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Ramirez, Steven AbrahamSupervisory Control Validation of a Fuel Cell Hybrid Bus Using Software-in-the-Loop and Hardware-in-the-Loop Techniques
Master of Science, The Ohio State University, 2013, Mechanical Engineering
The work presented within this thesis consists of the validation of a supervisory controller and vehicle simulator for the ECO Saver IV demonstration bus being developed as part of the National Fuel Cell Bus Program (NFCBP). The goal of the NFCBP is to develop fuel cell transit buses such that a U.S. industry for fuel cell bus technology can be established through both technology innovation and increased public awareness of fuel cell vehicles. The use of fuel cells in vehicles is desirable due to their high efficiencies and zero emissions, allowing the transportation sector to rely less heavily on petroleum and carbon based fuels that emit hazardous greenhouse gases. The ECO Saver IV, as designed by the DesignLine Corporation through a contract with the Center for Transportation and the Environment, is a battery dominant fuel cell hybrid bus that takes advantage of the benefits of hybridization in conjunction with the benefits of the fuel cell. The team of researchers at The Ohio State University (OSU) Center for Automotive Research (CAR) served as a subcontractor to develop a supervisory controller and fuel cell hybrid bus simulator, modeled after the chosen powertrain architecture. The validation performed involved the use of software-in-the-loop and hardware-in-the-loop simulations, where the results were compared to baseline model-in-the-loop simulations. The driving conditions of the intended application of the demonstration bus, i.e., integration into the OSU Campus Area Bus Services (CABS) fleet, were taken into consideration through the development of real-world drive cycles that were representative of actual CABS bus routes. A new driver model was developed that solved issues related to tracking distance, velocity and road grade to enable the use of real-world drive cycles. The results of the validation are to be used in the final phases of development and construction of the ECO Saver IV fuel cell hybrid transit bus to prove the effectiveness of using the developed control algorithm within the bus’ control hardware. To aid in the evaluation phase of the demonstration bus project, a CAN based data acquisition system was developed and tested on the HIL test bench. The logged data will be used to evaluate the successfulness of the fuel cell hybrid transit bus while providing evidence of the viability of such a vehicle.

Committee:

Shawn Midlam-Mohler, Dr. (Advisor); Yann Guezennec, Dr. (Committee Member)

Subjects:

Automotive Engineering; Engineering; Mechanical Engineering

Keywords:

Fuel Cell; Hybrid; Bus; Hardware in the Loop; HIL; Software in the Loop; SIL; supervisory control; data acquisition; National Fuel Cell Bus Program; real world drive cycle

Ghosh, UjjalOne dimensional modeling of planar solid oxide fuel cell
Master of Science (MS), Ohio University, 2005, Mechanical Engineering (Engineering)
Using modeling and simulation, the present work offers parametric study for Planar Solid Oxide Fuel Cell (PSOFC) as a function of fuel gas composition. The study comprises of one-dimensional steady and dynamic state modeling of single PSOFC in Aspen Custom Modeler. The simulations are performed at the interface of fuel channel and anode, and the reaction kinetics, the spatial distributions of temperature and specie concentrations inside the PSOFC are calculated. Steady state model estimates the cell performance as function of CO, and the dynamic model estimates the transient performance degradation, due to Area Specific Resistance (ASR) degradation. Additionally, the dynamic model analyzes the sensitivity of cell performance on input variables, and recovery time for the small variations. The analysis shows that temperature, current density, flow-rate, ASR and fuel composition affect the cell performance. At low current densities, the cell performances are comparable, up to 80% CO in the fuel gas.

Committee:

David Bayless (Advisor)

Subjects:

Engineering, Mechanical

Keywords:

One Dimensional Modeling; Planar Fuel Cell; Solid Oxide Fuel Cell

Gaone, Joseph MichaelA Mathematical Model of a Microbial Fuel Cell
Master of Science, University of Akron, 2013, Applied Mathematics
In this study a microbial fuel cell (MFC) computational model is developed. The purpose is to establish a one dimensional MFC model, at steady state, that contains a biofilm, anode, membrane, and cathode region and uses a conductive biofilm matrix that depends on pH. Biomass equations, chemical equations, and potential equations are developed to model the operation of each compartment. Numerics are utilized to solve the various sets of ordinary and partial differential equations. We examine the efficiency and optimization of this MFC. A parameter study was performed on this model to compare the results to previous models and experiments for validation and to observe the effects of new contributions. The results show that a non-constant conductivity is vital to MFC operation if large variation in pH is expected. Applied potential was found to be optimal at the lowest possible value that does not inhibit electron transport to the cathode. Electric potential can be maximized by making the distance between electrodes as small as possible to reduce the resistance. These features are essential in order to maximize efficiency and power output of an MFC. This model and investigation are significant because it unifies previously separate anode and cathode models as well as establish the basis of including pH dependent non-constant conductivity in MFC models.

Committee:

Gerry Young, Dr. (Advisor); Curtis Clemons, Dr. (Advisor); Kevin Kreider, Dr. (Advisor); J. Patrick Wilber, Dr. (Advisor)

Subjects:

Biochemistry; Mathematics

Keywords:

MFC; microbial fuel cell; conductive biofilm matrix; biofilm; fuel cell; mathematical model; computational model; model; nanowire; conductive nanowires

Gardner, PaulAerosol Jet Printing of LSCF-CGO Cathode for Solid Oxide Fuel Cells
Master of Science (MS), Wright State University, 2011, Chemistry
Solid oxide fuel cell (SOFC) technology has attracted great attention due to advantages such as low emissions and high efficiency. In this work, solid oxide fuel cells were fabricated by incorporating functional layers deposited by a novel aerosol jet® printing method. The buffer and cathode layers were printed from gadolinium doped ceria (Ce0.9Gd0.1)O1.95 (CGO) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) inks, respectively. The CGO layer was deposited on the sintered electrolyte and then LSCF was subsequently deposited onto the CGO layer. The polarization curves showed a 19% improvement in current density using LSCF as the cathode instead of LSM. Cathode grain size was shown to change by 85% over the sintering temperatures examined. Lastly, the effect that ethyl cellulose additive had on the resulting cathode was determined. It was discovered that the porosity of the microstructure was not correlated to the additive's molecular weight. The actual causes of the cathode porosity may be the order of polymer branching or the ethoxy content of the ethyl cellulose.

