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Showing papers on "Nafion published in 1982"


Journal ArticleDOI
TL;DR: In this article, the electrochemical behavior of Ru(bpy),2+ (bpy = 2,2'-bipyridine) contained in 2-thick films of the perfluorosulfonate polymer Nafion on glassy carbon is described.
Abstract: The electrochemical behavior of Ru(bpy),2+ (bpy = 2,2'-bipyridine) contained in 2-"thick films of the perfluorosulfonate polymer Nafion on glassy carbon is described. The apparent diffusion coefficient, D, , for the 2+ and 3+ forms was determined by potential-step chronoamperometric measurements to be (5 & 2) X cm*s-l. Dapp for the 2+ form was independent of loading of R ~ ( b p y ) , ~ + in the film. The shapes of the cyclic voltammetric (current-potential) waves for the system were fit by digital simulation techniques with a model involving interactions between the electroactive groups as well as interconversions of different forms of the 2+ and 3+ species. Recent reports from this labora t~ry l -~ have described polymer electrodes based on the ion-containing polymer Nafion.4 Because (CF2 C Fz )I (C FC F21? I O-GF~) G C F ~ C F ~ SGCN:

340 citations


Journal ArticleDOI
TL;DR: In this paper, the mechanism of charge transport through Nafion polymers coated on glassy carbon electrodes and containing Cp2FeTMA+, R~(bpy),~+, and O~ (bpy,~+ ) is described.
Abstract: The mechanism of charge transport through Nafion polymers coated on glassy carbon electrodes and containing Cp2FeTMA+, R~(bpy),~+, and O~(bpy),~+ (where Cp2FeTMA+ is ((trimethylammonio)methyl)ferrocene, bpy = 2,2'-bipyridine) is described. The apparent diffusion coefficients, Dam,, of polymer modified electrodes, as measured by conventional electrochemical methods and which can include contributions from intermolecular electron transfer, are compared to the diffusion coefficients of actual mass transport of the electroactive species through the polymer, D,, as measured from the rate of permeation of the electroactive material. The results indicate that Dapp = D, for Cp2FeTMA+, Dapp 20, for Os(bpy),*+, and DaP4 = 15D, for Ru(bpy)t+. These results are discussed in terms of the Dahms-Ruff model, where the observed diffusional behavior is due to both physical diffusion of the electroactive species and an electron-transfer component that can contribute to the observed behavior. The contribution of the electron-exchange mechanism toward the value of Dapp decreases in the order of electroactive species, Ru(bpy),*+ >> O~(bpy),~+ 2 Cp2FeTMA+. A key question in the behavior of "polymer electrodes" (elec- trodes coated with a thin layer of polymer1-*) involves the mechanism of charge transport through the layers. The rate of charge transport frequently governs the rate of electrochemical and catalytic processes at such electrodes and has been the subject of numerous recent inve~tigations.~,~.~-" Charge can be trans- ported through the layer by electron transfer between redox centers, counterion diffusion, and diffusion of the electroactive species; the relative contribution of these effects is probably different for different kinds of polymer coatings.

323 citations


Journal ArticleDOI
TL;DR: In this article, the authors used metal plating to increase the adhesive strength of perfluorosulfonic acid polymer membranes (Dupont manufactured Nafion) for solid polymer electrolyte (SPE).

237 citations



Journal ArticleDOI
TL;DR: In this article, a perfluorinated carboxylate polymer film was measured and the self-diffusion coefficient was compared to those obtained for Nafion in terms of the ion clustered morphology of the two materials.
Abstract: Sodium ion, cesium ion, and water self‐diffusion coefficients in a perfluorinated carboxylate polymer film have been measured. Results are compared to those obtained for a perfluorinated sulfonate polymer, Nafion. Both cation and water diffusion coefficients are very large in these materials in relation to the equilibrium amounts of sorbed water. The carboxylate polymer shows larger diffusion coefficients but smaller water sorption, compared to Nafion. Infrared results indicate significant changes in the state of sorbed water between the two materials. Results are discussed in terms of the ion clustered morphology of these ion exchange polymers.

52 citations


Journal ArticleDOI
TL;DR: In this paper, a perfluorinated carboxylate polymer film was studied in concentrated and solution environments at elevated temperatures, and the apparent of the exchange sites was found to be 1.9.
Abstract: Various properties of a perfluorinated carboxylate polymer film have been studied in concentrated and solution environments at elevated temperatures. Electrolyte and water sorption measurements reveal relatively constant electrolyte uptake but decreasing water sorption with increasing solution concentration. The apparent of the carboxylate exchange sites was found to be 1.9. Sodium ion self‐diffusion in the polymer was measured as a function of solution pH and concentration. Several differences in the diffusional properties of the carboxylate vs. Nafion sulfonate polymer films were found and are discussed in terms of ion pairing phenomena. Transport numbers for Na+ and in these polymers at high current densities were measured and are discussed in terms of the nature of ion transport in these polymers.

