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1
Stephens, Brian Dominic. "BIOCOMPOSITE PROTON EXCHANGE MEMBRANES*." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1147968573.
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Shi, Jinjun. "Composite Membranes for Proton Exchange Membrane Fuel Cells." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1214964058.
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Ion, Mihaela Florentina. "Proton transport in proton exchange membrane fuel cells /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3164514.
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Choi, Jonghyun. "Nanofiber Network Composite Membranes for Proton Exchange Membrane Fuel Cells." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1260461818.
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Ergun, Dilek. "High Temperature Proton Exchange Membrane Fuel Cells." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610803/index.pdf.
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It is desirable to increase the operation temperature of proton exchange membrane fuel cells above 100oC due to fast electrode kinetics, high tolerance to fuel impurities and simple thermal and water management.
In this studythe objective is to develop a high temperature proton exchange membrane fuel cell. Phosphoric acid doped polybenzimidazole membrane was chosen as the electrolyte material. Polybenzimidazole was synthesized with different molecular weights (18700-118500) by changing the synthesis conditions such as reaction time (18-24h) and temperature (185-200oC). The formation of polybenzimidazole was confirmed by FTIR, H-NMR and elemental analysis. The synthesized polymers were used to prepare homogeneous membranes which have good mechanical strength and high thermal stability. Phosphoric acid doped membranes were used to prepare membrane electrode assemblies. Dry hydrogen and oxygen gases were fed to the anode and cathode sides of the cell respectively, at a flow rate of 0.1 slpm for fuel cell tests. It was achieved to operate the single cell up to 160oC. The observed maximum power output was increased considerably from 0.015 W/cm2 to 0.061 W/cm2 at 150oC when the binder of the catalyst was changed from polybenzimidazole to polybenzimidazole and polyvinylidene fluoride mixture. The power outputs of 0.032 W/cm2 and 0.063 W/cm2 were obtained when the fuel cell operating temperatures changed as 125oC and 160oC respectively. The single cell test presents 0.035 W/cm2 and 0.070 W/cm2 with membrane thicknesses of 100 µ
m and 70 µ
m respectively. So it can be concluded that thinner membranes give better performances at higher temperatures.
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Xiao, Zhiyong. "Monolithic integration of proton exchange membrane microfuel cells /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20XIAO.
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Oyarce, Alejandro. "Electrode degradation in proton exchange membrane fuel cells." Doctoral thesis, KTH, Tillämpad elektrokemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-133437.
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The topic of this thesis is the degradation of fuel cell electrodes in proton exchange membrane fuel cells (PEMFCs). In particular, the degradation associated with localized fuel starvation, which is often encountered during start-ups and shut-downs (SUs/SDs) of PEMFCs. At SU/SD, O2 and H2 usually coexist in the anode compartment. This situation forces the opposite electrode, i.e. the cathode, to very high potentials, resulting in the corrosion of the carbon supporting the catalyst, referred to as carbon corrosion. The aim of this thesis has been to develop methods, materials and strategies to address the issues associated to carbon corrosion in PEMFC.The extent of catalyst degradation is commonly evaluated determining the electrochemically active surface area (ECSA) of fuel cell electrode. Therefore, it was considered important to study the effect of RH, temperature and type of accelerated degradation test (ADT) on the ECSA. Low RH decreases the ECSA of the electrode, attributed to re-structuring the ionomer and loss of contact with the catalyst.In the search for more durable supports, we evaluated different accelerated degradation tests (ADTs) for carbon corrosion. Potentiostatic holds at 1.2 V vs. RHE were found to be too mild. Potentiostatic holds at 1.4 V vs. RHE were found to induce a large degree of reversibility, also attributed to ionomer re-structuring. Triangle-wave potential cycling was found to irreversibly degrade the electrode within a reasonable amount of time, closely simulating SU/SD conditions.Corrosion of carbon-based supports not only degrades the catalyst by lowering the ECSA, but also has a profound effect on the electrode morphology. Decreased electrode porosity, increased agglomerate size and ionomer enrichment all contribute to the degradation of the mass-transport properties of the cathode. Graphitized carbon fibers were found to be 5 times more corrosion resistant than conventional carbons, primarily attributed to their lower surface area. Furthermore, fibers were found to better maintain the integrity of the electrode morphology, generally showing less degradation of the mass-transport losses. Different system strategies for shut-down were evaluated. Not doing anything to the fuel cell during shut-downs is detrimental for the fuel cell. O2 consumption with a load and H2 purge of the cathode were found to give around 100 times lower degradation rates compared to not doing anything and almost 10 times lower degradation rate than a simple air purge of the anode. Finally, in-situ measurements of contact resistance showed that the contact resistance between GDL and BPP is highly dynamic and changes with operating conditions.Denna doktorsavhandling behandlar degraderingen av polymerelektrolytbränslecellselektroder. polymerelektrolytbränslecellselektroder. Den handlar särskilt om nedbrytningen av elektroden kopplad till en degraderingsmekanism som heter ”localized fuel starvation” oftast närvarande vid uppstart och nedstängning av bränslecellen. Vid start och stopp kan syrgas och vätgas förekomma samtidigt i anoden. Detta leder till väldigt höga elektrodpotentialer i katoden. Resultatet av detta är att kolbaserade katalysatorbärare korroderar och att bränslecellens livslängd förkortas. Målet med avhandlingen har varit att utveckla metoder, material och strategier för att både öka förståelsen av denna degraderingsmekanism och för att maximera katalysatorbärarens livslängd.Ett vanligt tillvägagångsätt för att bestämma graden av katalysatorns degradering är genom mätning av den elektrokemiskt aktiva ytan hos bränslecellselektroderna. I denna avhandling har dessutom effekten av temperatur och relativ fukthalt studerats. Låga fukthalter minskar den aktiva ytan hos elektroden, vilket sannolikt orsakas av en omstrukturering av jonomeren och av kontaktförlust mellan jonomer och katalysator.Olika accelererade degraderingstester för kolkorrosion har använts. Potentiostatiska tester vid 1.2 V mot RHE visade sig vara för milda. Potentiostatiska tester vid 1.4 V mot RHE visade sig däremot medföra en hög grad av reversibilitet, som också den tros vara orsakad av en omstrukturering av jonomeren. Cykling av elektrodpotentialen degraderade istället elektroden irreversibelt, inom rimlig tid och kunde väldigt nära simulera förhållandena vid uppstart och nedstängning.Korrosionen av katalysatorbäraren medför degradering av katalysatorn och har också en stor inverkan på elektrodens morfologi. En minskad elektrodporositet, en ökad agglomeratstorlek och en anrikning av jonomeren gör att elektrodens masstransportegenskaper försämras. Grafitiska kolfibrer visade sig vara mer resistenta mot kolkorrosion än konventionella kol, främst p.g.a. deras låga ytarea. Grafitiska kolfibrer visade också en förmåga att bättre bibehålla elektrodens morfologi efter accelererade tester, vilket resulterade i lägre masstransportförluster.Olika systemstrategier för nedstängning jämfördes. Att inte göra något under nedstängning är mycket skadligt för bränslecellen. Förbrukning av syre med en last och spolning av katoden med vätgas visade 100 gånger lägre degraderingshastighet av bränslecellsprestanda jämfört med att inte göra något alls och 10 gånger lägre degraderingshastighet jämfört med spolning av anoden med luft. In-situ kontaktresistansmätningar visade att kontaktresistansen mellan bipolära plattor och GDL är dynamisk och kan ändras beroende på driftförhållandena.
QC 20131104
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DeLashmutt, Timothy E. "Modeling a proton exchange membrane fuel cell stack." Ohio : Ohio University, 2008. http://www.ohiolink.edu/etd/view.cgi?ohiou1227224687.
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Yurdakul, Ahmet Ozgur. "Acid Doped Polybenzimidazole Membranes For High Temperature Proton Exchange Membrane Fuel Cells." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608506/index.pdf.
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Acid Doped Polybenzimidazole Membranes for High Temperature
Proton Exchange Membrane Fuel Cells
Author: Ahmet Özgü
r Yurdakul One of the most popular candidates for high temperature PEMFC&rsquo
s is phosphoric acid doped polybenzimidazole (PBI) membrane due to its thermal and mechanical stability. In this study, high molecular weight PBI was synthesized by using PPA polymerization. The stirring rate of reaction solution was optimized to obtain high molecular weight. The inherent viscosity of polymer was measured at four points in 96 percent sulphuric acid solution at 30 degree centigrade by using an Ubbelohde viscometer. The highest average molecular weight was found as approximately 120,000 using the Mark-Houwink equation. The polymer was dissolved in N,N-dimethylacetamide at 70 degree centigrade with an ultrasonic stirrer. The membranes cast from this solution were doped with phosphoric acid solutions at different concentrations. The doping levels of the membranes were 6, 8, 10 and 11 moles phosphoric acid/PBI repeat unit. The mechanical strength of the acid doped membranes measured by tensile tests were found as 23, 16, 12 and 11 MPa, respectively. Conductivity measurements were made using the four probe technique. The membranes were placed in a conductivity cell and measurements were taken in humidity chamber with temperature and pressure control. The conductivity of membranes was measured at 110, 130 and 150 degree centigrade in both dry air and water vapor. The highest conductivity was 0.12 S/cm at 150 degree centigrade and 33 percent relative humidity for the membrane doped with 11 moles of H3PO4. The measurements showed that conductivity increased with increasing doping and humidity. Moreover, membranes had acceptable conductivity levels in dry air.
