Three dimensional proton exchange membrane fuel cell cathode model using a modified agglomerate approach based on discrete catalyst particles

The spherical agglomerate model represents the most detailed description of the PEM fuel cell catalyst layer as it accounts for both micro and macroscale transport phenomena. The usual approach with the classical spherical agglomerate model is to couple the homogenous mixture assumption for the agglomerate core to its idealized spherical geometry to obtain an analytical solution which is easily incorporated within a macroscale model. In this study, we incorporate numerical results from a modified agglomerate model based on discrete platinum particles [33] to create a more physically realistic 3D macroscale model for the PEM fuel cell cathode catalyst layer. Results from the 3D cathode model based on the modified particle approach are compared with the classical model and the macro-homogenous model. We find that, similar to the classical approach, the modified 3D model is able to reproduce previously reported trends for reactant, reaction rate, and overpotential distributions, whereas the macro-homogenous model fails to predict mass transport limitations properly. It is also shown that, unlike the classical approach, the modified 3D model is able to accurately predict the effect of Pt loading in the diffusion-loss region.