Posters presented at the October 16, 2006 Deans’ Forum on Energy Security and Sustainability

Hydrogen and Fuel Cells

16: Photocatalytic Hydrogen Production from Water Using Supramolecular Assemblies

The conversion of light energy into chemical energy is currently a topic of considerable interest. This interest has been stimulated by the urgent need for alternative energy sources as the depletion of the limited fossil fuel supply increase with increasing population. Hydrogen has been proposed as an attractive alternative form of energy for the future and water a cheap renewable source of energy. The conversion of solar energy into chemical energy through water splitting, to generate hydrogen and oxygen, is a potentially clean and renewable source of hydrogen fuel for the hydrogen economy. Solar energy can be harnessed more efficiently to produce hydrogen from water using a photocatalyst. Studies directed towards the use of mixed-metal supramolecular complexes as photocatalysts for the production of hydrogen from water are described. The authors wish to acknowledge the financial collaboration of Phoenix Canada Oil Company which holds long term license rights to commercialize the technology. The authors also wish to acknowledge the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy for their generous support of this research. References 1. Elvington, M.; Brewer, K. J. “Photoinitiated Electron Collection at a Metal in a Rhodium-Centered Mixed-Metal Supramolecular Complex” Inorg. Chem. 2006, 45, 5242-5244. 2. Brown, J.; Elvington, M.; Mongelli, M. T.; Zigler, D. F.; Brewer, K. J. “Analytical Methods Development for Supramolecular Design in Solar Hydrogen Production” Proc. SPIE 2006, in press.

Karen J. Brewer, kbrewer@vt.edu, 540-231-6579, Mail code: 0212, Affiliation: faculty

Shamindri M. Arachchige, arachsm@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: postdoc

Mark Elvington, melvingt@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: graduate student

Jared M. Brown, jrbmbm3@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: graduate student

Shengliang Zhao, zhao@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: graduate student

Joan Zapiter, jzapiter@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: graduate student

David Zigler, dfzigler@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: graduate student

Matthew T. Mongelli, mongelli@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: postdoc

Caitlin Nickel, crnickel@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: undergrad

Michael Robertson, mrob4vt@vt.edu, 540-231-4708, Mail code: 0212, Affiliation: undergrad

4: Morphological Analysis of Molecular Weight Effects Based on Random and Multiblock Copolymers for Fuel Cells

The proton exchange membrane (PEM) fuel cell is a fuel conversion technology for applications ranging from automobiles, homes, and portable electronic devices. PEMs must possess several characteristics to be viable, like high protonic conductivity, good mechanical properties, hydrolytic stability, low fuel permeability, and cost effectiveness. While Nafion®, a perfluorinated sulfonic acid polymer, is currently the standard for use in PEMs, its limitations, which include cost and fuel permeability, have prompted research into alternative PEM materials. A promising alternative to Nafion® may be sulfonated poly(arylene ether sulfone) (BPSH) copolymers, which display good chemical/mechanical stability and proton conductivity, as well as reduced fuel permeability. Sulfonated poly(arylene ether sulfone) copolymers synthesized with fluorinated comonomer (4,4’-hexafluoroisophenylidene diphenol or 6F-bisphenol; 6FSH) possess the positive membrane characteristics of BPSH copolymers and bond well to Nafion® electrodes. Copolymerizing BPSH with hydrophobic oligomers into multiblock copolymers may be an additional way to optimize membrane properties. While it is accepted that molecular weight will directly influence PEM mechanical properties, the influence of molecular weight or block length upon morphology and other membrane properties is not as well-characterized. The present study evaluates the effect of molecular weight upon the morphologies and membrane properties of two random copolymer series (BPSH and 6FSH) and the effect of block length upon the morphologies and membrane properties of two multiblock copolymer series containing BPSH. Using tapping mode atomic force microscopy (AFM), it can be observed that changes in molecular weight appear to have little effect on the phase separated morphologies, water uptake, and proton conductivities of random copolymers. Changes in block length, however, have a pronounced effect on the phase separated morphologies of multiblock copolymers. Additional study is required to more completely determine the relationship between block length, morphology, and membrane properties for the multiblock copolymers.

Anand Badami, abadami@vt.edu, 231-3778, Mail code: 0212, Affiliation: graduate student

