[PDF] The Characterization Of New Fluorinated Ionomers For Use In Polymer Electrolyte Membrane Pem Fuel Cells eBook

Author : Walther Grot
Publisher : William Andrew
Page : 313 pages
File Size : 45,84 MB
Release : 2011-07-15
Category : Technology & Engineering
ISBN : 1437744583

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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

Author : Nadzrinahamin Ahmad Nazir
Publisher :
Page : 211 pages
File Size : 38,77 MB
Release : 2011
Category : Conducting polymers
ISBN :

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Nafion perfluorinated ionomer membrane has been regarded as a benchmark material in proton electrolyte membrane fuel cells (PEMFC) due to its excellent perm selectivity properties. However, the excessive swelling and low operating temperature window (up to 80 °C) of Nafion marked its vital shortcomings in the proton fuel cell operations. This dissertation is focused on the modification of hydrophobic fluorocarbon matrix and hydrophilic ionic domains/clusters of Nafion to alleviate the aforementioned shortcomings. The first modification is via solution blending of Nafion with copolymer of poly(vinylidenefluoride-trifluoroethylene) or PVDF-TrFE, which modified the fluorocarbon matrix of Nafion, while the second is via simple in-situ impregnation of Nafion with several kinds of functionalized supramolecules, which locally alters the properties of the ionic domains/clusters. Nafion/PVDF-TrFE blends revealed an hourglass type phase diagram, consisting of single phase crystal (Cr1), and crystal + liquid (Cr1 + L2) and liquid + liquid (L1 + L2) coexistence regions. Blends of Nafion with PVDF-TrFE demonstrated swelling reduction upon hydration as confirmed by Fourier transform infrared (FTIR) spectroscopy and water uptake measurements. The 60/40 Nafion/PVDF-TrFE blend with bicontinuous morphology exhibits both capacitor and proton conductivity properties. This blend was found to have lower proton conductivity with a decreasing trend upon increasing temperature. Supramolecules of photocurable hyperbranched polyester (HBPEAc-COOH) were used in the first part of in-situ impregnation attempt. Of particular importance is that the present study is the first to successfully incorporate polymer molecules/networks into the Nafion ionic domains by means of impregnation with hyperbranched supramolecules followed by photopolymerization in-situ. HB impregnated Nafion membranes were found to render swelling suppression as well as improved mechanical stability. This impregnated membrane exhibited an increasing trend of proton conductivity with increasing temperature, which eventually surpassed that of neat Nafion above 100 °C. Two unique supramolecules terminated with hydroxyl (Noria) and tert-butyloxycarbonyl (Noria-BOC), which resembles a waterwheel, were used in the second impregnation attempt. We anticipated that these waterwheel supramolecules, Noria in particular, will have potential utility as the "solid proton carrier" in proton fuel cells to substitute the role of water at high temperatures. Noria and Noria-BOC impregnated membranes exhibited excellent swelling suppression and the mechanical stability of both impregnated membranes increased beyond the existing neat Nafion. Only Noria impregnated membrane shows improved proton conductivity at elevated temperature whereas Noria-BOC impregnated membrane revealed a plummet in the proton conductivity at high temperatures similar to that of neat Nafion.

Author : Yun Wang
Publisher : Momentum Press
Page : 450 pages
File Size : 49,48 MB
Release : 2013-04-06
Category : Technology & Engineering
ISBN : 1606502476

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Polymer Electrolyte Membrane (PEM) fuel cells convert chemical energy in hydrogen into electrical energy with water as the only by-product. Thus, PEM fuel cells hold great promise to reduce both pollutant emissions and dependency on fossil fuels, especially for transportation—passenger cars, utility vehicles, and buses—and small-scale stationary and portable power generators. But one of the greatest challenges to realizing the high efficiency and zero emissions potential of PEM fuel cells technology is heat and water management. This book provides an introduction to the essential concepts for effective thermal and water management in PEM fuel cells and an assessment on the current status of fundamental research in this field. The book offers you: • An overview of current energy and environmental challenges and their imperatives for the development of renewable energy resources, including discussion of the role of PEM fuel cells in addressing these issues; • Reviews of basic principles pertaining to PEM fuel cells, including thermodynamics, electrochemical reaction kinetics, flow, heat and mass transfer; and • Descriptions and discussions of water transport and management within a PEM fuel cell, including vapor- and liquid-phase water removal from the electrodes, the effects of two-phase flow, and solid water or ice dynamics and removal, particularly the specialized case of starting a PEM fuel cell at sub-freezing temperatures (cold start) and the various processes related to ice formation.

