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Zhang Y, Li H, Wang J, Silvester DS, Warr GG, Atkin R. Potential-dependent superlubricity of stainless steel and Au(111) using a water-in-surface-active ionic liquid mixture. J Colloid Interface Sci 2024; 678:355-364. [PMID: 39208763 DOI: 10.1016/j.jcis.2024.08.187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2024] [Revised: 08/19/2024] [Accepted: 08/22/2024] [Indexed: 09/04/2024]
Abstract
HYPOTHESIS The friction and interfacial nanostructure of a water-in-surface-active ionic liquid mixture, 1.6 M 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate ([BMIm][AOT]), can be tuned by applying potential on Au(111) and stainless steel. EXPERIMENTAL Atomic force microscopy (AFM) was used to examine the friction and interfacial nanostructure of 1.6 M [BMIm][AOT] on Au(111) and stainless steel at different potentials. FINDINGS Superlubricity (vanishing friction) is observed for both surfaces at OCP+1.0 V up to a surface-dependent critical normal force due to [AOT]- bilayers adsorbing strongly to the positively charged surface thus allowing AFM tip to slide over solution-facing hydrated anion charged groups. High-resolution AFM imaging reveals ripple-like features within near-surface layers, with the smallest amplitudes at OCP+1 V, indicating the highest structural stability and resistance to thermal fluctuations due to highly ordered boundary [AOT]- bilayers templating robust near-surface layers. Exceeding the critical normal force at OCP+1.0 V causes the AFM tip to penetrate the hydrated [AOT]- layer and slide over alkyl chains, increasing friction. At OCP and OCP-1.0 V, higher friction correlates with more pronounced ripples, attributed to the rougher templating [BMIm]+ boundary layer. Kinetic experiments show that switching from OCP-1.0 V to OCP+1.0 V achieves superlubricity within 15 s, enabling real-time friction control.
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Affiliation(s)
- Yunxiao Zhang
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Hua Li
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia; Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Western Australia, Australia.
| | - Jianan Wang
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Debbie S Silvester
- School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth 6845, Western Australia, Australia
| | - Gregory G Warr
- School of Chemistry and Sydney Nano Institute, The University of Sydney, Sydney, New South Wales, Australia
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia.
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2
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Li H, Wang J, Warr GG, Atkin R. Nanostructure and Dynamics of the Locally Concentrated Ionic Liquid 2:1 (wt:wt) HMIM FAP:TFTFE and HMIM FAP on Graphite and Gold Electrodes as a Function of Potential. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2403109. [PMID: 39105361 DOI: 10.1002/smll.202403109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 07/26/2024] [Indexed: 08/07/2024]
Abstract
Video-rate atomic force microscopy (AFM) is used to record the near-surface nanostructure and dynamics of one pure ionic liquid (IL), 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (HMIM FAP), and a locally-concentrated IL comprising HMIM FAP with the low viscosity diluent 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFTFE), on highly oriented pyrolytic graphite (HOPG) and Au(111) electrodes as a function of potential. Over the potential range measured (open-circuit potential ± 1 V), different near-surface nanostructures are observed. For pure HMIM FAP, globular aggregates align in rows on HOPG, whereas elongated and worm-like nanostructures form on Au(111). For 2:1 (wt:wt) HMIM FAP:TFTFE, larger and less defined diluent swollen IL aggregates are present on both electrodes. Long-lived near-surface nanostructures for HMIM FAP and the 2:1 (wt:wt) HMIM FAP:TFTFE persist on both electrodes. 2:1 (wt:wt) HMIM FAP:TFTFE mixture diffuses more rapidly than pure HMIM FAP on both electrodes with obviously higher diffusion coefficients on HOPG than on Au(111) due to weaker electrostatic and solvophobic interactions between near-surface aggregates and Stern layer ions. These outcomes provide valuable insights for a wide range of IL applications in interface sciences, including electrolytes, catalysts, lubricants, and sensors.
