Electrical Double Layer Structure in Ionic Liquids: An Understanding of the Unusual Capacitance−Potential Curve at a Nonmetallic Electrode

Islam, Md. Mominul; Alam, Muhammad Tanzirul; Okajima, Takaharu; Ohsaka, Takeo

doi:10.1021/jp8114447

Cited by 99 publications

(118 citation statements)

References 22 publications

(128 reference statements)

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“…Furthermore, the level of the curves, and their overall shape, agrees well with experimental results (Islam et al , 2009;Lockett et al , 2008a), which tends to support our simple model. Still, since we are armed with a theory and a microscopic model, we can go further and make scrutinizing analyses of the microscopic structure at the surfaces.…”

Section: Performance Of the Dft For The Full Il Modelsupporting

confidence: 88%

“…In another lattice approach by Lauw and coworkers (Lauw et al , 2009), both cations and anions were modelled by a star-like architecture, with each monomer subject to an independently specified dielectric response. Under certain circumstances, these models were able to qualitatively reproduce the so-called "camel-shaped" differential capacitance, C D , profile observed in imidazolium ILs at carbon electrodes (Islam et al , 2009;Lockett et al , 2008a). This behaviour is an indication of subtle structuring effects at charged surfaces and is a stern test for theory.…”

Section: Other Approachesmentioning

confidence: 88%

“…In this case, neutral monomers adsorb weakly (a m w = 0.5), while anions (simple) and cations (charged monomers) display a strong adsorption (a c w = 1). differential capacitance data on metallic and non-metallic electrodes (Islam et al , 2009). Specifically, one will in general find a bell-shaped C D curve with metal electrodes (no camel-hump), and U-shaped C D with glassy carbon electrodes.…”

Section: Electrodes With Adsorption or Specific Adsorptionmentioning

confidence: 99%

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A Classical Density Functional Theory of Ionic Liquids

2011

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Classical Density Functional Theory of Ionic Liquids 3 Other approachesILs are fascinating from a theoretical standpoint. In order to treat ILs, a theory must account for both electrostatic and steric correlations. Attempts to develop such a theory have appeared in the literature. These include the lattice based model by Kornyshev and co-workers (Fedorov et al. , 2008;Kornyshev , 2007). In another lattice approach by Lauw and coworkers (Lauw et al. , 2009), both cations and anions were modelled by a star-like architecture, with each monomer subject to an independently specified dielectric response. Under certain circumstances, these models were able to qualitatively reproduce the so-called "camel-shaped" differential capacitance, C D , profile observed in imidazolium ILs at carbon electrodes (Islam et al. , 2009;Lockett et al. , 2008a). This behaviour is an indication of subtle structuring effects at charged surfaces and is a stern test for theory. Although camel-shaped C D profiles are predicted, qualitative discrepancy against experimental results remains. This is not surprising since these crude theories lack a proper description of electrostatic correlations despite accounting for steric contributions. Charge-charge correlations have been shown to be important in interfacial phenomena of highly coupled electrostatic fluids. As with dispersion forces, ionic correlations are always attractive and lower the total energy. Thus, we expect that they will also play a role in establishing the camel shape of the C D . That this is the case, is seen from both simulations (Lamperski & Zydor , 2007;Vatamanu et al. , 2010) (Fedorov et al. , 2010;Trulsson et al. , 2010), play an important role in determining their properties. In this work, we will use a model for ILs wherein the molecular ions interact via dispersion, as well as electrostatic, forces and the cation has an oligomeric structure consistent with imidazolium ions. This model has also been adopted by us in previous recent publications (Forsman et al. , 2011;Trulsson et al. , 2010), and employs the methods of polymer free energy density functional theory (DFT) (Woodward , 1991). The result will be a simple, albeit approximate DFT for ILs. We have already introduced the salient features of the theory in a previous publication (Forsman et al. , 2011). Here, we will present a much more thorough treatment, emphasizing the relation to theories of simpler fluids. We will also extend the scope of the study with some emphasis on temperature dependence and the effects of ion-specific adsorption. The IL-DFT that we will discuss here is an off-lattice theory, whose accuracy can be straightforwardly tested against computer simulations of the same molecular model. We will begin with a discussion of relevant earlier work, in order to introduce the essential mechanistic components that will be combined in our density functional theory for ionic liquids. Classical density functional theory (DFT) of simple fluidsThe ideal gas law is known and used by most physicists and chemist...

