The polymer electrolyte fuel cell (PEFC) has been one of the most studied fuel cell systems, because of several advantages for transportation applications. Research involve fundamental aspects related to the water transport and the fuel cell reactions (1,2), the practical aspects related to the optimization of the structure and operational conditions of gas diffusion electrodes (1-6), and technological aspects related to water management and the engineering of operational sized fuel cell modules (7-13). In many of these works it is observed that very satisfactory results regarding the performance of low catalyst loading electrodes (0.15 to 0.4 mg Pt/cm2) hgve been obtained in single cells (2-6). However, the use of such electrodes is not yet being considered for building fuel cell stacks and, although not usually mentioned (7-13), fuel cell modules are assembled employing electrodes presenting catalyst loadings in the range of 2 to 4 mgPt cm"2.

In this work the results on the research and development of small polymer electrolyte fuel cell stacks employing low catalyst loading electrodes are described. The systems include the assembly of single cells, 6-celI and 21-cell modules. Testing of the stacks was conducted in a specially designed test station employing non-pressurized H2/02 reactants and measuring the individual and the overall cell voltage versus current characteristics under several operational conditions for the system.

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