A Modified Agglomerate Model with Discrete Catalyst Particles for the PEM Fuel Cell Catalyst Layer

The spherical agglomerate model for the PEM fuel cell catalyst layer is modified by representing the catalyst as a distribution of discrete Pt particles. The modified approach incorporates local mass diffusion effects and electrochemical reactions at the catalyst particle level. The influence of randomly distributed catalyst particles in the agglomerate is investigated for the first time. Unlike the classical approach, the discrete particle approach provides physically realistic results for the diffusion-limited region when the catalyst loading is varied. Polarization curves obtained with the discrete particle approach show that for a spherical agglomerate (i) catalyst utilization can be increased by concentrating the catalyst particles near the agglomerate wall, and (ii) a peripheral distribution of fewer particles can perform better than a uniform distribution of more numerous particles.