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Hill, Melinda Lou. "Polymeric and Polymer/Inorganic Composite Membranes for Proton Exchange Membrane Fuel Cells." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/37597.
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Several types of novel proton exchange membranes which could be used for both direct methanol fuel cells (DMFCs) and hydrogen/air fuel cells were investigated in this work. One of the main challenges for DMFC membranes is high methanol crossover. Nafion, the current perfluorosulfonic acid copolymer benchmark membrane for both DMFCs and hydrogen/air fuel cells, shows very high methanol crossover. Directly copolymerized disulfonated poly(arylene ether sulfone)s copolymers doped with zirconium phosphates and phenyl phosphonates were synthesized and showed a significant reduction in methanol permeability. These copolymer/inorganic nanocomposite hybrid membranes show lower water uptake and conductivity than Nafion and neat poly(arylene ether sulfone)s copolymers, but in some cases have similar or even slightly improved DMFC performance due to the lower methanol permeability. These membranes also show advantages for high temperature applications because of the reinforcing effect of the filler, which helps to maintain the modulus of the membrane, allowing the membrane to maintain proton conductivity even above the hydrated glass transition temperature (Tg) of the copolymer. Sulfonated zirconium phenyl phosphonate additives were also synthesized, and membranes incorporating these materials and disulfonated poly(arylene ether sulfone)s showed promising proton conductivity over a wide range of relative humidities. Single-Tg polymer blend membranes were studied, which incorporated disulfonated poly(arylene ether sulfone) with varied amounts of polybenzimidazole. The polybenzimidazole served to decrease the water uptake and methanol permeability of the membranes, resulting in promising DMFC and hydrogen/air fuel cell performance.Ph. D.
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Marani, Debora. "Development of hybrid proton-conducting polymers for proton exchange membrane fuel cells." Aix-Marseille 1, 2006. http://www.theses.fr/2006AIX11002.
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Le développement d'électrolytes polymères de nouvelle génération est un pré requis essentiel pour la commercialisation à grande échelle des piles à combustibles à membrane polymérique. Ces conducteurs protoniques doivent présenter une bonne stabilité morphologique, hydrolytique, mécanique et une conductivité appropriée à une température supérieure à 100°C à basse humidité relative. Dans ce travail, diverses stratégies sont explorées pour la synthèse de polymères conducteurs hybrides organiques-inorganiques nanocomposites à partir de polymères thermoplastiques aromatiques. L'emploi de matériaux hybrides permet d'exploiter l'effet synergique dû à la présence simultanée d'une composante organique polymérique et d'une partie inorganique à base de silicium. Ces effets synergétiques s'expliquent par la possibilité de moduler et de contrôler la séparation entre les parties hydrophile et hydrophobe, dont dépendent fortement les propriétés de l'électrolyte polymère. Des matériaux hybrides de classe I à base de poly-éther-éther-kétone (PEEK) ont été synthétisés ainsi que plusieurs exemples de matériaux hybrides de classe II à base de PEEK et de poly-phényl-sulfone (PPSU) sulfonatés (SPEEK et SPPSU) et contenant comme partie inorganique des atomes de silicium diversement fonctionnalisés. La caractérisation des matériaux comporte l'analyse structurale, l'étude des propriétés physicochimiques et le comportement électrochimique. Des résultats très positifs ont été obtenus principalement avec deux des systèmes étudiés : un mélange de polymères à base de SPEEK et SPPSU silicié et un polymère interconnecté à base de PEEK sulfonaté et silicié (SOSiPEEK)
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MARANI, DEBORA. "Development of hybrid proton-conducting polymers for proton exchange membrane fuel cells." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2006. http://hdl.handle.net/2108/202679.
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Lo sviluppo di elettroliti polimerici di nuova generazione è un requisito essenziale per la diffusione su grande scala delle celle a combustibile a membrana polimerica. Tali conduttori protonici devono esibire stabilità morfologica, idrolitica, meccanica ed adeguate proprietà di conducibilità (σ~ 0.01 Scm-1) a temperature superiori a 100 °C per bassi valori d’umidità relativa. Nel presente lavoro sono esplorate diverse strategie per la sintesi di polimeri conduttori ibridi organici-inorganici nanocompositi a partire da polimeri termoplastici aromatici. L'impiego di materiali ibridi permette di sfruttare l'effetto sinergico dovuto alla contemporanea presenza di una componente organica, nel caso specifico polimerica, e di una inorganica, nel caso specifico a base di silicio. Tale effetto sinergico si esplica nella possibilità di modulare e controllare la separazione tra la fase idrolifila ed idrofobica da cui fortemente dipendono le prestazioni dell'elettrolita polimerico. Membrane ibride di classe I a base di polietereterchetone solfonato (S-PEEK) sono così state sintetizzate insieme a numerosi esempi di membrane ibride di classe II a base di S-PEEK e polifenilsolfone solfonato (S-PPSU), contenenti come porzione inorganica atomi di silicio diversamente funzionalizzati. La caratterizzazione dei materiali ha riguardato l’analisi della struttura, le proprietà chimico fisiche ed il comportamento elettrochimico. Risultati molto positivi sono stati ottenuti principalmente con due dei sistemi investigati: una miscela polimerica a base di S-PEEK e S-PPSU sililato ed un polimero interconnesso tramite ponti -SO2- (SOPEEK) e sililato (SOSiPEEK).The development of new generation polymer electrolytes is an essential prerequisite for grand scale commercialisation on of polymer electrolyte membrane fuel cells. These proton conductors must show good morphological, hydrolytic and mechanical stability and an appropriate conductivity (σ ~ 0.01 Scm-1) at a temperature above 100°C at low relative humidity. In this work, diverse strategies for synthesis of hybrid organic-inorganic proton conducting polymer nanocomposites were explored, based on aromatic thermoplastic polymers. The use of hybrid materials permits exploitation of the synergy between the simultaneously present organic polymeric component and an inorganic silicon-based part. These effects can be explained by the possibility to modulate and to control the separation between hydrophilic and hydrophobic parts, which strongly modify the properties of the electrolytic polymer. Hybrid materials of class I based on sulfonated poly-ether-ether-ketone (S-PEEK) were synthesized as well as several examples of hybrid materials of class II based on SPEEK and poly-phenyl-sulfone sulfonated (S-PPSU) and containing as inorganic part diverse functionalized silicon atoms. These materials were characterized from the point of view of structure, physical and chemical properties and electrochemical behaviour. Very positive results were obtained mainly for two investigated systems: a mixture of S-PEEK and S-PPSU silylated polymer and a cross-linked polymer, through -SO2- bridges (SOPEEK) and silylated (SOSiPEEK).
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He, Chen Feng. "Surface behavior of sulfonated hydrocarbon proton exchange membranes." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/31224.
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La pile à combustible a suscité une attention croissante en tant que solution de rechange écologique aux carburants fossiles. Les membranes échangeuses d’ions (PEM)s sont utilisées dans des piles à combustible à membrane échangeuse de protons (PEMFC) et des piles à combustible directes au méthanol (DMFC) comme composant séparateur pour fournir une barrière au transfert de carburant entre les électrodes et pour transférer des protons de l'anode à La cathode. Les PEMFC et les DMFC suscitent des intérêts plus particuliers pour l'utilisation dans les applications automobiles, stationnaires et électroniques portables. En tant que composante clé d’une PEMFC, une PEM est nécessaire pour effectuer des fonctions multiples telles que la séparation de gaz, l'isolation électrique et le transfert ionique pour transporter des protons de l'anode à la cathode. La présence d'eau dans une PEM est essentielle pour que les polymères traditionnels sulfonés transfèrent les protons et facilitent la conductivité protonique. Comme le Nafion, la conduction protonique des polymères de type PEM sulfonés dépend de le teneur en eau dans les membranes. Cependant, une absorption excessive d'eau dans une PEM conduit à un changement dimensionnel inacceptable, à une mésadaptation dimensionnelle avec les électrodes, à une délamination des couches de catalyseur de la PEM et à une perte des propriétés mécaniques, ce qui pourrait conduire à une mauvaise performance ou un manque de durabilité de l'assemblage membrane – électrode (MEA). En tant que systèmes hautement intégrés, les piles à combustible sont faites de matériaux hétérogènes comportant contenant du gaz, du liquide et du solide. Les MEA sont typiquement fabriqués par collage d'électrodes de catalyseur de platine supporté sur du carbone sur l'électrolyte PEM, en utilisant un ionomère de type Nafion liant du catalyseur, quel que soit la PEM utilisée. La structure et l'activité des différentes interfaces, l'adhérence et la compatibilité entre les différentes couches ainsi que les caractéristigues du carburant jouent des rôles clés sur la performance globale de la pile à combustible. Parmi ces questions diverses, le transfert inévitable de méthanol dans une PEM, telle que le Nafion, limite les applications en DEMFC. Malgré le développement de nombreuses PEM à base d'hydrocarbures en tant que substituts au Nafion, le comportement de surface et l'adaptation / compatibilité interfaciale entre ce type de PEM et les autres couches est moins bien compris. Dans cette thèse, nous...The fuel cell has received attention as a promising eco-friendly alternative energy source to fossil fuels. Polymer exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) have attracted increasing interest for use in motor vehicles and electronic applications including stationary and portable devices. As a key component of PEMFC and DMFC, PEM is required to perform multiple functions such as fuel separator, electrical insulator and ionic path to transport protons from the anode to the cathode. The presence of water in PEM is essential for traditional, sulfonated polymers to transfer protons and to facilitate proton conductivity. As Nafion, the proton conduction of the sulfonated PEM-type polymers depends upon the water content in the membranes. However, excessive water uptake in a PEM results in unacceptable dimensional change, dimensional mismatch with the electrodes, delaminating of catalyst layers from the PEM and loss of mechanical properties, which could result in poor membrane electrode assembly (MEA) performance or durability. As a highly integrated system, fuel cells are used in a heterogeneous environment containing gas, liquid, and solid. Typically, MEAs are constructed by bonding carbonsupported platinum catalyst electrodes onto the PEM electrolyte. Regardless of the PEM used, a Nafion-type ionomer is usually employed as a catalyst support. The structure and activity at the different interfaces, the adhesion and compatibility among various layers, as well as fuel property on PEM play key roles on the fuel cell universal performance as vital as the individual components. Among these heterogeneous concerns, crossover of methanol in PEM, such as Nafion, limits DEMFC applications. In spite of the development of numerous hydrocarbon PEMs as substitutes to Nafion, the surface behavior and interfacial match between a PEM and the other layers, such as, the interface between a PEM and gas diffusion layer/catalyst layer/methanol layer are less understood. In this thesis, the surface/interface behavior of a representative selection of hydrocarbon-based proton exchange membranes (PEMs) was investigated. These PEMs are: copolymerized sulfonated poly(ether ether ketone) (SPEEK-HQ), sulfophenylated poly(aryl ether ether ketone) (Ph-SPEEK), sulfophenylated poly(aryl ether ether ketone ketone) (Ph-m-SPEEKK), and sulfonated poly (aryl ether ether nitrile) (SPAEEN-B).
