New Proton Exchange Membranes

All these attempts to improve the membrane characteristics by decreasing the methanol crossover and increasing their temperature resistance gave encouraging results. However, modification of the existing membranes (e.g., with barrier screens) without decreasing the electrical 

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These main objectives can be reached only by modifying the structures and compositions of primarily the anode (methanol electrode) and secondarily the cathode (oxygen electrode) as discussed in Sections 111 and IV, respectively. In addition. Section IV discusses the conception of new proton exchange membranes with lower methanol permeability in order to improve the cathode characteristics. Section V deals with the progress in the development of DMFCs, while in Section VI the authors attempt to make a prognosis on the status of DMFC R D and its potential applications. 

Following a period of slack, decisive improvements were made after 1990 in the area of PEMFCs. Modem models now achieve specific powers of over 600 to 800 mW/cm while using less than 0.4 mg/cm of platinum catalysts and offering a service fife of several tens of thousands of hours. These advances were basically attained by the combination of two factors (1) using new proton-exchange membranes of the Nafion type, and (2) developing ways toward much more efficient utilization of the platinum catalysts in the electrodes. 

Wang, R, Hickner, M., Kim, Y. S., Zawodzinski, T. A. and McGrath, J. E. 2002. Direct polymerization of sulfonated poly(arylene ether sulfone) random (statistical) copolymers Candidates for new proton exchange membranes. Journal of... 

Linkous CA, Anderson HR, Kopitzke RW, Nelson GL (1998) Development of new proton exchange membrane... 

Linkous, C.A. et al. Development of new proton exchange membrane electrolytes for water electrolysis at higher temperatures, Int J. Hydrogen Energy, 23, 525-529 (1998). 

Recently, UTC Fuel Cells announced a new proton exchange membrane demonstration fuel cell that will sell for about 2,000/kW. This, of course, is approaching the "magic number."... 

Haug AT, White RE. Oxygen diffusion coefficient and solubility in a new proton exchange membrane. J Electrochem Soc 2000 147(3) 980—3. 

Xu W, Liu C, Xue X et al (2004) New proton exchange membranes based on poly(vinyl alcohol) for DMFCs. Solid State Ion 171 121-127... 

Numerous works by other authors and our own research group describe the syntheses of new proton exchange membranes based on hydrocarbon polymers. The characteristics of these new materials, which determine their potential applications, are discussed in detail. A review of electrochemical properties, water uptake, and thermal stability makes possible a comprehensive understanding of the proton conduction mechanism and physical state of absorbed water in these systems. 

Over the last decade, several new proton exchange membranes have been developed. The new polymers in fuel cell applications are based mostly on hydrocarbon structures for the polymer backbone. Poly(styrene sulfonic acid) is a basic material in this field. In practice, poly(styrene sulfonic acid) and the analogous polymers such as phenol sulfonic acid resin and poly(trifluorostyrene sulfonic acid), were frequently used as polymer electrolytes for PEMFCs in the 1960s. Chemically and thermally stable aromatic polymers such as poly(styrene) [ 3 ], poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbony 1-1,4-phenylene) (PEEK) [4], poly(phenylenesulfide) [5], poly(l,4-phenylene) [6, 7], poly (oxy-1,4-phe-nylene) [8], and other aromatic polymers [9-11], can be employed as the polymer backbone for proton conducting polymers. These chemical structures are illustrated in Fig. 6.2. 

Yang, S., Gong, C., Guan, R., Zou, H., Dai, H. (2006) Sulfonated poly(phenylene oxide) membranes as promising materials for new proton exchange membranes. Polymers for Advanced Technologies, 17, 360 365. 

W.H. Choi, W.H. Jo, Preparation of new proton exchange membrane based on self-assembly of poly(styrene-co-styrene sulfonic acid)-b-poly(methyl methacrylate)/ poly(vinylidene fluoride) blend, J. Power Sources, 188 (2009) 127-131. 

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