Ionic conductivity of stabilized zirconia networks in composite SOFC electrodes

Yamahara, Keiji; Sholklapper, Tal Z.; Jacobson, Craig P.; Visco, Steven J.; Jonghe, Lutgard C. De

doi:10.1016/j.ssi.2005.03.010

Cited by 85 publications

(64 citation statements)

References 7 publications

(2 reference statements)

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“…and co-workers, [10] or to the creation of new oxygen reduction sites and additional triple phase boundaries with the cobalt spinel particles. The performance improvement and the reduction in non-ohmic resistance by cobalt infiltration for these cathodesupported cells was consistent with most of the results reported for Ni-SYSZ anode supported SYSZ cells [5], in which cobalt was infiltrated into a thin-film LSM-SYSZ cathode.…”

Section: Electrochemical Performancesupporting

confidence: 90%

“…6. The authors previously reported [5] that Co 3 O 4 nano-particles with an average size of 25 nm were found by TEM in the pores of infiltrated LSM-SYSZ composites heated up to an operational temperature of 650˚C. The improvement by cobalt infiltration might be attributed to enhancement of surface exchange processes on the LSM itself, such as discussed by Kilner, Steele.…”

Section: Electrochemical Performancementioning

confidence: 93%

“…At 800˚C, this power density is marginal for practical use. Recently, it was reported [5,6] that the LSM cathode activity can be dramatically improved by infiltrating nano-sized catalyst particles into its pores after the firing process. It may therefore be expected that the performance of LSM-supported thin-film SOFC cells could equally be improved by this procedure.…”

Section: Introductionmentioning

confidence: 99%

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Catalyst-infiltrated supporting cathode for thin-film SOFCs

et al. 2005

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The fabrication and electrochemical performance of co-fired, LSM-SYSZ [i.e. using humidified hydrogen as a fuel. Co-firing of bi-layers and tri-layers was successful at 1250˚C by optimizing the amount of carbon pore formers. A power density of a factor of 2.5 higher than that recently reported for the same type of cell at 800˚C [3] was obtained for a cell with cobalt infiltration into the supporting cathode: the peak power densities were 455, 389, 285, 202, 141 mW/cm 2 at 800, 750, 700, 650, 600˚C, respectively, and in most cases power densities at 0.7V exceeded more than 90 % of the peak output. Increasing the cathode porosity from 43 to 53 % improved peak power densities by as much as 1.3, shifting the diffusion limitation to high current densities. Cobalt infiltration into the support improved those by as much as a factor of 2 due to a significant reduction in non-ohmic resistance. These results demonstrate that cobalt catalyst-infiltrated LSM can be effective and low-cost supporting electrodes for reduced temperature, thin film SOFCs.

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Section: Electrochemical Performancesupporting

confidence: 90%

Section: Electrochemical Performancementioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Catalyst-infiltrated supporting cathode for thin-film SOFCs

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“…4 Because oxygen ion conduction is poor in LSM, [5][6][7] it is generally believed that the vicinity of three-phase boundaries ͑TPBs͒ of LSM cathode constitutes the active site for ORR. [8][9][10][11] Therefore, numerous studies have employed porous, high-surface-area electrodes with nanometer-scale LSM particle sizes [12][13][14] or composite LSM-YSZ 3,15,16 to enhance overall TPB length and thus lower ORR resistance and overpotential. However, it is not apparent how LSM particle sizes alter the rate-limiting reaction of ORR and the contributions of the TPB and bulk pathway 6,17,18 as a function of temperature, which limits the efficiency optimization of porous electrodes for intermediate temperature operation.…”

mentioning

confidence: 99%

Thickness Dependence of Oxygen Reduction Reaction Kinetics on Strontium-Substituted Lanthanum Manganese Perovskite Thin-Film Microelectrodes

O’

Shao‐Horn

2009

Electrochem. Solid-State Lett.

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Oxygen reduction reaction ͑ORR͒ kinetics was investigated on dense La 0.8 Sr 0.2 MnO 3 microelectrodes as a function of temperature and microelectrode thickness using electrochemical impedance spectroscopy. The surface oxygen exchange and mixed bulk/threephase-boundary ͑TPB͒ charge transfer process were found to control ORR kinetics at high and low temperatures, respectively. The transition temperature from the mixed bulk/TPB charge transfer control to surface oxygen exchange was found to be highly dependent on the microelectrode thickness ͑ϳ600°C for 65 nm vs ϳ800°C for 705 nm͒. These findings can be used to guide the design of electrodes that can operate at intermediate temperatures. Solid oxide fuel cells ͑SOFCs͒ that utilize 8 mol % yttriastabilized zirconia ͑YSZ͒ electrolyte, La 1−x Sr x MnO 3 ͑LSM͒ cathode, and nickel-YSZ anode typically operate at temperatures above 800°C. To reduce SOFC cost and increase SOFC durability, intense research efforts have been focused on reducing operating temperatures to 700°C or lower without sacrificing SOFC efficiency. [1][2][3] However, the main barrier to achieve acceptable SOFC efficiency at intermediate temperatures is the voltage loss at the LSM cathode, where oxygen reduction reaction ͑ORR͒ occurs. 4 Because oxygen ion conduction is poor in LSM, [5][6][7] it is generally believed that the vicinity of three-phase boundaries ͑TPBs͒ of LSM cathode constitutes the active site for ORR. [8][9][10][11] Therefore, numerous studies have employed porous, high-surface-area electrodes with nanometer-scale LSM particle sizes [12][13][14] or composite LSM-YSZ 3,15,16 to enhance overall TPB length and thus lower ORR resistance and overpotential. However, it is not apparent how LSM particle sizes alter the rate-limiting reaction of ORR and the contributions of the TPB and bulk pathway 6,17,18 as a function of temperature, which limits the efficiency optimization of porous electrodes for intermediate temperature operation.Electrodes with well-defined geometries, such as dense coneshaped pellets, 19-21 thin films, 22-25 and patterned microelectrodes, [26][27][28][29][30][31][32][33] have been used to provide simple scaling relationships between ORR impedance and electrode dimensions, such as TPB length. Mizusaki et al. 6 first demonstrated that oxygen-ion diffusion can occur through dense, oxygen-over-stoichiometric LSM electrodes having thickness of 1-2 m at 700-900°C. Brichzin et al. 28,29 have subsequently utilized microelectrodes with a thickness of 100 nm to show that ORR occurs predominantly via the bulk pathway instead of the TPB pathway at 800°C. In addition, Koep et al. 30 have used dense, patterned LSM electrodes of different thickness to show a critical thickness of 360 nm at 700°C, where the bulk pathway dominates having surface reactions as rate limiting for ORR. More recently, la O' et al. 33 have employed microelectrodes to propose four distinct processes during ORR on LSM: ͑i͒ ion transport in 8YSZ, ͑ii͒ a surface diffusion process on LSM, ͑iii͒ at least one surface...