Hae-Seung Lee, hslee@vt.edu, Affiliation: graduate student

Yanxiang Li, lyxiang@vt.edu, Affiliation: graduate student

Abhishek Roy, aroy@vt.edu, Affiliation: graduate student

Hang Wang, hawang3@vt.edu, Affiliation: graduate student

James McGrath, jmcgrath@vt.edu, Mail code: 0344, Affiliation: faculty

44: Falling Film Fuel Cell

Most of the world’s fossil fuel is in the form of solid coal. Biomass is also in solid form. Solid fuels are important for large-scale stationary power generation. Leading fuel cell technologies use stationary electrolytes and advanced micro-porous materials. These cells are not suitable for power generation directly from solid fuels because they become fouled with fuel impurities and because the cost of the materials is prohibitive. The falling film cell uses a flowing molten carbonate electrolyte which entrains solid fuel, delivers it to the reaction zone, and carries off impurities. It uses a laminar flow layer, rather than a porous membrane, to separate fuel and oxygen. The cathode reaction is 2CO2 + 3CO2 + 4e¬–. ® 2CO3=, while the anode reaction is C + 2CO3= ®O2 + 4e¬– CO2. ®The net reaction is thus C + O2 The cell consists of two macro-porous beds, one for the anode and one for the cathode, separated by a small gap. These beds are large in height but small in thickness. Electrolyte is fed into each bed from the top. Electrolyte flow rate is such that the frictional resistance of the flow through the bed is balanced by the gravitational force on the electrolyte and the bed remains fully wetted. Oxygen and carbon dioxide are supplied to the outer surface of the cathode bed. They diffuse into the cathode and react with electrons on the cathode surface to form carbonate ions. The electrolyte flowing into the anode contains carbon particles. Carbonate ions are conducted through the electrolyte to the surface of the particles, where they combine with carbon to form electrons and carbon dioxide. The electrons are transferred to the current-collecting anode bed through collisions, while the carbon dioxide diffuses to the anode outer surface where it vaporizes. Falling film cells can be efficiently grouped into cell arrays, and multiple arrays can be combined to form large power plants.

Alan Kornhauser, alkorn@vt.edu, 231-7064, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Ritesh Agarwal, ritesha@vt.edu, 231-6801, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: graduate student

9: A Revolutionary Technology: High-Yield Hydrogen Production from Sugars by Artificial Enzymatic Pathway Engineering

The hydrogen economy offers a compelling future energy vision because hydrogen is abundant, clean, flexible, and secure. Here we have designed a novel artificial enzymatic pathway engineering (AEPE) that can convert abundant polysaccharides (starch and cellulose) plus water to net hydrogen and carbon dioxide with a stoichiometric reaction (C6H10O5 + 7 H2O --> 12 H2 + 6 CO2). These reactions integrate reversible substrate phosphorylation by glucan phosphorylases, pentose phosphate pathway, and hydrogen production by hydrogenase. Based on enzymatic reactions and thermodynamic analysis, the overall process is spontaneous and unidirectional because of a negative Gibbs free energy and the removal of gaseous products of reaction from the aqueous reaction phase. It requires neither energy input nor consumption of coenzymes or other chemicals, once a stable multi-enzyme biocatalyst has been developed. Mild reaction conditions, high hydrogen yields, projected low production costs, and high energy density of polysaccharides (14.8 H2-based mass%) make this designed pathway reaction for hydrogen production even more appealing. With technology improvements, this technology will highly likely become the basic technology for the incoming hydrogen economy, especially for mobile applications. Based on this technology, we propose a new conceptual SUGAR CAR, in which the sugar is converted to hydrogen on board, electricity is produced via hydrogen-fuel-cells, and motor is driven by electricity. This power train system would have as high as 60% energy conversion efficiency.

Percival Zhang, ypzhang@vt.edu, 231-7414, Dept: Biological Systems Engineering, Mail code: 0303, Affiliation: faculty

50: Multiblock Hydrophilic-Hydrophobic Proton Exchange Membranes for Fuel Cells

Fuel cells are electrochemical devices that convert chemical energy to electrical energy. Among various types of fuel cells, proton exchange membrane fuel cells (PEMFCs) are of major importance. The integral part of the fuel cell is considered to be the PEM. The current state of the art PEMs are perfluorosulfonic acid membranes such as Nafion® manufactured by DuPont. Our research group has been engaged in the past few years in the synthesis and characterization of biphenol based partially disulfonated poly(arylene ether sulfone) (BPSH) random copolymers as potential PEMs. Both Nafion and BPSH show high proton conductivity at fully hydrated conditions. However proton transport is especially limited at low hydration level for the BPSH random copolymer. We have recently synthesized a series of multiblock ionomers having polyimide hydrophobic blocks and poly(arylene ether sulfone) hydrophilic blocks with 100% degree of sulfonation. Unlike the BPSH copolymers, where the sulfonic acid groups are randomly distributed in pairs along the chain, the multiblock copolymers feature an ordered sequence of hydrophilic and hydrophobic segments. The transport properties of the BPSH-PI multiblock copolymers were studied over a range of different block lengths and IECs. Under fully hydrated conditions all the multiblock copolymers showed similar proton conductivity. However under partially hydrated conditions the proton conductivity was found to be a function of block lengths. This was attributed to the decreasing morphological barrier to the transport with increasing block length, as studied from the diffusion coefficients and AFM images. However for methanol transport, methanol permeability showed a reverse trend in compare to the self diffusion coefficient of water. Thus in multiblock copolymers, the hydrophilic domains provide a pathway for water and proton transport where as the hydrophobic domains apparently acts as a barrier for methanol transport.

