[PDF] Preparation Of Perfluorinated Ionomers For Fuel Cell Applications eBook
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One of the major issues with the current membrane technology for polymer electrolyte membrane fuel cells is the low conductivity seen at low relative humidity. This dissertation discloses the preparation of perfluorinated polymers with higher densities of acid sites and higher conductivities to overcome this issue. These materials are prepared using a system designed to safely synthesize and polymerize tetrafluoroethylene (TFE) on a hundred gram scale. The copolymerization of TFE and perfluoro-2-(2-fluorosulfonylethoxy) propyl vinyl ether (PSEPVE) to prepare materials with varying ratios of the two monomers was carried out by solution, bulk, and emulsion polymerization techniques. Additionally, the homopolymer of PSEPVE has been prepared and characterized by MALDI-TOF mass spectrometry, which shows the low molecular weight distribution seen in other similar materials in the literature is due to a high rate of [beta]-scission termination. Spectroscopic measurements and thermal analysis were carried out on these samples to obtain better characterization than was currently available. Producing polymers with a higher amount of PSEPVE, and thus higher density of acid sites, leads to the materials becoming water soluble after hydrolysis. However, addition of a curable ter-monomer allows the polymer chains to be crosslinked to regain water insolubility. Using this approach, water insoluble membranes with high densities of acid sites and conductivities up to 5.5 times higher than Nafion® 115, the standard benchmark for fuel cell membranes, have been produced. Preparation of high molecular weight, low EW copolymers of TFE and PSEPVE is difficult due to the reactivity ratios of the two monomers. Literature reactivity ratios for VDF and PSEPVE are more favorable for preparation of high molecular weight, low EW copolymers. Here, alternating copolymers of VDF and PSEPVE are prepared for the first time; where high molecular weight samples have been shown to possess low swelling characteristics in water. It has also been found the lower molecular weight samples that are soluble in perfluorohexane can be converted to perfluorinated polymers by direct fluorination with 20% elemental fluorine in nitrogen with 254 nm UV irradiation.
Fluorinated ionomer polymers form impermeable membranes that conduct electricity, properties that have been put to use in large-scale electrochemical applications, revolutionizing the chlor-alkali industry and transforming production methods of some of the world’s highest-production commodity chemicals: chlorine, sodium hydroxide and potassium hydroxide. The use of fluorinated ionomers such as Nafion® have removed the need for mercury and asbestos in these processes and led to a massive reduction in electricity usage in these highly energy-intensive processes. Polymers in this group have also found uses in fuel-cells, metal-ion recovery, water electrolysis, plating, surface treatment of metals, batteries, sensors, drug release technologies, gas drying and humidification, and super-acid catalysis used in the production of specialty chemicals. Walther Grot, who invented Nafion® while working for DuPont, has written this book as a practical guide to engineers and scientists working in electrochemistry, the fuel cell industry and other areas of application. His book is a unique guide to this important polymer group and its applications, in membranes and other forms. The 2e expands this handbook by over a third, with new sections covering developments in electrolysis and membranes, additional information about the synthesis and science of the polymer group, and an enhanced provision of reference data. An essential reference for scientists working with electrolysis and electrochemical processes (the use of this polymer group in industrial chemistry processes is credited with a 1% reduction in global electricity usage) Covers the techniques involved in the growing range of applications for fluorinated ionomers, including fuel cells, batteries and drug delivery The only book on this important polymer group, written by Walther Grot, the inventor of the leading fluorinated ionomer, Nafion® from DuPont
From the late-1960’s, perfluorosulfonic acid (PFSAs) ionomers have dominated the PEM fuel cell industry as the membrane material of choice. The “gold standard’ amongst the many variations that exist today has been, and to a great extent still is, DuPont’s Nafion® family of materials. However, there is significant concern in the industry that these materials will not meet the cost, performance, and durability requirementsnecessary to drive commercialization in key market segments – es- cially automotive. Indeed, Honda has already put fuel cell vehicles in the hands of real end users that have home-grown fuel cell stack technology incorporating hydrocarbon-based ionomers. “Polymer Membranes in Fuel Cells” takes an in-depth look at the new chem- tries and membrane technologies that have been developed over the years to address the concerns associated with the materials currently in use. Unlike the PFSAs, which were originally developed for the chlor-alkali industry, the more recent hydrocarbon and composite materials have been developed to meet the specific requirements of PEM Fuel Cells. Having said this, most of the work has been based on derivatives of known polymers, such as poly(ether-ether ketones), to ensure that the critical requirement of low cost is met. More aggressive operational requi- ments have also spurred the development on new materials; for example, the need for operation at higher temperature under low relative humidity has spawned the creation of a plethora of new polymers with potential application in PEM Fuel Cells.
