Download or read book Experimental Methods and Mathematical Models to Examine Durability of Polymer Electrolyte Membrane Fuel Cell Catalysts written by Shankar Raman Dhanushkodi and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton exchange membrane fuel cells (PEMFC) are attractive energy sources for power trains in vehicles because of their low operating temperature that enables fast start-up and high power densities. Cost reduction and durability are the key issues to be solved before PEMFCs can be successfully commercialized. The major portion of fuel cell cost is associated with the catalyst layer which is typically comprised of carbon-supported Pt and ionomer. The degradation of the catalyst layer is one of the major failure modes that can cause voltage degradation and limit the service life of the fuel cell stack during operation. To develop a highly durable and better performing catalyst layer, topics such as the causes for the degradation, modes of failure, different mechanisms and effect of degradation on fuel cell performance must be studied thoroughly. Key degradation modes of catalyst layer are carbon corrosion and Pt dissolution. These two modes change the electrode structure in the membrane electrode assembly (MEA) and result in catalyst layer thinning, CO2 evolution, Pt deposition in the membrane and Pt agglomeration. Alteration of the electrode morphology can lead to voltage degradation. Accelerated stress tests (ASTs) which simulate the conditions and environments to which fuel cells are subject, but which can be completed in a timely manner, are commonly used to investigate the degradation of the various components. One of the current challenges in employing these ASTs is to relate the performance loss under a given set of conditions to the various life-limiting factors and material changes. In this study, various degradation modes of the cathode catalyst layer are isolated to study their relative impact on performance loss _Fingerprints' of identifiable performance losses due to carbon corrosion are developed for MEAs with 0.4 mg cm−2 cathode platinum loadings. The fingerprint is used to determine the extent of performance loss due to carbon corrosion and Pt dissolution in cases where both mechanisms operate. This method of deconvoluting the contributions to performance loss is validated by comparison to the measured performance losses when the catalyst layer is subjected to an AST in which Pt dissolution is predominant. The limitations of this method iv are discussed in detail. The developed fingerprint suggests that carbon loss leading to CO2 evolution during carbon corrosion ASTs contributes to performance loss of the cell. A mechanistic model for carbon corrosion of the cathode catalyst layer based on one appearing in the literature is developed and validated by comparison of the predicted carbon losses to those measured during various carbon corrosion ASTs. Practical use of the model is verified by comparing the predicted and experimentally observed performance losses. Analysis of the model reveals that the reversible adsorption of water and subsequent oxidation of the carbon site onto which water is adsorbed is the main cause of the current decay during ASTs. Operation of PEM fuel cells at higher cell temperatures and lower relative humidities accelerates Pt dissolution in the catalyst layer during ASTs. In this study, the effects of temperature and relative humidity on MEA degradation are investigated by applying a newly developed AST protocol in which Pt dissolution is predominant and involves the application of a potentiostatic square-wave pulse with a repeating pattern of 3s at 0.6 V followed by 3s at 1.0 V. This protocol is applied at three different temperatures (40°C, 60°C and 80°C) to the same MEA. A diagnostic signature is developed to estimate kinetic losses by making use of the effective platinum surface area (EPSA) obtained from cyclic voltammograms. The analysis indicates that performance degradation occurs mainly due to the loss of Pt in electrical contact with the support and becomes particularly large at 80°C. This Pt dissolution AST protocol is also investigated at three different relative humidities (100%, 50% and 0%). Electrochemical impedance spectroscopy measurements of the MEAs show an increase in both the polarization and ohmic resistances during the course of the AST. Analysis by cyclic voltammetry shows a slight increase in EPSA when the humidity increases from 50% to 100%. The proton resistivity of the ionomer measured by carrying out impedance measurements on MEAs with H2 being fed on the anode side and N2 on the cathode side is found to increase by the time it reaches its end-of-life state when operated under 0 % RH conditions.
Download or read book Modeling and Diagnostics of Polymer Electrolyte Fuel Cells written by Ugur Pasaogullari and published by Springer Science & Business Media. This book was released on 2010-07-23 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume, presented by leading experts in the field, covers the latest advances in diagnostics and modeling of polymer electrolyte fuel cells, from understanding catalyst layer durability to start-up under freezing conditions.
