The Design and Synthesis of High Performance Polyolefins for Use in Alkaline Anion Exchange Membrane Fuel Cells

The Design and Synthesis of High Performance Polyolefins for Use in Alkaline Anion Exchange Membrane Fuel Cells
Author: Henry Aloysius Kostalik (IV)
Publisher:
Total Pages: 154
Release: 2011
Genre:
ISBN:

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Fuel cells are devices that convert the chemical energy stored in a fuel directly into electricity and have the potential to serve as a highly efficient and environmentally sustainable power generation technology for stationary and mobile applications. Within a fuel cell, the polymer electrolyte membrane serves as the ion conducting medium between the anode and cathode, making it a central, and often performance-limiting component of the fuel cell. The most common polymer electrolyte membrane fuel cells operate under acidic conditions and are therefore proton conducting. Although proton exchange membrane (PEM) fuel cells are well developed and can offer excellent performance, they rely almost exclusively on platinum, a very expensive and scarce noble metal. This dependence on platinum has severely hindered wide scale commercialization of PEM fuel cell technologies. By comparison, alkaline fuel cells that employ hydroxide conducting alkaline anion exchange membranes (AAEMs) are relatively unexplored. A major advantage of alkaline fuel cells, when compared to acidic fuel cells, is their enhanced reaction kinetics for oxygen reduction, permitting the use of less costly, non-noble metal catalysts (e.g. Ni). Therefore, high performance AAEMs could significantly advance fuel cell technologies. We have been working to develop new polymeric materials that can serve as effective AAEMs. Prior work in this area has mainly focused on re-engineering existing materials to access AAEMs. In contrast, we approached this problem from a synthetic perspective by designing and synthesizing materials from the ground up. Herein, the synthesis of two separate AAEM systems that are synthesized via ring-opening metathesis polymerization are described. The first route involves the copolymerization of a tetraalkylammonium-functionalized norbornene with dicyclopentadiene. The crosslinked thin films generated are mechanically strong and exhibit exceptional methanol tolerance. The second route involves the synthesis of a solvent processable, tetraalkylammonium-functionalized polyethylene for use as an AAEM. The membranes are insoluble in both pure water and aqueous methanol but exhibit excellent solubility in a variety of other aqueous alcohols. These solubility characteristics extend the utility of this system for use as both an AAEM and ionomer electrode material from a single polymer composition. The AAEMs generated are mechanically strong and exhibit high hydroxide conductivities. Lastly, we have developed a standardized procedure for measuring the alkaline stability of a benzyltrimethylammonium (BTMA) model compound and a BTMA functionalized polyethylene. The procedure is broadly applicable and should serve as a testing method to better understand other systems, specifically those based on novel cations. Applying this procedure should facilitate the discovery of AAEMs with increased base stability, thus enabling high temperature AAEM fuel cell operation.

Enhancements of the Synthesis and Fabrication of Anion Exchange Membranes

Enhancements of the Synthesis and Fabrication of Anion Exchange Membranes
Author: Megan Matta
Publisher:
Total Pages: 0
Release: 2023
Genre:
ISBN:

