Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
  • H01M4/9025—Oxides specially used in fuel cell operating at high temperature, e.g. SOFC
  • H01M4/9033—Complex oxides, optionally doped, of the type M1MeO3, M1 being an alkaline earth metal or a rare earth, Me being a metal, e.g. perovskites
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the invention relates to an electrode
• Perovskite base with solid electrolyte contact which is particularly suitable for high-temperature fuel cells.
• Solid electrolyte fuel cells usually operate at operating temperatures of around 950 to 1000 ° C. The aim is to lower the operating temperature to approximately 800 ° C.
• ZrO2 (YsZ) stabilized with Y 2 O 3 is generally used as the solid electrolyte.
• the solid electrolyte which in the classic concept also serves as a substrate support and usually has a thickness of 100 to 150 ⁇ m, is coated on both sides with different materials as electrodes (see Fig. 1): Perovskites such as (La 1-x Sr x ) MnO 3 applied, as an anode a Ni / ZrO 2 cermet.
• the aim of the invention is therefore to reduce the chemical interactions between the perovskites serving as electrodes and the solid electrolyte and, if appropriate, to improve the electrochemical properties of the electrodes. This goal is achieved by inhibiting platinum metal doping in the perovskite adjacent to the electrolyte.
• doped electrodes additionally show improved electrochemical properties.
• the doping amounts useful here can go up to over 1%, but are expediently chosen in the range from 10 to 10 3 ppm.
• platinum metals iridium and ruthenium are preferred, which are absorbed by the perovskite in particular in oxidic form.
• the doping can vary over the total volume of the
• platinum metals with high oxide vapor pressure e.g.
• the perovskite e.g. in air or another oxygen-containing atmosphere at elevated temperatures (approx. 600 - 1000 ° C) exposed to the access of the oxide vapor for long periods.
• the desired doping can be achieved by impregnation and heat treatment or by suitable additives already during electrode manufacture.
• perovskite cathodes of high-temperature fuel cells particular attention is paid to the perovskite cathodes of high-temperature fuel cells, but a perovskite provided for the anode can also be doped with platinum metal according to the invention.
• the doping according to the invention is useful for types of perovskite and mixtures such as are provided for fuel cells, such as for example perovskite based on LaMnO 3 , LaCoO 3 , LaFeO 3 ⁇ , LaCrO 3, etc.
• Perovskites based on lanthanum ferrite were examined in particular. Y 2 O 3 -containing ZrO 2 materials are widely used as the solid electrolyte.
• the reduction in reactivity of perovskite electrodes by platinum metal doping can, of course, also be used with other oxide masses serving as solid electrolyte, such as mixed oxides based on Gd, Ce-based and doped BaCeO 3 .
• the invention is not limited to fuel cells, but can be used in all cases of boundary layer structures operated at elevated temperatures, in which material of the perovskite type and high-temperature-resistant oxide materials in particular
• perovskites e.g.
• FIG. 1 shows a diagram for an electrode / electrolyte arrangement of fuel cells
• FIG. 2 shows a graph for the SrZrO 3 formation in a powder mixture of YsZ and perovskite
• Figure 3 is an x-ray diagram for
• Figure 4 is a graph for the cell volume
• Perovskite powders of different compositions were loaded for 48 h or 121 h at 900 ° C together with iridium sheet in air via the gas phase.
• the samples pretreated in this way were mixed with the electrolyte material 8YsZ (with 8 mol% Y2O3 stabilized ZrO 2 ) in equimolar proportions, pressed into pellets and annealed or aged at 1000 ° C. for different times.
• the formation of reaction products (SrZrO 3 or CaZrO 3 ) after 25 h or 48 h exposure was determined with the aid of X-ray diffraction images.
• the results are summarized in Table 1. As can be seen, the samples doped with iridium show a much lower tendency to react with the electrolyte than that untreated samples.
• the time course of the SrZrO 3 formation is plotted in FIG. 2, which clearly shows the difference.
• a perovskite with the composition (La 0.6 Sr 0.4 ) 0.9 Fe 0.8 Co 0.2 O 3- ⁇ was chosen as the starting material, which was calcined for 48 h at 900 ° C in an oxygen atmosphere.
• two samples of the same composition were "outsourced” in the same oxygen atmosphere in the presence of iridium at 900 ° C for 48 h or 121 h.
• the nitrates of the corresponding metal components of the perovskite and Ir (III) oxide (Ir 2 O 3 ) served as starting materials. All components were homogenized in an aqueous solution, dried and then stored in air at 1200 ° C. for 48 h in order to build up the perovskite grid. With the help of a parallel iridium determination using neutron activation analysis and
• the iridium content could be determined to be about 200 ppm in both cases.
• the perovskite obtained was mixed in an equimolar ratio with YsZ, pressed into pellets and aged at 1000 ° C for 72 hours. The result is shown in Tab. 1.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Inert Electrodes (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1994
  • 1994-01-11 DE DE4400540A patent/DE4400540C2/de not_active Expired - Fee Related
• 1995
  • 1995-01-10 EP EP95905046A patent/EP0739543A1/de not_active Withdrawn
  • 1995-01-10 US US08/682,508 patent/US5824429A/en not_active Expired - Fee Related
  • 1995-01-10 WO PCT/DE1995/000026 patent/WO1995019053A1/de not_active Application Discontinuation
  • 1995-01-10 JP JP7518270A patent/JPH09507335A/ja active Pending
  • 1995-01-10 AU AU13821/95A patent/AU694471B2/en not_active Ceased
• 1996
  • 1996-07-10 NO NO962900A patent/NO962900L/no unknown

Non-Patent Citations (1)

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