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Rismanchian, Azadeh. "Copper Nickel Anode for Methane SOFC." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1312299949.
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Stübner, Ralph. "Untersuchungen zu den Eigenschaften der Anode der Festoxid-Brennstoffzelle (SOFC)." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2002. http://nbn-resolving.de/urn:nbn:de:swb:14-1025078611046-09161.
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This thesis investigates the electrical and electrochemical properties and the long-term stability of anodes of the solid oxide fuel cell (SOFC). A model is suggested, which describes the impedance spectra of symmetrical anode cells. According to this, the series resistance in the spectra is caused by the resistance of the electrolyte (YSZ), ohmic parts of the anodes, which are described as porous electrodes, and by the partial contacting of the anodes. A major contribution to it is provided by the nickel matrix in the anodes. The high frequency relaxation in the spectra is assigned to the transfer reaction, the low frequency to a gas diffusion inhibition along the gas supply channels. The degradation of the symmetrical anode cells, which has been observed in long-term experiments, is ascribed to a degradation of the electrolyte material, of the transfer reaction, of the nickel matrix in the anodes and of the contact resistance between the anodes and the current collecting nickel grids. The degradation rate of the last two depends on the gas composition. A model for the observed behaviour in time is presentedDiese Arbeit untersucht die elektrischen und elektrochemischen Eigenschaften und die Langzeitbeständigkeit der Anoden von Festoxid-Brennstoffzellen (SOFC). Ein Modell wird vorgestellt, mit dem die Impedanzspektren symmetrischer Anodenzellen beschrieben werden können. Demnach ist der Serienwiderstand in den Spektren verursacht durch den Widerstand des Elektrolyten (YSZ), ohmsche Anteile in den Anoden, die als poröse Elektroden beschrieben werden, und durch die partielle Kontaktierung der Anoden. Maßgebliche Beiträge liefert hier die Nickelmatrix in den Anoden. Die hochfrequente Relaxation in den Spektren wird der Durchtrittsreaktion, die niederfrequente einer Gasdiffusionshemmung entlang der Gasversorgungskanäle zugeordnet. Die in Langzeitversuchen beobachtete Degradation der symmetrischen Anondenzellen wird zurückgeführt auf eine Degradation des Elektrolytmaterials, der Durchtrittsreaktion, der Nickelmatrix in den Anoden und des Kontaktwiderstandes zwischen den Anoden und den stromabnehmenden Nickelnetzen. Die Degradation der beiden letzteren ist in ihrer Rate abhängig von der Gaszusammensetzung. Ein Modell für das beobachtete zeitliche Verhalten wird vorgestellt
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Stübner, Ralph. "Untersuchungen zu den Eigenschaften der Anode der Festoxid-Brennstoffzelle (SOFC)." Doctoral thesis, Technische Universität Dresden, 2001. https://tud.qucosa.de/id/qucosa%3A24154.
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This thesis investigates the electrical and electrochemical properties and the long-term stability of anodes of the solid oxide fuel cell (SOFC). A model is suggested, which describes the impedance spectra of symmetrical anode cells. According to this, the series resistance in the spectra is caused by the resistance of the electrolyte (YSZ), ohmic parts of the anodes, which are described as porous electrodes, and by the partial contacting of the anodes. A major contribution to it is provided by the nickel matrix in the anodes. The high frequency relaxation in the spectra is assigned to the transfer reaction, the low frequency to a gas diffusion inhibition along the gas supply channels. The degradation of the symmetrical anode cells, which has been observed in long-term experiments, is ascribed to a degradation of the electrolyte material, of the transfer reaction, of the nickel matrix in the anodes and of the contact resistance between the anodes and the current collecting nickel grids. The degradation rate of the last two depends on the gas composition. A model for the observed behaviour in time is presented.Diese Arbeit untersucht die elektrischen und elektrochemischen Eigenschaften und die Langzeitbeständigkeit der Anoden von Festoxid-Brennstoffzellen (SOFC). Ein Modell wird vorgestellt, mit dem die Impedanzspektren symmetrischer Anodenzellen beschrieben werden können. Demnach ist der Serienwiderstand in den Spektren verursacht durch den Widerstand des Elektrolyten (YSZ), ohmsche Anteile in den Anoden, die als poröse Elektroden beschrieben werden, und durch die partielle Kontaktierung der Anoden. Maßgebliche Beiträge liefert hier die Nickelmatrix in den Anoden. Die hochfrequente Relaxation in den Spektren wird der Durchtrittsreaktion, die niederfrequente einer Gasdiffusionshemmung entlang der Gasversorgungskanäle zugeordnet. Die in Langzeitversuchen beobachtete Degradation der symmetrischen Anondenzellen wird zurückgeführt auf eine Degradation des Elektrolytmaterials, der Durchtrittsreaktion, der Nickelmatrix in den Anoden und des Kontaktwiderstandes zwischen den Anoden und den stromabnehmenden Nickelnetzen. Die Degradation der beiden letzteren ist in ihrer Rate abhängig von der Gaszusammensetzung. Ein Modell für das beobachtete zeitliche Verhalten wird vorgestellt.
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O'Brien, Julie Suzanne. "Cermet Anodes for Solid Oxide Fuel Cells (SOFC) Systems Operating in Multiple Fuel Environments: Effects of Sulfur and Carbon Composition as well as Microstructure." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20634.
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A series of cermet powders of composition NixCo(1-x)O-YSZ were synthesized for testing as cermet anode materials for SOFCs. The Co is found by powder XRD to become incorporated into the crystal lattice of the NiO, thus forming a true alloyed material. SEM and EDS results show two types of particles upon sintering to 1380oC: small, amorphous particles of YSZ and large, crystalline particles of nickel.
The electrochemical oxidation of hydrogen on a cermet anode composed of Ni0.7Co0.3O-YSZ was investigated using a series of many button cells. Through EIS data, cyclic voltammetry data, the exchange current densities for these button cells were determined. Although a relatively large variation was found (expected to be due to microstructural variation) the average values for both methods of measurement is in good agreement in hydrogen.
Following reduction in pure hydrogen, the fuel was changed to a mixture with high concentration of H2S. It was found that a concentration of 10 % H2S/H2 produced a sudden change in anode microstructure and resulted in loss of exchange current density. Lowering the amount of H2S in the initial fuel feed, which allowed for a more gradual microstructural change, allowed the cell to eventually function at concentrations in excess of 10 % H2S/H2. It was determined by OCV values in various concentrations of H2S/H2 that hydrogen is the predominant fuel of choice, even if H2S is available. Following electrochemical testing, slow cooling in a 10 % H2S/H2 mixture following produced metal sulfide spheres, as determined by SEM and EDS.
Investigation in hydrocarbon, alcohol and biodiesel fuels was then undertaken to test the fuel variability of the given cermet anode material. Methane containing 10 % H2S was found to have increased exchange current density relative to poisoned hydrogen. Ethane and biodiesel experienced no increase in exchange current density, but a lengthening of the functional lifetime of the cell was observed, indicating reduced carbon poisoning. Methanol is a promising oxygen-containing SOFC fuel since it produced exchange current density values larger than hydrogen, and showed no evidence of coke formation by post-mortem SEM.
Since oxygen-containing fuels are known to decompose in the gas phase at typical SOFC operating temperatures, the performance in a mixture of various CO/H2 fuels was then investigated. The Ni0.7Co0.3O-YSZ cermet anode gave higher exchange current density values for low ratio of CO/H2 fuels in the range 20/80 and 30/70 compared to pure H2. This is the first example of a Ni-based anode providing higher performance with a CO/H2 mixed fuel than for a pure H2 fuel. Finally, continuous running of a cell with fuel ratio 25/75 CO/H2 for 7 days produced exchange current density values, which were observed to increase significantly above the values for pure H2 during days 1-4 followed by deterioration below the value for hydrogen on subsequent days.
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Lay, Elisa. "Nouveaux matériaux d'électrode de cellule SOFC." Phd thesis, Université Joseph Fourier (Grenoble), 2009. http://tel.archives-ouvertes.fr/tel-00461152.
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Ce travail est consacré à l'étude des influences de deux cations, le cérium et le baryum, sur les propriétés structurales, physico-chimiques, électriques et électrochimiques de l'oxyde (La,Sr)(Cr,Mn)O3 (LSCM). L'effet de l'état d'oxydation du cérium a été déterminé en substituant les sites A de LSCM et d'un oxyde de composition proche, CexSr1-xCr0,5Mn0,5O3 (CeSCM). L'influence des propriétés de basicité du baryum a été examinée. Les matériaux sont stables en conditions de fonctionnement d'anode pour SOFC. La conductivité est de type p pour CeLSCM et CeSCM. Les composés LBCM sont des semi-conducteurs de type n pour des pressions partielles comprises entre 1 et 10-4 atm, et de type p pour des pressions plus faibles. Sous atmosphère neutre, la conductivité électrique totale augmente avec la teneur en cérium dans LSCM, et la conductivité des matériaux CeSCM est similaire à celle de CeLSCM substitué par 25% de cérium (36 S.cm-1 à 900 °C). Sous atmosphère réductrice, la conductivité des matériaux CeLSCM est de l'ordre de 1 S.cm-1. La quantité de baryum n'a pas d'influence sur la conductivité de LSBCM. La caractérisation d'électrodes ponctuelles denses a permis de montrer que les performances anodiques augmentent avec la teneur en cérium substitué au lanthane dans LSCM. La nature des processus impliqués n'est pas modifiée lorsque le strontium est substitué par le cérium, même si l'absence de lanthane pénalise le comportement anodique. Des performances intéressantes pour une application comme matériau d'anode pour SOFC ont été atteintes pour le composé La0,75Ba0,25Cr0,5Mn0,5O3. Les origines des contributions élémentaires des caractéristiques d'électrode sont discutées.
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Ihringer, Raphaël. "Electrolytes minces sur supports anode dans les piles à combustible SOFC /." [S.l.] : [s.n.], 2001. http://library.epfl.ch/theses/?nr=2307.
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Yin, Wenbin. "Reaction Mechanism of Carbon and Methane on the Anode of SOFC." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398778152.
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Agbede, Oluseye Omotoso. "Study of oxygen dissolution in molten tin : a novel SOFC anode." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24757.