Committee:

Eric Fossum, PhD (Advisor); David Grossie, PhD (Committee Chair); Rachel Aga, PhD (Committee Chair)

Subjects:

Chemistry

Keywords:

solid oxide fuel cell; SOFC; LSCF; cathode; LSM; fuel cell; aerosol jet; aerosol jet deposition; aerosol jet deposition technique; Optomec; AJDT;

Rottmayer, Michael AProcessing and Properties of Nanocomposite Thin Films for Microfabricated Solid Oxide Fuel Cells
PhD, University of Cincinnati, 2017, Engineering and Applied Science: Materials Science
Microfabricated solid oxide fuel cells (mSOFCs) have recently gained attention as a promising technology, with the potential to offer a low temperature (as low as 300°C), reduced start-up time, and improved energy density for portable power applications. At present, porous Pt is the most common cathode being investigated for mSOFCs. However, there are significant technical challenges for utilizing pure metallic electrodes at the operating temperatures of interest due to their tendency towards Ostwald ripening, as well as no bulk ionic conductivity. Nanocomposite materials (e.g. Pt/YSZ) are a promising alternative approach for providing both microstructural and electrochemical stability to the electrode layer. The overall objective of this research was to explore the processing of nanocomposite metal / metal oxide materials (i.e. Pt/YSZ) for use as a high performance cathode electrode for mSOFCs. The Pt/YSZ nanocomposite cathodes were deposited through a co-sputtering process and found to be stable up to 600°C in air for extended periods of time through an exhaustive materials and electrochemical study. A percolation theory model was utilized to guide the design of the Pt/YSZ composition, allowing for a networked connection of ionic- and electron-conduction through the membrane, leading to an extension of the triple phase boundary (TPB). The Pt/YSZ composite deposition pressure was found to be a key in helping to stabilize the morphology of the film. By increasing the deposition pressure, this led to the formation of intergranular void spacing, or porosity, as well as a reduction of film strain in the post-annealed film. Surface analyses of the composite film demonstrated that the lower film strain led to a minimization of Pt hillock grain coarsening and de-wetting, even after exposure to high temperatures (600°C) for extended periods of time (tested up to 24hrs) in air. Analyses of the Pt/YSZ composite microstructure and composition by TEM confirmed an interconnected network of Pt and YSZ was maintained through the film’s thickness after exposure to high temperatures in air. A significant improvement in the stability of the electrical conductivity was demonstrated relative to the Pt electrodes, tested under constant current measurement conditions for up to 24hrs at 600°C. mSOFC testing results revealed that interconnectivity or percolation of the Pt and YSZ through the composite cathode was achieved, effectively leading to an increase in the TPB length, or increase in reaction sites for the oxygen reduction reaction to occur. The activation energy associated with the oxygen reduction reaction charge transfer kinetics in the Pt/YSZ was shown to be lower than a pure porous Pt electrode, along with a significant improvement in stability of the morphology during extended mSOFC operation. Mass diffusion of oxygen through the cathode to the TPB was found to be the rate determining step in the oxygen reduction reaction process. A further increase in porosity in the Pt/YSZ cathode should result in more efficient oxygen diffusion and a higher performance mSOFC cathode.

Committee:

Raj Singh, Sc.D. (Committee Chair); Relva Buchanan, Sc.D. (Committee Member); Hong Huang, Ph.D. (Committee Member); Rodney Roseman, Ph.D. (Committee Member)

Subjects:

Materials Science

Keywords:

micro fuel cell;solid oxide fuel cell;composite;thin film;nanomaterial;sputtering

Stuckey, Philip A.Kinetic Studies and Electrochemical Processes at Fuel Cell Electrodes
Doctor of Philosophy, Case Western Reserve University, 2011, Chemical Engineering
Kinetic parameters that describe the operating efficiency and rate of a reaction are revealed in situ by applying normal pulse voltammetry to normally operating proton exchange membrane fuel cells. The Tafel slope for the oxygen reduction reaction is directly extracted from the steady state chronoamperometric response. Conditioning potential, temperature, and relative humidity are varied independently to observe their effect on the Tafel slope. Aqueous ex situ techniques commonly used to collect kinetic data only mimic the conditions within fuel cell and are unable to capture true operating processes, especially the effects of relative humidity. The observed Tafel slopes are 47-62 mV/decade for oxide covered platinum indicating a smaller activation overpotential than that for oxide free platinum with Tafel slopes of 91-119 mV/decade in initial studies. High temperature operation at 120°C showed no kinetic or mechanistic benefit compared to fuel cell operation at 80°C. If high efficiency is desired, the fuel cell should be operated in a potential range where oxide is present on the platinum surface. A novel technique is presented using pulse voltammetry measure platinum oxide coverage in situ on PEMFC electrodes. A linear logarithmic rate was noticed for oxide conditioning times longer than 1 second. Extended testing of relative humidity effects at 80 °C, combined with electrochemical active surface area measurements to normalize the oxide growth, showed a growth rate of 28 μC cm-2 (log s)-1 and also provided the ability to monitor platinum dissolution from the electrode. Concepts from both these projects are assimilated to develop novel pulse voltammetry waveforms that are applied in situ on normally operating proton exchange membrane fuel cells to reveal Tafel kinetics with control of adsorbed oxide on platinum. The results show that the Tafel slope decreases with increasing platinum oxide coverage on the electrode. The oxidation of higher order polyols such as glycerol would have profound impacts in the fuel cell arena considering the abundance of glycerol and its low price in the marketplace. Glycerol would provide a fuel with higher energy density than hydrogen. Preliminary results from glycerol oxidation studies on Pt, Pt-Ru, and Pt-Cr are reported.

Committee:

Thomas Zawodzinski, Jr. (Advisor); Jay Mann, Jr. (Committee Chair); Mohan Sankaran (Committee Member); David Schiraldi (Committee Member)

Subjects:

Alternative Energy; Analytical Chemistry; Chemical Engineering; Energy; Engineering; Mechanical Engineering

Keywords:

Fuel cell; electrochemistry; pulse voltammetry; Tafel slope; oxygen reduction reaction; platinum; oxide; in situ; kinetics; proton exchange membrane fuel cell; normal pulse voltammetry; chronocoulometry; chronoamperometry; glycerol; hydrogen

Siengchum, TrittiStudy of Direct Utilization of Solid Carbon and CH4/CO2 Reforming on Solid Oxide Fuel Cell
Doctor of Philosophy, University of Akron, 2012, Chemical Engineering
This study demonstrates the feasibility and optimization of utilizing carbon and CH4 to generate electricity with solid oxide fuel cell (SOFC). Carbon sources including coconut shell biomass, coal, coke injecting into the anode compartment of the SOFC were heated rapidly. The detail reactions that occur on the carbon during this process were studied in the Chapter 4, fast pyrolysis of coconut biomass. The products of biomass fast pyrolysis consist of char, liquid and gases. The utilization of CH4 and CO2, which are the major pyrolysis products, was investigated in Chapter 5 with Rh-modification of the SOFC anode. The purpose of Rh-modification is to avoid carbon deposition in the anode matrix by promoting the dissociation of CO2, as a result, increasing the rate of carbon oxidation. The importance of the rate of carbon electrochemical oxidation has been highlighted in the study of carbon-based SOFC in Chapter 3. The rate of carbon oxidation and CO oxidation was studied as a function of operating current density of carbon-based SOFC with Ag impregnated Ni/YSZ anode. Chapter 3 reports the study of evolution of gases from direct utilization of carbon in a solid oxide fuel cell (C-SOFC) with coconut carbon, a carbonaceous material with low ash and sulfur content. The addition of CO2 to the anode chamber increased CO formation and maximum power density from 0.09 Wcm-2 to 0.13 Wcm-2, indicating the occurrence of Boudouard reaction coupling with CO electrochemical oxidation on the C-SOFC. Analysis of CO and CO2 concentration as a function of current and voltage revealed that electricity was mainly produced from the electrochemical oxidation of carbon at low current density and produced from the electrochemical oxidation of CO at high current density. The operating efficiencies of SOFC operated with coconut carbon and Ohio coal was evaluated to be less than 2 % in Chapter 4. This low efficiency was mainly due to gaseous product of carbon pyrolysis leaving the anode chamber unreacted, which lead to the study of fast pyrolysis. The fast pyrolysis reactions occur on the carbon fuel during the feeding step into the SOFC at high temperature. The reaction pathway of coconut shell fast pyrolysis was studied by analysis of the transient evolution product profiles as a function of temperature, measured directly in the sample bed. Fast pyrolysis of coconut shell produced (i) pyrolysis liquid containing C-H, C=O, and C-O-C bands, (ii) char with the absence of C-OH and C=O suggesting that ether and carbonyl compounds were decomposed below 600 °C, and (iii) gaseous product majorly consisting of CO2. The results of this study suggest the importance of utilization of gaseous species of fast pyrolysis, i.e., CH4, CO, CO2, and H2. The utilization of CH4 and CO2 to produce electricity was studied in SOFC comprising a Ni/YSZ anode impregnation of Rh. The Rh-Ni/YSZ anode SOFC and Ni/YSZ anode SOFC were tested simultaneously in the multiple SOFC reactor under flowing CH4/CO2. Exposure of the Ni/YSZ anode SOFC to CH4/CO2 produced a maximum power density that degraded from 0.06 to 0.01 W/cm2 after 41 h. Impregnation of Rh at 0.01 and 0.03 wt.% onto the Ni/YSZ anode produced the Rh-Ni/YSZ anode that exhibited a maximum power density of 0.06 and 0.08 W/cm2 , respectively, for more than 185 h. Extensive testing of SOFC with various concentration of Rh in H2/Ar and CH4/CO2 suggests the optimum Rh concentration of 0.07 ' 0.10 wt%

