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Advanced direct methanol fuel cells. Final report

Description: The goal of the program was an advanced proton-exchange membrane (PEM) for use as the electrolyte in a liquid feed direct methanol fuel cell which provides reduced methanol crossover while simultaneously providing high conductivity and low membrane water content. The approach was to use a membrane containing precross-linked fluorinated base polymer films and subsequently to graft the base film with selected materials. Over 80 different membranes were prepared. The rate of methanol crossover through the advanced membranes was reduced 90%. A 5-cell stack provided stable performance over a 100-hour life test. Preliminary cost estimates predicted a manufacturing cost at $4 to $9 per kW.
Date: November 1, 1999
Creator: Hamdan, Monjid & Kosek, John A.
Partner: UNT Libraries Government Documents Department

Engineered Nanostructured MEA Technology for Low Temperature Fuel Cells

Description: The objective of this project is to develop a novel catalyst support technology based on unique engineered nanostructures for low temperature fuel cells which: (1) Achieves high catalyst activity and performance; (2) Improves catalyst durability over current technologies; and (3) Reduces catalyst cost. This project is directed at the development of durable catalysts supported by novel support that improves the catalyst utilization and hence reduce the catalyst loading. This project will develop a solid fundamental knowledge base necessary for the synthetic effort while at the same time demonstrating the catalyst advantages in Direct Methanol Fuel Cells (DMFCs).
Date: July 16, 2009
Creator: Zhu, Yimin
Partner: UNT Libraries Government Documents Department

SHAPE SELECTIVE NANOCATALYSTS FOR DIRECT METHANOL FUEL CELL APPLICATIONS

Description: While gold and platinum have long been recognized for their beauty and value, researchers at the Savannah River National Laboratory (SRNL) are working on the nano-level to use these elements for creative solutions to our nation's energy and security needs. Multiinterdisciplinary teams consisting of chemists, materials scientists, physicists, computational scientists, and engineers are exploring unchartered territories with shape-selective nanocatalysts for the development of novel, cost effective and environmentally friendly energy solutions to meet global energy needs. This nanotechnology is vital, particularly as it relates to fuel cells.SRNL researchers have taken process, chemical, and materials discoveries and translated them for technological solution and deployment. The group has developed state-of-the art shape-selective core-shell-alloy-type gold-platinum nanostructures with outstanding catalytic capabilities that address many of the shortcomings of the Direct Methanol Fuel Cell (DMFC). The newly developed nanostructures not only busted the performance of the platinum catalyst, but also reduced the material cost and overall weight of the fuel cell.
Date: September 12, 2012
Creator: Murph, S.
Partner: UNT Libraries Government Documents Department

Advanced Materials for PEM-Based Fuel Cell Systems

Description: Proton exchange membrane fuel cells (PEMFCs) are quickly becoming attractive alternative energy sources for transportation, stationary power, and small electronics due to the increasing cost and environmental hazards of traditional fossil fuels. Two main classes of PEMFCs include hydrogen/air or hydrogen/oxygen fuel cells and direct methanol fuel cells (DMFCs). The current benchmark membrane for both types of PEMFCs is Nafion, a perfluorinated sulfonated copolymer made by DuPont. Nafion copolymers exhibit good thermal and chemical stability, as well as very high proton conductivity under hydrated conditions at temperatures below 80 °C. However, application of these membranes is limited due to their high methanol permeability and loss of conductivity at high temperatures and low relative humidities. These deficiencies have led to the search for improved materials for proton exchange membranes. Potential PEMs should have good thermal, hydrolytic, and oxidative stability, high proton conductivity, selective permeability, and mechanical durability over long periods of time. Poly(arylene ether)s, polyimides, polybenzimidazoles, and polyphenylenes are among the most widely investigated candidates for PEMs. Poly(arylene ether)s are a promising class of proton exchange membranes due to their excellent thermal and chemical stability and high glass transition temperatures. High proton conductivity can be achieved through post-sulfonation of poly(arylene ether) materials, but this most often results in very high water sorption or even water solubility. Our research has shown that directly polymerized poly(arylene ether) copolymers show important advantages over traditional post-sulfonated systems and also address the concerns with Nafion membranes. These properties were evaluated and correlated with morphology, structure-property relationships, and states of water in the membranes. Further improvements in properties were achieved through incorporation of inorganic fillers, such as phosphotungstic acid and zirconium hydrogen phosphate. Block copolymers were also studied due to the possibility to achieve a desired combination of homopolymer properties as well as the unique morphologies that ...
Date: October 26, 2005
Creator: McGrath, James E.
Partner: UNT Libraries Government Documents Department

