Download or read book Concentration Effects of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Activity for Three Platinum Catalysts written by and published by . This book was released on 2014 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: A rotating disk electrode (RDE) along with cyclic voltammetry (CV) and linear sweep voltammetry (LSV), were used to investigate the impact of two model compounds representing degradation products of Nafion and 3M perfluorinated sulfonic acid membranes on the electrochemical surface area (ECA) and oxygen reduction reaction (ORR) activity of polycrystalline Pt, nano-structured thin film (NSTF) Pt (3M), and Pt/Vulcan carbon (Pt/Vu) (TKK) electrodes. ORR kinetic currents (measured at 0.9 V and transport corrected) were found to decrease linearly with the log of concentration for both model compounds on all Pt surfaces studied. Ultimately, model compound adsorption effects on ECA were more abstruse due to competitive organic anion adsorption on Pt surfaces superimposing with the hydrogen underpotential deposition (HUPD) region.
Download or read book Adsorption Characteristics of Polymer Electrolyte Membrane Chemical Degradation Products and Their Impact on Oxygen Reduction Reaction Activity for Platinum Catalysts written by Jason M. Christ and published by . This book was released on 2014 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Impact of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Reaction Activity for Platinum Electrocatalysts written by and published by . This book was released on 2014 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The impact of model membrane degradation compounds on the relevant electrochemical parameters for the oxygen reduction reaction (i.e. electrochemical surface area and catalytic activity), was studied for both polycrystalline Pt and carbon supported Pt electrocatalysts. Model compounds, representing previously published, experimentally determined polymer electrolyte membrane degradation products, were in the form of perfluorinated organic acids that contained combinations of carboxylic and/or sulfonic acid functionality. Perfluorinated carboxylic acids of carbon chain length C1 - C6 were found to have an impact on electrochemical surface area (ECA). The longest chain length acid also hindered the observed oxygen reduction reaction (ORR) performance, resulting in a 17% loss in kinetic current (determined at 0.9 V). Model compounds containing sulfonic acid functional groups alone did not show an effect on Pt ECA or ORR activity. Lastly, greater than a 44% loss in ORR activity at 0.9V was observed for diacid model compounds DA-Naf (perfluoro(2-methyl-3-oxa-5-sulfonic pentanoic) acid) and DA-3M (perfluoro(4-sulfonic butanoic) acid), which contained both sulfonic and carboxylic acid functionalities.
Download or read book PEM Water Electrolysis written by Dmitri Bessarabov and published by Academic Press. This book was released on 2018-08-04 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: PEM Water Electrolysis, a volume in the Hydrogen Energy and Fuel Cell Primers series presents the most recent advances in the field. It brings together information that has thus far been scattered in many different sources under one single title, making it a useful reference for industry professionals, researchers and graduate students. Volumes One and Two allow readers to identify technology gaps for commercially viable PEM electrolysis systems for energy applications and examine the fundamentals of PEM electrolysis and selected research topics that are top of mind for the academic and industry community, such as gas cross-over and AST protocols. The book lays the foundation for the exploration of the current industrial trends for PEM electrolysis, such as power to gas application and a strong focus on the current trends in the application of PEM electrolysis associated with energy storage. Presents the fundamentals and most current knowledge in proton exchange membrane water electrolyzers Explores the technology gaps and challenges for commercial deployment of PEM water electrolysis technologies Includes unconventional systems, such as ozone generators Brings together information from many different sources under one single title, making it a useful reference for industry professionals, researchers and graduate students alike
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 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.
