Numerical analysis on influence of surface structures of cathode catalyst layers on performance of polymer electrolyte fuel cells

Abstract

Because it is time-consuming to optimize the design of a cathode catalyst layer (CCL), a numerical simulation to predict the reaction and mass transport characteristics without trial and error is desirable. This study used numerical analysis to investigate how the mass transport occurring in CCLs with flat and three-dimensional (3D) structures influenced the performance. The simulations included the reconstruction of the CCLs and their electrochemical calculation using our multi-block model. The simulation results showed the reduction of the proton resistance in the ionomer was a factor in improving the performance in the 3D structure in comparison with the flat structure. An increasing aspect ratio of the 3D structure improved the cell performance and decreased the proton resistance in the ionomer. These results were due to the shortened conductive path of the protons from the polymer electrolyte membrane to the gas diffusion layer side surface in the 3D structure. Finally, the cell performance with an increase in the ionomer content was predicted. This numerical analysis made it possible to understand the reaction of the 3D structure and mass transport and predict ways to optimize the structural design to improve cell performance.