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Affiliation(s)
- Hua Li
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
- Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, WA, 6009, Australia
| | - Jianan Wang
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Gregory G Warr
- School of Chemistry and Sydney Nano Institute, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
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Wang J, Buzolic JJ, Mullen JW, Fitzgerald PA, Aman ZM, Forsyth M, Li H, Silvester DS, Warr GG, Atkin R. Nanostructure of Locally Concentrated Ionic Liquids in the Bulk and at Graphite and Gold Electrodes. ACS NANO 2023; 17:21567-21584. [PMID: 37883191 DOI: 10.1021/acsnano.3c06609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2023]
Abstract
The physical properties of ionic liquids (ILs) have led to intense research interest, but for many applications, high viscosity is problematic. Mixing the IL with a diluent that lowers viscosity offers a solution if the favorable IL physical properties are not compromised. Here we show that mixing an IL or IL electrolyte (ILE, an IL with dissolved metal ions) with a nonsolvating fluorous diluent produces a low viscosity mixture in which the local ion arrangements, and therefore key physical properties, are retained or enhanced. The locally concentrated ionic liquids (LCILs) examined are 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIM TFSI), 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (HMIM FAP), or 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (BMIM FAP) mixed with 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFTFE) at 2:1, 1:1, and 1:2 (w/w) IL:TFTFE, as well as the locally concentrated ILEs (LCILEs) formed from 2:1 (w/w) HMIM TFSI-TFTFE with 0.25, 0.5, and 0.75 m lithium bis(trifluoromethylsulfonyl)imide (LiTFSI). Rheology and conductivity measurements reveal that the added TFTFE significantly reduces viscosity and increases ionic conductivity, and cyclic voltammetry (CV) reveals minimal reductions in electrochemical windows on gold and carbon electrodes. This is explained by the small- and wide-angle X-ray scattering (S/WAXS) and atomic force microscopy (AFM) data, which show that the local ion nanostructures are largely retained in LCILs and LCILEs in bulk and at gold and graphite electrodes for all potentials investigated.
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Affiliation(s)
- Jianan Wang
- School of Molecular Sciences, The University of Western Australia, Perth 6009, Australia
| | - Joshua J Buzolic
- School of Molecular Sciences, The University of Western Australia, Perth 6009, Australia
| | - Jesse W Mullen
- School of Molecular and Life Sciences, Curtin University, Perth 6102, Australia
| | - Paul A Fitzgerald
- Sydney Analytical, Core Research Facilities, The University of Sydney, Sydney 2050, Australia
| | - Zachary M Aman
- Department of Chemical Engineering, The University of Western Australia, Perth 6009, Australia
| | - Maria Forsyth
- Institute for Frontier Materials and the ARC Centre of Excellence for Electromaterials Science, Deakin University, Geelong 3220, Australia
| | - Hua Li
- School of Molecular Sciences, The University of Western Australia, Perth 6009, Australia
- Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth 6009, Australia
| | - Debbie S Silvester
- School of Molecular and Life Sciences, Curtin University, Perth 6102, Australia
| | - Gregory G Warr
- School of Chemistry and Sydney Nano Institute, The University of Sydney, Sydney 2050, Australia
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, Perth 6009, Australia
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4
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Freeman JS, Mamme MH, Ustarroz J, Warr GG, Li H, Atkin R. Molecular Resolution Nanostructure and Dynamics of the Deep Eutectic Solvent-Graphite Interface as a Function of Potential. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2204993. [PMID: 36627266 DOI: 10.1002/smll.202204993] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 12/08/2022] [Indexed: 06/17/2023]
Abstract
Interest in deep eutectic solvents (DESs), particularly for electrochemical applications, has boomed in the past decade because they are more versatile than conventional electrolyte solutions and are low cost, renewable, and non-toxic. The molecular scale lateral nanostructures as a function of potential at the solid-liquid interface-critical design parameters for the use of DESs as electrochemical solvents-are yet to be revealed. In this work, in situ amplitude modulated atomic force microscopy complemented by molecular dynamics simulations is used to probe the Stern and near-surface layers of the archetypal and by far most studied DES, 1:2 choline chloride:urea (reline), at the highly orientated pyrolytic graphite surface as a function of potential, to reveal highly ordered lateral nanostructures with unprecedented molecular resolution. This detail allows identification of choline, chloride, and urea in the Stern layer on graphite, and in some cases their orientations. Images obtained after the potential is switched from negative to positive show the dynamics of the Stern layer response, revealing that several minutes are required to reach equilibrium. These results provide valuable insight into the nanostructure and dynamics of DESs at the solid-liquid interface, with implications for the rational design of DESs for interfacial applications.
