JP2012033417A - Solid oxide fuel cell and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell enabling high output, and to provide a method for manufacturing the same.SOLUTION: The solid oxide fuel cell comprises a solid electrolyte layer 11 with oxygen ion conductivity, a fuel electrode 12 formed on one principal surface of the solid electrolyte layer and containing porous sintered bodies 121 composed of an electron-ion mixed conductive material and an oxide film 122 which supports dispersed metal particles 123 formed on at least one part of the surface of the porous sintered bodies, and an air electrode formed on the other principal surface of the solid electrolyte layer.

Description

  Embodiments described herein relate generally to a solid oxide fuel cell and a method for manufacturing the same.

A solid oxide fuel cell (SOFC) is a next-generation clean fuel cell that can reduce the resistance acting inside the cell due to its high operating temperature (700-1000 ° C), realizing high power generation efficiency and low CO ₂ generation. It is expected as a powerful power generation system.

The SOFC fuel electrode is generally formed by cermet of ceramic particles having oxide ion conductivity and metal particles which are a catalyst and have electronic conductivity. Nickel particles that have high catalytic activity at high temperatures and are useful as reforming catalysts for hydrocarbon fuels such as methane are used for the metal particles that are catalysts. For the oxide ion conductive particles, ZrO ₂ (YSZ) stabilized with Y ₂ O ₃ having high oxide ion conductivity at a high temperature is used.

  The electrochemical reaction at the fuel electrode occurs at the interface of hydrogen gas as the fuel, nickel as the catalyst and electronic conductor, and oxide ion conductor, that is, a three-phase interface. Therefore, increasing the amount of the three-phase interface is the key to improving the fuel electrode performance.

  When mixed conductive particles having both oxide ions and electronic conductivity are used instead of YSZ having only oxide ion conductivity, this three-phase interface is increased, and the performance as a fuel electrode is further improved. On the other hand, the nickel particles as a catalyst can increase the three-phase interface (reaction field) as the particle size is reduced and the number is increased, that is, the catalyst specific surface area is increased, and high catalytic activity is expected. However, when the nickel particle size is reduced, there is a problem that the particles are easily aggregated and sintered under a use environment of a high temperature reducing atmosphere.

In view of this, a method has been proposed in which the nickel catalyst particle size is made small and fixed to a substrate (Patent Document 1). Here, a nickel-aluminum complex oxide such as NiAl ₂ O ₄ is used as a catalyst precursor, and reduction treatment is performed to produce nickel particles as an electrode catalyst. Nickel particles produced by this method are precipitated from the inside of NiAl ₂ O _4, are as small as several tens of nanometers, and are firmly fixed to the surface of Al ₂ O ₃ formed as a substrate at the same time. This structural feature is expected to play an anchoring role at high temperatures and maintain stability. Actually, when a nickel catalyst based on Al ₂ O ₃ and SDC (Sm ₂ O ₃ doped CeO ₂ ), which is a mixed conductive particle, are combined to form an electrode, particularly high catalytic activity is exhibited. Has been confirmed.

  In addition, a method has been proposed in which SDC particles are used and nickel fine particles are supported on the surface thereof in a highly dispersed manner (Non-Patent Document 1). In this method, a network-like porous fuel electrode made by sintering SDC is impregnated with an aqueous metal salt solution such as nickel nitrate, and nickel particles are formed by firing. Thereby, the nickel particle size can be reduced to about several tens nm to several hundreds nm, and high catalytic activity is obtained with a smaller amount of added nickel. However, since the nickel particles produced by this method are not particularly fixed to the base material, there are problems that aggregation and sintering are likely to occur and the particle size becomes non-uniform.

  On the other hand, in recent years, further higher output has been demanded, and neither of Patent Document 1 and Non-Patent Document 1 sufficiently satisfy the requirement for such higher output.

JP 2009-64640 A

J. et al. Electrochem. Soc. 141, [2], 342-346, 1994.

  An object of the present invention is to provide a solid oxide fuel cell having a novel configuration capable of increasing output and a method for manufacturing the same.