Abhishek Roy, aroy@vt.edu, 540-230-9337, Dept: Macromolecular Science and Engineering, Mail code: 0212, Affiliation: graduate student

Hae-Seung Lee, Affiliation: graduate student

Xiang Yu, Affiliation: graduate student

Stuart Dunn, Affiliation: undergrad

Anand Badami, Affiliation: graduate student

Yanxiang Li, Affiliation: faculty

James McGrath, Affiliation: graduate student

52: Advanced Technology Vehicle Fleet Impact Assessment Study

The latest conventional passenger vehicles using petroleum-based fuels have very low tailpipe and evaporative emissions relative to previous generation vehicles. On the other hand, fuel economy has hardly increased over the same period and fleet-average fuel economy has actually decreased since more vehicles are classified as light duty trucks (LDTs; sport utility vehicles and minivans) and are used for daily transportation. Growing vehicle miles traveled (VMT) per year increases our dependence on imported oil (rising toward 60%) and greenhouse gas (GHG) emissions from combustion of hydrocarbon fossil fuels. Also, most of the vehicle environmental impact (over 90%) comes from fuel or energy use. Advanced technology vehicles (ATVs), such as hybrid electric vehicles (HEVs), flexible-fuel vehicles (FFV) using E85 or gasoline in any combination, and fuel cell vehicles (FCV) using compressed hydrogen gas (CHG), have several advantages compared to conventional vehicles; better fuel economy, less GHG emissions, and lower tailpipe emissions. Therefore, the objective of this study is to asses the overall environmental impact from a sales fleet vehicle application for these ATVs and alternative fuels compared to conventional vehicles and petroleum-based fuels. For this study, vehicle use patterns are surveyed from four selected regions; Atlanta, GA, San Diego, CA, Chicago, IL, and the mountain west, as a reference. Also, this study identifies those vehicles (including conventional gasoline vehicles) and their characteristics that have most significant impact on the analysis and conclusions. After this study, additional field testing for selected vehicles will be performed to collect and analyze data on fuel/energy use.

Doug Nelson, Doug.Nelson@vt.edu, 231-4324, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Jeongwoo Lee, jeongwoo@vt.edu, 231-6801, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: graduate student

59: Hydrogen Fuel Cell Auxiliary Power Unit for Transportation Applications

Finding alternatives to oil in the transportation sector is a critical task due to the diminishing supply of oil and the threat that global warming poses to the environment. The Hybrid Electric Vehicle Team (HEVT) of Virginia Tech has addressed both of these issues through the development of a demonstration hydrogen fuel cell auxiliary power unit (APU). HEVT’s fuel cell APU is designed to provide 12 V electrical power to a vehicle, replacing the inefficient engine/alternator with a more efficient system. In addition, the APU provides a mobile 120 V A/C supply that is ideal for use during camping, tailgating, and other events that require AC electrical power. Finally, this APU provides an excellent demonstration to educate the public on how an automotive hydrogen fuel cell system works. Hydrogen fuel cells provide for a promising alternative to oil for transportation energy needs. When made from renewable energy sources or clean nuclear energy, hydrogen serves as a clean energy carrier for automobiles. Adding to this cleanliness, the only emission from a hydrogen fuel cell is pure water. Experts have posed that the world will hit a peak in oil production sometime within the next 5 to 40 years. This pivotal period, known as Peak Oil, will mark when oil demand will exceed the world’s ability to produce oil leading to an unprecedented soaring of energy costs. Through alternative energy research, HEVT is working to help solve the world’s energy and environment problems, and train the future generation of engineers that will have no choice but to find solutions.

Doug Nelson, Doug.Nelson@vt.edu, 231-4324, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Bryan Shevock, bshevock@vt.edu, 231-6801, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: graduate student

64: Development of a Nitrifying Microbial Fuel Cell for Sustainable Wastewater Treatment

Wastewater treatment is an energy intensive process that removes contaminants and protects the environment. While some wastewater treatment plants (WWTPs) recover a small portion of their energy demand through sludge handling processes, most of the useful energy available from wastewater remains unrecovered. Efforts are underway to harness energy from wastewater by developing microbial fuel cells (MiFCs) that generate electricity. To date, MiFC technology based on wastewater treatment has focused on utilizing energy from carbon metabolism; however, this approach has been plagued with inefficiencies. Microaerobic nitrifying MiFCs have key advantages over carbon-based metabolism (e.g., higher electron flux potential of ammonia-N over most forms of carbon in domestic sewage) and could eventually replace aerobic ammonia oxidation at WWTPs. Another significant challenge with MiFCs has been the transfer of electrons from the bacteria to the anode. Nanostructure-enhanced anodes have the potential to facilitate more efficient electron transfer for MiFCs because carbon nanostructures, such as nanofibers, possess outstanding conducting properties and increase the available surface area for cellular attachment. We have developed a novel nitrifying MiFC that contains a nanostructure-enhanced anode, which has successfully achieved power generation of 43 mW/m2 over 9 hours (comparable to early achievements by carbon MiFCs). Overall, this technology has the potential to significantly reduce wastewater treatment plant operating costs and make the larger-scale implementation of MiFC technology far more feasible. The outcome would be a technology that could generate enough electricity to power more than 100,000 homes (assuming 41% efficiency) off the ammonia in domestic sewage at treatment facilities across the United States (worth roughly $100 million/yr in energy production).

