An ab initio study of the primary hydration and proton transfer of CF3SO3H and CF3O(CF2)2SO3H: Effects of the hybrid functional and inclusion of diffuse functions

Wang, Chen; Clark, J. R.; Kumar, Milan; Paddison, Stephen J.

doi:10.1016/j.ssi.2011.07.002

Cited by 60 publications

(81 citation statements)

References 64 publications

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“…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%

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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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Section: Introductionmentioning

confidence: 99%

“…7 Figure 1c depicts water completely solvating the ions at higher water contents allowing complete ion dissociation. 3,[6][7] Figure 1. Depiction of the cation center of charge (+) and water dipole (⇸) distributions around a pendant sulfonate group ().…”

Section: Introductionmentioning

confidence: 99%

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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“…5,13,[26][27][28][31][32][33] Vibrational spectroscopy and the theoretical analysis of vibrational spectral properties provide an excellent tool to probe the interactions of water molecules confined in membranes. 13,16 Falk et al 14,15 discovered that the IR spectrum of hydrated Nafion membranes featured a very broad peak around 3500 cm -1 -3200 cm -1 , typical of bulk water spectra, but in addition to the broad peak were a few sharp peaks around 3600 cm -1 and 3700 cm -1 , not characteristic of bulk water.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure and Vibrational Mode Study of Nafion Membrane Interfacial Water Interactions

Kabrane

Aquino

2014

J. Phys. Chem. A

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The structural, energetic, and mid-infrared spectral properties of water clusters interacting with a model perfluorosulfonate (Nafion) ionomer segment have been investigated by means of quantum chemical calculations. Density functional theory calculations were conducted to model interfacial water condensed in pores and channels of Nafion and helped shedding light on the structural and vibrational properties of hydrated Nafion membranes. The computational models consisted of a sodium counterion, the Nafion ionomer, and a cluster of water molecules positioned in three different regions of the ionomer. The orientations of the water molecules in the vicinity of the ionomer were examined to understand the appearance of O-H stretching bands that deviated from the typical bulk water values as well as the appearance of multiple free O-H stretching bands. The calculations revealed insights into the structure, orientation, and energetics of Nafion and water clusters in and around the membrane interface; the results show that hydrogen atoms at the water-ionomer interface hydrogen bond to the hydrophilic sulfonate group as well as to the hydrophobic fluorinated backbone.

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“…An increase in EW results in the larger sulfonate-sulfonate separation, and thus hinders proton transport through hydrophilic channels (Allahyarov and Taylor, 2011). Theoretical and computational analyses, such as molecular dynamics (MD) simulations and ab initio simulations, have been used extensively to investigate proton transport properties including electroosmosis in Nafion membranes and thin films (Feng et al, 2012, Feng and Voth, 2011, Jorn et al, 2012, Petersen and Voth, 2006, Petersen et al, 2005, Tse et al, 2013, Seeliger et al, 2005, Spohr et al, 2002, Cui et al, 2007, Jang et al, 2004, Wang et al, 2011a, Karo et al, 2010, Knox and Voth, 2010, Komarov et al, 2013, Spohr, 2007, Mabuchi and Tokumasu, 2014, Wescott et al, 2006, Tuckerman et al, 1995, Eikerling et al, 2008, Kornyshev and Spohr, 2009, Choe et al, 2008, Yan et al, 2008, Aochi et al, 2016, Kurihara et al, 2017. However, extensive simulations using ab initio methods for a larger number of atoms, where systems reproduce nanostructured Nafion morphology and water domains with reliable statistics, have been limited because of the high computational cost of such simulations.…”

Section: Introductionmentioning

confidence: 99%

Dependence of electroosmosis on polymer structure in proton exchange membranes

Mabuchi

Tokumasu

2017

Mechanical Engineering Journal

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Effects of polymer structure on the electroosmosis in proton exchange membranes (PEMs) have been investigated using a reactive molecular dynamics simulation. An anharmonic two-state empirical valence bond (aTS-EVB) model has been used to describe efficiently excess proton transport via the Grotthuss hopping mechanism. The electroosmotic drag coefficients (i.e., the number of water molecules transferred through the membrane per proton) has been evaluated directly in PEMs consisting of various equivalent weights (EWs). The electroosmotic drag coefficients from the MD simulations are in good agreement with the available experimental values at studied levels of hydration. It is shown that for low water contents the connectivity of the water clusters decreases with increasing EW, leading to a decrease in the electroosmotic drag coefficients. The proton and water mobility is also found to decrease with increasing EW because of the structural changes in the water cluster domains. The present simulations provide quantitative information about the direct link between electroosmosis and nanoscopic water domain structure in different polymer structures

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An ab initio study of the primary hydration and proton transfer of CF3SO3H and CF3O(CF2)2SO3H: Effects of the hybrid functional and inclusion of diffuse functions

Cited by 60 publications

References 64 publications

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

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

Electronic Structure and Vibrational Mode Study of Nafion Membrane Interfacial Water Interactions

Dependence of electroosmosis on polymer structure in proton exchange membranes

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