42 citations


Journal ArticleDOI
TL;DR: In this paper, the electrochemical behavior of solution species at electrodes consisting of a conductive polymer layer, produced by incorporation of tetrathiafulvalenium (T T P ) bromide into the cation-exchange polymer Nafion, on various substrates (Pt, Ta, SnO,, n-Si) is described.
Abstract: The electrochemical behavior of solution species at electrodes consisting of a conductive polymer layer, produced by incorporation of tetrathiafulvalenium ( T T P ) bromide into the cation-exchange polymer Nafion, on various substrates (Pt, Ta, SnO,, n-Si) is described. The voltammetric behavior of the solution species Fe(CN),'and Fey2(where Ye = ethylenediaminetetraacetate) at the Nafion-TTF' electrodes was consistent with models of electrodes partially covered with electronically conductive sites. Microscopic investigation of the electrode showed that the incorporated TTF+ forms electroactive domains and conductive nonelectroactive crystals from electrochemical cycling. The nonelectroactive crystals have the same stoichiometry as the one-dimensional organic conductor TTFBro,7. In the electrodeposition of copper onto the TTF' polymer electrode, most deposited on the TTFBT,,~, indicating that they were the major source of electronic conduction within the polymer. When the TTF' polymer was applied to the surface of an n-type Si electrode, the lifetime of the semiconductor electrode for the photooxidation of Fe(I1) species was improved. Polymer electrodes consist of thin (-0.1-10 pm) polymer layers on conductive (metal or carbon) substrates.'-3 These include polymers containing electroactive groups in the polymer backbone and polyelectrolyte layers in which electroactive ions are held by electrostatic binding., In these materials charge is transported by diffusion and migration of the ions as well as by electron hopping between electroactive sites. Electronically conductive polymers3 and the related one-dimensional organic metals4 (e.g., (1) (a) Merz, A.; Bard, A. J. J . Am. Chem. SOC. 1978, 100, 3222. (b) Itaya, K.; Bard, A. J. Anal. Chem. 1978, 50, 1487. (c) Van De Mark, M. R.; Miller, L. L. J . Am. Chem. Soc. 1978, 100,639. (d) Daum, P.; Murray, R. W. J . Electrochem. SOC. 1979, 103, 289. (e) Kaufman, F. B.; Engler, E. M. J . Am. Chem. SOC. 1979, 101, 547. (2) (a) Oyama, N.; Anson, F. C. J . Electrochem. Soc. 1980,127, 247. (b) Ibid. 1980,112, 271. (c) Rubinstein, I.; Bard, A. J. J . Am. Chem. SOC. 1980, 102, 6641. (d) Ibid. 1981, 103, 5007. (e) Oyama, N.; Anson, F. C. Anal. Chem. 1980, 52, 1192. (3) (a) Diaz, A. F.; Kanazawa, K. K. J . Chem. SOC., Chem. Commun. 1979,635. (b) Kanazawa, K. K.; Diaz, A. F.; Geiss, R. H.; Gill, W. P.; Kwak, J. F.; Logan, J. A.; Rabolt, J. F.; Street, G. B. Ibid. 1979, 854. (c) Diaz, A. F.; Castillo, J. I. Ibid. 1980, 397. (d) Kanazawa, K. K.; Diaz, A. F.; Gill, W. D.; Grant, P. M.; Street, G. B.; Gardini, G. P. Synth. Met. 1979/1980, 1 , 329. (e) Bull, R. A,; Fan, F. R.; Bard, A. J. J . Electrochem. SOC. 1982, 129, 1009. 0002-7863/82/1504-5862$01.25/0 TTF-TCNQ, where TTF is tetrathiafulvalene and TCNQ is Elgs] -(CF,CF,I,(CFCF, Iy I O(C,F,)OCF,CF,SO,-Na+

42 citations


Journal ArticleDOI
TL;DR: Proton NMR measurements of T 1, T 1 π and T 2 in perfluorosulphonate membranes, together with neutron scattering and dielectric data, show that the aqueous phase in Nafion solidifies at a glass transformation whose temperature T g is 168 K in water-saturated acid membranes as mentioned in this paper.

32 citations


Journal ArticleDOI
TL;DR: Mossbauer spectra of Nafion perfluoronated acid membranes exchanged with iron or europium have been studied as a function of ion concentration, water content, temperature, and applied magnetic field in order to characterize the ionic phase in these materials as mentioned in this paper.
Abstract: Mossbauer spectra of “Nafion” perfluoronated acid membranes exchanged with iron or europium have been studied as a function of ion concentration, water content, temperature, and applied magnetic field in order to characterize the ionic phase in these materials In every sample, the recoil-free fraction falls to zero at a temperature which decreases from 280 to 220 K with increasing water content The sudden fall in recoil-free fraction corresponds to a glass transition in the ionic phase rather than its melting point In Fe2+ Nafion, the spectrum is independent of water content above 6 wt%, and is typical of fully hydrated, isolated Fe2+(H2O)6 species The isomer shift, quadrupole splitting, and linewidth all change continuously below 6 wt % water, indicating a range of environments for the iron For Fe3+ Nafion, ions in several distinct environments can be identified on the basis of their magnetic properties Isolated Fe3+ species (Fe–Fe distances greater than 12 A) showing paramagnetic hyperfine structure in their 42-K spectra predominate in slightly neutralized samples, and in those with high water content The proportion of dimers, whose quadrupole splitting is about 17 mm/s, increases with increasing iron content or decreasing water content A third component of the spectra has a quadrupole splitting of 04 mm/s It is associated with paramagnetic iron having other iron ions in the neighborhood, and also with iron ions located in the interior of small groups or chains formed from dimers There is no iron belonging to magnetically ordered clusters involving hundreds of ferric ions of the type found in some other ionomers All the exchanged ions belong to the ionic phase, and none are associated with the polymer backbone