Committee:

Steven Chuang, PhD (Advisor); Jie Zheng, Dr. (Committee Member); Nic D. Leipzig, Dr. (Committee Member); Guo-Xiang Wang, Dr. (Committee Member); Stephen Z. Cheng, Dr. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

SOFC; CH4; CO2 reforming; Rh; carbon fuel cell; fuel cell; fast pyrolysis; coconut shell

Rismani-Yazdi, HamidBioconversion of Cellulose into Electrical Energy in Microbial Fuel Cells
Doctor of Philosophy, The Ohio State University, 2008, Food Agricultural and Biological Engineering

In microbial fuel cells (MFCs), bacteria generate electricity by mediating the oxidation of organic compounds and transferring the resulting electrons to an anode electrode. The objectives of this study were to: 1) test the possibility of generating electricity in an MFC with rumen microorganisms as biocatalysts and cellulose as the electron donor, 2) analyze the composition of bacterial communities enriched in cellulose-fed MFCs, 3) determine the effect of various external resistances on power output and coulombic efficiency of cellulose-fed MFCs, 4) evaluate bacterial diversity and cellulose metabolism under different circuit loads, 5) assess the influence of methane formation on the performance of cellulose-fed MFCs under long-term operation, and 6) characterize the diversity of methanogens in cellulose-fed MFCs.

The results demonstrate that electricity can be generated from cellulose by exploiting rumen microorganisms as biocatalysts. Cloning and analysis of 16S rRNA gene sequences indicated that the most predominant bacteria in the anode-attached consortia were related to Clostridium spp., while Comamonas spp. abounded in the suspended consortia. Results suggest that oxidation of metabolites with the anode as an electron sink was a rate limiting step in the conversion of cellulose to electricity in MFCs.

This study also shows that the size of external resistance significantly affects the bacterial diversity and power output of MFCs. A maximum power density of 66 mW/m2 was achieved by the 20-ohm MFCs, while MFCs with 249, 480 and1000 ohms external resistances produced 57.5, 53 and 47 mW/m2, respectively. Thus the external resistance may be a useful tool to control microbial communities and consequently enhance performance of MFCs.

Furthermore, this study demonstrates that methanogenesis competes with electricity generation at the early stages of MFC operation but operating conditions suppress methanogenic activity over time. The suppression of methanogenesis was accompanied by a decrease in the diversity of methanogens and changes in the concentration of short chain fatty acids.

An improved understanding of the microbial communities, interspecies interactions and processes involved in electricity generation is essential to effectively design and control cellulose-fed MFCs for enhanced performance. In addition, technical and biological optimization is needed to maximize power output of these systems.

Committee:

Ann Christy, PhD (Advisor); Burk Dehority, PhD (Committee Member); Olli Tuovinen, PhD (Committee Member); Alfred Soboyejo, PhD (Committee Member); Zhongtang Yu, PhD (Committee Member)

Subjects:

Agricultural Engineering; Chemical Engineering; Energy; Environmental Engineering; Environmental Science; Microbiology

Keywords:

Microbial fuel cell; biofuel cell; cellulose degradation; renewable energy; rumen microorganisms; 16S rRNA; DGGE; cellulose; alternative energy; external resistance; circuit load; bacterial diversity; methane; methanogenesis; archaea

Kuhn, JohnInvestigation of catalytic phenomena for solid oxide fuel cells and tar removal in biomass gasifiers
Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering
Solid oxide fuel cells (SOFCs) show promise for generating clean power from a variety of fuels. The major roadblocks to their implementation are a large cathodic resistance, which causes insufficient power densities and high fabrication costs, and anodic deactivation caused by carbon-based fuels such as coal and biomass-derived gases and their sulfur impurities. The large cathodic resistance is caused by slow oxygen activation kinetics and oxide ion transport of the current manganite-based cathode. At the anode, deactivation occurs through the conventional nickel-based material’s poor sulfur tolerance and tendency to form carbon fibers. Thus, the development of catalytically active materials suitable for use as electrodes is needed to help SOFCs realize their full potential. Replacing manganite with reducible transition metals (e.g., cobalt) leads to mixed (electronic and ionic) conductivity and improved performance through the enlargement of the electrochemically active area. However, further improvements are limited because the oxygen reduction kinetics and oxygen-surface interactions are poorly understood. The present work examines the catalytic phenomena of doped-lanthanum ferrites for use as cathode materials in intermediate temperature (500 and 800°C) applications. The kinetics and energetics of the oxygen reduction reaction is related to surface and bulk structural changes that occur as a function of environment and dopant levels. The current research also focuses on understanding deactivation of conventional anode materials in the presence of carbon fuels with sulfur impurities. The results show formation of adsorbed sulfur and surface sulfides even when the bulk phase is stable. The use of this information to modify conventional anode materials is still an active area of research. Characterization is performed by XRD, XPS, and vibrational spectroscopy to complement the oxidation results. Since gasification of biomass takes place in a fluidized bed reactor, attrition resistance is important to eliminate the loss of catalyst. Dolomite catalysts have been tried, but generally are not attrition resistant. With our collaborators, the use of Ni-doped olivine catalysts is examined. These catalysts have proved to be attrition resistant and possess adequate reforming activity.

