Durable High-Power Membrane Electrode Assemblies with Low-Pt-Loading

General Motors (GM) and other automotive membrane electrode assemblies (MEAs) developers have achieved very impressive beginning-of-life (BOL) performance using low-Pt-loading (0.05–0.1 mgPt/cm2) cathodes with PtCo alloys and thin (10–15 micron) membranes. Unfortunately, these MEAs are subject to life-limiting degradation during operation, especially at peak power, because of complex degradation mechanisms that are highly sensitive to the materials, MEA design, and fuel cell operating strategy. Specifically, power degradation of the cathode occurs via Pt and Co dissolution as well as deterioration of O2 transport properties. Additionally, thin membranes are subject to failure due to manufacturing defects in the adjacent gas diffusion media and electrodes and the formation of membrane-attacking radical species caused by high gas crossover. This project is designed to systematically study these degradation phenomena in a MEA, applying and extending diagnostic and modeling tools available at GM and its partners.

The project approach is based on our understanding that there is substantial opportunity to select operating conditions and voltage waveforms to reduce life-limiting electrode and membrane degradation rates. In this project, we intend to map the impact of operating conditions on MEA durability for proton exchange membrane fuel cells. This will be achieved by systematic durability studies relying on advanced characterization tools and degradation mechanism model development and validation. Specifically, the project approach is to improve MEA performance and durability by executing the following work elements: (1) integrating the best-in-class materials to generate a MEA in Budget Period (BP) 1, (2) incorporating systematic durability studies to assess the impact of operating conditions on MEA life, (3) conducting extensive postmortem characterization of MEAs to provide mechanistic understanding of MEA degradation along with developing and validating models to predict electrode and membrane degradation, and (4) recommending benign yet realistic operating conditions to extend durability of the MEA past 5,000 h for the DOE 2020 durability target.