Molecular Dynamics Simulations of Cerium Ion Transport Phenomena in Polymer Electrolyte Membranes of Polymer Electrolyte Fuel Cells

Abstract

We analyzed the transport properties of cerium ions, which are added to improve the chemical durability of a polymer electrolyte membrane (PEM), using molecular dynamics simulations. For the analysis, the diffusion coefficient of cerium ions and the radial distribution function around sulfonic acid groups were obtained. The results show that at low water content, the diffusion coefficient is small because of the direct coordination of cerium ions to the sulfonic acid groups due to the small number of water molecules around the sulfonic acid groups. At high water content, water molecules gather around the sulfonic acid groups, and cerium ions are coordinated far from the sulfonic acid groups, resulting in a weaker binding than at low water content and an increase in the diffusion coefficient of cerium ions.