Phosphoric acid fuel cell 1132 Subject

Phosphoric acid fuel cells (PAFCs) are commercially available. Several hundred PAFC units, most of the order of 200 kW, are operating worldwide. PAFCs are realizing efficiencies of up to 40%. The only byproducts of PAFC operation are water and heat. However, enriched hydrogen fuel must be produced by subjecting hydrocarbon resources (natural gas or... 

In addition to loss of the platinum, the carlxm support that anchors the platinum crystallites and provides electrical coimectivity to the gas-diffusion media and bipolar plates is also subject to degradation. In phosphoric acid fuel cell, graphitized carbons are the standard because of the need for corrosion resistance in high-temperature acid environments [129], but PEM fuel cells have not employed fully graphitized carbons in the catalyst layers, due in large part to the belief that the extra cost could be avoided. Electrochemical corrosion of carbon materials as catalyst supports will cause electrical isolation of the catalyst particles as they are separated from the support or lead to aggregation of catalyst particles, both of which result in a decrease in the electrochemical active surface area of the catalyst and an increase in the hydrophUicity of the surface, which can, in turn, result in a decrease in gas permeability as the pores become more likely to be filled with liquid water films that can hinder gas transport. 

The polymer electrolyte fuel cell, PEFC, and the phosphoric acid fuel cell, PAFC, are acidic fuel cells the PEFC operates in the temperature range below and around 100 °C (PEFC), respectively, and the PAFC at around 200 °C. Hydrogen is the preferred fuel for both types. A PEFC can also be fed by liquid or gaseous methanol, called direct methanol fuel cell, DMFC. Other fuels based on alcohols, e.g., the direct ethanol fuel cell, DEFC, are subject to research. Fuel cell types utilizing an acidic aqueous electrolyte will not be considered here. 

The use of bio-fuels as a fuel in fuel cells has been relatively poorly explored. A few results have been obtained from simulations and experiments for SOFC in [31 0]. The main consideration in these studies of bio-fuel is bio-gas from sewage or gasifier. In many cases, bio-fuel is subjected to hydrogen reforming processes [41,42], and only hydrogen is supplied to the cells. Theoretical analysis [43] was also carried out with regard to reforming of bio-fuel for a phosphoric acid fuel ceU (PAFC). 

Additionally, the chemical resistance of the bipolar plate can be characterized by measuring the corrosion current under a potential typical for fuel cell operation and using 85 % phosphoric acid as an electrolyte. The relevance, detailed parameters, and development targets of this corrosion test are still subject to technical discussions and depend on the anticipated application of the plate. The accepted corrosion current under reference conditions is lower for long... 

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