Microscale simulations of reaction and mass transport in cathode catalyst layer of polymer electrolyte fuel cell

The resistance of the cathode oxygen reduction reaction in polymer electrolyte fuel cells must be reduced for improving the performance. Therefore, it is important to thoroughly understand the relationship between the heterogeneous structures and the cell performance. However, it is difficult to obtain such an understanding using experimental approaches and typical uniform porous simulations. In this study, numerical analysis was used to simulate a three-dimensional catalyst layer (CL) with carbon black (CB) aggregate structures and ionomer coating models, and a cathode reaction and mass transport simulation model incorporating the heterogeneous structure was developed. Moreover, the relationship between the electrode structure and the cell performance, including the reaction distribution and output performance, was examined. The current density distribution depended on the CB structure and ionomer adhesion shape. From the viewpoint of enhancing both the Pt utilization and the mass transport performance, an adequate heterogeneous pore structure in the CL is necessary. These results were used to determine the optimal material properties for the high performance cell. • Simulation model in cathode catalyst layer with 3D structure was developed. • Heterogeneous structure with carbon black and ionomer was simulated. • Ionomer adhesion affect mass transport, and it cause reaction distribution. • Local reaction on Pt surface was changed to bi-modal distribution by agglomerate. • Effective Pt utilization in cathode was estimated by this simulation.