Analytical Model for Pem Fuel Cell Concentration Impedance

Analytical model for concentration/pressure (zeta) impedance of the cathode side of a PEM fuel cell is developed. The model is based on transient oxygen mass transport equations through the gas - diffusion and cathode catalyst layers. Analytical solution for zeta - impedance is derived and the relation of zeta - impedance and regular cell impedance is obtained. In the limit of high oxygen consumption in the catalyst layer, simple equations for the static point of zeta impedance are derived. These equations allow one to estimate oxygen transport coefficients of the catalyst and gas diffusion layers from the static point of zeta - spectrum. Qualitative resemblance of the model and experimental zeta - spectra is demonstrated.