Nancy Love, nlove@vt.edu, 231-3980, Dept: Civil and Environmental Engineering00, Mail code: 0246, Affiliation: faculty

Jeremy Guest, jsguest@vt.edu, Dept: Civil and Environmental Engineering00, Mail code: 0246, Affiliation: graduate student

Sayangdev Naha, sayan@vt.edu, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: graduate student

Joshua Sole, jsole@vt.edu, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: graduate student

Ishwar Puri, ikpuri@vt.edu, 231-3243, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: faculty

Michael Ellis, mwellis@vt.edu, 231-9102, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

66: Self-Healing Composite Seal for Solid Oxide Electrolyzer/Fuel Cells

Sold oxide fuel cells (SOFC) show great promise for clean stationary power generation. SOFCs can have efficiencies of 60% or higher when combined with a gas turbine hybrid. They are presently being implemented in niche small-scale applications successfully, but suffer from long term durability. This is largely due to cracking in the gas seal between metal and ceramic components. Seals are placed between layers in a stacked SOFC which prevent the fuel and air from leaking or mixing. The sealant material has a strict set of requirements because it must be capable of being thermally cycled many times and able to withstand temperatures of 800-1000 °C while maintaining mechanical and chemical stability between components. Seals that have been researched include glasses, glass/ceramics, mica, Si-C-N polymers, and FeCrAlY, but all have drawbacks. This Department of Energy funded project focuses on developing a novel composite seal which integrates shape memory alloy wires into a glass/ceramic to create a durable gas seal which has self-healing capabilities. The wires are 3D printed, a rapid prototyping technique, into a mesh structure and then the glass/ceramic is infiltrated around the wires to create the composite seal. The wire mesh is designed so that the seal’s thermal expansion is similar to the components it is in contact with which helps prevent stress buildup in the seal causing cracking. Additionally, the shape memory alloy wires undergo a phase change at ~200 °C which will push the wires back into their original shape if they have been distorted by cooling and will heal cracks that may have formed. Currently, seals are being produced and tested over the Fall to examine their behavior. This project has the potential to significantly increase the lifetime and durability of SOFCs which is necessary for their wide-spread use.

Christopher Story, 540-231-9652, Dept: Materials Science and Engineering 00, Mail code: 0237, Affiliation: graduate student

Kevin Yu, 717-658-2749, Dept: Materials Science and Engineering 00, Mail code: 0237, Affiliation: undergrad

Kathy Lu, 540-231-3225, Dept: Materials Science and Engineering 00, Mail code: 0237, Affiliation: faculty

W.T. Reynolds, 540-231-6825, Dept: Materials Science and Engineering 00, Mail code: 0237, Affiliation: faculty

67: Multi-physics, Multi-scale Models: Low and High Temperature Fuel Cells

An objective of this work has been to develop comprehensive macroscopic and microscopic 2D and 3D models for high-temperature (Solid Oxide) and low-temperature (Proton Exchange Membrane) fuel cells. Modeling efforts include a wide range of 1D, 2D, and 3D macroscopic models for both PEMFC’s and SOFC’s ranging from single layer models (i.e. membrane and catalyst layer) to full cell models which take into account flow channel dynamics, water transport, reduced backing permeability due to water saturation, species diffusion through tortuous backing, and proton and electron transport throughout the fuel cell. Steady state macroscopic SOFC models have also been developed which account for mass, thermal, and charge transport in a planar SOFC. The SOFC model also includes electrochemical effects and the chemistry of internal fuel reforming. However, in order to overcome some of the inherent weakness of such macroscopic models in which the effects of the microstructure of the porous media on cell operation and performance is only taken into account by considering such media as homogeneous layers characterized by macroscopic, averaged parameters such as porosity and tortuosity, a series of steady-state microscopic continuum models of the cathode catalyst layer (active layer) of a proton exchange membrane fuel cell were developed. These models incorporate O2 species and ion transport while taking a discrete look at the placement of the carbon supported Pt particles within the electrode-catalyst layer. Another approach which is fully dynamic has been to use Kinetic Theory and the Boltzmann equation in combination with Lattice Boltzmann Methods in order to develop 2D and 3D models which deal with reactive gas mixtures, enabling the simulation of fluid flow in both PEMFC and SOFC catalyst layers.