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Conventional power plants for the conversion of fossil fuels to electricity have low efficiencies and produce large amount of carbon dioxide, a greenhouse gas, which contribute to climate change. Hence, a molten tin reformer and methane-fuelled SOFC with molten tin anode (Sn(l)-SOFC) for easier CO2 capture and higher power efficiency were investigated. Both systems involved oxygen dissolution in molten tin and methane reaction with the dissolved oxygen, as well as gas bubbling, so oxygen dissolution and methane reaction at bubble | molten tin interface were investigated. Oxygen was separated successfully from a 10%O2-He blend through gas bubbling and dissolution in molten tin which suggests that oxygen may be separated from air in the molten tin reformer by bubbling air through molten tin in the first stage of the periodic process. An LSM-YSZ/LSM double-layered reference electrode and YSZ electrolyte potentiometric oxygen sensor was used to measure the concentration of dissolved oxygen in molten tin; hence, enabling derivation of the solubility limit and Gibbs energy change for the formation of SnO which was in equilibrium with oxygen at the solubility limit. The solubility of oxygen in molten tin in equilibrium with SnO in the temperature range 973-1123 K was ca. 0.019-0.107 atom%. The rate of oxygen dissolution in molten tin when 10%O2-He blend was bubbled through it was controlled by chemical reaction at the bubble | molten tin interface; the mechanism involved a first step of chemisorption to molten tin at the bubble | molten tin interface, forming SnO as the absorbed intermediate. The second step of the mechanism involved the dissociation of SnO to molten tin and oxygen atom incorporated in the molten tin. The rate limiting step was the dissociation of SnO into molten tin and oxygen atom. Likewise, the rate of deoxygenation of molten tin by 10%CH4-He was not limited by the diffusion of oxygen atoms in the molten tin but might be limited by surface reaction at the bubble | molten tin interface. The performance of the molten tin reformer and methane-fuelled Sn(l)-SOFC depends on bubble size and behaviour, so bubbles generated in molten tin were characterized by determining the sizes, shape, velocities, and behaviour under different operating conditions of nozzle diameter, gas flow rates and temperatures. A pressure pulse technique which incorporates a differential pressure transducer was employed successfully in the measurement of frequencies of bubble formation in molten tin at high temperatures in the range 973-1173 K while the bubbles were approximated as oblate spheroids which wobbled. LSM cathodes were deposited on micro-tubular YSZ electrolytes and the microstructures and electrical conductivities characterized by scanning electron microscopy (SEM) and four-point probe resistance measurement, respectively. SEM micrographs showed the densification of LSM cathodes with increased sintering temperature, which resulted in increased electrical conductivities. Potential difference-current density data and impedance spectra were determined for a methane-fuelled SOFC with molten tin anode. A peak power density of about 100 W m-2 at a current density of 222 A m-2 and potential difference of 0.45 V was obtained for the methane-fuelled SOFC with molten tin anode at 850 oC. Impedance spectra showed that ohmic potential losses controlled the reactor performance, with about half of those arising from the inherent difficulty in achieving a low resistance contact at the (Ag wire) Ag wool current collector | LSM cathode interface.
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Fisher, James C. II. "A Novel Fuel Cell Anode Catalyst, Perovskite LSCF: Compared in a Fuel Cell Anode and Tubular Reactor." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1152215855.
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Fouquet, Daniel. "Einsatz von Kohlenwasserstoffen in der Hochtemperatur-Bennstoffzelle SOFC." Aachen Wiss.-Verl. Mainz, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2707906&prov=M&dok_var=1&dok_ext=htm.
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Geagea, Maya. "Nouvelles architectures de surfaces d’échanges de piles à combustible de type SOFC pour l’amélioration de l’efficacité électrochimique." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM046/document.
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Le présent travail souhaite explorer théoriquement et expérimentalement de quelle manière l’augmentation des surfaces d’échange par l’architecturation mésoscopique des interfaces électrode/électrolyte dans une SOFC à anode support pourrait améliorer ses performances. D’abord, une optimisation des caractéristiques microstructurales de l’anode a été effectuée par ajustement de la composition initiale de la barbotine, favorisation de la percolation du réseau de Ni par une microstructure « hiérarchique » et des mesures de perméabilités aux gaz identifiant le choix de l’anode. Ensuite, un modèle électrochimique a montré une augmentation des courants d’échange par rapport à la surface plane dans le cas d’un motif périodique pour une épaisseur d’électrolyte sensiblement plus petite que les dimensions du motif. Ce dernier doit présenter des singularités concaves et convexes de façon à confiner le matériau d’électrode au voisinage de l’interface, ainsi que des caractéristiques géométriques réduisant la surtension de concentration. De telles architectures ont été réalisées, par des techniques de mise en forme des céramiques, sur des anodes auto-supportées (YSZ + Ni) sur lesquelles une couche mince d’électrolyte (YSZ) a été déposée, puis l’ensemble co-fritté. Pour finaliser la cellule, une barrière de diffusion (CGO) et une cathode bicouche (LSCF48 + CGO / LSCF48) ont ensuite été déposées puis frittées. Les premiers résultats électriques et électrochimiques montrent une augmentation de la densité de courant de130 à 300 mA.cm-2 à une tension d’opération de 0,7 V, qui reste plus élevée que ce que prévoyait la modélisation. Les résultats sont discutés ici en termes de géométrie du motif et de son évolution au cours du frittage, ainsi que des surtensions d’activation et de concentrationThe present work aims to explore, theoretically and experimentally, how the increase of exchange surfaces via the mesoscopic scale corrugation of electrode / electrolyte interfaces in an anode-supported SOFC could improve its performance. First, an optimization of the microstructural characteristics of the anode was performed by adjusting the initial composition of the slurry, favoring the percolation of the network of Ni by a "hierarchical" microstructure and gas permeability measurements identifying the choice of the anode. Next, an electrochemical model showed an increase in the exchange currents with respect to the planar surface in the case of a periodic pattern for an electrolyte thickness substantially smaller than the dimensions of the pattern. The latter must have concave and convex singularities so as to confine the electrode material in the vicinity of the interface, as well as geometrical characteristics reducing the concentration overvoltage. Such architectures have been carried out by ceramic shaping techniques on self-supported anodes (YSZ + Ni) on which a thin layer of electrolyte (YSZ) has been deposited, and then the co-sintered along with the anode. To finalize the cell, a diffusion barrier (CGO) and a bi-layered cathode (LSCF48 + CGO / LSCF48) were then deposited and then sintered. The first electrical and electrochemical results show an increase in the current density from 130 to 300 mA.cm-2 at an operating voltage of 0.7V, which is still higher than what was anticipated by modeling, reaching more than the double of the value for flat interfaces. The results are discussed here in terms of geometry of the pattern and its evolution during sintering, as well as activation and concentration overvoltages
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Mirzababaei, Jelvehnaz. "LSCF Synthesis and Syngas Reactivity over LSCF-modified Ni/YSZ Anode." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1312225644.
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Soltanzadeh, Marjan. "Modeling Triple Phase Boundary (TPB) in Solid Oxide Fuel Cell (SOFC) Anode." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28843.
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The idea of having the triple phase boundary (TPB) is extensively used in the fuel cell literature, especially with respect to solid oxide fuel cells (SOFC). The TPB concept indicates that the hydrogen oxidation reaction and the oxygen reduction reaction, which produce electric current, can actually occur at special sites, called "triple phase boundaries" where the gaseous fuel phase, ion conducting phase: electrolyte, and electron conducting phase, come into contact. Recent study shows that despite the common assumption about TPB, it is not just a point, but a zone that consists of two lines. The kinetic reaction often introduces a significant limitation to fuel cell performance. Therefore, understanding, characterizing, and optimizing the TPB content in fuel cells provides excellent opportunities for performance improvement.
Studying the kinetics of the reaction that takes place at the triple phase boundary is one aspect of this paper. It includes the study of all kinds of chemical and electrochemical reactions as well as their reaction rates, the surface species, and the electrochemical parameters, such as reaction rate constants and conductivity. A mathematical model is developed to describe a simplified anodic solid oxide fuel cell (SOFC) system, Ni/ H2--H 2O/YSZ, and its reaction occurring in the vicinity of the triple phase boundary (TPB).
The model incorporates coupled diffusion, migration and reaction phenomena of the chemical components in the gas phase, Ni particle and zirconia solid state. The kinetic constants necessary for the simulations are estimated on the basis of literature data.
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Monteiro, Natalia Kondo. "Síntese e caracterização de manganita-cromita de lantânio dopada com rutênio para anodos de células a combustível de óxidos sólidos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-18112011-160321/.
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Diversos anodos para célula a combustível de óxido sólido (SOFC) têm sido estudados devido aos problemas de deterioração dos anodos tradicionalmente usados, os compósitos à base de zircônia estabilizada/Ni (YSZ/Ni). Estudos prévios evidenciaram que a perovskita La0,75Sr0,25Cr0,50Mn0,50O3 (LSCM) possui desempenho similar em SOFCs usando hidrogênio e metano como combustível, tornando essa cerâmica um possível substituto dos compósitos à base de níquel. No presente estudo, foram sintetizados compostos La0,75Sr0,25Cr0,50-xMn0,50- yRux,yO3 (LSCM-Ru) pelo método dos precursores poliméricos. Análises termogravimétrica e térmica diferencial (TG/ATD) simultâneas e difração de raios X (DRX) foram utilizadas para monitorar a evolução térmica das resinas precursoras e a formação de fase dos compostos. As propriedades elétricas de amostras sinterizadas foram estudadas pela técnica de 4 pontas de prova dc na faixa de temperatura entre 25 °C e 800 °C. Os resultados experimentais indicaram a formação de fase única dos compostos LSCM-Ru calcinados a ~1200 °C. Os parâmetros de rede, calculados a partir dos dados de DRX, revelaram que a substituição parcial dos íons Cr ou Mn pelo Ru não altera significativamente a estrutura cristalina do LSCM até x,y ~ 0,10; uma característica consistente com os raios iônicos similares dos cátions Cr, Mn e Ru com número de coordenação seis. Medidas de resistividade elétrica ao ar mostraram que o mecanismo de transporte não é alterado e que o efeito da substituição de Ru nas propriedades elétricas do composto depende do íon substituído (Cr ou Mn) de maneira consistente com suas substituições parciais. Os testes de SOFCs unitárias revelaram que células com os anodos constituídos por uma camada coletora de corrente do anodo cerâmico LSCM-Ru e uma camada funcional de YSZ/Ni têm desempenho superior a células contendo apenas o anodo cerâmico. As células contendo os anodos cerâmicos LSCM-Ru foram testadas em hidrogênio e etanol, entre 800 °C e 950 °C, e mostraram desempenho em etanol superior ao em hidrogênio; uma característica que foi associada às propriedades de transporte eletrônico dos compostos LSCM-Ru em atmosfera redutora. Os resultados sugerem que os compostos LSCM com substituição parcial de Ru são anodos promissores para SOFC operando com etanol.Several anodes for solid oxide fuel cell (SOFC) have been studied because of serious degradation exhibited by the traditionally used yttria-stabilized zirconia/Ni cermets (YSZ/Ni). Previous studies showed that the perovskite La0.75Sr0.25Cr0.50Mn0.50O3 (LSCM) has similar performance in SOFCs running on hydrogen and methane fuels, making such a ceramic a potential alternative to YSZ/Ni cermets. In the present study, compounds La0.75Sr0.25Cr0.50- xMn0.50-yRux,yO3 (LSCM-Ru) were synthesized by the polymeric precursor method. Simultaneous thermogravimetric and differential thermal analysis (TG/DTA) and X-ray diffraction (XRD) were used to monitor the thermal evolution of the precursor resins and the formation of crystalline phases. The electrical properties of sintered samples were studied by the 4-probe dc technique in the temperature range between 25 °C and 800 °C with controlled atmosphere. The experimental results showed the formation of single phase LSCM-Ru compounds after heat treatment at ~ 1200 °C. Lattice parameters, calculated from the XRD data, revealed that the partial substitution of Cr or Mn by Ru has no significant effect on the crystal structure of LSCM up to Ru x,y ~ 0.10; in agreement with the similar ionic radius of Cr, Mn and Ru with coordination number six. Electrical resistivity measurements showed that the transport mechanism is unchanged and that the effect of Ru addition on the electrical properties of the compound depends on the substituted ion (Cr or Mn). Electrochemical tests of SOFCs demonstrated that single cells comprised of a current collector layer of LSCM-Ru ceramic anode and a functional layer for YSZ/Ni have superior performance when compared to single cells with only one layer of the ceramic anode. Single cells with the LSCM-Ru ceramic anode layer were tested under both hydrogen and ethanol fuels, in the 800 °C - 950 °C temperature range. The main results showed that the single fuel cells exhibited higher performance under ethanol than under hydrogen; a feature that was related to the enhanced electronic transport properties of LSCM-Ru in reducing atmosphere. The experimental results suggest that the LSCM-Ru compounds are promising anodes for ethanol fueled SOFCs.