Abstract: Hydrogen is a critical energy carrier for defossilising the transportation sector. Proton-exchange membrane (PEM) fuel cells represent a pivotal technology for heavy-duty vehicles, in particular. These fuel cells enable the conversion of hydrogen into electrical energy, with the only by-product being water. State-of-the-art PEM fuel cells rely on perfluorosulfonic acid (PFSA) as cation-exchange material. The synthesis of PFSAs is complex, hazardous and expensive, which limits their production to a few select facilities globally, driving up costs even at high volumes. In recent years, there has been a growing concern over the high level of irreversible environmental damage caused by perfluorinated substances. Leading corporations, such as DuPont and 3M, have faced numerous lawsuits for over a decade. To address these concerns, 3M announced in December 2022 that it would exit the perfluorinated substances business by the end of 2025. An alternative to PFSAs is hydrocarbon ionomers, which offer potentially lower material costs, high thermo-mechanical stability at high operating temperatures, and reduced environmental concerns. While replacing PFSA with hydrocarbon ionomers can make fuel cells more sustainable, it has been observed in earlier studies to compromise performance. The primary objective of this study was to bridge the performance and knowledge gap between hydrocarbon and PFSA-based PEM fuel cells. This was achieved by employing a recently commercialized ionomer called "Pemion". Leveraging this innovative material, this work succeeded in developing a fully hydrocarbon-based fuel cell with outstanding performance, representing a significant breakthrough in 2021. To realize this outcome, the study began with a comprehensive literature review,[1] that identified the most significant limitations associated with hydrocarbon-based fuel cells and proposed strategies for their future commercialization. Systematic know-how transfer was then implemented from the field of PFSA-based materials, encompassing process adaptations and extensive optimization of the catalyst layer to advance towards the state-of-the-art performance of PFSA-based fuel cells. A combination of an ultra-thin monolithic membrane (7 μm) and an optimized ink composition with a platinum-cobalt catalyst enabled a comparable peak performance (> 2 W cm-2) to state-of-the-art PFSA reference cell under optimized laboratory conditions: H2/O2, 80 °C, fully humidified gases and ambient pressure. Electrochemical characterizations under various operating conditions show that the hydrocarbon-based cells' performance is more sensitive to changes in relative humidity than the PFSA reference cell.[2] Based on the proof-of-concept, two follow-up improvement pathways have been identified to improve performance and understanding in hydrocarbon-based fuel cells. First, ionomer gradient catalyst layers have been introduced for hydrocarbon-based fuel cells.[3] A two-fold higher ionomer content compared to the optimized one in 25 % of the catalyst layer at the membrane interface improved the performance by up to 35 % in application-relevant conditions, i.e. reduced humidity, while maintaining high peak performance under the same conditions. Second, different conditioning procedures were investigated on hydrocarbon-based fuel cells for the first time. A novel conditioning procedure developed for hydrocarbon-based fuel cells was found to improve the typically lower performance at low current densities of hydrocarbon-based fuel cells the most efficiently.