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Richardson, Peter. "Oxygen evolution electrocatalysts for proton exchange membrane water electrolysis." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/374786/.
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Proton exchange membrane (PEM) water electrolysers are forecast to become an important intermediary energy storage technology between renewable power sources and energy distribution/usage. This is because they offer a production route to high purity H2 that is both non-polluting and efficient. Energy stored as H2 can be converted back to electricity for use in the national grid, pumped into existing natural gas networks or used as a fuel for hydrogen-powered vehicles. The majority of the energy losses in a PEM water electrolyser are associated with the high overpotential that is required for the electrochemical evolution of O2 that occurs at the anode. The highly oxidising conditions of this reaction coupled to the low pH of the PEM environment restrict electrocatalyst selection to expensive noble metal oxides. Thus to enhance the commercial viability of PEM electrolysers, the goal of electrocatalyst development for the O2 evolution reaction is to (i) increase the catalytic performance, (ii) increase the catalyst stability and (iii) reduce the cost of the catalyst components. In this work a range of iridium-based electrocatalysts with reduced Ir contents have been prepared. Two methods are employed to reduce the Ir content: (i) mixing the Ir with ruthenium to form a binary metal oxide and (ii) dispersing the active Ir phase on an indium tin oxide (ITO) support. Investigation of the electrocatalysts via a combination of different physical and electrochemical characterisation techniques, including a novel in-situ X-ray absorbance experiment, indicates that both approaches produce electrocatalysts with comparable or improved O2 evolution activity compared to the state-of-the-art iridium oxide (IrO2) material. However selection of the most appropriate catalyst for PEM electrolysis may ultimately be a compromise between activity, stability and cost.
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Einsla, Brian Russel. "High Temperature Polymers for Proton Exchange Membrane Fuel Cells." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/27320.
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Novel proton exchange membranes (PEMs) were investigated that show potential for operating at higher temperatures in both direct methanol (DMFC) and H2/air PEM fuel cells. The need for thermally stable polymers immediately suggests the possibility of heterocyclic polymers bearing appropriate ion conducting sites. Accordingly, monomers and random disulfonated poly(arylene ether) copolymers containing either naphthalimide, benzoxazole or benzimidazole moieties were synthesized via direct copolymerization. The ion exchange capacity (IEC) was varied by simply changing the ratio of disulfonated monomer to nonsulfonated monomer in the copolymerization step. Water uptake and proton conductivity of cast membranes increased with IEC. The water uptake of these heterocyclic copolymers was lower than that of comparable disulfonated poly(arylene ether) systems, which is a desirable improvement for PEMs. Membrane electrode assemblies were prepared and the initial fuel cell performance of the disulfonated polyimide and polybenzoxazole (PBO) copolymers was very promising at 80 C compared to the state-of-the-art PEM (Nafion®); nevertheless these membranes became brittle under operating conditions. Several series of poly(arylene ether)s based on disodium-3,3â -disulfonate-4,4â -dichlorodiphenylsulfone (S-DCDPS) and a benzimidazole-containing bisphenol were synthesized and afforded copolymers with enhanced stability. Selected properties of these membranes were compared to separately prepared miscible blends of disulfonated poly(arylene ether sulfone) copolymers and polybenzimidazole (PBI). Complexation of the sulfonic acid groups with the PBI structure reduced water swelling and proton conductivity.
The enhanced proton conductivity of Nafion® membranes has been proposed to be due to the aggregation of the highly acidic side-chain sulfonic acid sites to form ion channels. A series of side-chain sulfonated poly(arylene ether sulfone) copolymers based on methoxyhydroquinone was synthesized in order to investigate this possible advantage and to couple this with the excellent hydrolytic stability of poly(arylene ether)s. The methoxy groups were deprotected to afford reactive phenolic sites and nucleophilic substitution reactions with functional aryl sulfonates were used to prepare simple aryl or highly acidic fluorinated sulfonated copolymers. The proton conductivity and water sorption of the resulting copolymers increased with the ion exchange capacity, but changing the acidity of the sulfonic acid had no apparent effect.Ph. D.
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Pitia, Emmanuel Sokiri. "Composite Proton Exchange Membrane Based on Sulfonated Organic Nanoparticles." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1339277956.
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Parikh, Harshil R. "Modeling and analysis of proton exchange membrane fuel cell." Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1088438486.
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Alhazmi, Nahla Eid. "Thermal conductivity of proton exchange membrane fuel cell components." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/6818/.
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Proton exchange membrane (PEM) fuel cell has the potential to be one of the main energy sources in the future. However, the leading issues when operating the fuel cells are the water and the thermal managements. In this thesis, numerical studies have been developed in order to investigate the sensitivity of the PEM fuel cells performance to the thermal conductivities of the main components in PEM fuel cells, which are the membrane, the gas diffusion layer (GDL) and the catalyst layer. In addition, the effect of the thermal conductivity of these components and the metallic GDL on the temperature distribution and the water saturation was considered conducive to the improvement of the heat and water management in PEM fuel cells. On the other hand, the experimental work was completed to determine the effects of the thermal conductivity and the thermal contact resistance of the components in PEM fuel cells. The thermal conductivity of the GDL was measured in two directions, namely the in-plane and the through-plane directions taking into account the effect of the main parameters in the GDL which are the mean temperature, the compression pressure, the fibre direction, the micro porous layer (MPL) coating and polytetrafluoroethylene (PTFE) loading. Furthermore, the thermal conductivities of the membrane and the catalyst layer were measured in both directions, the in-plane and the through-plane, with considering the effect of the temperature and the Pt loading in the catalyst layer, and the effect of the water content and temperature on the membrane. This study is a comprehensive study on the thermal conductivity of PEM fuel cells and emphasized the importance of the thermal conductivity of the components in PEM fuel cells.
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Adigoppula, Vinay Kumar. "A study on Nafion® nanocomposite membranes for proton exchange membrane fuel cells." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3940.
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With a rise in demand for electricity and depletion of fossil fuel levels, researchers are looking for an alternative resource to generate power, one which is more environmentally friendly. Fuel cells are one of the best alternatives presently available and are considered by many to be the most promising energy sources with efficiencies of up to 60%. Presently, the cost associated with the usage of fuel cells available in the market is quite high. Researchers are trying to bring down costs associated with their usage and improve efficiency. PEM fuel cells are one of the most promising types of fuel cells. Researchers are currently trying to improve its efficiency by improving its electrolyte. Nafion® is one of the main electrolyte used in PEM fuel cells as it acts as proton conductor. Graphene has an exceptionally high surface area to volume ratio and excellent strength. Current research is focused on integrating graphene in PEM fuel cell electrolytes to improve performance. In this study, graphene is added to Nafion® in varying weight percentages to study the performance of the fuel cell given these changes. The graphene weight percentage is varied by 1, 2, 3, and 4. The fuel cell was operated and it was observed that with the addition of graphene there is an improvement in voltage, proton conductivity, and electron conductivity of the PEM fuel cell. The improvement of proton conductivity and electron conductivity followed a linear path with the increase in graphene weight percentage in the Nafion®. Physical properties of the Nafion® membrane with additional graphene were measured and found out that dielectric constant and thermal conductivity also improved linearly with an increase in graphene weight percentage.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Lee, Heon Joong Choe Song-Yul. "Modeling and analysis of a PEM fuel cell system for a quadruped robot." Auburn, Ala, 2009. http://hdl.handle.net/10415/1786.
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Zhang, Jingxin. "Investigation of CO tolerance in proton exchange membrane fuel cells." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0708104-193007/.
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22
Adams, Joshua H. "A Homogenization Model of a Proton Exchange Membrane Photoelectrochemical Cell." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1291998857.