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Choi, Hyunkyu. "Perovskite-type oxide material as electro-catalysts for solid oxide fuel cells." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354652812.
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Lee, Tae Jung. "Characterisation of anode supported microtubular SOFC process on pure methane reduction and operation." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/592/.
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The optimisations of reduction and operation of Ni-YSZ anode supported micro tubular cells on pure methane were studied. A major problem of SOFCs is nickel anode performance on methane and higher hydrocarbons. The aim of this work was to study the effect of reduction and operation of anode-supported microtubular SOFCs using methane as both reductant and fuel. The results were compared to those from optimised operation using hydrogen. To measure mechanical strength, the three point bending test was employed. Temperature programmed oxidation (TPO) results were investigated to measure the carbon deposition on the anode in order to assess potential damage to the cermet catalyst. Also field emission scanning electron microscope (FE-SEM) and Energy-Dispersive X-ray spectroscopy EDS results were analysed on the anode surface.
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Mai, Thi Hai Ha. "Effet de H2S sur la structure et les performances électriques d’une anode SOFC." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI003/document.
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Une SOFC peut être alimentée en biogaz sans reformage préliminaire du fait de sa température de fonctionnement élevée. Cependant, la présence de polluants comme le soufre peut empoisonner les électrodes. Cette thèse se concentre sur la compréhension des effets de H2S sur la structure de l'anode et les performances électriques. Spectroscopie Raman, imagerie optique et spectroscopie d'impédance ont été utilisées in situ pour évaluer la cinétique de sulfuration et les modifications morphologiques de Ni et Ni-CGO en présence de H2S à différentes températures. Les performances électriques de Ni-YSZ/YSZ/Pt ont été mesurées à 500°C à l'abandon et sous polarisation (500 mV). Un circuit électrique avec une impédance de concentration du second ordre est proposé. Les caractéristiques de l'anode avec combustibles propre et pollué sont discutées à partir des formes et des décompositions des spectres. Les corrélations entre propriétés électriques et accumulation de sulfure de nickel sont présentéesA Solid Oxide Fuel Cell (SOFC) can be fed with biogas without a preliminary reforming due to its high operating temperature. However, the biogas contains numerous pollutants like sulfur which poison the electrodes. This thesis focuses on the understanding of the H2S impacts on the anode structure and electrical performances. Raman Spectroscopy, optical imagery and Impedance Spectroscopy have been used in situ to evaluate the sulfidation kinetics and the morphological changes of Ni and Ni-CGO pellets exposed to H2S at various temperatures. The electrical performances of Ni-YSZ/YSZ/Pt cells under open circuit and 500 mV-polarizing conditions at 500°C have been measured. An electrical circuit with a second-order concentration impedance is proposed. The anode behaviors in clean and polluted fuel are discussed based on the evolutions of impedance shapes and on the fitted parameters. Correlations between the electrical properties and the build-up of nickel sulfide are presented
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Becker, Benjamin Paul. "Patterned nickel anode stability in SOFC environments with H2, CO and CH4 fuel feeds." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2902.
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Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Penwell, William. "Doped Perovskite Materials for Solid Oxide Fuel Cell (SOFC) Anodes and Electrochemical Oxygen Sensors." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30695.
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This work focused on the study of three independent projects involving perovskite oxide materials and their applications as solid oxide fuel cell (SOFC) anodes and electrochemical oxygen sensors. The underlying theme is the versatility and tune-ability of the perovskite structure. Reactivity and conductivity (ionic as well as electronic) are modified to optimize performance in a specific application.
The effect of Ce doping on the structure and the conductivity of BaFeO3 perovskite materials is investigated and the resulting materials are applied as oxygen sensors. The new perovskite family, Ba1-xCexFeO3-δ (x=0, 0.01, 0.03, and 0.05), was prepared via a sol-gel method. Powder XRD indicates a hexagonal structure for BaFeO3 with a change to a cubic perovskite upon Cerium doping at the A site. The solubility limit of Ce at the A site was experimentally determined to be between 5-7 mol %. Bulk, electronic and ionic conductivities of BaFeO3-δ and Ba0.95Ce0.05FeO3-δ were measured in air at temperatures up to 1000˚C. Cerium doping increases the conductivity throughout the entire temperature range with a more pronounced effect at higher temperatures. At 800˚C the conductivity of Ba0.95Ce.05FeO3-δ reaches 3.3 S/cm. Pellets of Ba0.95Ce.05FeO3-δ were tested as gas sensors at 500 and 700˚C and show a linear, reproducible response to O2.
Promising perovskite anodes have been tested in high sulfur fuel feeds. A series of perovskite solid oxide fuel cell (SOFC) anode materials: Sm0.95Ce0.05FeO3-δ, Sm0.95Ce0.05Fe0.97Ni0.03O3-δ and Sm0.95Ce0.05Fe0.97Co0.03O3-δ have been tested for sulfur tolerance at 500°C. The introduction of the extreme 5% H2S enhances the performance of these anodes, verified by EIS and CA experiments. Post mortem analyses indicate that the performance
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enhancement arises from the partial sulfidation of the anode, leading to the formation of FeS2, Sm3S4 and S on the perovskite surface. Testing in lower concentrations of sulfur, more common in sour fuels, 0.5% H2S, also enhances the performance of these materials. The SCF-Co anode shows promising stability and an increase in exchange current density, io, from 13.72 to 127.02 mA/cm2 when switching from H2 to 0.5% H2S/99.5% H2 fuel composition. Recovery tests performed on the SCF-Co anode conclude that the open cell voltage (OCV) and power density of these cells recover within 4 hours of H2S removal. We conclude that the formation of metal sulfide species is only partially reversible, yielding an anode material with an overall lower Rct upon switching back to pure H2. Combining their performance in sulfur containing fuels with their previously reported coke tolerance makes these perovskites especially attractive as low temperature SOFC anodes in sour fuels.
A new perovskite family Ba1-xYxMoO3 (x=0-0.05) has been investigated in regards to electrical conductivity and performance as IT-SOFC anode materials for the oxidation of H2. Refinement of p-XRD spectra as well as SEM imaging conclude that the solubility limit of Y doping at the A site is 5 mol%, beyond which Y2O3 segregation occurs. The undoped BaMoO3 sample has a colossal room temperature conductivity of 2500 S/cm in dry H2. All materials maintain metallic conductivity in the temperature range of 25-1000°C with resistance increasing with Y doping. The Ba1-xYxMoO3 (x=0, 0.05) materials exhibit good performance as SOFC anode materials between 500-800°C, with Rct values at 500°C in dry H2 of 3.15 and 6.33 ohm*cm2 respectively. The catalytic performance of these perovskite anodes is directly related to electronic conductivity, as concluded from composite anode performance.
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Seo, Haewon. "Mesoscale structural modification for anode-supported solid oxide fuel cell：Effects of corrugated structures fabricated through microextrusion printing." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263653.
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Siengchum, Tritti. "Electrochemical Oxidation of Methane on Ni-Doped Perovskite Anode Solid Oxide Fuel Cell." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1248205545.
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Roudeau, Sabine. "Nouveaux matériaux d'anodes pour pile à combustible SOFC fonctionnant à 700 °C." Bordeaux 1, 2008. http://www.theses.fr/2008BOR13588.
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Sauvet, Anne-Laure. "Etude de nouveaux matériaux d'anode pour pile à combustible à oxyde solide (SOFC) fonctionnant sous méthane." Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10096.
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Arakaki, Alexander Rodrigo. "Estudos de síntese e processamento de compósitos de óxido de níquel-céria dopada utilizados como anodo de células a combustível de óxido sólido de temperatura intermediária (IT-SOFC)." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-27102014-134125/.
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Este trabalho compreendeu os estudos de síntese química de pós por via úmida, de processamento cerâmico e de redução do óxido de níquel contido nos compósitos de céria dopada com samária e gadolínia, aplicados, principalmente, como anodos de Células a Combustível de Óxido Sólido. A rota adotada para a preparação dos pós com composição Ce0,8(SmGd)0,2O1,9/NiO e proporção em massa de 40 : 60% foi a coprecipitação de hidróxidos associada ao tratamento solvotérmico, utilizando-se como matérias-primas cloretos de cério, níquel, samário e gadolínio. O surfactante aniônico brometo de cetil trimetil amônio (CTAB) também foi utilizado na etapa de precipitação na relação molar Metal / CTAB entre 1 e 3. A influência do solvente orgânico utilizado no tratamento solvotérmico dos pós foi analisada utilizando o etanol, propanol e o butanol, nas condições de temperatura de 150ºC por 16 h, com e sem calcinação a 600ºC por 1h, e moagem em moinho de bolas. As amostras compactadas foram sinterizadas em temperaturas entre 1200 e 1400ºC por 1h. A redução in situ do NiO-SGDC foi estudada na amostra cerâmica preparada nas seguintes condições: síntese por coprecipitação usando ou não o CTAB, tratamento solvotérmico em butanol, calcinação a 600ºC, prensagem e sinterização a 1350ºC por 1h. O processo de redução das amostras sintetizadas em butanol foi avaliado em forno tubular em atmosfera dinâmica de 4%H2/Ar, fixando-se a temperatura a 900°C e variando-se o tempo entre 10 e 120 minutos. A redução também foi relizada nos compósitos sintetizados utilizando o CTAB na proporção Metal/CTAB = 2, tratados termicamente em etanol e butanol, após calcinação, prensagem e sinterização em forno tubular sob atmosfera de H2/Ar em isotermas de 700, 800 e 900°C por períodos entre 2 e 240 minutos. Os pós, as cerâmicas e os compósitos sintetizados em laboratório foram comparados com os materiais compósitos produzidos com pós de origem comercial. A caracterização dos pós foi realizada por difração de raios X (DRX), microscopia eletrônica de varredura (MEV), área de superfície específica por adsorção gasosa de nitrogênio (BET), análise térmica (TG/DTA) e distribuição granulométrica por espalhamento de feixe laser (Cilas). As cerâmicas foram analisadas por microscopia eletrônica de varredura, DRX e medidas de densidade pela técnica de imersão em água (método de Arquimedes). As cerâmicas e os compósitos foram caracterizados eletricamente por medidas de resistência elétrica pelo método de quatro pontas DC. Os resultados mostraram que os pós sem calcinação apresentaram as estruturas cristalinas características da céria e do hidróxido de níquel, e elevada área de superfície específica (80 m2/g). As cerâmicas provenientes dos pós tratados com etanol e propanol apresentaram boa homogeneidade química, estrutural e valores de densidade de 99% em relação a densidade teórica. Verificou-se que 80 a 90% do NiO é reduzido e as porosidades atingidas pelos compósitos são da ordem de 30%. A caracterização elétrica mostrou que a condutividade iônica da fase cerâmica do anodo, sintetizado solvotermicamente em butanol, possui valor de 0,03S.cm-1 na temperatura de 600°C, valor superior aos encontrados na literatura. A caracterização elétrica dos compósitos reduzidos revelou alta condutividade elétrica característica do níquel metálico, indicando percolação adequada da fase de níquel e distribuição homogênea de ambas fases cerâmica e metálica. As rotas de síntese e os materiais estudados são, portanto, adequados para a aplicação como anodo das IT-SOFCs.This work comprises studies of powder chemical synthesis by wet route, ceramic processing and reduction of nickel oxide added to samaria and gadolinia doped ceria ceramic composite, mainly applied as Solid Oxide Fuel Cells anode. The route adopted for the powders preparation with composition Ce0.8(SmGd)0.2O1.9/NiO and mass ratio of 40:60% was hydroxides coprecipitation and solvothermal treatment, using as start materials the cerium, nickel, samarium and gadolinium chlorides. The anionic surfactant cetyltrimethylammonium bromide (CTAB) was also used in the precipitation stage with the molar ratio Metal/CTAB ranging between 1 and 3. The influence of organic solvent used in the powders solvothermal treatment was analyzed by using ethanol, propanol and butanol at temperature of 150°C for 16h, with and without calcination at 600°C for 1h, and grinding in a ball mill. The compacted samples were sintered at temperatures between 1200 and 1400°C for 1h. The in situ reduction of NiO-SGDC was studied in the samples synthesized by coprecipitation using CTAB and without it, followed by solvothermal treatment in butanol, calcined at 600°C, pressed and sintered at 1350°C for 1h. The reduction procedure was evaluated in a tubular oven and atmosphere of 4% H2/Ar, setting the temperature at 900°C and time range between 10 and 120 minutes. The composites synthesized using the CTAB in the proportion of Metal/CTAB = 2, followed by solvothermal treatment in ethanol and butanol, after calcining, compaction and sintering, was also reduced in a tubular oven and atmosphere of 4% H2/Ar, setting the temperature at 700, 800 and 900°C and time range between 2 and 240 minutes. The powders, ceramics and the sinterized cermets syntesized in laboratory were compared to the materials produced with comercial powders. The powders characterization was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area by nitrogen gas adsorption (BET), thermal analysis (TG / DTA) and particle size distribution by scattering beam laser (Cilas). Ceramics were analyzed by scanning electron microscopy (SEM), XRD and density measurements by the technique of immersion in water (Archimedes method). The ceramics and cermets condutivity was characterized by the four probe DC method. The results obtained showed that the powders without calcination presented the crystal structures characteristics of ceria and nickel hydroxide, and high specific surface area (80m2/g) . The ceramic prepared from powders treated with ethanol and propanol had a high chemical and structural homogeneity and density values corresponding to 99% of the theoretical density. It was found that 80 to 90 % of NiO is reduced and the porosity of the composite reached about of 30 %. The anode ceramic phase synthesized solvothermically in butanol presented electrical conductivity of 0.03S.cm-1 at 600°C, higher than found at literature. The reduced cermets electrical characterization showed high electrical conductivity feature of metallic nickel, indicating the nickel phase good percolation and homogeneous distribution of both ceramic and metallic phases. Considering all these results, the synthesis routes and studied materials are suitable for use as the anode IT- SOFCs.
