Simulating Morphology and Degradation of PEMFC Cathode Catalyst Layers with Porous Carbon Supports: Part II: Effect of Ionomer and Relative Humidity on Catalyst Degradation

We present a physical degradation model which simulates the evolution of the cathode catalyst layer nanomorphology and associated catalyst surface area in the course of potential-induced ageing. By coupling to the morphology model featured in Part I, the effects of the pore, particle and ionomer distributions and resulting nanoscale interfaces in each individual material are taken into account. Specifically, the model discriminates between catalyst ageing on the support surface and inside primary pores of the support. For model validation, catalyst utilization data in terms of active surface area measured at varying relative humidity is used. These data are sensitive to a variety of electrode properties such as support porosity, catalyst loading and size and ionomer loading. Simulations are compared against data from 15 samples manufactured in-house using different materials and aged in different conditions. In-depth analysis of simulation results identifies the model as a valuable tool to establish a link between electrode composition and nanomorphology as well as between nanomorphology and expected degradation.