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Ion exchange membranes (IEMs) have emerged as important components in a wide variety of electrochemical processes and applications, playing a vital role in facilitating the selective transport of ions while preventing species crossover between the anolyte and catholyte. These versatile polymer or polymer composite membranes find uses in diverse fields such as energy conversion and storage, water treatment, chemical synthesis, and biotechnology. At the core of their functionality, ion exchange membranes exhibit a unique property known as "selective permeability." This property allows them to permit the controlled movement of specific ions across their structure based on differences in charge and size, while restricting the transport of other species. Diffusion of other molecules, such as water, can also be controlled simultaneously by optimizing the ion content, water uptake, and polymer structure of these materials. The design and synthesis of ion exchange membranes involve the incorporation of charged functional groups capable of exchanging ions with the surrounding solution. This functional group can be embedded in the backbone of the polymer, in an ionene-type structure, or attached to the backbone by tethered side chains. IEMs are broadly classified by the charge of the functional group into cation exchange membranes (CEMs) and anion exchange membranes (AEMs). CEMs have anionic functional groups and permit the transport of cations, whereas AEMs have cationic functional groups and permit the transport of anions. Bipolar membranes (BPM) are a type of composite IEM consisting of an AEM and CEM laminated together and an interesting topic of future research. Most AEMs produced today contain chemically unstable arylene ether backbones, have poor mechanical properties, and require toxic reagents for functionalization. This dissertation seeks to synthesize new anion exchange membranes that are stable in alkaline conditions while maintaining the high conductivities required for the operation of electrochemical devices. To develop a chemically stable aliphatic polyolefin AEM, a library of polymers synthesized via Ziegler-Natta polymerization was examined. This library consisted of quaternized poly(11-bromo-1-undecene-co-4-phenyl-2-butene) with degrees of functionalization of 20 mol% to 50 mol% -- and was made utilizing a different catalyst system than previously explored. A TiCl3ˑAA catalyst was reacted with triisobutylaluminum (TiBA) co-catalyst to synthesize a more robust catalyst complex than the traditional AlEt2Cl catalyst. It was found that this new system could incorporate a higher amount of halogenated monomer (up to 50 mol %) on a multi-gram scale (50 g) at high yield without poisoning and deactivating the catalyst. The monomer incorporation was equal to the monomer feed and allowed for the targeting of specific ion exchange capacities. A large-scale synthesis (100 g) was conducted to assess the feasibility of pilot scale experiments. The dissolved polymers were solvent cast onto an ePTFE support and heterogeneously quaternized by immersing the alkylbromide-functionalized membrane in trimethyl amine solution. This procedure resulted in uneven wrinkled membranes, and a new method of casting supported membranes was subsequently developed, as described below. The hydroxide conductivity of the membranes was measured at room temperature, with conductivities up to 32 mS/cm reported. Given the issues with deformities in the supported membranes, further work focused on developing more efficient and consistent methods of membrane fabrication. It is speculated from initial experiments that high molecular weight polymer was being filtered from the sample during solution processing -- decreasing the mechanical strength of cast membranes. The quaternary ammonium-functionalized polyolefins were cryomilled to retain high molecular weight polymer without aggregation. Casting membranes from the cryomilled powder increased the mechanical properties of the membrane such that the mechanical membrane support was no longer needed. Moreover, cryomilling facilitated bulk heterogenous quaternization of the polymer prior to membrane fabrication, reducing the amount of trimethylamine solution needed. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) measurements confirmed that the Menshutkin reaction went to completion and all bromine moieties were quaternized for all degrees of functionalization. The quaternized polymer resins were cryomilled to yield a free-flowing powder that could be used for AEM fabrication. The polymers were examined with thermogravimetric analysis, and the degradation temperature of the ammonium was found to be 215 °C in the chloride form. Suggesting that thermal processing, such as heat pressing, is a viable option for membrane fabrication. Environmentally benign ethanol as a solvent was utilized to disperse the powder and cast membranes unsupported. The resulting AEMs were smooth, with even appearance across the sample, and thin, with thicknesses ranging between 15 [mu]m and 20 [mu]m. Preliminary synthesis on a monomer for ring opening metathesis polymerization (ROMP) was attempted in an effort to examine the effects of well-defined backbone architecture on conductivity and chemical durability. The monomer, 3-(N,N'-dimethylpropyl-1-amine)-cyclooctene, was synthesized in high purity and characterized by proton NMR. Unfortunately attempts to polymerize the monomer via ROMP were unsuccessful as of the writing of this dissertation.