Committee:

Umit Ozkan (Advisor)

Keywords:

solid oxide fuel cell; perovskite; Ni-YSZ; biomass gasification; tar removal; Ni-olivine

Shan, XiHydrogen Storage for Micro-fabricated Electrochemical Devices
Doctor of Philosophy, Case Western Reserve University, 2004, Materials Science and Engineering
Micro-fabricated PEM fuel cells and other micro-power systems are being developed to provide on-board electrical power source for MEMS systems. The development of these micro-power systems needs a hydrogen source that has high volume density, fast hydriding/de-hydriding kinetics and can be easily activated under atmosphere pressure at room temperature. In this investigation, the effects of palladium on the hydrogen storage properties of LaNi4.7Al0.3, CaNi5 and Mg2.4Ni were studied. It is found that mechanical grinding these alloys with palladium can lower the activation pressures to sub-atmosphere at room temperature and significantly increase hydriding/de-hydriding kinetics; the activation durability of these alloys in air is also greatly extended to more than 2 years. The hydride ink making process, in which polymer binders are added to the 10wt% palladium modified alloy, slightly decreases the storage capacity, but the alloy is still active under atmospheric pressure at room temperature. The cyclic hydriding/dehydriding stabilities of palladium modified alloys under pure and humidified hydrogen were studied. After 5000 cycles under pure hydrogen, the storage capacities of 10wt% palladium modified LaNi4.7Al0.3 and CaNi5 decrease 14-20% and 30-35% respectively. For test under hydrogen with 75% relative humidity, the storage capacity of 10wt% palladium modified LaNi4.7Al0.3 decreases 60% after 3000 cycles. The degradation of LaNi4.7Al0.3 is mainly due to the oxidation caused by air exposures during the test or water vapor in the hydrogen; for CaNi5, disproportionation of CaNi5 is the main reason. The mechanism of palladium on the activation and hydriding/de-hydriding of the alloys can be explained by hydrogen spillover and reverse hydrogen spillover. When inks made with 10wt% palladium modified LaNi4.7Al0.3 and CaNi5 were used as the hydrogen source for PEM fuel cell, the maximum currents they can provide exceed the requirement for the micro-fabricated PEM fuel cell system, the electric energy capacities of the LaNi4.7Al0.3 and CaNi5 are 120Wh/kg and 110Wh/kg respectively. The efficiency of hydrogen from LaNi4.7Al0.3 is more than 90%, while for CaNi5 the efficiency is only 60% due to its low de-hydriding plateau pressure

Committee:

Joe Payer (Advisor)

Subjects:

Engineering, Materials Science

Keywords:

hydrogen storage; fuel cell; spill over

Dong, DaxuanPolyphenylene Sulfonic Acids As Proton Exchange Membranes For Fuel Cells
Doctor of Philosophy, Case Western Reserve University, 2012, Chemistry

High molecular weight poly(biphenyl-3,3’-disulfonic acid) (PBPDSA) homopolymer was synthesized using the Ullmann coupling reaction. The molecular weight of PBPDSA was improved by changing the solvent, counter ion and drying method. A water insoluble copolymer PBPDSA-g-NPB was obtained by grafting PBPDSA with neopentylbenzene (NPB). The proton conductivity of this film was 0.114 S/cm at 50%RH and 80oC, which is higher than the initial DOE target 0.1 S/cm.

In order to further improve the conductivity, a novel copolymer poly(phenylene disulfonic acid_co-fluorene disulfonic acid) (PxF1)was designed and synthesized. PxF1 was synthesized by reacting 1,4-dibromobenzene-2,5-disulfonic acid (DBPDSA) and 2,7-dibromofluorene-3,5-disulfonic acid (DBFDSA) using the Ullmann coupling. This copolymerization was optimized by screening temperature, solvent, coordination reagent and drying method. The best conditions are DBPDSA-Li, DBFDSA-Li and copper dried separately under vacuum and then together under an argon steam at 200oC and copolymerized in NMP at 200oC using 2,2’-bipyridine (BPy) as a coordination reagent. In order to obtain water insoluble membranes, PxF1 was further grafted with benzyl groups and crosslinked.

PxF1 and its grafted copolymers exhibited an abnormal increase in reduced viscosity at low concentrations. The Polarizing Optical Microscopy (POM) studies, the film dimensional changes as a function of relative humidities and WAXD measurements are consistent with a nematic liquid crystalline structure.

A copolymer hexagonal packing model was proposed and verified by studying the relationship between the calculated molar volume and the measured molar volume using a curve fitting program. The use of WAXD combined with measurements of volume and weight increase for copolymer as a function of relative humidity enabled us to make a direct estimate of frozen-in free volume. The frozen-in free volume from this analysis is 32.0 cc/SO3H (λ = 1.8) for P10F1 and 32.1 cc/SO3H (λ = 1.8) for P10F1-g-Bn27% (4-46).

The in plane proton conductivity of these materials, measured as a function of relative humidity and temperature, was 10 times higher than that of Nafion212®. TGA study indicates that the copolymers are stable up to 304oC. The mechanical properties of those copolymers are affected by the grafting degree and relative humidity. The grafted copolymer has reasonable mechanical properties (breaking stress 13.3 MPa at 6.6% strain) at 23%RH.

Committee:

Morton H. Litt, PhD (Advisor)

Subjects:

Polymer Chemistry

Keywords:

fuel cell; proton exchange membranes; polyphenylene; Ullmann reaction

Moolsin, SupatCyclotriphosphazenes and Polyphosphazenes with Azolylphenoxy and Aminophenoxy Side Groups as Fuel Cell Membrane Candidates
Doctor of Philosophy, University of Akron, 2011, Chemistry

In Chapter 1 research of hydrogen/air and direct methanol fuel cell membranes especially on the synthesis of new proton conducting membranes is reviewed. Alternative polymer electrolyte membranes such as modified Nafions, polyimides, polyarylene ethers, acid-base polymer blends and polyphosphazenes have been compared to the currently used perfluorinated polymer electrolytes such as Nafions. Because polyphosphazenes are another subject that is involved in the fuel cell research. They are also discussed herein including applications as fuel cell membranes.

Chapter 2 and Chapter 3 focus on the syntheses and characterizations of phosphazene cyclic trimers and linear polymers. The nucleophilic substitution reactions of both phosphazenes with azolylphenol derivatives are discussed. Along with “click” chemistry, a secondary reaction of phosphazene compounds then generates a new route to obtain novel phosphazene compounds. An amino-end compound, such as hexaaminopheoxy-substituted cyclotriphosphazene, is also synthesized by a two-step reaction. Characterization techniques such as nuclear magnetic resonance, mass spectrometry, elemental analysis, infra-red spectrometry and single-crystal X-ray diffraction are applied. The thermal properties of these compounds are examined by thermogravimetric analysis and differential scanning calorimetry.

Chapter 4 and Chapter 5 focus on a membrane preparation and characterization. Chapter 4 is a preliminary study of a triazole-based copolyimide. The preparation and characterization of phosphazene-based proton conducting membranes are discussed in Chapter 5. The conducting membranes are acid-doped composites between a triazole-based copolyimide and the selected phosphazene compound. Basic properties such as water uptake and acid doping levels along with their thermal properties and proton conductivity are discussed.