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Sarda, Venkatesh Verfasser], Lorenz [Akademischer Betreuer] Singheiser, and Werner [Akademischer Betreuer] [Lehnert. "Degradation phenomena in the anode side of solid oxide fuel cell (SOFC) stacks / Venkatesh Sarda ; Lorenz Singheiser, Werner Lehnert." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1156924243/34.
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Sun, Shichen. "Electrochemical Behaviors of the Electrodes for Proton Conducting Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC)." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3915.
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Proton conducting intermediate temperature (600oC-400oC) solid oxide fuel cells (IT-SOFC) have many potential advantages for clean and efficient power generation from readily available hydrocarbon fuels. However, it still has many unsolved problems, especially on the anode where the fuel got oxidized and the cathode where oxygen got reduced. In this study, for the anode, the effects of hydrogen sulfite (H2S) and carbon dioxide (CO2) as fuel contaminants were studied on the nickel (Ni) based cermet anode of proton conducting IT-SOFC using proton conducting electrolyte of BaZr0.1Ce0.7Y0.1Yb0.1O3 (BZCYYb). Both low-ppm level H2S and low-percentage level CO2 caused similar poisoning effects on the anode reaction. The H2S poisoning effect was also found to be much less than on oxide-ion conducting SOFC, which is attributed to the absence of water evolution for the anode reaction in proton conducting SOFC. In addition, the H2S/CO2 poisoning mechanisms were investigated using X-ray diffraction, energy dispersive spectroscopy (EDS), Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). For H2S, other than possible sulfur dissolution into BZCYYb, no bulk reaction was found, suggesting sulfur adsorption contributes to the reduced performance. For CO2, reaction with BZCYYb to form BaCO3 and CeO2 is identified and is believed to be the reason for the sudden worsening in CO2 poisoning as temperature drops below ~550oC. For the cathode, several representative SOFC cathodes including silver (Ag), La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), LSCF-BZCYYb composite, and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) were evaluated based on BZCYYb electrolyte. LSCF give similar high interfacial resistance as Ag, while LSCF-BZCYYb composite cathode shows lower interfacial resistance, suggesting LSCF behaves like pure electronic conductor cathode in this case. For BSCF, it shows smallest interfacial resistance and the charge transfer process appears to accelerate with the introduction of H2O, while oxygen adsorption/transport seem to slow down due to adsorbed H2O. Furthermore, CO2 was shown to cause poisoning on the BSCF cathode, yet the poisoning was significantly reduced with the co-presence of water. The results suggest that although BSCF seem to display mixed proton-electronic conduction, its strong affinity to H2O may inhibit the oxygen reduction reaction on the cathode and new cathode materials still need to be designed.
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Cella, Beatriz. "S?ntese e caracteriza??o de NiO-CGO para anodo e eletr?litos s?lidos e base de C?ria para SOFC." Universidade Federal do Rio Grande do Norte, 2009. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12682.
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Previous issue date: 2009-01-04The direct use of natural gas makes the Solid Oxide Fuel Cell (SOFC) potentially more competitive with the current energy conversions technologies. The Intermediate Temperature SOFC (IT-SOFC) offer several advantages over the High Temperature SOFC (HT-SOFC), which includes better thermal compatibility among components, fast start with lower energy consumption, manufacture and operation cost reduction. The CeO2 based materials are alternatives to the Yttria Stabilized Zirconia (YSZ) to application in SOFC, as they have higher ionic conductivity and less ohmic losses comparing to YSZ, and they can operate at lower temperatures (500-800?C). Ceria has been doped with a variety of cations, although, the Gd3+ has the ionic radius closest to the ideal one to form solid solution. These electrolytes based in ceria require special electrodes with a higher performance and chemical and termomechanical compatibility. In this work compounds of gadolinia-doped ceria, Ce1-xGdxO2-δ (x = 0,1; 0,2 and 0,3), used as electrolytes, were synthesized by polymeric precursors method, Pechini, as well as the composite material NiO - Ce0,9Gd0,1O1,95, used as anode, also attained by oxide mixture method, mixturing the powders of the both phases calcinated already. The materials were characterized by X ray diffraction, dilatometry and scanning electronic microscopy. The refinement of the diffraction data indicated that all the Ce1-xGdxO2-δ powders were crystallized in a unique cubic phase with fluorite structure, and the composite synthesized by Pechini method produced smaller crystallite size in comparison with the same material attained by oxide mixture method. All the produced powders had nanometric characteristics. The composite produced by Pechini method has microstructural characteristics that can increase the triple phase boundaries (TPB) in the anode, improving the cell efficiency, as well as reducing the mass transport mechanism effect that provokes anode degradation
A utiliza??o direta do g?s natural torna a c?lula a combust?vel de ?xido s?lido (SOFC) potencialmente mais competitiva com as atuais tecnologias para convers?o de energia. A SOFC de temperatura intermedi?ria (IT-SOFC) oferece muitas vantagens sobre a SOFC de alta temperatura (HT-SOFC), que incluem melhor compatibilidade t?rmica entre os componentes, partida r?pida com menos consumo energ?tico, redu??o de custos de obten??o e opera??o. Os materiais baseados em CeO2 s?o alternativas aos eletr?litos de zirc?nia estabilizada com ?tria (YSZ) para aplica??es em SOFC, pois t?m condutividade i?nica maior e menores perdas ?hmicas em compara??o a YSZ, e podem operar a temperaturas mais baixas (500-800?C). C?ria tem sido dopada com uma variedade de c?tions, entretanto, o Gd3+ possui o raio i?nico mais pr?ximo do ideal para forma??o da solu??o s?lida. Esses eletr?litos baseados em c?rio requerem eletrodos especiais com um alto desempenho e compatibilidade termomec?nica e qu?mica. Neste trabalho compostos c?ria dopada com gadol?nia, Ce1-xGdxO2-δ (x = 0,1; 0,2 e 0,3), utilizadas como eletr?litos, foram sintetizados a partir do m?todo dos precursores polim?ricos, Pechini, assim como o material comp?sito NiO - Ce0,9Gd0,1O1,95, usado para anodo, obtido tamb?m pelo m?todo de mistura dos ?xidos, p?s das duas fases j? calcinadas. Os materiais foram caracterizados atrav?s das t?cnicas de difra??o de raios X, dilatometria e microscopia eletr?nica de varredura. O refinamento dos dados obtidos pela difra??o de raios X indicou que todos os p?s de Ce1-xGdxO2-δ cristalizaram em uma ?nica fase c?bica com estrutura fluorita, e que o comp?sito obtido por Pechini produziu menores tamanhos de cristalitos das fases em compara??o com o p? sintetizado por mistura de ?xidos em uma mesma temperatura de calcina??o. Todos os p?s obtidos t?m caracter?sticas nanom?tricas. O comp?sito obtido por Pechini possui caracter?sticas microestruturais que podem aumentar a fronteira de fase tripla (TPB) dentro do anodo, melhorando a efici?ncia da c?lula, assim como reduzir o efeito do mecanismo de transporte de massa que provoca degrada??o do anodo
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Lu, Lanying. "Studies of anode supported solid oxide fuel cells (SOFCs) based on La- and Ca-Doped SrTiO₃." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/7068.
