Fundamental Issues in Modeling of Mixed‐Conductors. Rebuttal to “Comment on ‘Electrode Kinetics of Porous Mixed‐Conducting Oxygen Electrodes’” [S. B. Adler, J. A. Lane, and B. C. H. Steel (pp. 3554–3564, Vol. 143, No. 11, 1996)]

Adler, Stuart B.; Lane, Jonathan A.; Steele, B.C.H.

doi:10.1149/1.1837696

Cited by 175 publications

(262 citation statements)

References 1 publication

Supporting

Mentioning

254

Contrasting

Unclassified

Order By: Relevance

“…However, the performance of pure La 1 À x Sr x Co 1 À y Fe y O 3 À d electrode is still limited by the oxygen ion transport process within the electrode bulk in addition to the oxygen exchange process at the surface. For example, Adler et al have experimentally and theoretically demonstrated that cathodic reaction of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 À d on gadolinia-doped ceria is dominated by both the oxygen ion transport and oxygen surface exchange processes [1,2]. To enhance the transport process of the LSCF electrode, doped ceria is often introduced, which can substantially improve the electrochemical performance.…”

Section: Introductionmentioning

confidence: 99%

Oxygen surface exchange properties of La0.6Sr0.4Co0.8Fe0.2O3 − δ coated with SmxCe1 − xO2 − δ

Hong

Zhang

Chen

et al. 2012

Journal of Power Sources

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Oxygen surface exchange properties of La0.6Sr0.4Co0.8Fe0.2O3 − δ coated with SmxCe1 − xO2 − δ

Hong

Zhang

Chen

et al. 2012

Journal of Power Sources

View full text Add to dashboard Cite

“…Ref [73]. provides a rationale for selecting oxygen vacancy concentration as the composition variable for modeling transport in mixed-conducting oxides like doped ceria.…”

mentioning

confidence: 99%

Carbon dioxide reduction on gadolinia-doped ceria cathodes

2008

View full text Add to dashboard Cite

AC impedance spectroscopy has been performed on 40 mol% gadolinia-doped ceria electrodes on yttria stabilized zirconia (YSZ) at 700-950°C in reducing CO/CO 2 atmospheres. Area-specific-resistance (ASR) values for this electrode were in the range of 0.8-37 Ω-cm 2 , about two orders of magnitude lower than measurements on Pt electrodes and slightly lower than data on Ni-YSZ electrodes in the literature under similar temperature and partial pressure of oxygen (P O 2 ) conditions. A continuum-based model of this electrode is described and an analysis performed to extract the vacancy diffusion coefficient (D v ) and surface exchange rate coefficient (R 0 ) as a function of temperature and P O 2 , from the impedance results. The D v data agree reasonably well with published measurements of the tracer diffusion coefficient (D ⁎ ) based on isotope profiling by secondary ion mass spectroscopy (SIMS) and conductivity measurements on 40 mol% GDC. The R 0 values are a factor of 3 lower than the published measurements of the surface reaction rate (k) obtained from isothermal thermogravimetric relaxation, and decrease with increasing P O 2 . Values of the thermodynamic factor (A) calculated from the fitted model parameters matched well with those calculated from oxygen nonstoichiometry data in the literature. Published by Elsevier B.V.

show abstract

“…However, the assumption ∇μ e = 0 does not imply that electron transport is not present, but rather that this process does not limit the oxygen transport. 15 The term corresponding to the differentiation of the thermodynamic factor, A, in Eq. 12 contains the product ∇ A∇c v,MC , and therefore it is of second order and can be omitted in accordance with earlier assumptions.…”

Section: Impedance Modelmentioning

confidence: 99%

“…Hence, its state is determined solely by temperature, pressure and the mentioned mole fractions. The total gas concentration, c, of both species in the gas pores is assumed to be constant with respect to time, t, and from this is follows that ∂c O 2 /∂t = c∂ x/∂t, so that the transport of O 2 , as caused by diffusion and flow, is [15] where v is the flow velocity. Still assuming that the total gas concentration is constant, and further that no reactions occur in the GP, the classical continuity equation reduces to ∇ · v = 0.…”