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Affiliation(s)
- Justin S Freeman
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, 6009, Australia
| | - Mesfin Haile Mamme
- Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Brussels, 1050, Belgium
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Brussels, 1050, Belgium
| | - Jon Ustarroz
- Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Brussels, 1050, Belgium
- Chemistry of Surfaces, Interfaces and Nanomaterials (ChemSIN), Université Libre de Bruxelles, Boulevard du Triomphe 2, Brussels, 1050, Belgium
| | - Gregory G Warr
- School of Chemistry and University of Sydney Nano Institute, The University of Sydney, Sydney, New South Wales, 2006, Australia
| | - Hua Li
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, 6009, Australia
- Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Western Australia, 6009, Australia
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, 6009, Australia
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5
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Li H, Liang Y, Ju W, Schneider O, Stimming U. In Situ Monitoring of the Surface Evolution of a Silver Electrode from Polycrystalline to Well-Defined Structures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:14981-14987. [PMID: 36395357 DOI: 10.1021/acs.langmuir.2c02748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Capturing the surface-structural dynamics of metal electrocatalysts under certain electrochemical environments is intriguingly desired for understanding the behavior of various metal-based electrocatalysts. However, in situ monitoring of the evolution of a polycrystalline metal surface at the interface of electrode-electrolyte solutions at negative/positive potentials with high-resolution scanning tunneling microscopy (STM) is seldom. Here, we use electrochemical STM (EC-STM) for in situ monitoring of the surface evolution process of a silver electrode in both an aqueous sodium hydroxide solution and an ionic liquid of 1-methyl-1-octylpyrrolidinium bis(trifluoromethylsulfonyl) amide driven by negative potentials. We found silver underwent a surface change from a polycrystalline structure to a well-defined surface arrangement in both electrolytes. In NaOH aqueous solution, the silver surface transferred in several minutes at a turning-point potential where hydrogen adsorbed and formed mainly (111) and (100) pits. Controversially, the surface evolution in the ionic liquid was much slower than that in the aqueous solution, and cation adsorption was observed in a wide potential range. The surface evolution of silver is proposed to be linked to the surface adsorbates as well as the formation of their complexes with undercoordinated silver atoms. The results also show that cathodic annealing of polycrystalline silver is a cheap, easy, and reliable way to obtain quasi-ordered crystal surfaces.
