WO2011036729A1 - Solid oxide fuel cell - Google Patents

Solid oxide fuel cell Download PDF

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Publication number
WO2011036729A1
WO2011036729A1 PCT/JP2009/004904 JP2009004904W WO2011036729A1 WO 2011036729 A1 WO2011036729 A1 WO 2011036729A1 JP 2009004904 W JP2009004904 W JP 2009004904W WO 2011036729 A1 WO2011036729 A1 WO 2011036729A1
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Prior art keywords
fuel electrode
catalyst
electrode
region
oxide
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PCT/JP2009/004904
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French (fr)
Japanese (ja)
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長田憲和
深澤孝幸
首藤直樹
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株式会社 東芝
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Priority to PCT/JP2009/004904 priority Critical patent/WO2011036729A1/en
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    • 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
    • H01M4/8636—Inert electrodes with catalytic activity, e.g. for fuel cells with a gradient in another property than porosity
    • H01M4/8642—Gradient in composition
    • 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
    • H01M4/8605—Porous electrodes
    • H01M4/8621—Porous electrodes containing only metallic or ceramic material, e.g. made by sintering or sputtering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M2008/1293—Fuel cells with solid oxide electrolytes
    • 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 present invention relates to a solid oxide fuel cell (SOFC), and particularly to an improved fuel electrode for SOFC.
  • SOFC solid oxide fuel cell
  • the solid oxide fuel cell can obtain a sufficient reaction rate without using an expensive noble metal catalyst due to its high operating temperature (700-1000 ° C), and compared with other types of fuel cells. As the power generation efficiency is the highest and the generation of CO 2 is small, it is expected as a next-generation clean power generation system.
  • a cermet material which is a mixed sintered body of metal particles having electronic conductivity and ceramic particles having ionic conductivity or mixed electron / ion conductivity is used for a general fuel electrode.
  • the metal used as the electrode catalyst also serves as an electron conduction path in the electrode, so the metal particles need to have a certain size.
  • the contributing three-phase interface is limited and it is difficult to improve the catalytic activity. For this reason, in order to improve the characteristics of the fuel electrode, it is necessary to increase the ion and electron conductivity in the electrode and to increase the surface area of the catalyst particles.
  • the metal particles near the electrolyte mainly function as an electrode catalyst, and the metal particles function as an electronic conduction path as they approach the surface of the fuel electrode.
  • the cermet material is used in this two-layer structure electrode, and the particle size of the metal particles used for the catalyst cannot be made very small, so that the catalytic activity is low and a significant improvement in characteristics cannot be expected.
  • the object of the present invention is to improve the catalytic activity in the solid oxide fuel cell.
  • the solid electrolyte fuel cell of the present invention is a solid oxide type comprising a sintered body of a metal catalyst or a catalyst particle comprising a metal catalyst-carrying metal oxide carrying a metal catalyst and an electron / ion mixed conductive particle.
  • a solid oxide fuel cell having a fuel cell anode The concentration of the catalyst in the fuel electrode is non-uniform in the direction perpendicular to the surface of the fuel electrode, and in the fuel electrode central region disposed between the electrolyte vicinity region and the fuel electrode surface vicinity region of the fuel electrode.
  • the catalyst concentration has a maximum value.
  • the anode activity of the solid oxide fuel cell can be improved, and the output of the solid oxide fuel cell can be increased.
  • FIG. 1 is a schematic sectional view of a solid oxide fuel cell (SOFC) fuel electrode according to a first embodiment of the present invention.
  • FIG. 2 is a schematic cross-sectional view of an SOFC fuel electrode having a catalyst concentration distribution in the fuel electrode using a reduction precipitation catalyst.
  • FIG. 3 is a diagram illustrating a manufacturing process of the fuel electrode according to the present embodiment.
  • SOFC solid oxide fuel cell
  • the fuel electrode material for a solid oxide fuel cell and the method for manufacturing the fuel electrode according to the present invention will be described, but the present invention is not limited to the following embodiments and examples.
  • the schematic diagram referred in the following description is a figure which shows the positional relationship of each structure, The ratio of the magnitude
  • Embodiments described herein relate generally to a fuel electrode and a solid oxide fuel cell using the same.
  • the SOFC is formed by laminating a fuel electrode material layer 12 on one surface and an oxygen electrode material layer 13 on the other surface with a solid oxide electrolyte plate 11 interposed therebetween.
  • Oxygen ions (O 2 ⁇ ) dissociated in the oxygen electrode material layer 13 move to the fuel electrode material layer 12 through the solid oxide electrolyte 11 and react with hydrogen to generate water.
  • the electrons generated at this time are taken out through an external circuit and used for power generation.
  • Ln rare earth element
  • A Sr, Ca, Ba
  • B At least one of Cr, Mn, Fe, Co, and Ni
  • x is 0 to 1
  • ⁇ in the above formula means that there is a defect in the oxygen atom
  • Consists of These complex oxides dissociate oxygen efficiently and have electronic conductivity. It is also possible to compensate for the ionic conductivity that is slightly insufficient with the composite oxide by adding an ionic conductive oxide together.
  • Sm 2 O 3 CeO 2 doped with, or Gd 2 O 3 CeO 2 doped with, Y 2 O 3 is used any one of the doped CeO 2 a.
  • These show mixed conductivity of electrons and ions in a reducing atmosphere, but only show high ionic conductivity in an oxygen-containing atmosphere, and are represented by the general formula Ln 1-x A x BO 3- ⁇ . It does not react with oxides showing mixed conductivity.
  • Ni—Al-based and Ni—Mg-based composite oxides The performance of composite electrodes with conductive particles has been demonstrated (see Japanese Patent Application Laid-Open Nos. 2009-64640 and 2009-64641).
  • Ni-Al-based and Ni-Mg-based composite oxides are reduced at high temperatures to form Ni particle-supported aluminum composite oxide / Ni particle-supported magnesium composite oxide on Al-based and Mg-based oxide substrates.
  • Ni fine particles can be formed, and the deposited Ni fine particles have a nanometer size, so that a large catalyst surface area can be obtained with a small amount of catalyst.
  • metal particles are produced as precipitates from the composite oxide during reduction, they are immobilized on the substrate, and the metal particles are hardly sintered even in a high-temperature reducing atmosphere.
  • the volume of the insulating substrate is larger than the volume of the deposited metal fine particles, the ohmic resistance in the fuel electrode layer is increased when forming an electrode.
  • the fuel electrode is formed by using the metal catalyst-supported oxide particles such as the Ni particle-supported aluminum oxide or the Ni particle-supported magnesium oxide and the electron / ion mixed conductive particles in combination.
  • the mixing ratio of the Ni particle-supported aluminum oxide or Ni particle-supported magnesium oxide and the electron / ion mixed conductive particles in the fuel electrode is changed.
  • the amount of the electron / ion mixed conductive particles 16 is increased in the fuel electrode surface vicinity region 18 and the electrolyte vicinity region 20, and Ni particle-supported aluminum composite oxide or Ni particle-supported magnesium composite oxidation is provided in the fuel electrode center region.
  • a fuel electrode central region 19 having a maximum catalyst concentration with an increased amount 17 is provided (FIG. 2).
  • the electron / ion mixed conductive particles 16 in the electrolyte vicinity region 20 mainly function as an ionic conductor
  • the electron / ion mixed conductive particles 16 in the surface vicinity portion 18 mainly function as an electron conductor. That is, the oxide ions (O 2 ⁇ ) generated at the oxygen electrode 13 can smoothly move through the solid oxide electrolyte 11 to the vicinity of the electrolyte 20, and the transferred oxygen ions (O 2 ⁇ ) Activated by many catalysts in the pole center region 19 and efficiently reacts with water vapor and electrons, and the generated electrons are transported to the current collector 21 through the fuel electrode surface vicinity region 18. Thereby, in addition to smooth conduction of electrons and ions in the fuel electrode, the catalyst can be used effectively, so that the fuel electrode characteristics are improved.
  • the metal catalyst-supported oxide particles used in the fuel electrode in the present embodiment are prepared by reducing a composite oxide that is a precursor containing a catalyst metal and an element constituting the metal oxide that supports the catalyst metal.
  • the metal catalyst-supported oxide particles can be used. Specifically, the Ni component in the Ni—Al composite oxide particles (NiAl 2 O 4 composite oxide) is precipitated on the surface by reduction, and the base material becomes aluminum oxide (mainly Al 2 O 3 ). That is, Ni particle carrying Al 2 O 3 is formed.
  • the size of the metal fine particles thus formed is generally several tens of nm. In order to perform an active catalytic function, the size of the metal fine particles is preferably about 5 nm to 500 nm.
  • a particle having a size of 5 nm or less is actually difficult to produce, and if the particle size is 500 nm or more, adjacent particles may be bonded to each other and may have the same problem as conventional NiO reduced.
  • a more preferable size for the catalyst is about 20 nm to 100 nm. Since this size is one to two orders of magnitude smaller than the conventional electrode catalyst size, an improvement in catalyst activity is expected. For this reason, the amount of NiAl 2 O 4 to be added is preferably in the range of 5 wt% to 80 wt% of the entire material constituting the electrode. More preferably, it is 10 to 50 weight%.
  • the particulate material having electron-ion mixed conductivity used in the fuel electrode CeO 2 doped with CeO 2 or Gd 2 O 3 doped with Sm 2 O 3, or a Y 2 O 3 doped and CeO 2 can be used with, without being limited thereto, as long as it has a high oxygen ion conductivity and electronic conductivity at 400 ° C. or higher 1000 ° C. or less.
  • CeO 2 doped with 10 to 50 mol% Sm 2 O 3 , Gd 2 O 3 , or Y 2 O 3 is preferable. (See J. Appl. Electrochem., 18, 527 (1988).).
  • the mixing ratio of the substances constituting the fuel electrode material layer is preferably set in the following range.
  • a range of ⁇ 9 is preferred. The reason is that it is necessary to produce a sufficient network of electron / ion conductive oxide particles.
  • the amount of the catalyst-supporting metal oxide is larger than the region near the fuel electrode surface and the region near the solid electrolyte, and it is necessary not to cut the network between the ion conductive oxide particles.
  • the reason is that it is necessary to produce a sufficient network of electron / ion conductive oxide particles.
  • the electrolyte vicinity region 20 indicates a region of the fuel electrode material layer having a thickness of 1/3 from the surface of the solid electrolyte plate 11 in the fuel electrode material layer 12, and the fuel electrode surface vicinity region 18. Similarly, the region of the fuel electrode material layer having a thickness of 1/3 from the surface thereof in the fuel electrode material layer.
  • the relationship between the catalyst concentration in the layer near the fuel electrode surface area 18, the catalyst concentration in the fuel electrode center area 19, and the catalyst concentration in the electrolyte vicinity area 20 is as follows. By configuring so as to be high, the effect of the present invention is achieved.
  • the fuel electrode material layer 12 may be a layer having a clearly discontinuous surface, or the fuel electrode material layer does not have a discontinuous surface whose composition changes continuously. It may be a uniform layer. In this case, the average concentration of the material composition constituting each region may satisfy the above-described conditions, or may be a configuration having a clearly maximum value in a thinner region.
