Theoretical Prediction of the Capacitance of Ionic Liquid Films

Szparaga, Ryan; Woodward, Clifford E.; Forsman, Jan

doi:10.1021/jp3053357

Cited by 20 publications

(18 citation statements)

References 24 publications

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“…Furthermore, this voltage can be 'tuned' by varying the average width of the electrode pores. As found in our previous work [14], we also find enhanced capacitances under supercritical conditions (close to the transition critical point). This is not surprising, as the differential capacitance is a thermodynamic response function that diverges at critical points.…”

Section: Introductionsupporting

confidence: 90%

Capillary Condensation of Ionic Liquid Solutions in Porous Electrodes

2013

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We use classical density functional theory to investigate room temperature ionic liquid + solvent mixtures in porous electrodes. We consider those mixtures that display a misicbility gap in the bulk fluid and hence have the capacity undergo capillary condensation in pores which preferentially attract the ionic liquid component. A novel aspect of this transition is that, when the system is at or near the critical point for this transition, we find an extraordinary increase in the capacitance, which derives from the fact that the capacitance is a thermodynamic response function, diverging at spinodal points.

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Section: Introductionsupporting

confidence: 90%

Capillary Condensation of Ionic Liquid Solutions in Porous Electrodes

2013

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“…The formalism developed here can also be generalized to include larger neutral clusters, or specific clusters of say cation-cation pairs due to π − π stacking in alkyl-imidazoliums. The coarse-grained RTIL model has been previously described [5,28,29]. Secondly, we will explore the implications of ion pair formation on a number of the predictions of the DFT.…”

Section: Recent Molecular Dynamics (Md) Simulations By Vatamanu Et Almentioning

confidence: 99%

Influence of ion pairing in ionic liquids on electrical double layer structures and surface force using classical density functional approach

Forsman

Woodward

2015

The Journal of Chemical Physics

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We explore the influence of ion pairing in room temperature ionic liquids confined by planar electrode surfaces. Using a coarse-grained model for the aromatic ionic liquid [C4MIM+][BF4−], we account for an ion pairing component as an equilibrium associating species within a classical density functional theory. We investigated the resulting structure of the electrical double layer as well as the ensuing surface forces and differential capacitance, as a function of the degree of ion association. We found that the short-range structure adjacent to surfaces was remarkably unaffected by the degree of ion pairing, up to several molecular diameters. This was even the case for 100% of ions being paired. The physical implications of ion pairing only become apparent in equilibrium properties that depend upon the long-range screening of charges, such as the asymptotic behaviour of surface forces and the differential capacitance, especially at low surface potential. The effect of ion pairing on capacitance is consistent with their invocation as a source of the anomalous temperature dependence of the latter. This work shows that ion pairing effects on equilibrium properties are subtle and may be difficult to extract directly from simulations.

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“…The problem may potentially be further exacerbated in the relatively restricted confines of small charged pores, by the formation of "ordered" structures, more akin to one-and two-dimensional solids. 4,5,25 Many strategies, such as configuration bias Monte Carlo, 26−28 continuous fractional component Monte Carlo, 29,30 or weighted-histogram methods, 31 improve the efficiency of insertion moves. In addition, other techniques have also been developed that maintain equilibrium with an "unknown" bulk in non-uniform fluids.…”

Section: Introductionmentioning

confidence: 99%

Local Grand Canonical Monte Carlo Simulation Method for Confined Fluids

et al. 2019

J. Chem. Theory Comput.

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We describe a new local grand canonical Monte Carlo method to treat fluids in pores in chemical equilibrium with a reference bulk. The method is applied to Lennard-Jones particles in pores of different geometry and is shown to be much more accurate and efficient than other techniques such as traditional grand canonical simulations or Widom’s particle insertion method. It utilizes a penalty potential to create a gas phase, which is in equilibrium with a more dense liquid component in the pore. Grand canonical Monte Carlo moves are employed in the gas phase, and the system then maintains chemical equilibrium by “diffusion” of particles. This creates an interface, which means that the confined fluid needs to occupy a large enough volume so that this is not an issue. We also applied the method to confined charged fluids and show how it can be used to determine local electrostatic potentials in the confined fluid, which are properly referenced to the bulk. This precludes the need to determine the Donnan potential (which controls electrochemical equilibrium) explicitly. Prior approaches have used explicit bulk simulations to measure this potential difference, which are significantly costly from a computational point of view. One outcome of our analysis is that pores of finite cross-section create a potential difference with the bulk via a small but nonzero linear charge density, which diminishes as ∼1/ln(L), where L is the pore length.

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Theoretical Prediction of the Capacitance of Ionic Liquid Films

Cited by 20 publications

References 24 publications

Capillary Condensation of Ionic Liquid Solutions in Porous Electrodes

Capillary Condensation of Ionic Liquid Solutions in Porous Electrodes

Influence of ion pairing in ionic liquids on electrical double layer structures and surface force using classical density functional approach

Local Grand Canonical Monte Carlo Simulation Method for Confined Fluids

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