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Affiliation(s)
- Hongjiao Li
- School of Chemical Engineering, Sichuan University, Chengdu 610065, China
- Institut für Informatik VI, Technische Universität München, Schleißheimer Str. 90a, Garching b. München 85748, Germany
| | - Yunchang Liang
- Max Planck-EPFL Laboratory for Molecular Nanoscience and Technology, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
- Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Wenbo Ju
- School of Physics and Optoelectronics, South China University of Technology, Wushan Road 381, Guangzhou, Guangdong 510640, China
| | - Oliver Schneider
- Institut für Informatik VI, Technische Universität München, Schleißheimer Str. 90a, Garching b. München 85748, Germany
| | - Ulrich Stimming
- Department of Physics E19, Technische Universität München, James-Franck-Str.1, Garching b. München 85748, Germany
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6
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Reddy AB, Pilkington GA, Rutland MW, Glavatskih S. Tribotronic control of an ionic boundary layer in operando extends the limits of lubrication. Sci Rep 2022; 12:20479. [PMID: 36443307 PMCID: PMC9705526 DOI: 10.1038/s41598-022-22504-6] [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: 05/02/2022] [Accepted: 10/17/2022] [Indexed: 11/29/2022] Open
Abstract
The effect of electric potential on the lubrication of a non-halogenated phosphonium orthoborate ionic liquid used as an additive in a biodegradable oil was studied. An in-house tribotronic system was built around an instrument designed to measure lubricant film thickness between a rolling steel ball and a rotating silica-coated glass disc. The application of an electric field between the steel ball and a set of customized counter-electrodes clearly induced changes in the thickness of the lubricant film: a marked decrease at negative potentials and an increase at positive potentials. Complementary neutron reflectivity studies demonstrated the intrinsic electroresponsivity of the adsorbate: this was performed on a gold-coated silicon block and made possible in the same lubricant system by deuterating the oil. The results indicate that the anions, acting as anchors for the adsorbed film on the steel surface, are instrumental in the formation of thick and robust lubricating ionic boundary films. The application of a high positive potential, outside the electrochemical window, resulted in an enormous boost to film thickness, implicating the formation of ionic multi-layers and demonstrating the plausibility of remote control of failing contacts in inaccessible machinery, such as offshore wind and wave power installations.
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Affiliation(s)
- Akepati Bhaskar Reddy
- System and Component Design, Department of Machine Design, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden
| | - Georgia A Pilkington
- Division of Surface Chemistry and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden
| | - Mark W Rutland
- Division of Surface Chemistry and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden.
- Laboratoire de Tribologie et de Dynamique des Systèmes, Ecole Centrale de Lyon, 69134, Ecully, France.
- School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia.
| | - Sergei Glavatskih
- System and Component Design, Department of Machine Design, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden.
- School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia.
- Department of Electromechanical, Systems and Metal Engineering, Ghent University, 9052, Ghent, Belgium.
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7
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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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8
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Katakura S, Amano KI, Sakka T, Bu W, Lin B, Schlossman ML, Nishi N. Evolution and Reversible Polarity of Multilayering at the Ionic Liquid/Water Interface. J Phys Chem B 2020; 124:6412-6419. [PMID: 32600035 DOI: 10.1021/acs.jpcb.0c03711] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Highly correlated positioning of ions underlies Coulomb interactions between ions and electrified interfaces within dense ionic fluids such as biological cells and ionic liquids. Recent work has shown that highly correlated ionic systems behave differently than dilute electrolyte solutions, and interest is focused upon characterizing the electrical and structural properties of the dense electrical double layers (EDLs) formed at internal interfaces. It has been a challenge for experiments to characterize the progressive development of the EDL on the nanoscale as the interfacial electric potential is varied over a range of positive and negative values. Here we address this challenge by measuring X-ray reflectivity from the interface between an ionic liquid (IL) and a dilute aqueous electrolyte solution over a range of interfacial potentials from -450 to 350 mV. The growth of alternately charged cation-rich and anion-rich layers was observed along with a polarity reversal of the layers as the potential changed sign. These data show that the structural development of an ionic multilayer-like EDL with increasing potential is similar to that suggested by phenomenological theories and MD simulations, although our data also reveal that the excess charge beyond the first ionic layer decays more rapidly than predicted.