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23
Agar, Ertan. "2-d Modeling Of A Proton Exchange Membrane Fuel Cell." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611587/index.pdf.
Full textAbstract:
In this thesis, a Proton Exchange Membrane Fuel Cell is modeled with COMSOL Multiphysics software. A cross-section that is perpendicular to the flow direction is modeled in a 2-D, steady-state, one-phase and isothermal configuration. Anode, cathode and membrane are used as subdomains and serpentine flow channels define the flow field . The flow velocity is defined at the catalyst layers as boundary conditions with respect to the current density that is obtained by using an agglomerate approach at the catalyst layer with the help of fundamental electrochemical equations. Darcy&rsquos Law is used for modeling the porous media flow. To investigate the effects of species depletion along the flow channels, a different type of cross-section that is parallel to the flow direction is modeled by adding flow channels as a subdomain to the anode and cathode. Differently, Brinkman Equations are used to define flow in the porous electrodes and the free flow in the channels is modeled with Navier-Stokes equations. By running parallel-to-flow model, mass fractions of species at three different locations (the inlet, the center and the exit of the channel) are predicted for different cell po- tentials. These mass fractions are used as inputs to the perpendicular-to-flow model to obtain performance curves. Finally, by maintaining restricted amount of species by having a very low pressure difference along the channel to represent a single mid-cell of a fuel cell stack, a species depletion problem is detected. If the cell potential is decreased beyond a critical value, this phenomenon causes dead places at which the reaction does not take place. Therefore, at these dead places the current density goes to zero unexpectedly.
24
Maasdorp, Lynndle Caroline. "Temperature proton exchange membrane fuel cells in a serpentine design." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1316_1307961639.
Full textAbstract:
The aim of my work is to model a segment of a unit cell of a fuel cell stack using numerical methods which is classified as computational fluid dynamics and implementing the work in a commercial computational fluid dynamics package, FLUENT. The focus of my work is to study the thermal distribution within this segment. The results of the work aid in a better understanding of the fuel cell operation in this temperature range. At the time of my investigation experimental results were unavailable for validation and therefore my results are compared to previously published results published. The outcome of the results corresponds to this, where the current flux density increases with the increasing of operating temperature and fixed operating voltage and the temperature variation across the fuel cell at varying operating voltages. It is in the anticipation of determining actual and or unique material input parameters that this work is done and at which point this studies results would contribute to the understanding high temperature PEM fuel cell thermal behaviour, significantly.
25
Jia, Nengyou. "Electrochemistry of proton-exchange-membrane electrolyte fuel cell (PEMFC) electrodes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0019/MQ54898.pdf.
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26
Pasricha, Sandip. "Modeling and Transient Degradation of Proton Exchange Membrane Fuel Cells." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/pasricha/PasrichaS0506.pdf.
Full textAbstract:
This thesis presents a model based approach to describe proton exchange membrane (PEM) fuel cell degradation with time. This degradation study involves analysis of voltage and current profiles of PEM membranes under transient load conditions. The data is collected from 80 membranes in an Independence1000 1000W PEM system over the life span of the membrane. The thesis also presents PEM fuel cell models developed and validated on a 500W SR-12 commercial PEM stack. Several static models from the literature are reviewed in terms of physical effects, parameterized for identification, and compared using measured data from the commercial PEM stack. The dynamic model is obtained by extending static current voltage profiles to include temperature dependence, and by dynamically modeling the temperature of the membrane. After inspecting all these models a simplified model is used for analyzing PEM fuel cell degradation and changes in physical phenomena in fuel cell observed over a period of time.
27
Page, Shannon Charles. "Testing Protocol Development for a Proton Exchange Membrane Fuel Cell." Thesis, University of Canterbury. Department of Mechanical Engineering, 2007. http://hdl.handle.net/10092/3519.
Full textAbstract:
Fuel cell technology has undergone significant development in the past 15 years, spurred in part by its unique energy conversion characteristics; directly converting chemical energy to electrical energy. As fuel cell technology has past through the prototype/pre-commercialisation development, there is increasing interest in manufacturing and application issues. Of the six different fuel cell types pursued commercially, the Proton Exchange Membrane (PEM) fuel cell has received the greatest amount of research and development investment due to its suitability in a variety of applications. A particular application, to which state-of-the art PEMFC technology is suited, is backup/uninterruptible power supply (UPS) systems, or stand-by power systems. The most important feature of any backup/UPS system is reliability. Traditional backup power systems, such as those utilising valve regulated lead acid (VRLA) batteries, employ remote testing protocols that acquire battery state-of-health and state-of-charge information. This information plays a critical role in system management and reliability assurance. A similar testing protocol developed for a PEM fuel cell would be a valuable contribution to the commercialization of these systems for backup/UPS applications. This thesis presents a novel testing and analysis procedure, specifically designed for a PEM fuel cell in a backup power application. The test procedure electronically probes the fuel cell in the absence of hydrogen. Thus, the fuel cell is in an inactive, or passive, state throughout the testing process. The procedure is referred to as the passive state dynamic behaviour (PSDB) test. Analysis and interpretation of the passive test results is achieved by determining the circuit parameter values of an equivalent circuit model (ECM). A novel ECM of a fuel cell in a passive state is proposed, in which physical properties of the fuel cell are attributed to the circuit model components. Therefore, insight into the physical state of the fuel cell is achieved by determining the values of the circuit model parameters. A method for determining the circuit parameter values of many series connected cells (a stack) using the results from a single stack test is also presented. The PSDB test enables each cell in a fuel cell stack to be tested and analysed using a simple procedure that can be incorporated into a fuel cell system designed for backup power applications. An experimental system for implementing the PSDB test and evaluating the active performance of three different PEM fuel cells was developed. Each fuel cell exhibited the same characteristic voltage transient when subjected to the PSDB test. The proposed ECM was shown to accurately model the observed transient voltage behaviour of a single cell and many series connected cells. An example of how the PSDB test can provide information on the active functionality of a fuel cell is developed. This method consists of establishing baseline performance of the fuel cell in an active state, in conjunction with a PSDB test and identification of model parameter values. A subsequent PSDB test is used to detect changes in the state of the fuel cell that correspond to performance changes when the stack is active. An explicit example is provided, where certain cells in a stack were purposefully humidified. The change in state of the cells was identified by the PSDB test, and the performance change of the effected cells was successfully predicted. The experimental test results verify the theory presented in relation to the PSDB test and equivalent circuit model.
28
Puthiyapura, Vinod Kumar. "Development of anode catalysts for proton exchange membrane water electrolyser." Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2446.
Full textAbstract:
The proton exchange membrane water electrolyser (PEMWE) is a promising technology for the production of hydrogen from water. The oxygen evolution reaction (OER) has a high over potential cf. with the hydrogen evolution reaction and is one of the main reasons for the high energy demand of the electrolyser. RuO₂ and IrO₂ are the most active catalyst for OER, but are costly, making the electrolyser system expensive. In general, it is important to use stable, active and cheap catalysts in order to make a cost efficient electrolyser system. Supporting the active catalyst on a high surface area conducting support material is one of the approaches to reduce the precious metal loading on the electrode. Antimony tin oxide (ATO) and indium tin oxide (ITO) were studied as possible support materials for IrO₂ in the PEMWE anode prepared by the Adams method. The effect of the support material on the surface area, electronic conductivity, particle size and agglomeration were investigated. The IrO₂ showed highest conductivity (4.9 S cm-¹) and surface area (112 m2 g-¹) and decreased with the decrease in the IrO₂ loading. Using the catalysts in the membrane electrode assemblies (MEA) with Nafion®-115 membranes, at 80°C showed that the catalyst with better dispersion and conductivity gave better performance. The unsupported IrO₂ and 90% IrO₂ supported on ATO and ITO showed the best performance among all the catalysts tested, achieving a cell voltage of 1.73 V at 1 A cm-². A lower IrO₂ loading decreased the conductivity and surface area. The IrO₂ particle size and bulk conductivity of the supported catalyst significantly influenced the MEA performance. Overall, it is important to maintain a conductive network of IrO₂ on the non-conducting support to maintain the bulk conductivity and thus reduce the Ohmic potential drop. Although RuO₂ is the most active catalyst for OER, it lacks stability on long term operation. RuxNb1-xO₂ and IrxNb1-xO₂ catalysts were synthesized and characterized, to try to develop stable electrodes for PEMWE. However the Adams method of catalyst synthesis formed a sodium–niobium complex making it unsuitable for preparation of Nb based catalysts. In both Adams and hydrolysis methods of synthesis, the addition of Nb ₂O₅ decreased the anodic charge and electronic conductivity of the catalyst due to the dilution of the active RuO₂. The RuO₂ catalyst showed the best performance in MEA evaluation compared to the bimetallic catalyst (1.62 V and 1.75 V @1 A cm-² for RuO₂(A) and RuO₂(H) respectively). A higher stability for bimetallic catalyst compared to the monometallic catalysts was obtained from the continuous CV cycling and MEA stability test.
29
Kleszyk, Piotr Marcin. "Rapid screening of proton exchange membrane fuel cell cathode catalysts." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/80107/.