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“…Após essa etapa, a pastilha foi novamente pesada e a diferença de peso atribuída à água retida nos poros. Métodos mais complexos para a medida de porosidade são referidos na literatura, como massa específica do material [19], condutividade iônica [20], análise digital da estrutura [21], e outros métodos especiais [22,23]. Entretanto, os resultados dessas técnicas mais elaboradas não mostram nenhuma vantagem sobre o método da absorção de água ou solvente.…”

Section: Preparação Da Célula Unitáriaunclassified

Preparação e avaliação de célula a combustível do tipo PaCOS unitária com ânodo a base de níquel e cobalto

Silva¹,

Alencar²,

Fiúza³

et al. 2007

Matéria (Rio J.)

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RESUMOUma célula a combustível do tipo PACOS unitária foi preparada e avaliada na geração de energia elétrica, utilizando metano ou hidrogênio como combustível. O ânodo da célula foi sintetizado a partir do eletro-catalisador desenvolvido e testado nesse trabalho (CATAC). O CATAC foi preparado pela mistura mecânica da zircônia estabilizada com ítria (YSZ) com os precursores metálicos (nitrato de níquel e cobalto, em sua forma hexahidratado), adicionando-se 25% de ácido cítrico à massa total da mistura e por fim calcinado a 800°C por quatro horas em ar. O catalisador foi caracterizado por fluorescência de raios X (XRF) e espectroscopia foto-eletrônica de raios X (XPS), a qual não indicou interação eletrônica entre o cobalto e níquel; o teor metálico do CATAC foi de aproximadamente 35% em massa. O CATAC foi testado para a geração de hidrogênio a partir da reforma a vapor do metano, mostrando boa produtividade de hidrogênio a partir de 600ºC. A estrutura do ânodo/eletrólito/cátodo foi preparada por prensagem de uma camada de CATAC misturado com grafite, uma camada de YSZ puro, e uma camada de óxido misto de lantânio, estrôncio e manganês (LSM) e grafite. O conjunto foi então prensado e sinterizado a 1380°C por quatro horas. Nas superfícies do ânodo e cátodo foram fixadas telas de platina, com o auxílio de tinta de platina, sendo o conjunto aquecido a 1100°C. Todo o sistema foi colado a um reator de alumina utilizando cola cerâmica. Microscopias por MEV da estrutura mostraram eletrólito denso e eletrodos porosos, com um conjunto adequadamente sinterizado. A célula unitária foi testada utilizando metano ou hidrogênio como combustível, a três temperaturas de operação. A tensão variou inversamente proporcional com a corrente, quando o desempenho foi medido a 850 ou 950ºC e hidrogênio, mas manteve-se constante acima de cinco mV a 800ºC com metano. A célula unitária mostrou um desempenho satisfatório na geração de eletricidade tanto com metano quanto com hidrogênio como combustíveis. Palavras chaves:Rede Cooperativa, pilha a combustível, óxido sólido, catalisador, níquel, cobalto, YSZ. Synthesis and Evaluation of Solid Oxide Fuel Cell (SOFC) with Anode based on Nickel and Cobalt ABSTRACTA unitary solid oxide fuel cell (SOFC) was prepared and evaluated for the electric energy generation, using methane and hydrogen as fuel. The cell anode was made with the electro-catalyst developed and characterized in this work (CATAC). CATAC was prepared by the mechanical mixture of zirconia stabilized with ytria (YSZ) and the metallic precursors (nickel and cobalt nitrate, hexahydrated), adding 25% of citric acid to the total mass, and finally calcined at 800°C for four hours in air. The catalyst was characterized by X-ray fluorescence (XRF) and X-ray photo-electronic spectroscopy (XPS), which did not indicate any electronic interaction between nickel and cobalt; CATAC metal content was approximately 35% in mass. CATAC was tested for the hydrogen generation from methane vapor reforming, showing good productivity starting at 600ºC. The ...

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Ionic conductivity of stabilized zirconia networks in composite SOFC electrodes

Cited by 85 publications

References 7 publications

Catalyst-infiltrated supporting cathode for thin-film SOFCs

Catalyst-infiltrated supporting cathode for thin-film SOFCs

Thickness Dependence of Oxygen Reduction Reaction Kinetics on Strontium-Substituted Lanthanum Manganese Perovskite Thin-Film Microelectrodes

Preparação e avaliação de célula a combustível do tipo PaCOS unitária com ânodo a base de níquel e cobalto

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