  • a mesh-like current collecting wiring layer or a porous current collecting layer having high electronic conductivity may be provided between the fuel electrode current collector 21 and the fuel electrode material layer 12. This facilitates electronic conduction between the fuel electrode current collector and the fuel electrode.
  • FIG. 3 shows a method of manufacturing the fuel electrode for the fuel cell according to the present embodiment.
  • a catalyst metal particle-supported oxide precursor such as a nickel aluminum composite oxide
  • S1 the raw materials are mixed and made into a paste
  • S2 the raw materials are mixed and made into a paste
  • S3 the raw materials are mixed and made into a paste
  • S2 the raw materials are mixed and made into a paste
  • S3 the shape
  • S3 is performed
  • This process is repeated until the fuel electrode has a required thickness, and reduction is performed to reduce the catalyst metal particle-supported oxide precursor (S4).
  • S4 the catalyst metal particle-supported oxide precursor
  • NiO powder and Al 2 O 3 powder are mixed and fired to prepare a catalyst precursor made of a Ni—Al composite oxide represented by NiAl 2 O 4 , and then pulverized to obtain a Ni—Al composite oxide Precursor particles are created.
  • the composite oxide particle diameter after pulverization is preferably about 0.1 to several ⁇ m.
  • Ni—Al composite oxide precursor particles thus prepared and the electron / ion mixed conductive particles are mixed at a target ratio, and an aqueous solution of a metal salt such as nitrate is added to the target composition.
  • a paste S1 in FIG. 3
  • electron-ion mixed conductive particles Sm 2 O 3 CeO 2 was doped or CeO 2 doped with Gd 2 O 3, or uses a CeO 2 doped with Y 2 O 3, are limited to However, what is necessary is just to have high oxide ion electroconductivity and electronic conductivity in 400 degreeC or more and 1000 degrees C or less.
  • the pasted mixed powder is screen-printed on the surface of the solid electrolyte plate 11, and heated to a temperature at which the adhesive strength between the two is increased and baked (S2, S3 in FIG. 3).
  • the firing temperature is preferably in the range of 1000 ° C. to 1400 ° C.
  • the area near the fuel electrode surface 18 and the center of the fuel electrode where the ratio of the Ni—Al composite oxide particles and the electron / ion mixed conductive particles is different in each part, which is a feature of this embodiment Region 19 and electrolyte vicinity region 20 are formed.
  • the method of forming the electron / ion mixed conductive particles 16 and the Ni—Al composite oxide precursor particles is not limited to this.
  • the mixed powder may be made into a slurry by coating, dipping, or spray coating, or formed into a sheet and laminated.
  • the Ni—Al composite oxide particles and the electron / ion mixed conductive oxide particles are combined and integrated to form a network.
  • the fuel electrode material layer and the oxygen electrode material layer are preferably porous composed of open cells, and are mixed with a pore-forming material that is previously burned down to form pores.
  • pores can be effectively formed.
  • An example of the pore forming material is an organic material such as acrylic spherical particles.
  • the composite oxide represented by the formula (1) is pasted using water or an alcohol solvent, and the solid electrolyte plate 11 on the side opposite to the surface on which the fuel electrode is baked is formed. Screen printing is performed on the surface, and the temperature is raised to a temperature at which the adhesive strength between the two is increased, followed by firing. In general, it is preferable to fire in the range of 1000 ° C. to 1300 ° C.
  • particles exhibiting ionic conductivity may be mixed.
  • the particles having ion conductivity for example, SDC, GDC, YDC, or the like can be used.
  • the fuel electrode is reduced in a reducing atmosphere of 800 ° C. or higher and 1000 ° C. or lower (S4 in FIG. 3).
  • the reduction treatment of NiO is performed at about 900 ° C. so as not to raise the temperature more than necessary.
  • NiAl 2 O 4 as a main component, Ni is sufficiently precipitated, so that the reduction is performed at 900 ° C. or more. It is more preferable.
  • the reduction time is not particularly limited, but may be about 10 minutes.
  • NiAl 2 O 4 composite oxide The Ni component in the Ni—Al composite oxide precursor particles (NiAl 2 O 4 composite oxide) is deposited on the surface by the reduction, and the base material becomes aluminum oxide (mainly Al 2 O 3 ). That is, Ni particle-supported Al 2 O 3 is formed.
  • the size of the metal fine particles thus formed is generally several tens of nm. In order to perform an active catalytic function, the size of the metal fine particles is preferably about 5 nm to 500 nm. A particle having a size of 5 nm or less is actually difficult to produce, and if the particle size is 500 nm or more, adjacent particles may be bonded to each other and may have the same problem as conventional NiO reduced. A more preferable size for the catalyst is about 20 nm to 100 nm.
  • the amount of NiAl 2 O 4 to be added is preferably in the range of 5 wt% to 80 wt% of the entire material constituting the electrode. More preferably, it is 10 to 50 weight%.
  • the catalyst particle diameter to be formed is small, the amount of catalyst used in the conventional cermet type fuel electrode can be reduced even at the catalyst concentration maximum portion, and the mixed conductor portion can be made large. This makes it possible to suppress differences in thermal expansion from the solid electrolyte and differences due to matching mismatch.
  • the deposited metal particles are present only in one layer on the surface portion of the base material Al 2 O 3 , have good consistency with the base material, and have a strong bond. Therefore, it also has a feature that it does not move easily even when exposed to a high temperature reducing atmosphere.
  • the contact resistance of the fuel electrode using the composite oxide capable of fixing the fine Ni particles to the base material can be reduced, and the cell Loss can be reduced.
  • the precipitation catalyst can be used effectively, and the cell output can be improved.
  • an inexpensive manufacturing method such as screen printing and spray coating can be applied even in the electrode preparation process, and a cell can be manufactured at low cost.
  • NiO powder having an average particle diameter of about 1 ⁇ m and Al 2 O 3 powder having an average particle diameter of about 0.4 ⁇ m were mixed at a molar ratio of 1: 1, the mixed powder was press-molded, and the mixture was pressed in argon at 1300 ° C. for 5 minutes.
  • NiAl 2 O 4 composite oxide was produced by sintering for a period of time. Using a planetary ball mill, this composite oxide was pulverized until the specific surface area became 20 to 23 m 2 / g to obtain a NiAl 2 O 4 fuel electrode catalyst precursor.
  • NiAl 2 O 4 fuel electrode catalyst precursor prepared in “Preparation of Ni—Al composite oxide precursor” and SDC (Sm 0.2 Ce) having an average particle size of 0.3 ⁇ m as a sintered body having ionic conductivity. 0.8 O 2 ) particles were weighed so that the weight ratio of the pulverized particles was 10:90, 15:85, 20:80, and 30:70, respectively.
  • a fuel electrode paste was prepared by adding approximately 30% by weight of the Ce and Sm nitrate aqueous solution prepared in the above “adjustment of pasting solvent” to the mixed powder, and mixing the mixture with a high-speed rotary mixer.
  • a Pt electrode was similarly printed on the opposite surface of the YSZ electrolyte to form an oxygen electrode, and a Pt reference electrode was applied to the electrolyte side surface, followed by baking at 960 ° C. for 30 minutes.
  • the Ni paste mixed with YSZ powder Ni: YSZ is mixed so that the weight ratio is 82:18
  • a current collecting layer was laminated on the fuel electrode surface. Thereafter, heat treatment was performed at 960 ° C. for 30 minutes in an air atmosphere, and the current collecting layer was immobilized on the electrode surface.
  • a Pt electrode was similarly printed on the opposite surface of the YSZ electrolyte to form an oxygen electrode, and a Pt reference electrode was applied to the electrolyte side surface, followed by baking at 960 ° C. for 30 minutes.
  • the Ni paste mixed with YSZ powder Ni: YSZ is mixed so that the weight ratio is 82:18
  • a current collecting layer was laminated on the fuel electrode surface. Thereafter, heat treatment was performed at 960 ° C. for 30 minutes in an air atmosphere, and the current collecting layer was immobilized on the electrode surface.
  • Ni paste mixed with YSZ powder Ni: YSZ is mixed so that the weight ratio is 82:18 is printed in the same manner as the fuel electrode paste so that it overlaps exactly on the three-layer structure fuel electrode surface.
  • a current collecting layer was laminated on the fuel electrode surface. Thereafter, heat treatment was performed at 960 ° C. for 30 minutes in an air atmosphere, and the current collecting layer was immobilized on the electrode surface.
  • ⁇ Cell characteristic evaluation test> The flat plate type solid oxide electrochemical cell produced in Example 1 and the same cell produced in Comparative Examples 1 and 2 were set in an output characteristic evaluation apparatus, and the fuel electrode side was sealed with a Pyrex (registered trademark) glass material. A Pt wire having a diameter of 0.5 mm was attached to the side surface of the electrolyte to obtain a reference electrode. After raising the temperature in an N 2 atmosphere, hydrogen was introduced into the fuel electrode to perform a reduction treatment. The hydrogen reduction time was set at 1000 ° C. for 30 minutes.
  • Table 1 shows the electrochemical property evaluation results of the cells of Example 1 and Comparative Examples 1 and 2.
  • the power density of Example 1 is about 8% higher than the power density of Comparative Example 1, and the power density of about 32% higher than the power density of Comparative Example 2. It was observed.
  • the ohmic resistance in the fuel electrode is similarly compared. The ohmic resistance in the electrode is obtained by subtracting the theoretical electrolyte resistance of the YSZ electrolyte used from the cell resistance between the terminals, and the theoretical electrolyte resistance of 0.5 mm YSZ used in both cells is 0.50; cm 2 .
  • the contact resistance on the oxygen electrode side and the resistance in the electrode are regarded as sufficiently low, and the fuel electrode resistance is obtained by subtracting the theoretical electrolyte resistance from the cell resistance between the terminals. Comparing the calculation results of the ohmic resistance in the fuel electrode of both cells, the fuel electrode resistance of 0.01; cm 2 was compared in Comparative Example 1 while it was suppressed to almost zero in Example 1. In Example 2, an anode resistance of 0.05; cm 2 exists. As described above, from the comparison results of cell output density and ohmic resistance in the fuel electrode, the cell of Example 1 has higher characteristics than Comparative Examples 1 and 2, and has a structure having a catalyst concentration maximum at the center in the fuel electrode. The characteristic improvement effect by appears.
  • the effect of the catalyst concentration distribution in the fuel electrode is expected to be comparable even if the Ni-supported particles are not only aluminum oxide but also Ni-particle-supported magnesium oxide.

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Abstract

Disclosed is a solid oxide fuel cell that can more effectively utilize a catalyst and can realize high output properties by providing a catalyst concentration distribution within a fuel electrode. A fuel electrode is formed which has a structure having a maximum catalyst concentration in a region between a region near a fuel layer solid electrolyte and a region near the surface of the fuel electrode. The above constitution can facilitate the transfer of electrons and ions in the fuel electrode around the portion that has the maximum catalyst concentration, can improve fuel electrode properties, and can increase cell output.

