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Überrück T, Neudert O, Kreuer KD, Blümich B, Granwehr J, Stapf S, Han S. Effect of nitroxide spin probes on the transport properties of Nafion membranes. Phys Chem Chem Phys 2018; 20:26660-26674. [PMID: 30320331 DOI: 10.1039/c8cp04607g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Nafion is the most common material used as a proton exchange membrane in fuel cells. Yet, details of the transport pathways for protons and water in the inner membrane are still under debate. Overhauser Dynamic Nuclear Polarization (ODNP) has proven to be a useful tool for probing hydration dynamics and interactions within 5-8 Å of protein and soft material surfaces. Recently it was suggested that ODNP can also be applied to analyze surface water dynamics along Nafion's inner membrane. Here we interrogate the viability of this method for Nafion by carrying out a series of measurements relying on 1H nuclear magnetic resonance (NMR) relaxometry and diffusometry experiments with and without ODNP hyperpolarization, accompanied by other complementary characterization methods including small angle X-ray scattering (SAXS), thermal gravimetric analysis (TGA) of hydration, and proton conductivity by AC impedance spectroscopy. Our comprehensive study shows that commonly used paramagnetic spin probes-here, stable nitroxide radicals-for ODNP, as well as their diamagnetic analogues, reduce the inner membrane surface hydrophilicity, depending on the location and concentration of the spin probe. This heavily reduces the hydration of Nafion, hence increases the tortuosity of the inner membrane morphology and/or increases the activiation barrier for water transport, and consequently impedes water diffusion, transport, and proton conductivity.
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Affiliation(s)
- Till Überrück
- RWTH Aachen University, Institut für Technische und Makromolekulare Chemie, Worringerweg 2, 52074 Aachen, Germany.
| | - Oliver Neudert
- Dept. Technical Physics II/Polymer Physics, University of Technology Ilmenau, 98684 Ilmenau, Germany and GMBU e.V., Erich-Neuß-Weg 5, 06120 Halle (Saale), Germany
| | - Klaus-Dieter Kreuer
- Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Bernhard Blümich
- RWTH Aachen University, Institut für Technische und Makromolekulare Chemie, Worringerweg 2, 52074 Aachen, Germany.
| | - Josef Granwehr
- RWTH Aachen University, Institut für Technische und Makromolekulare Chemie, Worringerweg 2, 52074 Aachen, Germany. and Forschungszentrum Jülich, Institut für Energie- und Klimaforschung - Grundlagen der Elektrochemie (IEK-9), 52425 Jülich, Germany
| | - Siegfried Stapf
- Dept. Technical Physics II/Polymer Physics, University of Technology Ilmenau, 98684 Ilmenau, Germany
| | - Songi Han
- University of California Santa Barbara, Department of Chemistry and Biochemistry, Santa Barbara, CA 93106, USA
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Abstract
In this comprehensive review, recent progress and developments on perfluorinated sulfonic-acid (PFSA) membranes have been summarized on many key topics. Although quite well investigated for decades, PFSA ionomers' complex behavior, along with their key role in many emerging technologies, have presented significant scientific challenges but also helped create a unique cross-disciplinary research field to overcome such challenges. Research and progress on PFSAs, especially when considered with their applications, are at the forefront of bridging electrochemistry and polymer (physics), which have also opened up development of state-of-the-art in situ characterization techniques as well as multiphysics computation models. Topics reviewed stem from correlating the various physical (e.g., mechanical) and transport properties with morphology and structure across time and length scales. In addition, topics of recent interest such as structure/transport correlations and modeling, composite PFSA membranes, degradation phenomena, and PFSA thin films are presented. Throughout, the impact of PFSA chemistry and side-chain is also discussed to present a broader perspective.
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Affiliation(s)
- Ahmet Kusoglu
- Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, MS70-108B, Berkeley, California 94720, United States
| | - Adam Z Weber
- Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, MS70-108B, Berkeley, California 94720, United States
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Fumagalli M, Lyonnard S, Prajapati G, Berrod Q, Porcar L, Guillermo A, Gebel G. Fast Water Diffusion and Long-Term Polymer Reorganization during Nafion Membrane Hydration Evidenced by Time-Resolved Small-Angle Neutron Scattering. J Phys Chem B 2015; 119:7068-76. [PMID: 25971732 DOI: 10.1021/acs.jpcb.5b01220] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report a small-angle neutron scattering study of liquid water sorption in Nafion membranes. The swelling of hydrophilic domains was measured on the nanoscale by combining in situ time-resolved and long-term static experiments, yielding kinetic curves recorded over an unprecedented time scale, from hundreds of milliseconds to several years. At low water content, typically below 5 water molecules per ionic group, a limited subdiffusive regime was observed and ascribed to nanoconfinement and local interactions between charged species and water molecules. Further ultrafast and thermally activated swelling due to massive liquid water sorption was observed and analyzed by using Fick's equation. The extracted mutual water diffusion coefficients are in good agreement with pulsed field gradient NMR self-diffusion coefficient values, evidencing a water diffusion-driven process due to concentration gradients within the Nafion membrane. Finally, after completion of the ultrafast regime, the kinetic swelling curves exhibit a remarkable long-term behavior scaling as the logarithm of time, showing that the polymer membrane can continuously accommodate additional water molecules upon hydration stress. The present nanoscale kinetics results provide insights into the vapor-versus-liquid sorption mechanisms, the nanostructure of Nafion, and the role of polymer reorganization modes, highlighting that the membrane can never reach a steady state.