Download or read book Improving Oxygen Reduction Reaction Catalysts for Polymer Electrolyte Membrane Fuel Cells written by Jarrid A. Wittkopf and published by . This book was released on 2017 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer electrolyte membrane fuel cells include proton exchange membrane fuel cells (PEMFCs) and hydroxide exchange membrane fuel cells (HEMFCs). PEMFCs use a proton conducting electrolyte, generating an acidic environment, while HEMFCs employ a hydroxide conducting electrolyte, providing a basic environment. For both types of fuel cells, the oxygen reduction reaction (ORR) at the cathode is sluggish and controls the fuel cell performance. Therefore, this thesis focuses on improving ORR catalyst activity and durability. ☐ PEMFCs, the more mature technology, have been commercially implemented in fuel cell cars like the Toyota Mirai and Honda Clarity. However, PEMFCs are expensive because they require a large amount of platinum (Pt) catalyst to overcome the ORR overpotential and the rapid catalyst degradation caused by the acidic operating environment. Current PEMFCs use Pt nanoparticles supported on amorphous carbon black as ORR catalysts. These catalysts have activity and durability concerns resulting from both the Pt nanoparticles and the amorphous carbon support. Strategies to improve catalyst activity and durability include generating a support-less catalyst, increasing the durability of the catalyst support, and switching to a basic environment. ☐ A transition to unsupported catalysts with an extended surface structure improves specific activity and durability and in turn, the cost-effectiveness of the entire fuel cell. Pt-coated copper nanowires (Pt/CuNW) exemplify these desirable catalytic traits. Improving this platform, post-synthetic processing is used to further enhance the ORR performance of the Pt/CuNW catalyst. Specifically, annealing followed by electrochemical dealloying increases activity by introducing geometric lattice tuning through Cu alloying. The resultant bimetallic PtCu-coated copper nanowire (PtCu/CuNW) catalyst yields ORR specific and mass activities of 2.65 mA cmPt-2 and 1.24 A mgPt-1, surpassing the respective DOE targets (SA and MA) of 0.72 mA cmPt-2 and 0.44 A mgPt-1. PtCu/CuNWs demonstrate enhanced durability over Pt nanoparticle catalysts by maintaining 64.1 % of its active surface area after undergoing 30,000 cycles of a potential cycling accelerated durability test (0.6 - 1.1 vs RHE). Post durability PtCu/CuNWs outperformed the DOE targets with a SA and MA of 1.50 mA cmPt-2 and 0.477 A mgPt-1 ☐ Alternately, increasing catalyst support durability through the introduction of a more durable carbon support has also been accomplished. Highly graphitic and cost-effective Cup-stacked carbon nanofiber supports have the potential to address the support durability concerns. Pt supported on carbon black (Vulcan XC-72) and cup-stacked carbon nanofibers as well as each carbon support alone underwent a high potential (1.4 V vs RHE) accelerated durability test in acidic and basic environments using rotating disk electrode techniques. It was shown that in all environments the cup-stacked carbon nanofiber support demonstrated higher durability and the catalysts tested in the basic environment had better overall stability compared to their acidic counterpart. ☐ HEMFCs have the potential for incorporating a wide variety of non-precious metal catalysts and promise to dramatically lower the fuel cell cost. One commercially available non-precious metal catalyst is Acta 4020. This carbon-based catalyst, containing 3.5 wt. % transition metals, when compared to state-of-the-art Pt/C catalysts shows comparable ORR performance and superior durability while exposed to a potential cycling (0.6 – 1.1 V vs RHE) accelerated durability test. Fuel cell testing also demonstrated the feasibility of incorporating this catalyst into the cathode electrode of a HEMFC.
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 Carbon Materials for Catalysis written by Philippe Serp and published by John Wiley & Sons. This book was released on 2009-02-04 with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first comprehensive book covering all aspects of the use of carbonaceous materials in heterogeneous catalysis. It covers the preparation and characterization of carbon supports and carbon-supported catalysts; carbon surface chemistry in catalysis; the description of catalytic, photo-catalytic, or electro-catalytic reactions, including the development of new carbon materials such as carbon xerogels, aerogels, or carbon nanotubes; and new carbon-based materials in catalytic or adsorption processes. This is a premier reference for carbon, inorganic, and physical chemists, materials scientists and engineers, chemical engineers, and others.