Description

固体酸化物型燃料電池Solid oxide fuel cell
　本発明は、固体酸化物型燃料電池（ＳＯＦＣ）に関し、特に改善されたＳＯＦＣ用燃料極に関する。 The present invention relates to a solid oxide fuel cell (SOFC), and particularly to an improved fuel electrode for SOFC.
　固体酸化物型燃料電池（ＳＯＦＣ）はその高い作動温度（７００～１０００℃）から、高価な貴金属触媒を用いなくても十分な反応速度を得ることができ、また他のタイプの燃料電池と比較して最も発電効率が高くＣＯ２の発生も少ないため、次世代のクリーンな発電システムとして期待されている。 The solid oxide fuel cell (SOFC) can obtain a sufficient reaction rate without using an expensive noble metal catalyst due to its high operating temperature (700-1000 ° C), and compared with other types of fuel cells. As the power generation efficiency is the highest and the generation of CO 2 is small, it is expected as a next-generation clean power generation system.
　この固体酸化物型燃料電池の特性を向上させるには、燃料極の高性能化が必要である。一般的な燃料極には電子導電性を有する金属粒子とイオン導電性もしくは電子・イオン混合導電性を有するセラミックス粒子の混合焼結体であるサーメット材料が用いられる。しかしこのサーメット電極では、電極触媒となる金属が電極内の電子導電パスにもなるため金属粒子はある程度の大きさが必要であり、電極中の金属体積のわりに表面積は小さくなるため、電極反応に寄与する三相界面は限られてしまい触媒活性を向上させることは難しい。このため、燃料極の特性を向上させるには電極中のイオンおよび電子導電性を高くし、且つ触媒粒子の表面積を大きくする必要がある。 In order to improve the characteristics of this solid oxide fuel cell, it is necessary to improve the performance of the fuel electrode. A cermet material which is a mixed sintered body of metal particles having electronic conductivity and ceramic particles having ionic conductivity or mixed electron / ion conductivity is used for a general fuel electrode. However, in this cermet electrode, the metal used as the electrode catalyst also serves as an electron conduction path in the electrode, so the metal particles need to have a certain size. The contributing three-phase interface is limited and it is difficult to improve the catalytic activity. For this reason, in order to improve the characteristics of the fuel electrode, it is necessary to increase the ion and electron conductivity in the electrode and to increase the surface area of the catalyst particles.
　さらに、燃料極特性を向上させるには、燃料極反応に必要な電子，イオン，反応ガスが会合する三相界面まで、いかに効率良く電子やイオンを運ぶかが重要である。一般的なサーメット燃料極の金属粒子に注目すると、電解質近傍の金属粒子は電極触媒として主に機能し、燃料極表面付近になるにしたがい金属粒子は電子導電パスとして機能するため、燃料極を二層構造にして各層の電子導電性粒子とイオン導電性粒子の混合比を変化させる検討も行われている（非特許文献１参照）。この試みでは、燃料極中、電極表面層に金属粒子を多くいれることで良好な電子導電性を確保しセル集電体への電子供与を優先的に行う。また、電解質近傍層にはイオン導電性粒子を多く入れることで良好なイオン導電性を確保し、金属触媒上で電極反応が優先的に行われるよう設計されている。しかし、この二層構造電極ではサーメット材料を用いており、触媒に用いる金属粒子の粒径をあまり小さくすることができないため、触媒活性が低く、大幅な特性向上は望めない。 Furthermore, in order to improve the fuel electrode characteristics, it is important to efficiently transport electrons and ions to the three-phase interface where electrons, ions, and reaction gases necessary for the fuel electrode reaction meet. Focusing on the metal particles of a general cermet fuel electrode, the metal particles near the electrolyte mainly function as an electrode catalyst, and the metal particles function as an electronic conduction path as they approach the surface of the fuel electrode. Studies have also been conducted to change the mixing ratio of the electron conductive particles and the ion conductive particles in each layer in a layer structure (see Non-Patent Document 1). In this trial, a large amount of metal particles are placed in the electrode surface layer in the fuel electrode to ensure good electron conductivity and preferentially donate electrons to the cell current collector. Moreover, it is designed so that good ion conductivity can be ensured by putting a large amount of ion conductive particles in the electrolyte vicinity layer, and the electrode reaction is preferentially performed on the metal catalyst. However, the cermet material is used in this two-layer structure electrode, and the particle size of the metal particles used for the catalyst cannot be made very small, so that the catalytic activity is low and a significant improvement in characteristics cannot be expected.
　本発明は、上記固体酸化物型燃料電池において、触媒活性を改善することを目的としている。 The object of the present invention is to improve the catalytic activity in the solid oxide fuel cell.
　本発明の固体電解質燃料電池は、金属触媒、もしくは金属触媒を担持してなる金属触媒担持金属酸化物からなる触媒粒子と、電子・イオン混合導電性粒子との焼結体からなる固体酸化物型燃料電池燃料極を備えた固体酸化物型燃料電池であって、
　燃料極における前記触媒の濃度が、前記燃料極の面に垂直方向に不均一であって、燃料極の電解質近傍領域と燃料極表面近傍領域との間に配置されている燃料極中央領域において前記触媒濃度が極大値を持つことを特徴とする。 The solid electrolyte fuel cell of the present invention is a solid oxide type comprising a sintered body of a metal catalyst or a catalyst particle comprising a metal catalyst-carrying metal oxide carrying a metal catalyst and an electron / ion mixed conductive particle. A solid oxide fuel cell having a fuel cell anode,
The concentration of the catalyst in the fuel electrode is non-uniform in the direction perpendicular to the surface of the fuel electrode, and in the fuel electrode central region disposed between the electrolyte vicinity region and the fuel electrode surface vicinity region of the fuel electrode. The catalyst concentration has a maximum value.
　本発明によれば、上記構成によって、固体酸化物型燃料電池の燃料極活性を向上させ、固体酸化物型燃料電池の高出力化を達成することができる。 According to the present invention, with the above configuration, the anode activity of the solid oxide fuel cell can be improved, and the output of the solid oxide fuel cell can be increased.
図１は、本発明の第１の実施形態に係る固体酸化物型燃料電池（ＳＯＦＣ）燃料極の断面構造模式図である。FIG. 1 is a schematic sectional view of a solid oxide fuel cell (SOFC) fuel electrode according to a first embodiment of the present invention. 図２は、還元析出型触媒を用いた燃料極内に触媒濃度分布を有するＳＯＦＣ燃料極の断面模式図である。FIG. 2 is a schematic cross-sectional view of an SOFC fuel electrode having a catalyst concentration distribution in the fuel electrode using a reduction precipitation catalyst. 図３は、本実施形態に係る燃料極の製造工程を示す図である。FIG. 3 is a diagram illustrating a manufacturing process of the fuel electrode according to the present embodiment.
　以下、本発明による固体酸化物型燃料電池用燃料極材料及び燃料極の製造方法について説明するが、本発明は以下の実施の形態や実施例に限定されるものではない。また、以下の説明で参照する模式図は、各構成の位置関係を示す図であり、粒子の大きさや各層の厚さの比等は実際のものと必ずしも一致するものではない。 Hereinafter, the fuel electrode material for a solid oxide fuel cell and the method for manufacturing the fuel electrode according to the present invention will be described, but the present invention is not limited to the following embodiments and examples. Moreover, the schematic diagram referred in the following description is a figure which shows the positional relationship of each structure, The ratio of the magnitude | size of a particle | grain, the thickness of each layer, etc. do not necessarily correspond with an actual thing.
［固体酸化物型燃料電池のセル構成］
　本発明の実施形態は、燃料極とこれを用いた固体酸化物型燃料電池に関する。まず図１および図２の断面模式図を参照しつつ本実施形態を説明する。ＳＯＦＣは、固体酸化物電解質板１１を挟んで、その一方の面に燃料極材料層１２を、もう一方の面に酸素極材料層１３を積層して成る。
　上記酸素極材料層１３にて解離された酸素イオン（Ｏ２－）は固体酸化物電解質１１を通って燃料極材料層１２へと移動し、水素と反応して水を生成する。このときに生成する電子は外部回路を通して取り出し発電に供する。酸素極材料層１３側での酸素の解離および燃料極側での水素と酸素イオンとの反応は、いずれも電極内の電子－イオン－反応ガスが共に介する三相界面において起こる。そのため、固体酸化物型燃料電池においては、これら三相界面をいかに多く形成するかが重要な課題となる。
　なお、以下の実施の形態において説明する本発明において特徴的な構成要件以外の固体電解質燃料電池の構成要件は、特に記載がないものについては従来公知のものを採用することができる。 [Cell configuration of solid oxide fuel cell]
Embodiments described herein relate generally to a fuel electrode and a solid oxide fuel cell using the same. First, the present embodiment will be described with reference to schematic cross-sectional views of FIGS. 1 and 2. The SOFC is formed by laminating a fuel electrode material layer 12 on one surface and an oxygen electrode material layer 13 on the other surface with a solid oxide electrolyte plate 11 interposed therebetween.
Oxygen ions (O 2− ) dissociated in the oxygen electrode material layer 13 move to the fuel electrode material layer 12 through the solid oxide electrolyte 11 and react with hydrogen to generate water. The electrons generated at this time are taken out through an external circuit and used for power generation. Both the dissociation of oxygen on the oxygen electrode material layer 13 side and the reaction of hydrogen and oxygen ions on the fuel electrode side occur at the three-phase interface through which the electron-ion-reactive gas in the electrode is present. Therefore, in a solid oxide fuel cell, how many these three-phase interfaces are formed becomes an important issue.
In addition, as for the constituent requirements of the solid electrolyte fuel cell other than the characteristic constituent features in the present invention described in the following embodiments, those conventionally known can be adopted unless otherwise specified.
（酸素極材料層）
　酸素極材料層１３を構成する酸素極材料は、混合導電性を示す酸化物であり一般式Ｌｎ１－ｘＡｘＢＯ３－δ（Ｌｎ＝希土類元素；Ａ＝Ｓｒ、Ｃａ、Ｂａ；Ｂ＝Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉのうち少なくとも１種、ｘは、０～１、また、上記式中δは、酸素原子に欠損があることを意味している）で表される複合酸化物からなる。これらの複合酸化物は、酸素を効率よく解離すると同時に電子導電性を有している。
　また、前記複合酸化物で若干不足するイオン導電性を、イオン導電性酸化物を併せて添加することにより補うことも可能である。このイオン導電性酸化物としては、Ｓｍ２Ｏ３をドープしたＣｅＯ２、もしくはＧｄ２Ｏ３をドープしたＣｅＯ２、Ｙ２Ｏ３をドープしたＣｅＯ２のいずれか一つを用いる。これらは還元性雰囲気では電子とイオンの混合導電性を示すが、酸素含有雰囲気中では高いイオン導電性のみを示すものであり、かつ前記一般式Ｌｎ１－ｘＡｘＢＯ３－δで示される混合導電性を示す酸化物と反応をしないものである。 (Oxygen electrode material layer)
The oxygen electrode material constituting the oxygen electrode material layer 13 is an oxide exhibiting mixed conductivity and has a general formula Ln 1-x A x BO 3-δ (Ln = rare earth element; A = Sr, Ca, Ba; B = At least one of Cr, Mn, Fe, Co, and Ni, x is 0 to 1, and δ in the above formula means that there is a defect in the oxygen atom) Consists of. These complex oxides dissociate oxygen efficiently and have electronic conductivity.