  The solid oxide fuel cell of the embodiment includes a solid electrolyte layer having oxygen ion conductivity, and porous sintering made of an electron-ion mixed conductive material formed on one main surface side of the solid electrolyte layer. And a fuel electrode including an oxide film formed by dispersing and supporting metal particles formed on at least a part of the surface of the porous sintered body. And an air electrode formed on the other main surface side of the solid electrolyte layer.

It is sectional drawing which shows schematic structure of the solid oxide fuel cell in embodiment. It is sectional drawing which expands and shows the fuel electrode of the solid oxide fuel cell shown in FIG. It is an XRD pattern of the complex oxide film obtained in the example. 2 is a SEM photograph of a fuel electrode obtained in Example 1.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(Solid oxide fuel cell)
FIG. 1 is a cross-sectional view showing a schematic configuration of a solid oxide fuel cell in the present embodiment, and FIG. 2 is an enlarged cross-sectional view showing a fuel electrode of the solid oxide fuel cell shown in FIG. .

  A solid oxide fuel cell 10 shown in FIG. 1 includes a solid electrolyte layer 11 exhibiting oxygen ion conductivity, a fuel electrode 12 formed on the main surface 11A side of the solid electrolyte layer 11, and a solid electrolyte layer 11. It has the air electrode 13 formed in the main surface 11B side opposite to the main surface 11A. Further, current collectors 15 and 16 are formed on the main surfaces 12A and 13A side of the fuel electrode 12 and the air electrode 13 opposite to the solid electrolyte layer 11 via current collecting layers 17 and 18, respectively. .

  In this embodiment, the current collecting layers 17 and 18 and the current collectors 15 and 16 are not essential components, but by providing such a current collecting layer and current collector, a solid oxide fuel is provided. The electric power generated in the battery 10 can be efficiently extracted outside.

The solid electrolyte layer 11 can be composed of, for example, stabilized zirconia. In this case, examples of the stabilizer include Y ₂ O ₃ , Sc ₂ O ₃ , Yb ₂ O ₃ , Gd ₂ O ₃ , Nd ₂ O ₃ , CaO, and MgO. These stabilizers are used as a solid solution in zirconia. Moreover, it can replace with stabilized zirconia and can also comprise perovskite type oxides, such as LaSrGaMg oxide, LaSrGaMgCo oxide, LaSrGaMgCoFe oxide, LaSrGaMgCoFe oxide. Furthermore, a ceria-based electrolyte solid solution in which Sm ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , La ₂ O _{3 and the} like are dissolved in CeO ₂ can also be used. However, the solid electrolyte layer 11 is not limited to these materials, and may be composed of other materials.

  In addition, although the thickness of the solid electrolyte layer 11 can be arbitrarily set according to the objective, it can be set as the range of 0.01 mm-0.5 mm, for example.

As an example, 8 mol% Y ₂ O ₃ stabilized zirconia having a thickness of 0.01 mm can be used.

  As shown in FIG. 2, the fuel electrode 12 includes a porous sintered body 121 made of an electron-ion mixed conductive material and metal particles 123 formed on at least a part of the surface of the porous sintered body 121. An oxide film 122 is included. The metal particles 123 are in contact with the porous sintered body 121 and protrude from the oxide film 122. That is, in the fuel electrode 12 shown in FIG. 2, the porous sintered body 121 has a skeleton, and the metal particles 123 dispersedly supported on the oxide film 122 coated on the surface function as a catalyst.

The porous sintered body 121 is made of an electron-ion mixed conductive material. Specifically, it can be composed of at least one selected from the group consisting of _Sm 2 _{O 3} doped _CeO 2, _Gd 2 _{O 3} doped CeO _2, and _Y 2 _{O 3} doped CeO _2. In this case, since the surface of the porous sintered body 121 becomes an interface between the electronic conductor and the oxide ion conductor, a fuel gas such as hydrogen gas in the solid oxide fuel cell 10 shown in FIG. And the amount of the interface of the oxide ion conductor, that is, the three-phase interface is increased. Therefore, the electrochemical reaction in the fuel electrode 12 is promoted, and the output characteristics of the solid oxide fuel cell 10 can be improved.