Commercialization Effort for 1W Consumer Electronics Power Pack

Description: A commercial ready fuel cell charger has been further developed, demonstrated, and field tested during the three phases of this project. The work performed and demonstrated has shown the commercialization readiness of this future product and underlying technology. The tasks in phase 1 of the project focused on component cost reduction, redesign for manufacturability, performance & reliability testing, and system integration. The end of phase 1 was completed on time and was signified by passing the Go/No-Go checkpoint. As shown in the report all technical metrics have been met or exceeded and the Go/No-Go checkpoint was passed in November of 2009. The tasks in phase 2 focused on tool fabrication and tooled component prove-out in working systems. The end of Phase 2 was the accomplishment of building working systems made almost completely of tooled components. The tasks in phase 3 of the project were preparing for and executing a 75 unit field test of the DMFC charger product developed in Phase 1 and phase 2. This field test demonstrated the functionality of the DMFC in the hands of real users while also providing feedback for potential design improvements. This was the first time a significant number of MTI units were put into the field to test usability and functionality. Feedback from the field test was positive and the units functioned well in the field.
Date: June 29, 2011
Creator: Carlstrom, Charles, M.
Partner: UNT Libraries Government Documents Department

Effect of BPSH post treatment on DMFC performance and properties

Description: Direct methanol fuel cells (DMFCs) are being investigated for applications ranging from milliwatt (cell phones) to kilowatt (MUS) size scales. A common pitfall for DMFCs has been the inability of the electrolyte, typically Nafion, to act as an effective methanol barrier. Methanol crossover adversely affects the cell by lowering the cell voltage due to a mixed potential at the cathode and lower fuel utilization. Improved DMFC performance was demonstrated with sulfonated poly(arylene ether sulfone) copolymer membranes (1). Another study has shown the dependence of polymer properties and morphology on the post treatment of such membranes (2). In agreement with measurements on free-standing films, the fuel cell characteristics of these membranes have been found to have a strong dependence on acidification treatment. Methanol permeability, proton conductivity, and electro-osmotic drag coefficient all were found to increase when the membranes were acidified under boiling conditions versus a low-temperature process.
Date: January 1, 2002
Creator: Kickner, M. (Michael); Yuseung, K. (Kim); McGrath, James E.; Zelenay, P. (Piotr) & Pivovar, B. S. (Bryan Scott)
Partner: UNT Libraries Government Documents Department

Direct methanol fuel cell performance using sulfonated poly (arylene ether sulfone) random copolymers as electrolytes.

Description: Sulfonated poly(arylene ether sulfone) random copolymers are a new series of sulfonic acid containing polymers that have shown promise as fuel cell electrolytes. Here, we report on direct methanol fuel cell (DMFC) performance of this class of polymers at sulfonation levels ranging from 40 to 60% (monomer basis). The DMFC performance of these polymers is compared to that of Nafion 117, the long standing standard in fuel cell testing. These polymers show a higher selectivity for protons over methanol for all the sulfonation levels tested, with the 40% sulfonated polymer showing 2.5 times the selectivity of Nafion. While the higher sulfonated forms (50 and 60%) did show a higher selectivity, only the lower sulfonation levels (40 and 45%) have shown improved performance in DMFC testing. The results of these experiments will be discussed in terms of the relevant test conditions, and experimentally determined membrane properties. The relevant DMFC properties of these polymers will be discussed in terms of sulfonation level and compared to those of Nafion 117.
Date: January 1, 2001
Creator: Zawodzinski, T. A. (Thomas A.), Jr.; Zelenay, P. (Piotr); Hickner, M. (Michael); Wang, F. (Feng); McGrath, James E. & Pivovar, B. S. (Bryan Scott)
Partner: UNT Libraries Government Documents Department