It is also possible to compensate for the ionic conductivity that is slightly insufficient with the composite oxide by adding an ionic conductive oxide together. As the ion conductive oxide, Sm 2 O 3 CeO 2 doped with, or Gd 2 O 3 CeO 2 doped with, Y 2 O 3 is used any one of the doped CeO 2 a. These show mixed conductivity of electrons and ions in a reducing atmosphere, but only show high ionic conductivity in an oxygen-containing atmosphere, and are represented by the general formula Ln 1-x A x BO 3-δ. It does not react with oxides showing mixed conductivity.
（燃料極材料層）
　本発明者らは、これまでにＮｉ－Ａｌ系，Ｎｉ－Ｍｇ系の複合酸化物からの還元析出法による触媒製造法を開発してきており、この触媒と、イオン導電性もしくは電子・イオン混合導電性粒子との複合電極の性能を実証してきた（特開２００９－６４６４０号公報、及び特開２００９－６４６４１号公報参照）。
　この方法ではＮｉ－Ａｌ系，Ｎｉ－Ｍｇ系の複合酸化物を高温で還元することにより、Ｎｉ粒子担持アルミニウム複合酸化物／Ｎｉ粒子担持マグネシウム複合酸化物としてＡｌ系およびＭｇ系酸化物基体上にＮｉ微粒子を形成することができ、この析出したＮｉ微粒子はナノメートルサイズであることから、少量の触媒量で大きな触媒表面積を得ることができている。また、還元時に複合酸化物からの析出物として金属粒子を作製するため基体に固定化されており、高温還元雰囲気下においても金属粒子の焼結が起こりにくくなる。しかし、析出金属微粒子体積に比べ絶縁性基体の体積が大きいため、電極化時には燃料極層内のオーム抵抗が大きくなる。 (Fuel electrode material layer)
The present inventors have so far developed a catalyst production method by a reduction precipitation method from Ni—Al-based and Ni—Mg-based composite oxides. The performance of composite electrodes with conductive particles has been demonstrated (see Japanese Patent Application Laid-Open Nos. 2009-64640 and 2009-64641).
In this method, Ni-Al-based and Ni-Mg-based composite oxides are reduced at high temperatures to form Ni particle-supported aluminum composite oxide / Ni particle-supported magnesium composite oxide on Al-based and Mg-based oxide substrates. Ni fine particles can be formed, and the deposited Ni fine particles have a nanometer size, so that a large catalyst surface area can be obtained with a small amount of catalyst. Further, since metal particles are produced as precipitates from the composite oxide during reduction, they are immobilized on the substrate, and the metal particles are hardly sintered even in a high-temperature reducing atmosphere. However, since the volume of the insulating substrate is larger than the volume of the deposited metal fine particles, the ohmic resistance in the fuel electrode layer is increased when forming an electrode.
　本発明ではこのＮｉ粒子担持アルミニウム酸化物もしくはＮｉ粒子担持マグネシウム酸化物のような金属触媒担持酸化物粒子と、電子・イオン混合導電性粒子を併用して燃料極を形成する。その際に、燃料極中のＮｉ粒子担持アルミニウム酸化物もしくはＮｉ粒子担持マグネシウム酸化物と、電子・イオン混合導電性粒子の混合比を変化させる。これによって、燃料極表面近傍領域１８と電解質近傍領域２０には電子・イオン混合導電性粒子１６の量を多くし、燃料極中央領域にはＮｉ粒子担持アルミニウム複合酸化物あるいはＮｉ粒子担持マグネシウム複合酸化物量１７を多くした触媒濃度が極大である燃料極中央領域１９を設ける（図２）。これにより、電解質近傍領域２０の電子・イオン混合導電性粒子１６は主にイオン導電体として働き、表面近傍部１８の電子・イオン混合導電性粒子１６は電子導電体として主に働く。すなわち、酸素極１３で生成した酸化物イオン（Ｏ２－）は固体酸化物電解質１１を通って電解質近傍領域２０までスムーズに移動することができ、移動してきた酸素イオン（Ｏ２－）は燃料極中央領域１９で多くの触媒により活性化されて水蒸気と電子に効率的に反応し、生成した電子は、燃料極表面近傍領域１８を通って集電体２１まで運ばれる。これにより燃料極内での電子およびイオンの導電がスムーズになることに加え、触媒を有効に利用することができるため燃料極特性が向上する。 In the present invention, the fuel electrode is formed by using the metal catalyst-supported oxide particles such as the Ni particle-supported aluminum oxide or the Ni particle-supported magnesium oxide and the electron / ion mixed conductive particles in combination. At that time, the mixing ratio of the Ni particle-supported aluminum oxide or Ni particle-supported magnesium oxide and the electron / ion mixed conductive particles in the fuel electrode is changed. As a result, the amount of the electron / ion mixed conductive particles 16 is increased in the fuel electrode surface vicinity region 18 and the electrolyte vicinity region 20, and Ni particle-supported aluminum composite oxide or Ni particle-supported magnesium composite oxidation is provided in the fuel electrode center region. A fuel electrode central region 19 having a maximum catalyst concentration with an increased amount 17 is provided (FIG. 2). Thereby, the electron / ion mixed conductive particles 16 in the electrolyte vicinity region 20 mainly function as an ionic conductor, and the electron / ion mixed conductive particles 16 in the surface vicinity portion 18 mainly function as an electron conductor. That is, the oxide ions (O 2− ) generated at the oxygen electrode 13 can smoothly move through the solid oxide electrolyte 11 to the vicinity of the electrolyte 20, and the transferred oxygen ions (O 2− ) Activated by many catalysts in the pole center region 19 and efficiently reacts with water vapor and electrons, and the generated electrons are transported to the current collector 21 through the fuel electrode surface vicinity region 18. Thereby, in addition to smooth conduction of electrons and ions in the fuel electrode, the catalyst can be used effectively, so that the fuel electrode characteristics are improved.
　本実施の形態に於いて燃料極に用いる金属触媒担持酸化物粒子としては、触媒金属とこれを担持する金属酸化物を構成する元素を含有する前駆体となる複合酸化物を還元することにより作成される金属触媒担持酸化物粒子を用いることができる。
　具体的には、Ｎｉ－Ａｌ複合酸化物粒子（ＮｉＡｌ２Ｏ４複合酸化物）中のＮｉ成分が還元により表面へ析出して、基材はアルミニウム酸化物（おもにＡｌ２Ｏ３）となる。すなわち、Ｎｉ粒子担持Ａｌ２Ｏ３が形成される。このようにして形成される金属微粒子の大きさは一般には数十ｎｍである。活性な触媒機能を果たすには、金属微粒子の大きさは５ｎｍ以上５００ｎｍ以下程度であることが好ましい。５ｎｍ以下のサイズのものは現実的に作製が困難であるし、５００ｎｍ以上となると隣接粒子同士が結合してしまって従来のＮｉＯを還元して用いるのと同じ問題を抱えてしまう恐れがある。触媒としてより好ましいサイズは２０ｎｍ以上１００ｎｍ以下程度である。このサイズは従来の電極触媒サイズの１～２桁小さい値のため触媒活性の向上が期待される。このため、添加するＮｉＡｌ２Ｏ４の量としては電極を構成する材料全体の５重量％以上８０重量％以下の範囲内が良い。より好ましくは１０重量％以上５０重量％以下である。 The metal catalyst-supported oxide particles used in the fuel electrode in the present embodiment are prepared by reducing a composite oxide that is a precursor containing a catalyst metal and an element constituting the metal oxide that supports the catalyst metal. The metal catalyst-supported oxide particles can be used.
Specifically, the Ni component in the Ni—Al composite oxide particles (NiAl 2 O 4 composite oxide) is precipitated on the surface by reduction, and the base material becomes aluminum oxide (mainly Al 2 O 3 ). That is, Ni particle carrying Al 2 O 3 is formed. The size of the metal fine particles thus formed is generally several tens of nm. In order to perform an active catalytic function, the size of the metal fine particles is preferably about 5 nm to 500 nm. A particle having a size of 5 nm or less is actually difficult to produce, and if the particle size is 500 nm or more, adjacent particles may be bonded to each other and may have the same problem as conventional NiO reduced. A more preferable size for the catalyst is about 20 nm to 100 nm. Since this size is one to two orders of magnitude smaller than the conventional electrode catalyst size, an improvement in catalyst activity is expected. For this reason, the amount of NiAl 2 O 4 to be added is preferably in the range of 5 wt% to 80 wt% of the entire material constituting the electrode. More preferably, it is 10 to 50 weight%.
　本実施の形態において、燃料極に用いる電子・イオン混合導電性を有する粒子材料としては、Ｓｍ２Ｏ３をドープしたＣｅＯ２もしくはＧｄ２Ｏ３をドープしたＣｅＯ２、もしくはＹ２Ｏ３をドープしたＣｅＯ２を用いることができるが、これに限定されず、４００℃以上１０００℃以下において高い酸素イオン導電性と電子導電性を有しているものであれば良い。一般的には１０～５０ｍｏｌ％のＳｍ２Ｏ３、Ｇｄ２Ｏ３、もしくはＹ２Ｏ３をドープしたＣｅＯ２の範囲が良い。（Ｊ．　Ａｐｐｌ．Ｅｌｅｃｔｒｏｃｈｅｍ．，１８，５２７（１９８８）．参照）。 In this embodiment, the particulate material having electron-ion mixed conductivity used in the fuel electrode, CeO 2 doped with CeO 2 or Gd 2 O 3 doped with Sm 2 O 3, or a Y 2 O 3 doped and CeO 2 can be used with, without being limited thereto, as long as it has a high oxygen ion conductivity and electronic conductivity at 400 ° C. or higher 1000 ° C. or less. Generally, CeO 2 doped with 10 to 50 mol% Sm 2 O 3 , Gd 2 O 3 , or Y 2 O 3 is preferable. (See J. Appl. Electrochem., 18, 527 (1988).).
　本実施の形態において、燃料極材料層を構成する物質の混合比率は、以下の範囲とすることが好ましい。
　燃料極表面近傍領域においては、触媒担持金属酸化物と、電子・イオン導電性酸化物との混合比率は、重量比にして、触媒担持金属酸化物：電子・イオン導電性酸化物＝１：２～９の範囲が好ましい。その理由は、電子・イオン導電性酸化物粒子同士の十分なネットワークを作製する必要があるからである。
　燃料極中央領域においては、触媒担持金属酸化物と、電子・イオン導電性酸化物との混合比率は、重量比にして、触媒担持金属酸化物：電子・イオン導電性酸化物＝１：１～４の範囲が好ましい。その理由は、燃料極表面近傍領域および固体電解質近傍領域よりも触媒担持金属酸化物量が多く、またイオン導電性酸化物粒子同士のネットワーク切断しない必要があるからである。
　固体電解質近傍領域においては、触媒担持金属酸化物と、電子・イオン導電性酸化物との混合比率は、重量比にして、触媒担持金属酸化物：電子・イオン導電性酸化物＝１：２～９の範囲が好ましい。その理由は、電子・イオン導電性酸化物粒子同士の十分なネットワークを作製する必要があるからである。 In the present embodiment, the mixing ratio of the substances constituting the fuel electrode material layer is preferably set in the following range.