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Solid oxide fuel cells (SOFCs) have attracted much interest as the most efficient electrochemical device to directly convert chemical energy to usable electrical energy. The porous Ni-YSZ anode known as the state-of-the-art cermet anode material is found to show serious degradation when using hydrocarbon as fuel due to carbon deposition, sulphur poisoning, and nickel sintering. In order to overcome these problems, doped strontium titanate has been investigated as a potential anode material due to its high electronic conductivity and stability in reducing atmosphere. In this work, A-site deficient strontium titanate co-doped with lanthanum and calcium, La₀.₂Sr₀.₂₅Ca₀.₄₅TiO₃ (LSCT[sub](A-)), was examined. Flat multilayer ceramics have been produced using the aqueous tape casting technique by controlling the sintering behaviour of LSCT[sub](A-), resulting in a 450µm thick porous LSCT[sub](A-) scaffold with a well adhered 40µm dense YSZ electrolyte. Impregnation of CeO₂ and Ni results in a maximum power density of 0.96Wcm⁻² at 800°C, higher than those of without impregnation (0.124Wcm⁻²) and with impregnation of Ni alone (0.37Wcm⁻²). The addition of catalysts into LSCT[sub](A-) anode significantly reduces the polarization resistance of the cells, suggesting an insufficient electrocatalytic activity of the LSCT[sub](A-) backbone for hydrogen oxidation, but LSCT[sub](A-) can provide the electronic conductivity required for anode. Later, the cells with the configuration of LSCT[sub](A-)/YSZ/LSCF-YSZ were prepared by the organic tape casting and impregnation techniques with only 300-m thick anode as support. The effects of metallic catalysts in the anode supports on the initial performance and stability in humidified hydrogen were discussed. The nickel and iron impregnated LSCT[sub](A-) cell exhibits a maximum powder density of 272mW/cm² at 700°C, much larger than 43mW/cm² for the cell without impregnation and 112mW/cm² for the cell with nickel impregnation. Simultaneously, the bimetal Ni-Fe impregnates have significantly reduced the degradation rates in humidified hydrogen (3% H₂O) at 700°C. The enhancement from impregnation of the bi-metal can possibly be the result of the presence of ionic conducting Wustite Fe₁₋ₓO that resides underneath the Ni-Fe metallic particles and better microstructure. Third, in order to improve the ionic conductivity of the anode support and increase the effective TPBs, ionic conducting ceria was impregnated into the LSCT[sub](A-) anode, along with the metallic catalysts. The CeO₂-LSCT[sub](A-) cell shows a poor performance upon operation in hydrogen atmosphere containing 3% H₂O; and with addition of metallic catalysts, the cell performance increases drastically by almost three-fold. However, the infiltrated Ni particles on the top of ceria layer cause the deposition of carbon filament leading to cell cracking when exposure to humidified methane (3% H₂O). No such behaviour was observed on the CeO₂-NiFe impregnated anode. The microstructure images of the impregnated anodes at different times during stability testing demonstrate that the grain growth of catalysts, the interaction between the anode backbone and infiltrates, and the spalling of the agglomerated catalysts are the main reasons for the performance degradation. Fourth, the YSZ-LSCT[sub](A-) composites including the YSZ contents of 5-80wt.% were investigated to determine the percolation threshold concentration of YSZ to achieve electronic and ionic conducting pathways when using the composite as SOFC anode backbone. The microstructure and dilatometric curves show that when the YSZ content is below 30%, the milled sample has a lower shrinkage than the unmilled one due to the blocking effect from the well distributed YSZ grains within LSCT[sub](A-) bulk. However, at the YSZ above 30% where two phases start to form the individual and interconnected bulk, the composites without ball milling process show a lower densification. The impact of YSZ concentration and ball milling process on the electrical properties of the composites reveals that the percolation threshold concentration is not only dependant on the actual concentration, but also related to the local arrangement of two phases. In Napier University, the electroless nickel-ceramic co-depositon process was investigated as a manufacturing technique for the anodes of planar SOFCs, which entails reduced costs and reduced high-temperature induced defects, compared with conventional fabrication techniques. The Ni-YSZ anodes prepared by the electroless co-deposition technique without the addition of surfactant adhere well to the YSZ electrolyte before and after testing at 800°C in humidified hydrogen. Ni-YSZ anodes co-deposited with pore-forming starch showed twice the maximum power density compared with those without the starch. It has therefore been demonstrated that a porous Ni-YSZ cermet structure was successfully manufactured by means of an electroless plating technique incorporating pore formers followed by firing at 450°C in air. Although the use of surfactant (CTAB) increases the plating thickness, it induces the formation of a Ni-rich layer on the electrolyte/anode interface, leading to the delamination of anode most likely due to the mismatched TECs with the adjacent YSZ electrolyte.
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Perera, Chaminda Kithsiri. "The Effects of Mercury on the Performance of Ni/YSZ Anode in a Planar Solid Oxide Fuel Cell." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1268934012.
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Li, Xiaxi. "In situ characterization of electrochemical processes of solid oxide fuel cells." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54256.
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Solid oxide fuel cells (SOFCs) represent a next generation energy source with high energy conversion efficiency, low pollutant emission, good flexibility with a wide variety of fuels, and excellent modularity suitable for distributed power generation. As an electrochemical energy conversion device, SOFC’s performance and reliability depend sensitively on the catalytic activity and stability of the electrode materials. To date, however, the development of electrode materials and microstructures is still based largely on trial-and-error methods because of inadequate understanding of the mechanisms of the electrode processes. Identifying key descriptors/properties of electrode materials or functional heterogeneous interfaces, especially under in situ conditions, may provide guidance to the design of electrode materials and microstructures. This thesis aims to gain insight into the electrochemical and catalytic processes occurring on the electrode surfaces using unique characterization tools with superior sensitivity, high spatial resolution, and excellent surface specificity applicable under in situ/operando conditions.
Carbon deposition on nickel-based anodes is investigated with in situ Raman spectroscopy and SERS. Analysis shows a rapid nucleation of carbon deposition upon exposure to small amount of propane. Such nucleation process is sensitive to the presence of surface coating (e.g., GDC) and the concentration of steam. In particular, operando analysis of the Ni-YSZ boundary indicates special function of the interface for coking initiation and reformation.
The coking-resistant catalysts (BaO, BZY, and BZCYYb) are systematically studied using in situ Raman spectroscopy, SERS, and EFM. In particular, time-resolved Raman analysis of the surface functional groups (-OH, -CO3, and adsorbed carbon) upon exposure to different gas atmospheres provides insight into the mechanisms related to carbon removal. The morphology and distribution of early stage carbon deposition are investigated with EFM, and the impact of BaO surface modification is evaluated.
The surface species formed as a result of sulfur poisoning on nickel-based anode are examined with SERS. To identify the key factors responsible for sulfur tolerance, model cells with welldefined electrode-electrolyte interfaces are systematically studied. The Ni-BZCYYb interface exhibits superior sulfur tolerance.
The oxygen reduction kinetics on LSCF, a typical cathode material of SOFC, is studied using model cells with patterned electrodes. The polarization behaviors of these micro- electrodes, as probed using a micro-probe impedance spectroscopy system, were correlated with the systematically varied geometries of the electrodes to identify the dominant paths for oxygen reduction under different electrode configurations. Effects of different catalyst modifications are also evaluated to gain insight into the mechanisms that enhance oxygen reduction activity.
The causes of performance degradation of LSCF cathodes over long term operation are investigated using SERS. Spectral features are correlated with the formation of surface contamination upon the exposure to air containing Cr vapor, H2O, and CO2. Degradation in cathode performance occurs under normal operating conditions due to the poisoning effect of Cr from the interconnect between cells and the high operating temperature. The surface-modified LSCF cathode resists surface reactions with Cr vapor that impairs electrode performance, suggesting promising ways to mitigate performance degradation.
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Khan, Feroze. "Effect of Hydrogen Sulfide in Landfill Gas on Anode Poisoning of Solid Oxide Fuel Cells." Youngstown State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1338838003.
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Jia, Lu. "Étude de la fabrication de piles à combustible nanostructurées SOFC par l'injection de suspensions et de solutions dans un plasma inductif." Thèse, Université de Sherbrooke, 2010. http://savoirs.usherbrooke.ca/handle/11143/1943.
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In this work, the nano-structured components of solid oxide fuel cells have been produced, using radio frequency (RF) solution or suspension plasma spraying processes. The emerging technology of suspension plasma spraying was explored to produce thin and gas tight nano-structured solid oxide fuel cells electrolytes, which in an effort to develop a cost-effective and scalable fabrication technique for high performance solid oxide fuel cells (SOFCs). Glycine-nitrate process (GNP) produced cerium oxide (CeO[subscript 2]) and gadolinium oxide (Gd[subscript 2]O[subscript 3]) nano-powders were used to prepare suspensions and then separately injected to form composite GDC electrolyte coatings. A dynamic mask system has been developed to control the heating effects of a high-temperature plasma deposition process. The experimental results of the nano-structured SOFCs GDC electrolytes production by means of a RF suspension plasma spraying process using the newly proposed mask were compared to the ones without mask. The potential of this deposition technique to improve the electrolyte coating uniformity and to reduce the coating porosity was demonstrated. SOFCs anodes require long triple phase boundary (TPB) and appropriate gas diffusion pass for the fast transport of both fuel and exhaust gases, but the area where gas diffusion passes are especially required would be different from the area suitable for electrochemical reaction in the anodes. Functionally graded anodes in both composition and porosity have been proposed to fulfill the anodic functions in adequate anodic areas. On the basis of the optimized spraying conditions and the laboratory-developed solution feeding system, NiO-GDC functionally graded nanostructure anodes were prepared using solution plasma spraying (SolPS) process. Then the microstructure and material composition of the anodes were analyzed. A graded distribution in contents of both nickel and GDC was confirmed in the coating. Field emission scanning electron microscopy (FESEM) observation exhibited a continuous variation in porosity from 35% to 9% along the direction across the coating thickness. The functionally graded anodes deposited by SolPS process may minimize the thermal expansion mismatch between SOFC components and increase the length of triple phase boundary, which should lead to the improvement of the anodic performances. The successful fabrication of the functionally graded nano-structural electrodes as well as dense electrolyte coatings represents an opportunity for the Centre de Recherche en Énergie, Plasma et Électrochimie (CREPE) to fabricate the fully integrated nano-structured SOFC using solution and suspension plasma spraying processes.
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Bukhari, Syed Munawer. "New Perovskite Materials for Sensors and Low Temperature Solid Oxide Fuel Cell (LT-SOFC) Applications." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20206.
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This work involved the development of new perovskite oxides based on SmFeO3 and testing their performances as sensors for reducing gases (H2, CO & CH4) and as anode materials for dry methane oxidation in solid oxide fuel cells. The new perovskite oxide materials with formula Sm0.95Ce0.05Fe1-xMxO3-δ (M= Co, Ni & Cr) were synthesized by a sol gel method using citric acid as a complexing agent. The resulting materials were characterized by using a battery of techniques including XRD, XRF, XPS, SEM and electrochemical methods.
Sensing experiments revealed that both cobalt doped and Cr doped materials can detect H2, CO and CH4 in air at different temperatures including room temperature. The Ni doped materials did not prove good candidates as sensors. However, their reduction treatment studies showed the formation of metallic nanoparticles on the surface which deeply influence their electrical conductivity as well as sensing ability. Consequently, this modification in surface structure and chemical composition enabled them to sense hydrogen gas at 300oC very effectively. The response of sensors based on these reduced materials was measurable and reversible.
Some materials were also selected on the basis of their reduction stability and electrical properties, and their electrochemical performances were evaluated as SOFC anodes under dry methane and dry hydrogen fuels separately. The performance tests as SOFC anode revealed that the best anode material for the oxidation of dry hydrogen fuel is Sm0.95Ce0.05FeO3-δ. Furthermore, Sm0.95Ce0.05FeO3-δ proved to be coke resistant anode under dry methane fuel and exhibited reasonably low charge transfer resistance values at temperatures between 600-700oC. The doping of Co and Ni at the B-site of Sm0.95Ce0.05FeO3-δ found to be very effective in further improving its performance as SOFC anode towards oxidation of dry methane fuel at the lower temperatures.
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Scarabelot, Evandro Garske. "Obtenção e caracterização de pós Ce0,8La0,2O1,9 e Ce0,9Ca0,1O1,9 via síntese por combustão visando sua aplicação em SOFC." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/173138.
