Fuel cell design, conducting polymers

PPBP showed much higher and more stable proton conductivity than that of sul-fonated PEEK, which is in agreement with the strong water absorption of the former polymer, as a consequence of the presence of the flexible pendent side chains. These properties may be important for future design and development of fuel cells based on polymer electrolytes. 

Figure I.6a also reveals the timeline of milestones in fuel cell design. The leftmost curve is the performance curve of the first practical H2/O2 fuel cell, built by Mond and Langer in 1889 (Mond and Langer, 1889). The electrodes consisted of thin porous leafs of Pt covered with Pt black particles with sizes of 0.1 lam. The electrol)de was a porous ceramic material, earthenware, that was soaked in sulfuric acid. The Pt loading was 2 mg cm and the current density achieved was about 0.02 A cm at a fuel cell voltage of 0.6 V. The next curve in Figure I.6a marks the birth of the PEFC, conceived by Grubb and Niedrach (Grubb and Niedrach, 1960). In this cell, a sulfonated cross-linked polystyrene membrane served as gas separator and proton conductor. However, the proton conductivity of the polystyrene PEM was too low and the membrane lifetime was too short for a wider use of this cell. It needed the invention of a new class of polymer electrolytes in the form of Nafion PFSA-type PEMs to overcome these limitations.

Allcock, H. R. and Wood, R. M. 2006. Design and synthesis of ion-conductive polvphosphazenes for fuel cell applications Review. Journal of Polymer Science Part B 44 2358-2368. 

K. Miyatake, Y. Chikashige, M. Watanabe, Novel sulfonated poly(arylene ether) A proton conductive polymer electrolyte designed for fuel cells. Macromolecules 2003, 36(26), 9691-9693. 

The basic design of a fuel cell, an ionically conducting electrolyte and separator layer sandwiched between two electronically conducting gas diffusion electrodes (the fuel anode and the oxidant cathode, respectively), is shown schematically in Fig. 2 for a polymer electrolyte fuel cell with an acidic electrolyte and hydrogen and oxygen as the corresponding reactants. Typically, under open circuit conditions, H2/air fuel cells exhibit a cell voltage of... 

Abstract Chemical structure, polymer microstructme, sequence distribution, and morphology of acid-bearing polymers are important factors in the design of polymer electrolyte membranes (PEMs) for fuel cells. The roles of ion aggregation and phase separation in vinylic- and aromatic-based polymers in proton conductivity and water transport are described. The formation, dimensions, and connectivity of ionic pathways are consistently found to play an important role in determining the physicochemical properties of PEMs. For polymers that possess low water content, phase separation and ionic channel formation significantly enhance the transport of water and protons. For membranes that contain a high... 

The Nafion membrane, for instance, has shown good performance in fuel cells but has certain limitations, i.e., it has poor ionic conductivity at low humidity and is available at an expensive rate of 500 /m. The costs for Nafion , for example, become attractive only at high production voliunes [3]. Consequently, the search for new membrane materials with low cost and the required electrochemical characteristics, along with performances matching those of Nafion , is continuing and has become the most focused research area in the design of polymer electrolyte fuel cells. 

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