In the region near the surface of the fuel electrode, the mixing ratio of the catalyst-supporting metal oxide and the electron / ion conductive oxide is, as a weight ratio, catalyst-supporting metal oxide: electron / ion conductive oxide = 1: 2. A range of ˜9 is preferred. The reason is that it is necessary to produce a sufficient network of electron / ion conductive oxide particles.
In the central region of the fuel electrode, the mixing ratio of the catalyst-supported metal oxide and the electron / ion conductive oxide is, as a weight ratio, catalyst-supported metal oxide: electron / ion conductive oxide = 1: 1 to A range of 4 is preferred. The reason is that the amount of the catalyst-supporting metal oxide is larger than the region near the fuel electrode surface and the region near the solid electrolyte, and it is necessary not to cut the network between the ion conductive oxide particles.
In the vicinity of the solid electrolyte, the catalyst-supporting metal oxide and the electron / ion conductive oxide are mixed in a weight ratio of catalyst-supporting metal oxide: electron / ion conductive oxide = 1: 2 to A range of 9 is preferred. The reason is that it is necessary to produce a sufficient network of electron / ion conductive oxide particles.
　上記本実施の形態において、電解質近傍領域２０とは、燃料極材料層１２において固体電解質板１１表面から、１／３の厚さを有する燃料極材料層の領域を示し、燃料極表面近傍領域１８とは、同じく燃料極材料層においてその表面から１／３の厚さを有する燃料極材料層の領域を言う。本発明においては、この燃料極表面近傍領域１８の層の触媒濃度と、燃料極中心領域１９の触媒濃度と、電解質近傍領域２０の触媒濃度の関係を、燃料極中心領域１９の触媒濃度がもっとも高くなるように構成することにより、前記本発明の効果を達成するものである。
　かかる本発明において、燃料極材料層１２は、明確に不連続面を備えた層となっていても良いし、燃料極材料層が、連続して組成が変化する不連続面を有していない一様な層であってもよい。この場合、それぞれの領域を構成する材料組成の平均濃度が上記条件を満足していても良いし、さらに薄い領域で明確に極大値を有する構成であっても良い。 In the present embodiment, the electrolyte vicinity region 20 indicates a region of the fuel electrode material layer having a thickness of 1/3 from the surface of the solid electrolyte plate 11 in the fuel electrode material layer 12, and the fuel electrode surface vicinity region 18. Similarly, the region of the fuel electrode material layer having a thickness of 1/3 from the surface thereof in the fuel electrode material layer. In the present invention, the relationship between the catalyst concentration in the layer near the fuel electrode surface area 18, the catalyst concentration in the fuel electrode center area 19, and the catalyst concentration in the electrolyte vicinity area 20 is as follows. By configuring so as to be high, the effect of the present invention is achieved.
In the present invention, the fuel electrode material layer 12 may be a layer having a clearly discontinuous surface, or the fuel electrode material layer does not have a discontinuous surface whose composition changes continuously. It may be a uniform layer. In this case, the average concentration of the material composition constituting each region may satisfy the above-described conditions, or may be a configuration having a clearly maximum value in a thinner region.
　また、燃料極集電体２１と、燃料極材料層１２の間には、網目状集電配線層もしくは高い電子導電性を有する多孔質な集電層を有していても良い。これにより燃料極集電体－燃料極間の電子導電が容易になる。（特開２００９－６４６４０号公報参照） In addition, between the fuel electrode current collector 21 and the fuel electrode material layer 12, a mesh-like current collecting wiring layer or a porous current collecting layer having high electronic conductivity may be provided. This facilitates electronic conduction between the fuel electrode current collector and the fuel electrode. (Refer to JP 2009-64640 A)
［燃料電池用電極の製造方法］
　以下に、前記燃料極構造を有する燃料極を備えた燃料電池セルの製造方法を詳述する。この実施の形態では、金属触媒粒子担持酸化物粒子として、Ｎｉ－Ａｌ系複合酸化物を触媒合成の前駆体として用いたＮｉ粒子担持アルミナ粒子を採用し、電子・イオン混合導電性粒子として、サマリアドープセリア（ＳＤＣ）を用いた場合を例にとって、説明するが、本発明はこれに限定されるものではなく、同様な作用を有する物質を用いても差し支えないことはもちろんである。 [Method for producing fuel cell electrode]
Below, the manufacturing method of the fuel cell provided with the fuel electrode which has the said fuel electrode structure is explained in full detail. In this embodiment, as the metal catalyst particle-supported oxide particles, Ni particle-supported alumina particles using a Ni—Al based composite oxide as a catalyst synthesis precursor are adopted, and as the electron / ion mixed conductive particles, Samaria is used. The case where doped ceria (SDC) is used will be described as an example. However, the present invention is not limited to this, and it is needless to say that a substance having the same function may be used.
　本実施の形態の燃料電池用燃料極の製造方法を図３に示す。
　図３に見られるように、ニッケルアルミニウム複合酸化物のような触媒金属粒子担持酸化物の前駆体を作成した後、これを粉砕して粒子化する。次いで、各原料を混合し、ペースト化する（Ｓ１）。
　次いで、これを所要の形状に成形し（Ｓ２）、焼成を行う（Ｓ３）。燃料極が所要の厚さになるまで、この工程を繰り返し、還元を行って触媒金属粒子担持酸化物前駆体を還元する（Ｓ４）
　以上の工程によって、燃料極が形成され、さらに酸素極等を形成して燃料電池を作成する。 FIG. 3 shows a method of manufacturing the fuel electrode for the fuel cell according to the present embodiment.
As shown in FIG. 3, after a catalyst metal particle-supported oxide precursor such as a nickel aluminum composite oxide is prepared, it is pulverized into particles. Next, the raw materials are mixed and made into a paste (S1).
Subsequently, this is shape | molded in a required shape (S2), and baking is performed (S3). This process is repeated until the fuel electrode has a required thickness, and reduction is performed to reduce the catalyst metal particle-supported oxide precursor (S4).
Through the above steps, a fuel electrode is formed, and an oxygen electrode and the like are further formed to produce a fuel cell.
　以下、具体的に各工程について説明する。
　まず、ＮｉＯ粉末とＡｌ２Ｏ３粉末を混合焼成して、ＮｉＡｌ２Ｏ４で表されるＮｉ－Ａｌ複合酸化物からなる触媒前駆体を作製し、これを粉砕してＮｉ－Ａｌ複合酸化物前駆体粒子を作成する。粉砕後の複合酸化物粒子径は０．１～数μｍ程度が好ましい。 Hereinafter, each step will be specifically described.
First, NiO powder and Al 2 O 3 powder are mixed and fired to prepare a catalyst precursor made of a Ni—Al composite oxide represented by NiAl 2 O 4 , and then pulverized to obtain a Ni—Al composite oxide Precursor particles are created. The composite oxide particle diameter after pulverization is preferably about 0.1 to several μm.
　次に、このようにして作製したＮｉ－Ａｌ複合酸化物前駆体粒子と、電子・イオン混合導電性粒子とを目的の割合で混合し、目的の組成に調製した硝酸塩等の金属塩水溶液を加えてペースト化する（図３のS1）。
　電子・イオン混合導電性粒子の例としては、Ｓｍ２Ｏ３をドープしたＣｅＯ２もしくはＧｄ２Ｏ３をドープしたＣｅＯ２、もしくはＹ２Ｏ３をドープしたＣｅＯ２を用いるが、これに限定されず、４００℃以上１０００℃以下において高い酸化物イオン導電性と電子導電性を有しているものであれば良い。 Next, the Ni—Al composite oxide precursor particles thus prepared and the electron / ion mixed conductive particles are mixed at a target ratio, and an aqueous solution of a metal salt such as nitrate is added to the target composition. To make a paste (S1 in FIG. 3).
Examples of electron-ion mixed conductive particles, Sm 2 O 3 CeO 2 was doped or CeO 2 doped with Gd 2 O 3, or uses a CeO 2 doped with Y 2 O 3, are limited to However, what is necessary is just to have high oxide ion electroconductivity and electronic conductivity in 400 degreeC or more and 1000 degrees C or less.
　次に、このペースト化した混合粉末を固体電解質板１１の表面にスクリーン印刷し、両者の接着強度が高まる温度まで昇温して焼成する（図３のS2,S3）。
　この焼成温度は、１０００℃以上１４００℃以下の範囲で焼成することが好ましい。目的の組成に調製した硝酸塩等の金属塩水溶液を加えてペースト化したＮｉ－Ａｌ複合酸化物前駆体粒子と電子・イオン混合導電性粒子のペーストをスクリーン印刷し、両者の接着強度が高まる温度まで昇温して焼成を繰り返すことにより、本実施形態の特徴であるそれぞれの部分でＮｉ－Ａｌ複合酸化物粒子と電子・イオン混合導電性粒子の比率が異なる燃料極表面近傍領域１８、燃料極中央領域１９、電解質近傍領域２０を形成する。
　上記電子・イオン混合導電性粒子１６とＮｉ－Ａｌ複合酸化物前駆体粒子を形成する方法はこれに限定されるものではない。混合粉末をスラリー化して塗布、ディッピング、あるいはスプレーコーティング法により作製しても、シート化し積層形成しても構わない。
　上記焼結により、Ｎｉ－Ａｌ複合酸化物粒子と電子・イオン混合導電性酸化物粒子が結合・一体化し、ネットワークを形成している。また、電極中のガス拡散性を考慮すると、燃料極材料層及び酸素極材料層は、連通気泡からなる多孔質であることが好ましく、あらかじめ焼成時に焼失して気孔を形成する気孔形成材を混合しておくことで効果的に気孔を形成することができる。気孔形成材の例としては有機系材料で、例えばアクリル系の球状粒子などを採用することができる。 Next, the pasted mixed powder is screen-printed on the surface of the solid electrolyte plate 11, and heated to a temperature at which the adhesive strength between the two is increased and baked (S2, S3 in FIG. 3).
The firing temperature is preferably in the range of 1000 ° C. to 1400 ° C. Ni-Al composite oxide precursor particles pasted by adding an aqueous solution of metal salt such as nitrate to the desired composition and screen-printed paste of electron / ion mixed conductive particles, up to a temperature at which the adhesive strength between them is increased By repeating the firing after raising the temperature, the area near the fuel electrode surface 18 and the center of the fuel electrode where the ratio of the Ni—Al composite oxide particles and the electron / ion mixed conductive particles is different in each part, which is a feature of this embodiment Region 19 and electrolyte vicinity region 20 are formed.