Committee:

Dr. Wiley Youngs, Dr. (Advisor); Claire Tessier, Dr. (Advisor); Matthew Espe, Dr. (Committee Member); Michael Taschner, Dr. (Committee Member); Robert Weiss, Dr. (Committee Member)

Subjects:

Chemistry

Keywords:

cyclotriphosphazenes; polyphosphazenes; polyimides; fuel cell membranes

Granados-Focil, SergioA new class of polyelectrolytes, poly(phenylene sulfonic acids) and its copolymers as proton exchange membranes for PEMFC’s
Doctor of Philosophy, Case Western Reserve University, 2006, Macromolecular Science
A novel rigid rod liquid crystalline poly(biphenylene disulfonic acid), PBPDSA, was synthesized for the first time using the Ullman coupling reaction. The resulting water soluble, polymer showed a complex aggregation behavior in solution, which complicated the estimation of its molecular weight. The proton conductivity of PBPDSA was higher than that of Nafion over the whole tested range of relative humidities and temperatures. The unparalleled properties of this material were attributed to its liquid crystalline lamellar solid state structure. In order to obtain water insoluble membranes, PBPDSA was modified by grafting bulky or crosslinkable hydrophobic groups. The resulting grafted copolymers showed a solid state structure similar to that of PBPDSA, as well as an analogous anisotropy in some of its properties. The in plane proton conductivity of these materials, measured as a function of relative humidity and temperature, was higher or comparable to that of Nafion. The membranes performance at low relative humidities and high temperatures is remarkable, showing conductivity values up to 2 orders of magnitude larger than those found for Nafion. TGA and FTIR studies indicate that the polymers are stable up to 175°C. The most important discovery was that this class of materials forms almost perfect MeOH vapor barriers. A 20 microns film was more than 1000 times less permeable than Nafion 117. The effect of the bulky and crosslinkable groups on the conductivity, mechanical properties and dimensional stability of the copolymer membranes was evaluated. However, an unequivocal correlation between polymer structure and its properties was complicated by the presence of structural defects generated during the grafting process. Experimental conditions allowing the control but not the elimination of such defects were found and used to prepare grafted copolymers in a controlled and reproducible manner. The initial results of an effort to produce random copolymers using new comonomers amenable to copolymerization using the Ullman reaction are discussed. An extension of this approach, with better structural control and understanding of the membranes’ final solid state structure, will likely produce new membranes whose properties will greatly surpass those of the state of the art materials widely used today.

Committee:

Morton Litt (Advisor)

Keywords:

Fuel cell membranes; PEM; Polyphenylenes; Polyphenylene sulfonic acids; proton exchange membranes; liquid crystalline polymers

Parikh, Harshil R.MODELING AND ANALYSIS OF PHOTON EXCHANGE MEMBRANE FUEL CELL
Master of Science (MS), Ohio University, 2004, Mechanical Engineering (Engineering)

Fuel cell technology is one of the emerging technologies for alternative power supply. Different types of fuel cells are available to serve in various applications. Proton exchange membrane fuel cell (PEMFC), which is the focus of this work, is used widely for portable applications. Present PEMFCs are expensive which impede their commercialization. Better understanding of processes and the optimization of the fuel cell will solve the problem. The focus of this work is to numerically simulate the complex processes that take place within the fuel cell and to develop a typical User Defined Function (UDF). As mathematical model of fuel cell is very complex, it is very difficult to solve the problem analytically. Numerical simulation is the only economical and fast method to understand the processes properly. The work also investigates the effects of change of parameters on the performance of the fuel cell.

Committee:

Bhavin Mehta (Advisor)

Subjects:

Engineering, Mechanical

Keywords:

Modeling; Computer Simulation; Proton Exchange Membrane Fuel Cell

Sinnamon, Ryan R.Analysis of a Fuel Cell Combustor in a Solid Oxide Fuel Cell Hybrid Gas Turbine Power System for Aerospace Application
Master of Science in Engineering (MSEgr), Wright State University, 2014, Mechanical Engineering
Over the last few years, fuel cell technology has significantly advanced and has become a mode of clean power generation for many engineering applications. Currently the dominant application for fuel cell technology is with stationary power generation. Very little has been published for applications on mobile platforms, such as unmanned aerial vehicles. With unmanned aerial vehicles being used more frequently for national defense and reconnaissance, there is a need for a more efficiency, longer endurance power system that can support the increased electrical loads onboard. It has already been proven by others that fuel cell gas turbine hybrid systems can achieve higher system efficiencies at maximum power. The integration of a solid oxide fuel cell combustor with a gas turbine engine has the potential to significantly increase system efficiency at off-design conditions and have a higher energy density compared to traditional heat based systems. This results in abilities to support larger onboard electrical loads and longer mission durations. The majority of unmanned air vehicle mission time is spent during loiter, at part load operation. Increasing part load efficiency significantly increases mission duration and decreases operational costs. These hybrid systems can potentially have lower power degradation at higher altitudes compared to traditional heat based propulsion systems. The purpose of this research was to analyze the performance of a solid oxide fuel cell combustor hybrid gas turbine power system at design and off-design operating conditions at various altitudes. A system level MATLAB/Simulink model has been created to analyze the performance of such a system. The hybrid propulsion system was modeled as an anode-supported solid oxide fuel cell integrated with a commercially-available gas turbine engine used for remote control aircraft. The design point operation of the system was for maximum power at sea-level. A steady-state part load performance analysis was conducted for various loads ranging from 10 = L = 100 percent design load at varying altitudes ranging from 0 = Y = 20,000 feet. This analysis was conducted for four different fuel types: humidified hydrogen, propane, methane, and JP-8 jet fuel. The analysis showed that maximum system efficiency was achieved at loads of 40 = L = 60 percent design load at each altitude and fuel type. The system utilizing methane fuel, internally-steam reformed within the fuel cell, proved to have the highest system efficiency of 46.8 percent (LHV) at a part load of L = 60 percent and an altitude of Y = 20,000 feet.

Committee:

Rory Roberts, Ph.D. (Advisor); Scott Thomas, Ph.D. (Committee Member); Hong Huang, Ph.D. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

SOFC; Fuel Cell; Aerospace; UAV; Hybrid Power System; Unmanned Aircraft;

Shreeram, Devesh DadhichElectrochemical Analysis of Genetically Engineered Bacterial Strains in a Urine-Based Microbial Fuel Cell
MS, University of Cincinnati, 2016, Engineering and Applied Science: Materials Science
Microbial fuel cells (MFCs) use bacterial metabolism to harvest the energy content of organic compounds, producing electrons and protons. In recent years, mutation of bacterial strains to increase the power output has emerged as a priority research focus in the field of MFCs. This thesis investigates wild-type Pseudomonas aeruginosa (PAO1) and two of its mutant strains pilT and pilT-bdlA in Luria broth media (LB) to determine the effect of mutation in the performance of MFCs. In addition the PAO1 and pilT strains are tested in the first urine-based MCF employing genetically engineered bacteria. Polarization and electrochemical impedance spectroscopy (EIS) were implemented to observe the performance of MFC reactors with different bacterial strains and media. The pilT mutant has reduced twitching motility and hyperpiliation, both of which enhance the formation of electrogenic biofilms. The double mutant, pilT-bdlA also has chemotaxis suppression, which should lead to more persistent biofilms because the pilT-bdlA strain does not escape the electrode surface even when the nutrient concentration is low. The increase in biofilm thickness due to pilT-bdlA mutation is also expected to increase the power output. In LB media (Chapter 3), polarization data show that the pilT produces a 4.8-fold power enhancement compared to wild-type PAO1 and a 2.3-fold power enhancement over pilT-bdlA. The pilT-bdlA MFC performance was in between pilT and/ PAO1 (pilT > pilT-bdlA > PAO1). That is, the pilT-bdlA double mutation did not display the expected power enhancement. In urine-based MFCs (Chapter 4), the pilT mutant showed a 2.7-fold increase in peak power density compared to the wild-type strain, PAO1. For both strains, the observed high internal resistance near open circuit voltage was traced to sluggish redox reactions on the anode surface and not to bacterial metabolism. The observed performance of the pilT mutant proved that mutant strains can increase the power output, opening new opportunities for urine-based mini-devices.