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O dióxido de cério (CeO2), pode apresentar condutividade iônica e eletrônica (condutor misto) em temperaturas relativamente baixas (considerando a faixa de trabalho 1000°C de uma SOFC). Esta característica torna este material promissor para uso em células a combustível de óxido sólido (SOFC ou CCOS) assim como em catalisadores. Vale destacar que em altas temperaturas o dióxido de cério puro é um mau condutor iônico, contudo pode-se obter um aumento significativo com a substituição estrutural do íon cério (Ce+4) por outro íon metálico de menor valência (La+3 e Ca+2). O estudo proposto consiste em sintetizar óxido de cério dopado com lantânio e cálcio com características microestruturais e elétricas adequadas para uso em uma CCOS. Utilizando o método de síntese de combustão foi estudado a influência que o excesso de combustível (sacarose) pode proporcionar nas características finais dos pós cerâmicos. A caracterização dos pós foi realizada pelas técnicas de raios-X (DRX), área superficial especifica (BET), análise termogravimétrica (TGA), Microscopia Eletrônica de: Varredura (MEV) e Transmissão (MET), Microscopia de Calefação (MC) e por fim a análise elétrica por meio da Espectroscopia de Impedância Eletroquímica (EIE). Os principais resultados mostraram que a técnica de síntese por combustão é um método eficiente para obtenção de pós nanoparticulados, bem dispersos e com elevada homogeneidade. Observou-se ainda que a troca do tipo de dopante assim como o teor de combustível utilizado na síntese interfere diretamente nas propriedades microestruturais, físicas e elétricas dos compostos finais a base de céria dopada. As amostras apresentaram comportamento condutor em baixas temperaturas (500°C) o que viabiliza sua utilização como catalizadores e também em CCOS após tratamentos térmicos em atmosferas adequadas para aplicação como eletrodos ou eletrólitos. Os resultados também demonstram que a céria dopada com cálcio tem características que se torna viável a substituição do lantânio para uso em uma CCOS.The cerium dioxide (CeO2) has ionic and electronic conductivity (mixed conductor) properties at relatively low temperatures (considering a working range of 1000°C for a SOFC). These characteristics make this material appropriate for use as anode in solid oxide fuel cells (SOFC or CCOS). It should be mentioned that pure cerium dioxide is a bad ionic conductor in high temperatures, but we have a significant increase with the structural substitution of the cerium ion (Ce+4) by another metal ion of lower valence (in its crystalline lattice). The proposed study consisted in the synthesis of ceria oxide with lanthanum and/ or calcium with microstructural and electrical characteristics, suitable for use in a CCOS. Using the combustion synthesis, the influence of excess of fuel (sucrose) on the final characteristics of the ceramic powder has been analyzed. The characterization of the powders was realized using X-ray (XRD), specific surface area (BET), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Electron Microscope Transmission (TEM), Microscope Heating (HSM) and Electrochemical Impedance Spectroscopy (EIS). The main results showed that the combustion synthesis technique is an efficient method to obtain nanoparticulate and well dispersed powders with high homogeneity. It was observed that the exchange of the dopant type as well as the fuel content used in the synthesis interferes directly in the microstructural, physical and electrical properties of the final compounds of ceria doped. Therefore, the calcium doped ceria has interesting characteristics for use in a CCOS.
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Wendler, Leonardo Pacheco. "SÍNTESE E CARACTERIZAÇÃO DE PÓS CERÂMICOS COM COMPOSIÇÃO LaCr0,5Ni0,5O3 BASEADO NO MÉTODO PECHINI PARA ÂNODO DE CÉLULAS A COMBUSTÍVEL DE ÓXIDO SÓLIDO." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2014. http://tede2.uepg.br/jspui/handle/prefix/1441.
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The solid oxide fuel cells (SOFCs) have been considered as one of the most promising power sources to the future, and because that have awakened the interest from the governments and large companies. The large scale utilization of these devices only depends on costs reduction and better systems performance. The anode is one of the most requested components of a SOFC, because maintains direct contact with the fuel. The anode material must presents thermal stability, compatibility with the electrolyte, good catalytic activity and electronic conductivity. A lot of materials have just tested for use as SOFCs anodes, including metals like platinum and nickel. However, many problems were found, mainly because platinum wasn´t able to maintain its integrity in the cell operation conditions, suffering peeling during the process; and nickel particles suffered sintering in the high operation temperatures of the cell, blocking the fuel arrival to reaction sites, causing the loss of system performance. One of the alternatives to these metals are the lanthanumcontaining materials with perovskite structure. To this study it has been proposed the utilization of a lanthanum-based perovskite containing chromium, which provides good stability, and nickel, which provides good catalytic activity. Thus, the aim of the present study is to obtain the perovskite structure LaCr0,5Ni0,5O3, and characterize it to verify if its properties place it like a possible material to utilization as SOFC anode. It was investigated the obtaining of this composition by Pechini method, and the samples were characterized by X-ray diffraction, infrared spectroscopy, thermo gravimetric analysis, differential thermal analysis, He picnometry, specific surface area by BET method, scanning electronic microscopy, energy dispersive X-ray spectrometry, impedance spectroscopy and mercury porosimetry. The synthesized material showed high electrical conductivity at room temperature, and showed potential for use as anode in SOFCs.
As células a combustível de óxido sólido (CaCOS, ou SOFCs, do inglês Solid Oxide Fuel Cells) tem sido consideradas como uma das mais promissoras fontes de energia do futuro, e por isso tem despertado o interesse dos governos e de grandes empresas. A utilização em larga escala desses dispositivos depende unicamente da redução de custos e do aumento do desempenho dos sistemas. O ânodo é um dos componentes mais solicitados de uma CaCOS, pois mantém contato direto com o combustível. O material do ânodo deve então apresentar estabilidade térmica, uma compatibilidade com o eletrólito, boa atividade catalítica e condutividade eletrônica. Muitos materiais já foram testados para utilização como ânodo em CaCOS, incluindo metais como platina e níquel. Porém foram encontrados muitos problemas, principalmente porque a platina não mantinha sua integridade nas condições de operação da célula, sofrendo descamação durante o processo; e o níquel sofria sinterização de suas partículas nas altas temperaturas de operação da célula, impedindo a chegada do combustível nos sítios de reação, causando a perda de desempenho do sistema. Uma das alternativas a estes metais é a utilização de materiais com estrutura perovisquita contendo lantânio Para este trabalho está sendo proposta a utilização de uma perovisquita baseada em lantânio contendo cromo, o qual fornece boa estabilidade, e níquel, o qual fornece boas propriedades catalíticas. Desta forma o objetivo do presente trabalho é estudar a obtenção da estrutura perovisquita LaCr0,5Ni0,5O3, e caracterizá-la para verificar se as suas propriedades a colocam como um possível material para utilização como ânodo em CaCOS. Foi investigada a obtenção desta composição através do método Pechini, e as amostras foram caracterizadas por difração de raios x, espectroscopia no infravermelho, análise termogravimétrica, análise térmica diferencial, picnometria a He, área superficial específica pelo método BET, microscopia eletrônica de varredura, espectrometria de energia dispersiva de raios x, espectroscopia de impedância e porosimetria de mercúrio. O material sintetizado apresentou alta condutividade elétrica à temperatura ambiente, e mostrou potencial para utilização como ânodo em CaCOS.
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Périllat-Merceroz, Cédric. "Titanates de structures pérovskite et dérivées : Influence des éléments constitutifs et de la dimensionnalité sur les propriétés d'anode SOFC." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2009. http://tel.archives-ouvertes.fr/tel-00459141.
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Les matériaux d'anode pour pile à combustible haute température (Solid Oxide Fuel Cell, SOFC) doivent répondre à un important cahier des charges. L'exigence d'une alimentation directe sous méthane (sans reformage en amont) rajoute des contraintes de fonctionnement au niveau de l'activation catalytique du gaz et le risque de formation de coke. Avec pour objectif la recherche du matériau idéal, l'influence de la dimensionnalité de la structure sur les propriétés catalytiques et électrochimiques a été étudiée. Après synthèse par voie sol-gel de type Pechini et caractérisation structurale par diffraction des rayons X, diffraction des neutrons et diffraction électronique, l'activation catalytique du méthane a été mesurée en condition de vaporeformage (CH4:H2O=10:1). Des mesures de conductivité électrique en température et sous faible pression partielle d'oxygène ont complété cette étude avant d'évaluer l'activité électrochimique en température et sous H2(97%)/H2O(3%) par spectroscopie d'impédance complexe sur cellules à électrodes symétriques ou sur cellule complète, avec ou sans imposition de courant. Parmi l'ensemble des composés testés, le meilleur candidat retenu est le membre x=0.80 de la série LaxSr1-xTiO3+δ, composé lamellaire découlant d'une organisation à long ordre de l'oxygène sur- stoechiométrique présent au sein de la structure. Bien que relativement faible par rapport à certains composés 3D (de l'ordre de 10-2 S.cm-1 à 1073K sous Ar/H2(2%)), sa conductivité électrique ne s'avère pas rédhibitoire, étant compensée par une forte activité catalytique et électrochimique.
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Gadacz, Geoffroy. "Développement d'une anode cermet Ni-CGO pour une pile à combustible monochambre fonctionnant sous un mélange O2/C3H8." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2010. http://tel.archives-ouvertes.fr/tel-00484669.
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Cette étude est dédiée au développement d'une anode pour une pile à combustible SOFC monochambre. Ce dispositif ne présente pas de séparation physique entre les compartiments anodique et cathodique, contrairement à une pile conventionnelle. Un mélange contenant de l'oxygène et un hydrocarbure est directement injecté sur l'ensemble du dispositif comprenant électrolyte, anode et cathode. La cathode doit être sélective à la réduction de l'oxygène et l'anode à l'oxydation de l'hydrocarbure. Ce dispositif permet donc de s'affranchir des problèmes d'étanchéité des dispositifs conventionnels mais les matériaux d'électrode doivent répondre à des critères catalytiques restrictifs. L'étude a été réalisée avec une anode de type cermet composée de nickel et d'oxyde de cérium gadolinié (CGO). L'hydrocarbure choisi est le propane. L'objectif du travail est de comprendre les phénomènes physico-chimiques se produisant à l'anode afin d'optimiser les conditions de fonctionnement de la pile monochambre, sous mélange O2 / C3H8. Pour cela, les propriétés catalytiques des poudres de nickel et de CGO ont été déterminées en fonction de la température et du rapport O2 / C3H8. Après avoir optimisé les paramètres de préparation des anodes par sérigraphie sur électrolyte support (CGO), des mesures de conductivité électrique par méthode Van der Pauw ont été réalisées également sous différents mélanges O2 / C3H8 en fonction de la température. La confrontation des résultats (propriétés catalytiques et électriques) a permis de mettre en évidence l'existence d'une température limite de fonctionnement, qui dépend du rapport O2 / C3H8. En-dessous de cette température limite, le nickel s'oxyde et l'anode catalyse principalement l'oxydation totale du propane. Au-dessus de cette température limite, le nickel reste sous la forme métallique et catalyse préférentiellement l'oxydation partielle du propane. Ces résultats sont également corroborés à des calculs thermodynamiques, qui mettent en évidence que la réaction préférentielle à basse température est l'oxydation du nickel. Des phénomènes d'oscillations de la conductivité électrique et de la température ont permis de proposer un mécanisme réactionnel basé sur le dépôt et l'oxydation de carbone. Enfin, des dispositifs complets monochambre ont été élaborés en utilisant une cathode BSCF (Ba0,5Sr0.5Co0,8Fe0,2O3) et testés.
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Borcezi, Janaina Semanech. "SÍNTESE E CARACTERIZAÇÃO DA PEROVISQUITA LaNi(1-x)CrxO3-d PARA UTILIZAÇÃO EM ÂNODO DE CÉLULAS A COMBUSTÍVEL." Universidade Estadual de Ponta Grossa, 2018. http://tede2.uepg.br/jspui/handle/prefix/2658.
