The influence of the cationic form and degree of hydration on the structure of Nafion™

Negro, Enrico; Vittadello, Michele; Vezzù, Keti; Paddison, Stephen J.; Noto, Vito Di

doi:10.1016/j.ssi.2013.09.017

Cited by 41 publications

(97 citation statements)

References 34 publications

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“…The MIR region has been already highly documented in Nafion and other PFSA membranes, 10,[16][17][18][19][20][21][22]43 but the FIR spectra were never reported in the literature. 3D plots of a typical hydration sequence from dry to 100%RH are shown in Figure 1 The 3D plots evidence several distinct mechanisms identified through the appearance or disappearance of characteristic bands in both the FIR and MIR.…”

Section: Resultsmentioning

confidence: 99%

“…The attribution of this band is still controversial. 22 3.3. Low Water Content Ionized State, λ = 1 to 3: Hydronium-Water-Sulfonic Charges Interactions, and High Water Content λ = 3 to 14.…”

Section: Resultsmentioning

confidence: 99%

“…Since the pioneering studies of Falk 16 and Ostrowska, 17 the efforts have been focused on attributing backbone, side-chains, and water modes. With the same aim, further infrared studies of Nafion under controlled water vapor pressure were performed by Di Noto, 21,22 Iwamoto, 20 and Laporta. 19 Buzzoni 18 also reported a comparison of Nafion membrane with acids of similar strength.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of Ionization, Hydration, and Intermolecular H-Bonding in Proton Conducting Nanostructured Ionomers

et al. 2014

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Water−ions interactions and spatial confinement largely determine the properties of hydrogen-bonded nanomaterials. Hydrated acidic polymers possess outstanding proton-conducting properties due to the interconnected H-bond network that forms inside hydrophilic channels upon water loading. We report here the first far-infrared (FIR) coupled to mid-infrared (MIR) kinetics study of the hydration mechanism in benchmark perfluorinated sulfonic acid (PFSA) membranes, e.g., Nafion. The hydration process was followed in situ, starting from a well-prepared dry state, within unprecedented continuous control of the relative humidity. A step-by-step mechanism involving two hydration thresholds, at respectively λ = 1 and λ = 3 water molecules per ionic group, is assessed. The molecular environment of water molecules, protonic species, and polar groups are thoroughly described along the various states of the polymer membrane, i.e., dry (λ ≈ 0), fully ionized (λ = 1), interacting (λ = 1−3), and H-bonded (λ > 3). This unique extended set of IR data provides a comprehensive picture of the complex chemical transformations upon loading water into proton-conducting membranes, giving insights into the state of confined water in charged nanochannels and its role in driving key functional properties as ionic conduction.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanism of Ionization, Hydration, and Intermolecular H-Bonding in Proton Conducting Nanostructured Ionomers

et al. 2014

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“…The structural and dynamical properties of protons and water confined in the PFSA polymers have been extensively studied by numerical simulations [15][16][17] and infrared spectroscopy [18][19][20][21][22][23]. The short-side chain Aquivion was shown to perform better in fuel cells, with respect to the reference Nafion [11].…”

Section: Introductionmentioning

confidence: 99%

QENS investigation of proton confined motions in hydrated perfluorinated sulfonic membranes and self-assembled surfactants

Berrod

Lyonnard

Guillermo

et al. 2015

EPJ Web of Conferences

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Abstract. We report on QuasiElastic Neutron Scattering (QENS) investigations of the dynamics of protons and water molecules confined in nanostructured perfluorinated sulfonic acid (PFSA) materials, namely a commercial Aquivion membrane and the perfluorooctane sulfonic acid (PFOS) surfactant. The former is used as electrolyte in low-temperature fuel cells, while the latter forms mesomorphous self-assembled phases in water. The dynamics was investigated as a function of the hydration level, in a wide time range by combining time-of-flight and backscattering incoherent QENS experiments. Analysis of the quasielastic broadening revealed for both systems the existence of localized translational diffusive motions, fast rotational motions and slow hopping of protons in the vicinity of the sulfonic charges. The characteristic times and diffusion coefficients have been found to exhibit a very similar behaviour in both membrane and surfactant structures. Our study provides a comprehensive picture of the proton motion mechanisms and the dynamics of confined water in model and real PFSA nanostructures.

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“…This approach is then very different from those developed for membranes made from a single ionomer in which one polymer has to combine all the required properties. In that latter case, the presence of polarizable groups in various amounts to suit the conduction properties can more directly and dramatically affect the other properties such as swelling, gas permeability or mechanical properties [ 14,15 ]. In order to mimic Nafion ® micro or nano structure, IPN architecture combining the polyelectrolyte network with a neutral fluorinated one appears as an interesting strategy.…”

Section: Introductionmentioning

confidence: 99%

Hydrophobic networks for advanced proton conducting membrane: Synthesis, transport properties and chemical stability

Magana

Festin

Fumagalli

et al. 2015

Journal of Membrane Science

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The influence of the cationic form and degree of hydration on the structure of Nafion™

Cited by 41 publications

References 34 publications

Mechanism of Ionization, Hydration, and Intermolecular H-Bonding in Proton Conducting Nanostructured Ionomers

Mechanism of Ionization, Hydration, and Intermolecular H-Bonding in Proton Conducting Nanostructured Ionomers

QENS investigation of proton confined motions in hydrated perfluorinated sulfonic membranes and self-assembled surfactants

Hydrophobic networks for advanced proton conducting membrane: Synthesis, transport properties and chemical stability

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