Membranes perfluorosulfonate polymer

The first membranes to show significant potential and trigger the development of membrane electroly2ers were made from the perfluorosulfonate polymer called Nafion (40,41). 

Membrane cells are the state of the art chlor-alkah technology as of this writing. There are about 14 different membrane cell designs in use worldwide (34). The operating characteristics of some membrane cells are given in Table 3. The membranes are perfluorosulfonate polymers, perfluorocarboxylate polymers, and combinations of these polymers. Membranes are usually reinforced with a Teflon fabric. Many improvements have been made in membrane cell designs to accommodate membranes in recent years (35,36). 

R. Yeo, Application of Perfluorosulfonated Polymer Membranes in Fuel Cells, Electrolysis, and Load Leveling Devices, in Perfluorinated Ionomer Membranes, A. Eisenberg and H.L. Yeager (eds), ACS Symposium Series Number 180, American Chemical Society, Washington, DC, pp. 453-473 (1982). 

In a H2/air fuel cell, the protons produced at the anode side need to be transferred to the cathode side to react with 02. This requires a proton transport electrolyte. Nafion membranes, composed of a perfluorosulfonated polymer, are the most commonly used polymer electrolyte membranes to conduct protons. The structure of the Nafion membrane is shown in Figure 1.5. Nafion can take on a... 

Feldheim DL, Lawson DR, Martin CR (1993) Influence of the sulfonate countercation on the thermal stability of Nation perfluorosulfonate membranes. J Polym Sci Part B Polym Phys 31(8) 953—7... 

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]. 

Hopfinger and Mauritz and Hopfinger also presented a general formalism to describe the structural organization of Nafion membranes under different physicochemical conditions. It was assumed that ionic clustering does not exist in the dry polymer. This assumption is applicable to the perfluorinated carboxylic acid polymer" but not the perfluorosulfonate polymers." They consider the balance in energy between the elastic deformation of the matrix and the various molecular interactions that exist in the polymer. 

Self-diffusion coefficients of polyvalent cations in these perfluorinated ionomer membranes have not been reported. It can be inferred from the use of the sulfonate membranes as Donnan dialysis devices that transport of cations such as CuflT), Mg(II), and Al(III) under a concentration gradient is rapid. Also, column chromatographic separation of the alkaline-earth ion is readily accomplished with a powdered Nafion perfluorosulfonate polymer, which is again an indication of facile diffusion of these cations within the polymer phase. 

The majority of research which is discussed in this volume deals with the Nafion brand perfluorosulfonate polymers, manufactured by E. I. du Pont de Nemours and Co.. These materials were developed during the middle 1960 s, and have been available in various forms for study during the past few years. The synthesis and general properties of Nafion membranes are summarized... 

Applications of Perfluorosulfonated Polymer Membranes in Fuel Cells, Electrolyzers, and Load Leveling Devices... 

Yeo R S 1982 Applications of perfluorosulfonated polymer membranes in fuel cells, electrolyzers, and load leveling devices Perfluorinated lonomer Membranes ed A Eisenberg and H L Yeager (Washington, DC American Chemical Society) pp 453-73... 

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,... 

E.J. Roche, M. Pineri and R. Duplessix, Phase separation in perfluorosulfonic ionomer membrane, J. Polym. Sci., Polym. Phys. Ed., 1982, 20, 107-116 C. Heitner-Wirguin, Recent advances in perfluorinated ionomer membranes structure, properties and application, J. Membr. Sci., 1996, 120, 1-33 G. Gebel and J. Lambard, Small-angle scattering study of water-swollen perfluorinated ionomer membranes, Macromolecules,... 

Abstract This article outlines some history of and recent progress in perfluorinated membranes for polymer electrolyte fuel cells (PEFCs). The structure, properties, synthesis, degradation problems, technology for high temperature membranes, reinforcement technology, and characterization methods of perfluorosulfonic acid (PFSA) membranes are reviewed. 

Several types of perfluorosulfonated polymers were also developed, such as the Dow membrane Aciplex , depending on their equivalent weight and thickness [133]. 

The principle of operation is shown in Fig. 2. Chlorine gas is produced at the anode (especially optimized dimensionally stable anode) with an anolyte feed concentration of 14 wt % HCl. Anode and cathode are separated by a cation exchange membrane (perfluorosulfonic acid polymer, PFSA, e.g., Nafion of DuPont). The ODC is based on a conductive carbon cloth which operates simultaneously as a gas diffusion layer because a suitable material is incorporated. The oxygen reduction reaction (5) takes place in three-phase boundaries of a thin, porous catalyst layer on the surface. 

Abstract In this chapter, we discuss the proton conductivity and use of heteropoly acids (HP As) in proton exchange fuel cells. We first review the fundamental aspects of proton conduction in the HPAs and then review liquid HPA-based fuel cells. Four types of composite proton exchange membranes containing HPAs have been identified HPAs imbibed perfluorosulfonic acid membranes, HPAs imbibed hydrocarbon membranes, sol-gel-based membranes, and polymer hybrid polyoxometa-late (polypom)-based membranes. 

Alternatively, electrospun functionalized nanofibers with high proton conductivity could also be incorporated into polymer matrices, in which perfluorosulfonated polymers, such as Nation , were selected as the matrix polymers. With the filled proton-conducting component fibers, the proton conductivity of composite membranes could be greatly enhanced. The relative reports are shown in Table 2.4. 

The most commercially successful are membranes Nafion (Du Pont, USA). Nafion is perfluorosulfonic ionomer with high proton conductivity and chemical and mechanical stability [6]. However, limited operation temperature, low water uptake, and high cost are disadvantages of the perfluorosulfonic polymer. 

Kumar, S. and Pineri, M. (1986) Interpretation of small angle X-ray and neutron scattering data for perfluorosulfonated ionomer membranes, J. Polym. Sci. Polym. Phys. Ed., 24, 1767-1782. 

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