Low-temperature Fuel Cells PEMFCs and DAFCs

The last three fuel cells (PEMFC, DAFC and SAMFC) are low-temperature fuel cells. In this chapter, the discussion will be focused on these fuel cells, particularly the PEMFC and the DAFC, since they can accommodate biomass fuels, either after fuel processing to obtain reformate hydrogen or directly with bioethanol. 

In this chapter, after recalling the working principles and the different kinds of fuel cells, the discussion will be focused on low-temperature fuel cells (AFC, PEMFC, and DAFC), in which several kinds of carbon materials are used (catalyst support, gas-diffusion layer [GDL], bipolar plates [BP], etc.). Then some possible applications in different areas will be presented. Finally the materials used in fuel cells, particularly carbon materials, will be discussed according to the aimed applications. To read more details on the use of carbon in fuel cell technology, see the review paper on The role of carbon in fuel cell technology recently published by Dicks [6],... 

For low-temperature fuel cells (AFC, PEMFC, and DAFC) carbon is mainly used... 

In low-temperature fuel cells (AFC, PEMFC, DAFC, etc.), carbon materials are important since they are involved in the fabrication of BP, GDL, and CL. It appears that no other materials can replace carbon with the same properties (good electronic conductivity, good thermal and chemical stabilities, and low cost). But much work is needed to optimize carbon materials for fuel cell applications and to ensure that they meet the performance targets for conductivity, physical properties, and lifetime within operating stacks. 

DMFCs and direct ethanol fuel cells (DEFCs) are based on the proton exchange membrane fuel cell (PEM FC), where hydrogen is replaced by the alcohol, so that both the principles of the PEMFC and the direct alcohol fuel cell (DAFC), in which the alcohol reacts directly at the fuel cell anode without any reforming process, will be discussed in this chapter. Then, because of the low operating temperatures of these fuel cells working in an acidic environment (due to the protonic membrane), the activation of the alcohol oxidation by convenient catalysts (usually containing platinum) is still a severe problem, which will be discussed in the context of electrocatalysis. One way to overcome this problem is to use an alkaline membrane (conducting, e.g., by the hydroxyl anion, OH ), in which medium the kinetics of the electrochemical reactions involved are faster than in an acidic medium, and then to develop the solid alkaline membrane fuel cell (SAMFC). 

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