Six cell 'single cell' stack diagnostics and membrane electrode assembly evaluation

Description: Polymer electrolyte fuel cells are promising candidates as energy conversion devices in applications from portable power to stationary applications or electric vehicles. In order to achieve practical voltage, power and energy density, stacks are employed for almost all applications. Here, we present a six-cell 'single cell' stack in which individual cells can be isolated from the stack by current carrying leads found within each of the bipolar plates. The current carrying leads allow individual cells to be isolated from the rest of the stack, so that cells can either be tested together or independently. The design of the stack, utility for specific applications, including stack diagnostics and membrane electrode assembly (MEA) testing, and some experimental results, obtained using the stack, are presented. Special focus is given in this paper to the area of direct methanol fuel cell (DMFC) stacks, however the equipment and many of the experimental results presented are appropriate for other fuel cell systems.
Date: January 1, 2002
Creator: Pivovar, B. S. (Bryan Scott); Le Scornet, F. (Francois); Eickes, C. (Christian); Zawodzinski, C. (Christine); Purdy, G. M. (Geraldine M.); Wilson, M. S. (Mahlon S.) et al.
Partner: UNT Libraries Government Documents Department

Direct Methanol Fuel Cell Prototype Demonstration for Consumer Electronics Applications

Description: This report is the final technical report for DOE Program DE-FC36-04GO14301 titled “Direct Methanol Fuel Cell Prototype Demonstration for Consumer Electronics Applications”. Due to the public nature of this report some of the content reported in confidential reports and meetings to the DOE is not covered in detail in this report and some of the content has been normalized to not show actual values. There is a comparison of the projects accomplishments with the objectives, an overview of some of the key subsystem work, and a review of the three levels of prototypes demonstrated during the program. There is also a description of the eventual commercial product and market this work is leading towards. The work completed under this program has significantly increased the understanding of how Direct Methanol Fuel Cells (DMFC) can be deployed successfully to power consumer electronic devices. The prototype testing has demonstrated the benefits a direct methanol fuel cell system has over batteries typically used for powering consumer electronic devices. Three generations of prototypes have been developed and tested for performance, robustness and life. The technologies researched and utilized in the fuel cell stack and related subsystems for these prototypes are leveraged from advances in other industries such as the hydrogen fueled PEM fuel cell industry. The work under this program advanced the state of the art of direct methanol fuel cells. The system developed by MTI micro fuel cells aided by this program differs significantly from conventional DMFC designs and offers compelling advantages in the areas of performance, life, size, and simplicity. The program has progressed as planned resulting in the completion of the scope of work and available funding in December 2008. All 18 of the final P3 prototypes builds have been tested and the results showed significant improvements over P2 prototypes in build ...
Date: July 7, 2009
Creator: Carlstrom, Charles, M., Jr.
Partner: UNT Libraries Government Documents Department

Electrochemical and XRD characterization of platinum-ruthenium blacks for DMFC anodes.

Description: It is generally accepted that Pt-Ru alloy catalysts with an atomic Pt-to-Ru ratio of 1:1 generate the best anode perform'ance in the direct methanol fuel cell (DMFG). However, at near-ambient cell operating temperatures, Gasteiger et al. reported that a catalyst with significantly lower Ru content, {approx} 10 at %, offers the highest activity towards methanol. Recently, Dinh et al. demonstrated that the activity of different Pt-Ru catalysts with the same Pt-to-Ru atomic ratio in the bulk might vary depending on the actual surface composition, which is often significantly different from that in the bulk phase, In this work, we study several experimental Pt-Ru catalysts (Johnson Matthey) with Pt-to-Ru atomic ratio ranging from 9: 1 to 1 :2. Electrocatalytic activity of these catalysts in methanol oxidation reaction is investigated in a regular DMFC 'and probed using voltammetric stripping of surhce CO.
Date: January 1, 2002
Creator: Eickes, C. (Christian); Brosha, E. L. (Eric L.); Garzon, F. H. (Fernando H.); Purdy, G. M. (Geraldine M.); Zelenay, P. (Piotr); Morita, T. (Takanari) et al.
Partner: UNT Libraries Government Documents Department

