Perfluorosulfonic acid ionomer membrane

Ghassemzadeh, L., Marrony, M., Barrera, R., Kreuer, K. D., Maier, and Muller, K. 2009. Chemical degradation of proton conducting perfluorosulfonic acid ionomer membranes studied by solid-state nuclear magnetic resonance spectroscopy. Journal of Power Sources 186 334-338. 

The electrolyte is a perfluorosulfonic acid ionomer, commercially available under the trade name of Nafion . It is in the form of a membrane about 0.17 mm (0.007 in) thick, and the electrodes are bonded directly onto the surface. The elec trodes contain veiy finely divided platinum or platinum alloys supported on carbon powder or fibers. The bipolar plates are made of graphite or metal. 

An adequate structure of polymer molecules promotes the advantageous phase separation into hydrophobic and hydrophilic domains upon water uptake. The most notable class of membranes based on this principle are the perfluorosulfonic acid ionomers (PFSI), Nafion [26] and similar membranes [27]. In these membranes, perfluorosulfonate side chains, terminated with hydrophilic —SO3H groups, are attached to a hydrophobic fluorocarbon backbone. The tendency of ionic groups to aggregate into ion clusters due to the amphiphilic nature of the ionomer leads to the formation of basic aqueous units. At sufficient humidity these units first get connected by narrow channels and then may even fuse to provide continuous aqueous pathways [28]. 

Kreuer et al. [25] investigated the membrane properties, including water sorption, transport (proton conductivity, electro-osmotic water drag and water diffusion), microstructure and viscoelasticity of the short-side-chain (SSC) perfluorosulfonic acid ionomers (PFSA, Dow 840 and Dow 1150) with different lEC-values. The data were compared to those for Nafion 117, and the implications for using such ionomers as separator materials in direct methanol and hydrogen fuel cells discussed. Tire major advantages of PFSA membranes were seen to be (i) a high proton conductivity. 

Cation-exchange membranes, perfluorosulfonic acid ionomer, 125... 

Polymer electrolyte membrane Polymer electrolyte membrane fuel cell Pulse field gradient NMR spectroscopy Perfluorosulfonic acid ionomer... 

Ogumi Z (2010) Aminated perfluorosulfonic acid ionomers to improve the triple phase boundary region in anion-exchange membrane fuel cells. J Elecliochem Soc 157(11) A1153-A1157. doi 10.1149/ 1.3483105... 

Key words electrolyte, membrane, proton conductor, perfluorosulfonic acid, ionomer, acid-doped membranes, sulfonic acid, phosphonic acid, heterocycle,... 

Zhang YM, Li L, Tang JK, Bauer B, Zhang W et al. (2009) Development of covalently cross-linked and composite perfluorosulfonic acid membranes . ECS Trans. 25 1469. Gao HR, Jones DJ, Roziere J, Zhang YM (2011) Cross-linking of the short-side-chain perfluorosulfonic acid ionomer . Manuscript in preparation. 

The advent of Du Pont s inert perfluorosulfonic acid membranes, Nafion, in the late 1960,s made chlor-alkali production in a membrane cell a realistic possibility. The basic structure of Du Pont s fluoro ionomer is shown... 

I, 1980, 76, 2558-2574 L.Y. Levy, A. Jenard and H.D. Hurwitz, Hydration and ion-exchange process in carboxylic membranes. Part 1. Infrared spectroscopic investigation of the acid membranes, J. Chem. Soc. Trans. 1, 1982, 78, 29-36 M. Falk, Infrared spectra of perfluorosulfonated polymer and water in perfluorosulfonate polymer, Perfluorinated Ionomer Membranes, ed. A. Eisenberg, H.L. Yeager, ACS Symposium Series, American Chemical Society, Washington DC, 1982, p. 139 C. Heitner-Wirguin and D. Hall, An infrared study of an anion exchange membrane,... 

Z.D. Deng and K.A. Mauritz, Dielectric relaxation studies of acid-containing short-side-chain perfluorosulfonate ionomer membranes, Macromolecules, 1992, 25, 2369-2380. 

Copolymers of tetrafluoroethylene and sulfonic acid functional per-fluorinated monomers (e.g., Nafion, Dow s perfluorosulfonic acid (PFSA)) have high water permeability. Water transport through these ionomer membranes has been investigated. The non-Fickian diffusion process is analyzed by a thermodynamic approach. The results provide some useful insights into the behavior of these materials as dehydration membranes. 

Yoshimiu-a and Iwasaki of Sumitomo Chemical Co. have synthesized aromatic ionomers containing pendant perfluorosulfonic acid groups (Fig. 7.29) [79]. Poly (arylene ether sulfone) was brominated and then perfluorosulfonated via Ullmann coupling reaction in the presence of copper catalyst. The lEC was controllable up to 1.58 meq/g. The obtained ionomer membranes behaved very differently from the typical sulfonated aromatic ionomer membranes. Characteristic hydrophobic/hydro-philic separation (ca. 3-4 nm) was observed in the smaU-angle X-ray scattering (SAXS) analyses of the hydrated samples. The ionic clusters were slightly smaller... 

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