[4] Based on the findings, fuel cells that use Pemion have been shown to perform similarly to those that use PFSA, but further improvements are required for their application in fuel-cell electric vehicles. To continue improving these fuel cells, it is important to find a balance between effective proton conductivity and mechanical integrity of the ionomer in the catalyst layer for efficient performance under different humidity levels. Reference: [1] Hien Nguyen, Carolin Klose, Lukas Metzler, Severin Vierrath, and Matthias Breitwieser. Fully hydrocarbon membrane electrode assemblies for proton exchange membrane fuel cells and electrolyzers: An engineering perspective. Advanced Energy Materials, 12(12):2103559, 2022. doi:10.1002/aenm.202103559. [2] Hien T. T. Nguyen, Florian Lombeck, Claudia Schwarz, Philipp A. Heizmann, Michael Adamski, Hsu-Feng Lee, Benjamin Britton, Steven Holdcroft, Severin Vierrath, and Matthias Breitwieser. Hydrocarbon-based pemionTM proton exchange membrane fuel cells with state-of-the-art performance. Sustainable Energy & Fuels, (5):3687-3699, 2021. doi:10.1039/D1SE00556A. [3] Hien T. T. Nguyen, Dilara Sultanova, Philipp A. Heizmann, Severin Vierrath, and Matthias Breitwieser. Improving the efficiency of fully hydrocarbon-based proton-exchange membrane fuel cells by ionomer content gradients in cathode catalyst layers. Materials Advances, 2022. doi:10.1039/d2ma00761d. [4] Hien Nguyen, Julian Stiegeler, Hannes Liepold, Claudia Schwarz, Severin Vierrath, and Matthias Breitwieser. A comparative study of conditioning methods for hydrocarbon-based proton-exchange membrane fuel cells for improved performance. doi:https://doi.org/10.1002/ente.202300202
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
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.
Handbook of Fluoropolymer Science and Technology A comprehensive handbook on fluoropolymer synthesis, characterization, and processing Fluoropolymers, one of the more durable classes of polymer materials, are known to enable novel technologies as a result of their remarkable properties. As key components in industry applications, fluoropolymers have established commercial interest and scientists have discovered more efficient approaches of handling them. This book reviews up-to-date fluoropolymer platforms as well as recently discovered methods for the preparation of fluorinated materials. It focuses on synthesis, characterization, and processing aspects, providing guidelines for practicing scientists and engineers. In addition, the book covers: Concepts and studies from leading international laboratories, including academia, government, and industrial institutions Emerging technologies and applications in energy, optics, space exploration, fuel cells, microelectronics, gas separation membranes, biomedical instrumentation, and more Current environmental concerns associated with fluoropolymers, relevant regulations, and growth opportunities Overall, the chapters provide coverage of chemical methods and help the reader further understand how fluoropolymer research provides solutions for material challenges. The concepts in this book also inspire professionals to identify new markets and funding sources for fluoropolymer research and development.
Industrial Aspects of Fluorinated Oligomers and Polymers; Fluoroalkyl Acrylate Polymers and Their Applications; Structural Diversity in Fluorinated Polyphosphazenes: Exploring the Change from Crystalline Thermoplastics to High-Performance Elastomers and Other New Materials; Fluoroplastics and Fluoroelastomers - Basic Chemistry and High-performance Applications; Fluorinated Specialty Chemicals - Fluorinated Copolymers for Paints and Perfluoropolyethers for Coatings; Commercial Synthesis and Applications of Poly(Vinylidene Fluoride); The Role Perfluoropolyethers in the Development of Polymeric Proton Exchange Membrane Fuel Cells; Fluorinated Ionomers and Ionomer Membranes: Monomer and Polymer Synthesis and Applications; Research and Non-major Commercial Co- and Terpolymers of Tetrafluoroethylene; Chlorotrifluoroethylene Copolymers for Energy-applied Materials; Fabrication of Flexible Transparent Nanohybrids with Heat-resistance Properties Using a Fluorinated Crystalline Polymer; Creation of Superamphiphobic, Superhydrophobic/Superoleophilic and Superhydrophilic/Superoleophobic Surfaces by Using Fluoroalkyl-endcapped Vinyltrimethoxysilane Oligomer as a Key Intermediate
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.