry and Catalysis
- Ulm University
- D-89081 Ulm
- Germany
- Helmholtz-Institute Ulm (HIU) Electrochemical Energy Storage
| | - R. Jürgen Behm
- Institute of Surface Chemistry and Catalysis
- Ulm University
- D-89081 Ulm
- Germany
- Helmholtz-Institute Ulm (HIU) Electrochemical Energy Storage
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38
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Sebastián P, Climent V, Feliu JM. Characterization of the interfaces between Au(hkl) single crystal basal plane electrodes and [Emmim][Tf 2 N] ionic liquid. Electrochem commun 2016. [DOI: 10.1016/j.elecom.2015.11.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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