Electrokinetic Measurements of Thin Nafion Films

Barbati, Alexander C.; Kirby, Brian J.

doi:10.1021/la403735g

Cited by 16 publications

(15 citation statements)

References 60 publications

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“…27 This discrepancy motivated us to reproduce these conductivity measurements. The mobility of Li + ions in an electrolyte solution consisting of LiPF 6 in ACN is approximately six times higher than in a solution of LiPF 6 in DMSO. 28,29 Therefore, if the measurements of Doyle et al are correct, the conductivity of lithium in an electrolyte is not strongly correlated with the conductivity of lithiated Nafion containing the same solvent.…”

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confidence: 86%

Molecular Dynamics Modeling of the Conductivity of Lithiated Nafion Containing Nonaqueous Solvents

Burlatsky

Darling

Новиков

et al. 2016

J. Electrochem. Soc.

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We use molecular dynamics to predict the ionic conductivities of lithiated Nafion perfluorinated ionomeric membranes swelled in dimethyl sulfoxide (DMSO) and acetonitrile (ACN). The experimental conductivity of lithiated Nafion swollen with DMSO is two orders of magnitude higher than with ACN. Conversely, the mobility of Li + ions in a solution of LiPF 6 in ACN is approximately six times higher than in DMSO. In this work, we demonstrate that the ionic conductivity of Nafion is substantially governed by the concentration of free Li + ions, i.e. by the degree of dissociation of the Li + and SO 3 − pairs, and that the inherent mobility of Nafion is a cation-exchange membrane that has been extensively studied and used in aqueous electrochemical systems. In this work, we seek to understand the applicability of Nafion to flow batteries that use nonaqueous solvents and lithium salts. A flow battery is an electrochemical device that stores and releases energy by oxidizing and reducing redox molecules that remain dissolved in electrolytes. The active molecules are stored in external vessels and pumped to reactors to charge or discharge the battery. This arrangement provides a separation of energy and power that is absent from conventional enclosed batteries like lead acid. The all-vanadium redox flow battery, for example, is an aqueous system that relies on the V 2+ /V 3+ and VO 2+ /VO 2 + couples at the negative and positive electrodes and H + as the primary charge carrier. Nonaqueous electrolytes are being considered for redox flow batteries to enable electrochemical couples with potential differences substantially exceeding the aqueous stability limit of 1.23 V, and, consequently, increase energy density. Two key considerations in reactor design are power density and Coulombic efficiency. The membrane must possess high ionic conductivity, low electronic conductivity, and low permeability of active species (the various vanadium ions in the aqueous example mentioned above) to simultaneously achieve high area-specific power density and high Coulombic efficiency. In this work, Li + is the primary charge carrier, and the unspecified active species are assumed to be absent from the membrane. Future work could examine the behavior of active molecules in lithiated membranes containing different solvents, with a specific focus on the charge on the active molecule.Many experimental 1-9 and numerical 10-21 works discussing ion diffusion and conductivity in Nafion swollen with water have been published during the past two decades. The dependence of conductivity on water content and temperature is well understood. Furthermore, a number of theoretical 22,23 and experimental works consider Nafion swollen with methanol or water/methanol mixtures in the context of direct methanol fuel cells. 24,25 It has been demonstrated that the diffusion coefficients of water, methanol, and hydronium decrease with increasing methanol concentration. There have been far fewer studies on Nafion containing solvents other than water and methanol. A nota...

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confidence: 86%

Molecular Dynamics Modeling of the Conductivity of Lithiated Nafion Containing Nonaqueous Solvents

Burlatsky

Darling

Новиков

et al. 2016

J. Electrochem. Soc.

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“…Electrokinetic effects-based techniques are often used to measure physical and chemical properties of porous and charged layers, because they reveal information on the physicochemical state of an interface in contact with an electrolytic solution. Thus, streaming potential measurements has been used to investigate the surface characteristics of ultrafiltration membranes, and to determine the interactions between the foulant and the membrane [ 2 , 3 ].…”

Section: Introductionmentioning

confidence: 99%

Electro-Osmotic Behavior of Polymeric Cation-Exchange Membranes in Ethanol-Water Solutions

Barragán

Villaluenga

Morales-Villarejo

et al. 2020

Entropy

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The aim of this work is to apply linear non-equilibrium thermodynamics to study the electrokinetic properties of three cation-exchange membranes of different structures in ethanol-water electrolyte solutions. To this end, liquid uptake and electro-osmotic permeability were estimated with potassium chloride ethanol-water solutions with different ethanol proportions as solvent. Current–voltage curves were also measured for each membrane system to estimate the energy dissipation due to the Joule effect. Considering the Onsager reciprocity relations, the streaming potential coefficient was discussed in terms of ethanol content of the solutions and the membrane structure. The results showed that more porous heterogeneous membrane presented lower values of liquid uptake and streaming potential coefficient with increasing ethanol content. Denser homogeneous membrane showed higher values for both, solvent uptake and streaming coefficient for intermediate content of ethanol.

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“…Electrokinetic techniques are often implemented to characterize these porous and charged layers [9]. Streaming current [10,11], streaming potential [12,13], and conductivity [13][14][15] measurements have all been performed to extract information on the state of the interface in these systems. These experimental efforts require analytical [16][17][18][19][20][21][22] and/or numerical [23][24][25] frameworks through which the experimental data is analyzed and interpreted.…”

Section: Introductionmentioning

confidence: 99%

Surface conductivity in electrokinetic systems with porous and charged interfaces: Analytical approximations and numerical results

Barbati

Kirby

2016

Electrophoresis

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We derive an approximate analytical representation of the conductivity for a 1D system with porous and charged layers grafted onto parallel plates. Our theory improves on prior work by developing approximate analytical expressions applicable over an arbitrary range of potentials, both large and small as compared to the thermal voltage (RTF). Further, we describe these results in a framework of simplifying nondimensional parameters, indicating the relative dominance of various physicochemical processes. We demonstrate the efficacy of our approximate expression with comparisons to numerical representations of the exact analytical conductivity. Finally, we utilize this conductivity expression, in concert with other components of the electrokinetic coupling matrix, to describe the streaming potential and electroviscous effect in systems with porous and charged layers.

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Electrokinetic Measurements of Thin Nafion Films

Cited by 16 publications

References 60 publications

Molecular Dynamics Modeling of the Conductivity of Lithiated Nafion Containing Nonaqueous Solvents

Molecular Dynamics Modeling of the Conductivity of Lithiated Nafion Containing Nonaqueous Solvents

Electro-Osmotic Behavior of Polymeric Cation-Exchange Membranes in Ethanol-Water Solutions

Surface conductivity in electrokinetic systems with porous and charged interfaces: Analytical approximations and numerical results

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