Committee:

Dale Schaefer, Ph.D. (Committee Chair); Daniel Hassett, Ph.D. (Committee Member); Jude Iroh, Ph.D. (Committee Member)

Subjects:

Energy

Keywords:

microbial fuel cell;MFC;Mutation;Pseudomonas;Urine;Biofilms

Yen, Shen-AnWater Management in the PEM Fuel Cell by Incorporating a Novel Siloxane Polymer in the Electrode Layer
Master of Science (MS), Ohio University, 2012, Chemical Engineering (Engineering and Technology)
The purpose of this work was to alleviate the water issue present in Nafion┬┐┬┐-based PEM fuel cells operating at low relative humidity conditions by employing a hydrophilic substance COMP-1 in the electrode layer. This modified electrode was hypothesized to prevent the cell from dehydrating by retaining water in the catalyst layer. The improvement would accelerate PEM fuel cell technology to be commercialized in the automotive sector. Through evaluating the important overpotentials dominated by kinetic, ohmic resistance and mass transport limitations, the results show a positive influence of COMP-1 at 50% to 60% RH conditions, but it is not clear that water retention is the cause.

Committee:

Valerie Young, PhD (Advisor); Khairul Alam, PhD (Committee Member); Amina Bose, PhD (Committee Member); Howard Dewald, PhD (Committee Member); Daniel Gulino, PhD (Committee Member)

Subjects:

Alternative Energy; Chemical Engineering; Energy; Engineering

Keywords:

PEM fuel cell; Electrode Engineering; Water Management; Nafion Eledtrolyte; Composite Electrode

Tang, LingMODIFICATION OF SOLID OXIDE FUEL CELL ANODES WITH CERIUM OXIDE COATINGS
Doctor of Philosophy, Case Western Reserve University, 2009, Materials Science and Engineering

A priority for research in solid oxide fuel cells (SOFCs) is to develop cells that can maintain adequate performance in sulfur-containing fuel streams. There has been evidence that cerium oxide in the anode or electrolyte is associated with sulfur tolerance of the cell, but the mechanism underlying this effect is not well understood.

The objective of the present research is to show that the porous cermet SOFC anodes can be coated with cerium oxide films, so that the cell performance can be evaluated as a function of the anode structure and the microstructure of the film. Three types of anodes — Ni/yttria-stabilized zirconia (YSZ), Ni/gadolinia-doped ceria (GDC), and Ni/GDC with GDC interlayer were infiltrated with an aqueous solution to deposit nanocrystalline ceria films. The cells were then tested in hydrogen/nitrogen fuel containing hydrogen sulfide at levels up to 500 ppm. Modification of the anodes with thiol-terminated and trichlorosilane-terminated surfactants was explored. Different ceria film morphology was achieved for each surface treatment. In the cells that underwent performance testing, the thiol treatment promoted ceria film deposition, while the sulfonate treatment suppressed ceria deposition. Uniform ceria films up to 100 nm thick could be deposited in 48 h.

Results on cell testing conditions, e.g. current, time, and H2S exposure were related to different anode structures and ceria coating morphologies. In general, the Ni/GDC anodes showed better performance than the Ni/YSZ anode. The introduction of ceria films often resulted in higher cell current and longer testing time, including operation under H2S exposure. Post-testing characterization revealed that, for some anodes, microstructure changes such as coarsening of Ni in the anode, migration of Ni to the anode surface, and depletion of Ni occurred. These changes in microstructure were irreversible and might account for permanent loss of cell performance. The presence of ceria films delayed these microstructure changes. The more ceria coating, the greater was its inhibitory effect. As a mixed ionic–electronic conductor, ceria can also increase the effective triple-phase boundary region, which in turn may have contributed to the improved cell performance. No specific microstructure change could be attributed exclusively to a sulfur-anode interaction.

Committee:

Mark De Guire, PhD (Committee Chair); Joe Payer, PhD (Committee Member); Frank Ernst, PhD (Committee Member); Wainright Jesse, PhD (Committee Member)

Subjects:

Materials Science

Keywords:

cerium oxide; thin film deposition; solid oxide fuel cell; sulfur tolerance

Zhu, HuanfengExperimental and Theoretical Aspects of Electrode|Electrolyte Interfaces
Doctor of Philosophy, Case Western Reserve University, 2010, Chemistry

In-situ Raman spectra of solution phase electrogenerated species were recorded in a channel flow cell. A microscope objective aligned normal to the direction of flow downstream from the edge of the working electrode was used to focus the excitation laser beam near the metal-electrode|electrolyte interface and also to collect the Raman scattered light from electrogenerated species under maximum detection sensitivity. Linear correlations were found between both the gain and the loss of the integrated Raman intensity attributed to the active redox species, and the current measured at the working electrode as a function of potential.

Light-activated microelectrodes in redox electrolytes were modeled theoretically using COMSOL under strict axisymmetric geometry. Dimensioned and dimensionless steady state profiles for solid state and solution phase species were predicted by solving self-consistently the transport equations and the electrostatic potential within the semiconductor phase subject to the appropriate boundary conditions. The local flux at the interface in the direction normal to the semiconductor surface was calculated as a function of photon flux intensity and bias potential. The predicted limited currents were proportional to the photon flux intensity under high bias potential, the simulation results showed that photo-generated holes in an n-type semiconductor would escape beyond the edge of the illuminated disk, thereby increasing the effective area of the light-activated microelectrode. The effect of the shape on properties of electrocatalytically active nanoparticles supported on inactive planar substrates was modeled theoretically. The results indicated very minor differences between the diffusion limited currents, ilim, for reaction on a hemisphere and full sphere with the same area. However, for prolate spheroids large enhancements were predicted as the aspect ratio was increased. Analyses of the predicted behavior of active microdisks dispersed on both planar and spherical inactive substrates suggested that currents very close to ilim could be achieved for coverage on the order of 1%. This effect might explain experimental observations for the onset potential for the oxygen reduction well ahead of the onset of the reduction of iron porphyrins adsorbed on carbon surfaces associated with the conversion from the inactive to the active form of the macrocycle.

Committee:

Daniel Scherson, A. (Advisor); Robert Dunbar, C. (Committee Chair); Alfred Anderson, B. (Committee Member); Clemens Burda (Committee Member); Kathleen Kash (Committee Member)

Subjects:

Chemical Engineering; Chemistry

Keywords:

Raman; Flow Channel Cell; Semiconductor; Simulation; Microelectrode; Fuel cell; Electrocatalyst; Electrochemistry; Oxygen Reduction

Yu, ZhiqiangTransient Studies of Ni-, Cu-Based Electrocatalysts in CH4 Solid Oxide Fuel Cell
Doctor of Philosophy, University of Akron, 2007, Chemical Engineering

Solid oxide fuel cells (SOFCs) have attracted much research attention because of their capability of oxidizing hydrocarbons directly to produce electricity. A key to successfully designing CH4 SOFC lies in the development of good anode electrocatalysts for CH4 electrochemical oxidation. The transient techniques combined with the current/voltage acquisition and gas monitoring system provides a unique method for studying anode electrochemical oxidation reactions. Ni/YSZ, Cu/Ce0.8Sm0.2O1.9/YSZ, Cu/Ce0.8Mg0.2O1.8/YSZ, and Cu/Ce0.5Zr0.5O2/LSCF anode electrocatalysts were developed in this study for CH4 SOFC.

