The effects of non-uniform distribution of catalyst loading on polymer electrolyte membrane fuel cell performance

The catalyst layers are the most important part of the polymer electrolyte membrane (PEM) fuel cells, and the cell performance is highly related to its structure. The gas diffusion layers (GDLs) are also the essential components of the PEM fuel cell since the reactants should pass through these layers. Model prediction shows that electrical current in catalyst layer is non-uniform, influenced by the channel-land geometry. In addition, the compression effect of GDLs and water generation due to the electrochemical reaction may cause non-uniformity in porosity and, therefore, increases the non-uniformity in reactant concentration in GDL/catalyst layer interface. Simulation results suggest that non-uniform catalyst loading distribution in the catalyst layer will improve the performance of the whole catalyst layer by diminishing the variation in current density.In the present study the porosity variation in GDL is calculated by considering the applied pressure and the amount of water generated in the cell. The catalyst layer is described in terms of a spherical agglomerate model, and the effects of different mechanisms of water transport in membrane are investigated as well. The validity of the model is assessed by comparing the computed results with experimental data.