Abstract
With respect to polymer electrolyte fuel cells (PEFC), degradation of the catalyst and gas diffusion layers, which are parts of the membrane electrode assembly (MEA), and its influence on electrode flooding were investigated. Highβhumidity operation is desirable for high performance of a PEFC, because the proton exchange membrane and ionomer at the catalyst layer must hold a large amount of water. Additionally, high gas utilization is necessary for high system efficiency. However, under these conditions, the cell performance is significantly degraded by water flooding of the electrodes. A PEFC single cell was operated at 0.3 A/cm^2^ at high humidity for 10,000 h, and the cell performance was evaluated in terms of the cell potential, cell resistance, IV characteristics, crossover rate, effective chemical surface area, and oxygen gain, in order to determine the parts of the cell that play a dominant role in cell degradation. Degradation of gas diffusivity was found to dominate the degradation of cell performance, and it was found to occur mainly in the catalyst layer rather than in the gas diffusion layer. Β© 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(3): 10β17, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20899