MATHEMATICAL-MODEL OF A GAS-DIFFUSION ELECTRODE BONDED TO A POLYMER ELECTROLYTE

A mathematical model for an ion-exchange membrane attached to a gas-fed porous electrode is derived and discussed. The model is applied to simulate the oxygen electrode of a polymer-electrolyte fuel cell. Our discussion focuses on cell polarization characteristics, water transport, and catalyst utilization-all of which must be considered for fuel-cell design. Calculated polarization behavior is shown to compare favorably with published experimental data. Our results indicate that if the membrane maintains full saturation, its contribution to the total cell resistance is most significant at higher operating current densities (greater than 200 mA/cm2). Polarization resistance due to the oxygen reduction reaction appears to be important for all practical current densities. Water transport, driven by pressure and electric-potential forces, is shown to be a complicated function of the cell operating conditions. The utilization and distribution of noble-metal catalyst is discussed.