29 citations



Journal ArticleDOI
TL;DR: In this paper, the authors determined the diffusion coefficients and fluxes of sulfide and polysulfide species through Nafion membranes in order to correlate the physical properties of these membranes with their actual performance in three-electrode photoelectrochemical storage cells.
Abstract: The authors have determined the diffusion coefficients and fluxes of sulfide and polysulfide species through Nafion membranes in order to correlate the physical properties of these membranes with their actual performance in three-electrode photoelectrochemical storage cells. Diffusion coefficients for sulfide range from about 3 x 10 -9 to 1 x 10/sup 7/ cm/sup 2//sec, depending on the equivalent weight and thickness of the membrane, and the pH of the solution. Diffusion coefficients for polysulfide are considerably lower, and we discuss some reasons. A Nafion 315 membrane was chosen for the first test in the storage system and the results of the test are presented.

Journal ArticleDOI
TL;DR: In this article, the reaction of thiophene with acyclic acid anhydrides in the presence of Nafion-H (fluorocarbon resin sulfonic acid) afforded the corresponding 2-acylthiophenes in moderate yields.
Abstract: The reaction of thiophene with acyclic acid anhydrides in the presence of Nafion-H (fluorocarbon resin sulfonic acid) afforded the corresponding 2-acylthiophenes in moderate yields. Acylation with ...


Journal ArticleDOI
TL;DR: In this article, the mechanism of charge transport through Nafion polymers coated on glassy carbon electrodes and containing Cp2FeTMA+, R~(bpy),~+, and O~ (bpy,~+ ) is described.
Abstract: The mechanism of charge transport through Nafion polymers coated on glassy carbon electrodes and containing Cp2FeTMA+, R~(bpy),~+, and O~(bpy),~+ (where Cp2FeTMA+ is ((trimethylammonio)methyl)ferrocene, bpy = 2,2'-bipyridine) is described. The apparent diffusion coefficients, Dam,, of polymer modified electrodes, as measured by conventional electrochemical methods and which can include contributions from intermolecular electron transfer, are compared to the diffusion coefficients of actual mass transport of the electroactive species through the polymer, D,, as measured from the rate of permeation of the electroactive material. The results indicate that Dapp = D, for Cp2FeTMA+, Dapp 20, for Os(bpy),*+, and DaP4 = 15D, for Ru(bpy)t+. These results are discussed in terms of the Dahms-Ruff model, where the observed diffusional behavior is due to both physical diffusion of the electroactive species and an electron-transfer component that can contribute to the observed behavior. The contribution of the electron-exchange mechanism toward the value of Dapp decreases in the order of electroactive species, Ru(bpy),*+ >> O~(bpy),~+ 2 Cp2FeTMA+. A key question in the behavior of "polymer electrodes" (elec- trodes coated with a thin layer of polymer1-*) involves the mechanism of charge transport through the layers. The rate of charge transport frequently governs the rate of electrochemical and catalytic processes at such electrodes and has been the subject of numerous recent inve~tigations.~,~.~-" Charge can be trans- ported through the layer by electron transfer between redox centers, counterion diffusion, and diffusion of the electroactive species; the relative contribution of these effects is probably different for different kinds of polymer coatings.

Journal ArticleDOI
TL;DR: Reference electrodes utilizing cation exchanging qualities of perfluorosulfonic polymer membranes (Nafion) have been developed as mentioned in this paper, which are constructed of a plastic body with Nafion plug connecting inner and outer compartments.
Abstract: Reference electrodes utilizing cation exchanging qualities of perfluorosulfonic polymer membranes (Nafion) have been developed. They are constructed of a plastic body with Nafion plug connecting inner and outer compartments. The variability of the composition of filling solutions makes these electrodes suitable for applications where conventional reference electrodes cause interferring effects. Data on stability, reproducibility, effect of temperature, pH and total ionic strength of several cationic forms of the electrodes are presented.


Journal ArticleDOI
TL;DR: In this article, the reaction of thiophene with acyclic acid anhydrides in the presence of Nafion-H (fluorocarbon resin sulfonic acid) afforded the corresponding 2-acylthiophenes in moderate yields.
Abstract: The reaction of thiophene with acyclic acid anhydrides in the presence of Nafion-H (fluorocarbon resin sulfonic acid) afforded the corresponding 2-acylthiophenes in moderate yields. Acylation with ...