Effect of Carbon Support Characteristics on Fuel Cell Durability in Accelerated Stress Testing

Support carbon corrosion has been considered a major degradation mechanism impacting the fuel cell performance. A support corrosion accelerated stress test (AST) that consists of potential cycling between 1.0 V and 1.5 V at 35 degrees C and 70 degrees C, respectively has been performed at Ford to evaluate the durability of five membrane electrode assemblies (MEAs), which were made from suppliers' catalyst coated membranes (CCMs) containing different carbon supports, catalyst loadings and compositions, ionomer/carbon (I/C) ratios, and ionomer equivalent weights (EWs). The carbon corrosion behaviors from these carbon supports were studied focusing on the carbon loss, voltage degradation at a fixed current density, electrochemical surface area (ECSA) loss, catalyst layer thickness reduction, catalyst dispersion change, and electrode porosity change after AST, with the aid of comprehensive post-mortem failure analysis. Although the MEAs performed differently in these characterizations, the cumulative percentage carbon loss became quite the same for four high-surface-area carbon supports at 70 degrees C. This is probably due to the strong direct oxidation of carbon at elevated temperature and high-potential window as long as carbon is available. Graphitized carbon presented outstanding support durability at high temperature than high-surface-area carbons. However, as temperature decreased, this advantage was no longer obvious. A database for carbon corrosion with failure analysis has been established in this work to support material and system strategy developments.

Automated summary

Support carbon corrosion is a major degradation mechanism affecting fuel cell performance. An accelerated stress test was conducted at Ford to evaluate the durability of five MEAs made from CCMs containing different carbon supports, catalyst loadings, compositions, I/C ratios, and ionomer EWs. The study focused on carbon loss, voltage degradation, ECSA loss, catalyst layer thickness reduction, catalyst dispersion change, and electrode porosity change post-AST.