PEMFC development, areas

PEMFC current development needs are relatively well documented and easily accessible by browsing the US Department of Energy web site [9-11]. The four major areas of PEMFC development needs are succinctly summarized as ... 

Sol-gel techniques have been successfidly applied to form fuel cell components with enhanced microstructures for high-temperature fuel cells. The apphcations were recently extended to synthesis of hybrid electrolyte for PEMFC. Although die results look promising, the sol-gel processing needs further development to deposit micro-structured materials in a selective area such as the triple-phase boundary of a fuel cell. That is, in the case of PEMFC, the sol-gel techniques need to be expanded to form membrane-electrode-assembly with improved microstructures in addition to the synthesis of hybrid membranes to get higher fuel cell performance. 

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. 

With the continued extensive progress in PEMFC technology and science, there is a need for updated information—particularly in the area of material properties and performance. Given the highly interdisciplinary nature of the fuel cell field, a wide spectrum of relevant scientific, engineering, and technical aspects needs to be covered. This book will provide updated, detailed background material on key developments in the PEMFC area. In particular. 

Matos et al. 60] developed Nafion-titanate nanotube composites as the PEMFC electrolyte operating at elevated temperatures. The addition of 5-15 wt% nanotubes to the ionomer allowed the PEMFC performance essentially to be sustained up to 130 °C. The polarization curves of PEMFCs using composite electrolytes reflected a competing effect between an increase in water uptake due to the extremely large surface area of the nanotubes, and a decrease in the proton conductivity of the composites. 

In view of the significant modeling activities and number of active groups worldwide, it is useful to assess the current status to ensure future developments will address PEMFC areas of major concern. This is especially important considering that PEMFCs are at a critical juncture. Large capital amounts have already been spent during the last ten years with even larger sums likely... 

Not surprisingly, the focus in this area has been on the development of phosphonated PEMFC membranes. However, phosphonated membranes can also be of interest for use as electrol3Aes in other electrochemical devices such as flow batteries. In addition, there are now a few reports on the preparation and study of polymers functionalized with phosphonium... 

The PEMFC system has seen such an important development in the last ten years that it would be impossible to describe in few lines the extent of its application. The transport area is surely the most challenging. After fluctuating periods, serious advances have been made on the cost and efficiency levels. Daimler is announcing a well-planned market entry for a fuel cell vehicle in 2014. US and Japanese developers are also ready. Already there are several buses fleet in many European, American and Asian cities. Light portable applications have their niche markets and numerous PEMFC units are already in use for residential applications, most particularly in Japan. In Canada, the first commercial benefits from PEMFC systems have been registered in the three last years. Moreover, the intense research activity on membranes and the opportunities offered by higher operating temperatures and relatively low humidity open an important field of development. 

Fig. 15.25 Pathways for future electrocatalyst development for automotive PEMFCs. (a) Thick films or bulk single crystal and polycrystalline catalysts that are ideal for fundamental studies on surface structure and mechanisms these materials need to be modified into (c) and (d) to be applicable to fuel cells, (b) Typical commercial nanoparticles (2-4 nm) on a high-surface-area carbon support used in fuel cells at this time (c) Thin continuous films of catalyst on a support such as carbon nanotubes that may provide a physical porous structure for mass transport in a fuel cell (d) Core-shell catalysts where only the shell eonsists of precious metals and are supported on a typical high-surface-area support [72, 77, 89]...

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