A simplified model for water management in a polymer electrolyte membrane ͑PEM͒ fuel cell operating under prescribed current with iso-potential plates is presented. The consumption of gases in the flow field channels, coupled to the electric potential and water content in the polymer membrane, is modeled in a two-dimensional slice from inlet to outlet and through the membrane. Both co-and counter-flowing air and fuel streams are considered, with attention paid to sensitivity of along-the-channel current density to inlet humidities, gas stream composition, and fuel and oxygen stoichiometries. The parameters describing the nonequilibrium kinetics of the membrane/catalyst interface are found to be fundamental to accurate fuel cell modeling. A new parameter which models nonequilibrium membrane water uptake rates is introduced. Four parameters, the exchange current, a membrane water transfer coefficient, an effective oxygen diffusivity, and an average membrane resistance, are fit to a subset of data and then held constant in subsequent runs which compare polarization curves, current density and membrane hydration distributions, water transfer, and stoichiometric sensitivity to the balance of the experimental data.

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In this study, the structural degradation of a polymer electrolyte membrane fuel cell (PEMFC) cathode catalyst layer due to carbon corrosion was investigated. To oxidize the catalyst carbon support, the PEMFC catalyst layer was subjected to a 30 h accelerated stress test that cycled the cathode potential from 0.1 to 1.5normalVRHE (where RHE denotes reversible hydrogen electrode) at 30 and 150 s intervals. Carbon dioxide release was measured in the gas exhaust to establish the rate and amount of carbon loss. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), scanning electron microscopy, and polarization analyses were completed to characterize and correlate the structural degradation of the catalyst layer to the PEMFC performance. The results showed a clear thinning of the cathode catalyst layer and the gas diffusion layer carbon sublayer and a reduction in the effective platinum surface area due to carbon support oxidation. The degradation of the cathode catalyst layer also altered the water management, as evidenced by an increase in the voltage losses associated with oxygen mass transport and catalyst layer ohmic resistance. There was an emphasis on the EIS measurement to further develop and verify this methodology for other degradation mechanisms.