Investigation of Effect of Platinum Nanoparticle Shape on Oxygen Transport in PEMFC Catalyst Layer Using Molecular Dynamics Simulation

Abstract

For the widespread adoption of polymer electrolyte membranefuelcells, it is compelling to investigate the influence of the Pt nanoparticleshapes on the electrocatalytic activity. In this study, a catalystlayer was modeled by incorporating four types of Pt nanoparticles:tetrahedron, cube, octahedron, and truncated octahedron, to investigatethe relationship between the shapes of the nanoparticles and theirimpact on the oxygen transport properties using molecular dynamicssimulations. The results of our study reveal that the free volume,which has a substantial impact on the oxygen transport properties,exhibited higher values in the sequence of the tetrahedron, cube,octahedron, and truncated octahedron model. The difference in freevolume following the formation of less dense ionomers was also relatedto the surface adsorption of Pt nanoparticles. Consequently, thisled to an improved facilitation of oxygen transport. To clarify thedependence of the oxygen transport on the shape of the Pt nanoparticlesin detail, we analyzed the structural properties of different Pt shapes by dividing the Pt nanoparticle regions into corners, edges, andfacets. Examination of the structural properties showed that the structureof the ionomer depended not only on the shape of the Pt nanoparticlesbut also on the number of corners and edges in the upper and sideregions of the Pt nanoparticles.