(181i) Molecular Dynamics Simulation of O2 Transport in Nafion

Polymer electrolyte membrane fuel cells (PEMFCs) are a viable energy source for small scale power generation. However, the power density of modern PEMFCs is still too low to provide adequate performance. Poor O₂ transport in the ionomer layer of the PEMFC adversely impacts power density. In this research, we use molecular dynamics simulations to explore the effect of ionomer chemistry on O₂ transport. Bulk calculations are used to quantify O₂ diffusivity, while thin-film calculations of ionomer on platinum catalyst are used to quantify O₂ solubility. Simulations show that the addition of bulky groups to ionomer backbones, and shorter ionomer side chains result in improved O₂ permeability. This is attributable to reduced ionomer crystallinity in the bulk phase and suppression of the formation of a dense ionomer layer in interfacial systems. These observations are corroborated by experiments.