Download or read book Polymer Electrolyte Membrane and Direct Methanol Fuel Cell Technology written by Christoph Hartnig and published by Elsevier. This book was released on 2012-03-19 with total page 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) technology are promising forms of low-temperature electrochemical power conversion technologies that operate on hydrogen and methanol respectively. Featuring high electrical efficiency and low operational emissions, they have attracted intense worldwide commercialization research and development efforts. These R&D efforts include a major drive towards improving materials performance, fuel cell operation and durability. In situ characterization is essential to improving performance and extending operational lifetime through providing information necessary to understand how fuel cell materials perform under operational loads.This two volume set reviews the fundamentals, performance, and in situ characterization of PEMFCs and DMFCs. Volume 1 covers the fundamental science and engineering of these low temperature fuel cells, focusing on understanding and improving performance and operation. Part one reviews systems fundamentals, ranging from fuels and fuel processing, to the development of membrane and catalyst materials and technology, and gas diffusion media and flowfields, as well as life cycle aspects and modelling approaches. Part two details performance issues relevant to fuel cell operation and durability, such as catalyst ageing, materials degradation and durability testing, and goes on to review advanced transport simulation approaches, degradation modelling and experimental monitoring techniques.With its international team of expert contributors, Polymer electrolyte membrane and direct methanol fuel cell technology Volumes 1 & 2 is an invaluable reference for low temperature fuel cell designers and manufacturers, as well as materials science and electrochemistry researchers and academics. Covers the fundamental science and engineering of polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs), focusing on understanding and improving performance and operation Reviews systems fundamentals, ranging from fuels and fuel processing, to the development of membrane and catalyst materials and technology, and gas diffusion media and flowfields, as well as life cycle aspects and modelling approaches Details performance issues relevant to fuel cell operation and durability, such as catalyst ageing, materials degradation and durability testing, and reviews advanced transport simulation approaches, degradation modelling and experimental monitoring techniques
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 Polymer Electrolyte Fuel Cell Degradation written by Matthew M. Mench and published by Academic Press. This book was released on 2011-08-27 with total page 473 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. Designed to be relevant to the professional community in addition to researchers, this book will serve as a valuable reference featuring topics covered nowhere else and a one-stop-shop to create a solid platform for understanding this important area of development. The reference covers aspects of durability in the entire fuel cell stack. Each chapter also includes vision of pathways forward and an explanation of the tools needed to continue along the path toward commercialization. Features expert insights from contributing authors who are key industrial and academic leaders in the field Includes coverage of two key topics in the field- Testing and Protocol for Durability, and Computational Modeling Aspects of PEFC Durability- which are newly emerging, pivotally important subjects not systematically covered anywhere else Undertakes aspects of durability across the entire fuel stack, from membranes to bipolar plates
Download or read book Membrane Degradation Mechanisms in Polymer Electrolyte Membrane Fuel Cells written by Vishal Onkarmal Mittal and published by . This book was released on 2006 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Handbook of Fuel Cells written by Wolf Vielstich and published by John Wiley & Sons. This book was released on 2009-04-20 with total page 1090 pages. Available in PDF, EPUB and Kindle. Book excerpt: A timely addition to the highly acclaimed four-volume handbook set; volumes 5 and 6 highlight recent developments, particularly in the fields of new materials, molecular modeling and durability. Since the publication of the first four volumes of the Handbook of Fuel Cells in 2003, the focus of fuel cell research and development has shifted from optimizing fuel cell performance with well-known materials to developing new materials concepts, and to understanding the origins of materials and fuel cell degradation. This new two-volume set provides an authoritative and timely guide to these recent developments in fuel cell research.
