PEFCs perfluorinated membranes

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... 

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. 

Major areas of application are in the field of aqueous electrochemistry. The most important application for perfluorinated ionomers is as a membrane separator in chloralkali cells.86 They are also used in reclamation of heavy metals from plant effluents and in regeneration of the streams in the plating and metals industry.85 The resins containing sulfonic acid groups have been used as powerful acid catalysts.87 Perfluorinated ionomers are widely used in worldwide development efforts in the held of fuel cells mainly for automotive applications as PEFC (polymer electrolyte fuel cells).88-93 The subject of fluorinated ionomers is discussed in much more detail in Reference 85. 

The PEFC was first developed for the Gemini space vehicle by General Electric, USA. In this fuel cell type, the electrolyte is an ion-exchange membrane, specifically, a fluorinated sulfonic acid polymer or other similar solid polymer. In general, the polymer consists of a polytetrafluoroethylene (Teflon) backbone with a perfluorinated side chain that is terminated with a sulfonic acid group, which is an outstanding proton conductor. Hydration of the membrane yields dissociation and solvation of the proton of the acid group, since the solvated protons are mobile within the polymer. Subsequently, the only liquid necessary for the operation of this fuel cell type is water [7,8],... 

Initially, poly(styrenesulfonic acid) (PSSA) and sulfonated phenol-formaldehyde membranes were used for PEFCs, but the useful life of these materials was limited because of significant degradation under fuel-cell operating conditions. A critical breakthrough was achieved with the introduction of Nafion , a perfluorinated polymer with side chains... 

In the preceding chapter, recent progress on perfluorinated ionomer membranes is reviewed. There is no doubt that the perfluorinated ionomer membranes will dominate in the area of polymer electrolyte fuel cells (PEFCs) for the years to come however, drawbacks peculiar to perfluorinated materials such as high production... 

Pozio, A., Silva, R. R, De Francesco, M. and Giorgi, L. (2003) Nafion degradation in PEFCs from end plate iron contamination. Electrochim. Acta 48, 1543-1549 Qiao, J., Saito, M., Hayamizu, K. and Okada, T. (2006) Degradation of perfluorinated ionomer membranes for PEM fuel cells during processing with H Oj. J. Electrochem. Soc. 153, A967-A974... 

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