Analysis of the oxygen scattering behaviour on ionomer surface in catalyst layer of PEFC

Abstract

Mass transport significantly affects the reaction efficiency of polymer electrolyte fuel cells. In particular, the oxygen transport in catalyst layers is important for the improvement of its efficiency. However, the mechanism of oxygen scattering on ionomer surface, which is one of the dominant factors of transport phenomena, has not been clarified. Therefore, we analyzed the oxygen scattering behaviour on ionomer surface using molecular dynamics simulation. Oxygen molecules are impinged to ionomer surface with different incident energies and angles. According to the total energy of oxygen molecule, the trajectories of oxygen molecules are classified into trapping or scattering. The trapping probability of oxygen molecule on ionomer surface decreases as the normal component of the incident energy increases. Oxygen molecules with low normal incident energy get energy during the gas–surface interaction on the surface and desorb from the surface. The number of collisions with the surface does not affect the energy transfer between oxygen molecule and ionomer surface.