Michael von Spakovsky, vonspako@vt.edu, 231-6684, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Mike Ellis, mwellis@vt.edu, 231-9102, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Douglas Nelson, doug.nelson@vt.edu, 231-4324, Dept: Mechanical Engineering, Affiliation: faculty

68: System/Component Modeling/Optimization for Fuel Cell System Synthesis/Design and Operational/Control

The focus of this work is the development of enabling design-for–the-environment tools for use in the synthesis/design and operational/control of PEMFC and SOFC technologies. The major tasks envisioned include i) developing fully transient nonlinear, general models of PEMFC and SOFC stacks and a variety of BOPS (balance-of-plant subsystems) components, ii) developing realistic load profile scenarios for various types of stationary and non-stationary applications for use in generating optimal control strategies for such systems; iii) implementing bottom-up and top-down approaches for the development of optimal control strategies; iv) including uncertainty considerations in the modeling and optimization process, and v) developing decomposition startegies for the large-scale dynamic optimization of system/component synthesis/design and operational control.

Michael von Spakovsky, vonspako@vt.edu, 231-6684, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Mike Ellis, mwellis, 231-9102, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Douglas Nelson, doug.nelson, 231-4324, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Donald Leo, donald.leo@darpa.mil, 571-218-4939, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

83: Synthesis of Carbon Nanotubes and Their Hydrogen Storage Capacity

The use of hydrogen as a fuel is limited in large part because of lack of progress in developing suitable storage and delivery systems. A benchmark has been set by the US Department of Energy (DOE) for hydrogen storage, which is 6.5 weight percent of the species in a storing material. Materials that adsorb significant quantities of hydrogen are therefore urgently needed. The special hydrogen adsorbing characteristics of carbon nanomaterials make them rather suited as hydrogen storage devices. Due to their high surface area and capillarity, carbon nanotubes (CNTs) can have high hydrogen storage capacity. We have simulated hydrogen storage in CNTs using molecular dynamics simulations to investigate their suitability for hydrogen storage. Based on our results, future directions to enhance hydrogen storage, such as electrochemical storage and metal ion encapsulation are suggested. We make a case that molecular simulation studies can identify the most promising structures and compositions to maximize hydrogen storage. Although research on CNTs is a fast-moving field, their commercialization is hampered by the lack of methods to economically produce the material in bulk, which requires a proper understanding of their growth and formation mechanisms. We present here a high-throughput and energy efficient flame synthesis method for the growth of CNTs. We have catalytically synthesized CNTs on metal (Ni, Co, Fe) substrates using a co-flow burner using ethylene as the fuel. The growth rate of these nanotubes has been modeled using a diffusion model that is coupled with results obtained from atomistic simulations. Detailed gas phase chemistry inside the flame, the surface chemistry influencing catalytic graphene growth, and the transport of carbon into the catalyst are considered and the growth rate predicted.

Soumik Banerjee, soumik@vt.edu, 5409217630, Dept: 14655, Mail code: 0219, Affiliation: graduate student

Sayangdev Naha, sayan@vt.edu, 773-343-7907, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: graduate student

Ishwar Puri, ikpuri@vt.edu, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: faculty

89: Investigations on the Durability of Proton Exchange Membrane Fuel Cells – Fundamental Studies and Perspectives

Fuel cells are energy devices that convert chemical energy into electrical energy. As a result of the electrochemical reactions occurring on the two electrodes, the fuel at the anode side is oxidized to release electrons, which are then transferred to the cathode side, reducing the oxidant species (usually oxygen). The flow of electrons during these electrochemical processes gives rise to current in the electrical circuit, while potential difference exists over the two electrodes based upon the nature of the redox reactions. The electrical energy obtained by fuel cells can be utilized in residential, stationary, adventure, distant communication and transport applications. The biggest advantage of fuel cell energy compared to traditional energy is its high efficiency. Unlike internal combustion and steam engines, heat exchange and mechanical work are no longer the major energy conversion methods. The electrons from the chemical reactions themselves are collected and conveyed directly to supply power. With the proper selection of fuel such as pure hydrogen, the fuel cell energy is fairly clean, showing great potential of contributing to the environmental pollution problem of modern industrial world. In spite of the potential, fuel cells have not been commercialized to a large extent after its first invention almost two hundred years ago. The two principal challenges to this commericialization are cost and durability. In this poster, novel approaches to proton exchange membrane fuel cell (PEMFC) durability research are summarized. These efforts are significantly different from most other studies on durability in that rather than focusing on chemical degradations, more attention is given to the mechanical aspects of the PEMFC system. The influence of uniaxial loading on proton conductivity of Nafion 117 membrane and sulfonated poly(arylene ether sulfone) random copolymer membrane with 35% of sulfonation (BPSH35) is also investigated. In addition, the long-term aging of hydrogen-air PEMFCs is examined with a cyclic current profile and under constant current conditions. A phenomenological mathematical model is set up to describe the PEMFC aging process under both cyclic and constant conditions. Finally, perspectives on the durability study of PEMFCs are presented, along with the ideas of improving fuel cell long-term performances with respect to materials design, membrane-electrode-assembly (MEA) manufacture and system configuration.