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Section: Performance Of the Dft For The Full Il Modelsupporting

confidence: 88%

Section: Other Approachesmentioning

confidence: 88%

Section: Electrodes With Adsorption or Specific Adsorptionmentioning

confidence: 99%

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A Classical Density Functional Theory of Ionic Liquids

2011

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“…Estimates based on Israelashsvili's publications generate capacitance curves behaving as GC at moderate potentials. Such behaviour is seen for some electrodes such as HOPG [78,79], but this is believed to be from the contribution of the space charge in semi-metallic graphite electrode rather than the double layer in ionic liquid (for analysis of those contributions see Ref. 31 and citations therein).…”

Section: Debye Length Implicationsmentioning

confidence: 99%

Mean-Field Theory of Electrical Double Layer In Ionic Liquids with Account of Short-Range Correlations

Goodwin

Feng

Kornyshev

2017

Electrochimica Acta

144

187

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We develop the theory of the electrical double layer in ionic liquids as proposed earlier by Kornyshev (2007). In the free energy function we keep the so called 'short-range correlation terms' which were omitted there. With some simplifying assumptions, we arrive at a modified expression for differential capacitance, which makes differential capacitance curves less sharply depending on electrode potential and having smaller values at extrema than in the previous theory. This brings the results closer to typical experimental observations, and makes it appealing to use this formalism for treatment of experimental data. Implications on Debye length and the extent of ion paring in ionic liquids are then briefly discussed.

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“…Up to now, differential capacitance curves have been measured on different electrodes including liquid metal Hg, [56,95,96] solid metals Au [29,97,98] and Pt, [83,84,[97][98][99] glassy carbon (GC), [48,97,98,100] and HOPG. [98,100] The ionic liquids involved are mainly with alkylimidazolium-based cations.…”

Section: Differential Capacitance Curvementioning

confidence: 99%

The Electrode/Ionic Liquid Interface: Electric Double Layer and Metal Electrodeposition

Wei

et al. 2010

ChemPhysChem

144

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The last decade has witnessed remarkable advances in interfacial electrochemistry in room‐temperature ionic liquids. Although the wide electrochemical window of ionic liquids is of primary concern in this new type of solvent for electrochemistry, the unusual bulk and interfacial properties brought about by the intrinsic strong interactions in the ionic liquid system also substantially influence the structure and processes at electrode/ionic liquid interfaces. Theoretical modeling and experimental characterizations have been indispensable in reaching a microscopic understanding of electrode/ionic liquid interfaces and in elucidating the physics behind new phenomena in ionic liquids. This Minireview describes the status of some aspects of interfacial electrochemistry in ionic liquids. Emphasis is placed on high‐resolution and molecular‐level characterization by scanning tunneling microscopy and vibrational spectroscopies of interfacial structures, and the initial stage of metal electrodeposition with application in surface nanostructuring.

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Electrical Double Layer Structure in Ionic Liquids: An Understanding of the Unusual Capacitance−Potential Curve at a Nonmetallic Electrode

Cited by 99 publications

References 22 publications

A Classical Density Functional Theory of Ionic Liquids

A Classical Density Functional Theory of Ionic Liquids

Mean-Field Theory of Electrical Double Layer In Ionic Liquids with Account of Short-Range Correlations

The Electrode/Ionic Liquid Interface: Electric Double Layer and Metal Electrodeposition

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