  The metal particles 123 have a size of about several nm to 200 nm, and are dispersed and supported on the oxide film 122 as described above. That is, since the fine metal particles 123 of about several nm to 200 nm are supported and fixed on the oxide film 122, aggregation and sintering with respect to the metal particles 123 are unlikely to occur later, and the particle size becomes nonuniform. This does not cause a problem. That is, since the fine metal particles 123 of several nm to 200 nm are stably present and function as a catalyst, the electrochemical reaction at the fuel electrode 12 is promoted as the substantial surface area of the catalyst increases. As a result, the output characteristics of the solid oxide fuel cell 10 can be improved.

The dispersion density of the metal particles 123 is, for example, 10 particles / μm ^{2 to} 10,000 particles / μm ² . Thereby, the catalytic effect of the metal particles 123 can be more effectively exhibited.

  Note that the thickness of the oxide film 122 is preferably in the range of, for example, several nm to several tens of nm so that the metal particles 123 having the above-described size can be exposed from the oxide film 122.

  As a result, in the solid oxide fuel cell 10 according to the present embodiment, the metal dispersed and supported by the porous sintered body 121 made of an electron-ion mixed conductive material and the oxide film 122 formed on the surface thereof. Along with the effect of promoting the electrochemical reaction by the particles 123, sufficiently high output characteristics can be obtained as compared with the conventional case.

  The metal particles 123 are preferably composed of nickel, cobalt, iron, copper, or the like that functions as a catalyst in the electrochemical reaction. In addition, the oxide film 122 is preferably composed of aluminum oxide or magnesium oxide due to a manufacturing method described below.

  Further, as apparent from FIG. 2, the porous sintered body 121 has open pores, so that a fuel gas such as hydrogen or a generated gas smoothly flows through the porous sintered body 121, that is, the fuel electrode 12. Can diffuse. Therefore, the fuel gas can be supplied to the inside of the porous sintered body 121, the three-phase interface can be sufficiently increased, and the metal particles 123 formed inside the porous sintered body 121 are also in contact with each other. To be able to. As a result, the electrochemical reaction in the fuel electrode 12 can be further promoted, and sufficiently high output characteristics can be obtained.

  The porosity of the porous sintered body 121 is preferably 30% to 70%, for example. When the porosity is less than 30%, the generation ratio of the above-described open pores is reduced, and it is difficult to obtain the above-described effects. On the other hand, when the porosity exceeds 70%, the sintered density of the porous sintered body 121 decreases, the strength decreases, and the long-term reliability of the fuel electrode 12 decreases. That is, when the solid oxide fuel cell 10 shown in FIG. 1 is used for a long time, the fuel electrode 12 may be damaged, and its long-term reliability may not be sufficiently maintained.

  Further, it is preferable that the bonded portion of the porous sintered body 121 is firmly bonded without a defect such as a void. This can contribute to the above-described electrochemical reaction at the three-phase interface without hindering the movement of oxygen ions and electrons due to defects in the bonding portion.

  In the present embodiment, as described above, the oxide film 122 may be formed on at least a part of the surface of the porous sintered body 121, but the ratio of the oxide film 122 in the fuel electrode 12 is 0. It is preferably in the range of 1% by volume to 20% by volume.

  When the formation ratio of the oxide film 122 on the porous sintered body 121 exceeds 20% by volume, the covering ratio of the oxide film 122 to the porous sintered body 121 increases. In some cases, the oxide film 122 is formed in the open pores at a sufficiently large coating ratio, and the electrical conductivity of the porous sintered body 121, that is, the movement of oxygen ions and electrons may be hindered. As a result, the substantial electrochemical reaction in the fuel electrode 12 may be reduced, and the output characteristics of the solid oxide fuel cell 10 may be deteriorated.

  On the other hand, when the formation ratio of the oxide film 122 on the porous sintered body 121 is less than 0.1% by volume, the ratio of the metal particles 123 that are dispersed and supported as the formed oxide film 122 decreases. And the catalytic action cannot be fully exerted, and as a result, the output characteristics of the solid oxide fuel cell 10 may be deteriorated.

  The formation ratio of the oxide film 122 is determined by measuring the weight of the porous sintered body 121 before and after the formation of the oxide film 122 in which the metal particles 123 are dispersed and supported. Density), and divided by the theoretical density of the oxide film 122.

