Impedance of the Surface Double Layer of LSCF/CGO Composite Cathodes: An Elementary Kinetic Model

Yurkiv, Vitaliy; Costa, Rémi; Ilhan, Zeynep; Ansar, Asif; Bessler, Wolfgang G.

doi:10.1149/2.070404jes

Cited by 46 publications

(55 citation statements)

References 58 publications

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“…The Bode plots allow to tune the double layer capacitance parameters. When fitting these parameters, consistency with the literature values is privileged ∼100 F m −2 are found at the anode, in line with the estimates by Bertei et al 20 for Ni/YSZ interfaces, and ∼150 F m −2 are calculated at the cathode, which is higher than the value evaluated with the correlation by Yurkiv et al 47 for the LSCF/GDC interface, but still in the order of magnitude proposed in the literature. 48 The absence of an additional capacitance does not allow to describe the third, minor arc, whose impact is however negligible in the cell performance.…”

Section: Impedance Experiments At 700supporting

confidence: 89%

A Distributed Charge Transfer Model for IT-SOFCs Based on Ceria Electrolytes

Rahmanipour

Pappacena

Boaro

et al. 2017

J. Electrochem. Soc.

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A distributed charge transfer model for IT-SOFCs with MIEC electrolyte and composite electrodes is developed. A physically-based description of the electronic leakage current in the electrolyte is included, together with mass and charge conservation equations. The model is applied to simulate experimental polarization curves and impedance spectra collected on IT-SOFCs consisting of SDC electrolytes, Cu-Pd-CZ80 infiltrated anodes and LSCF/GDC composite cathodes. Hydrogen electro-oxidation experiments are examined (H 2 /N 2 humidified mixtures, 700 • C, 30-100% H 2 molar fraction). A significant increase of the ohmic resistance measured in the impedance spectra is revealed at decreasing the H 2 partial pressure or increasing the voltage (from 0.71 cm 2 at 100% H 2 to 0.81 cm 2 at 30% H 2 ). Good agreement between the calculated and experimental polarization and EIS curves is achieved by fitting the exchange current density and the capacitance of each electrode. Model and theoretical analyses allow to rationalize the observed shift of the ohmic resistance, highlighting the key-role played by the electronic leakage current. Overall, the model is able to capture significant kinetic features of IT-SOFCs, and allows to gain insight into relevant parameters for the optimal design of the cell (electrochemically active thickness, current and potential distribution, mass diffusion gradients). Samaria doped Ceria (SDC) and Gadolinia doped Ceria (GDC) are reference electrolyte materials for intermediate temperature solid oxide fuel cell (IT-SOFC) applications, thanks to their high ionic conductivity between 500• C and 700• C. 1-5 Associated to a high ionic conductivity, however, these materials show mixed ionic and electronic conductive (MIEC) properties, and their electronic conductivity increases when exposed to reducing atmospheres. The MIEC character of the electrolyte, in turn, results in the onset of electronic leakage currents (or short circuit currents) and low open-circuit voltage values. The leakage current has a chemical origin and is due to the partial reduction of Ce 4+ ions to Ce 3+ ions, prompted by the different chemical potential at the electrodes: this current is active also in the absence of an electric field applied on the cell, since it stems from the spontaneous transfer of ions across the lattice structure. As a consequence, the effects of the leakage current are not confined to the electrolyte, but extend to the electrodes, and entail a complex relationship with the current drawn from the cell. 6 Deeper insight can therefore be achieved by mathematical modeling.In the literature, comprehensive models can be found, which take into account the MIEC properties of Ce-based electrolytes. Starting from continuum rigorous descriptions, a series of models has been derived for the prediction of impedance spectra collected on MIEC electrolytes, the most important examples being those by Jamnik and Maier, 7 by the group of Haile 8,9 and by Atkinson et al. 10 These models propose closed-form, equivalent circuit-l...

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Section: Impedance Experiments At 700supporting

confidence: 89%

A Distributed Charge Transfer Model for IT-SOFCs Based on Ceria Electrolytes

Rahmanipour

Pappacena

Boaro

et al. 2017

J. Electrochem. Soc.

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“…Based upon this fit, our model yields a DL capacitance of 79 F m À2 (farad per microscopic LST surface). Considering that the surface DL represents the so-called chemical capacitance, reflecting the variability of the oxygen stoichiometry on the MIEC surface, the obtained value of 79 F m À2 is reasonable and well agrees with literature data for similar systems [15,18,19]. The LST-CGO interfacial DL capacitance is assumed to be temperature dependent.…”

Section: Mixed Conducting Anode Modelsupporting

confidence: 86%

“…The electrochemical models are based on previously published ones [15,16] that consider the following features:…”

Section: Modeling and Simulation Methodologymentioning

confidence: 99%

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Towards understanding surface chemistry and electrochemistry of La 0.1 Sr 0.9 TiO 3-α based solid oxide fuel cell anodes

Yurkiv

Constantin

Hornés

et al. 2015

Journal of Power Sources

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“…The simulation approach together with mathematical model is documented in our previous work (14,15) and only a brief summary is presented here. All chemical processes (chemical and electrochemical) are formulated as elementary reactions.…”

Section: Physical Modelmentioning

confidence: 99%

Lifetime and Performance Prediction of SOFC Anodes Operated with Trace Amounts of Hydrogen Sulfide

et al. 2015

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An elementary kinetic model is developed to predict the influence of sulfur on Ni/YSZ anodes of solid oxide fuel cells (SOFC) performance. A multi-step reaction mechanism describing the formation and oxidation of sulfur on the Ni surface is coupled with gas transport in the channel and porous phase, and charge-transfer processes. A thermodynamic and kinetic data set of sulfur formation and oxidation is derived based upon various literature sources including a coverage-dependent description of the enthalpy of surface-adsorbed sulfur. The validity of the model is demonstrated on two SOFC operation modes, namely H 2 /H 2 O/H 2 S and CH 4 /H 2 /H 2 O/H 2 S fuel mixtures, at different operating conditions using various electrochemical literature experiments. The first concern is the influence of adsorbed sulfur on chargetransfer processes and the second concern is the effect of adsorbed sulfur on complex methane reforming chemistry. The results reveal that sulfur surface coverage increases with current density demonstrating a low sulfur oxidation rate.

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Impedance of the Surface Double Layer of LSCF/CGO Composite Cathodes: An Elementary Kinetic Model

Cited by 46 publications

References 58 publications

A Distributed Charge Transfer Model for IT-SOFCs Based on Ceria Electrolytes

A Distributed Charge Transfer Model for IT-SOFCs Based on Ceria Electrolytes

Towards understanding surface chemistry and electrochemistry of La 0.1 Sr 0.9 TiO 3-α based solid oxide fuel cell anodes

Lifetime and Performance Prediction of SOFC Anodes Operated with Trace Amounts of Hydrogen Sulfide

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