Scott Case, scase@exchange.vt.edu, 231-3140, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: faculty

Dan Liu, danl@vt.edu, 231-3139, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: graduate student

94: A High-Efficiency Power Conditioning System for Fuel Cells and Renewable Energies

Typical fuel cells and renewable energies have a low-voltage DC output. In order to make the energy available for household applications, a power conditioning system (PCS) is needed to convert low-voltage DC to high-voltage DC and then to high-voltage AC. Our example case is to convert the 26V-DC solid oxide fuel cell output to 400V-DC with a high-efficiency DC-DC converter and to 120/240V AC with a high-efficiency DC-AC inverter. The same PCS can also be used for the photovoltaic source to deliver power to either household appliances or utility grid connection. Virginia Tech Future Energy Electronics Center has developed a couple highly efficient PCS prototypes for US Department of Energy and has licensed key technology elements to two companies. This poster will show how PCS works and some test results.

Jason Lai, laijs@vt.edu, 231-4741, Dept: Electrical and Computer Engineering, Mail code: 0111, Affiliation: faculty

Jian-Liang Chen, jlchen99@vt.edu, 231-2159, Dept: Electrical and Computer Engineering, Mail code: 0111, Affiliation: graduate student

Seungryul Moon, semoon@vt.edu, 231-2159, Dept: Electrical and Computer Engineering, Mail code: 0111, Affiliation: graduate student

Sung Yeul Park, supark@vt.edu, 231-2159, Dept: Electrical and Computer Engineering, Mail code: 0111, Affiliation: graduate student

96: Synthesis and Characterization of Multiblock Copolymers based on Sulfonated Segmented Hydrophilic and Hydrophobic Blocks for Proton Exchange Membranes (PEMs)

Controlled molecular weight hydrophilic and hydrophobic blocks with primary amine and anhydride end groups were successfully synthesized. A series of segmented sulfonated poly(arylene ether)-B-polyimide multiblock copolymers having various block lengths were synthesized via coupling reaction between amine moieties on hydrophilic blocks and anhydride moieties on hydrophobic blocks. Successful imidization reactions require an NMP + m-cresol mixed solvent system and catalysis was essential. All copolymers give tough, ductile films when cast with a NMP solution. Several membrane parameters were investigated e.g. water uptake, proton conductivity, and methanol permeability. The new materials are strong candidates for PEM systems.

Hae-Seung Lee, hslee@vt.edu, Affiliation: graduate student

Anand Badami, abadami@vt.edu, Affiliation: graduate student

Abhishek Roy, aroy@vt.edu, Affiliation: graduate student

James McGrath, jmcgrath@vt.edu, Dept: chemistry, Affiliation: faculty

98: Involving Undergraduates in Research through an NSF REU Site: Materials and Processes for Proton Exchange Membrane Fuel Cells

Involving undergraduate students in meaningful research activities is an important part of their education. Positive experiences in research can influence career choices and often encourage pursuit of advanced degrees. Through the National Science Foundation's program on Research Experiences for Undergraduates, we have just completed our first of a three year award for an REU site on "Materials and Processes for Proton Exchange Membrane Fuel Cells". Ten undergraduate students participated in the 12-week summer program, each under the direction of a graduate student mentor and a faculty member. The diverse group of students came from VT and other well-known universities across the United States. All of them were exposed to working in a research environment and encouraged to consider graduate school, including at VT. In addition to their research, students participated in a short course to prepare them for their research, a weekly communication program designed to enhance their written and oral communication skills, and a focused seminar program involving experts from VT and from industry. Research topics ranged from using waste water bacteria to develop a functioning fuel cell to digital image correlation techniques to characterize membrane deformations to synthesis of membranes with improved performance and durability to techniques for recovering catalyst at end of life. This poster will provide an overview of the program as well as highlight the research of several of the students. The Macromolecules and Interfaces Institute helped to administer this REU program along with several others, allowing for a total of nearly 40 undergraduate participants in the summer of 2006.

David Dillard, dillard@vt.edu, 231-4714, Mail code: 0219, Affiliation: faculty

Michael Ellis, mwellis@vt.edu, 231-9102, Affiliation: faculty

100: Partially Fluorinated Hydrophilic-Hydrophobic Multiblock Copolymers for Proton Exchange Membrane in Fuel Cells

Fluorine terminated poly(arylene ether ketone) (6FK) hydrophobic oligomers with controlled molecular weights were synthesized via step growth polymerization based on 4, 4’-Hexafluoroisopropylidenediphenol (6F BPA) and 4,4’-difluorobenzophenone (DFBP), while phenoxide terminated disulfonated poly(arylene ether sulfone) (BPSH) hydrophilic oligomers were prepared based on biphenol and 3,3’-Disulfonated 4,4’-dichlorodiphenyl sulfone (SDCDPS). Multiblock copolymers containing hydrophobic (6FK) and hydrophilic (BPSH) segments were synthesized by polycondensation of two oligomers with functional terminal groups. The compositions of the multiblock copolymers can be controlled by varying the two oligomers’ sequence length. 19F and 1H NMR spectra were used to characterize the oligomer molecular weights and multiblock copolymer’s structure. The protonic conductivity, water uptake, and the morphology are a function of relative humidity (RH), which will be discussed

