Types of Alkaline Fuel Cells

For alkaline fuel cells, the electrolyte is concentrated (85 wt%) KOH at the operating temperature of 250°C. However, the concentration of KOH is kept between 

35 and 50 wt% for lower operating temperatures of 120°C. In addition, spinels, metal oxides, noble metals, nickel and silver are also used as electrocatalysts. The alkaline fuel cells are further classified into three main categories. 

unlike mobile electrolyte AFC, the electrolyte does not need to be pumped out. Moreover, there is no problem of an internal short-circuit, which makes it more favourable for space applications. The KOH electrolyte in an asbestos matrix possesses excellent porosity, corrosion resistance and strength. Due to the stationary nature of the electrolyte, it becomes mandatory that pure oxygen should be supplied at the cathode. In case CO2 is present in the air, carbonate formation takes place and the complete fuel cell needs to be rebuilt. Hydrogen is pumped at the anode and circulated to remove water. The cooling system comprises fluorinated hydrocarbon dielectric liquid. The product water is used for humidification of the cabin, cooking and drinking in space orbiter systems. As the water is used at the cathode, its level must be kept sufficiently high at the anode side. 

This type of alkaline fuel cell is easy to fabricate and is used for high power generation. The schematic of a dissolved fuel alkaline fuel cell is shown in Fig. 1.8. 

8e is obtained per the NaBH4 atom, which indicates its remarkable potential as a fuel. The hydrolysis reaction is also supported by the catalysts, which leads to losses in these fuel cells, i.e.. 

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