Download or read book In Situ Modeling of Chemical Membrane Degradation in Polymer Electrolyte Fuel Cells written by Ka Hung Wong and published by . This book was released on 2015 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chemical membrane degradation is a major limiting factor for polymer electrolyte fuel cell (PEFC) durability and lifetime. While the effects of chemical membrane degradation are characterized in the literature, the underlying mechanism is not fully understood. This motivates the development of a comprehensive in situ chemical membrane degradation model addressed in this work to determine the linkages between the membrane electrolyte assembly (MEA) macroscopic phenomena, in situ operating conditions, and the temporal membrane degradation process. Chemical membrane degradation through OH radical attack on the membrane, where the radical is produced by decomposition of hydrogen peroxide in the presence of contaminants such as Fe2+, is comprehensively investigated. A redox cycle of iron ions is discovered within the MEA which sustains the Fe2+ concentration in the membrane and results in the most severe chemical degradation at open circuit voltage (OCV). The cycle is suppressed at lower cell voltages leading an exponential decrease in Fe2+ concentration in the membrane and associated membrane degradation rate, which suggests that intermediate cell voltage operation would efficiently mitigate chemical membrane degradation and extend the fuel cell lifetime. Effectiveness of membrane additives (e.g., ceria) in mitigating the membrane degradation is explored. At high cell voltages, abundant Ce3+ ions are available in the membrane to quench hydroxyl radicals which is the primary mitigation mechanism observed at OCV conditions. However, the mitigation is suppressed at low cell voltages, where electromigration drives Ce3+ ions into the cathode catalyst layer (CL). Without an adequate amount of Ce3+ in the membrane, the hydroxyl radical scavenging is significantly reduced. Moreover, the modeling results reveal that proton starvation may occur in the cathode CL due to local Ce3+ accumulation and associated reductions in proton conductivity and oxygen reduction kinetics. Significant performance tradeoffs in the form of combined ohmic and kinetic voltage losses are therefore evident. A lower initial Ce3+ concentration is demonstrated to mitigate voltage losses without compromising membrane durability at high cell voltages. However, the harmful Fe2+ concentration in the membrane increases with the Ce3+ concentration, which suggests that ceria-supported MEAs can experience higher rates of degradation than baseline MEAs at low cell voltages. Strategic MEA design is recommended in order to ensure membrane durability at low cell voltages.
Download or read book Polymer Electrolyte Membrane Degradation and Oxygen Reduction in Fuel Cells written by Alexander Panchenko and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Platinum Electrocatalysis written by Mohammad Javad Eslamibidgoli and published by . This book was released on 2016 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Formation of hydrogen peroxide and oxygenated radical species are the leading cause of chemical degradation observed in polymer electrolyte membranes (PEM) in polymer electrolyte fuel cells. Recent experimental studies have shown that Pt nano-deposits in the PEM, which originate from Pt dissolution in the catalyst layer, play an important role in radical-initiated membrane degradation. Surface reactions at Pt particles facilitate the formation of reactive oxygen species. The net effect of Pt surface processes on membrane degradation depends on the local equilibrium conditions around the Pt nano-deposits, specifically, their equivalent local electrode potential. In this thesis, we first present a multi-step theoretical approach, validated by a collaborative experimental study, to understand the impact of environmental conditions around the Pt nanodeposits on membrane chemical degradation. In the first step, we developed a physical analytical model for the potential distribution at Pt nanodeposits in the PEM. Given the local potential, we identify the surface adsorption state of Pt. Thereafter, density functional theory (DFT) was used to investigate the influence of the Pt adsorption state on the mechanism of oxygen reduction reaction (ORR), particularly the formation of hydrogen peroxide and hydroxyl radical as the two important reactive oxygen species for membrane degradation. In a separate work, we employed DFT to study the atomistic mechanism for interfacial place-exchange between surface Pt atom and chemisorbed oxygen at oxidized Pt (111)-water interfaces. Understanding the criteria for Pt oxide growth is a crucial step to comprehend the mechanisms of Pt dissolution during electrochemical processes.