The method of forming the electron / ion mixed conductive particles 16 and the Ni—Al composite oxide precursor particles is not limited to this. The mixed powder may be made into a slurry by coating, dipping, or spray coating, or formed into a sheet and laminated.
By the sintering, the Ni—Al composite oxide particles and the electron / ion mixed conductive oxide particles are combined and integrated to form a network. In consideration of gas diffusibility in the electrode, the fuel electrode material layer and the oxygen electrode material layer are preferably porous composed of open cells, and are mixed with a pore-forming material that is previously burned down to form pores. Thus, pores can be effectively formed. An example of the pore forming material is an organic material such as acrylic spherical particles.
　その後、酸素極材料層１３の材料として一般式Ｌｎ１－ｘＡｘＢＯ３－δ（Ｌｎ＝希土類元素；Ａ＝Ｓｒ、Ｃａ、Ｂａ；Ｂ＝Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉのうち少なくとも１種であり、ｘは、０～１である。）で表される複合酸化物を、水またはアルコール系溶媒を用いてペースト化し、燃料極を焼き付けた面と反対側の固体電解質板１１の表面にスクリーン印刷し、両者の接着強度が高まる温度まで昇温して焼成する。
　一般には１０００℃以上１３００℃以下の範囲で焼成することが好ましい。また酸素極ペーストにはＬｎ１－ｘＡｘＢＯ３－δ（Ｌｎ＝希土類元素；Ａ＝Ｓｒ、Ｃａ、Ｂａ；Ｂ＝Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉのうち少なくとも１種であり、ｘは、０～１である。）で表される複合酸化物だけでなく、イオン導電性を示す粒子を混合してもよい。
　イオン導電性を有する粒子としては、例えば、ＳＤＣ、ＧＤＣ、ＹＤＣなどを用いることができる。 Thereafter, the material of the oxygen electrode material layer 13 is represented by the general formula Ln 1-x A x BO 3-δ (Ln = rare earth element; A = Sr, Ca, Ba; B = Cr, Mn, Fe, Co, Ni) 1 is a type, and x is 0 to 1.) The composite oxide represented by the formula (1) is pasted using water or an alcohol solvent, and the solid electrolyte plate 11 on the side opposite to the surface on which the fuel electrode is baked is formed. Screen printing is performed on the surface, and the temperature is raised to a temperature at which the adhesive strength between the two is increased, followed by firing.
In general, it is preferable to fire in the range of 1000 ° C. to 1300 ° C. The oxygen electrode paste includes Ln 1-x A x BO 3-δ (Ln = rare earth element; A = Sr, Ca, Ba; B = Cr, Mn, Fe, Co, Ni, and x Is 0 to 1.) In addition to the composite oxide represented by (1), particles exhibiting ionic conductivity may be mixed.
As the particles having ion conductivity, for example, SDC, GDC, YDC, or the like can be used.
　酸素極１３焼成後、燃料極を８００℃以上１０００℃以下の還元性雰囲気下にて還元処理する（図３のS4）。
　通常ＮｉＯの還元処理では必要以上に温度を上げないよう９００℃程度で行うが、ＮｉＡｌ２Ｏ４を主成分とする本実施形態ではＮｉの析出を十分に起こさせるため、９００℃以上で還元することがより好ましい。還元時間は特に限定されないが１０分程度もあればよい。 After the oxygen electrode 13 is fired, the fuel electrode is reduced in a reducing atmosphere of 800 ° C. or higher and 1000 ° C. or lower (S4 in FIG. 3).
Usually, the reduction treatment of NiO is performed at about 900 ° C. so as not to raise the temperature more than necessary. However, in this embodiment containing NiAl 2 O 4 as a main component, Ni is sufficiently precipitated, so that the reduction is performed at 900 ° C. or more. It is more preferable. The reduction time is not particularly limited, but may be about 10 minutes.
　還元によりＮｉ－Ａｌ複合酸化物前駆体粒子（ＮｉＡｌ２Ｏ４複合酸化物）中のＮｉ成分が表面へ析出して基材はアルミニウム酸化物（おもにＡｌ２Ｏ３）となる。すなわち、Ｎｉ粒子担持Ａｌ２Ｏ３が形成される。このようにして形成される金属微粒子の大きさは一般には数十ｎｍである。活性な触媒機能を果たすには、金属微粒子の大きさは５ｎｍ以上５００ｎｍ以下程度であることが好ましい。５ｎｍ以下のサイズのものは現実的に作製が困難であるし、５００ｎｍ以上となると隣接粒子同士が結合してしまって従来のＮｉＯを還元して用いるのと同じ問題を抱えてしまう恐れがある。触媒としてより好ましいサイズは２０ｎｍ以上１００ｎｍ以下程度である。このサイズは従来の電極触媒サイズの１～２桁小さい値のため触媒活性の向上が期待される。このため、添加するＮｉＡｌ２Ｏ４の量としては電極を構成する材料全体の５重量％以上８０重量％以下の範囲内が良い。より好ましくは１０重量％以上５０重量％以下である。 The Ni component in the Ni—Al composite oxide precursor particles (NiAl 2 O 4 composite oxide) is deposited on the surface by the reduction, and the base material becomes aluminum oxide (mainly Al 2 O 3 ). That is, Ni particle-supported Al 2 O 3 is formed. The size of the metal fine particles thus formed is generally several tens of nm. In order to perform an active catalytic function, the size of the metal fine particles is preferably about 5 nm to 500 nm. A particle having a size of 5 nm or less is actually difficult to produce, and if the particle size is 500 nm or more, adjacent particles may be bonded to each other and may have the same problem as conventional NiO reduced. A more preferable size for the catalyst is about 20 nm to 100 nm. Since this size is one to two orders of magnitude smaller than the conventional electrode catalyst size, an improvement in catalyst activity is expected. For this reason, the amount of NiAl 2 O 4 to be added is preferably in the range of 5 wt% to 80 wt% of the entire material constituting the electrode. More preferably, it is 10 to 50 weight%.
　本実施形態によれば、形成する触媒粒子径が小さいため、触媒濃度極大部においても従来のサーメット型燃料極で使用する触媒量に比べ少なくすることができ、混合導電体部分を大きくとることが可能となり、固体電解質との熱膨張的な差や整合ミスマッチによる差を小さく抑えることができる。 According to the present embodiment, since the catalyst particle diameter to be formed is small, the amount of catalyst used in the conventional cermet type fuel electrode can be reduced even at the catalyst concentration maximum portion, and the mixed conductor portion can be made large. This makes it possible to suppress differences in thermal expansion from the solid electrolyte and differences due to matching mismatch.
　また、この析出金属粒子は、基材であるＡｌ２Ｏ３の表面部に一層だけ存在し、基材との整合性が良く、強い結合を有している。したがって、高温還元性雰囲気にさらされても容易に移動することが無いという特徴も有している。 Further, the deposited metal particles are present only in one layer on the surface portion of the base material Al 2 O 3 , have good consistency with the base material, and have a strong bond. Therefore, it also has a feature that it does not move easily even when exposed to a high temperature reducing atmosphere.
　さらに、金属粒子が微細で孤立して存在するため、急激な酸化に対しても体積膨張が局所的に抑えられ、破壊に至りにくいという利点もある。 Furthermore, since the metal particles are fine and isolated, there is an advantage that volume expansion is locally suppressed even against rapid oxidation, and it is difficult to cause destruction.
　以上説明したように、本実施形態により作製される燃料極によれば、微細なＮｉ粒子を基材固定化することが可能な複合酸化物を用いた燃料極の接触抵抗が小さくでき、セルの損失を少なくすることができる。また析出触媒を有効に利用することができセル出力の向上も可能である。 As described above, according to the fuel electrode produced according to the present embodiment, the contact resistance of the fuel electrode using the composite oxide capable of fixing the fine Ni particles to the base material can be reduced, and the cell Loss can be reduced. In addition, the precipitation catalyst can be used effectively, and the cell output can be improved.
　以上の手段によって、本発明によれば、電極調製プロセスにおいてもスクリーン印刷、スプレーコーティングなど安価な製法が適用でき、低コストでセルを作製することが可能である。 By the above means, according to the present invention, an inexpensive manufacturing method such as screen printing and spray coating can be applied even in the electrode preparation process, and a cell can be manufactured at low cost.
　本実施の形態について実施例によってさらに詳細に説明する。電極に用いるイオン導電性を有する焼結体としてＳｍ２Ｏ３をドープしたＣｅＯ２を、金属触媒粒子担持酸化物前駆体としてＮｉＡｌ２Ｏ４を例に挙げて説明する。また、用いた粉末の粒径等は以下の記載の範囲に限定されるものではない。 This embodiment will be described in more detail with reference to examples. Description will be made by taking CeO 2 doped with Sm 2 O 3 as a sintered body having ionic conductivity used for an electrode and NiAl 2 O 4 as an example of a metal catalyst particle-supported oxide precursor. Moreover, the particle diameter etc. of the used powder are not limited to the range of the following description.
＜Ｎｉ－Ａｌ複合酸化物前駆体の調製＞
　平均粒径約１μｍのＮｉＯ粉末と平均粒径約０．４μｍのＡｌ２Ｏ３粉末をモル比で１：１になるように混合し、混合粉末をプレス成形してアルゴン中、１３００℃で５時間焼結することでＮｉＡｌ２Ｏ４複合酸化物を作製した。遊星型ボールミルを用いてこの複合酸化物を、比表面積が２０～２３ｍ２／ｇになるまで粉砕し、ＮｉＡｌ２Ｏ４燃料極触媒前駆体とした。 <Preparation of Ni-Al composite oxide precursor>
NiO powder having an average particle diameter of about 1 μm and Al 2 O 3 powder having an average particle diameter of about 0.4 μm were mixed at a molar ratio of 1: 1, the mixed powder was press-molded, and the mixture was pressed in argon at 1300 ° C. for 5 minutes. NiAl 2 O 4 composite oxide was produced by sintering for a period of time. Using a planetary ball mill, this composite oxide was pulverized until the specific surface area became 20 to 23 m 2 / g to obtain a NiAl 2 O 4 fuel electrode catalyst precursor.
＜ペースト化溶液の調製＞
　イオン導電性を有する焼結体であるＳＤＣ（Ｓｍ０．２Ｃｅ０．８Ｏ２）と同組成になるように、ＣｅおよびＳｍの硝酸塩をＣｅ：Ｓｍ＝１：４で混合し、ＳＤＣとして０．８Ｍになるように硝酸塩水溶液を調製した。 <Preparation of pasting solution>
Ce and Sm nitrates were mixed at Ce: Sm = 1: 4 so as to have the same composition as SDC (Sm 0.2 Ce 0.8 O 2 ), which is a sintered body having ionic conductivity, and SDC A nitrate aqueous solution was prepared so as to have a concentration of 0.8M.
