Proton exchange membrane fuel cell disadvantages

Recent developments in AAEMs have opened up the possibiUty of an alkaline analog of the acidic solid polymer electrolyte fuel cell. This could utilize the benefits of the alkaline cathode kinetics and at the same time eradicate the disadvantages of using an aqueous electrolyte. As the AAEM is also a polymer electrolyte membrane (sometimes abbreviated as PEM), some clarity in abbreviations is required. In this chapter, PEM refers only to the proton exchange membrane fuel cells (acidic), AAEM refers to the anion exchange membrane H2/O2 fuel cells, and AFC exclusively refers to the aqueous electrolyte alkaline H2/O2 fuel cells. Anion exchange membranes are also employed in alkaline direct alcohol fuel cells, discussion of which will refer to them as ADMFC/ADEFC (methanol/ ethanol). 

Some fuel cells use fuels other than hydrogen. For example, methane replaces hydrogen in some cells, but has the disadvantage of producing carbon dioxide as an exhaust gas. Fuel cells such as the one shown in Figure 20.13 use a plastic sheet called a proton-exchange membrane (PEM), which eliminates the need for a liquid electrolyte. 

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