Author : Tatsuhiro Okada
Publisher : Nova Science Pub Incorporated
Page : 116 pages
File Size : 19,44 MB
Release : 2008
Category : Science
ISBN : 9781604568042

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In this book the authors focus on the ion and water transport characteristics in Nafion and other perfluorinated ionomer membranes that are recently attracting attention in various fields such as water electrolysis, mineral recovery, electrochemical devises and energy conversion. Methodology of measurements and data analysis is first presented that enables basic characterisation of transport parameters in the perfluorinated ionomer membranes. Cation exchange isotherm data are collected in binary cation systems, with the aim to see the behaviours of cationic species that exist with H+ in the membrane. Water transference coefficients, ionic transference numbers, ionic mobilities and other membrane transport parameters are measured in single and mixed counter cation systems using electrochemical methods. Diffusion coefficients of water and cations are also measured by pulsed-field-gradient spin-echo NMR (PGSE-NMR) at various temperatures in different kinds of perfluorinated ionomer membranes. The results are discussed in two perspectives. One is to predict the hydration state in perfluorosulfonated ionomer membranes in relation to the possible degradation of performances in fuel cells under contaminated conditions with foreign cations. An analytical formulation of membrane transport equations with proper boundary conditions is proposed, and using various parameters of membrane transport, a simple diagnosis of water dehydration problem is carried out. This analysis leads one to an effective control of fuel cell operation conditions, especially from viewpoint of proper water management. The others are to elucidate the ion and water transport mechanisms in the membrane in relation to polymer structures (e.g., different ion exchange capacity), and to propose a new design concept of polymer electrolyte membranes for fuel cell applications. Additionally for this purpose methanol and other alcohols are penetrated into the membrane, and alcohol permeability, membrane swelling, ionic conductivity and diffusion coefficients of water and CH3 are measured systematically for various kinds of membranes to cope with the problem of methanol crossover in direct methanol fuel cells (DMFCs).It is found that in order to realise a high ionic conductivity in the membrane, one should aim at a polymer structure through molecular design that takes into account the relative size of ions with a hydration shell against the size and atmosphere of ionic channels. For DMFC, a partially cross-linked polymer chain with high degree of hydrophilic ion transport paths based on phase-separated structures is recommended. Various possibilities of such polymer electrolytes are discussed.

Author : Sarah Garner
Publisher :
Page : 0 pages
File Size : 35,47 MB
Release : 2022
Category :
ISBN :

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Fuel cell membrane durability remains one of the key challenges limiting the wide scale adoption of fuel cell technology. Degradation in polymer electrolyte membrane (PEM) fuel cells limits the operational lifetime of the fuel cell and prevents the widescale adoption of fuel cell technology. This work contributes to characterizing the membrane structure and correlations to mechanical durability. In this study a selection of perfluorosulphonic acid (PFSA) ionomer membranes with expanded polytetrafluoroethylene (ePTFE) reinforcements were tested. The membranes differed mainly in the type of reinforcement layer and the thickness. The membranes were characterized by experiments in Nuclear Magnetic Resonance Spectroscopy, Fourier Transform Infrared Spectroscopy, Small Angle X-ray Scattering, Dynamic Mechanical Analysis and Mechanical Accelerated Stress Testing. The results showed that the greatest impact on membrane durability is the addition of a reinforcement layer, and through the addition/ changing of the reinforcement layer the mechanical strength of the membrane is influenced. The properties that had a positive correlation with increasing in situ mechanical strength were matrix domain spacing, ePTFE crystallinity, yield strength and elastic modulus. Overall, this work provides insight in designing new membranes for increased durability and longer lifetime.

Author : Todd Stephen Sayler
Publisher :
Page : 248 pages
File Size : 32,35 MB
Release : 2012
Category : Electronic dissertations
ISBN :

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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.

Author : Felix N. Büchi
Publisher : Springer Science & Business Media
Page : 489 pages
File Size : 16,95 MB
Release : 2009-02-08
Category : Science
ISBN : 038785536X

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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.