＜燃料極ペーストの調製＞
　前記「Ｎｉ－Ａｌ複合酸化物前駆体の調製」で調製したＮｉＡｌ２Ｏ４燃料極触媒前駆体と、イオン導電性を有する焼結体として平均粒径０．３μｍのＳＤＣ（Ｓｍ０．２Ｃｅ０．８Ｏ２）粒子とを、粉砕粒子の重量比で１０：９０，１５：８５，２０：８０，３０：７０重量比になるようにそれぞれ混合粉を秤量した。この混合粉に前記「ペースト化溶媒の調整」で調整したＣｅ，Ｓｍ硝酸塩水溶液を混合粉末に対して約３０重量％加えて高速回転混合機により混合することで、燃料極ペーストとした。 <Preparation of fuel electrode paste>
The NiAl 2 O 4 fuel electrode catalyst precursor prepared in “Preparation of Ni—Al composite oxide precursor” and SDC (Sm 0.2 Ce) having an average particle size of 0.3 μm as a sintered body having ionic conductivity. 0.8 O 2 ) particles were weighed so that the weight ratio of the pulverized particles was 10:90, 15:85, 20:80, and 30:70, respectively. A fuel electrode paste was prepared by adding approximately 30% by weight of the Ce and Sm nitrate aqueous solution prepared in the above “adjustment of pasting solvent” to the mixed powder, and mixing the mixture with a high-speed rotary mixer.
＜固体酸化物電気化学セルの作製－１＞（実施例１）
　固体酸化物電解質にはφ１８ｍｍ、厚さ５００μｍに加工したＹＳＺ（８ｍｏｌ％Ｙ２Ｏ３で安定化させたＺｒＯ２）を用いた。始めに前記「燃料極ペーストの調製」で調製したＮｉＡｌ２Ｏ４：ＳＤＣ＝１５：８５のペーストをスクリーン印刷機でＹＳＺ電解質の中央にφ６ｍｍの大きさで印刷した。印刷後、大気炉に入れ、４００℃にて３０分間の仮焼成を行った。その後、前記「燃料極ペーストの調製」で調製したＮｉＡｌ２Ｏ４：ＳＤＣ＝３０：７０のペーストを先に形成したＮｉＡｌ２Ｏ４－ＳＤＣ上にぴったり重なるよう同様に印刷し、大気炉に入れ再度４００℃にて３０分間の仮焼成を行った。つづいて、前記「燃料極ペーストの調製」で調製したＮｉＡｌ２Ｏ４：ＳＤＣ＝１５：８５のペーストを先に形成した二層のＮｉＡｌ２Ｏ４－ＳＤＣ上にぴったり重なるよう同様に印刷し、大気炉に入れ１３００℃にて２時間焼成を行った。次に、ＹＳＺ電解質の反対面にＰｔ電極を同様に印刷して酸素極とし、また電解質側面にＰｔ参照極を塗って、９６０℃で３０分間焼成した。その後、ＹＳＺ粉末を混合したＮｉペースト（Ｎｉ：ＹＳＺが重量比で８２：１８になるように混合）を、三層構造燃料極表面上にぴったりと重なるように、燃料極ペーストと同様に印刷し、燃料極表面上に集電層を積層した。その後、大気雰囲気中、９６０℃で３０分間の熱処理を施し、集電層を電極表面に固定化した。 <Preparation of Solid Oxide Electrochemical Cell-1> (Example 1)
As the solid oxide electrolyte, YSZ (ZrO 2 stabilized with 8 mol% Y 2 O 3 ) processed to have a diameter of 18 mm and a thickness of 500 μm was used. First, the paste of NiAl 2 O 4 : SDC = 15: 85 prepared in the above “Preparation of fuel electrode paste” was printed with a screen printer at a size of φ6 mm in the center of the YSZ electrolyte. After printing, it was placed in an atmospheric furnace and pre-baked at 400 ° C. for 30 minutes. Thereafter, the NiAl 2 O 4 : SDC = 30: 70 paste prepared in the above “Preparation of fuel electrode paste” is printed in the same manner so as to be exactly overlapped on the previously formed NiAl 2 O 4 -SDC, and placed in an atmospheric furnace. Temporary baking was performed again at 400 ° C. for 30 minutes. Subsequently, the paste of NiAl 2 O 4 : SDC = 15: 85 prepared in the above “Preparation of fuel electrode paste” was printed in the same manner so as to be exactly overlapped on the two layers of NiAl 2 O 4 -SDC formed earlier, It baked at 1300 degreeC for 2 hours in the atmospheric furnace. Next, a Pt electrode was similarly printed on the opposite surface of the YSZ electrolyte to form an oxygen electrode, and a Pt reference electrode was applied to the electrolyte side surface, followed by baking at 960 ° C. for 30 minutes. After that, the Ni paste mixed with YSZ powder (Ni: YSZ is mixed so that the weight ratio is 82:18) is printed in the same manner as the fuel electrode paste so as to exactly overlap the surface of the three-layer structure fuel electrode. A current collecting layer was laminated on the fuel electrode surface. Thereafter, heat treatment was performed at 960 ° C. for 30 minutes in an air atmosphere, and the current collecting layer was immobilized on the electrode surface.
＜固体酸化物電気化学セルの作製－２＞（比較例１）
　固体酸化物電解質にはφ１８ｍｍ、厚さ５００μｍに加工したＹＳＺ（８ｍｏｌ％Ｙ２Ｏ３で安定化させたＺｒＯ２）を用いた。始めに前記「燃料極ペーストの調製」で調製したＮｉＡｌ２Ｏ４：ＳＤＣ＝１０：９０のペーストをスクリーン印刷機でＹＳＺ電解質の中央にφ６ｍｍの大きさで印刷した。印刷後、大気炉に入れ、４００℃にて３０分間の仮焼成を行った。その後、前記「燃料極ペーストの調製」で調製したＮｉＡｌ２Ｏ４：ＳＤＣ＝２０：８０のペーストを先に形成したＮｉＡｌ２Ｏ４－ＳＤＣ上にぴったり重なるよう同様に印刷し、大気炉に入れ再度４００℃にて３０分間の仮焼成を行った。つづいて、前記「燃料極ペーストの調製」で調製したＮｉＡｌ２Ｏ４：ＳＤＣ＝３０：７０のペーストを先に形成した二層のＮｉＡｌ２Ｏ４－ＳＤＣ上にぴったり重なるよう同様に印刷し、大気炉に入れ１３００℃にて２時間焼成を行った。次に、ＹＳＺ電解質の反対面にＰｔ電極を同様に印刷して酸素極とし、また電解質側面にＰｔ参照極を塗って、９６０℃で３０分間焼成した。その後、ＹＳＺ粉末を混合したＮｉペースト（Ｎｉ：ＹＳＺが重量比で８２：１８になるように混合）を、三層構造燃料極表面上にぴったりと重なるように、燃料極ペーストと同様に印刷し、燃料極表面上に集電層を積層した。その後、大気雰囲気中、９６０℃で３０分間の熱処理を施し、集電層を電極表面に固定化した。 <Preparation of Solid Oxide Electrochemical Cell-2> (Comparative Example 1)
As the solid oxide electrolyte, YSZ (ZrO 2 stabilized with 8 mol% Y 2 O 3 ) processed to have a diameter of 18 mm and a thickness of 500 μm was used. First, the paste of NiAl 2 O 4 : SDC = 10: 90 prepared in “Preparation of fuel electrode paste” was printed in the center of the YSZ electrolyte with a size of φ6 mm using a screen printer. After printing, it was placed in an atmospheric furnace and pre-baked at 400 ° C. for 30 minutes. After that, the NiAl 2 O 4 : SDC = 20: 80 paste prepared in “Preparation of fuel electrode paste” is printed in the same manner so as to be exactly overlapped on the previously formed NiAl 2 O 4 -SDC, and placed in an atmospheric furnace. Temporary baking was performed again at 400 ° C. for 30 minutes. Subsequently, the NiAl 2 O 4 : SDC = 30: 70 paste prepared in “Preparation of fuel electrode paste” was similarly printed on the two layers of NiAl 2 O 4 -SDC previously formed, It baked at 1300 degreeC for 2 hours in the atmospheric furnace. Next, a Pt electrode was similarly printed on the opposite surface of the YSZ electrolyte to form an oxygen electrode, and a Pt reference electrode was applied to the electrolyte side surface, followed by baking at 960 ° C. for 30 minutes. After that, the Ni paste mixed with YSZ powder (Ni: YSZ is mixed so that the weight ratio is 82:18) is printed in the same manner as the fuel electrode paste so that it overlaps exactly on the three-layer structure fuel electrode surface. A current collecting layer was laminated on the fuel electrode surface. Thereafter, heat treatment was performed at 960 ° C. for 30 minutes in an air atmosphere, and the current collecting layer was immobilized on the electrode surface.
＜固体酸化物電気化学セルの作製－３＞（比較例２）
　固体酸化物電解質にはφ１８ｍｍ、厚さ５００μｍに加工したＹＳＺ（８ｍｏｌ％Ｙ２Ｏ３で安定化させたＺｒＯ２）を用いた。始めに前記「燃料極ペーストの調製」で調製したＮｉＡｌ２Ｏ４：ＳＤＣ＝１５：８５のペーストをスクリーン印刷機でＹＳＺ電解質の中央にφ６ｍｍの大きさで印刷した。印刷後、大気炉に入れ、４００℃にて３０分間の仮焼成を行った。その後、前記「燃料極ペーストの調製」で調製したＮｉＡｌ２Ｏ４：ＳＤＣ＝３０：７０のペーストを先に形成したＮｉＡｌ２Ｏ４－ＳＤＣ上にぴったり重なるよう同様に印刷し、大気炉に入れ１３００℃にて２時間焼成を行った。次に、ＹＳＺ電解質の反対面にＰｔ電極を同様に印刷して酸素極とし、また電解質側面にＰｔ参照極を塗って、９６０℃で３０分間焼成した。その後、ＹＳＺ粉末を混合したＮｉペースト（Ｎｉ：ＹＳＺが重量比で８２：１８になるように混合）を、三層構造燃料極表面上にぴったりと重なるように、燃料極ペーストと同様に印刷し、燃料極表面上に集電層を積層した。その後、大気雰囲気中、９６０℃で３０分間の熱処理を施し、集電層を電極表面に固定化した。 <Preparation of Solid Oxide Electrochemical Cell-3> (Comparative Example 2)
As the solid oxide electrolyte, YSZ (ZrO 2 stabilized with 8 mol% Y 2 O 3 ) processed to have a diameter of 18 mm and a thickness of 500 μm was used. First, the paste of NiAl 2 O 4 : SDC = 15: 85 prepared in the above “Preparation of fuel electrode paste” was printed with a screen printer at a size of φ6 mm in the center of the YSZ electrolyte. After printing, it was placed in an atmospheric furnace and pre-baked at 400 ° C. for 30 minutes. Thereafter, the NiAl 2 O 4 : SDC = 30: 70 paste prepared in the above “Preparation of fuel electrode paste” is printed in the same manner so as to be exactly overlapped on the previously formed NiAl 2 O 4 -SDC, and placed in an atmospheric furnace. Firing was performed at 1300 ° C. for 2 hours. Next, a Pt electrode was similarly printed on the opposite surface of the YSZ electrolyte to form an oxygen electrode, and a Pt reference electrode was applied to the electrolyte side surface, followed by baking at 960 ° C. for 30 minutes. After that, the Ni paste mixed with YSZ powder (Ni: YSZ is mixed so that the weight ratio is 82:18) is printed in the same manner as the fuel electrode paste so that it overlaps exactly on the three-layer structure fuel electrode surface. A current collecting layer was laminated on the fuel electrode surface. Thereafter, heat treatment was performed at 960 ° C. for 30 minutes in an air atmosphere, and the current collecting layer was immobilized on the electrode surface.