  The thickness of the fuel electrode 12 can be set to 5 μm to 50 μm, for example. However, this is not the case when the electrolyte layer is thin and the air electrode is used as the support material.

  Although not particularly shown in FIG. 2, a coating layer made of an electron-ion mixed conductive material constituting the porous sintered body 121 may be provided on the surface of the porous sintered body 121. When the oxide film 122 is formed on the surface of the porous sintered body 121 as described above, the electrical conductivity of the entire fuel electrode 12 is reduced, that is, the resistance is increased, and the resistance is increased when the generated power is taken out to the outside. May cause loss. However, by providing the coating layer, the resistance of the entire fuel electrode 12 can be reduced to increase the electrical conductivity, and the above-described disadvantages can be eliminated.

  In addition, since the entire surface of the coating layer functions as the above-described three-phase interface, the three-phase interface is increased depending on the coating ratio of the coating layer. The output characteristics of the oxide fuel cell 10 can be improved.

The air electrode 13, can be composed of any material used as an oxygen electrode of an electrochemical cell than before, preferably, the general formula _{Ln 1-x A x BO 3} -δ (Ln = rare earth elements; A composite oxide represented by A = Sr, Ca, Ba; at least one of B = Cr, Mn, Fe, Co, and Ni) can be used. Such a composite oxide efficiently dissociates oxygen and has electronic conductivity. Therefore, it is possible to promote an electrochemical reaction between oxygen ions and hydrogen gas via the catalyst in the fuel electrode 12 described below, which contributes to higher output of the solid oxide fuel cell 10. .

  In addition, the thickness of the air electrode 13 can be 5 micrometers-100 micrometers, for example. However, this is not the case when the electrolyte layer is thin and the air electrode is used as the support material.

  The current collecting layer 17 includes a metal material such as nickel, cobalt, iron, copper, platinum, gold, silver, and the like and an electron-ion mixed conductive material that constitutes the porous sintered body 121. It can consist of a mixture. On the other hand, in the case of the current collection layer 18, it can be comprised from the mixture of metal materials, such as platinum, gold | metal | money, silver, and these metal materials and the electron-ion mixed conductive material which comprises the porous sintered compact 121. FIG. . The current collecting layers 17 and 18 reduce the resistance between the fuel electrode 12 and the air electrode 13 with respect to the current collectors 15 and 16 more reliably, and collect the generated power. It is for taking out more efficiently than the body.

  The current collectors 15 and 16 must be made of a material that does not oxidize under normal operating conditions. For example, in addition to precious metals such as gold, silver, and platinum, other base metals such as silver are used. What was coated with can be used. The current collector 15 on the fuel electrode side also allows the use of nickel. A ceramic material having conductivity can also be used. Further, a chromium-based alloy whose oxide film has conductivity can also be used.

(Method for producing solid oxide fuel cell)
Next, the manufacturing method of the 1st solid oxide fuel cell in embodiment is demonstrated. In the present embodiment, the manufacturing method will be described in relation to the solid oxide fuel cell 10 shown in FIGS.

  First, ceramic particles are stacked on the main surface 11A of the solid electrolyte layer 11 if the material is an electron-ion mixed conductive material. Such a laminated arrangement can be performed, for example, by pasting ceramic particles and screen-printing the obtained paste. In addition, when ceramic particles cannot be laminated and arranged in a predetermined thickness by one screen printing, the above-described screen printing may be performed a plurality of times. In addition, it can replace with such screen printing and can substitute by methods, such as sheet forming, application | coating, and dipping.

  In the paste, when the porous sintered body 121 is formed through subsequent sintering, an organic substance such as styrene particles is used so that the porosity is, for example, in the above-described preferable range. A predetermined amount of system particles can be contained.

Next, the paste applied as described above is sintered to form a porous sintered body 121 that forms the skeleton of the fuel electrode 12 as shown in FIG. When the porous sintered body 121 is made of an electron-ion mixed conductive material (ceramic particles) such as the above-described Sm ₂ O ₃ -doped CeO ₂ , the sintering temperature is in the range of 1200 ° C. to 1400 ° C., for example. To do. The sintering atmosphere can be in the air.

