skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Synchrotron X-ray studies of model SOFC cathodes, part II: Porous powder cathodes

Abstract

Infiltrated La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) sintered porous powder cathodes for solid oxide fuel cells have been investigated by synchrotron ultra-small angle x-ray scattering (USAXS). We demonstrated that atomic layer deposition (ALD) is the method for a uniform coating and liquid-phase infiltration for growing nanoscale particles on the porous LSCF surfaces. The MnO infiltrate, grown by ALD, forms a conformal layer with a uniform thickness throughout the pores evidenced by USAXS thickness fringes. The La0.6Sr0.4CoO3 (LSC) and La2Zr2O7 (LZO) infiltrates, grown by liquid-phase infiltration, were found to form nanoscale particles on the surfaces of LSCF particles resulting in increased surface areas. Impedance measurements suggest that the catalytic property of LSC infiltrate, not the increased surface area of LZO, is important for increasing oxygen reduction activities.

Authors:
; ORCiD logo; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1411042
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Solid State Ionics; Journal Volume: 311; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Chang, Kee-Chul, Ingram, Brian, Ilavsky, Jan, Lee, Shiwoo, Fuoss, Paul, and You, Hoydoo. Synchrotron X-ray studies of model SOFC cathodes, part II: Porous powder cathodes. United States: N. p., 2017. Web. doi:10.1016/j.ssi.2017.10.001.
Chang, Kee-Chul, Ingram, Brian, Ilavsky, Jan, Lee, Shiwoo, Fuoss, Paul, & You, Hoydoo. Synchrotron X-ray studies of model SOFC cathodes, part II: Porous powder cathodes. United States. doi:10.1016/j.ssi.2017.10.001.
Chang, Kee-Chul, Ingram, Brian, Ilavsky, Jan, Lee, Shiwoo, Fuoss, Paul, and You, Hoydoo. 2017. "Synchrotron X-ray studies of model SOFC cathodes, part II: Porous powder cathodes". United States. doi:10.1016/j.ssi.2017.10.001.
@article{osti_1411042,
title = {Synchrotron X-ray studies of model SOFC cathodes, part II: Porous powder cathodes},
author = {Chang, Kee-Chul and Ingram, Brian and Ilavsky, Jan and Lee, Shiwoo and Fuoss, Paul and You, Hoydoo},
abstractNote = {Infiltrated La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) sintered porous powder cathodes for solid oxide fuel cells have been investigated by synchrotron ultra-small angle x-ray scattering (USAXS). We demonstrated that atomic layer deposition (ALD) is the method for a uniform coating and liquid-phase infiltration for growing nanoscale particles on the porous LSCF surfaces. The MnO infiltrate, grown by ALD, forms a conformal layer with a uniform thickness throughout the pores evidenced by USAXS thickness fringes. The La0.6Sr0.4CoO3 (LSC) and La2Zr2O7 (LZO) infiltrates, grown by liquid-phase infiltration, were found to form nanoscale particles on the surfaces of LSCF particles resulting in increased surface areas. Impedance measurements suggest that the catalytic property of LSC infiltrate, not the increased surface area of LZO, is important for increasing oxygen reduction activities.},
doi = {10.1016/j.ssi.2017.10.001},
journal = {Solid State Ionics},
number = C,
volume = 311,
place = {United States},
year = 2017,
month =
}
  • We present synchrotron x-ray investigations of thin film La 0.6Sr 0.4Co 0.2Fe 0.8O 3-δ (LSCF) model cathodes for solid oxide fuel cells, grown on electrolyte substrates by pulse laser deposition, in situ during half-cell operations. We observed dynamic segregations of cations, such as Sr and Co, on the surfaces of the film cathodes. The effects of temperature, applied potentials, and capping layers on the segregations were investigated using a surfacesensitive technique of total external reflection x-ray fluorescence. We also studied patterned thin film LSCF cathodes using high-resolution micro-beam diffraction measurements. We find chemical expansion decreases for narrow stripes. This suggestsmore » the expansion is dominated by the bulk pathway reactions. The chemical expansion vs. the distance from the electrode contact was measured at three temperatures and an oxygen vacancy activation energy was estimated to be ~1.4 eV.« less
  • The structure of 14 compounds in the series Ba{sub 2}LnTaO{sub 6} have been examined using synchrotron X-ray diffraction and found to undergo a sequence of phase transitions from I2/m monoclinic to I4/m tetragonal to Fm3-bar m cubic symmetry with decreasing ionic radii of the lanthanides. Ba{sub 2}LaTaO{sub 6} is an exception to this with variable temperature neutron diffraction being used to establish that the full series of phases adopted over the range of 15-500 K is P2{sub 1}/n monoclinic to I2/m monoclinic to R3-bar rhombohedral. The chemical environments of these compounds have also been investigated and the overbonding to themore » lanthanide cations is due to the unusually large size for the B-site in these perovskites. - Graphical abstract: The evolution of the structure across the series of double perovskites Ba{sub 2}LnTaO{sub 6} is established using a combination of synchrotron X-ray and neutron diffraction. The symmetry increases from monoclinic to tetragonal and then cubic as the size of the lanthanide decreases.« less
  • This study is to complement an early report (the manuscript is attached for review purpose) on the role of interlayer on activity and performance stability in praseodymium nickelates. The aforementioned report showed a remarkable 48% increase in power density while switching from common GDC interlayer to a new interlayer chemistry (PGCO). Furthermore, a stable long-term performance was linked with suppressed reaction between the cathode and PGCO interlayer. In this article, we report in situ studies of the phase evolution. The high energy XRD studies at a synchrotron source showed fully suppressed phase transition in praseodymium nickelates with PGCO interlayer, whilemore » the electrodes on the GDC interlayer undergo substantial phase transformation. Furthermore, in operando and post-test XRD analyses shown fully suppressed structural changes in electrodes operated in full cells at 750°C and 0.80 V for 500 hours. SEM-EDS analysis showed that the formation of PrO x at the cathode-interlayer interface may play a role in a decrease of mechanical integrity of the interfaces, due to thermal expansion mismatch, leading to a local stress between the two phases. Furthermore, phase evolution at a narrow interface may propagate toward the electrode bulk, leading to structural changes Q1 and performance degradation.« less
  • This study details subtle compositional modifications (marginal A-site deficiencies and Cu B-site dopant additions) to a La0.8Sr0.2FeO3 (LSF-20) cathode material to enhance sintering below 1000 C. The interaction of the modified LSF-20 compounds with YSZ below 1000 C was also investigated. Initial single cell studies utilizing a (La0.8Sr0.2)0.98Fe0.98Cu0.02O3 cathode material on an anode supported YSZ cell have indicated power densities in the range 1.35-1.75 W/cm2 at 750 C and 0.7V.