＜セル特性評価試験＞
　実施例１で作製した平板型固体酸化物電気化学セルと比較例１，２で作製した同セルを出力特性評価装置にセットし、燃料極側、をパイレックス（登録商標）ガラス材によりシールした。電解質側面にφ０．５ｍｍのＰｔ線を付け参照極とした。Ｎ２雰囲気中で昇温したのち、燃料極に水素を導入して還元処理を行った。水素還元時間は１０００℃で３０分間とした。 <Cell characteristic evaluation test>
The flat plate type solid oxide electrochemical cell produced in Example 1 and the same cell produced in Comparative Examples 1 and 2 were set in an output characteristic evaluation apparatus, and the fuel electrode side was sealed with a Pyrex (registered trademark) glass material. A Pt wire having a diameter of 0.5 mm was attached to the side surface of the electrolyte to obtain a reference electrode. After raising the temperature in an N 2 atmosphere, hydrogen was introduced into the fuel electrode to perform a reduction treatment. The hydrogen reduction time was set at 1000 ° C. for 30 minutes.
　次に、燃料極に３０℃で加湿した５０ｍＬ／ｍｉｎのＨ２を、酸素極に１００ｍＬ／ｍｉｎのドライ空気を導入し、セル出力特性を評価した。また、カレントインターラプト法によるＩＲ分離も行った。 Next, 50 mL / min of H 2 humidified at 30 ° C. was introduced into the fuel electrode, and 100 mL / min of dry air was introduced into the oxygen electrode, and the cell output characteristics were evaluated. In addition, IR separation by the current interrupt method was also performed.
＜セル特性評価試験＞
　以下、＜セル特性評価試験＞について説明する。
　実施例１および比較例１，２のセルの電気化学特性評価結果を表１に示す。はじめに、両セルの最大出力密度を比較すると、実施例１の出力密度は、比較例１の出力密度に比べ約８％の出力向上が、比較例２の出力密度に比べ約３２％の出力向上が見られた。次に、燃料極内のオーム抵抗を同様に比較する。電極内オーム抵抗は、端子間のセル抵抗から使用しているＹＳＺ電解質の理論電解質抵抗を引くことで求められ、両セルに用いている厚さ０．５ｍｍのＹＳＺの理論電解質抵抗０．５０;ｃｍ２である。また、酸素極にはＰｔを使用しているため、酸素極側の接触抵抗、電極内抵抗は十分低いとみなし、端子間のセル抵抗から理論電解質抵抗を引くことで、燃料極抵抗とした。両セルの燃料極内オーム抵抗の算出結果を比較すると、実施例１では、ほぼゼロに抑えることができているのに対し、比較例１では０．０１;ｃｍ２の燃料極抵抗が、比較例２では０．０５;ｃｍ２の燃料極抵抗が存在している。以上、セル出力密度、燃料極内オーム抵抗の比較結果から、実施例１のセルの方が比較例１，２よりも特性が高く、燃料極内中央に触媒濃度極大部を持つ構造にしたことによる特性向上効果が表れている。 <Cell characteristic evaluation test>
Hereinafter, <cell characteristic evaluation test> will be described.
Table 1 shows the electrochemical property evaluation results of the cells of Example 1 and Comparative Examples 1 and 2. First, comparing the maximum power density of both cells, the power density of Example 1 is about 8% higher than the power density of Comparative Example 1, and the power density of about 32% higher than the power density of Comparative Example 2. It was observed. Next, the ohmic resistance in the fuel electrode is similarly compared. The ohmic resistance in the electrode is obtained by subtracting the theoretical electrolyte resistance of the YSZ electrolyte used from the cell resistance between the terminals, and the theoretical electrolyte resistance of 0.5 mm YSZ used in both cells is 0.50; cm 2 . Further, since Pt is used for the oxygen electrode, the contact resistance on the oxygen electrode side and the resistance in the electrode are regarded as sufficiently low, and the fuel electrode resistance is obtained by subtracting the theoretical electrolyte resistance from the cell resistance between the terminals. Comparing the calculation results of the ohmic resistance in the fuel electrode of both cells, the fuel electrode resistance of 0.01; cm 2 was compared in Comparative Example 1 while it was suppressed to almost zero in Example 1. In Example 2, an anode resistance of 0.05; cm 2 exists. As described above, from the comparison results of cell output density and ohmic resistance in the fuel electrode, the cell of Example 1 has higher characteristics than Comparative Examples 1 and 2, and has a structure having a catalyst concentration maximum at the center in the fuel electrode. The characteristic improvement effect by appears.
[規則26に基づく補充 28.10.2009]　
Figure WO-DOC-TABLE-1
 [Supplement under rule 26 28.10.2009]
Figure WO-DOC-TABLE-1
　この燃料極内触媒濃度分布の効果は、Ｎｉ担持粒子がアルミニウム酸化物だけでなく、Ｎｉ粒子担持マグネシウム酸化物であっても同程度の効果が期待される。 The effect of the catalyst concentration distribution in the fuel electrode is expected to be comparable even if the Ni-supported particles are not only aluminum oxide but also Ni-particle-supported magnesium oxide.
１１・・・固体電解質板
１２・・・燃料極
１３・・・酸素極
１８・・・燃料極表面近傍領域
１９・・・燃料極中央領域
２０・・・電解質近傍領域
２１，２２・・・集電体
１６・・・電子・イオン混合導電性酸化物粒子
１７・・・金属触媒担持金属酸化物粒子
 
  DESCRIPTION OF SYMBOLS 11 ... Solid electrolyte plate 12 ... Fuel electrode 13 ... Oxygen electrode 18 ... Fuel electrode surface vicinity area | region 19 ... Fuel electrode center area | region 20 ... Electrolyte vicinity area | regions 21, 22 ... Collection Electrode 16 ... Electron / ion mixed conductive oxide particles 17 ... Metal catalyst-supported metal oxide particles

Claims (5)

  1. 　金属触媒、もしくは金属触媒を担持してなる金属触媒担持金属酸化物からなる触媒粒子と、電子・イオン混合導電性粒子との焼結体からなる燃料極を備えた固体酸化物型燃料電池であって、
    　前記燃料極における前記金属触媒の濃度が、前記燃料極の面に垂直方向に不均一であって、前記燃料極の電解質近傍領域と燃料極表面近傍領域との間にある燃料極中央領域において前記金属触媒濃度が極大値を持つことを特徴とする固体酸化物型燃料電池。     A solid oxide fuel cell having a fuel electrode made of a sintered body of a metal catalyst or a metal oxide carrying a metal catalyst carrying a metal catalyst and an electron / ion mixed conductive particle. And
    The concentration of the metal catalyst in the fuel electrode is non-uniform in a direction perpendicular to the surface of the fuel electrode, and in the fuel electrode central region located between the electrolyte vicinity region and the fuel electrode surface region of the fuel electrode. A solid oxide fuel cell characterized in that the metal catalyst concentration has a maximum value.
  2. 　前記燃料極は、前記金属触媒量の多い領域と、該領域と比べ金属触媒量の少ない領域を備えており、これらの界面では触媒含有量が傾斜して存在していることを特徴とする請求項１に記載の固体酸化物型燃料電池。 The fuel electrode includes a region where the amount of the metal catalyst is large and a region where the amount of the metal catalyst is small as compared with the region, and the catalyst content is inclined at these interfaces. Item 2. The solid oxide fuel cell according to Item 1.
  3. 　前記燃料極は、前記金属触媒量の多い領域の金属触媒含有量が、金属触媒量の少ない領域の前記金属触媒含有量の１．５～３倍であることを特徴とする請求項１に記載の固体酸化物型燃料電池。 2. The fuel electrode according to claim 1, wherein the content of the metal catalyst in the region where the amount of the metal catalyst is large is 1.5 to 3 times the content of the metal catalyst in the region where the amount of the metal catalyst is small. Solid oxide fuel cell.
  4. 　前記触媒粒子は、アルミニウムもしくはマグネシウム酸化物表面にＮｉ，Ｃｏ，Ｆｅ，およびＣｕより選ばれる少なくとも一種が担持された構造を備えたものであることを特徴とする請求項１に記載の固体酸化物型燃料電池。 2. The solid oxide according to claim 1, wherein the catalyst particles have a structure in which at least one selected from Ni, Co, Fe, and Cu is supported on the surface of aluminum or magnesium oxide. Type fuel cell.
  5. 　前記触媒金属の粒径が、５ｎｍ以上５００ｎｍ以下であることを特徴とする請求項１に記載の固体酸化物型燃料電池。
          2. The solid oxide fuel cell according to claim 1, wherein a particle diameter of the catalyst metal is 5 nm or more and 500 nm or less.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015114168A1 (en) * 2014-02-03 2015-08-06 Centre National De La Recherche Scientifique (Cnrs) Deep metal deposition in a porous matrix by high power impulse magnetron sputtering (hipims), porous substrates impregnated with metal catalyst and uses thereof
WO2024122787A1 (en) * 2022-12-05 2024-06-13 Samsung Electro-Mechanics Co., Ltd. Solid oxide cell

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JPH1040933A (en) * 1996-07-26 1998-02-13 Kansai Electric Power Co Inc:The Anode film forming method in fuel cell
JP2003151578A (en) * 2001-08-30 2003-05-23 Toto Ltd Manufacturing method of solid electrolyte fuel cell fuel electrode film
JP2009064640A (en) * 2007-09-05 2009-03-26 Toshiba Corp Fuel electrode of solid oxide electrochemical cell, its manufacturing method, and solid oxide electrochemical cell

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JPH1040933A (en) * 1996-07-26 1998-02-13 Kansai Electric Power Co Inc:The Anode film forming method in fuel cell
JP2003151578A (en) * 2001-08-30 2003-05-23 Toto Ltd Manufacturing method of solid electrolyte fuel cell fuel electrode film
JP2009064640A (en) * 2007-09-05 2009-03-26 Toshiba Corp Fuel electrode of solid oxide electrochemical cell, its manufacturing method, and solid oxide electrochemical cell

Cited By (3)

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Publication number Priority date Publication date Assignee Title
WO2015114168A1 (en) * 2014-02-03 2015-08-06 Centre National De La Recherche Scientifique (Cnrs) Deep metal deposition in a porous matrix by high power impulse magnetron sputtering (hipims), porous substrates impregnated with metal catalyst and uses thereof
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WO2024122787A1 (en) * 2022-12-05 2024-06-13 Samsung Electro-Mechanics Co., Ltd. Solid oxide cell

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