Redox and phase behavior of Pd-substituted (La,Sr)CrO3 perovskite solid oxide fuel cell anodes

Victor Y. Zenou, Daniel E. Fowler, Romain Gautier, Scott A. Barnett, Kenneth R Poeppelmeier, Laurence D. Marks

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The use of palladium and strontium in LaCrO3 perovskites for solid oxide fuel cell anodes is known to lead to improved performance, in part due to the formation of palladium at the surface under reducing conditions that can act as a catalyst, with regeneration of the catalyst possible by cycling between oxidizing and reducing conditions. Whether this cycling involves dissolution and exsolution of the palladium into the perovskite is unclear. We describe a detailed analysis of the perovskites La0.8Sr0.2Cr1 − xPdxO3 − δ (LSCrPd, nominal stoichiometry x = 0.1 and 0.2) under reducing and oxidizing conditions. A LSCrPd perovskite was found to be the main phase, further confirmed by transmission electron microscopy. Secondary phases including metallic Pd, PdO, and La4PdO7, as well as SrCrO4, were also present. Some phases, such as PdO, SrCrO4, and La4PdO7, were no longer present following reduction while other phases such as metallic Pd and La2O3, were found in increasing amounts. When used as active solid oxide fuel cell anode layers both with and without Gd0.1Ce0.9O2 − β (GDC) in La0.9Sr0.1Ga0.8Mg0.2O3 − ε/La0.4Ce0.6O2 electrolyte-supported cells, SOFCs with anodes containing GDC and higher amounts of Pd demonstrated higher maximum power densities and lower anode polarization resistances compared to cells with GDC-free, lower Pd content anodes. While the Pd is important to improve the anode performance, the results indicate that cycling does not lead to simple dissolution/exsolution into the perovskite, instead many other phases are present while a limited amount of Pd was actually observed in the perovskite.

Original languageEnglish
Pages (from-to)90-105
Number of pages16
JournalSolid State Ionics
Volume296
DOIs
Publication statusPublished - Nov 15 2016

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cell anodes
Phase behavior
solid oxide fuel cells
Solid oxide fuel cells (SOFC)
Perovskite
Anodes
anodes
palladium
Palladium
perovskites
cycles
dissolving
catalysts
Dissolution
cells
regeneration
strontium
radiant flux density
stoichiometry
Strontium

Keywords

  • Electrochemical impedance spectroscopy (EIS)
  • Perovskite
  • Solid oxide fuel cell
  • Transmission electron microscope (TEM), scanning transmission electron microscope (STEM), X-ray diffraction (XRD)

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Redox and phase behavior of Pd-substituted (La,Sr)CrO3 perovskite solid oxide fuel cell anodes. / Zenou, Victor Y.; Fowler, Daniel E.; Gautier, Romain; Barnett, Scott A.; Poeppelmeier, Kenneth R; Marks, Laurence D.

In: Solid State Ionics, Vol. 296, 15.11.2016, p. 90-105.

Research output: Contribution to journalArticle

Zenou, Victor Y. ; Fowler, Daniel E. ; Gautier, Romain ; Barnett, Scott A. ; Poeppelmeier, Kenneth R ; Marks, Laurence D. / Redox and phase behavior of Pd-substituted (La,Sr)CrO3 perovskite solid oxide fuel cell anodes. In: Solid State Ionics. 2016 ; Vol. 296. pp. 90-105.
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AU - Zenou, Victor Y.

AU - Fowler, Daniel E.

AU - Gautier, Romain

AU - Barnett, Scott A.

AU - Poeppelmeier, Kenneth R

AU - Marks, Laurence D.

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AB - The use of palladium and strontium in LaCrO3 perovskites for solid oxide fuel cell anodes is known to lead to improved performance, in part due to the formation of palladium at the surface under reducing conditions that can act as a catalyst, with regeneration of the catalyst possible by cycling between oxidizing and reducing conditions. Whether this cycling involves dissolution and exsolution of the palladium into the perovskite is unclear. We describe a detailed analysis of the perovskites La0.8Sr0.2Cr1 − xPdxO3 − δ (LSCrPd, nominal stoichiometry x = 0.1 and 0.2) under reducing and oxidizing conditions. A LSCrPd perovskite was found to be the main phase, further confirmed by transmission electron microscopy. Secondary phases including metallic Pd, PdO, and La4PdO7, as well as SrCrO4, were also present. Some phases, such as PdO, SrCrO4, and La4PdO7, were no longer present following reduction while other phases such as metallic Pd and La2O3, were found in increasing amounts. When used as active solid oxide fuel cell anode layers both with and without Gd0.1Ce0.9O2 − β (GDC) in La0.9Sr0.1Ga0.8Mg0.2O3 − ε/La0.4Ce0.6O2 electrolyte-supported cells, SOFCs with anodes containing GDC and higher amounts of Pd demonstrated higher maximum power densities and lower anode polarization resistances compared to cells with GDC-free, lower Pd content anodes. While the Pd is important to improve the anode performance, the results indicate that cycling does not lead to simple dissolution/exsolution into the perovskite, instead many other phases are present while a limited amount of Pd was actually observed in the perovskite.

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KW - Transmission electron microscope (TEM), scanning transmission electron microscope (STEM), X-ray diffraction (XRD)

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