Impedance Study of Alternative (La,Sr)FeO[sub 3−δ] and (La,Sr)(Co,Fe)O[sub 3−δ] MIEC Cathode Compositions

Leonide, André; Rüger, Bernd; Weber, André; Meulenberg, Wilhelm Albert; Ivers‐Tiffée, Ellen

doi:10.1149/1.3265473

Cited by 123 publications

(97 citation statements)

References 19 publications

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“…12,28,29 A complete assignment to gas conversion, diffusion, and three phase boundary (TPB) processes was performed for the particular SOEC in this work. The processes along with their relaxation frequencies are listed in Table I.…”

Section: Electrochemical Analysismentioning

confidence: 99%

A Comparative Study of Durability of Solid Oxide Electrolysis Cells Tested for Co-Electrolysis under Galvanostatic and Potentiostatic Conditions

Rao¹,

Sun²,

Hagen³

2018

J. Electrochem. Soc.

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State-of-the-art SOECs consisting of a nickel-yttria stabilized zirconia (Ni-YSZ) fuel electrode, YSZ electrolyte and lanthanum strontium cobaltite ferrite-gadolinium doped ceria (LSCF-GDC) composite oxygen electrode were tested under co-electrolysis (H 2 O+CO 2 ) conditions. The aim in this study was to compare the SOEC durability under co-electrolysis conditions between galvanostatic and potentiostatic modes. Specifically, the cells were operated at 0.75 A/cm 2 (galvanostatic) and at 1.2 V (potentiostatic) at 750 • C for over 1000 hours. In both modes, a larger degradation was observed initially for the first 200 hours of testing, followed by a more stable performance over longer operating times. Interestingly, there was a difference in trends of serial and polarization resistances' evolution. In galvanostatic mode of operation, both increased while for potentiostatic mode only the polarization resistance increased over time. The difference of the degradation was attributed to the overpotentials being experienced by the cells in the respective modes. Trends of the area specific resistance (ASR) and detailed electrochemical analysis of the performance of the cell under durability conditions for both modes indicated that the degradation was due to both the fuel electrode and the oxygen electrode, with an additional contribution from fuel electrode in galvanostatic testing. Microstructural analysis also confirmed the degradation of the active fuel electrode.

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Section: Electrochemical Analysismentioning

confidence: 99%

A Comparative Study of Durability of Solid Oxide Electrolysis Cells Tested for Co-Electrolysis under Galvanostatic and Potentiostatic Conditions

Rao¹,

Sun²,

Hagen³

2018

J. Electrochem. Soc.

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“…In particular, the author's group has developed diagnosis methods of operating status of the polymer electrolyte fuel cell (PEFC) by analyzing the variation of resistances and capacitances of equivalent circuit models of the PEFC (Konomi & Saho, 2006;Nakajima et al, 2008). For the SOFC, a number of EIS analyses have been reported (Barsoukov & Macdonald, 2005;Esquirol et al, 2004;Horita et al, 2001;Huang et al, 2007;Ishihara et al, 2000;Jiang, 2002;Leonide et al, 2010;McIntosh et al, 2003). Although many of those reports focused on the characterization of developed materials, there were very few reports (Barfod et al, 2007) that analyze each impedance of the anode and cathode in the full cell impedance of a practical cell simultaneously and separately by applying EIS under operation.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Impedance Spectroscopy Study of the Mass Transfer in an Anode-Supported Microtubular Solid Oxide Fuel Cell

Nakajima¹

2011

Mass Transfer - Advanced Aspects

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“…14,15 In the same direction, Leonide et al reported a method to render the specific k δ and D δ values of MIEC cathodes by combining electrochemical impedance spectroscopy with an analysis of the distribution of relaxation times (DRT) and the electrode geometry. 16 Most recently, Endler-Schuck et al published the evolution of these parameters as a function of time * Electrochemical Society Member.…”

mentioning

confidence: 99%

Oxygen Transport Kinetics of Mixed Ionic-Electronic Conductors by Coupling Focused Ion Beam Tomography and Electrochemical Impedance Spectroscopy

Almar

Szász

Weber

et al. 2017

J. Electrochem. Soc.

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The oxygen reduction reaction of mixed ionic-electronic conducting (MIEC) cathodes Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) and La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) is investigated by detailed electrochemical impedance spectroscopy and focused ion beam tomography. The oxygen transport parameters of these materials are usually determined for model systems, such as dense bulks or thin films. However in the present study, probable differences regarding the time and thermal history of the samples (e.g. ambient poisoning gases, grain coarsening, secondary phase or surface segregation, etc.) were avoided by the in situ sintering of electrodes with nominal stoichiometry under synthetic air. The microstructural parameters of the electrodes are obtained by 3D FIB-SEM reconstruction tomography and subsequently used in combination with the Adler-Lane-Steele analytical model to calculate a simulated cathode resistance. Large discrepancies are observed compared to the electrochemical impedance measurements. In particular, the electrochemical impedance measurements do not show a Gerischer behavior, as expected for MIEC materials controlled by a coupled surface-exchange and bulk diffusion. Analysis by distribution function of relaxation times (DRT) reveals four individual processes taking place, indicating a surface-exchange controlled behavior with a reaction zone similar to the particle size. Bulk diffusion (D) and surface-exchange (k) coefficients from literature are critically discussed and tentative surface-exchange coefficients (k) for both MIECs are given. High-temperature devices such as solid oxide fuel cells (SOFCs) and oxygen transport membranes (OTMs) are promising systems for working towards zero-emissions power generation. The selected materials require high chemical and microstructural stability, as well as high catalytic activity during the oxygen reduction reaction (ORR), under normal operational conditions (i.e. operational temperature and oxygen partial pressure). Particularly interesting are the mixed ionic-electronic conducting (MIEC) materials, based on the ABO 3 perovskite structure. Their material properties can be flexibly customized, giving solid solutions with high ionic-electronic conductivity and hence good transport properties. More specifically, La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) has become established as the stateof-the-art SOFC cathode, while Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) has presented outstanding oxygen permeation flux in its cubic phase. 1-3The surface-exchange coefficient (k) and the oxygen diffusion coefficient (D) provide key information about the oxygen transport mechanism that dominates the cathodic ORR. Many publications have assessed the D and k values of MIEC materials, most commonly by; electrical conductivity relaxation (ECR) measurements for dense bulks [4][5][6][7][8] and temperature for LSCF cathodes. 17 Here it should be pointed out that the well-known ALS model can only be applied if the measured impedance shows a Gerischer impedance, which indicates tha...

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Impedance Study of Alternative (La,Sr)FeO[sub 3−δ] and (La,Sr)(Co,Fe)O[sub 3−δ] MIEC Cathode Compositions

Cited by 123 publications

References 19 publications

A Comparative Study of Durability of Solid Oxide Electrolysis Cells Tested for Co-Electrolysis under Galvanostatic and Potentiostatic Conditions

A Comparative Study of Durability of Solid Oxide Electrolysis Cells Tested for Co-Electrolysis under Galvanostatic and Potentiostatic Conditions

Electrochemical Impedance Spectroscopy Study of the Mass Transfer in an Anode-Supported Microtubular Solid Oxide Fuel Cell

Oxygen Transport Kinetics of Mixed Ionic-Electronic Conductors by Coupling Focused Ion Beam Tomography and Electrochemical Impedance Spectroscopy

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