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Affiliation(s)
- M Fumagalli
- †Université Grenoble Alpes, CNRS/CEA-INAC-SPrAM, F-38000 Grenoble, France
| | - S Lyonnard
- †Université Grenoble Alpes, CNRS/CEA-INAC-SPrAM, F-38000 Grenoble, France
| | - G Prajapati
- †Université Grenoble Alpes, CNRS/CEA-INAC-SPrAM, F-38000 Grenoble, France
| | - Q Berrod
- †Université Grenoble Alpes, CNRS/CEA-INAC-SPrAM, F-38000 Grenoble, France
| | - L Porcar
- ‡Institut Laue Langevin, BP 156, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France
| | - A Guillermo
- †Université Grenoble Alpes, CNRS/CEA-INAC-SPrAM, F-38000 Grenoble, France
| | - G Gebel
- §Université Grenoble Alpes, CEA Liten DTNM, F-38000 Grenoble, France
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Fechete R, Demco DE, Zhu X, Tillmann W, Möller M. Water states and dynamics in perfluorinated ionomer membranes by 1H one- and two-dimensional NMR spectroscopy, relaxometry, and diffusometry. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.02.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Klein M, Perrin JC, Leclerc S, Guendouz L, Dillet J, Lottin O. Anisotropy of Water Self-Diffusion in a Nafion Membrane under Traction. Macromolecules 2013. [DOI: 10.1021/ma401511t] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Mathieu Klein
- Université
de Lorraine, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
- CNRS, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
| | - Jean-Christophe Perrin
- Université
de Lorraine, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
- CNRS, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
| | - Sébastien Leclerc
- Université
de Lorraine, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
- CNRS, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
| | - Laouès Guendouz
- Institut
Jean-Lamour, UMR 7198, CNRS, Université de Lorraine, Vandoeuvre-lès-Nancy, F- 54500, France
| | - Jérôme Dillet
- Université
de Lorraine, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
- CNRS, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
| | - Olivier Lottin
- Université
de Lorraine, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
- CNRS, LEMTA, UMR7563, Vandoeuvre-lès-Nancy, F-54500, France
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Lee SM, Han OH. Hot-Pressing Effects on Polymer Electrolyte Membrane Investigated by2H NMR Spectroscopy. B KOREAN CHEM SOC 2013. [DOI: 10.5012/bkcs.2013.34.2.510] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Muncaci S, Mattea C, Stapf S, Ardelean I. Frequency-dependent NMR relaxation of liquids confined inside porous media containing an increased amount of magnetic impurities. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2013; 51:123-128. [PMID: 23303718 DOI: 10.1002/mrc.3924] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 11/13/2012] [Accepted: 12/18/2012] [Indexed: 06/01/2023]
Abstract
Frequency-dependent NMR relaxation studies have been carried out on water (polar) and cyclohexane (nonpolar) molecules confined inside porous ceramics containing variable amounts of iron oxide (III). The porous ceramics were prepared by compression of powders mixed with iron oxide followed by thermal treatment. The pore size distribution was estimated using a technique based on diffusion in internal fields that exposed a narrow distribution of macropore sizes with an average pore dimension independent of iron oxide content. The relaxation dispersion curves were obtained at room temperature using a fast field cycling NMR instrument. They display an increase of the relaxation rate proportional to the iron oxide concentration. This behavior is more prominent at low Larmor frequencies and is independent of the polar character of the confined molecules. The results reported here can be fitted well with a relaxation model considering exchange between molecules in the close vicinity of the paramagnetic centers located in the surface and bulk-like molecules inside the pores. This model allows the extraction of the transverse diffusional correlation time that can be related to the polar character of the confined molecules.