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Affiliation(s)
- Seiji Katakura
- Department of Energy and Hydrocarbon Chemistry, Kyoto University, Kyoto 615-8510, Japan
| | - Ken-Ichi Amano
- Department of Energy and Hydrocarbon Chemistry, Kyoto University, Kyoto 615-8510, Japan.,Faculty of Agriculture, Meijo University, Nagoya, Aichi 468-8502, Japan
| | - Tetsuo Sakka
- Department of Energy and Hydrocarbon Chemistry, Kyoto University, Kyoto 615-8510, Japan
| | - Wei Bu
- ChemMatCARS, Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, United States
| | - Binhua Lin
- ChemMatCARS, Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, United States
| | - Mark L Schlossman
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Naoya Nishi
- Department of Energy and Hydrocarbon Chemistry, Kyoto University, Kyoto 615-8510, Japan
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9
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Hjalmarsson N, Bergendal E, Wang YL, Munavirov B, Wallinder D, Glavatskih S, Aastrup T, Atkin R, Furó I, Rutland MW. Electro-Responsive Surface Composition and Kinetics of an Ionic Liquid in a Polar Oil. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:15692-15700. [PMID: 31581771 DOI: 10.1021/acs.langmuir.9b02119] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The quartz crystal microbalance (QCM) has been used to study how the interfacial layer of an ionic liquid dissolved in a polar oil at low weight percentages responds to changes in applied potential. The changes in surface composition at the QCM gold surface depend on both the magnitude and sign of the applied potential. The time-resolved response indicates that the relaxation kinetics are limited by the diffusion of ions in the interfacial region and not in the bulk, since there is no concentration dependence. The measured mass changes cannot be explained only in terms of simple ion exchange; the relative molecular volumes of the ions and the density changes in response to ion exclusion must be considered. The relaxation behavior of the potential between the electrodes upon disconnecting the applied potential is more complex than that observed for pure ionic liquids, but a measure of the surface charge can be extracted from the exponential decay when the rapid initial potential drop is accounted for. The adsorbed film at the gold surface consists predominantly of ionic liquid despite the low concentration, which is unsurprising given the surtactant-like structures of (some of) the ionic liquid ions. Changes in response to potential correspond to changes in the relative numbers of cations and anions, rather than a change in the oil composition. No evidence for an electric field induced change in viscosity is observed. This work shows conclusively that electric potentials can be used to control the surface composition, even in an oil-based system, and paves the way for other ion solvent studies.
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Affiliation(s)
| | | | | | | | | | - Sergei Glavatskih
- Department of Electrical Energy, Metals, Mechanical Constructions and Systems , Ghent University , B-9000 , Ghent , Belgium
| | | | - Rob Atkin
- School of Molecular Sciences , University of Western Australia , 6009 Perth , Australia
| | | | - Mark W Rutland
- Surfaces, Processes and Formulation , RISE Research Institutes of Sweden , SE-50115 Stockholm , Sweden
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10
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Electric double layer structure and capacitance of imidazolium-based ionic liquids with FSI− and Tf− anions at graphite electrode by molecular dynamic simulations. J Electroanal Chem (Lausanne) 2019. [DOI: 10.1016/j.jelechem.2019.113452] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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11
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Panhwar GM, Mysyk R, Rojo T, Shaikhutdinov S, Bondarchuk O. Electrowetting of Ionic Liquid on Graphite: Probing via in Situ Electrochemical X-ray Photoelectron Spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:14528-14536. [PMID: 30412414 DOI: 10.1021/acs.langmuir.8b02900] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Thin films of ionic liquid 1-ethyl-3-methylimidazolium bis(fluoromethylsulfonyl)imide ([EMIm][FSI]) vapor-deposited on highly oriented pyrographite (HOPG) were studied by X-ray photoelectron spectroscopy and atomic force microscopy. The results revealed a reversible morphological transition from a "drop-on-layer" structure to a "flat-layer" structure at positive, and not at negative, polarization. The effect is rationalized in terms of electric-field-induced reduction of the liquid-solid transition temperature in the ionic liquid film, when its thickness is comparable to the charge screening length. The observed bias asymmetry of [EMIm][FSI] electrowetting on HOPG is tentatively explained by the bilayer structure at the interface driven by the affinity of the imidazolium ring to the HOPG surface.