Yanxiang Li, lyxiang@vt.edu, 5402318224, Dept: Chemistry, Mail code: 0212, Affiliation: graduate student

102: Characterizing Strength and Fracture Properties of Proton Exchange Membranes

Abstract: Pinhole formation in the proton exchange membrane (PEM) can lead to gas crossover, reducing fuel cell efficiency. Environmental factors, cyclic operation, and the resulting stress state may all contribute to membrane degradation and pinhole formation. We are exploring the use of both strength and fracture mechanics concepts to gain insights into membrane failure and durability. This poster will review progress made in characterizing the biaxial strength of commercial proton exchange membranes. In addition, a knife slit test has been adapted in an effort to determine the fracture energy of the membranes, wherein the presence of a sharp knife blade reduces crack tip plasticity, providing fracture energies that may be more representative of the intrinsic fracture energies of thin membranes. Moisture and temperature are shown to have a significant effect on both the strength and fracture properties. This work is part of a suite of characterization and modeling tools being jointly developed by General Motors and Virginia Tech.

David Dillard, dillard@vt.edu, 231-4714, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: faculty

Scott Case, scase@vt.edu, 231-3140, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: faculty

Michael Ellis, mwellis@vt.edu, 231-9102, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Ron Li, li233@vt.edu, 231-7485, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: graduate student

Kshitish Patankar, kpatankar@vt.edu, 231-7484, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: graduate student

Michael Pestrak, msp@vt.edu, 231-7485, Dept: 016300, Mail code: 0201, Affiliation: graduate student

Jake Grohs, jrgrohs@vt.edu, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: undergrad

Nyssa Glenn, nglenn@vt.edu, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: undergrad

Elisa Campbell, cmpbele@vt.edu, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: undergrad

Yeh-Hung Lai, yeh-hung.lai@gm.com, Affiliation: faculty

Michael Budinski, michael.budinski@gm.com, Affiliation: faculty

Craig Gittleman, craig.gittleman@gm.com, Affiliation: faculty

103: Characterizing the Constitutive Properties of Proton Exchange Membranes

The proton exchange membranes of operating fuel cells are exposed to significant changes in temperature and moisture content. Because of the significant time, temperature, and moisture dependence, a complex stress state profile is induced within these membranes because of the fixed boundary conditions imposed by the gas distribution layers and bipolar plates. In order to understand the effects of these stresses on membrane integrity, it is important to be able to predict the stress state that will result under anticipated operating conditions. In this poster we will discuss the development of linear viscoelastic constitutive models for commercial proton exchange membranes. A dynamic mechanical analyzer, equipped with a custom environmental chamber, is used to collect relaxation modulus for small membrane strips subjected to stress relaxation loading conditions. Properties are obtained over a range of temperature and humidity conditions. Predictive models have been developed to use these properties to predict membrane behavior. In addition, a unique instrument has been fabricated for simultaneously characterizing the mass uptake and dimension changes in membranes exposed to various temperature and humidity conditions. These studies are providing additional insights into the mechanical properties of proton exchange membranes. This work is part of a suite of characterization and modeling tools being jointly developed by General Motors and Virginia Tech.

David Dillard, dillard@vt.edu, 231-4714, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: faculty

Scott Case, scase@vt.edu, 231-3140, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: faculty

Michael Ellis, mwellis@vt.edu, 231-9102, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: faculty

Yeh-Hung Lai, yeh-hung.lai@gm.com, Affiliation: faculty

Michael Budinski, michael/budinski@gm.com, Affiliation: faculty

Craig Gittleman, craig/gittleman@gm.com, Affiliation: faculty

Kshitish Patankar, kpatankar@vt.edu, 231-7484, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: graduate student

Will Smith, wgsmith@vt.edu, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: graduate student

Robert Gaines, gainesr@vt.edu, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: undergrad

Nyssa Glenn, nglenn@vt.edu, Dept: Engineering Science and Mechanics, Mail code: 0219, Affiliation: undergrad

Hunter Moore, hmoore@vt.edu, Dept: Mechanical Engineering, Mail code: 0238, Affiliation: graduate student