Methanol crossover in direct methanol fuel cell systems.

Description: Direct methanol fuel cells (DMFCs) are currently being investigated for a number of different applications from several milliwatts to near kilowatt size scales (cell phones, laptops, auxiliary power units, etc .). Because methanol has a very high energy density, over 6000 W hr/kg, a DMFC can possibly have greatly extended lifetimes compared to the batteries, doesn't present the storage problems associated with hydrogen fuel cells and can possibly operate more efficiently and cleanly than internal combustion engines.
Date: January 1, 2003
Creator: Pivovar, B. S. (Bryan Scott); Bender, G. (Guido); Davey, J. R. (John R.) & Zelenay, P. (Piotr)
Partner: UNT Libraries Government Documents Department

TUNING OF SIZE AND SHAPE OF AU-PT NANOCATALYST FOR DIRECT METHANOL FUEL CELLS

Description: In this paper, we report the precise control of the size, shape and surface morphology of Au-Pt nanocatalysts (cubes, blocks, octahedrons and dogbones) synthesized via a seed-mediated approach. Gold 'seeds' of different aspect ratios (1 to 4.2), grown by a silver-assisted approach, were used as templates for high-yield production of novel Au-Pt nanocatalysts at a low temperature (40 C). Characterization by electron microscopy (SEM, TEM, HRTEM), energy dispersive X-ray analysis (EDX), UV-Vis spectroscopy, zeta-potential (surface charge), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS) were used to better understand their physico-chemical properties, preferred reactivities and underlying nanoparticle growth mechanism. A rotating disk electrode was used to evaluate the Au-Pt nanocatalysts electrochemical performance in the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) of direct methanol fuel cells. The results indicate the Au-Pt dogbones are partially and in some cases completely unaffected by methanol poisoning during the evaluation of the ORR. The ORR performance of the octahedron particles in the absence of MeOH is superior to that of the Au-Pt dogbones and Pt-black, however its performance is affected by the presence of MeOH.
Date: April 20, 2011
Creator: Murph, S.
Partner: UNT Libraries Government Documents Department

Direct Methanol Fuel Cell Power Supply For All-Day True Wireless Mobile Computing

Description: PolyFuel has developed state-of-the-art portable fuel cell technology for the portable computing market. A novel approach to passive water recycling within the MEA has led to significant system simplification and size reduction. Miniature stack technology with very high area utilization and minimalist seals has been developed. A highly integrated balance of plant with very low parasitic losses has been constructed around the new stack design. Demonstration prototype systems integrated with laptop computers have been shown in recent months to leading OEM computer manufacturers. PolyFuel intends to provide this technology to its customers as a reference design as a means of accelerating the commercialization of portable fuel cell technology. The primary goal of the project was to match the energy density of a commercial lithium ion battery for laptop computers. PolyFuel made large strides against this goal and has now demonstrated 270 Wh/liter compared with lithium ion energy densities of 300 Wh/liter. Further, more incremental, improvements in energy density are envisioned with an additional 20-30% gains possible in each of the next two years given further research and development.
Date: November 30, 2008
Creator: Wells, Brian
Partner: UNT Libraries Government Documents Department

Two dimensional point of use fuel cell : a final LDRD project report.

