Anomalous transport property at surface and interface of metal/rare earth doped ceria

Kishimoto, Haruo; Sakai, Natsuko; Yamaji, Katsuhiko; Horita, Teruhisa; Brito, Manuel E.; Yokokawa, Harumi; Amezawa, Koji; Uchimoto, Yoshiharu

doi:10.1016/j.ssi.2008.03.041

Cited by 18 publications

(22 citation statements)

References 10 publications

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“…Concerning roles of ceria layer, effects of water vapors should be discussed . On the basis of accumulated knowledge by AIST endeavors , it can be pointed out that a small amount of water vapors can be emitted from the ceria‐LSCM‐gas three phase boundaries (TPB) and this can clean up the electrochemical area; hydrogen permeation experiments provide the magnitude of proton conductivities in GDC or YSZ. As will be shown later, the magnitude of the proton conductivity in YSZ is about seven order of magnitude lower than that of the ionic conductivity.…”

Section: Cathode Overpotentialmentioning

confidence: 99%

Recent Achievements of NEDO Durability Project with an Emphasis on Correlation Between Cathode Overpotential and Ohmic Loss

et al. 2017

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Long-term performance testes by CRIEPI (Central Research Institute for Electric Power Industry) on six industrial stacks have revealed an interesting correlation between cathode polarization loss and ohmic loss. To make clear the physicochemical meaning of this correlation, detailed analyses were made on the conductivity degradation of YSZ electrolyte in button cells and then on the ohmic losses in the industrial cells in terms of time constants which are determined from speed of the tetragonal transformation through the Y diffusion from the cubic phase to the tetragonal phase. In some cases, shorter time constants (faster degradations) were detected than those expected from the two-time-constant (with and without NiO reduction effects) model, suggesting that additional ohmic losses after subtracting the contribution from the tetragonal transformation must be caused from other sources such as cathode-degradation inducing effects. Main cathode degradations can be ascribed to sulfur poisoning due to contamination in air in the CRIEPI test site. An important feature was extracted as this cathode degradations became more severe when the gadolinium-doped ceria (GDC) interlayers were fabricated into dense film. Plausible mechanisms for cathode degradations were proposed based on the Sr/Co depletion on surface of lanthanum strontium cobalt ferrite (LSFC) in the active area. Peculiar cathode degradations found in stacks are interpreted in term of changes in surface concentration by reactions with sulfur oxide, electrochemical side reactions for water vapor emission or Sr volatilization, and diffusion of Sr/Co from inside LSCF.

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Section: Cathode Overpotentialmentioning

confidence: 99%

Recent Achievements of NEDO Durability Project with an Emphasis on Correlation Between Cathode Overpotential and Ohmic Loss

et al. 2017

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“…It has been demonstrated that isotope exchange with subsequent SIMS analysis is a very powerful tool to monitor the surface reaction kinetics and the bulk diffusion of oxygen in SOFC electrode and electrolyte materials under both equilibrium and polarized conditions [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] . Moreover, because of the relatively high lateral and depth resolution of SIMS, the electrochemically active regions of the electrodes can be visualized.…”

Section: Introductionmentioning

confidence: 99%

Mapping electrochemically driven gas exchange of mixed conducting SrTi0.7Fe0.3O3−δ and Ce0.8Gd0.2O1.9 thin films by 18O tracer incorporation under reducing atmosphere

et al. 2015

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Thermally and electrochemically driven 18O tracer exchange experiments in H2/H218O atmosphere were performed on SrTi0.7Fe0.3O3 − δ and Ce0.8Gd0.2O2 − δ thin films on single crystalline YSZ substrates. Noble metal current collectors were deposited on both films and electrochemically polarized during the exchange experiment. The resulting tracer distribution was analyzed by spatially resolved secondary ion mass spectrometry. Increased tracer fraction near the current collectors was found under cathodic polarization and decreased tracer fraction under anodic polarization. High cathodic bias leads to enhanced n-type electronic conductivity, which increases the extent of the electrochemically active zone.

