Effect of the Ionic Conductivity of the Electrolyte in Composite SOFC Cathodes

Vohs, John M.; Gorte, Raymond J.

doi:10.1149/1.3581109

Cited by 50 publications

(47 citation statements)

References 61 publications

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“…4,[7][8][9]27,28,[31][32][33][34] The changes in microstructure are demonstrated by the SEM micrographs of LSF-YSZ composites after calcination to 1123 K and 1373 K, presented in Figure 3. For the 1123 K sample, the LSF particles are small, with a characteristic size of about 50 nm, and appear to coat the YSZ channels uniformly.…”

Section: Resultsmentioning

confidence: 98%

“…Of the various perovskites that are of interest, our group has focused on LSF because it does not react with YSZ at temperatures below 1373 K, 27,28 allowing changes in perovskite microstructure to be examined by varying the calcination temperature of the electrode after infiltration. 3,4,[27][28][29][30][31][32][33] Past work has shown that high calcination temperatures (e.g. 1373 K) dramatically decrease the surface area of the LSF phase and lead to a significant increase in the non-ohmic electrode resistance at open circuit.…”

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confidence: 99%

“…1373 K) dramatically decrease the surface area of the LSF phase and lead to a significant increase in the non-ohmic electrode resistance at open circuit. 4,[7][8][9]27,28,[31][32][33][34] It is important to point out that due to the relatively simple microstructure, the electrochemical characteristics of infiltrated SOFC cathodes can be described in terms of mathematical models with no or very few fitting parameters. 7,8,25,26 The electrode kinetics do not exhibit Tafelian behavior and the oxygen reduction reactions should not be described in terms of Butler-Volmer kinetics.…”

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confidence: 99%

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An Investigation of Oxygen Reduction Kinetics in LSF Electrodes

Küngas

Levine

et al. 2012

J. Electrochem. Soc.

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The characteristics of solid oxide fuel cell (SOFC) cathodes, prepared by infiltration of La0.8Sr0.2FeO3−δ (LSF) into porous yttria-stabilized zirconia (YSZ) scaffolds, were evaluated by studying the effect of p(O2) and of Al2O3 overlayers deposited by Atomic Layer Deposition (ALD) on impedance spectra at 873 and 973 K. The electrode resistance of LSF-YSZ composites calcined at 1123 K was dominated by high-frequency processes that show a relatively weak p(O2) dependence of −0.2 at 973 K. Composites calcined to 1373 K exhibited additional, low-frequency features in their impedance spectra that were more strongly dependent on p(O2), −0.43. These low-frequency processes are due to O2 adsorption limitations caused by the lower surface area of the LSF phase. Decreases in the exposed LSF surface caused by ALD films caused similar changes in the impedance spectra. The ALD overlayers were disrupted by heating to 1073 K and electrode polarization at 873 K. The implications of these results for understanding O2 adsorption limitations on SOFC cathodes are discussed.

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Section: Resultsmentioning

confidence: 98%

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confidence: 99%

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An Investigation of Oxygen Reduction Kinetics in LSF Electrodes

Küngas

Levine

et al. 2012

J. Electrochem. Soc.

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“…The two electrolyte materials tested in this study were 10% ScSZ and 8% YSZ. Although ScSZ is significantly more expensive than YSZ, it is mechanically stronger and has a higher ionic conductivity . The cells made with ScSZ had 100‐μm‐thick electrolytes, whereas the YSZ cells had electrolytes that were 160‐μm thick, made by laminating two 80‐μm tapes.…”

Section: Methodsmentioning

confidence: 99%

The stability of direct carbon fuel cells with molten Sb and Sb–Bi alloy anodes

et al. 2012

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The long‐term stability of direct carbon fuel cells, based on solid oxide fuel cells with molten Sb and Sb–Bi anodes, was examined for operation with activated charcoal, rice starch, and bio‐oil fuels at 973 K. With intermittent stirring of the fuel–metal anode interface, the anode performance was stable, and reasonable power densities (∼250 mW/cm2) were achieved for periods up to 250 h. With Sc‐stabilized zirconia, severe thinning of the electrolyte occurred in regions of high current flow. No electrolyte thinning was observed with yttria‐stabilized zirconia as the electrolyte operating at the same current densities. © 2012 American Institute of Chemical Engineers AIChE J, 59: 3342–3348, 2013