Download or read book Polymer Electrolyte Fuel Cell Durability written by Felix N. Büchi and published by Springer Science & Business Media. This book was released on 2009-02-08 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers a significant number of R&D projects, performed mostly after 2000, devoted to the understanding and prevention of performance degradation processes in polymer electrolyte fuel cells (PEFCs). The extent and severity of performance degradation processes in PEFCs were recognized rather gradually. Indeed, the recognition overlapped with a significant number of industrial dem- strations of fuel cell powered vehicles, which would suggest a degree of technology maturity beyond the resaolution of fundamental failure mechanisms. An intriguing question, therefore, is why has there been this apparent delay in addressing fun- mental performance stability requirements. The apparent answer is that testing of the power system under fully realistic operation conditions was one prerequisite for revealing the nature and extent of some key modes of PEFC stack failure. Such modes of failure were not exposed to a similar degree, or not at all, in earlier tests of PEFC stacks which were not performed under fully relevant conditions, parti- larly such tests which did not include multiple on–off and/or high power–low power cycles typical for transportation and mobile power applications of PEFCs. Long-term testing of PEFCs reported in the early 1990s by both Los Alamos National Laboratory and Ballard Power was performed under conditions of c- stant cell voltage, typically near the maximum power point of the PEFC.
Download or read book Experimental Methods and Data Analyses for Polymer Electrolyte Fuel Cells written by and published by . This book was released on 2005 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book PEM Fuel Cell Catalyst Degradation Mechanism and Mathematical Modeling written by Wu Bi and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Durability of carbon-supported platinum nanoparticle is one of the limiting factors for PEM fuel cell commercial applications. In our research work, we applied both experimental and mathematical simulative tools to study the mechanisms of Pt/C catalyst degradation. An accelerated catalyst degradation protocol by cycling the cathode potential in a square-wave profile was applied to study the losses of cell performances, catalyst ORR activity, and Pt active surface areas. Post-mortem analyses of cathode Pt particle size by X-ray diffraction and platinum distributions in CCMs by SEM/EDS were also conducted. Increased cell temperature and relative humidity was found to accelerate the cathode catalyst degradation. High membrane water contents or abundant water/ionic channels within the polymer electrolyte were believed to accelerate Pt ion transport and cathode degradation. After degradation tests, significant amount of Pt loss into the membrane forming a Pt "band" was observed through cathode platinum dissolution and chemical reduction of soluble Pt ions by permeated hydrogen from the anode. Platinum deposition was confirmed at a location where the permeated hydrogen and oxygen had the complete catalytic combustion over the deposited Pt clusters/particles as the catalyst. A cathode degradation model was built including the processes of platinum oxidation, dissolution/replating, diffusion of Pt ions and Pt band formation in electrolyte. A simplified bi-modal particle size distribution was applied with equal numbers of small and large type particles uniformly distributed in the cathode initially. Processes of Pt mass exchange between two types of particles were demonstrated to cause the overall particle growth. This was due to the particle size effect that platinum dissolution from the small type particles and replating of Pt ions onto the large particles was favored. Parametric study found the increased upper cycling potential was the dominated factor to accelerate the catalyst degradation. Also high frequency of potential cycle and low surface oxide coverage accelerated the degradation rate. Pt dissolution and oxidation processes in perchloric acid were preliminary investigated, and both chemical and electrochemical processes of oxidation and dissolution were believed to be involved under closed-circuit fuel cell conditions with oxygen presence at cathode.
Download or read book Polymer Electrolyte Fuel Cell Degradation written by Matthew M. Mench and published by Academic Press. This book was released on 2012 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt: For full market implementation of PEM fuel cells to become a reality, two main limiting technical issues must be overcome- cost and durability. This cutting-edge volume directly addresses the state-of-the-art advances in durability within every fuel cell stack component. [...] chapters on durability in the individual fuel cell components -- membranes, electrodes, diffusion media, and bipolar plates -- highlight specific degradation modes and mitigation strategies. The book also includes chapters which synthesize the component-related failure modes to examine experimental diagnostics, computational modeling, and laboratory protocol"--Back cover.