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As células a combustível são vistas como uma promissora tecnologia de geração de energia para o futuro. Estes dispositivos possuem várias vantagens como a opções de combustíveis a serem utilizados e uma simplicidade no sistema de operação. Existem muitos tipos de células a combustível e dentre elas a que estão despertando mais interesse são as células a combustível de óxido sólido (CaCOS) por apresentarem maior eficiência de conversão, podendo chegar a 65%. Entre os dispositivos da célula a combustível, o ânodo é o que mantém contato com o combustível, assim, precisa apresentar características como estabilidade térmica, boa compatibilidade com o eletrólito, condutividade eletrônica e boa atividade catalítica. Pesquisas estão sendo desenvolvidas para os componentes da célula a combustível, a fim de tornar essa tecnologia comercialmente viável. Para o ânodo, as pesquisas desenvolvidas são com materiais a base de níquel, cobre, lantânio, platina e cobalto. As pesquisas também mostram que materiais com estrutura de perovisquita apresentam grande potencial quando utilizados como ânodo. Para o presente trabalho foi proposto o estudo da obtenção de perovisquitas do sistema LaNi(1-x)CrxO3-d, e a verificação da possibilidade de utilização como ânodo para célula a combustível. Para isto foram estudadas 3 composições LNC37 (x=7), LNC55 (x=5) e LNC73 (x=3). A obtenção das composições foi realizada pelo método Pechini, as amostras foram caracterizadas por difratometria de raios X, espectroscopia no infravermelho, análise térmica diferencial, microscopia eletrônica de varredura, espectroscopia de energia dispersiva de raios x, espectroscopia de impedância. A composição LNC73 apresentou estrutura romboédrica do grupo espacial R-3c, entretanto nos valores de temperatura de sinterização estudados esta composição mostrou a presença de uma segunda fase formada por La2NiO4, não demonstrando uma estabilidade estrutural adequada para uso em eletrodos de células a combustível. Dentre as composições estudadas as composições LNC37 e LNC55 apresentaram apenas uma fase com estrutura ortorrômbica do grupos espacial Pnma, e reuniram propriedades que indicam a possibilidade de serem utilizadas como anodo de células a combustível de óxido sólido.
Fuel cells are seen as a promising energy-generating technology for the future. These devices have several advantages such as the variety of fuels to be used and a simplicity in the operating system. There are many types of fuel cells and the most interesting ones are the solid oxide fuel cells (CaCOS), because they have a higher conversion efficiency, reaching 65%. Among the devices of the fuel cell, the anode is the one that maintains contact with the fuel, thus, it must present characteristics such as thermal stability, good compatibility with the electrolyte, electronic conductivity and good catalytic activity. Research is being developed for fuel cell components in order to make this technology commercially viable. For the anode, the researches developed are with materials based on nickel, copper, lanthanum, platinum and cobalt. The researches also show that materials with perovisquita structure present great potential when used as anode. For the present work the study of the perovisquitas of the LaNi (1-x) CrxO3-d system was proposed, and the possibility of use as an anode for fuel cells was proposed. For this, 3 compositions LNC37 (x = 7), LNC55 (x = 5) and LNC73 (x = 3) were studied. The compositions were obtained by the Pechini method, the samples were characterized by X-ray diffraction, infrared spectroscopy, differential thermal analysis, scanning electron microscopy, x-ray dispersive energy spectroscopy, and impedance spectroscopy. The composition LNC73 presented a rhombohedral structure of the R-3c space group, however in the studied sintering temperature values this composition showed the presence of a second phase formed by La2NiO4, not demonstrating a structural stability suitable for use in fuel cell electrodes. Among the studied compositions the compositions LNC37 and LNC55 presented only one phase with orthorhombic structure of the space group Pnma, and they gathered properties that indicate the possibility of being used as anode of solid oxide fuel cells.
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Chien, Chang-Yin. "Methane and Solid Carbon Based Solid Oxide Fuel Cells." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1299670407.
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Sivasankaran, Visweshwar. "Manufacturing and characterization of single cell intermediate-temperature solid oxide fuel cells for APU in transportation application." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS027/document.
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La fabrication de cellules de piles à combustible IT-SOFC de large dimension par un nouveau procédé simple et peu coûteux est présentée dans ce manuscrit. L’optimisation de ce nouveau procédé en regard de l’utilisation d’agents de porosité, d’épaisseur de couches et de température de frittage a été réalisée. Les résultats des tests électrochimiques sur des cellules de surface active 10 cm2 réalisés dans le dispositif Fiaxell semi-ouvert ont été détaillés pour différentes cellules. Des tests de performance de longue durée ont également été menés sur le dispositif Fiaxell, présentés et discutés. La préparation et la réalisation d’un nouveau banc de test de stack a également été mené et présenté dans ces travauxThe fabrications of large area IT-SOFC planar cell by new simple and cost effective process were explained. The optimization of the new process with respect to pore formers, thickness of layers, sintering temperature were performed. The electrochemical results of 10cm2 performed in Fiaxell open flange set up were detailed with respect to different configuration. Long term ageing performance tests of single cells were conducted in Fiaxell device and results are discussed. Preparation of new test bench and stacking process performed till now were briefed
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Vert, Belenguer Vicente Bernardo. "ELECTRODOS AVANZADOS PARA PILAS DE COMBUSTIBLE DE ÓXIDO SÓLIDO (SOFCs)." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/14669.
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Las celdas de combustible de óxido sólido (cuyo acrónimo en inglés es SOFC) son dispositivos energéticos capaces de convertir la energía química de un combustible directamente en energía eléctrica. Esto las dota de unas eficiencias eléctricas muy elevadas, que pueden llegar a ser del 80% si se aprovecha su calor residual de alta calidad mediante turbinas. Además, son capaces de funcionar con una gran variedad de combustibles: hidrógeno, gas natural, gas de síntesis, etanol, metanol, etc. Sin embargo, para su inserción en la cadena de producción energética, su temperatura de funcionamiento debería disminuir al rango de 500-700 ºC sin que se redujeran las densidades de potencias eléctricas generadas.
Las SOFC convencionales se basan en la conducción de iones oxígeno de su electrolito, que separa la reacción de combustión del combustible en sus semi-reacciones electroquímicas, generando de este modo la energía eléctrica directamente. Al disminuir la temperatura de operación en este tipo de SOFC, con electrolitos (o membranas) delgados e hidrógeno como combustible, la principal limitación de funcionamiento se centra en la activación y reducción del oxígeno que tiene lugar en el electrodo denominado cátodo. Por otro lado, el empleo de otros combustibles basados en carbono no es compatible con los materiales de ánodos actualmente utilizados.
Por tanto, es necesario el desarrollo de nuevos cátodos con mejoradas propiedades electrocatalíticas para la reducción de oxígeno a menores temperaturas, cuyas propiedades termo-mecánicas sean compatibles con las del resto de componentes de la celda, y la obtención de ánodos capaces de funcionar con combustibles basados en carbono.
La combinación conjunta de varios lantánidos y bario en la estructura perovskita (LalPrpSmsBab)0.58Sr0.4Fe0.8Co0.2O3 ha permitido obtener compuestos con resistencias de polarización de electrodo significantemente menores que las mostradas por el cátodo del estado de la técnica La0.6Sr0.4Fe0.8Co0.2O3 en el rango de temperaturas 450-650 ºC.Vert Belenguer, VB. (2011). ELECTRODOS AVANZADOS PARA PILAS DE COMBUSTIBLE DE ÓXIDO SÓLIDO (SOFCs) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14669
Palancia
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Delbos, Cédric. "Contribution à la compréhension de l'injection par voie liquide de céramiques (Y. S. Z. ; Pérovskite,. . . ) ou métaux (Ni,. . . ) dans un plasma d'arc soufflé afin d'élaborer des dépôts finement structurés pour S. O. F. Cs." Limoges, 2004. http://aurore.unilim.fr/theses/nxfile/default/e9f63d07-0a8c-400d-8f58-adc4585d61e6/blobholder:0/2004LIMO0035.pdf.
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Ces travaux de recherche sont dédiés à l’élaboration, par un même et unique procédé, des différentes couches (électrolyte / anode / cathode) entrant dans la composition des piles à combustibles à oxyde solide (S. O. F. Cs : Solid Oxide Fuel Cells). L’électrolyte en zircone yttriée (Y. S. Z. : Yttria Stabilised Zirconia) doit présenter une microstructure dense (imperméable aux gaz) d’une épaisseur comprise entre 5 et 20 µm, tandis que les électrodes doivent être poreuse et plus épaisses (200-500 µm), en Ni-Y. S. Z. (anode) et LaMnO 3 (cathode). La technique choisie pour atteindre ces objectifs est le procédé de projection par plasma d’arc soufflé, à pression atmosphérique, de céramiques ou de métaux injectés par voie liquide (précurseur ou suspension de poudre micrométrique ou sub-micronique). Pour mener à bien ces travaux, une bonne compréhension des phénomènes mis en jeu (paramètres plasma, injection de liquide, pénétration du jet de liquide et traitement de la suspension dans le plasma, nature et granulométrie des poudres employées pour la réalisation des suspensions,…) est nécessaire, et des modèles simples ont été utilisés pour déterminer des ordres de grandeurs et expliquer les résultats expérimentaux. Ces travaux ont ainsi permis la réalisation d’électrolytes denses d’épaisseurs comprises entre 5 et 20 µm et d’électrodes poreuses finement structurés. De plus, les premiers résultats sur la réalisation d’assemblage de ces différentes couches (électrolyte-cathode et électrolyte-anode) sont très prometteursThe aim of this PhD work is the elaboration, by a same process, of the different constituents (electrolyte / anode / cathode) of Solid Oxyde Fuell Cells (S. O. F. Cs ). The yttria stabilised zirconia electrolyte (Y. S. Z. ) should present a dense microstructure (gas impervious) with a thickness included betwen 5 and 20 µm, whereas the electrodes shoud be porous and thicker (200-500 µm), in Ni-Y. S. Z. (anode) and LaMnO 3 (cathode). The chosen process to reach these goals is the direct current plasma jet projection, under atmospheric pressure, of ceramics or metals by liquid injection (liquid precursor or micronic or submicronic powder suspensions). To bring this work to a successful conclusion, a good understanding of the acting event (plasma parameters, liquid injection, plasma liquid jet penetration and plasma suspension treatment, kind and granulometry of the powder used for the suspension production,…) is necessary, and simple models have been used in order to determine some magnitudes and explain experimental results. These works have also allowed the elaboration of dense electrolytes with a thickness included between 5 and 20 µm and finely structured porous electrodes. Moreover, the first results on multi layered production of the fuel cell constituent (electrolyte-cathode and electrolyte-anode) are likely
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Parikh, Harshil R. "Microstructure Changes In Solid Oxide Fuel Cell Anodes After Operation, Observed Using Three-Dimensional Reconstruction And Microchemical Analysis." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1417765534.
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Leite, Douglas Will. "Obtenção do cermet Ni-ZrO2 por moagem de alta energia." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-01082011-142900/.
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A obtenção do Cermet de níquel-zircônia via moagem de alta energia (Mechanical Alloying MA) foi estudado visando a preparação de anodos de células a combustível de óxido sólido (SOFC). O níquel metálico foi adicionado em três concentrações: 30, 40 e 50% em volume. As operações de moagem foram conduzidas em moinho vibratório de alta energia do tipo SPEX. Estudou-se a influência do tempo de moagem, a eficiência de aditivos para controle do processo, tipo e geometria dos potes de moagem. A influência destas variáveis foram avaliadas através de análises de tamanho de partículas, determinação de área superficial e morfologia do material resultante. O uso de pote de teflon resultou em contaminação por carbono. Por outro lado, o uso de pote de aço aumenta a contaminação por impurezas metálicas. As diversas geometrias projetadas para os potes mostraram que potes com maiores raios de concordância (R.15) apresentaram melhor rendimento. Após a conformação e sinterização a 1300°C em atmosfera de argônio, as amostras apresentaram valores de densidade entre 60 a 80% da densidade teórica. As microestruturas observadas por microscopia eletrônica de varredura revelaram uma boa homogeneidade na distribuição de fases do Cermet. A técnica de moagem de alta energia apresentou-se como boa opção na fabricação de Cermet Ni-ZrO2.The ZrO2 and metallic Ni Cermet obtained by Mechanical Alloying MA is studied in the present work with the objective to prepare solid oxide fuel cells anodes (SOFC). Metallic Ni is added under three different concentrations: 30, 40 and 50% volume. The millings were conducted in SPEX vibratory mill where the influence of milling time, process control additives efficiency, type and geometry of milling vessels were studied. The study of the influence of these variables was made under particle size analysis, surface area determination and resulting material morphology. The use of teflon vessel causes contamination by carbon. On the other side, steel vessel increases the contamination by metallic impurities. The several geometries projected and analyzed for the vessels showed that vessels with larger bottom radius (R.15) showed the best results. After conformation and sintering at 1300°C in argon atmosphere the samples reached densities between 60 and 80% of the theoretical density. Microstructures observed by scanning electron microscopy reveal good homogeneity in the Cermet phases distribution. The mechanical alloying technique was considered a good option to obtain Ni- ZrO2 Cermet.
