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Title: Ceria Nano-coating for Sulfur Tolerant Ni-based Anodes of SolidOxide Fuel Cells

Authors:
; ; ; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE
OSTI Identifier:
926602
Report Number(s):
LBNL-62689
R&D Project: M30012; BnR: 600301020
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Electrochemical and Solid-State Letters; Journal Volume: 10; Journal Issue: 9; Related Information: Journal Publication Date: 2007
Country of Publication:
United States
Language:
English
Subject:
36

Citation Formats

Kurokawa, Hideto, Sholklapper, Tal Z., Jacobson, Craig P., DeJonghe, Lutgard C., and Visco, Steven J. Ceria Nano-coating for Sulfur Tolerant Ni-based Anodes of SolidOxide Fuel Cells. United States: N. p., 2007. Web. doi:10.1149/1.2748630.
Kurokawa, Hideto, Sholklapper, Tal Z., Jacobson, Craig P., DeJonghe, Lutgard C., & Visco, Steven J. Ceria Nano-coating for Sulfur Tolerant Ni-based Anodes of SolidOxide Fuel Cells. United States. doi:10.1149/1.2748630.
Kurokawa, Hideto, Sholklapper, Tal Z., Jacobson, Craig P., DeJonghe, Lutgard C., and Visco, Steven J. Thu . "Ceria Nano-coating for Sulfur Tolerant Ni-based Anodes of SolidOxide Fuel Cells". United States. doi:10.1149/1.2748630.
@article{osti_926602,
title = {Ceria Nano-coating for Sulfur Tolerant Ni-based Anodes of SolidOxide Fuel Cells},
author = {Kurokawa, Hideto and Sholklapper, Tal Z. and Jacobson, Craig P. and DeJonghe, Lutgard C. and Visco, Steven J.},
abstractNote = {},
doi = {10.1149/1.2748630},
journal = {Electrochemical and Solid-State Letters},
number = 9,
volume = 10,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • A Ca- and Co-doped yttrium chromite (YCCC) - samaria-doped ceria (SDC) composite was studied in relation to a potential use as a solid oxide fuel cell (SOFC) anode material. Tests performed using the yttria-stabilized zirconia (YSZ) electrolyte-supported cells revealed that the electrocatalytic activity of the YCCC-SDC anode towards hydrogen oxidation at 800 C was comparable to that of the Ni-YSZ anode. In addition, the YCCC-SDC anode exhibited superior sulfur tolerant characteristics showing less than 10% increase in a polarization resistance, fully reversible, upon exposure to 20 ppm H2S at 800 C. No performance degradation was observed during multiple reduction-oxidation (redox)more » cycles when the anode was intentionally exposed to the air environment followed by the reduction in hydrogen. The redox tolerance of the YCCC-SDC anode was attributed to the dimensional and chemical stability of the YCCC exhibiting minimal isothermal chemical expansion upon redox cycling.« less
  • In this study the performance of CeO{sub 2} and Rh supported on CeO{sub 2} as anodes in solid oxide fuel cells (SOFC) was investigated. Experiments were conducted using a model SOFC consisting of an electrolyte disk of yttria-stabilized zirconia with thin films of samaria-doped ceria as both the anode and cathode. The current-voltage characteristics of the cell were measured for H{sub 2}, CO, and CH{sub 4} fuels as a function of the thickness of the CeO{sub 2} anode and the Rh loading. For H{sub 2} as the fuel, it was found that the cell performance was largely independent of themore » anode design, suggesting that, for this fuel, reaction on the anode was not limiting. In contrast, for CH{sub 4}, it was observed that the maximum current density produced by the cell was highly dependent on both the CeO{sub 2} film thickness and the Rh loading. This suggests that for CH{sub 4} the catalytic properties of the anode are important for good performance. Since during the CH{sub 4} experiments only negligible amounts of H{sub 2}O were produced (the fractional conversion was maintained below 10{sup -5}), this study also demonstrated that it is possible to oxidize CH{sub 4} electrochemically in a SOFC without prior steam reforming. The implications of these results to the design of practical SOFCs are discussed. 24 refs., 5 figs.« less
  • In order to enhance gas-diffusion rates in a mixed-conducting samaria-doped ceria (SDC) anode, micrometer-sized pores were prepared by sintering a SDC paste containing fine polymer beads (d = 1.2 {micro}m) coated on an yttria-stabilized zirconia electrolyte. SDC anodes prepared under different conditions were examined to determine their pore-size distribution, pore volume, ohmic resistance, polarization behavior, and morphological structure. Both the anodic overpotential and the ohmic resistance of SDC anodes were lowered appreciably by controlling their microstructures. The performance of a SDC anode with optimized microstructure was enhanced further with highly dispersed Ru catalysts at 3 wt % loading, especially atmore » low operating temperatures at about 800 C. The current density on a Ru-SDC anode at an overpotential of 0.1 V was 0.5 A/cm{sup 2} at 800 C.« less
  • The polarization behaviors of porous samaria-doped ceria anodes coupled with zirconia electrolytes with various ionic conductivities ({sigma}{sub ion}) were investigated. The exchange current density, j{sub 0}, on such mixed-conducting SDC anodes was not influenced by the {sigma}{sub ion} at 900 and 1,000 C, whereas j{sub 0} increased proportionally to {sigma}{sub ion} at a lower temperature of 800 C. However, the dispersion of nanometer-sized ruthenium catalysts on SDC particles resulted in an increase of j{sub 0} with increase in {sigma}{sub ion} in the entire temperature range between 800 and 1,000 C. The observations are well explained kinetically, i.e., the anode performancemore » is controlled by the rate of O{sup 2{minus}} supply to the anode layer via the electrolyte, as the anodic reaction rate becomes sufficiently high due to highly dispersed Ru electrocatalysts. Consequently, it is clear that the use of high-performance electrodes in combination with the solid electrolyte having high {sigma}{sub ion} is a prerequisite to achieving high performance of solid oxide fuel cells.« less
  • Polarization properties of ceria-based anodes dispersed with nanometer-sized Ru catalysts, which the authors developed for medium-temperature solid oxide fuel cells, were greatly improved by controlling the composition and microstructure. Among samaria-doped ceria (SDC) anodes with compositions of (CeO{sub 2}){sub 1{minus}x}(SmO{sub 1.5}){sub x} (0 {le} x {le} 0.4) a SDC anode with x = 0.2 was found to exhibit the maximum current density at a given overpotential at temperatures of 800 to 1,000 C, when operating under a hydrogen atmosphere. This high current density is a direct result of improved conductivities of both oxide ions ({sigma}{sub ion}) and electrons ({sigma}{sub e}).more » Attaching a very thin film of SDC onto a yttria-stabilized zirconia electrolyte before coating the Ru-dispersed SDC layer appreciably lowered the anodic overpotential for the SDC. The current densities on the improved Ru-SDC anode at a potential of {minus}0.9 V vs. an air reference electrode were 0.8 and 1.4 A/cm{sup 2} at 800 and 900 C, respectively.« less