Full textAbstract:
One of the major bottlenecks in catalyst development for proton exchange membrane fuel cell (PEMFC) is the lack of fast high-throughput testing methods. Fast screening techniques enable a large number of catalysts to be tested in a relatively short time under the same conditions. This project was focused on developing systems for screening catalysts used for the oxygen reduction reaction (ORR) at the cathode of PEMFCs. The first system developed was the 64 channel pin electrode array, using liquid electrolyte. The developed method improved both the quality and reproducibility of the data and has been used to rank catalyst samples, as well as to optimize loadings and the preparative methods of inks. The second system developed was a 25 channel array fuel cell, which operated under conditions analogous to real fuel cell environments. Both methods allowed trends in characteristics and activities of a series of catalysts to be established more rapidly than individual single-electrode methods such as half cell, rotating disc electrode (RDE) or fuel cell. The results from the two high-throughput methods are compared to those of the single channel systems. The mass and specific activities towards reduction of oxygen were studied using a series of Pt/C and PtCo/C catalysts. The catalytic properties of the Pt based carbon-supported catalysts were related to their structure e.g. particle size and lattice parameter, which were obtained mainly using Xray diffraction (XRD). It was found that the results acquired using parallel screening methods were similar to those collected with a RDE and a fuel cell. The thesis concludes with suggestions regarding the future improvement/development of high-throughput techniques. For the 64 channel array system the problem associated with the corrosion of the components should be solved. Similarly, the major changes for the array fuel cell would be to modify a heating system and further development of the anode flow field.
30
Kalapos, Thomas Lawrence. "Interaction of Water with the Proton Exchange Fuel Cell Membrane." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1175891061.
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31
Leonardy, Adrianus. "Non-Noble Metal Electrocatalysts for Proton Exchange Membrane Fuel Cell." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12036.
Full textAbstract:
Transition metal-nitrogen complex have shown promising electrocatalytic activity towards the oxygen reduction reaction (ORR) that can potentially replace the platinum-based electrocatalysts in fuel cell, which generally suffer from scarcity and instability issue. Iron and cobalt have been reported to posses the best electrocatalytic performance in comparison with other transition metals due to the nature of their d-electron configuration that fulfill the prerequisite strong back-bonding for the activation of oxygen molecule. Apart from the metal active centre, other factors such as catalyst support, electrode thickness and surface-nitrogen content have also been considered play important roles to improve the catalytic performance of transition-metal-nitrogen complex materials. In this study we integrated those factors and approaches to create non-noble metal-based electrocatalysts for proton exchange membrane fuel cell (PEMFC) with improved catalytic activity. Iron and cobalt were used as ORR metal active centers and different type of carbon supports were employed as electrocatalysts supports. Three different electrocatalysts were developed in this project, including ironcobaltnitrogen complex supported carbon nanotubes that were grown on carbon paper substrate, iron-cobalt-nitrogen complex incorporated vertically aligned carbon nanotubes and iron-cobalt-nitrogen complex incorporated vertically aligned nitrogen-doped carbon nanotubes. The electrochemical performances of those electrocatalysts were compared with platinum-based electrocatalyst, which is the most common commercial electrocatalysts recently. The results show that the developed non-noble metal-based electrocatalysts posses improved electrocatalytic properties in terms of electrochemical surface area, electron transfer number, kinetic rate constant, durability and methanol fuel tolerance.
32
Primucci, Mauricio. "Experimental characterization and diagonosis tools for proton exchange membrane fuel cells." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/96767.
Full textAbstract:
A fuel cell is a device that gives electric power directly from electrochemical reduction and oxidation reactions. PEM fuel cells
present some properties that make them appropriate for portable and transport applications: high efficiency, no emissions,
solid electrolyte, low operating temperatures and high power density. However, some technical problems can be improved,
durability of the materials and the appropriate control of the operating conditions. One important aspect of the operating
conditions is the water management. The right water content is needed in the electrolyte and catalyst layers to maximize the
efficiency of the PEMFC by minimizing the voltage losses. Water content in the fuel cell is given basically by the generation of
the water in the cathode due to the reaction, the humidity of the inlet gases and the transport trough the membrane.
This thesis studies, proposes and compares different experimental characterisation methods aimed to provide performance
indicators of the PEMFC water state.
A systematic use of Electrochemical Impedance Spectroscopy technique is presented and its results are studied in order to
analyse the influence of different operating conditions over the PEMFC response. The variables under analysis include: load
current, pressure temperature and gas relative humidity. All these variables are considered with inlet gases feeding: H2/O2
and H2/Air.
A set of relevant characteristics from the EIS response has been considered. Several equivalent circuits has been analysed
and those that have the best fitting with the experimental EIS data are selected.
When air is used as oxidant, a simple equivalent circuit with a resistance and a Warburg element is proposed. When Oxygen
is used as oxidant, a more complex equivalent circuit is needed. A detailed sensitive analysis is performed indicating those
parameters that best capture the influence of the operating conditions.
A new experimental characterisation technique, based on the inlet gases humidification interruption is proposed. This
dynamic technique combines the information extracted from EIS and the temporal response in order to study the water
transport and storage effects in the PEMFC. Two advantages of this proposed technique is the simple hardware configuration
used and the relative low impact on the fuel cell response, making attractive the humidification interruption as an in-situ
technique.
Three different sets of performance indicators are proposed as diagnosis tool.
Relevant Characteristics from the EIS response, if properly monitored, can give a diagnostic of the fuel cell internal state. After
an analysis, the chosen ones are: low and high frequency resistances (RLF and RHF) and the frequency of the maximum
phase. These RC are helpful to determine if the PEMFC with the current operating conditions is well humidified. If the zone
defined by RLF decrease, RHF slight increase and the frequency of the maximum phase increase is minimal, the cathode is
optimally humidified.
Equivalent Circuit are used in order to give a physical interpretation. The selected parameters as performance indicators are:
membrane resistance, Rm, time constant and resistance of diffusion process (using Warburg elements: Tw and Rw). In this
case, the humidification of the fuel cell is optimum if the zone where Rw and Tw decrease and Rm has slow increase is
minimal.
Model Based performance indicators are proposed: Rm, effective diffusion coefficient, Deff and effective active area, Aeff. The
optimal humidification occurs when the zone where Deff is stationary and Rm has not changed significantly, is minimal. The
parameter Aeff involved in this last diagnosis procedure can be detached from the humidification interruption test and be
used to estimate the effective active area and then is also helpful to compare the PEMFC performance in different operating
conditions.Una pila de combustible es un dispositivo que da energía eléctrica a partir de reacciones electroquímicas de reducción y oxidación. Las pilas del tipo PEMFC presentan propiedades que las hacen adecuadas para aplicaciones de transporte: alta eficiencia, cero emisiones, electrolito sólido, bajas temperaturas de operación y alta densidad de potencia. Sin embargo, algunos problemas técnicos deben ser estudiados: la durabilidad de los materiales y la correcta selección de las condiciones de funcionamiento. Una de las más importantes es la gestión del agua. Un balance adecuado del agua en la pila es necesario para maximizar la eficiencia de la PEMFC reduciendo al mínimo las pérdidas de tensión. El contenido de agua en la PEMFC viene dado por su generación en el cátodo debido a la reacción, la humedad de los gases de entrada y el transporte de agua a través de la membrana. La tesis estudia, propone y compara los diferentes métodos de caracterización experimental con el objetivo de obtener indicadores del estado del agua en la PEMFC. Se realiza un uso sistemático de la técnica “espectroscopía de impedancia electroquímica (EIS)” y el análisis de la influencia de las diferentes condiciones de operación sobre la respuesta de la PEMFC. Las variables estudiadas son: corriente de carga, presión de los gases, temperatura, humedad relativa y también la alimentación de los gases de entrada: H2/O2 y H2/aire. Se presenta un conjunto de características relevantes de la respuesta del EIS y se usan para dar valores iniciales a los circuitos equivalentes. Se estudian diferentes configuraciones de circuitos equivalentes y se seleccionan aquellos que tienen la mejor conexión con los datos experimentales. Se realiza un análisis de sensibilidad de los parámetros de los circuitos equivalentes con respecto a las diferentes condiciones de operación, para encontrar aquellos que sean útiles para representar estas variaciones. Se propone una nueva técnica experimental de caracterización, basada en la interrupción de la humidificación de los gases de entrada. Esta técnica combina la información de la respuesta temporal con la frecuencial (EIS) y es útil para analizar la influencia del agua en la respuesta de la PEMFC. Algunas ventajas de esta técnica son: la fácil implementación física y el bajo impacto sobre la respuesta de la PEMFC, lo cual convierte esta técnica en candidata para ser utilizada “In-situ”. Se proponen tres conjuntos de indicadores de comportamiento de la pila como herramientas de diagnosis. En primer lugar, se presentan las “Características Relevantes” de la respuesta de la EIS que dan un diagnóstico del estado interno de la PEMFC. De entre ellas se selecciona como indicadas: las resistencias de baja y alta frecuencia (RLF y RHF) y la frecuencia del máximo de fase. Estas características sirven para determinar la correcta humidificación de la pila en las condiciones actuales de operación. El cátodo está correctamente humidificado si la respuesta de las características, muestran que la zona definida por RLF bajando, RHF subiendo ligeramente y la frecuencia de la máxima fase está subiendo, es mínima. En segundo lugar, se usan los “Circuitos Equivalentes” para dar una interpretación física a los indicadores. Los parámetros seleccionados son: la resistencia de la membrana, Rm, la resistencia y la constante de tiempo de la difusión (Rw y Tw). En este caso, la humidificación correcta del cátodo ocurre cuando la zona donde Rw y Tw bajan y Rm sube ligeramente, es mínima. Por ultimo, se proponen indicadores de comportamiento utilizando un modelo: Rm, coeficiente de difusión efectivo, Deff y el área activa efectiva, Aeff. La humidificación óptima del cátodo ocurre cuando la zona donde Deff es estable y Rm no cambia significativamente, es mínima. El parámetro Aeff es útil para estimar el área activa efectiva aun cuando no se realice una interrupción de humidificación y para comparar la respuesta de la PEMFC bajo diferentes condiciones de operacion
33
Cheddie, Denver Faron. "Computational modeling of intermediate temperature proton exchange membrane (PEM) fuel cells." FIU Digital Commons, 2006. http://digitalcommons.fiu.edu/etd/2124.
