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Fuel electrode for solid electrolyte fuel cells and a method for manufacture of the electrode

a fuel cell and solid electrolyte technology, applied in the direction of electrolytes, cell components, electrochemical generators, etc., can solve the problems of complex overall manufacturing process, degrading electrode, exfoliation of electrode, etc., and achieves excellent electrode performance, low manufacturing cost, and profitable commercial application.

Inactive Publication Date: 2005-08-11
OSAKA GAS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides an improved fuel electrode for high-temperature solid electrolyte fuel cells that does not undergo sintering or aging even after continuous operation for a long time at a high temperature. The electrode is made of a porous element composed of a high melting point metal having a melting point of not less than 1,900° C. The preferred metals are ruthenium, osmium, rhodium, and iridium, with ruthenium being the most advantageous due to its high stability, low cost, and high catalyst activity for steam reforming. The electrode can be manufactured by dissolving or dispersing a powder of the metal or metal chloride in an organic solvent or water, coating the electrode material with the solution or dispersion, sintering it, and then reducing it. The electrode has substantially no sintering and low reaction, diffusion, and resistance polarization values. The manufacturing process is simple and cost-effective. The use of a high molecular weight compound soluble in the organic solvent or water facilitates porosity control and handling.

Problems solved by technology

However, the Ni / ZrO2 cermet electrode manufactured by the first-mentioned process is disadvantageous in that when the fuel cell is run over thousands of hours at temperatures near 1,000° C., the Ni grains therein are sintered thus degrading the electrode and ultimately causing exfoliation of the electrode.
The Ni / ZrO2 cermet manufactured by the second process is resistant to sintering and insures a satisfactory electrode performance, but, since it involves an EVD step, the overall manufacturing process is complicated and the cost of manufacture is increased.
The porous platinum electrode is disadvantageous in that the platinum reacts with the impure metal in the fuel and is vaporized in a continuous operation in a reducing atmosphere resulting in early aging of the electrode.
Furthermore, platinum is an expensive metal and the manufacture of porous platinum electrodes is costly.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0030] In 89 parts by weight of n-butanol were dissolved 10 parts by weight of hydrous ruthenium trichloride (RuCl3.3H2O) and 1 part by weight of polybutyl alcohol, and pellets (2 cm in diameter and 0.2 mm thick) of yttria-doped zirconia (ZrO2 containing 8 mol % of Y2O3; hereinafter referred to as YSZ) were coated with the resulting solution. The coated pellets were heated in air at 850° C., and then reduced in a H2 atmosphere at 1,000° C. to provide a porous electrode having a thickness of 50 μm. Using this as the fuel electrode, a fuel cell was fabricated and a fuel gas composed of 90 vol. % of H2 and 10 vol. % of H2O and air were passed to the fuel electrode and an air electrode, respectively, to investigate the polarization characteristics at 200 mA / cm2. As a result, all the reaction, diffusion and resistance polarization values were not larger than 5 mV. The same fuel electrode was maintained in H2 streams at 1,000° C. for 1,315 hours and similar determinations were made. As a ...

example 2

[0031] To 30 parts by weight of a 5% aqueous solution of polyvinyl alcohol were added 70 parts by weight of powdery ruthenium metal (particle size 1 to 5 μm) followed by thorough mixing. Then, YSZ pellets were coated with the resulting slurry. The coated pellets were heated in the air at 500° C. (for removal of the binder), and then were reduced in streams of a gas composed of 5 vol. % of H2 and 95 vol. % of N2 at 1,050° C. to provide a porous electrode having a thickness of 50 μm. The performance of this electrode was comparable to that of the electrode obtained in Example 1.

example 3

[0032] In 89 parts by weight of water were dissolved 10 parts by weight of hydrous ruthenium trichloride and 1 part by weight of polyvinyl alcohol. YSZ pellets were coated with the resulting solution and, thereafter, the procedure described in Example 2 was repeated to provide an electrode. The performance of this electrode was comparable to that of the electrode obtained in Example 1.

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Abstract

The invention relates to a fuel electrode for high-temperature solid electrolyte fuel cells and a process for manufacture of the electrode. The fuel electrode of the invention is a porous element composed of a high-melting metal, such as ruthenium, osmium, rhodium or iridium, or an alloy containing the metal. The process for manufacture of the fuel electrode comprises coating an electrode material with a solution or dispersion of the high-melting metal and / or its chloride, sintering the same and finally reducing the product.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a fuel electrode for high-temperature solid electrolyte fuel cells and a method of manufacturing the electrode. [0002] Heretofore, nickel / zirconia (Ni / ZrO2) cermets have been employed for fuel electrodes in commercialized high-temperature solid electrolyte fuel cells. [0003] These Ni / ZrO2 cermets are typically produced by the below alternative processes. [0004] (1) A process in which NiO / ZrO2 is sintered and then reduced to provide a Ni / ZrO2 cermet, (e.g. the Ceramatec process described in Proceedings of SOFC-NAGOYA, p.24); and [0005] (2) A process, known as the Westinghouse process, in which ZrO2 in a crude Ni / ZrO2 cermet is caused to grow into spaces between Ni grains by the EVD technique, (Japanese Kokai Patent Publication No. 6I-153280). [0006] Aside from the above, porous platinum (Pt) materials obtainable by sintering platinum pastes have been used in ZrO2 sensors and the like or in basic research. [0007] Howe...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M4/86H01M4/88H01M4/92H01M8/12
CPCH01M4/8807H01M4/8842H01M4/8882H01M4/8885H01M4/905H01M4/92Y10T29/49108H01M2008/1293H01M2300/0074Y02E60/525Y02E60/50Y10T29/49115H01M2004/8684
Inventor IPPOMMATSU, MASAMICHISUZUKI, MINORUSASAKI, HIROKAZUOTOSHI, SHOJIOHNISHI, HISAO
Owner OSAKA GAS CO LTD