  Next, the porous sintered body 121 is impregnated with a metal nitrate solution or a metal sulfate solution, heated to a temperature higher than the decomposition temperature of the metal nitrate or metal sulfate, to decompose the metal nitrate or metal sulfate, The impregnated components are baked and reacted at a high temperature of 1100 ° C. to 1400 ° C. to form a composite oxide film, a so-called catalyst precursor film. In addition, water etc. can be used for the solvent of these metal nitrates and metal sulfates.

  Next, a reduction treatment is performed on the composite oxide film so that the metal contained in the composite oxide film is precipitated in the form of particles, whereby the oxide film 122 in which the metal particles 123 are dispersed and supported is obtained.

  Through the above operation, an oxide film 122 in which metal particles 123 are dispersed and supported is formed on at least a part of the surface of the porous sintered body 121 as shown in FIG. The fuel electrode 12 can be formed.

  In the present embodiment, the metal nitrate becomes the metal particles 123 dispersedly supported on the oxide film 122 through a reduction treatment after forming a composite oxide (catalyst precursor) that is an intermediate product. Preferably, the first metal nitrate containing at least one metal selected from the group consisting of nickel, cobalt, iron, and copper and the oxide film 122 itself are formed through the subsequent reduction treatment. Preferably contains a second metal nitrate containing at least one of aluminum and magnesium. That is, the metal nitrate is preferably a complex metal nitrate composed of a first metal nitrate and a second metal nitrate.

  In this case, a composite oxide film is obtained by thermally decomposing the composite metal nitrate. This composite oxide film is a metal that is easily reduced from the first metal nitrate, that is, nickel, cobalt, iron, and The first oxide containing copper and / or the second oxide containing the metal that is difficult to reduce derived from the second metal nitrate, that is, aluminum and / or magnesium are included. Therefore, by obtaining such a composite oxide and subjecting it to a reduction treatment, the first oxide is easily reduced and the particles constituting the metal particles 123 are precipitated, while the second oxide Remains as oxide film 122 without being reduced.

  Therefore, according to the above aspect, the oxide film 122 in which the metal particles 123 are dispersed and supported by the reduction treatment can be easily formed.

  In the same manner as described above, the metal sulfate also becomes the metal particles 123 dispersed and supported on the oxide film 122 through the subsequent reduction treatment, preferably from the group consisting of nickel, cobalt, iron, and copper. The first metal sulfate containing at least one selected metal and the second metal sulfate which preferably forms at least one of aluminum and magnesium, which constitutes the oxide film 122 itself, through the subsequent reduction treatment. And a salt. Also in this case, the oxide film 122 in which the metal particles 123 are dispersed and supported by the reduction treatment can be easily formed based on the above-described effects.

  Next, the air electrode 13 can be formed by producing a paste containing ceramic particles constituting the air electrode on the main surface 11B of the solid electrolyte 11 by a conventional method, and screen-printing this paste.

  Next, if necessary, current collecting layers 17 and 18 are formed by a conventional method, and current collectors 15 and 16 are formed by a conventional method.

  The reduction treatment can be performed in advance at the stage of manufacturing the solid oxide fuel cell 10, but when the solid oxide fuel cell 10 is actually driven, it is post-treated with hydrogen gas used as a fuel gas. Can be done automatically.

Next, the manufacturing method of the 2nd solid oxide fuel cell in embodiment is demonstrated.
First, on the main surface 11A of the solid electrolyte layer 11, ceramic particles made of an electron-ion mixed conductive material and coated with a metal oxide on the surface thereof are laminated. In addition, the metal oxide coating on the ceramic particles is prepared by preparing ceramic particles made of an electron-ion mixed conductive material, and then immersing or suction filtering the ceramic particles in a metal nitrate or a metal sulfate. The metal oxide is obtained from the metal nitrate or metal sulfate by coating the surface of the ceramic particles with metal nitrate or metal sulfate and heating the obtained coating layer to a temperature equal to or higher than its decomposition temperature.