Full textAbstract:
A two-phase three-dimensional computational model of an intermediate temperature (120 - 190 ˚C) proton exchange membrane (PEM) fuel cell is presented. This represents the first attempt to model PEM fuel cells employing intermediate temperature membranes, in this case, phosphoric acid doped polybenzimidazole (PBI). To date, mathematical modeling of PEM fuel cells has been restricted to low temperature operation, especially to those employing Nafion® membranes; while research on PBI as an intermediate temperature membrane has been solely at the experimental level. This work is an advancement in the state of the art of both these fields of research. With a growing trend toward higher temperature operation of PEM fuel cells, mathematical modeling of such systems is necessary to help hasten the development of the technology and highlight areas where research should be focused.
This mathematical model accounted for all the major transport and polarization processes occurring inside the fuel cell, including the two phase phenomenon of gas dissolution in the polymer electrolyte. Results were presented for polarization performance, flux distributions, concentration variations in both the gaseous and aqueous phases, and temperature variations for various heat management strategies. The model predictions matched well with published experimental data, and were self-consistent.
The major finding of this research was that, due to the transport limitations imposed by the use of phosphoric acid as a doping agent, namely low solubility and diffusivity of dissolved gases and anion adsorption onto catalyst sites, the catalyst utilization is very low (~1 - 2 %). Significant cost savings were predicted with the use of advanced catalyst deposition techniques that would greatly reduce the eventual thickness of the catalyst layer, and subsequently improve catalyst utilization. The model also predicted that an increase in power output in the order of 50% is expected if alternative doping agents to phosphoric acid can be found, which afford better transport properties of dissolved gases, reduced anion adsorption onto catalyst sites, and which maintain stability and conductive properties at elevated temperatures.
34
Rezaei, Niya Seyed Mohammad. "Process modeling of impedance characteristics of proton exchange membrane fuel cells." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/53653.
Full textAbstract:
The impedance characteristics of proton exchange membrane (PEM) fuel cells are studied and analyzed in this thesis. The modeling approaches presented in literature are thoroughly reviewed and categorized as the measurement-modeling and process-modeling approaches. In the former category, a hypothetical equivalent circuit which has the impedance characteristics similar to measured impedances is presented. Since the equivalent circuit is not directly resulted from the physical and chemical properties of the PEM fuel cells, the majority of the measurement-modeling approaches lead to dubious conclusions. In the process-modeling approach, on the other hand, the governing equations of the fuel cell must analytically be solved to determine and the impedance. However, a few process-modeling approaches presented in literature have shown to be indirectly based on the same assumptions as the measurement-modeling approach, and hence, those can also lead to similar conclusions. Therefore, these process-modeling approaches are referred to as the semi-process models here.
In this thesis, the first complete process model for PEM fuel cells is presented which is not based on the above-mentioned assumptions. For each source of the losses in the fuel cell (i.e., the ohmic, activation and concentration overpotentials), a process model and equivalent circuit are obtained and compared against the impedance measurements reported in literature. The complete model (obtained by combining the models of the three losses) is then verified against the impedances measured in different operating conditions. Using the verified model, the measured Nyquist plots of the PEM fuel cells reported in literature are categorized. As a result, the dominant physical and chemical parameters controlling various arcs of the Nyquist plot are determined. Finally, the sensitivity analysis of the impedance characteristics of fuel cells is conducted using the verified model. As a result of this analysis, a minimum change in the operating conditions which results in statistically different Nyquist plots are determined.
Finally, as an application of the model presented here, the impedance of the cell in the anode and cathode starvation modes are studied. It is shown that the anode starvation cannot be recognized from the impedance measurements, as predicted by the model.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
35
Valenzuela, Jorge Ignacio. "Electrochemical impedance spectroscopy options for proton exchange membrane fuel cell diagnostics." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/266.
Full textAbstract:
Electrochemical impedance spectroscopy (EIS) has been exploited as a rich source of Proton Exchange Membrane Fuel Cell (PEMFC) diagnostic information for many years. Several investigators have characterized different failure modes for PEMFCs using EIS and it now remains to determine how this information is to be obtained and used in a diagnostic or control algorithm for an operating PEMFC.
This work utilizes the concept of impedance spectral fingerprints (ISF) to uniquely identify between failure modes in an operating PEMFC. Three well documented PEMFC failure modes, carbon monoxide (CO) poisoning, dehydration, and flooding were surveyed, modelled, and simulated in the time domain and the results were used to create a database of ISFs. The time domain simulation was realized with a fractional order differential calculus state space approach.
A primary goal of this work was to develop simple and cost effective algorithms that could be included in a PEMFC on-board controller. To this end, the ISF was discretized as coarsely as possible while still retaining identifying spectral features using the Goertzel algorithm in much the same way as in dual tone multi-frequency detection in telephony. This approach generated a significant reduction in computational burden relative to the classical Fast Fourier Transform approach.
The ISF database was used to diagnose simulated experimental PEMFC failures into one of five levels of failure: none (normal operation), mild, moderate, advanced, and extreme from one of the three catalogued failure modes. The described ISF recognition algorithm was shown to correctly identify failure modes to a lower limit of SNR = 1dB.
36
Singer, Simcha Lev. "Low platinum loading electrospun electrodes for proton exchange membrane fuel cells." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38280.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 104-106).
An experimental study was performed to evaluate the utility of electrospun carbon nanofiber supports for sputtered platinum catalyst in proton exchange membrane fuel cells. The performance of the sputtered nanofiber supports was similar to that of sputtered commercial gas diffusion layers in single cell fuel cell tests. However, sputtered platinum electrodes performed significantly worse than commercial thin film electrodes due to high activation and concentration voltage losses. Cyclic voltammetry and rotating disc electrode experiments were performed in order to evaluate the influence of platinum loading and particle size on the electrochemical active area and oxygen reduction performance of the sputtered platinum. Active area per weight catalyst decreased with sputtering time, and the oxygen reduction activity slightly increases with increasing sputtering time. Both of these effects are thought to be due to increasing platinum particle size as sputtering time is increased.
by Simcha Lev Singer.
S.M.
37
Wu, Chien-Shun, and 吳千舜. "Novel Proton Exchange Membrane." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/44190741451326289171.
Full textAbstract:
碩士國立中央大學
化學研究所
92
Conventional membranes such as Nafion suffer from the swelling and methanol crossover under high methanol concentration fuel stream. More durable proton exchange membrane (PEM) has received increasing interests from academic and industrial research for direct methanol fuel cell (DMFC) application. However, most efforts to reduce crossover effect is achieved by discriminating water and methanol permeation, usually at the cost of the proton conductivity. This dilemma is resolved by taking advantage of the novel conducting mechanism, which occurs in nano-ionics: membranes with and channels decorated with closely spaced sulfonic groups in connected nano-pores. Here proton transfer is established by the directional tunneling through the surface charge field created by finely dispersed nano flow channel. Previous studies have demonstrated that polymerization of phenolic in the PVdF and PVdF-HFP copolymers solution forms a thin crust of hydrophilic shell on the sol surface. Current study expands such design using inverse micelle formation where the sulfonic groups are exposed and extend in the solvent permeation channel (with dimensions less than 20 nm). The closely spaced arrangements establish a novel proton conducting behavior entirely different from those previously observed in other systems. As a result of the nano-flow structure, crossover is effectively reduced. Since the PVdF-HFP substrate is partially crystallized, the film withstands solvent swell and preserved the membrane dimensions even in high methanol concentration. Further cross-linking of the product leads to highly chemical and thermally stable membrane suitable for the application of direct methanol fuel cell (DMFC) .
38
Hong-Hong and 洪紘. "Performance of humidifier membranes for proton exchange membrane fuel cells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/cw2zs7.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
106
In this study, the membranes used in the planar membrane humidifier in the proton exchange membrane fuel cell system were developed. Poly (ethersulfone) (PES) and sulfonated poly (sulfonated poly(ether sulfone)) (SPES) blend membranes (i.e, SPES/PES= 0.3/1.0, 0.4/1.0, and 0.5/1.0 by wt.) containing nano-poorous tubes inside the membranes were fabricated by using solution casting method. The film surface of each membrane was covered with a layer of highly hydrophilic poly (vinyl alcohol (PVA) nano-fiber film, which possesses high hydophylic property. The high moisture absorption of the highly hydrophilic nano-fiber film covered on the surface of the humidifier membrane not only improved the humidity of dry gas but also reduced the dry gas permeation through the humidifier membrane.