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“…Additional details on the tape-casting procedures can be found in previous publications. 11,12 In some cases, the porous layers were infiltrated with La 0.6 Sr 0. 4 3 .…”

Section: Journal Of the Electrochemical Society 164 (6) F525-f529 (2mentioning

confidence: 99%

An Investigation of LSF-YSZ Conductive Scaffolds for Infiltrated SOFC Cathodes

Cheng

Wilson

et al. 2017

J. Electrochem. Soc.

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Porous composites of Sr-doped LaFeO 3 (LSF) and yttria-stabilized zirconia (YSZ) were investigated as conductive scaffolds for infiltrated SOFC cathodes with the goal of producing scaffolds for which only a few perovskite infiltration steps are required to achieve sufficient conductivity. While no new phases form when LSF-YSZ composites are calcined to 1623 K, shifts in the lattice parameters indicate Zr can enter the perovskite phase. Measurements on dense, LSF-YSZ composites show that the level of Zr doping depends on the Sr:La ratio. Because conductivity of undoped LSF increases with Sr content while both the ionic and electronic conductivities of Zr-doped LSF decrease with the level of Zr in the perovskite phase, there is an optimum initial Sr content corresponding to La 0.9 Sr 0.1 FeO 3 (LSF91). Although scaffolds made with 100% LSF had a higher conductivity than scaffolds made with 50:50 LSF-YSZ mixtures, the 50:50 mixture provides the optimal interfacial structure with the electrolyte and sufficient conductivity, providing the best cathode performance upon infiltration of La 0.6 Sr 0. 1 First, the NiO-YSZ composite that will become the anode is co-fired together with the YSZ electrolyte to produce a dense electrolyte. Next, a doped-ceria layer is screen printed onto the cathode side of the dense electrolyte and fired to produce a doped-ceria film that will act as a barrier layer to prevent reaction of the LSCF with the YSZ. Finally, LSCF is screen printed onto the doped-ceria film and fired to a temperature sufficient to give the LSCF structural integrity and good adhesion to the electrolyte. Obviously, there would be significant advantages to reducing the number of fabrication and calcination steps.An alternative method for preparing high-performance LSCF cathodes involves preparing a porous YSZ scaffold on the cathode side of the electrolyte, followed by infiltration of LSCF nanoparticles or precursor salts.2 The NiO-YSZ anode, the YSZ electrolyte, and the YSZ scaffold layers can all be co-fired, and the doped-ceria barrier layer may not be needed.3 However, the infiltration method is not widely used because many infiltration steps are typically required to provide sufficient cathode conductivity.Recently, it was suggested that the number of infiltration steps could be greatly reduced if the porous scaffold was itself electronically conductive. 4 Infiltration is still required to add LSCF into the scaffold to carry out the oxygen-exchange reactions but the amounts required for the catalytic reaction can be much smaller. To implement this approach, it is necessary to find a conductive oxide that will not react with YSZ at the temperatures required to produce a dense electrolyte. Because Sr-doped LaFeO 3 (LSF) has been shown to be relatively unreactive with YSZ, 5-7 our group focused on preparing LSF-YSZ scaffolds for this application.4 Co-firing LSF and YSZ did not lead to new phases but a shift in the lattice parameter for the perovskite phase suggested that some Zr was entering the perovskite lattice. ...

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Effect of the Ionic Conductivity of the Electrolyte in Composite SOFC Cathodes

Cited by 50 publications

References 61 publications

An Investigation of Oxygen Reduction Kinetics in LSF Electrodes

An Investigation of Oxygen Reduction Kinetics in LSF Electrodes

The stability of direct carbon fuel cells with molten Sb and Sb–Bi alloy anodes

An Investigation of LSF-YSZ Conductive Scaffolds for Infiltrated SOFC Cathodes

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