Sooja Park, Affiliation: faculty

111. Clathrate Hydrates: Unexplored Source of Natural Gas, Energy Storage, and Environmental Impact

Clathrate hydrates are unique compounds formed by the ydrogen bonding of water molecules, which assemble into crystalline, non-stoichiometric structures. These structures enclose a large number of different types of molecules, such as, light hydrocarbons, carbon dioxide, fluorinated compounds, hydrogen, and many others. There many practical applications for clathrate hydrates, the most prevalent being in the energy, environment, and storage areas. In the energy area, natural hydrate deposits are estimated to contain 20,000 trillion cubic meters of gas (mostly methane) or about two orders of magnitude greater than found in all other conventional sources of carbon. While methane hydrate deposits are potential energy resources, they are also of great environmental concern, since methane is a potent greenhouse gas (several times more harmful than carbon dioxide), and the stability of hydrate deposits is of grave concern to the environment. In the energy storage area, hydrates provide a medium to store gases as the density of guests in a hydrate volume is about 180 times that of a fluid at the same conditions. More recently, hydrates have been investigated as a potential medium for storage of hydrogen. Our research is studying several fundamental aspects of hydrates to better understand and predict their thermophysical and kinetic properties. By applying a multidisciplinary approach to this problem, our goal is to build a broad knowledge base on hydrates to more effectively address their application in the above mentioned areas.

Amadeu K. Sum, asum@vt.edu, 231-7869, Dept: Chemical Engineering, Mail code: 0211, Affiliation: faculty

Manufacture of Poly (arylene sulfone) Copolymer Films for Proton Exchange Membranes for Fuel Cells by Reverse Roll Coating and Film Drying Processes

Membranes are typically prepared in the laboratory by a batch solution casting process for the preliminary evaluation of their performance. However, commercial production-scale manufacture of the membranes cannot be achieved by the same batch process because the production rate is too low, and the requirements for the physical shape of the membranes such as thickness and uniformity cannot be easily satisfied, especially for the application of fuel cell (FC) proton exchange membranes (PEM). So, it is vital to develop and optimize a continuous process for the manufacture of poly (arylene sulfone) copolymer films for FC PEM. Reverse roll coating of polymer solution followed by film drying seems to be the most promising because of its good production rate and control capability of film thickness. The thickness of film coated on the substrate and its stability depend on the properties of polymer solution (viscosity, primary normal stress difference, surface tension), operating variables (substrate speed, roll speed), and geometric variables (roll diameter, gap between the roll and substrate). The drying conditions such as temperature, velocity and humidity of drying air, and substrate determine the structure and properties of final product films. Therefore, it is the primary objective of this study to obtain a uniform poly (arylene sulfone) copolymer film without any defects and to remove the solvent with a high rate. A model for the reverse roll coating which relates the film thickness and aforementioned controlling parameters will be developed and a model which enables to predict the drying time and dryer length will be also developed.

Myoungbae Lee and Donald G. Baird, 231-5998, dbaird@vt.edu, Dept. Chemical Engineering

114: Development of Compression Moldable Polymer Composite Bipolar Plates for Fuel Cells

Bipolar plates are by weight, volume, and cost the most significant contributor in a fuel cell stack. The major cost issue in the mass production of bipolar plates is their poor economical ability to be processed readily. There are numerous materials used to produce a bipolar plate that vary in their strength, ability to conduct current, and most importantly machining or forming costs. Polymer composite plates developed by a wet-lay process have exhibited excellent mechanical properties and improving conductivity properties. The advantage in using polymer composites is the desired use of compression molding to form channels directly into preforms quickly. A laminate structure is proposed in an effort to improve the existing through-plane conductivity, formability, and half-cell resistance of wet-lay based polymer composite bipolar plates.

Brent David Cunningham, Macromolecular Science & Engineering, brcunni1@vt.edu

115: Ordered Carbon Nanotube/Polymer Nano-composite Membranes for Gas Separations (hydrogen purification)

Recent molecular simulation and theoretical studies of single walled carbon nanotubes (SWNT) have indicated that these materials are predicted to have both high selectivities and very high fluxes for gas transport. Oriented multi-walled carbon nanotube (MWNT) and double-walled carbon nanotube (DWNT) membrane have been fabricated by several research groups. The gas permeabilities and water flux of DWNT membranes with a 1.6 nm pore diameter were higher than those of commercial polycarbonate membranes having 15 nm pore size by several orders of magnitude. However, these reported carbon nanotubes (CNTs) membranes are not commercially attractive because of complex and costly fabrication procedure and limited surface area. In this study, in order to overcome disadvantages of chemically grown CNTs membranes, we have developed a simple, fast, commercially attractive, and scalable filtration method to prepare oriented CNTs membrane with large surface area. The oriented single-walled carbon nanotube (SWNT) membrane sample showed higher permeability by one order of magnitude than the value predicted by the Knudsen model. Another unique feature of these membranes is that various functional groups can be attached to CNTs end tips. The various amino groups (-NH 2) on the nanotube pore entrance provide the sites for CO 2 adsorption and facilitate its separation from N 2 and CH 4. The amine functionalized SWNT membrane shows higher selectivities of CO 2 over other gas molecules because of preferential interaction of CO 2 with the nanotubes demonstrating practical applications in gas separations.

Sangil Kim, sikim@vt.edu, 231-6276, Chemical Engineering, graduate student; Eva Marand, emarand@vt.edu, 231-8231, faculty.