39
Chen, Po-cheng, and 陳柏丞. "Phosphoric acid dopedpolybenzimidazole membrane forhigh temperature proton exchange membrane." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/54630472108072543042.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
104
This study prepares PBI-XCl5/epoxy blending membrane as well as PBI-XCl6-/epoxy blending membrane and conduct all types of analyses on membrane materials as well as single cell testing. FTIR analysis is carried out on PBI (Polybenzimidazole) powder. Analyses on membrane materials include SEM (Scanning Electron Microscope), EDS (Energy Dispersive Spectrometer), TGA (Thermogravimetric Analysis), acid content analysis, and mechanical properties testing. The FTIR spectrum shows that PBI has been successfully synthesized and composite membranes such as PBI-XCl5 / epoxy and PBI-XCl6- / epoxy that have been prepared are undergoing SEM to observe the membrane surface and cross-section structures. EDS analyzes the composition of elements within the membrane and finds that X within the membrane materials can be used to confirm that the membranes have been successfully prepared. TGA inspects the thermal stability of the membrane materials. When temperatures are equal to and less than 200℃, there is no thermal cracking. Therefore, it is confirmed that the membrane materials can be applied to PEMFC. Acid content analysis on the membrane materials shows that the content of phosphoric acid significantly increases when membranes contain XCl5 and XCl6-. Analysis on mechanical strengths of the membrane materials shows that the two membrane materials show lower mechanical strengths compared to the mechanical strength of PBI / epoxy. Finally, we put the membranes and catalyst layers together to obtain the MEA (Membrane Electrode Assembly). Single cell tests are conducted on the MEA at 160℃ and 190 ℃. Experimental data shows that the maximum power and current density of the composite membrane mixed with XCl5 exhibit some improvements compared to the PBI-epoxy membrane. And the properties of the PBI-XCl6-/epoxy membrane are better than the PBI-XCl5 / epoxy membrane.
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LIU, YU-TUNG, and 劉宥彤. "Preparation of Reactive Polyhedral Oligomeric Silsequioxanes / Sulfonated Polyimide Network Proton Exchange Membranes for Applications in Proton Exchange Membrane Fuel Cell." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/5mht6d.
Full textAbstract:
碩士國立雲林科技大學
化學工程與材料工程系
107
In this study, we attempt to prepare a series of reactive polyhedral oligomeric silsesquioxane (POSS) / sulfonated polyimide (SPI) network proton exchange membranes (PEM). The preparations of POSS/SPI network PEM are based on reactive POSS (OFG-POSS) and sulfonated poly(amic acid) (SPAA). There OFG-POSS are synthesized by using Octakis(dimethylsilyloxy)silsesquioxane (Q8M8H), Allyl glycidyl ether (AGE) and Allyl 1,1,2,3,3,3-hexafloropropyl ether (AHFPE) to react to obtain a structure owing 4 epoxy groups and 4 fluorine groups. These reactive POSS are named as OFG-POSS. These SPAA are synthesized by using 1,4,5,8-Naphthalenetetracarboxylic acid dianhydride (NTDA), 2,2’- Bis(tri-fluoromethyl) benzidine (TFMB), α,ω-diaminopropyl polydi-methylsiloxane (PDMS), sulfonated 4,4’-(1,1’-Biphenyl-4,4’-diyldioxy)dianiline (BAPBDS). The OFG-POSS firstly react with SPAA, and the mixture is then further reacted through thermal imiderization to get POSS/SPI network PEMs. The molecular design views of composite and network PEMs are based on: Network structures own excellent mechanical and thermal properties, the retained water capacity. Further, the good dispersion of POSS and high POSS contents will increase proton conductivity. The good dispersion for POSS will increase the proton conductivity and reduced methanol crossover. The abilities of anti-oxidation and anti-hydrolysis will be enhanced due to containing fluorine in PEMs. The increasing miscibility will increase proton conductivity due to reducing resistance of interface through good intermix of fluorine structure and Nafion® solution. The synthesized proton exchange membrane of the network structure composite was identified by FT-IR and NMR to prove the correctness and integrity of the reaction. Meantime, the characteristics of proton exchange membranes include micro structure analysis, water uptake, oxidation test, state of water, dimension stability and proton conductivity methanol permeability, ion exchange capacity (IEC), and mechanic properties etc. Using these experiment results and the commercialize Nafion® 117 as references, we can evaluate the application feasibility of SPI composite PEMs as fuel cell PEMs.
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Liu, Chia-He, and 劉家和. "Control of Proton Exchange Membrane Fuel Cell Systems." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/91581428326136208059.
Full textAbstract:
碩士國立臺灣科技大學
化學工程系
93
In recent years, the fuel cell has been used widely in many fields such as battery, power plant, the power of motors . Because of the academic research difference, the mathematical model of fuel cell has been developed gently. Most of the research are based on non-linear parial differential equation for studying the inner mechanizer of fuel cell and the flow field design and we could realize simply and deeply about the inner transfer phenomena (mass transfer, heat transfer and the elechemistry reaction behavior of a fuel cell )by a rigorous mathematical model. But the bulk calculating costs and the verbose results cause the difficulty of the dynamic analysis. Not only using the fast and efficiency mathematical method but also the over-simply and realizable math mode to support the studying of the system integration & the problem of control system design.Here,we will take the mathematical eauations from the previous papers.We will not only try to realize some operating problems of the fuel cell stack from macroscopic view base on semi-emperical & empirical equations,but also offering some good suggestions to the stack design via the system dynamic simulations.Oxygen starvation phenomena will seriously damage the polymer membrane of the system.In this paper,we will focus on how to prevent the oxygen starvation occurs by designing the control structure.We hope the serious phenomena would not happen in our system by developing efficiency control structure.
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Rowe, Andrew Michael. "Mathematical modeling of proton exchange membrane fuel cells." Thesis, 1997. http://hdl.handle.net/1828/3185.
Full textAbstract:
A good understanding of the various mass and heat transport, and electrochemical re-action processes is required for design strategies that lead to increased performance of proton exchange membrane (PEM) fuel cells. Traditionally, attempts at understand¬ing how these processes interact has been through mathematical modeling where efforts have focussed on understanding the cathode. The interaction between mass transport, membrane hydration and the effects of heat generation and transfer com¬plicates our understanding of relevant processes, hampering the effort to improve fuel cell performance.
To further our basic understanding of how the power density of a PEM fuel cell can be increased, and, thereby, decrease the cost of a complete fuel cell system, a comprehensive performance model of a PEM fuel cell has been formulated and investigated. This model explicitly examines the anode as well as the cathode, and includes the effects of energy transfer as temperature control is critical to PEM cells. The results of this model suggest that humidification of the cathode gas stream may be reduced at high operating currents, the temperature peak across a single cell increases as operating temperature decreases, and the gas backing has a significant effect on mass transport at typical operating potentials, especially with air operation.
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Gan, Chai-Teck, and 顏在德. "Inorganic/Polymer Hybrid Material For Proton Exchange Membrane." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/98726537745679547602.
Full textAbstract:
碩士國立臺灣大學
化學工程學研究所
94
In our study, we try to synthesize a series of novel inorganic-organic hybrid polymer to be used in proton exchange membrane of fuel cell. We hope to exploit a lower cost membrane to partially replace nafion, which is an expensive commercial proton exchange membrane in fuel cell. There are two major parts in our research. First, we synthesize a series of novel hybrid polymer which contains sulfonic acid functional group in side chain. To introduce sulfonic acid into our polymer, two kinds of silane, 3-aminopropylmethyldiethoxysilane(APDES) and 3-aminopropyl-triethoxysilane(APTES), which contains amine functional group, are used to react with 1,3 propane sultone. After successfully introduce sulfonic acid group, we do a sol gel process via hydrolysis and condensation of alkoxide functional group (OR) of silane. Besides, we introduce DGEBA via a ring-opening reaction with APDES to improve the mechanical property of membrane. In second part of our study, we synthesize a new serial of hybrid basic polymer and doping some inorganic acid into our polymer to get an acid-base complex structure proton exchange membrane. The reaction of second part of our study is similar with first one part. The major difference is not to do sulfonation reaction in inorganic-organic hybrid polymer, but to dope inorganic acid into polymer directly via acid-base complex formation. In analysis part, we use FTIR to determine structure of membrane. Furthermore, TGA, DSC and SEM are used in thermal properties and morphology analysis. AC impedance analysis and diffusion cell are used in proton conductivity and methanol permeability analysis. Tensile strength testing is used in mechanical property analysis. In the first part of our study, the proton conductivity of membrane is in the range of 10-4~10-3 S/cm. In second part of our study, the proton conductivity is in the range of 10-3~10-2 S/cm, which close to proton conductivity of nafion in our testing system. The methanol permeability of our study is in the range of 10-7~10-6 cm2/s, which is better than permeability of nafion 117(10-6 cm2/s). By our study, we provide an alternative proton exchange membrane research for fuel cell application.
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Ma, Ying-Wei, and 馬英暐. "Adaptive Control of Proton Exchange Membrane Fuel Cell." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/62890400462285844290.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
94
The purpose of this thesis is to design an adaptive controller for Proton Exchange Membrane Fuel Cell. The objective of adaptive control scheme aims to maintain a desired steady voltage output under various loading conditions of fuel cell operation. First, an application of electro-chemical reactions of fuel cell results in a dynamic model, which is further simplified to a coupled nonlinear multi-input and multi-output system. Second, the linear recursive least square identification scheme is used to generate a 2nd order mathematical model of fuel cell. Based on the identification results, a SISO adaptive controller is designed and tested for the fuel cell. It is verified that the adaptive controller works successfully. At various fixed hydrogen flow rate, the voltage output has been well maintained under various current loads by adjusting the air flow rate.
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Chen, JhihYi, and 陳智逸. "Fabrication and Morphology Study of Proton Exchange Membrane." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/08103863961988275698.