Section: Impedance Modelmentioning

confidence: 99%

Analytical, 1-Dimensional Impedance Model of a Composite Solid Oxide Fuel Cell Cathode

Mortensen¹,

Søgaard²,

Jacobsen³

2013

J. Electrochem. Soc.

View full text Add to dashboard Cite

An analytical, 1-dimensional impedance model for a composite solid oxide fuel cell cathode is derived. It includes geometrical parameters of the cathode, e.g., the internal surface area and the electrode thickness, and also material parameters, e.g., the surface reaction rate and the vacancy diffusion coefficient. The model is successfully applied to a total of 42 impedance spectra, obtained in the temperature range 555 • C-852 • C and in the oxygen partial pressure range 0.028 atm-1.00 atm for a cathode consisting of a 50/50 wt% mixture of (La 0.6 Sr 0.4 ) 0.99 CoO 3−δ and Ce 0.9 Gd 0.1 O 1.95−δ . The surface exchange coefficient in oxygen for T = 802 • C and p O 2 = 1.00 atm is found to be k Ex = 1.42 × 10 −4 m s −1 and with an activation energy of E a = 107 kJ mol −1 , in fair agreement with literature. A parameter variation and a steady state analysis is performed, verifying the soundness of the model and providing both qualitative and quantitative information on the evolution of the impedance spectra of cathodes with changing parameters.Solid oxide fuel cells (SOFCs) can effectively convert energy bound in a fuel to electrical energy and are thus an interesting alternative to conventional technologies with lower efficiencies. Recent trends in SOFC research and development have focused on lowering the operation temperature to the range 600 • C-750 • C. Such a decrease in temperature will enable the use of cheaper materials for stack components, and several of the degradation mechanisms are expected to significantly slow down. 1-3 However, a lowering of the temperature also causes the electrochemical efficiency of the electrodes to decrease. Especially, the cathode reaction with the highest activation energy will contribute the most to the overall resistance at lower temperature, 4 and therefore significant research in later years has focused on preparing cathodes with improved micro-structures and/or better materials. In this context, cathodes containing cobalt based perovskites seem particularly promising.As it is time-consuming and expensive to test new cathodes at a full cell level, fast screening techniques have been developed. These techniques include symmetrical cells 5 and three electrode measurements, 6 that probe only the electrode in question. Also, more fundamental methods of measuring the oxygen exchange kinetics and vacancy diffusion have been employed to characterize the oxygen exchange rate of cathode materials. Among these are electrical conductivity relaxation, 7 16 O/ 18 O oxygen exchange combined with secondary ion mass spectrometry, 8 pulsed isotope exchange techniques, 9 and the electrolyte probe method. 10 Symmetrical cells represent an especially fast and reliable screening technique for establishing the performance of cathodes, as it does not require sealing or other atmospheres than air. 5 The typical symmetrical cell consists of a supporting electrolyte tape with a thickness of approximately 200 μm, onto which electrodes have been attached, normally using screen printing or spraying,...

show abstract

Fundamental Issues in Modeling of Mixed‐Conductors. Rebuttal to “Comment on ‘Electrode Kinetics of Porous Mixed‐Conducting Oxygen Electrodes’” [S. B. Adler, J. A. Lane, and B. C. H. Steel (pp. 3554–3564, Vol. 143, No. 11, 1996)]

Abstract: not Available.

Cited by 175 publications

References 1 publication

Oxygen surface exchange properties of La0.6Sr0.4Co0.8Fe0.2O3 − δ coated with SmxCe1 − xO2 − δ

Oxygen surface exchange properties of La0.6Sr0.4Co0.8Fe0.2O3 − δ coated with SmxCe1 − xO2 − δ

Carbon dioxide reduction on gadolinia-doped ceria cathodes

Analytical, 1-Dimensional Impedance Model of a Composite Solid Oxide Fuel Cell Cathode

Contact Info

Product

Resources

About