Types of Fuel Cell and Catalyst

Depending of the fuel applied and the nature of electrolyte, six fuel cells can be distinguished. These fuel cell systems are hsted in Table 9-1. 

Electrolyte KOH Polymer H3PO4 Molten carbonate Ceramic Polymer 

AFC = alkaline fuel cell PEMFC = proton exchange membrane fiiel cell PAFC = phosphoric acid fuel cell MCFC = molten carbonate fuel cell SOFC = solid oxide fuel cell DMFC = direct methanol fuel celt 

Apart from exhibiting electrocatalytic activity towards the electrode reactions, the electrocatalysts must be stable within the working cell. For the alkaline fuel cell (AFC) this is relatively easy since many electrocatalytic materials are adequately stable in alkaline solutions. The fact that the AFC is very sensitive to the presence of CO2, either in the fuel stream or in the air stream, has limited its application substantially to those simations where very pure hydrogen and very pure oxygen can be supplied. 

For the fuel cells employing acidic electrolytes, stabdity of the electrocatalysts is much more difficult to realize. Many electrocatalysts have been examined over many years for their application to fuel cells. The nature of preferred electrocatalysts is critically dependent on the kind of fuel cell. 

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