Adiabatic relaxation of convective-diffusive gas transport in a porous fuel cell electrode

The gas diffusion layer in the electrode of a proton exchange membrane fuel cell is a highly porous material which acts to distribute reactant gases u niformly to the active catalyst sites. We develop a mathematical model for ow of a multicomponent mixture of ideal gases in a highly porous electrode. The model is comprised of a porous medium equation for the evolution of th e gas mixture and a singularly perturbed convection-diffusion equation for the interspecies mass transfer within the mixture. The equations are couple d through nonlinear boundary conditions which describe consumption of react ants and generation of end products at the catalyst layer. Through a two-ti me-scale analysis, we derive a single reduced equation which captures the s low, diffusively driven, adiabatic relaxation to the steady state at each e lectrode. The asymptotic results are compared with one- and two-dimensional computations of the full system.