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Affiliation(s)
- Ghulam M Panhwar
- CIC Energigune , Parque Tecnológico de Alava , c/A. Einstein 48 , 01510 Miñano , Alava , Spain
| | - Roman Mysyk
- CIC Energigune , Parque Tecnológico de Alava , c/A. Einstein 48 , 01510 Miñano , Alava , Spain
| | - Teófilo Rojo
- CIC Energigune , Parque Tecnológico de Alava , c/A. Einstein 48 , 01510 Miñano , Alava , Spain
| | - Shamil Shaikhutdinov
- Abteilung Chemische Physik , Fritz-Haber-Institut der Max-Planck-Gesellschaft , Faradayweg 4-6 , 14195 Berlin , Germany
| | - Oleksandr Bondarchuk
- CIC Energigune , Parque Tecnológico de Alava , c/A. Einstein 48 , 01510 Miñano , Alava , Spain
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12
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Jo S, Park SW, Noh C, Jung Y. Computer simulation study of differential capacitance and charging mechanism in graphene supercapacitors: Effects of cyano-group in ionic liquids. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2018.07.126] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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13
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Bordes E, Douce L, Quitevis EL, Pádua AAH, Costa Gomes M. Ionic liquids at the surface of graphite: Wettability and structure. J Chem Phys 2018; 148:193840. [DOI: 10.1063/1.5010604] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Affiliation(s)
- Emilie Bordes
- Institut de Chimie de Clermont-Ferrand, Université Clermont Auvergne and CNRS, 63178 Aubière, France
| | - Laurent Douce
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg and CNRS, 67034 Strasbourg, France
| | - Edward L. Quitevis
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA
| | - Agílio A. H. Pádua
- Institut de Chimie de Clermont-Ferrand, Université Clermont Auvergne and CNRS, 63178 Aubière, France
| | - Margarida Costa Gomes
- Institut de Chimie de Clermont-Ferrand, Université Clermont Auvergne and CNRS, 63178 Aubière, France
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Insight into the Electrical Double Layer of an Ionic Liquid on Graphene. Sci Rep 2017; 7:4225. [PMID: 28652593 PMCID: PMC5484676 DOI: 10.1038/s41598-017-04576-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 05/24/2017] [Indexed: 11/14/2022] Open
Abstract
Graphene is a promising next-generation conducting material with the potential to replace traditional electrode materials in supercapacitors. Since energy storage in supercapacitors relies on the electrolyte-electrode interface, here we elucidate the interfacial subnanometer structure of a single component liquid composed solely of cations and anions – an ionic liquid- on electrified graphene. We study the effect of applied potential on the interaction between graphene and a silicon tip in an ionic liquid and describe it within the framework of the Derjaguin-Landau-Verwey-Overbeck (DLVO) theory. The energy is stored in an electrical double layer composed of an extended Stern layer, which consists of multiple ion layers over ~2 nanometers, beyond which a diffuse layer forms to compensate the applied potential on graphene. The electrical double layer significantly responds to the applied potential, and it shows the transition from overscreening to crowding of counterions at the interface at the highest applied potentials. It is proposed that surface charging occurs through the adsorption of the imidazolium cation to unbiased graphene (likely due to π-π interactions) and that the surface potential is better compensated when counterion crowding happens. This study scrutinizes the electrified graphene-ionic liquid interface, with implications not only in the field of energy storage, but also in lubrication.
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Wang Z, Li H, Atkin R, Priest C. Influence of Water on the Interfacial Nanostructure and Wetting of [Rmim][NTf2] Ionic Liquids at Mica Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:8818-8825. [PMID: 27486675 DOI: 10.1021/acs.langmuir.6b01790] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The effect of water concentration on the interfacial nanostructure and wetting behavior of a family of ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Rmim][NTf2], at the surface of mica was investigated by contact angle measurement and atomic force microscopy (AFM). AFM reveals that interfacial layers of ILs observed at the surface of mica for "dry" ILs are not present for water-saturated ILs. The interaction of the IL ions of [Rmim][NTf2] with water molecules through hydrogen bonding is suspected to disrupt IL ion layering and precursor film growth on mica. Without the IL precursor film, contact angle relaxation of "wet" ILs on mica is less significant and ambient vapor adsorption becomes more important in determining the macroscopic wetting behavior.