Download or read book Modeling Simulation and Experimental Validation of Polymer Electrolyte Membrane Fuel Cells and Alkaline Membrane Fuel Cells written by Lauber De Souza Martins and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Fuel cell technology is currently showing itself as a promising alternative for clean energy production due to its high efficiency and minimum environmental impact. However, its high cost is still a challenge that prevents this technology of being extensively used. A new conception and optimization are a natural alternative to reduce cost and make fuel cells increasingly more attractive for power generation. Geometric design, including the internal structure and external shape, considerably affect the thermal, fluid and electrochemical characteristics, which determines the polarization curves as well as the thermal and power inertia. In order to predict the response of fuel cells according to the variation of manufacturing materials, physical properties, operating and design parameters, a reliable simulation model (and computationally fast) is necessary. A simplified and comprehensive mathematical model for a polymer electrolyte membrane fuel cell (PEMFC) is developed and experimentally validated. Numerical results are obtained with the model for an existing set of ten commercial unit PEM fuel cells. The computed polarization and power curves are directly compared to the experimentally measured ones with good qualitative and quantitative agreement. Alkaline Membrane Fuel Cell (AMFC) is a recently developed fuel cell type, which has shown good experimental results. A mathematical model for a single AMFC with square section and fixed volume is introduced. The model is based on electrochemical principles, conservation of mass, momentum, energy and species. It also takes into account pressure drop in the gas channels and gradient of temperature with respect to space in the flow direction. The simulation results comprise temperature, net power, polarization curves and gas channels pressure drop. The computed temperature, polarization and power curves for AMFC are directly compared to the experimentally measured ones (using a prototype built in laboratory) with good qualitative and quantitative agreement. Therefore, the model is expected to be a useful tool for PEMFC and AMFC design and optimization.
Download or read book PEM Fuel Cells written by Frano Barbir and published by Academic Press. This book was released on 2012-09-25 with total page 537 pages. Available in PDF, EPUB and Kindle. Book excerpt: Demand for fuel cell technology is growing rapidly. Fuel cells are being commercialized to provide power to buildings like hospitals and schools, to replace batteries in portable electronic devices, and as replacements for internal combustion engines in vehicles. PEM (Proton Exchange Membrane) fuel cells are lighter, smaller, and more efficient than other types of fuel cell. As a result, over 80% of fuel cells being produced today are PEM cells. This new edition of Dr. Barbir's groundbreaking book still lays the groundwork for engineers, technicians and students better than any other resource, covering fundamentals of design, electrochemistry, heat and mass transport, as well as providing the context of system design and applications. Yet it now also provides invaluable information on the latest advances in modeling, diagnostics, materials, and components, along with an updated chapter on the evolving applications areas wherein PEM cells are being deployed. Comprehensive guide covers all aspects of PEM fuel cells, from theory and fundamentals to practical applications Provides solutions to heat and water management problems engineers must face when designing and implementing PEM fuel cells in systems Hundreds of original illustrations, real-life engineering examples, and end-of-chapter problems help clarify, contextualize, and aid understanding
Download or read book Comprehensive Consistent and Systematic Approach to the Mathematical Modeling of PEM Fuel Cells written by Jeffrey Baschuk and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polymer Electrolyte Fuel Cells written by Alejandro A. Franco and published by CRC Press. This book was released on 2016-04-19 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the recent research progress on the fundamental understanding of the materials degradation phenomena in PEFC, for automotive applications. On a multidisciplinary basis, through contributions of internationally recognized researchers in the field, this book provides a complete critical review on crucial scientific topics related
Download or read book Fuel Cells and Hydrogen Production written by Timothy E. Lipman and published by Springer. This book was released on 2018-10-05 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The expected end of the “oil age” will lead to increasing focus and reliance on alternative energy conversion devices, among which fuel cells have the potential to play an important role. Not only can phosphoric acid and solid oxide fuel cells already efficiently convert today’s fossil fuels, including methane, into electricity, but other types of fuel cells, such as polymer electrolyte membrane fuel cells, have the potential to become the cornerstones of a possible future hydrogen economy. This handbook offers concise yet comprehensive coverage of the current state of fuel cell research and identifies key areas for future investigation. Internationally renowned specialists provide authoritative introductions to a wide variety of fuel cell types and hydrogen production technologies, and discuss materials and components for these systems. Sustainability and marketing considerations are also covered, including comparisons of fuel cells with alternative technologies.
Download or read book Polymer Electrolyte Membrane and Direct Methanol Fuel Cell Technology written by Christoph Hartnig and published by Woodhead Pub Limited. This book was released on 2012 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: The promising forms of polymer electrolyte membrane fuel cells and direct methanol fuel cells technology have attracted intense worldwide commercialization research and development efforts.
