Fuel Cells Durability & Performance ---- Aarkstore Enterprise
This book provides an interdisciplinary review for fuel cell developers
, manufacturers and suppliers working in the fields of fuel cells materials, stacks, system design, fabrication, and testing. Important topics to be addressed include:
Factors Affecting Durability & Performance
Electrocatalysts - The Platinum Issue
Testing, Protocols, Balance of Plant
Beyond PEM
Membranes and MEAs
AUDIENCE :
Application Manager
Business Development Manager
Chemical Engineer
Chemist
Chief Technology Officer
Development Engineer
Director of Manufacturing
Director of Marketing
Director of Technology
Electrochemist
Manager for Test Engineering
President & CEO
Program Manager
R&D Chemist
R&D Engineer
Research Engineer
Research Scientist
Technology Development Manager
Vice President of Research
Vice President of Technology
Table of Contents :
CHAPTER 1
DOE Fuel Cell R&D Activities: Transportation, Stationary, and Portable Power Applications
Terry Payne, PhD, PE, Technology Development Manager, and Nancy Garland, PhD, Acting Fuel Cell Team Leader, Office of Hydrogen, Fuel Cells and Infrastructure Technologies, U.S. Department of Energy
The Department of Energys Hydrogen Program initiated new research and development projects aimed at reducing component cost and increasing stack durability and performance of transportation and stationary fuel cells. Updated progress in the Program including highlights from the new projects includes operation of a membrane electrode assembly over 7300 with voltage cycling. Market transformation activities in the Program such as forklifts for distribution centers and fuel cells for backup power will be discussed.
CHAPTER 2
FCV Development at Nissan - Current Status and Future Perspective
Kev Adjemian, Nissan Research Center, Nissan Motor Co., Ltd., Japan
Nissan Motor Company has recently developed their latest generation in-house stack which possesses many enhancements over the previous generation. Compared to the former stack, this design has doubled the power density and provides a longer lifetime while simultaneously reducing the overall cost. This has been accomplished with the development of an ultra-thin metal separator which has increased the maximum power by 40 kW, reaching a total of 130 kW. Additionally, the platinum usage has been halved which has resulted in both an increase in durability and a reduction of cost. Future research will be focused on additional enhancements of the stack and system in order to achieve FCV commercialization under the Nissan Green Program.
CHAPTER 3
Degradation of Gas Diffusion Media
Rod Borup, PhD, Institute for Hydrogen and Fuel Cell Research Fuel Cell Program Manager, Fuel Cell Team Leader, Los Alamos National Laboratory*
Gas Diffusion Layer (GDL) degradation over the lifetime of a PEMFC system can play an important role in the overall performance of the system. GDLs tend to show decreasing hydrophobicity during operational lifetimes, which change the fuel cells operating characteristics with respect to water removal and power density. Aging conditions vary the degree of GDL hydrophobicity loss, while exposure to impurities have been shown to both decrease and increase the hydrophobicity. To understand GDL degradation, we utilize a number of characterization methods, including measurements of surface energy, contact angle, pore size distribution, elemental analysis, FTIR, microscopy and in situ RH tests. *In collaboration with: J.Davey, LANL; D.Wood, Cabot Corp.
CHAPTER 4
An Inside Look at Degradation Pathways at a Polymer Electrolyte-Electrode Interface
Sanjeev Mukerjee, PhD, Professor, Director, Center for Renewable Energy Technology, Northeastern University
This chapter will provide an in-depth look at some of the most important degradation processes in PEM fuel cells based on H2 and direct fuel oxidation. Real life observations of degradation of ionomer/membranes, changes in interfacial structure, electrocatalyst deactivation, sintering will be discussed in the context of fuel cell operating variables. These include, overpotential, start up/shut down, temperature and relative humidity. Choice of materials, such as ionomer blends, membrane chemistry, catalyst support and nature of reaction centers will be juxtaposed with mechanistic perspective of their activity-lift time. This industry is in a state where there are increased expectations based on price and durability, an objective look at these demands in terms of what is achievable is paramount and the stated underlying goal of this presentation.