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Affiliation(s)
- Zhantao Wang
- Ian Wark Research Institute, University of South Australia , Mawson Lakes 5095, Australia
| | - Hua Li
- Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle , Callaghan, New South Wales 2308, Australia
| | - Rob Atkin
- Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle , Callaghan, New South Wales 2308, Australia
| | - Craig Priest
- Ian Wark Research Institute, University of South Australia , Mawson Lakes 5095, Australia
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17
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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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The electrochemical interface of Ag(111) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid—A combined in-situ scanning probe microscopy and impedance study. Electrochim Acta 2016. [DOI: 10.1016/j.electacta.2015.12.227] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Liu G, Cai M, Wang X, Zhou F, Liu W. Magnetite-Loaded Thermosensitive Nanogels for Bioinspired Lubrication and Multimodal Friction Control. ACS Macro Lett 2016; 5:144-148. [PMID: 35668589 DOI: 10.1021/acsmacrolett.5b00860] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability to control friction is quite attractive for many applications. Other than mechanical/physical methods to control friction, this letter shows how materials chemistry can regulate friction effectively. Magnetite-loaded thermosensitive poly(N-isopropylacrylamide) nanogels (Fe3O4@PNIPAM) were synthesized as nanoparticulate soft matter to reduce friction when it is used as an additive in aqueous lubricant. Interestingly, friction can be multiply regulated by temperature, magnetism, and near-infrared light through manipulating the colloidal properties of multifunctional composite nanogels in bulk solution and at the frictional interface.
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Affiliation(s)
- Guoqiang Liu
- State
Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical
Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Meirong Cai
- State
Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical
Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
| | - Xiaolong Wang
- State
Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical
Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
| | - Feng Zhou
- State
Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical
Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
| | - Weimin Liu
- State
Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical
Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
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Costa R, Pereira CM, Silva AF. Charge Storage on Ionic Liquid Electric Double Layer: The Role of the Electrode Material. Electrochim Acta 2015. [DOI: 10.1016/j.electacta.2015.02.180] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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21
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Forse AC, Griffin JM, Merlet C, Bayley PM, Wang H, Simon P, Grey CP. NMR Study of Ion Dynamics and Charge Storage in Ionic Liquid Supercapacitors. J Am Chem Soc 2015; 137:7231-42. [PMID: 25973552 PMCID: PMC4500645 DOI: 10.1021/jacs.5b03958] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Ionic liquids are emerging as promising new electrolytes for supercapacitors. While their higher operating voltages allow the storage of more energy than organic electrolytes, they cannot currently compete in terms of power performance. More fundamental studies of the mechanism and dynamics of charge storage are required to facilitate the development and application of these materials. Here we demonstrate the application of nuclear magnetic resonance spectroscopy to study the structure and dynamics of ionic liquids confined in porous carbon electrodes. The measurements reveal that ionic liquids spontaneously wet the carbon micropores in the absence of any applied potential and that on application of a potential supercapacitor charging takes place by adsorption of counterions and desorption of co-ions from the pores. We find that adsorption and desorption of anions surprisingly plays a more dominant role than that of the cations. Having elucidated the charging mechanism, we go on to study the factors that affect the rate of ionic diffusion in the carbon micropores in an effort to understand supercapacitor charging dynamics. We show that the line shape of the resonance arising from adsorbed ions is a sensitive probe of their effective diffusion rate, which is found to depend on the ionic liquid studied, as well as the presence of any solvent additives. Taken as whole, our NMR measurements allow us to rationalize the power performances of different electrolytes in supercapacitors.
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Affiliation(s)
- Alexander C Forse
- †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - John M Griffin
- †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Céline Merlet
- †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Paul M Bayley
- †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Hao Wang
- †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Patrice Simon
- §Université Paul Sabatier Toulouse III, CIRIMAT, UMR-CNRS 5085, F-31062 Toulouse, France.,∥Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France
| | - Clare P Grey
- †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.,‡Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
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