Transport in Proton Conductors for Fuel‐Cell Applications: Simulations, Elementary Reactions, and Phenomenology

Kreuer, Klaus‐Dieter; Paddison, Stephen J.; Spohr, Eckhard; Schuster, Michael

doi:10.1002/chin.200450274

Cited by 126 publications

(201 citation statements)

References 253 publications

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“…Another observation necessary to stress is the larger Mg 2+ /Na + mobility ratio in F9120 as compared with the ratios in the other two CEMs, this is in accordance with the fact that perfluorosulfonic CEMs have larger ionic channels in the membrane matrix when fully hydrated [49,50]. The F9120 membranes with Mg 2+ and Na + counter ions are in general more conductive than corresponding hydrocarbon-based CEMs (SPEEK and CMX).…”

Section: Membrane Conductivitysupporting

confidence: 56%

Ion mobility and partition determine the counter-ion selectivity of ion exchange membranes

Luo

Roghmans

Weßling

2020

Journal of Membrane Science

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Ion (perm)selectivity and conductivity are the two most essential properties of an ion exchange membrane, yet no quantitative relation between them has been suggested. In this work, the selectivity between two different counter-ions is correlated to the membrane conductivity. We show that the counter-ion selectivity measured by conventional electrodialysis (ED) can be expressed by the product of two parameters: (a) the mobility ratio between these two different counter-ions in the membrane and (b) their partition coefficient between the solution and the membrane. This is reminiscent of the classical solution-diffusion model. Via the counter-ion mobility in the membrane, the selectivity could be simply expressed with the membrane conductivity and dimensional swelling degree at pure counter-ion forms and at mixed counter-ion form when the membrane has been equilibrated with 1:1 equivalence ratio of the two counter-ions in the solution. This correlation is validated experimentally for the ion selectivity of K + /Na + in two commercial hydrocarbon-based cation exchange membranes (CEMs). For K + /Na + in a commercial perfluorosulfonic CEM, and for Mg 2+ /Na + in all the three types of CEMs, the correlation could predict the counter-ion partition very well; but there is an underestimation of the K + /Na + and Mg 2+ /Na + mobility ratios afforded by this correlation, which might be due to simplification of the cation activity coefficients in CEMs. This work offers a convenient method to decouple experimentally the effect of partition and mobility in controlling the membrane selectivity, and also proposes a new perspective to study the selectivity as well as conductivity of ion exchange membranes.

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Section: Membrane Conductivitysupporting

confidence: 56%

Ion mobility and partition determine the counter-ion selectivity of ion exchange membranes

Luo

Roghmans

Weßling

2020

Journal of Membrane Science

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“…1 A prototypical PEFC membrane consists of a phase-separated polymer with interconnected conductive, nanoscale, aqueous domains embedded in a nonconductive matrix that provides structural integrity and durability. [2][3][4] Interactions between appended charged polymer groups and aqueous counterions cause ion-transport behavior in the aqueous domains to differ from that in bulk aqueous solution. [3][4] To understand how molecular interactions among polymer, water, and ions at the nanoscale mediate transport at the macroscale, we formulate a multiscale mechanistic model for ion transport in fuel-cell membranes.…”

Section: Introductionmentioning

confidence: 99%

“…Unfavorable interactions between the hydrophilic sulfonate moiety and the hydrophobic backbone cause the polymer to phase separate into solid polymer bundles and an interconnected network of ionically conductive, hydrophilic domains or "pores." [2][3][4][5] Because the ionic conductivity of PFSA membranes increases drastically with water content, PEFC membranes typically operate under humidified conditions. 1 A wet environment leads to water absorption into the hydrophilic domains of the membrane with the subsequent water content described as the molar ratio of water per sulfonate site, λ (mole H 2 O/mole SO 3  ).…”

Section: Introductionmentioning

confidence: 99%

“…4 Because the sulfonate anions are immobilized by covalent bonds to the polymer matrix, electrolyte conduction through the membrane is accomplished by movement of aqueous cations. 3 The amount of absorbed water controls the degree to which the cation and the sulfonate group dissociate. 3,6 Figure 1a depicts a completely dry PFSA domain in which the sulfonate group and cation form an ionically bound ion pair.…”

Section: Introductionmentioning

confidence: 99%

“…3 The amount of absorbed water controls the degree to which the cation and the sulfonate group dissociate. 3,6 Figure 1a depicts a completely dry PFSA domain in which the sulfonate group and cation form an ionically bound ion pair. 3,[6][7] The proton exists as a hydronium cation since desorption of the constituent water molecule occurs only at extreme temperatures ( >200 °C).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Impact of Nano- and Mesoscales on Macroscopic Cation Conductivity in Perfluorinated-Sulfonic-Acid Membranes

Crothers

Radke

Weber³

2017

J. Phys. Chem. C

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A mean-field local-density theory is outlined for ion transport in perfluorinated-sulfonic-acid (PFSA) membranes. A theory of molecular-level interactions predict nanodomain and macroscale conductivity. The effects of solvation, dielectric saturation, dispersion forces, image charge, finite size, and confinement are included in a physically consistent 3D-model domain geometry. Probability-distribution profiles of aqueous cation concentration at the domain-scale are in agreement with atomistic simulations using no explicit fitting parameters. Measured conductivities of lithium-, sodium-, and proton-form membranes with equivalent weights of 1100, 1000, and 825 g/mol(SO3) validate the macroscale predictions using a single-value mesoscopic fitting parameter. Cation electrostatic interactions with pendant sulfonate groups are the largest source of migration resistance at the domainscale. Tortuosity of ionically conductive domains is the largest source of migration resistance at the macroscale. Our proposed transport model is consistent across multiple lengthscales. We provide a compelling methodology to guide material design and optimize performance in energy-conversion applications of PFSA membranes.

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Introduction and Overview: Protons, the Nonconformist Ions

Vona

Knauth

2012

Solid State Proton Conductors

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Transport in Proton Conductors for Fuel‐Cell Applications: Simulations, Elementary Reactions, and Phenomenology

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 126 publications

References 253 publications

Ion mobility and partition determine the counter-ion selectivity of ion exchange membranes

Ion mobility and partition determine the counter-ion selectivity of ion exchange membranes

Impact of Nano- and Mesoscales on Macroscopic Cation Conductivity in Perfluorinated-Sulfonic-Acid Membranes

Introduction and Overview: Protons, the Nonconformist Ions

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