The Role of Ion–Ion Correlations for the Differential Capacitance of Ionic Liquids

Downing, Rachel; Bossa, Guilherme Volpe; May, Sylvio

doi:10.1021/acs.jpcc.8b09756

Cited by 19 publications

(11 citation statements)

References 56 publications

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“…Therefore, the purely configurational entropy of the ions in a single 2D adlayer cannot explain the experimental data. Including particle interactions, for example, by the quasi-chemical approximation, would not substantially alter this conclusion. Moreover, several theoretical groups, for example, Kornyshev and Qiao proposed a rather 3D instead of 2D restructuring of the EDL which is in line with the formation of multilayers as found for this system by AFM .…”

Section: Discussionmentioning

confidence: 96%

Entropy Changes upon Double Layer Charging at a (111)-Textured Au Film in Pure 1-Butyl-1-Methylpyrrolidinium Bis[(trifluoromethyl)sulfonyl]imide Ionic Liquid

et al. 2019

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We investigated the entropy of the electrical double layer (EDL) formation at a (111)-textured Au film in the ionic liquid 1-butyl-1methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide by electrochemical microcalorimetry. We found reversible heat exchange upon EDL charging in the potential range of −0.6 to 1 V versus Fc/Fc + . Dependent on the potential, the heat evolution continued for 10 to 200 ms after the current flow, indicating slow reorganization of the EDL on this time scale. The partial molar entropy of the formation of the EDL Δ R S form was derived from the reversibly exchanged heat upon EDL charging. It varied about linearly with the potential from 27 J K −1 mol −1 at −0.6 V to −79 J K −1 mol −1 at 1 V versus Fc/Fc + . Δ R S form crosses zero close to the potential of zero charge of the system. The entropy values are much higher than those arising from purely configurational entropy of a 2D lattice gas, thus pointing to strong, potentialdependent immobilization of the constituents of the EDL, where the immobilization is correlated with the strength of the electric field in the EDL. In addition, from our entropy values, we derive an apparent contradiction with experimentally determined temperature coefficients of the EDL capacitance, which implies a strongly varying activity of the ions participating in charging of the EDL with temperature.

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Section: Discussionmentioning

confidence: 96%

Entropy Changes upon Double Layer Charging at a (111)-Textured Au Film in Pure 1-Butyl-1-Methylpyrrolidinium Bis[(trifluoromethyl)sulfonyl]imide Ionic Liquid

et al. 2019

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“…The Gouy–Chapman–Stern (GCS) model is a classical EDL model that conceptualizes the EDL as a serial connection of a rigid Helmholtz plane, which corresponds to the plane of the closest approach of solvated ions, and the Gouy–Chapman diffuse layer. − Subsequent improvements over the GCS model take into account ion steric effects, ,, specific adsorption and chemisorption, ,,, solvent polarization effects that lower the dielectric permittivity of near-surface solvent layers, , and nonlocal short-range correlations that become increasingly nontrivial in concentrated solutions. ,, A commonality shared by GCS-like models is that they use a continuum description of the electrolyte region, which is essentially treated as a Coulombic fluid, while the metal is treated as a featureless boundary. If the metal is treated either as a constant-potential or as a constant-charge boundary, GCS-like models correspond to either a grand-canonical or a canonical ensemble.…”

Section: Introductionmentioning

confidence: 99%

Grand-Canonical Model of Electrochemical Double Layers from a Hybrid Density–Potential Functional

Huang

Chen

Eikerling

2021

J. Chem. Theory Comput.

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A hybrid density–potential functional of an electrochemical interface that encompasses major effects in the contacting metal and electrolyte phases is formulated. Variational analysis of this functional yields a grand-canonical model of the electrochemical double layer (EDL). Specifically, metal electrons are described using the Thomas–Fermi–Dirac–Wigner theory of an inhomogeneous electron gas. The electrolyte solution is treated classically at the mean-field level, taking into account electrostatic interactions, ion size effects, and nonlinear solvent polarization. The model uses parametrizable force relations to describe the short-range forces between metal cationic cores, metal electrons, and electrolyte ions and solvent molecules. Therefore, the gap between the metal skeleton and the electrolyte solution, key to properties of the EDL, varies consistently as a function of the electrode potential. Partial charge transfer in the presence of ion specific adsorption is described using an Anderson–Newns type theory. This model is parametrized with density functional theory calculations, compared with experimental data, and then employed to unravel several interfacial properties of fundamental significance in electrochemistry. In particular, a closer approach of the solution phase toward the metal surface, for example, caused by a stronger ion specific adsorption, decreases the potential of zero charge and elevates the double-layer capacitance curve. In addition, the ion specific adsorption can lead to surface depolarization of ions. The present model represents a viable framework to model (reactive) EDLs under the constant potential condition, which can be used to understand multifaceted EDL effects in electrocatalysis.

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“…Making the natural change of variable ξ ¼ Àer=α leads to the standard form of the confluent Heun equation [86,87]…”

Section: Coulomb Interactionmentioning

confidence: 99%

Zero‐Energy Vortices in Dirac Materials

Downing¹,

Portnoi²

2019

Physica Status Solidi (b)

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In this brief review, the problem of electrostatic confinement of massless Dirac particles is surveyed via a number of exactly solvable one‐ and two‐body models. By considering bound states at zero energy, a route to obtain truly discrete states of massless Dirac particles in scalar potentials is presented, circumventing the celebrated Klein tunneling phenomenon. It is also shown how the coupling of two ultrarelativistic particles can arise, and its implications for cutting‐edge experiments with two‐dimensional Dirac materials are discussed. Finally, an analytic solution of the two‐body Dirac–Kepler problem is reported, which may be envisaged to bring about a deeper understanding of critical charge and atomic collapse in mesoscopic Dirac systems.

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The Role of Ion–Ion Correlations for the Differential Capacitance of Ionic Liquids

Cited by 19 publications

References 56 publications

Entropy Changes upon Double Layer Charging at a (111)-Textured Au Film in Pure 1-Butyl-1-Methylpyrrolidinium Bis[(trifluoromethyl)sulfonyl]imide Ionic Liquid

Entropy Changes upon Double Layer Charging at a (111)-Textured Au Film in Pure 1-Butyl-1-Methylpyrrolidinium Bis[(trifluoromethyl)sulfonyl]imide Ionic Liquid

Grand-Canonical Model of Electrochemical Double Layers from a Hybrid Density–Potential Functional

Zero‐Energy Vortices in Dirac Materials

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