Fuel perfluorinated membranes

Ionomer membranes are used in fuel cells in order to separate the anode and cathode compartment and to allow the transport of protons from the anode to the cathode. The typical membrane is Nation , which consists of a perfluorinated backbone and side chains terminated by sulfonic groups. In the oxidizing environment of fuel cells, Nation , as well as other membranes, is attacked by reactive oxygen radicals, which reduce the membrane stability. Direct ESR was used recently in our laboratory to detect and identify oxygen radicals as well as radical intermediates formed in perfluorinated membranes upon exposure to oxygen radicals [73,74]. The three methods used to produce oxygen radicals in the laboratory and the corresponding main reactions are shown below. 

Dolye, M. and Rajendran, G. 2003. Perfluorinated membranes. In Handbook of fuel cells—Fundamentals, technology and applications, part 3, ed. W. Vielstich, A. Lamm and H. A. Gasteiger, 351. Colchester, England John Wiley Sons. 

Eisman, G. A. 1990. The applications of Dow GhemicaTs perfluorinated membranes in proton exchange membrane fuel cells. Journal of Power Sources 29 389-398. 

S. Tsushima, S. Hirai, K. Kitamura, M. Yamashita, S. Takasel, MRI application for clarifying fuel cell performance with variation of polymer electrolyte membranes Comparison of water content of a hydrocarbon membrane and a perfluorinated membrane. Appl. Magn. Reson. 32, 233-241 (2007)... 

Perfluorinated membranes are still regarded as the best in the class for PEM fuel cell applications. - These materials are commercially available in various forms from companies such as DuPont, Asahi Glass, Asahi Chemical, 3M, Gore, and Sol-vay. Perfluorosulfonic acid (PFSA) polymers all consist of a perfluorocarbon backbone that has side chains terminated with sulfonated groups. 

Doyle, M. and Rajendran, G., Perfluorinated membranes, in Elandbook of Fuel Cells Fundamentals, Technology, and Applications, 1st ed., Vielstich, W., Lamm, A., and Gasteiger, H.A., Eds., John Wiley Sons, West Sussex, England, 2003, p. 351. 

Nafion, a perfluorinated sulfonic acid (PFSA) polymer electrolyte developed and produced by the E. I. Dupont Company, has been extensively studied as a fuel cell membrane. Despite its age, it remains the industry standard membrane because of its relatively high proton conductivity, toughness and quick start capabilities. Attempts to build upon the strengths of Nafion have resulted in a class of PFSA polymer electrolytes, including the short-side-chain (SSC) PFSA polymer electrolyte, originally synthesized by Dow and now produced by Solvay Solexis. Stracturally, PFSA polymer... 

Industrial production of perfluorinated ionomers, Nafion membranes, and all perfluorinated membranes is costly due to several factors first, the monomers used are expensive to manufacture, since the synthesis requires a large number of steps and the monomers are dangerous to handle. The precautions for safe handling are considerable and costly. Secondly, the PSEPVE monomer is not used for other applications, which limits the volume of production. The most significant cost driver is the scale of production. Today, the volume of the Nafion market for chlor-aUcali electrolysis (150,000 m year ) and fuel cells (150,000 m year ) is about 300,000 m year resulting in a production capacity of 65,000 kg year. When compared to large-scale production of polymers like Nylon (1.2 x 10 m year ), the perfluorinated ionomer membrane is a specialty polymer produced in small volumes. 

In spite of the documented, relatively high chemical stability of poly(PFSA) membranes in the fuel-cell environment, recent extensive work looking into the origins of performance loss observed in PEFCs has revealed important mechanisms of degradation that apply to perfluorinated membranes (while being further amplified in nonperfluorinated membranes). An important mechanism of membrane... 

G.A. Eisman, The application of Dow Chemical s perfluorinated membrane in proton-exchange fuel cell, J. Power Sources, 1990, 29, 389-398. 

While Nafion , a perfluorinated polymer developed by DuPont, is the most commonly used proton conductive polymer electrolyte membrane it is an insufficient solution in a number of areas. It has high cationic transport (approximately 9.56 5/cm) [8] but also has high levels of methanol fuel crossover, slow anode kinetics and very high cost [12]. Fuel cell membrane performance can be estimated from the ratio of proton conductivity (a) to methanol permeability (P). The higher the value of a/P, the better the membrane performance would be [13]. Chitosan has been shown to have a much lower methanol permeability than Nafion [14], and as such, a great deal of attention focused on developing chitosan membranes with high levels of ionic conduction and low methanol permeability as delineated in Table 3.1. 

The membrane material most often used in fuel cells today is Nation , made by DuPont. Nation is the product name of a perfluorosulfraiic acid/polyethylene copolymer (PFSA/PTFF) that clearly meets the specifications for thermal and chemical stability and high levels of protmi conductivity and electrical resistance. Other perfluorinated membranes are now commercially available in addition to Nation DOW Membrane from Dow Chemical Corp. and a membrane made by... 

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. 

Doyle M, Rajendran G (2003) Perfluorinated membranes. In Vielstich W, Gasteiger HA, Lamm A (eds) Handbook of fuel cells fimdamentals, technology and applications. WUey, Chichester, pp 351-395... 

Among the cation permeable membranes, the perfluorinated membranes which have been developed as separators for fuel cells and chlor-alkali electrolysers show the characteristic features of superselectivity, very high thermal stability and chemical resistance, which are not obtained by the other classes of polymeric ion permeable membranes. Three commercial forms of cation permeable perfluorinated membranes have been proposed ... 

Perfluorosulphonic Nation membrane separators are used in direct contact with electrodes as solid polymer electrolytes (SPE) in fuel cells . In this case, the membrane is both the electrolyte and the separator. The use of perfluorosulphonic membranes as SPE started 30 years ago with the US space program Gemini and the realization of low temperature H2/O2 SPE fuel cells. Since then, the feasibility of operating the SPE fiiel cells on hydrogen/halogen couples has been demonstrated. In addition, the introduction of perfluorinated membranes for use in water and brine electrolysis and more recently in organic synthesis has taken place . 

Banerjee, S. and Curti, D.E. 2004. Nation perfluorinated membranes in fuel cells. 

S. Banerjee and D.E. Curtin, Naflon perfluorinated membranes in fuel cells , Journal of Fluorine Chemistry, 125 (2004) 1211-1216. 

Tokuyama, a Japanese company specializing in membrane technology for electrodialysis and desalination, has undertaken development of AEMs in OH form, targeting fuel-cell applications. Tokuyama s 901 membrane anion conductivity, 30 mScm, at roughly half that of the proton conductivity of the perfluorinated membranes, is at an acceptable level for fuel-ceU development. Other material properties, such as dimensional stability due to the swelling as a result of the uptake of water, are also reasonable and are, in fact, better than those of typical PFSA membranes [36]. 

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