CH4 pulsing studies over Ni/YSZ anode indicated that (i) the reaction of D2O/CH4 (i.e., reforming of CH4 with D2O) occurs at the sites in the vicinity of the three phase boundary (i.e., the Ni-YSZ interface) where the electrochemical oxidation of HD/D2 takes place; (ii) the production of H2 from the dissociation of CH4 occurred on the Ni surface sites which is far from the three phase boundary. The absence of CO2 formation is due to that Ni/YSZ anode has been shown to exhibit a low activity for the water-gas shift reaction in 750 - 850 °C to produce CO2. The addition of D2O into CH4 improved the SOFC performance with the Ni/YSZ anode. Carbon deposition over Ni/YSZ electrocatalyst exhibits a significant inhibition effect on the electrochemical oxidation reaction over SOFCs with various metal/oxide anodes. CH4 step switch studies over the Cu/Ce0.8Sm0.2O1.9/YSZ anode showed that the electrochemical oxidation of CH4 involves C-H dissociation, hydrogen oxidation, and then carbon oxidation. Lattice oxygen in ceria is more active than oxygen ions (O2-) diffusing from cathode to react with adsorbed carbon to form CO and CO2. The filling up of the oxygen vacancy in ceria by O2- diffusing from cathode could produce current and occurred faster than the electrochemical oxidation reactions. The addition of D2O into CH4 fuel decreased the fuel cell performance, but provided the oxygen source for oxidation of hydrogen and carbon. Result suggested that the electrochemical oxidation of CH4 over the Cu/Ce0.8Mg0.2O1.8 anode catalyst is the limiting step. Coke residing over the Cu/Ce0.5Zr0.5O2/LSCF anode surface can be oxidized to CO and CO2, producing 100 mA/cm2 at 850 °C.

Committee:

Steven Chuang (Advisor)

Subjects:

Engineering, Chemical

Keywords:

CH4; anode; SOFCs; Cu/Ce0.8Mg0.2O1.8/YSZ; D2O/CH4; FUEL CELL

Pitia, Emmanuel SokiriComposite Proton Exchange Membrane Based on Sulfonated Organic Nanoparticles
Doctor of Philosophy, University of Akron, 2012, Polymer Engineering

As the world sets its sight into the future, energy remains a great challenge. Proton exchange membrane (PEM) fuel cell is part of the solution to the energy challenge because of its high efficiency and diverse application. The purpose of the PEM is to provide a path for proton transport and to prevent direct mixing of hydrogen and oxygen at the anode and the cathode, respectively. Hence, PEMs must have good proton conductivity, excellent chemical stability, and mechanical durability. The current state-of-the-art PEM is a perfluorosulfonate ionomer, Nafion. Although Nafion has many desirable properties, it has high methanol crossover and it is expensive.

The objective of this research was to develop a cost effective two-phase, composite PEM wherein a dispersed conductive organic phase preferentially aligned in the transport direction controls proton transport, and a continuous hydrophobic phase provides mechanical durability to the PEM. The hypothesis that was driving this research was that one might expect better dispersion, higher surface to volume ratio and improved proton conductivity of a composite membrane if the dispersed particles were nanometer in size and had high ion exchange capacity (IEC, = [mmol sulfonic acid]/gram of polymer). In view of this, considerable efforts were employed in the synthesis of high IEC organic nanoparticles and fabrication of a composite membrane with controlled microstructure.

High IEC, ~ 4.5 meq/g (in acid form, theoretical limit is 5.4 meq/g) nanoparticles were achieved by emulsion copolymerization of a quaternary alkyl ammonium (QAA) neutralized-sulfonated styrene (QAA-SS), styrene, and divinylbenzene (DVB). The effects of varying the counterion of the sulfonated styrene (SS) monomer (alkali metal and QAA cations), SS concentration, and the addition of a crosslinking agent (DVB) on the ability to stabilize the nanoparticles to higher IECs were assessed. The nanoparticles were ion exchanged to acid form. The extent of ion exchange was characterized with solid state 13C NMR spectroscopy, FTIR spectroscopy, TGA, elemental analysis, and titration. The results indicate the extent of ion exchange was ~ 70-80%. Due to the mass of QAA, the remaining QAA reduced the IEC of the nanoparticles to < 2.2 meq/g.

In fabricating the composite membranes, the nanoparticles and polystyrene were solution cast in a continuous process with and without electric field. The electric field had no effect on the water uptake. Based on the morphology and the proton conductivity, it appears orientation of the nanoparticles did not occur. We hypothesize the lack of orientation was caused by swelling of the particles with the solvent. The solvent inside the particle minimized polarizability, and thus prevented orientation. The composite membranes were limited to low proton conductivity of ~ 10-5 S/cm due to low IEC of the nanoparticles, but good dispersion of the nanoparticles was achieved. Future work should look into eliminating the QAA during synthesis and developing a rigid core for the nanoparticles.

Committee:

Robert A. Weiss, Dr. (Advisor); Mukerrem Cakmak, Dr. (Committee Member); Kevin Cavicchi, Dr. (Committee Member); Coleen Pugh, Dr. (Committee Member); Wiley J. Youngs, Dr. (Committee Member)

Subjects:

Chemical Engineering; Engineering; Polymer Chemistry; Polymers

Keywords:

fuel cell; PEM; proton exchange membrane; nanoparticles, quaternary alkyl ammonium, sulfonated styrene, emulsion, electric field alignment, ion exchange resin

Korfhagen, ScottStabilization of Scaffold-Supported, Photopolymerized Bilayer Lipid Membranes with Gramicidin-D for Novel Fuel Cells
MS, University of Cincinnati, 2008, Engineering : Materials Science

Bilayer lipid membranes are a necessary component of all life and have been examined for use in novel applications such as biosensors and polymer electrolyte membrane fuel cells. The goal of this study was to produce stabilized phospholipid bilayer membranes with gramicidin channels within the pores of porous polycarbonate “scaffolds” in order to improve the functional lifetime of the membranes. 1-Palmitoyl-2-10,12 Tricosadiynoyl-sn-Glycero-3-Phosphocholine (PTPC) and 1-Palmitoyl-2-10,12 Tricosadiynoyl-sn-Glycero-3-Phosphoethanolamine (PTPE) were utilized to develop polymerized phospholipid bilayers. The bilayer lipid membranes were formed by depositing a solution of lipids in decane onto a porous polycarbonate filter. An aqueous medium was then deposited on each side of the polycarbonate filter so that self-assembly of the bilayer lipid membrane could occur. The membranes were photopolymerized using short-wavelength ultraviolet radiation (λ = 254 nm).