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Affiliation(s)
- Sergiu Muncaci
- Technical University of Cluj-Napoca, Department of Physics, Cluj-Napoca, Romania
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Steiner E, Bouguet-Bonnet S, Blin JL, Canet D. Water behavior in mesoporous materials as studied by NMR relaxometry. J Phys Chem A 2011; 115:9941-6. [PMID: 21793571 DOI: 10.1021/jp205456g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Water in mesoporous materials possessing a two-dimensional hexagonal structure has been studied by the variation of its NMR longitudinal relaxation time T(1) as a function of the static magnetic field value, or equivalently of the NMR measurement frequency. This technique, dubbed relaxometry, has been applied from 5 kHz (measurement frequency) up to 400 MHz with various instruments including a variable-field spectrometer operating between 8 and 90 MHz. Moreover, the range 0-5 kHz could be investigated by transverse relaxation, T(2) denoting the corresponding relaxation time, and relaxation in the rotating frame, T(1ρ) denoting the corresponding relaxation time. Measurements of proton relaxation rates (inverse of relaxation times) have been performed with H(2)O and HOD (residual protons of heavy water) at water volumes of 80%, 60%, and 40% relative to the porous volume. Comparison between H(2)O and HOD shows clearly that, above 1 MHz where both sets of data are superposed, relaxation is purely intermolecular and due to paramagnetic relaxation (dipolar interactions of water protons with unpaired electrons of paramagnetic entities). Below 1 MHz, it is possible to subtract the intermolecular contribution (given by HOD data) from H(2)O data so that one is left with intramolecular relaxation which is solely due to water reorientational motions. The analysis of these low-frequency data (in terms of Lorentzian functions) reveals two types of water within the pores: one interacting strongly with the surface and the other corresponding to a second layer. High-frequency data, which arise from paramagnetic relaxation, exhibit again two types of water. Due to their correlation times, one type is assigned to relatively free water within the pores while the other type corresponds to bulk (interparticular) water. Their proportions, given as a function of the volume fraction, are consistent with the above assignments.
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Affiliation(s)
- Emilie Steiner
- Méthodologie RMN (CRM2, UMR 7036 CNRS), Nancy-Université, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex, France
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Neves LA, Sebastião PJ, Coelhoso IM, Crespo JG. Proton NMR relaxometry study of Nafion membranes modified with ionic liquid cations. J Phys Chem B 2011; 115:8713-23. [PMID: 21678948 DOI: 10.1021/jp111238m] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proton nuclear magnetic resonance (NMR) relaxometry was used to study the ionic mobility and levels of confinement within Nafion membranes modified by incorporation of selected ionic liquid (IL) cations. These studies were performed aiming at understanding the effect of using different types of ionic liquid cations, and their degree of incorporation, in the values of the spin-lattice relaxation times (T(1)) obtained at different values of frequency and thus detect the influence of confinement level on the ions mobility. The frequency dependence of the proton spin-lattice relaxation rate, R(1) = 1/T(1), for the modified Nafion/IL cation membranes was compared with that obtained for an unmodified Nafion membrane, allowing for distinguishing different contributions of the motions of the molecules depending on the frequency tested. The experimental R(1) results were analyzed in terms of models that consider the sum of the most effective relaxation contributions, to estimate the translational self-diffusion coefficient of the moving molecular species in the modified membranes. The stability of these membranes with temperature in terms of the spin-lattice relaxation was compared with results obtained by thermogravimetric analysis.
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Affiliation(s)
- Luísa A Neves
- REQUIMTE/CQFB, FCT, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
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Kim YS, Pivovar BS. Moving Beyond Mass-Based Parameters for Conductivity Analysis of Sulfonated Polymers. Annu Rev Chem Biomol Eng 2010; 1:123-48. [DOI: 10.1146/annurev-chembioeng-073009-101309] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The proton conductivity of polymer electrolytes is critical for fuel cells and has therefore been studied in significant detail. The conductivity of sulfonated polymers has been linked to material characteristics to elucidate trends. Mass-based measurements based on water uptake and ion exchange capacity are two of the most common material characteristics used to make comparisons between polymer electrolytes, but they have significant limitations when correlated to proton conductivity. These limitations arise in part because different polymers can have significantly different densities and because conduction occurs over length scales more appropriately represented by volume measurements rather than mass. Herein we establish and review volume-related parameters that can be used to compare the proton conductivity of different polymer electrolytes. Morphological effects on proton conductivity are also considered. Finally, the impact of these phenomena on designing next-generation sulfonated polymers for polymer electrolyte membrane fuel cells is discussed.
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Affiliation(s)
- Yu Seung Kim
- Sensors and Electrochemical Devices, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
| | - Bryan S. Pivovar
- Hydrogen Technologies and Systems Center, National Renewable Energy Laboratory, Golden, Colorado 80401
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