Molecular Insights into the Potential and Temperature Dependences of the Differential Capacitance of a Room-Temperature Ionic Liquid at Graphite Electrodes

Vatamanu, Jenel; Borodin, Oleg; Smith, Grant D.

doi:10.1021/ja104273r

Cited by 313 publications

(417 citation statements)

References 92 publications

(129 reference statements)

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“…51 Theoretical studies confirmed the existence of spatial heterogeneities at the interface due to the formation of polar and non-polar domains of the IL-molecules, as well as the existence of highly compressible alternating multilayers. 52,53,54,55,56 At very high negative potentials we could not find ordered superstructures such as those exist on Au(100) in BMIPF6, where ordered double-row structures of the cations could be observed (Fig. 9.…”

Section: In-situ Stmmentioning

confidence: 73%

The interface between HOPG and 1-butyl-3-methyl-imidazolium hexafluorophosphate

Müller

Németh

Vesztergom

et al. 2016

Phys. Chem. Chem. Phys.

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The interface between highly oriented pyrolytic graphite (HOPG) and 1-butyl-3-metyl-imidazolium hexafluorophosphate (BMIPF6) has been studied using cyclic voltammetry, electrochemical impedance spectroscopy, immersion charge measurements and in-situ scanning tunneling microscopy (insitu STM). The results are compared with those obtained with Au(100) in BMIPF6 (Phys.Chem.Chem.Phys., 2011, 13, 11627). The main result is that the high frequency capacitance spectra on the two systems are similar to each other, however at low frequencies some slow interfacial processes cause the appearance of a second capacitance arc on Au(100), which is absent for HOPG. The slow processes are attributed to the rearrangement of the Au surface structure and to the formation of ionic liquid adlayers -these are visualized by in-situ STM.

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Section: In-situ Stmmentioning

confidence: 73%

The interface between HOPG and 1-butyl-3-methyl-imidazolium hexafluorophosphate

Müller

Németh

Vesztergom

et al. 2016

Phys. Chem. Chem. Phys.

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“…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.…”

mentioning

confidence: 67%

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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“…[19][20][21] In the second cell ('composite electrode', nm. In each of these graphene membranes we carved two holes, each of diameter D=10Å (Fig.…”

Section: Simulation Detailsmentioning

confidence: 99%

Promising Performance Indicators for Water Desalination and Aqueous Capacitors Obtained by Engineering the Electric Double Layer in Nano-Structured Carbon Electrodes

Striolo

2015

J. Phys. Chem. C

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It is well known that the electric double layer plays important roles in a variety of applications, ranging from biology to materials sciences. Many studied the electric double layer using a variety of techniques, and as a result our understanding is mature, although not complete. Based on detailed understanding, we expect that by manipulating the electric double layer we could advance tremendously applications in the water-energy nexus. This is particularly true for electric double layer capacitors and capacitive desalination devices. However, such manipulation is not straightforward because of a competition of phenomena that occur within the electric double layer itself, including solvation effects, excluded volume phenomena, and ion-ion correlations. Using molecular dynamics simulations, we designed a composite graphene-based electrode to manipulate structural and dynamical properties of the electric double layer. Our design favors the formation of the compact Helmholtz layer. Inherent to our design is that the compact Helmholtz layer not only is atomically thick, but it is also highly mobile in the direction parallel to the charged surface. We suggest here how to exploit the properties of the engineered electric double layer towards developing a new continuous desalination process that combines the advantages of membrane and capacitive desalination processes, reducing their shortcomings.Insights on the molecular mechanisms relevant to the water-energy nexus are provided.2

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Molecular Insights into the Potential and Temperature Dependences of the Differential Capacitance of a Room-Temperature Ionic Liquid at Graphite Electrodes

Cited by 313 publications

References 92 publications

The interface between HOPG and 1-butyl-3-methyl-imidazolium hexafluorophosphate

The interface between HOPG and 1-butyl-3-methyl-imidazolium hexafluorophosphate

A Classical Density Functional Theory of Ionic Liquids

Promising Performance Indicators for Water Desalination and Aqueous Capacitors Obtained by Engineering the Electric Double Layer in Nano-Structured Carbon Electrodes

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