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“…(ii) Our previous investigation revealed that the oxygen exchange was broadly enhanced on GDC surface around the TPB of gaseous O 2 /Au/GDC with increasing temperature (10).…”

Section: Ecs Transactions 13 (26) 105-114 (2008)mentioning

confidence: 97%

Effect of Temperature and Applied Potential on Oxygen Transport Paths around Gold / Ion Conducting Oxides Hetero Interfaces

Kishimoto¹,

Sakai²,

Yamaji³

et al. 2008

ECS Trans.

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The effect of applied potential on the oxygen transport around gold / gadolinium doped ceria (GDC) or yttria stabilized zirconia (YSZ) was investigated by using oxygen isotope exchange and secondary ion mass spectrometry (SIMS). The active area of oxygen exchange was clearly observed along Au / YSZ / O 2 triple phase boundary (TPB) treated under an applied potential (cathodic polarization) of E = -0.3 V at T = 773 K in dry O 2 , whereas no obvious activation was observed at E = 0 V. On the other hand, the activation of oxygen exchange was broadly observed on GDC surface around Au/GDC boundary, and it was remarkably enhanced by applying the electric potential of E = -0.3 V. The difference of oxygen transport path between Au/YSZ system and Au/GDC system was discussed in relation to the difference in chemical properties of electrolyte materials. IntroductionThe oxygen transport around the interfaces between electron conducting metal or oxide electrodes / ion conducting oxide electrolytes is very important to realize the kinetics in surface reactions of oxygen permeation membrane, sensors and cathode reactions in solid oxide fuel cells (SOFC). Concerning the cathode reaction in SOFC, it consists of several reaction steps:1. Adsorption of oxygen molecule on electrode surface, 2. Surface diffusion of adsorbed oxygen to the triple phase boundary (TPB) of gas / electron conducting metal or oxide (electrolyte) / ion conducting oxide (electrolyte), 3. Reduction of oxygen by charge transfer process between adsorbed oxygen and oxide ion in electrolyte, 4. Dissolution of oxygen as oxide ion into electrolyte.The reaction processes on simplified interfaces with metal electrode / electrolyte, for examples, platinum / YSZ (1-4) or gold / YSZ (5,6) have been intensively investigated by using a conventional electrochemical method, such as current interruption, complex impedance spectroscopy. Those electrochemical methods have been well established. By these methods, it is easy to obtain the information of charge carrier migration along current path but it is not easy to interpret the observed data because all information is obtained as the changes of current and voltage in which the local transport of oxygen atom and oxide ion are neglected or are not well taken into account. In the actual electrode / electrolyte interfaces, the reaction does not always proceed homogenously, and there will be some inhomogeneous distribution of reaction active sites which will be influenced by many parameters, that is, physical properties of electrode and electrolyte materials and their combination, temperature, magnitude of cathodic polarization etc.To obtain information about the local oxygen transport in the vicinity of interface, we have adopted the experimental approaches for visualizing the tracks of oxygen transport at interfaces by using the oxygen isotope ( 18 O) labeling and subsequent secondary ion mass spectrometry analyses (SIMS). Kawada et al. firstly reported that the oxygen exchange was activated at those very restricted areas of pla...

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Anomalous transport property at surface and interface of metal/rare earth doped ceria

Cited by 18 publications

References 10 publications

Recent Achievements of NEDO Durability Project with an Emphasis on Correlation Between Cathode Overpotential and Ohmic Loss

Recent Achievements of NEDO Durability Project with an Emphasis on Correlation Between Cathode Overpotential and Ohmic Loss

Mapping electrochemically driven gas exchange of mixed conducting SrTi0.7Fe0.3O3−δ and Ce0.8Gd0.2O1.9 thin films by 18O tracer incorporation under reducing atmosphere

Effect of Temperature and Applied Potential on Oxygen Transport Paths around Gold / Ion Conducting Oxides Hetero Interfaces

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