Alkaline Anion Exchange Membranes for Fuel Cells

Alkaline Anion Exchange Membranes for Fuel Cells
Author: Jince Thomas
Publisher: John Wiley & Sons
Total Pages: 453
Release: 2024-02-07
Genre: Technology & Engineering
ISBN: 3527837590

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Alkaline Anion Exchange Membranes for Fuel Cells Build the fuel cells of the future with this cutting-edge material Alkaline anion exchange membranes (AAEMs) are cutting-edge polyelectrolyte materials with growing renewable energy applications including fuel cells, batteries, hydrogen electrolyzers and electrodialysis technologies. Their use in relatively new alkaline exchange membrane fuel cells (AEMFCs) is designed to produce cost-effective clean energy (electricity) produced by a chemical reaction. Rigorous studies are being conducted to meet the requirements of AAEMs precisely tailored for high anion conductivity and durability for future high energy efficient devices. Hence, over the past few years the academic and industrial scientific communities have explored various polymeric, composite and inorganic materials and studied their properties as a potential AAEM. The accumulated literature in this area of investigation is vast and in order to provide the community with the tools needed to strive forward, there is a clear need to condense this information in a single volume. Alkaline Anion Exchange Membranes for Fuel Cells meets this need with a comprehensive overview of the properties of these membranes and their applications. The book considers recent developments, common challenges, and the long-term prospects for this field of research and engineering. It constitutes a one-stop resource for the development and production of AAEM fuel cells and related electrochemical applications. Alkaline Anion Exchange Membranes for Fuel Cells readers will find: Discussion of electrochemical applications like redox flow batteries, water electrolysis, and many more Detailed treatment of specially tailored cationic groups such as quaternary ammonium and guanidinium Expert advice on efficient fabrication and electrode assembly Alkaline Anion Exchange Membranes for Fuel Cells is ideal for electrochemists, materials scientists, polymer chemists, electrical engineers, and anyone working in power technology or related fields.

Nanocarbons for Energy Conversion: Supramolecular Approaches

Nanocarbons for Energy Conversion: Supramolecular Approaches
Author: Naotoshi Nakashima
Publisher: Springer
Total Pages: 564
Release: 2018-08-13
Genre: Technology & Engineering
ISBN: 3319929178

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This book focuses on nanocarbons (carbon nanotubes, graphene, nanoporous carbon, and carbon black) and related materials for energy conversion, including fuel cells (predominately proton exchange membrane fuel cells [PEMFC]), Li-ion batteries, and supercapacitors. Written by a group of internationally recognized researchers, it offers an in-depth review of the structure, properties, and functions of nanocarbons, and summarizes recent advances in the design, fabrication and characterization of nanocarbon-based catalysts for energy applications. As such, it is an invaluable resource for graduate students, academics and industrial scientists interested in the areas of nanocarbons, energy materials for fuel cells, batteries and supercapacitors as well as materials design, and supramolecular science.

New Trends in Ion Exchange Studies

New Trends in Ion Exchange Studies
Author: Selcan Karakus
Publisher: BoD – Books on Demand
Total Pages: 94
Release: 2018-11-07
Genre: Science
ISBN: 1789842476

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This book covers new systems in technology that have developed our knowledge of ion exchange. This book discusses ion exchange resins to enhance cell growth; anion exchange membrane; nanosystems in ion exchange and ion exchange in environmental applications. The ion exchange system is used in bionanotechnology, cosmetic industry and water treatment.

Redox Flow Batteries

Redox Flow Batteries
Author: Huamin Zhang
Publisher: CRC Press
Total Pages: 409
Release: 2017-11-22
Genre: Science
ISBN: 1351648721

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Flow batteries have received attention in large-scale energy storage due to their flexible design, high safety, high energy efficiency, and environmental friendliness. In recent years, they have been rapidly developed and tested in a variety of scales that prove their feasibility and advantages of use. As energy becomes a global focus, it is important to consider flow battery systems. This book offers a detailed introduction to the function of different kinds of redox flow batteries, including vanadium flow batteries, as well as the electrochemical processes for their development, materials and components, applications, and near future prospects. Redox Flow Batteries: Fundamentals and Applications will give readers a full understanding of flow batteries from fundamentals to commercial applications.