Description: The Proliferation Assessment (program area - Things Thin) within the Defense Systems and Assessment Investment Area desires high energy density and long-lived power sources with moderate currents (mA) that can be used as building blocks in platforms for the continuous monitoring of chemical, biological, and radiological agents. Fuel cells can be an optimum choice for a power source because of the high energy densities that are possible with liquid fuels. Additionally, power generation and fuel storage can be decoupled in a fuel cell for independent control of energy and power density for customized, application-driven power solutions. Direct methanol fuel cells (DMFC) are explored as a possible concept to develop into ultrathin or two-dimensional power sources. New developments in nanotechnology, advanced fabrication techniques, and materials science are exploited to create a planar DMFC that could be co-located with electronics in a chip format. Carbon nanotubes and pyrolyzed polymers are used as building block electrodes - porous, mechanically compliant current collectors. Directed assembly methods including surface functionalization and layer-by-layer deposition with polyelectrolytes are used to pattern, build, and add functionality to these electrodes. These same techniques are used to incorporate nanoscale selective electrocatalyst into the carbon electrodes to provide a high density of active electron transfer sites for the methanol oxidation and oxygen reduction reactions. The resulting electrodes are characterized in terms of their physical properties, electrocatalytic function, and selectivity to better understand how processing impacts their performance attributes. The basic function of a membrane electrode assembly is demonstrated for several prototype devices.
Date: March 1, 2011
Creator: Zavadil, Kevin Robert; Hickner, Michael A. (Pennsylvania State University, University Park, PA) & Gross, Matthew L. (Pennsylvania State University, University Park, PA)
Partner: UNT Libraries Government Documents Department

SOME RECENT STUDIES IN RUGHENIUM ELECTROCHEMISTRY AND ELECTROCATALYSIS.

Description: Ruthenium is a metal of a considerable importance in electrochemical science and technology. It is a catalyst or co-catalyst material in Pt-Ru alloys for methanol- and reformate hydrogen-oxidation in fuel cells, while ruthenium oxide, a component in chlorine-evolution catalysts, represents an attractive material for electrochemical supercapacitors. Its facile surface oxidation generates an oxygen-containing species that provides active oxygen in some reactions. Ru sites in Pt-Ru catalysts increase the ''CO tolerance'' of Pt in the catalytic oxidation-reaction in direct methanol fuel cells (DMFC) and in reformate hydrogen-oxidation in proton exchange membrane fuel cells (PEMFC). The mechanism of Ru action is not completely understood, although current consensus revolves around the so-called ''bifunctional mechanism'' wherein Ru provides oxygenated species to oxidize CO that blocks Pt sites, and has an electronic effect on Pt-CO interaction. While various studies of polycrystalline Ru go back several decades those involving single crystal surfaces and the structural sensitivity of reactions on Ru surfaces emerged only recently. Using well-ordered single crystalline surfaces brings useful information as the processes on realistic catalysts are far too complex to allow identification of the microscopic reaction steps. In this article, we focus on progress in model systems and conditions, such as electrochemistry and electrocatalysis on bare and Pt-modified well-ordered Ru(0001) and Ru(10{bar 1}0) single-crystal surfaces. We also review current understanding of the mechanistic principles of Pt-Ru systems and a new development of a Pt submonolayer on Ru support electrocatalyst. Ruthenium crystallizes in a hexagonal close-packed structure, (hcp). Figure 1.1 shows the two single crystal surfaces of Ru. The Ru(0001) surface possesses the densest, i.e. hexagonal arrangement of atoms, Fig. 1.1a. The other plane, Ru(10{bar 1}0), can have one of the two terminations of the surface atoms, Fig. 1.1b. One termination can be described as a stepped surface with a trigonal arrangement of atoms ...
Date: August 1, 2006
Creator: MARINKOVIC, N.S.; VUKMIROVIC, M.B. & ADZIC, R.R.
Partner: UNT Libraries Government Documents Department

