Modification of Nafion Membranes: Tailoring Properties for Function

Leddy, Johna

doi:10.1021/bk-2015-1213.ch006

Cited by 13 publications

(13 citation statements)

References 40 publications

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“…For the calculation of the particle size distribution, we assume an irregular particle shape and a refractive index similar to Nafion (viz., 1.34). 30…”

Section: Fuel Cell Testing-mentioning

confidence: 99%

Ink Solvent Dependence of the Ionomer Distribution in the Catalyst Layer of a PEMFC

Orfanidi

Rheinländer

Schulte

et al. 2018

J. Electrochem. Soc.

115

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This study examines the effect of ink composition on the ionomer distribution in the catalyst layer of membrane electrode assemblies (MEA) prepared by decal transfer. We combine both structural and electrochemical characterization techniques to investigate the influence of the ionomer distribution on MEA performance determined by 50 cm 2 active area single-cell proton exchange membrane (PEM) fuel cell measurements. Cathodic catalyst layers were prepared from inks with different alcohols (1-propanol or 2-propanol) and varying water content (16-65 wt% H 2 O). The H 2 /air performance of cathode catalyst layers prepared from the different inks with 700 EW ionomer differed drastically, particularly under wet operating conditions, whereby the best performance was obtained for an ink based on 16 wt% H 2 O in 1-propanol. This was successfully correlated with the observation of ionomer patches at the cathode electrode surface (i.e., the surface facing the diffusion medium) determined by scanning electron microscopy (SEM), with N 2 adsorption analysis of the electrodes using a QSDFT model, and with dynamic light scattering data of ionomer/solvent mixtures. No correlation could be obtained between H 2 /air performance and the proton conductivity of the cathodes obtained by electrochemical impedance spectroscopy, and a model to rationalize this behavior will be proposed.

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“…For the calculation of the particle size distribution, we assume an irregular particle shape and a refractive index similar to Nafion (viz., 1.34). 30…”

Section: Fuel Cell Testing-mentioning

confidence: 99%

Ink Solvent Dependence of the Ionomer Distribution in the Catalyst Layer of a PEMFC

Orfanidi

Rheinländer

Schulte

et al. 2018

J. Electrochem. Soc.

115

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“…27 Based on M(bpy) z+ 3 molar volume and Nafion water content, zc * f is less than the sulfonate concentration. 15 Density and equivalent weight estimate sulfonate concentration in the hydrated domains of Nafion. The limited volume of the hydrated domains precludes charge neutralization of sulfonate anions by M(bpy) Table I are sussed based on these concentrations.…”

Section: Values Inmentioning

confidence: 99%

“…Density (water content) and equivalent weight set concentration of sulfonates and M(bpy) z+ 3 that will fit in the hydrated volume. 15 Estimates, reported as molar densities (M) and denoted N * , are developed as summarized in Table III.…”

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confidence: 99%

Electron Hopping of Tris (2,2^′-bipyridyl) Transition Metal Complexes M(bpy)^2/3₃in Nafion

Gellett

Knoche

Rathuwadu

et al. 2016

J. Electrochem. Soc.

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Voltammetric currents of transition metal complexes in films on electrodes increase with electron self exchange (hopping) rate k11. In films, diffusion coefficients Df∝k11c*f, where k11 sets frequency of electron hopping attempts and c*f film concentration sets distance between probes. Cyclic voltammetry of Nafion films on electrodes for six probes, tris(2,2′-bipyridyl) complexes, M(bpy)z +3 where Mz + is Ru2+, Os2+, Fe2+, Cr3+, Co3+, and Co2+, demonstrates Df varies linearly with kH2O11, literature k11 measured in water. From density of Ru(bpy)2 +3 exchanged Nafion 1.95 g/cm3 and nominal equivalent weight 1100, geometry establishes volume limited, z-independent c*f for all M(bpy)z +3. For concentrations of Ru(bpy)2 +3 in HNO3 where either Ru(bpy)2 +3: HNO3 ratio is fixed or Ru(bpy)2 +3 is 1 mM and HNO3 varies, c*f is statistically invariant. Based on aqueous titrations and dielectric constant sufficient to support ions, electron hopping is confined to hydrated domains of Nafion. From c*f, k11 in Nafion kNaf11 is estimated as k11Naf=0.010k11H2O, consistent with higher ion concentration in Nafion. Measured Df is 2 × 10− 9 cm2/s for Ru(bpy)2 +3 and Os(bpy)2 +3; 1 × 10− 10 cm2/s for Fe(bpy)2 +3 and Cr(bpy)3 +3; and 1.5 × 10− 12 and 5 × 10− 12 cm2/s for Co(bpy)2 +3 and Co(bpy)3 +3. For physical diffusion Dp ≲ 10− 12 cm2/s. A self consistent view of M(bpy)z +3 self exchange in Nafion is outlined. For Os(bpy)2/33, kH2O11 ≈ 4.5 × 108/Ms.

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“…Nafion ® (CAS number 66796-30-3) is a well-known commercial ionomer membrane material 24,25 with applications in fuel cells, 26 in catalysis, 27 and in electrolysers. 28 Nafion ® selfassembles into a "channel structure" 29,30 that allows cation transport through sulfonate-lined hydrophilic channels ( Figure 1) within a hydrophobic fluorocarbon matrix.…”

Section: Introductionmentioning

confidence: 99%

A Cationic Diode Based on Asymmetric Nafion Film Deposits

Madrid

Aaronson

et al. 2017

ACS Appl. Mater. Interfaces

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A thin film of Nafion, of approximately 5 μm thickness, asymmetrically deposited onto a 6 μm thick film of poly(ethylene terephthalate) (PET) fabricated with a 5, 10, 20, or 40 μm microhole, is shown to exhibit prominent ionic diode behavior involving cation charge carrier ("cationic diode"). The phenomenon is characterized via voltammetric, chronoamperometric, and impedance methods. Phenomenologically, current rectification effects are comparable to those observed in nanocone devices where space-charge layer effects dominate. However, for microhole diodes a resistive, a limiting, and an overlimiting potential domain can be identified and concentration polarization in solution is shown to dominate in the closed state.

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Modification of Nafion Membranes: Tailoring Properties for Function

Cited by 13 publications

References 40 publications

Ink Solvent Dependence of the Ionomer Distribution in the Catalyst Layer of a PEMFC

Ink Solvent Dependence of the Ionomer Distribution in the Catalyst Layer of a PEMFC

Electron Hopping of Tris (2,2^′-bipyridyl) Transition Metal Complexes M(bpy)^2/3₃in Nafion

A Cationic Diode Based on Asymmetric Nafion Film Deposits

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Modification of Nafion Membranes: Tailoring Properties for Function

Cited by 13 publications

References 40 publications

Ink Solvent Dependence of the Ionomer Distribution in the Catalyst Layer of a PEMFC

Ink Solvent Dependence of the Ionomer Distribution in the Catalyst Layer of a PEMFC

Electron Hopping of Tris (2,2′-bipyridyl) Transition Metal Complexes M(bpy)2/33in Nafion

A Cationic Diode Based on Asymmetric Nafion Film Deposits

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Electron Hopping of Tris (2,2^′-bipyridyl) Transition Metal Complexes M(bpy)^2/3₃in Nafion