CHAPTER 5
The Stability of Platinum and Carbon in PEMFC Electrodes: Insight Obtained by Applying Electrochemical Methods
Frank A. de Bruijn, PhD, Unit Manager Hydrogen and Clean Fossil Fuels, Energy research Centre of the Netherlands (ECN), The Netherlands*
The stability of platinum on carbon electrodes is studied by measuring the mass of the electrodes at constant potential with high accuracy using a Quartz Crystal Microbalance and combining it with cyclic voltammetry at frequent intervals. The studies on platinum, carbon and platinum/carbon catalysts revealed that platinum can dissolve in less than 90 hours almost completely under conditions that correspond to hot open circuit. Under these conditions, carbon is slowly oxidized to quinone, and subsequently be oxidized to CO2. Lowering the temperature from 80C to 60C lead to a drastic decrease of the platinum dissolution rate; avoiding open-circuit conditions at high temperature could lead to a much longer lifetime of PEM fuel cells. *In collaboration with: V.A.T.Dam
CHAPTER 6
MEA Durability Test System (MEADS)
Marianne Rodgers, PhD, Lead Project Scientist, Florida Solar Energy Center; and Kevin Cooper, PhD, Principal Scientist, Scribner Associates Inc.*
Evaluation of membrane electrode assembly (MEA) durability in a fuel cell requires occupation of test stations for long periods of time. However, durability is important to investigate because, along with performance and cost, it is a limiting factor in proton exchange membrane fuel cell commercialization. The MEA Durability test System (MEADS) (Scribner Associates Inc.) is designed to subject MEAs in subscale test cells to fixed and stable operating conditions. It performs parallel testing of up to eight cells simultaneously. Each cell is operated with controlled reactant flows, temperature, and anode and cathode dew points. The MEADS software control system maintains uniform and continuous testing of multiple MEAs when taking any cell off-line, performing rapid cell purging with N2, changing reactants, or performing OCV and/or current monitoring. The use of MEADS will significantly facilitate MEA durability testing at the Florida Solar Energy Center. *In collaboration with: L.Bonville, D.Slattery, J.Fenton, Florida Solar Energy Center.
CHAPTER 7
Performance and Durability of an Open Flowfield Architecture Fuel Cell
Amedeo Conti, PhD, Manager of Electrochemical Technology Group, Nuvera Fuel Cells
Nuveras fuel cell technology employs a porous metal structure as the key component of the multifunctional bipolar plate/flowfield assembly. This design approach offers significant advantages in terms of enhanced mass transfer at high current densities, high efficiency at low load, and water/ice management during freeze starts. This presentation will discuss recent results obtained by Nuvera in the course of its durability investigation. Tests under different protocols will be presented including: quasi-steady state operation, fast cycles, and freeze starts. Correlation between data and models will be outlined. Different stack architectures will be compared, and Nuveras future direction will be highlighted.
CHAPTER 8
Ovonic Metal Hydride Fuel Cell (MHFC) - The Power of PEM at a Fraction of the Cost
Rob Privette, Director, Product Development, Ovonic Fuel Cell Company, A Subsidiary of Energy Conversion Devices
Ovonics MHFC provides stack power densities typical of stationary PEMFCs using non-platinum catalysts and inherently rapid alkaline chemistry kinetics. The cost is much lower than other competitive fuel cell technologies by avoiding Pt-group metals and using well-known industrial battery manufacturing. Instant start and low temperature capabilities are well-suited for portable and back-up applications. The durability of MHFC stacks has been dominated by cathode effects. New MO/carbon catalysts have shown stable performance indicating greatly enhanced durability by stabilization of the catalyst on the carbon substrate. Ovonic is also addressing carbon dioxide effect which can mechanically degrade the electrodes
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