Next, the stacked ceramic particles are heated and sintered to form a porous sintered body 121 of the fuel electrode 12 made of an electron-ion mixed conductive material. When the porous sintered body 121 is made of an electron-ion mixed conductive material (ceramic particles) such as the above-described Sm ₂ O ₃ -doped CeO ₂ , the sintering temperature is in the range of 1200 ° C. to 1400 ° C., for example. To do. The sintering atmosphere can be in the air.

  Next, a reduction treatment is performed on the metal oxide to deposit the metal contained in the metal oxide in the form of particles, and the deposited metal particles 123 are dispersed and supported, and the oxide film 122 of the fuel electrode 12 is formed. Form.

  Also in this embodiment, when forming ceramic particles coated with a metal oxide, the metal nitrate is dispersed and supported on the oxide film 122 through a subsequent reduction treatment. The first metal nitrate containing at least one metal selected from the group consisting of nickel, cobalt, iron, and copper, and the subsequent reduction treatment, constitute the oxide film 122 itself. , Preferably a second metal nitrate containing at least one of aluminum and magnesium. That is, the metal nitrate is preferably a complex metal nitrate composed of a first metal nitrate and a second metal nitrate.

  In this case, the metal oxide covering the ceramic particles is a first metal oxide containing at least one metal selected from the group consisting of nickel, cobalt, iron, and copper, and a first metal oxide containing at least one of aluminum and magnesium. 2, the metal particles 123 include the metal of the first metal oxide, and the oxide film 122 includes the oxide of the metal in the second metal oxide. It becomes.

  The first metal oxide includes a metal that is easily reduced, i.e., nickel, cobalt, iron, and / or copper, and the second metal oxide includes a metal that is not easily reduced, i.e., aluminum and / or magnesium. Therefore, by obtaining such a composite oxide and subjecting it to a reduction treatment, the first metal oxide is easily reduced and the particles constituting the metal particles 123 are precipitated, while the second metal The oxide remains as an oxide film 122 without being reduced.

  Therefore, according to the above aspect, the oxide film 122 in which the metal particles 123 are dispersed and supported by the reduction treatment can be easily formed.

  In the same manner as described above, the metal sulfate also becomes the metal particles 123 dispersed and supported on the oxide film 122 through the subsequent reduction treatment, preferably from the group consisting of nickel, cobalt, iron, and copper. The first metal sulfate containing at least one selected metal and the second metal sulfate which preferably forms at least one of aluminum and magnesium, which constitutes the oxide film 122 itself, through the subsequent reduction treatment. And a salt. Also in this case, the oxide film 122 in which the metal particles 123 are dispersed and supported by the reduction treatment can be easily formed based on the above-described effects.

  Next, the air electrode 13 can be formed by producing a paste containing ceramic particles constituting the air electrode on the main surface 11B of the solid electrolyte 11 by a conventional method, and screen-printing this paste.

  Next, if necessary, current collecting layers 17 and 18 are formed by a conventional method, and current collectors 15 and 16 are formed by a conventional method.

  The reduction treatment can be performed in advance at the stage of manufacturing the solid oxide fuel cell 10, but when the solid oxide fuel cell 10 is actually driven, it is post-treated with hydrogen gas used as a fuel gas. Can be done automatically.

This embodiment will be described in more detail with reference to examples.
In this embodiment, powder having a specific particle size is used as an example, but the present invention is not limited to this.

Example 1
First, 3 g of SDC powder (Sm _0.2 Ce _0.8 O ₂ ) with an average particle size of 0.3 μm was added to 2% by weight of styrene particles (average particle size of 1 μm), 0.7 cc of water and plastic balls. In addition, the mixture was kneaded using a kneader to prepare a paste-like slurry. This paste was screen-printed at 6 mm in the center on a disk (φ18 mm, thickness 0.5 mm) containing Y ₂ O ₃ stabilized zirconia (YSZ) as a solid electrolyte. This was baked at 1300 ° C. for 2 hours in the atmosphere to burn off the styrene particles and sinter SDC to obtain a porous sintered body constituting the fuel electrode.

