The role of the drying process and the Pt/C structure on the ionomer morphology of the catalyst layer

Abstract

The coarse-grained molecular dynamics evaporation simulation was performed in order to reproduce the formation process of the catalyst layer in the polymer electrolyte fuel cells (PEFCs). The molecular mechanisms of the drying process, solution composition, and Pt/C structures affecting the film morphology were clarified. The deposition of the advancing solidification front of ionomers produced by fast evaporation significantly affected the surface structure of the ionomer film. The ionomer sulfonate groups tended to migrate towards the hydrophilic Pt surface from carbon. The ionomer network was formed by connecting neighboring Pt particles as the I/C ratio increased. The position order of the lamellar-like ionomer film decreased as the I/C ratio increased. The ionomer coverage and roughness were determined by the Pt/C ratio and I/C ratio. Appropriate distribution of the Pt particles, the I/C ratio, and the drying methods were crucial for designing the catalyst interface to improve the proton transport network and utilization of the Pt particles.