The resulting membranes were chemically analyzed using UV-Visual Spectroscopy and Raman Spectroscopy. The stability of membranes with and without gramicidin channels at elevated temperatures (60 - 80 °C) was analyzed by measuring the resistance or current across the phospholipid bilayer / polycarbonate membrane system. Resistance values in the giga-ohm range were found for phospholipid bilayer membranes without gramicidin in the presence of potassium, calcium or N-methyl-D-glucamine ions at 60 °C. When gramicidin channels were incorporated into the phospholipid bilayer membranes, the resistance values dropped to the order of mega-ohms. Additionally, these membranes were used to make novel proton exchange membrane fuel cells (PEM fuel cells). This study showed that gramicidin could be inserted into photopolymerized phospholipid bilayers and remained functional at 60 °C. It also showed that it might be possible to produce novel PEM fuel cells using these polymerized phospholipid bilayer membranes as proton exchange membranes.

Committee:

F. James Boerio, PhD (Committee Chair); Jude Iroh, PhD (Committee Member); Gregory Beaucage, PhD (Committee Member)

Subjects:

Engineering

Keywords:

phospholipid bilayer; PEM fuel cell; gramicidin; supported lipid membrane; photopolymerization; diacetylene

Kalapos, Thomas LawrenceInteraction of Water with the Proton Exchange Fuel Cell Membrane
Doctor of Philosophy, Case Western Reserve University, 2007, Chemical Engineering
For most polymer electrolyte membrane (PEM) fuel cells, water facilitates the proton transport that is a key process in the fuel cell’s operation. Therefore, understanding how water interacts with the membrane can guide material improvements for better fuel cell performance. Presently, optimal PEM fuel cell conditions are at approximately 80°C and 100% relative humidity. It is desired, however, to operate at temperatures above 120°C and consequently lower relative humidity (as low as 25%). Such operating conditions present a number of advantages, including a higher tolerance for CO poisoning of the commonly Pt catalyst, greater heat rejection (smaller radiator requirements) and higher rates of activation for the respective electrochemical half cell reactions. However, at conditions above 80°C and below 100% relative humidity (without pressurization of the system), fuel cell performance suffers greatly primarily due to the dehydration of the membrane. The question arises, then, how can a sufficient amount of water critical for proton transport be retained in the fuel cell without pressurization of the system? More fundamentally, what is the nature of proton transport in the membrane and the role of water or a similar “proton transport facilitator”? Additionally, what chemical and structural properties of the membrane are beneficial for operation at the desired conditions? To answer these questions, this work studied the thermodynamics of hydration of hydrophilic ionic acid groups for different membranes and model systems. Membranes were equilibrated at different activities of water corresponding to different levels of membrane humidity. Isopiestic data was collected from the equilibrated membranes. Differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) were employed to couple the heat release or gain and weight loss, both with respect to temperature, in order to arrive at an average change in enthalpy. Such enthalpic information gives insight to the condition of water in the membrane, either free (absorbed) or bound (chemically attached) and thereby can assist in the tailoring of materials that will retain water at temperatures above 100°C. Conductivity was measured by two-point electrical impedance spectroscopy (EIS) to investigate proton conduction. Diffusion and relaxation was measured by nuclear magnetic resonance spectroscopy (NMR) for insights into water transport in the membrane materials.

Committee:

Thomas Zawodzinski (Advisor)

Keywords:

Proton Exchange Membrane; Fuel Cell; Hydration; Diffusion; Nuclear Magnetic Resonance; water; interaction; intramolecular; intermolecular

Trembly, JasonThe Effect of Coal Syn Gas Containing Hydrogen Sulfide on the Operation of a Planar Solid Oxide Fuel Cell
Master of Science (MS), Ohio University, 2005, Chemical Engineering (Engineering)

Planar solid oxide fuel cell (PSOFC) research at Ohio University has shown that the PSOFC may be used to produce electrical energy using gasified Ohio coal. Electrolyte supported PSOFCs with an anode containing nickel, yttria stabilized zirconium, and cerium oxide were operated for over 500 hours. PSOFCs were tested by supplying the fuel cell with a simulated coal syn gas and assessing the performance of the fuel cell by operating it under a load of 14 Amps and measuring the fuel cell’s potential and area specific resistance (ASR). PSOFCs used in the research were found to have a potential of 0.74±0.01 Volts under a load of 0.21±0.01 Amps/cm 2 and an ASR increase of 0.10±0.16 percent per 100 hours of operation with out H 2 S and have a potential of 0.66±0.01 Volts under a load of 0.21±0.01 Amps/cm 2 and an ASR increase of 5.4±2.8 percent per 100 hours of operation with 249±9 ppm H 2 S.

Committee:

David Bayless (Advisor)

Subjects:

Engineering, Chemical

Keywords:

Planar Solid Oxide Fuel Cell; Coal Syn Gas; Hydrogen Sulfide; Sulfer Tolerance; Ni/CeO 2 Anode

Cooper, Matthew E.Energy Production from Coal Syngas Containing H2S via Solid Oxide Fuel Cells Utilizing Lanthanum Strontium Vanadate Anodes
Doctor of Philosophy (PhD), Ohio University, 2008, Chemical Engineering (Engineering and Technology)

Lanthanum strontium vanadate (LSV), a perovskite ceramic electrocatalyst suitable for use as a solid oxide fuel cell (SOFC) anode, has shown significant activity toward the selective oxidation of H2S from a fuel stream. With this in mind, the feasibility of a two-stage SOFC reaction process using LSV-based SOFCs as an alternative to H2S sorbents was investigated. A procedure for producing a bilayer LSV anode via an inexpensive screen-printing method was optimized and planar SOFCs utilizing these bilayer LSV anodes were tested under H2, syngas and syngas with H2S environments. Considering LSV/yttria stabilized zirconia (YSZ) bilayer anodes, it was found that the optimum anode thickness of 65 μm at 800°C yields a maximum power density of 5.85 mW/cm2, while at 900°C the optimized anode thickness of 80 μm realizes a maximum power density of 17.96 mW/cm2. Substitution of gadolinium-doped ceria (GDC) for YSZ in the bilayer LSV anode was shown to improve catalytic performance; peak power densities for optimized LSV/GDC-based SOFCs at 800 and 900°C were 16.60 and 34.86 mW/cm2, respectively.

It was demonstrated that all tested LSV-based SOFCs showed little to no performance degradation due to catalytic poisoning when utilizing syngas containing H2S as fuel, corroborating previous results. It was also shown that LSV had poor activity toward CO oxidation either directly or as a water-gas shift catalyst over the tested temperature range. A feasibility study of the aforementioned two-stage SOFC reaction process showed that SO2 found in the exhaust from the LSV-based SOFC caused performance degradation to a Ni-based SOFC, though not to the extent caused by an equal amount of H2S; this finding suggests that SOFCs utilizing LSV/YSZ anodes may indeed offer promise as a method for warm-gas remediation of H2S contained in hydrocarbon fuel streams.

Committee:

David J. Bayless, PhD (Advisor); Michael Prudich, PhD (Committee Member); Howard Dewald, PhD (Committee Member); Daniel Gulino, PhD (Committee Member); Jeffrey Rack, PhD (Committee Member)

Subjects:

Chemical Engineering

Keywords:

lanthanum strontium vanadate (LSV); solid oxide fuel cell (SOFC); coal syngas; H2S; SO2; electrochemical AC impedance spectroscopy (EIS); mathematical modeling

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