Final Project Report: Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

Abstract

The overall objectives of this project were to improve the understanding of the design space of fuel cell materials and components and to recommend degradation mitigation strategies that facilitate the achievement of the 2020 technical targets. The deliverables from this project to the public, fuel cell community, and DOE are an open-source code fuel cell performance and durability model including a user-guide for dissemination and use within the public domain, and catalyst layer performance and durability correlations with identification of the design spaces relevant to improved durability.The project was led by Ballard Material Products via a direct subcontract to Ballard Power Systems and included critical contributions from the other subcontractors: Georgia Institute of Technology, Los Alamos National Laboratory, Michigan Technical University, Queen's University/University of Calgary, and the University of New Mexico. Ballard's work, which encompassed the development of the performance and degradation models as well as experimental investigation for model validation and the correlation/durability window development, was carried out at Ballard Power Systems' facility in Burnaby, B.C., Canada.Ballard recognizes the significant contribution made by each of the project collaborators and their respective team members. As well, Ballard recognizes the support provided from the DOE project managers, Dr. David Peterson and Kathi Epping Martin, and the project technical advisor, Dr. John Kopasz.The work was funded by the U.S. Department of Energy, Energy Efficiency and Renewable Energy. DE-EE0000466Ballard Material Products Inc. Chapter IPage iii EXECUTIVE SUMMARYThe durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications that target operational lifetimes of 5,000 hours and 40,000 hours by 2015, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifying the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different structural compositions and under different fuel cell conditions remains an area not well understood.The focus of this project was to address catalyst durability by using a dual path approach that coupled an extensive range of experimental analysis and testing with a multi-scale modeling approach. With this, the major technical areas/issues of catalyst and catalyst layer performance and durability that were addressed are:1. Catalyst and ca...

Statistical Simulation of the Performance and Degradation of a PEMFC Membrane Electrode Assembly

“…Improvements in the beginning of life (BOL) performance and load-cycle durability of the membrane electrode assembly (MEA) continue to be key areas of focus for PEM fuel cells (1), for both research and engineering development. Specifically, reductions in the platinum loading, while maintaining performance and durability are key aspects to meeting the cost targets necessary for commercialization.…”

Performance, Degradation and Structural Changes Associated with Pt Cathode Catalyst Layer Design

“…While over the past few years significant progress was made in identifying catalyst degradation mechanisms and key parameters that influence the degradation rates, many gaps in the understanding of the driving mechanisms and acceleration for different catalyst layer compositions still remain. Recent publication in this area point to the importance of understanding the impact of catalyst layer structure on fuel cell performance and durability [1][2][3][4][5] . In this study, the impact of various compositional variables, i.e.…”

Trading Off Initial PEM Fuel Cell Performance versus Voltage Cycling Durability for Different Carbon Support Morphologies

“…typically determined with 1 bar H 2 /O 2 partial pressures at 0.9 V) and the oxygen transport resistance (R O total 2 ), are functions of the roughness factor and are not affected independently by the aging procedure itself, as the Pt surface area loss proceeds via the same degradation mechanisms (Pt loss into the membrane/ionomer phase and Pt growth via Ostwald ripening). 24 Such a fixed relationship between the cell performance and the rf was further extended to Pt/ Vulcan electrodes that were voltage-cycled at various relative humidities and cathode gases. 25 As these voltage loss contributions are also known to be highly affected by the catalyst morphology, each specific catalyst with a given carbon support morphology, platinum weight fraction (wt% Pt ), and Pt particle location (i.e., whether mostly external or internal of the carbon support) would exhibit an individual, characteristic correlation.…”