Full textAbstract:
碩士南台科技大學
化學工程與材枓工程系
95
Many researchers has made efforts to new material exploration and old material modification for proton exchange membranes (PEMs). The aim of this study is to develop a new material via several chemical processes. PEMs made from Ultra-high molecular weight polyethylene(UHMWPE) was first grafted by styrene monomer via emulsion polymerization.The UHMWPE-g-PS membrane was then ionized by sulfonation. This research is mainly to study the morphology of the membrane.After the UHMWPE-g-PS polymer sulfonized by fuming sulphuric acid, the proton on the benzene ring of the side-chain of polystyrene is substituted by SO3H+ group .The membrane with positive-charged SO3H+ group is a polyelectrolyte. As the SO3H+ groups attract each other by ion dipoles, they become ion cluster. The concentration of reacted styrene monomer seems to affect the morphology of cluster. Fourier transform infrared spectroscopy (FTIR)was used to make sure grafting reaction occurred. The membrane is hydrophilic after sulfonation. Different water content in the membrane affects the conduction of proton. Variation of water content in the membrane is characterized by thermogravimetric analyzer (TGA) and FTIR, it evidenced the formation of cluster. Transmission electron microscopy (TEM) was used to confirm the morphology of the membrane. The relationship between the morphology and proton conductivity is characterized by impedance analyzer.
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Lai, Yu-Ling, and 賴宥羚. "Proton Exchange Membrane Fuel Cell - Carbon Monoxide Poisoning." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/cx59x6.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
107
The first part of the study we model the performance of proton exchange membrane fuel cell under trace content of carbon monoxide in the anode feed. The process was simulated by the surface adsorption, desorption and surface electrochemical reactions. It was found the concentration of hydrogen has minor effect on the cell performance if pure hydrogen is used. However, if trace amount of carbon monoxide is included, cell performance is decreased significantly at low hydrogen concentration even the CO content is as low as 10ppm. The second part is injection of a small amount of air into the anode fuel stream can reduce the CO level. The performance of a PEMFC is investigated when subject to CO poisoning under different operation conditions and a model is hereby proposed. By applying 5% air bleeding, the cell output current can be restored to 90% within 10 min, even at high CO concentrations (200 ppm). The third part is to establish a model of carbon monoxide poisoning in proton exchange membrane fuel cell. Stefan-Maxwell equations are used to describe the multi-component gas diffusion. Model includes the capillary liquid transport phenomena in the GDL, liquid water pressure effects, electrochemical kinetics, and transport in the membrane. We evaluate the effect of liquid pressure in the gas diffusion layer at different cathode relative humidity.
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Lin, Hung-Chih, and 林泓志. "Hydrophilic treatment on composite membrane of proton exchange membrane fuel cell." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/22676534197292964877.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
99
There are four parts in this study. The first part is to insert SiO2 to anode catalyst layer which made from sol-gel process. And I prepare 0 wt.%、5 wt.%、10 wt.%, and15 wt.% SiO2 on the catalyst layer of PEMFC. The result shows that electrochemical surface area decreases as the SiO2 content is increasing. The second part is investigated the performance on fuel cell with different anode fuel and various anode humidifier temperature. The result shows that use oxygen is better than air on PEM fuel cell performance. Under non-humidified condition in cathode, the cell performance increase as the anode humidifier temperature is increasing. On the higher cell temperature, there is humidifier in cathode, the cell performance decrease due to the increase of mass transfer resistance on cathode by flooding. The third part is investigated the performance of two kind of composite membranes and commercial Nafion 117 at various anode humidifier temperature. The result shows that performance of Nafion 117 is better than composite membranes. The composite membrane which using cast way that membrane conductivity is better in high current. The fourth part is study the influence of hydrophilic SiO2 made from TEOS in sol-gel process on the anode catalyst layer and composite membrane under various anode humidifier temperatures. The result shows that the performance of MEA which add SiO2 in anode catalyst layer and membrane is better. Due to SiO2 can retain water in anode catalyst layer and membrane. Let the anode catalyst layer and membrane increase the wettability under low humidifier temperature. At cathode humidified case, the impedance spectra of single cell operated at various anode humidifier temperatures, shows that the diameter of semicircle decrease with increasing current. As the current reach a minimum resistance value, the diameter of semicircle increase with increasing current that is due to the mass transfer resistance increase.
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Yang, Bo Ph D. "Development of new membranes for proton exchange membrane and direct methanol fuel cells." Thesis, 2004. http://hdl.handle.net/2152/29868.
Full textAbstract:
Proton exchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC) are drawing much attention as alternative power sources for transportation, stationary, and portable applications. Nafion membranes are presently used in both PEMFC and DMFC as electrolytes, but are confronted with a few difficulties: (i) high cost, (ii) limited operating temperature of < 100 °C, and (iii) high methanol permeability. With an aim to overcome some of the problems encountered with the Nafion membranes, this dissertation focuses on the design and development of a few materials systems for use in PEMFC and/or DMFC. The incorporation of hydrous Ta₂O₅·nH₂O into Nafion membrane as well as the electrodes is shown to help the cell to retain water to higher temperatures. Membrane-electrode assembly (MEA) consisting of the composite membrane shows better cell performance at 100 and 110 °C than that with plain Nafion membrane, and a high power density of ~ 650 mW/cm² at 100 °C is obtained with H₂ - CO mixture as the fuel due to a significant alleviation of the CO poisoning of the catalysts. Sulfonated poly(etheretherketone) (SPEEK) membranes with various sulfonation levels are prepared and investigated in DMFC. With a sulfonation level of ~ 50 %, the SPEEK membranes exhibit low methanol permeability and electrochemical performance comparable to that of Nafion at around 60 °C, making it an attractive low-cost alternative to Nafion. From a comparative study of the structural evolutions with temperature in 2 M methanol solution, it is found that the lower methanol permeability of SPEEK membranes is related to the less connected and narrower pathways for water/methanol permeation. The dry proton conductor CsHSO₄ shows a high proton conductivity of ~ 10⁻³ S/cm at temperatures > 140 °C and water is not needed for proton conduction. However, it is found that CsHSO₄ decomposes to Cs₂SO₄ and H₂S at 150 °C in H₂ atmosphere in contact with the Pt/C catalyst. Thus, new catalyst materials need to be explored for CsHSO₄ to be used in practical high temperature PEMFC. Thin self-humidifying Nafion membranes with dispersed Pt/C catalyst powder are prepared and tested in PEMFC with dry H₂ and O₂. The Pt/C particles provide sites for catalytic recombination of H₂ and O₂ permeating from the anode and cathode, and the water produced at these sites directly humidifies the membrane. The performance of the cell with the self-humidifying membrane operated with dry reactants is ~ 90 % of that obtained with well humidified H₂ and O₂.text
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Wu, HungYi, and 吳宏一. "Analysis of Water Concentration and Temperature within Membrane in Proton Exchange Membrane." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/42060057775265420468.
Full textAbstract:
碩士國立臺灣大學
應用力學研究所
91
The primary concern of this thesis deals with the prediction of the water concentration distribution in the membrane of fuel cell. This model considers the thermal and water management in the PEMFC. In this work, the discussion was divided into two parts. The first part is the results about the water concentration distribution at the cathode side of the membrane being constant. The second part is the results about the water flux condition at the cathode side of the membrane. We will discuss how the temperature gradient affects the water management. First, under the conditions of fixed water concentration at the cathode side, the effect of temperature at the cathode side on the water concentration is significant. As the Tc is increased, the membrane dehydration will become less. While for the water flux condition at cathode side, the operating temperatures on the water management in the membrane are in similar manners. The effects of the anode temperature on the water management in the membrane are also examined in this thesis. It is found that the Ta has considerable impact on the water content in the membrane. In addition, this thesis also investigates the temperature distribution under different current density. The results reveal that under extremely large current density condition, the current density causes the temperature distribution in the membrane nonuniform. This results in the existence of thermal stress within the membrane and the breakdown of the membrane under extremely large current density.
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Chung, Shang-shu, and 鍾尚書. "Proton Exchange Membrane Fuel Cell Membrane Electrode Assembly Analysis and Numerical Simulation." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/18682795169208853066.
Full textAbstract:
碩士國立臺南大學
綠色能源科技研究所碩士班
98
A numerical study is performed to analyze the proton exchange membrane fuel cell membrane electrode assembly analysis and numerical simulation with an serpentine flow field. The modeling domain consists of the bipolar plates, flow channels, diffusion electrodes, and the membrane. Numerical simulation is focused on effects of the various parameters (permeability, porosity, and the operation voltage) on the performance of various mass fraction, current density- voltage (I-V) curve, power density- voltage (P-V) curve. Simulations reveal that the permeability and porosity virtually has a little effect on the PEMFC, but they will affect the flow into the hydrogen, oxygen and water , thus affecting the cell current density, current - voltage curve, power - voltage curve. Operation voltage were voltage V = 0.95, voltage V = 0.7 and the voltage V = 0.4 in three parts for discussion. The potential of the higher hydrogen mass fraction is increased; the higher mass fraction of oxygen; but the quality of water in the cathode sub-rate decreased. Permeability and porosity is already close to the micro-component model are discussed, so its impact is not pressure, temperature can obviously changed on the fuel cell performance. Although this study was to explore the single cell, hence a change in volume is very subtle, but the future needs of commercial proton exchange membrane fuel cell systems, permeability and porosity of that cost would be a major consideration.