Shape Selective Nano-Catalysts: Toward Direct Methanol Fuel Cells Applications

Description: A series of bimetallic core-shell-alloy type Au-Pt nanomaterials with various morphologies, aspect ratios and compositions, were produced in a heterogenous epitaxial fashion. Gold nanoparticles with well-controlled particle size and shape, e.g. spheres, rods and cubes, were used as 'seeds' for platinum growth in the presence of a mild reducing agent, ascorbic acid and a cationic surfactant cethyltrimethyl ammonium bromide (CTAB). The reactions take place in air and water, and are quick, economical and amenable for scaling up. The synthesized nanocatalysts were characterized by electron microscopy techniques and energy dispersive X-ray analysis. Nafion membranes were embedded with the Au-Pt nanomaterials and analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM) for their potential in direct methanol fuel cells applications.
Date: June 16, 2010
Creator: Murph, S.
Partner: UNT Libraries Government Documents Department

Fuel cell systems for personal and portable power applications

Description: Fuel cells are devices that electrochemically convert fuel, usually hydrogen gas, to directly produce electricity. Fuel cells were initially developed for use in the space program to provide electricity and drinking water for astronauts. Fuel cells are under development for use in the automobile industry to power cars and buses with the advantage of lower emissions and higher efficiency than internal combustion engines. Fuel cells also have great potential to be used in portable consumer products like cellular phones and laptop computers, as well as military applications. In fact, any products that use batteries can be powered by fuel cells. In this project, we examine fuel cell system trade-offs between fuel cell type and energy storage/hydrogen production for portable power generation. The types of fuel cells being examined include stored hydrogen PEM (polymer electrolyte), direct methanol fuel cells (DMFC) and indirect methanol fuel cells, where methanol is reformed producing hydrogen. These fuel cells systems can operate at or near ambient conditions, which make them potentially optimal for use in manned personal power applications. The expected power production for these systems is in the range of milliwatts to 500 watts of electrical power for either personal or soldier field use. The fuel cell system trade-offs examine hydrogen storage by metal hydrides, carbon nanotubes, and compressed hydrogen tanks. We examine the weights each system, volume, fuel storage, system costs, system peripherals, power output, and fuel cell feasibility in portable devices.
Date: January 1, 2001
Creator: Fateen, S. A. (Shaheerah A.)
Partner: UNT Libraries Government Documents Department

Characterization of fuel cell electrocatalysts using x-ray methods

Description: High surface area electrocatalysts are critical components of high efficiency low cost polymer membrane fuel cells. The platinum and/or platinum alloy catalysts are typically prepared as nanocrystalline carbon supported and unsupported anode and cathode materials. The choice of catalyst type depends on whether the application is for hydrogen or direct methanol fuel cells (DMFCs). 2 nm crystallite size Pt supported on Vulcan XC-72 carbon is the anode and cathode catalyst most commonly used for hydrogen fuel cells while Pt-Ru alloys of 3-5 nm are currently being used for anode catalysts in DMFC systems. Key parameters for successful catalyst design are average alloy composition, crystal structure, crystallite composition crystallite size and size distribution. All of the aforementioned parameters can be efficently and nondistructively measured using laboratory scale X-ray analysis methods. Recent advances in personal computer technology allow for full profile (Rietveld) and Warren-Averbach Fourier transform X-ray diffraction methods to be performed quickly and routinely. Full profile, also known as whole pattern analysis methods, model the entire X-ray diffraction pattern rather than just peak maxima. Highly overlapped diffraction patterns are very common in nanocrystalline materials due to size related line broadening phenomena. Full profile methods allow for the precise determination of lattice parameters and accurate measurement of individual diffraction line intensities. Phase fractions and percentages of amorphous material can also be estimated using full profile analysis techniques. Warren-Averbach Fourier transform methods allow for the determination of particle size distributions. This method offers advantages in speed and cost over electron microscopic analysis methods to obtain crystallite size distributions. Fundamental parameter X-ray fluorescence spectroscopy methods allows for the rapid accurate determination of catalyst composition and mass loadings on raw materials and membrane electrode assemblies. Another advantage of this method over older empirical standard methods is the elimination of many calibration standards of different compositions. ...
Date: January 1, 2001
Creator: Garzon, F. H. (Fernando H.); Brosha, E. L. (Eric L.); Zawodzinski, C. (Christine) & Ren, X. (Xiaoming)
Partner: UNT Libraries Government Documents Department

