Electrical Double Layers Close to Ionic Liquid–Solvent Demixing

Cruz, Carolina Abs da; Ciach, A.; Lomba, Enrique; Kondrat, Svyatoslav

doi:10.1021/acs.jpcc.8b09772

Cited by 35 publications

(56 citation statements)

References 65 publications

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“…It is well known that ǫ depends on temperature, particularly for polar solvents [33][34][35]. Nevertheless, we assume ǫ to be temperature-independent, and note that its temperature variation should not affect the results qualitatively, as pointed out in [30]. In addition, it is known that polarizability of solvent and of ions may play an important role in the structure and properties of electrical double layers [36][37][38][39][40][41].…”

Section: Modelmentioning

confidence: 96%

Effect of proximity to ionic liquid-solvent demixing on electrical double layers

Cruz

Kondrat

Lomba

et al. 2019

Journal of Molecular Liquids

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There is a growing interest in the properties of ionic liquids (ILs) and IL-solvent mixtures at metallic interfaces, particularly due to their applications in energy storage. The main focus so far has been on electrical double layers with ILs far from phase transitions. However, the systems in the vicinity of their phase transformations are known to exhibit some remarkable features, such as wetting transitions and capillary condensation. Herein, we develop a mean-field model suitable for the IL-solvent mixtures close to demixing, and combine it with the Carnahan-Starling (CS) and lattice-gas expressions for the excluded volume interactions. This model is then solved analytically, using perturbation expansion, and numerically. We demonstrate that, besides the well-known camel and bell-shaped capacitances, there is a bird-shaped capacitance, having three peaks as a function of voltage, which emerge due to the proximity to demixing. In addition, we find that the camel-shaped capacitance, which is a signature of dilute electrolytes, can appear at high IL densities for ionophobic electrodes. We also discuss the differences and implications arising from the CS and lattice-gas expressions in the context of our model.

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Section: Modelmentioning

confidence: 96%

Effect of proximity to ionic liquid-solvent demixing on electrical double layers

Cruz

Kondrat

Lomba

et al. 2019

Journal of Molecular Liquids

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“…The specific potential at which no charge is carried is called the potential of zero charge. This is a distinctive quantity for a given metal/solvent interface, and it is independent of the ions in the case in which there is no specific adsorption) and two symmetric maxima [ 35 ]. The camel-shaped capacitance is a signature of dilute electrolytes and has been extensively studied [ 49 , 52 , 53 , 54 , 55 , 59 , 112 , 113 , 114 , 115 ].…”

Section: Ionic Liquidsmentioning

confidence: 99%

“…On the other hand, if there are almost no voids or few solvent molecules, the counterions will start to accumulate at the electrode, and the EDL will get thicker. Consequently, in the case of large ionic density, the capacitance will take the bell shape, with a single maximum at the PZC [ 35 , 49 , 52 , 53 , 54 , 55 , 59 , 111 , 112 , 113 , 114 , 115 , 116 , 117 ].…”

Section: Ionic Liquidsmentioning

confidence: 99%

“…However, the specific interactions can play a very significant role as evidenced by the phase separation into IL-poor and IL-rich phases induced by these interactions [ 156 , 157 ]. The effect of the specific interactions on capacitance C (see Equation ( 3 )), charge Q (see Equation ( 4 )) and stored energy E (see Equation ( 6 )) was studied recently in [ 35 , 36 , 37 ], where the authors have considered a mixture of IL and neutral solvent confined by a slit-shaped mesopore, as shown in Figure 3 . Special attention was paid to the proximity of the phase transition.…”

Section: Effect Of Phase Separation On Electrochemical Properties Of mentioning

confidence: 99%

“…In particular, organic IL with a polar solvent like water can phase-separate at room temperature, and the critical point of this phase separation is of the order of 400 K. The studies of the phase separation in IL-solvent mixtures concerned mainly the bulk systems. The investigation of the effect of proximity to the demixing phase transition on electrochemical properties of confined IL-solvent mixtures has started only very recently [ 35 , 36 , 37 ].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Phase Transitions and Electrochemical Properties of Ionic Liquids and Ionic Liquid—Solvent Mixtures

Cruz

Ciach

2021

Molecules

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Recent advances in studies of ionic liquids (IL) and ionic liquid–solvent mixtures are reviewed. Selected experimental, simulation, and theoretical results for electrochemical, thermodynamical, and structural properties of IL and IL-solvent mixtures are described. Special attention is paid to phenomena that are not predicted by the classical theories of the electrical double layer or disagree strongly with these theories. We focus on structural properties, especially on distribution of ions near electrodes, on electrical double layer capacitance, on effects of confinement, including decay length of a dissjoining pressure between confinig plates, and on demixing phase transition. In particular, effects of the demixing phase transition on electrochemical properties of ionic liquid–solvent mixtures for different degrees of confinement are presented.

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In Situ Spectroelectrochemical Investigation of Potential‐Dependent Changes in an Amphiphilic Imidazolium‐Based Ionic Liquid Film on the Au(111) Electrode Surface

Sieling

Brand

2020

ChemElectroChem

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The stability of ionic liquids (ILs) at charged interfaces makes them very attractive in electrochemical applications. In this work, a Langmuir–Blodgett transfer is used to fabricate a monolayer of an amphiphilic 1‐methyl‐3‐octadecylimidazolium perchlorate IL on the Au(111) surface. The IL monolayer immersed in an aqueous electrolyte solution is very stable over a wide potential window. Polarization modulation infrared reflection absorption spectroscopy is used to monitor structural changes in the model of the electrical double layer of the IL in aqueous solution. The imidazolium cation is in direct contact with the Au(111) surface. The imidazolium ring adopts a rigid orientation, inclined toward the metal surface, in the monolayer on the Au(111) surface. The orientation of hydrocarbon chains responds to electric potentials. At low negative surface charge densities of the Au(111) electrode, the hydrocarbon chains in the amphiphilic cation have a large average tilt versus surface normal. A negative potential shift is accompanied by a reorientation of the hydrophobic hydrocarbon chains that adopt an up‐ward orientation, making the film permeable for counter‐ and/or co‐ions. This transition leads to the formation of an ordered, single‐component monolayer of the amphiphilic cation on the electrode surface.

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Electrical Double Layers Close to Ionic Liquid–Solvent Demixing

Cited by 35 publications

References 65 publications

Effect of proximity to ionic liquid-solvent demixing on electrical double layers

Effect of proximity to ionic liquid-solvent demixing on electrical double layers

Phase Transitions and Electrochemical Properties of Ionic Liquids and Ionic Liquid—Solvent Mixtures

In Situ Spectroelectrochemical Investigation of Potential‐Dependent Changes in an Amphiphilic Imidazolium‐Based Ionic Liquid Film on the Au(111) Electrode Surface

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