Modeling of local gas transport in catalyst layers of PEM fuel cells

A mathematical model focusing on local gas transport in a single carbon primary particle was developed by combining the classical agglomerate model with local gas transport in the vicinity of a Pt particle. Two local gas transport processes—gas transport through an ionomer thin film at Pt particles deposited on the surface of the carbon primary particle and gas transport through water at Pt particles deposited inside the carbon primary particle—were newly introduced. The model showed qualitative agreement with the experimentally measured gas transport resistance of catalyst layers with different effective Pt surface areas, which had not been captured by the classical agglomerate approach. The experimental data were fitted by significantly reducing the gas permeability for the local gas transport processes in the vicinity of the Pt surface, which was 1/4–1/20 of the permeability measured in the bulk materials. The corrections of gas permeability were all related to the local gas transport in the vicinity of the Pt surface, which implied the presence of a high energy barrier for reactant gas transport at ionomer/Pt and water/Pt interfaces. The influence of structural parameters of catalyst layers on the gas transport resistance was presented to provide a guideline toward the reduction of the gas transport resistance at low Pt loading. [Display omitted] •A mathematical model considering local gas transport in the vicinity of a Pt particle is developed.•The model can reproduce the experimental data which had not been captured by the classical agglomerate approach.•A guideline toward the reduction of the gas transport resistance at low Pt loading is proposed.