Download or read book PEM Fuel Cell Failure Mode Analysis written by Haijiang Wang and published by CRC Press. This book was released on 2011-08-25 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: PEM Fuel Cell Failure Mode Analysis presents a systematic analysis of PEM fuel cell durability and failure modes. It provides readers with a fundamental understanding of insufficient fuel cell durability, identification of failure modes and failure mechanisms of PEM fuel cells, fuel cell component degradation testing, and mitigation strategies against degradation. The first several chapters of the book examine the degradation of various fuel cell components, including degradation mechanisms, the effects of operating conditions, mitigation strategies, and testing protocols. The book then discusses the effects of different contamination sources on the degradation of fuel cell components and explores the relationship between external environment and the degradation of fuel cell components and systems. It also reviews the correlation between operational mode, such as start-up and shut-down, and the degradation of fuel cell components and systems. The last chapter explains how the design of fuel cell hardware relates to failure modes. Written by international scientists active in PEM fuel cell research, this volume is enriched with practical information on various failure modes analysis for diagnosing cell performance and identifying failure modes of degradation. This in turn helps in the development of mitigation strategies and the increasing commercialization of PEM fuel cells.
Download or read book Mathematical Modeling and Experimental Validation of Thin Low Platinum Content and Functionally Graded Cathode Catalyst Layers written by Kailyn Domican and published by . This book was released on 2014 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Low catalyst content remains a key requirement for the commercialization of polymer electrolyte fuel cells (PEFCs) into the energy, transportation, and material handling sectors. Understanding the fundamental phenomena reducing fuel cell performance at various stages of operation play a major role in PEFC optimization and reducing catalyst content. In this thesis, high performance PEFCs with low to moderate Pt loadings (27 - 112 [mu]gPt/cm2) have been fabricated using inkjet printing. To better understand thin low Pt content electrodes the PEFCs are tested at various back pressures, relative humidity, and oxygen partial pressures. The characterized PEFCs are then simulated using OpenFCST, an open-source FEM based fuel cell simulation framework, to aid in the investigation of key performance limiting phenomena. The simulations are obtained using a macro-homogeneous, non-isothermal MEA model where a multi-step reaction kinetics describes the oxygen reduction reaction. The model is then validated against the experimental Pt loading, ionomer loading, and oxygen partial pressure study. The successfully validated model highlighted key performance limitations between low Pt content and conventional (400 [mu]gPt/cm2) loading electrodes, while also highlighting the possible phenomena dictating ionomer and oxygen partial pressure performance. A mathematical model is also developed allowing the simulation of functionally graded electrodes. The model is then used to aid experimental design. To validate the new model two functionally graded ionomer electrodes are fabricated, characterized, and compared to the simulated results.
Download or read book Polymer Electrolyte Fuel Cells written by Michael Eikerling and published by CRC Press. This book was released on 2014-09-23 with total page 567 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides a systematic and profound account of scientific challenges in fuel cell research. The introductory chapters bring readers up to date on the urgency and implications of the global energy challenge, the prospects of electrochemical energy conversion technologies, and the thermodynamic and electrochemical principles underlying the op
Download or read book Proton Exchange Membrane Fuel Cells written by Alhussein Albarbar and published by Springer. This book was released on 2017-11-17 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book examines the characteristics of Proton Exchange Membrane (PEM) Fuel Cells with a focus on deriving realistic finite element models. The book also explains in detail how to set up measuring systems, data analysis, and PEM Fuel Cells’ static and dynamic characteristics. Covered in detail are design and operation principles such as polarization phenomenon, thermodynamic analysis, and overall voltage; failure modes and mechanisms such as permanent faults, membrane degradation, and water management; and modelling and numerical simulation including semi-empirical, one-dimensional, two-dimensional, and three-dimensional models. It is appropriate for graduate students, researchers, and engineers who work with the design and reliability of hydrogen fuel cells, in particular proton exchange membrane fuel cells.
Download or read book PEM Fuel Cell Electrocatalysts and Catalyst Layers written by Jiujun Zhang and published by Springer Science & Business Media. This book was released on 2008-08-26 with total page 1147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton exchange membrane (PEM) fuel cells are promising clean energy converting devices with high efficiency and low to zero emissions. Such power sources can be used in transportation, stationary, portable and micro power applications. The key components of these fuel cells are catalysts and catalyst layers. “PEM Fuel Cell Electrocatalysts and Catalyst Layers” provides a comprehensive, in-depth survey of the field, presented by internationally renowned fuel cell scientists. The opening chapters introduce the fundamentals of electrochemical theory and fuel cell catalysis. Later chapters investigate the synthesis, characterization, and activity validation of PEM fuel cell catalysts. Further chapters describe in detail the integration of the electrocatalyst/catalyst layers into the fuel cell, and their performance validation. Researchers and engineers in the fuel cell industry will find this book a valuable resource, as will students of electrochemical engineering and catalyst synthesis.
