Modeling the impact of Pt-particle position with respect of the C-support microstructure on PEMFC performance

A cathode catalyst layer model that accounts for the position of the Pt particles on the carbon support structure is proposed. By integrating a discrete Pt particle size distribution with a classification that distinguishes between Pt particles located on the support surface (Ptouter) and those embedded within the pore structure (Ptinner), we can identify distinct loss mechanisms. The model addresses additional mass transport and proton accessibility issues for Ptinner due to extended diffusion paths and reduced proton conduction within the ionomer-free primary pores of the carbon support. Conversely, Ptouter experiences ionomer poisoning from the adsorption of sulfonic acid groups and the densification of ionomer molecules, creating a compact layer over the Pt particles. The influence of carbon support type such as high and low surface area carbon on the cell performance is simulated and discussed for different scenarios such as particle location classification and relative humidity. A parametric study is conducted to elucidate the complex interactions between the contributions of current generation from Ptinner and Ptouter, alongside an analysis of their impact on mass activity and mass transport resistance.