Fuel cells different families

Wholly aromatic polymers are thought to be one of the more promising routes to high performance PEMs because of their availability, processability, wide variety of chemical compositions, and anticipated stability in the fuel cell environment. Specifically, poly(arylene ether) materials such as poly-(arylene ether ether ketone) (PEEK), poly(arylene ether sulfone), and their derivatives are the focus of many investigations, and the synthesis of these materials has been widely reported.This family of copolymers is attractive for use in PEMs because of their well-known oxidative and hydrolytic stability under harsh conditions and because many different chemical structures, including partially fluorinated materials, are possible, as shown in Figure 8. Introduction of active proton exchange sites to poly-(arylene ether) s has been accomplished by both a polymer postmodification approach and direct co-... 

The term electromembrane process is used to describe an entire family of processes that can be quite different in their basic concept and their application. However, they are all based on the same principle, which is the coupling of mass transport with an electrical current through an ion permselective membrane. Electromembrane processes can conveniently be divided into three types (1) Electromembrane separation processes that are used to remove ionic components such as salts or acids and bases from electrolyte solutions due to an externally applied electrical potential gradient. (2) Electromembrane synthesis processes that are used to produce certain compounds such as NaOH, and Cl2 from NaCL due to an externally applied electrical potential and an electrochemical electrode reaction. (3) Eletectromembrane energy conversion processes that are to convert chemical into electrical energy, as in the H2/02 fuel cell. 

Fig. 2 Monomers of the styrene family used in the preparation of radiation-grafted fuel cell membranes in different laboratories. The aromatic ring can be sulfonated, or the acid functionality may be incorporated via the R substituent...

The high EWs of the first Nafion membranes family limited their use in fuel cells and prompted the development of the Dow membrane. This membrane is structurally and morphologically similar to the Nafion membrane, but differs with respect to its EWs, which are typically in the 800 to 850 range, and have shorter size chains (z = 0 for Dow and z = 1 for Nafion) (Utracki and Weiss, 1989). The Dow membranes are a short side chain perfluorinated ionomer whereas the Nafion membranes are the long side chain perfluorinated ionomer. The specific conductance of 800 and 850 EW experimental membranes has been reported as 0.20 and 0.12 Q cm", respectively (Savadogo et al, 1995). It must be pointed out that the Dow monomer is more complicated to elaborate than the DuPont monomer. Therefore, the synthesis of the Dow epoxy is more complicated than that of the Nafion, which is a commercially available material (Savadogo et al, 1995). 

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