Synthesis And Characterization Of Polymeric Anion Exchange Membranes

Synthesis And Characterization Of Polymeric Anion Exchange Membranes
Author: Wenxu Zhang
Publisher:
Total Pages:
Release: 2016
Genre:
ISBN:

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As alkaline anion exchange membrane fuel cells (AAEMFC) are regarded as promising and important energy devices, the development of high performance anion exchange membranes are in urgent need, as well as fundamental investigation on the structure-property relationship, which are the motivation of this dissertation. Three different polymer systems are presented and focused on polymer synthesis, material morphology, and ion transport phenomena. Crosslinked membranes are promising as practical materials, however, the understanding and further improvement of its performance is hindered by the lack of an ordered morphology or well-defined chemical structure. In Chapter 2, a series of crosslinked membranes were design to bear cationic groups organized via covalent linkages, which were synthesized by sequential reversible addition-fragmentation chain transfer radical polymerization (RAFT), "click" chemistry, cast/crosslinking process, and solid state quaternization. Significant enhancement in conductivities was observed and presumably attributed to the formation of ion transport channels directed by polycation chains. Excellent membrane performance were observed, including conductivities, water diffusivities, and fuel cell power densities. In Chapter 3, phosphonium containing block copolymers were synthesized and subjected to morphology characterization. Using Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM), it was observed that these materials form well-ordered morphologies upon solvent casting, and the ionic block preferred to form a continuous phase. By comparing the anion conductivities, the matrix in a hexagonal phase was proved to be more efficient in ion transport than lamellae. Polycyclooctene (PCOE) based triblock copolymers were synthesized in Chapter 4, by using a special chain transfer agent (CTA) to mediate Ring-Opening Metathesis Polymerization (ROMP) and reversible addition-fragmentation chain transfer radical polymerization (RAFT). The well-defined melting transition (~50 oC) of PCOE enabled the investigation of the thermal transition in hydrophobic block affecting ionic domain behavior. Then metal ion doped star block copolymers were investigated in bulk and thin film forms to demonstrate that the star block copolymer architecture can facilitate microphase separation and thus the preparation of smaller features. Using an ortho-nitrobenzyl ester junction, triblock copolymers based on PEO and PSt were synthesized and applied to hierarchical pattern fabrication in self-assembled thin films. During these studies, the single monomer insertion methodology was developed for high efficiency synthesis of (multi)functional RAFT CTAs. The molecular characterization and controlled polymerization results were documented in Chapter 7. The last chapter contains outlooks based on the research in this dissertation. Methods to improve the previously presented materials were listed. Also, fundamental questions were raised on ion transport membranes, and possible ways to answer them were provided. In addition, potential research directions are proposed.

Characterization of Minerals, Metals, and Materials 2020

Characterization of Minerals, Metals, and Materials 2020
Author: Jian Li
Publisher: Springer Nature
Total Pages: 723
Release: 2020-01-23
Genre: Technology & Engineering
ISBN: 3030366286

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This collection gives broad and up-to-date results in the research and development of materials characterization and processing. Topics covered include advanced characterization methods, minerals, mechanical properties, coatings, polymers and composites, corrosion, welding, magnetic materials, and electronic materials. The book explores scientific processes to characterize materials using modern technologies, and focuses on the interrelationships and interdependence among processing, structure, properties, and performance of materials.

Polymerized Ionic Liquids

Polymerized Ionic Liquids
Author: Ali Eftekhari
Publisher: Royal Society of Chemistry
Total Pages: 564
Release: 2017-09-18
Genre: Science
ISBN: 1782629602

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The series covers the fundamentals and applications of different smart material systems from renowned international experts.