Studies of Scale Formation and Kinetics of Crofer 22 APU and Haynes 230 in Carbon Oxide-Containing Environment for SOFC Applications

Description: Significant progress in reducing the operating temperature of SOFCs below 800oC may allow the use of chromia-forming metallic interconnects at a substantial cost savings. Hydrogen is the main fuel for all types of fuel cells except direct methanol fuel cells. Hydrogen can be generated from fossil fuels, including coal, natural gas, diesel, gasoline, other hydrocarbons, and oxygenates (e.g., methanol, ethanol, butanol, etc.). Carbon oxides present in the hydrogen fuel can cause significant performance problems due to carbon formation (coking). Also, literature data indicate that in CO/CO2 gaseous environments, metallic materials that gain their corrosion resistance due to formation of Cr2O3, could form stable chromium carbides. The chromium carbide formation causes depletion of chromium in these alloys. If the carbides oxidize, they form non-protective scales. Considering a potential detrimental effect of carbon oxides on iron- and nickel-base alloy stability, determining corrosion performance of metallic interconnect candidates in carbon oxide-containing environments at SOFC operating temperatures is a must. In this research, the corrosion behavior of Crofer 22 APU and Haynes 230 was studied in a CO-rich atmosphere at 750°C. Chemical composition of the gaseous environment at the outlet was determined using gas chromatography (GC). After 800 h of exposure to the gaseous environment the surfaces of the corroded samples were studied by scanning electron microscopy (SEM) equipped with microanalytical capabilities. X-ray diffraction (XRD) analysis was also used in this study.
Date: January 1, 2006
Creator: Ziomek-Moroz, M.; Covino, B.S., Jr.; Holcomb, G.R.; Bullard, S.J. & Penner, L.R.
Partner: UNT Libraries Government Documents Department

Advanced Materials for PEM-Based Fuel Cell Systems

Description: Proton exchange membrane fuel cells (PEMFCs) are quickly becoming attractive alternative energy sources for transportation, stationary power, and small electronics due to the increasing cost and environmental hazards of traditional fossil fuels. Two main classes of PEMFCs include hydrogen/air or hydrogen/oxygen fuel cells and direct methanol fuel cells (DMFCs). The current benchmark membrane for both types of PEMFCs is Nafion, a perfluorinated sulfonated copolymer made by DuPont. Nafion copolymers exhibit good thermal and chemical stability, as well as very high proton conductivity under hydrated conditions at temperatures below 80 degrees C. However, application of these membranes is limited due to their high methanol permeability and loss of conductivity at high temperatures and low relative humidities. These deficiencies have led to the search for improved materials for proton exchange membranes. Potential PEMs should have good thermal, hydrolytic, and oxidative stability, high proton conductivity, selective permeability, and mechanical durability over long periods of time. Poly(arylene ether)s, polyimides, polybenzimidazoles, and polyphenylenes are among the most widely investigated candidates for PEMs. Poly(arylene ether)s are a promising class of proton exchange membranes due to their excellent thermal and chemical stability and high glass transition temperatures. High proton conductivity can be achieved through post-sulfonation of poly(arylene ether) materials, but this most often results in very high water sorption or even water solubility. Our research has shown that directly polymerized poly(arylene ether) copolymers show important advantages over traditional post-sulfonated systems and also address the concerns with Nafion membranes. These properties were evaluated and correlated with morphology, structure-property relationships, and states of water in the membranes. Further improvements in properties were achieved through incorporation of inorganic fillers, such as phosphotungstic acid and zirconium hydrogen phosphate. Block copolymers were also studied due to the possibility to achieve a desired combination of homopolymer properties as well as the unique morphologies ...
Date: October 26, 2005
Creator: McGrath, James E.; Baird, Donald G. & Spakovsky, Michael von
Partner: UNT Libraries Government Documents Department