Self-Consistent Description of Vapor-Liquid Interface in Ionic Fluids

Agrawal, Nikhil; Wang, Rui

doi:10.1103/physrevlett.129.228001

Cited by 11 publications

(19 citation statements)

References 42 publications

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“…For example, state-of-the-art theories do not predict overcharging for monovalent ions in aqueous solutions due to their weak 'physical' ion correlations, and any 'chemical' effects related to surface-specificity are commonly ignored. [6,31,32] Muscovite mica, a phyllosilicate mineral, is one of the most widely used substrates to study EDL structures due to its atomically flat basal plane with a well-defined surface charge of ~1 e À /A UC (A UC : area of the muscovite (001) unit cell, 46.72 Å 2 ). The cleaved surface is decorated with K + ions that can have short-range ordering, as observed by low-temperature noncontact atomic force microscopy (AFM) under ultra-high vacuum (UHV) conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The development of more realistic modifications of EDL theories for overcharging regimes is further complicated by the common disparity of ‘chemical’ and ‘physical’ literature. For example, state‐of‐the‐art theories do not predict overcharging for monovalent ions in aqueous solutions due to their weak ‘physical’ ion correlations, and any ‘chemical’ effects related to surface‐specificity are commonly ignored [6,31,32] …”

Section: Introductionmentioning

confidence: 99%

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Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb⁺ and Halides (Cl⁻, Br⁻, I⁻) at High Salinity

Neumann,

Lee,

Zhao

et al. 2023

ChemPhysChem

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Classical electric double layer (EDL) models have been widely used to describe ion distributions at charged solid‐water interfaces in dilute electrolytes. However, the chemistry of EDLs remains poorly constrained at high ionic strength where ion–ion correlations control non‐classical behavior such as overcharging, i.e., the accumulation of counter‐ions in amounts exceeding the substrate’s surface charge. Here, we provide direct experimental observations of correlated cation and anion distributions adsorbed at the muscovite (001)–aqueous electrolyte interface as a function of dissolved RbBr concentration ([RbBr] = 0.01–5.8 M) using resonant anomalous X‐ray reflectivity. Our results show alternating cation‐anion layers in the EDL when [RbBr] ≳ 100 mM, whose spatial extension (i.e., ~20 Å from the surface) far exceeds the dimension of the classical Stern layer. Comparison to RbCl and RbI electrolytes indicates that these behaviors are sensitive to the choice of co‐ion size. This new molecular‐scale understanding of the EDL structure during transition from classical to non‐classical regimes supports the development of realistic EDL models for technologies operating at high salinity such as water purification applications or modern electrochemical storage.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb⁺ and Halides (Cl⁻, Br⁻, I⁻) at High Salinity

Neumann,

Lee,

Zhao

et al. 2023

ChemPhysChem

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“…This dual-length scale issue can be circumvented using a decomposition scheme developed in our previous work. 63 The total correlation function is decoupled into the short-range contribution (subscript 'S') associated with the ion size and long-range contribution (subscript 'L') associated with the double-layer thickness as…”

Section: Decomposition Scheme For the Correlation Functionmentioning

confidence: 99%

“…Using the theory, we have successfully described the vapor-liquid interface in charged fluids. 63 Here, we first revisit the key equations of the modified Gaussian renormalized fluctuation theory. Then, we incorporate this theory into the transport equations 64 to investigate electrokinetic flows.…”

Section: Introductionmentioning

confidence: 99%

“…When charge inversion occurs, the correlations are significantly enhanced at the surface, making it an extremely challenging task to model the steep change in correlations from the surface to the bulk. Previously, we developed the modified Gaussian renormalized fluctuation theory, 62,63 which self‐consistently includes the spatially varying ion correlations and excluded volume effects in a unified framework. Using the theory, we have successfully described the vapor–liquid interface in charged fluids 63 .…”

Section: Introductionmentioning

confidence: 99%

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Non‐monotonic salt concentration dependence of inverted electrokinetic flow

Agrawal,

Wang

2023

AIChE Journal

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Modeling of electrokinetic flows is crucial to understand numerous phenomena associated with electrochemistry, biophysics, and colloidal science. Here, we incorporate the modified Gaussian renormalized fluctuation theory into transport equations for electrolyte solutions to study the ion‐correlation‐induced inversion of electrokinetic flows, also known as charge inversion. We are able to capture the non‐monotonic dependence of inverted streaming current and reversed electrophoretic mobility on salt concentration. By analyzing the double‐layer structure, we elucidate that this non‐monotonicity is a consequence of the competition between spatially varying ion correlations and the translational entropy of the ions. We find that for practical values of surface charge densities, the excluded volume effect does not play any significant role. In a significant improvement over existing theories, our theoretical predictions are in quantitative agreement with experimental measurements for charge inversion in trivalent salts.

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Ion-Specific Surface Tension of Aqueous Electrolyte Solutions: Analytical Insights from a Restricted Primitive Model

Xiao,

Zhou,

Jiang

2024

J. Chem. Theory Comput.

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The ion-specific surface tension of aqueous electrolyte solutions is of fundamental importance in physical chemistry, solution chemistry, electrochemistry, and biochemistry, yet it remains a challenge to be qualitatively predicted. In this work, an analytical theory of ion-specific surface tension is developed. By modeling the solution to a restricted primitive model (RPM), the surface tension increment of the electrolyte solution reduces to the surface tension of the RPM, which is further determined analytically by using the integral equation theory and the morphological thermodynamics theory. According to our formula, the surface tension increment of the electrolyte solution consists of a dominant and positive hard sphere contribution, which depends on the salt concentration, and a secondary electrostatic contribution, which depends on the inverse Debye length and the salt concentration. Our theory is applied to 1:1, 2:2, 1:2, 2:1, 3:1, and 3:2 electrolyte solutions with typical salt concentrations up to several mol/L and compared with experimental data. Without introducing any adjustable parameters, our theory leads to a good prediction of the surface tension increment of more than 50 kinds of aqueous solutions. Such a good agreement demonstrates the great potential of our theory for a fundamental understanding of specific ion effects in a variety of electrolyte solutions.

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Self-Consistent Description of Vapor-Liquid Interface in Ionic Fluids

Cited by 11 publications

References 42 publications

Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb⁺ and Halides (Cl⁻, Br⁻, I⁻) at High Salinity

Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb⁺ and Halides (Cl⁻, Br⁻, I⁻) at High Salinity

Non‐monotonic salt concentration dependence of inverted electrokinetic flow

Ion-Specific Surface Tension of Aqueous Electrolyte Solutions: Analytical Insights from a Restricted Primitive Model

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Self-Consistent Description of Vapor-Liquid Interface in Ionic Fluids

Cited by 11 publications

References 42 publications

Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb+ and Halides (Cl−, Br−, I−) at High Salinity

Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb+ and Halides (Cl−, Br−, I−) at High Salinity

Non‐monotonic salt concentration dependence of inverted electrokinetic flow

Ion-Specific Surface Tension of Aqueous Electrolyte Solutions: Analytical Insights from a Restricted Primitive Model

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Product

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Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb⁺ and Halides (Cl⁻, Br⁻, I⁻) at High Salinity

Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb⁺ and Halides (Cl⁻, Br⁻, I⁻) at High Salinity