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Ravella, Uday Krishna. "Thermal stability of potential fuel cell core materials La2Mo2-yWyO9 (0 ≤ y ≤ 2.0) under air and reductive atmospheres, and in contact with a Sr containing cathode material." Phd thesis, Université du Maine, 2012. http://tel.archives-ouvertes.fr/tel-00743197.
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La2Mo2-yWyO9 (y = 1.0 to 2.0) oxides were synthesized by conventional solid state route and studied by XRD, TC-XRD and DTA. A phase diagram of the series was proposed. The thermodynamically stable phases at room temperature are: for 1.0≤ y ≤1.2 a cubic β-La2Mo2O9 type solid solution, for 1.3≤ y ≤1.575 a biphasic mixture of β-La2Mo2O9 type + α-La2W2O9 type phases, and for 1.6≤ y ≤2.0 a triclinic α-La2W2O9 type solid solution. Inhomogeneous distribution of W is suspected in the biphasic samples. It is clear that the compounds above y =1.2 are not suitable for SOFC applications.Cationic diffusion studies were performed using SIMS on La2Mo2O9 (LMO)/La0.8Sr0.2MnO3-δ (LSM) annealed couples. Rod shaped LaMnO3 grains were observed on LMO pellet and SrMoO4 type phases were seen to be growing on LSM pellet. Hypotheses for possible reaction mechanisms are presented. Bulk diffusion coefficients of Sr and Mn in LMO and of Mo in LSM are extrapolated to be around 1x10-20 cm2.s-1 and 1x10-15 cm2.s-1, respectively, at 800oC. Similar diffusion studies were performed by depositing Mn and Sr cation rich solutions on LMO pellets and Mo rich solution on LSM pellet. Mn solution was observed to be forming, upon annealing, LaMnO3 single crystals on the surface of the LMO pellet. Mo in LSM and Sr in LMO diffusion coefficients appear to be much higher than in LMO/LSM couple experiments, namely around 1-2x10-10cm2.s-1 at 1150°C. Because of the reactivity, LMO/LSM couple is not desirable for SOFC applications, unless an appropriate buffer layer separates them.The stability of LMO and W-LMO was studied under reductive atmospheres. Successive structural changes from LMO to La7Mo7O30 (7730), an amorphous reduced phase La2Mo2O7-δ, and partial decomposition to metallic Mo were observed as a function of oxygen loss. The pO2 stability domain of La2Mo2-yWyO9 did not appear to change with W content, but the reduction kinetics varied with y. At reverse, the stability limit of the 7730 phase was found to be dependent on W content. The amorphous reduced phase can accommodate a wide range of oxygen stoichiometry (7-δ from 6.69 to 6.20), but its stability vs. pO2 is questioned. Resistivity measurements performed on a low compacity crack-free amorphous La2Mo2O7-δ sample showed significant increase in the conductivity (> 1 S.cm-1 at 1000 K) relative to La2Mo2O9, with a pseudo activation energy 0.255eV. It is postulated that n-type electronic conductivity arises from partial reduction of hexavalent Mo6+ to a mixture of Mo3+ and Mo4+.
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Bassil, Siréna. "Procédé propre de production de chaleur et d'électricité à partir d'un biogaz produit à l'échelle domestique : exemples de matériaux catalytiques de reformage du méthane." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10055.
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Le reformage catalytique du méthane en hydrogène, vecteur d'énergie pour les piles à combustibles de type Solid Oxide Fuel Cell (SOFC), a été étudié sur des matériaux d'anode à base de métaux supportés (NiO/CeO2, NiO-Y2O3-ZrO2) et également sur des catalyseurs de structure définie (La0,8Sr0,2TiO3+δ). La première famille de catalyseurs a été synthétisée par deux méthodes de préparation : la technique d'imprégnation en milieu aqueux et en milieu organique sur des supports du commerce CeO2 et Y2O3-ZrO2 ou préparés au laboratoire, et par le procédé sol-gel. Le titanate de lanthane dopé au strontium a été préparé par la méthode de co-précipitation et également par la méthode sol-gel. La méthode de préparation a un effet important sur les propriétés physico-chimiques des catalyseurs synthétisés et par conséquent affecte à la fois leur activité catalytique en reformage du méthane et leur résistance à l'empoisonnement par le dépôt de carbone. Les catalyseurs à base de nickel supporté sur cérine ont été par la suite dopés avec l'oxyde de magnésium (formation d'une solution solide MgO-NiO) ainsi qu'avec l'oxyde de lanthane (La2O3-NiO) en vue de limiter la formation de carbone sur la surface catalytique et augmenter ainsi la durée de vie des catalyseurs lors du reformage du méthane. Les résultats obtenus montrent que l'effet de promotion de la phase active NiO par MgO ou La2O3 diminue à la fois le dépôt de carbone mais également les performances catalytiques. Les propriétés physico-chimiques et les performances catalytiques de NiO-Y2O3-ZrO2 préparé par le procédé sol-gel ont été comparées à celles de matériaux commerciaux (Aldrich & Jülich) de même composition. Les résultats expérimentaux montrent que les matériaux synthétisés par la méthode sol-gel sont plus actifs en vaporeformage du méthane que ceux du commerce (dans le domaine de fonctionnement d'une pile SOFC) alors qu'ils présentent une activité similaire à ces derniers en reformage à sec du méthane. La quantité de carbone graphitique formée, quoique supérieure à celle observée dans le cas des catalyseurs commerciaux, demeure faible (< 2%). Ce dépôt de carbone ne provoque qu'une légère diminution des performances catalytiques en reformage à sec du méthane. Ceci est probablement lié à la diminution des sites actifsThe catalytic reforming of methane into hydrogen, for direct operation of Solid Oxide Fuel Cells (SOFCs) on methane, was studied on anode materials such as NiO/CeO2, NiO-Y2O3-ZrO2 and La0.8Sr0.2TiO3+δ. The first group of catalysts was synthesized by two methods: the impregnation technique both in aqueous and organic media (commercial and laboratory made CeO2 and Y2O3-ZrO2), and also using sol-gel process. Lanthanumtitanium oxide host structure doped with strontium was prepared both by co-precipitation and sol-gel process. The method of preparation has an important effect on the physico-chemical properties of the synthesized catalysts and affects consequently both their catalytic performances in methane reforming and their resistance to poisoning by carbon deposition. In order to limit carbon formation on the catalytic surface and to increase the lifetime of catalysts during the catalytic reforming of methane, ceria supported nickel based-catalysts were doped with magnesium oxide (forming MgO-NiO solid solution) as well as with lanthanum oxide (La2O3-NiO). The obtained results show that the effect of promotion of NiO active phase by MgO and La2O3 decreases carbon deposition but also the catalytic performances. Physico-chemical properties and catalytic performances of NiO-Y2O3-ZrO2 (Ni-YSZ) prepared by the sol-gel process were compared with those of commercial (Aldrich and Jülich) materials having the same composition. The experimental results showed that materials synthesized by the sol gel method are more active in methane steam reforming than commercial catalysts while sol gel and commercial samples show similar performances in methane dry reforming. Amounts of graphitic carbon, although being higher for sol gel samples compared to commercial ones, remain low (< 2%). This carbon deposit provokes only a slight decrease of catalytic performances of sol gel prepared materials in methane dry reforming, probably by decreasing the number of active sites
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Mirzababaei, Jelvehnaz. "Solid Oxide Fuel Cells with Methane and Fe/Ti Oxide Fuels." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1415461807.
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Aguilar, Luis Felipe. "Development of Sulfur Tolerant Materials for the Hydrogen Sulfide Solid Oxide Fuel Cell." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6979.
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One of the major technical challenges towards a viable H2S//Air SOFC is to identify and develop anode materials that are electronically conductive, chemically and electrochemically stable, and catalytically active when exposed to H2S-rich environments. The corrosive nature of H2S renders most traditional state-of-the-art SOFC anode materials (Ni, Pt, Ag) useless for long-term cell performance even at very low sulfur concentrations. In my doctoral thesis work, a new class of perovskite-based anodes was developed for potential use in SOFCs operating with H2S and sulfur-containing fuels. Cermets from this family of materials have shown excellent chemical stability and electrochemical performance at typical SOFC operating conditions. As an added benefit, they appear to preferentially oxidize H2S over hydrogen, as suggested by open circuit voltage, impedance spectra, and cell performance measurements obtained using various H2S-H2-N2 fuel mixtures. Cell power output values were among the highest reported in the literature and showed no significant deterioration during 48-hour testing periods. Impedance measurements indicated overall cell resistances decreased with increasing temperature and H2S content of the fuel. This behavior is starkly different from that of contemporary SOFC anodes, where the presence of H2S usually increases overall polarization resistance and ultimately destroys the cell. Results are promising due to the drastic improvement in sulfur tolerance compared to the current generation of SOFC power systems.
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Fagg, Duncan Paul. "Anodes for SOFCs (solid oxide fuel cells)." Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU082955.
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The success of Solid Oxide Fuel Cells (S.O.F.C) rests heavily on material selection. The performances of several compounds were investigated as possible anode materials, starting with reduced titanates such as the magnesium titanate and zirconium titanate. These compositions, although possessing many qualities beneficial for use as an anode material, were found to be too unstable for practical use. For this reason further work concentrated on stable, zirconia based, compounds with exhibited mixed conduction under reducing atmospheres. The mobility of electronic carriers is considered to be much higher than that of ionic defects, therefore, promising mixed conductors can be formed by doping a good ionic conductor with a small concentration of transition metal ions. Zirconia based mixed conductors were studied for two reasons. Firstly, zirconia stabilised in the cubic defect fluorite structure, exhibits a high level of ionic conductivity. Secondly, it is the most common electrolyte material for an S.O.F.C. An anode based on zirconia would, therefore, be expected to offer a good physical compatibility with the electrolyte material and to exhibit a high ionic contribution to total conductivity. Large defect fluorite solid solutions in the systems Y2O3-ZrO2-Nb2O5, Yb2O3-ZrO2-Nb2O5 and CaO-ZrO2-Nb2O5 were established, which enabled the effects of composition, dopant size and charge on conduction to be investigated. These effects were shown to be linked to structure. From these results and comparisons with the Y2O3-ZrO2-TiO2 system, optimum, mixed conducting, compositions were established. The sample Y0.25Ti0.15Zr0.60O1.875 exhibited the best mixed conducting properties to date, obtained for compositions based on zirconia.
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Choi, Song Ho. "Development of SOFC anodes resistant to sulfur poisoning and carbon deposition." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26601.
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Thesis (Ph.D)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Committee Chair: Meilin Liu; Committee Member: Arun Gokhale; Committee Member: Christoper Summers; Committee Member: Preet Singh; Committee Member: Tom Fuller. Part of the SMARTech Electronic Thesis and Dissertation Collection.