Next, nickel nitrate (Ni (NO ₃ ) ₂ · 6H ₂ O) and aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O) were weighed to a molar ratio of 1: 2, and water and isopropyl alcohol were mixed. Was added at a ratio of 1: 1 to prepare a 0.5 mol / l complex nitrate solution. Here, by using a mixed solvent of water and isopropyl alcohol 1: 1, the surface tension of the composite nitrate solution is lowered, and the surface of the porous sintered body can be uniformly impregnated. The porous sintered body obtained as described above was impregnated with the aqueous solution of the composite nitrate, and then fired at 1300 ° C., and the composition of NiAl ₂ O ₄ constituting the fuel electrode on the surface of the porous sintered body A composite oxide film having the following structure was formed.

Next, NiO powder having an average particle diameter of 1 μm and YSZ powder having a diameter of 0.3 μm are weight ratio of 82:18 on the surface of the fuel electrode having the porous sintered body and the composite oxide film having the composition of NiAl ₂ O _4. 0.6 cc of water was added to 3 g of the mixed powder mixed in the above, and the current collecting layer paste obtained by kneading in a kneader with a plastic ball was screen-printed, and the same was conducted in the atmosphere at 960 ° C. for 30 Partial firing was performed to form a current collecting layer.

  Next, platinum paste was screen-printed with a diameter of 6 mm on the counter electrode, and baked in the atmosphere at 960 ° C. for 30 minutes to form an air electrode, whereby a solid oxide fuel cell was obtained.

(Example 2)
In place of the above-mentioned complex nitrate, nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) and magnesium nitrate (Mg (NO ₃ ) ₂ .6H ₂ O) are mixed and dissolved so that the molar ratio is 1: 2. Then, a cell of a solid oxide fuel cell was prepared in the same manner as in Example 1 except that the porous sintered body was impregnated with an aqueous solution of complex nitrate which was made into an aqueous solution of 1.0 mol / l by adding water. Got.

(Example 3)
After immersing SDC particles (Sm _0.2 Ce _0.8 O ₂ ) having an average particle size of 0.3 μm in the aqueous composite nitrate solution of Example 1, suction filtration was performed. After drying, heat treatment was performed at 500 ° C. for 30 minutes, and nitrates were thermally decomposed to produce ceramic particles coated with metal oxide (coated ceramic particles).

Next, 0.7 cc of water was added to 3 g of the coated ceramic powder having an average particle size of 0.3 μm and kneaded with a plastic ball in a kneader to prepare a slurry paste. This paste was screen printed with a size of φ6 mm on one side of a YSZ (8 mol% Y ₂ O ₃ stabilized ZrO ₂ ) solid electrolyte plate processed to φ18 mm and a thickness of 0.5 mm, and in the atmosphere at 1300 ° C. for 2 hours. Sintering was performed. In addition, the current collector layer paste of Example 1 was screen-printed and fired at 1300 ° C. for 2 hours in the same manner to form a current collector layer.

  Next, a platinum paste was screen-printed on the other surface of the electrolyte and fired at 960 ° C. to obtain a solid oxide fuel cell.

Example 4
On the surface of the porous sintered body coated with the composite oxide prepared in Example 1, samarium nitrate (Sm (NO ₃ ) ₃ .6H ₂ O) and cerium nitrate (Ce (NO ₃ ) ₃ .6H ₂ O And a mixed nitrate aqueous solution of 1.0 mol / l by adding water to form a mixed nitrate film. This was heat treated at 1300 ° C. for 2 hours to thermally decompose the nitrate, and on the surface of the SDC porous sintered body covered with the Ni—Al based composite oxide film, Sm _0.2 Ce _0.8 O was further added. _An electron-ion mixed conductive film having _two compositions was formed. Otherwise, a solid oxide fuel cell was produced in the same manner as in Example 1.

(Example 5)
In Example 3, when preparing the paste of the coated ceramic particles, samarium nitrate (Sm (NO ₃ ) ₃ .6H ₂ O) and cerium nitrate (Ce (NO ₃ ) ₃ .6H ₂ O) are used in a molar ratio instead of water. A mixed nitrate aqueous solution mixed 1: 4 was used. The addition amount of the mixed nitrate aqueous solution was 0.45 cc with respect to 2 g of the oxide-coated ceramic particles, and kneaded with a plastic ball in a kneader. The obtained paste was screen printed with a size of φ6 mm on one side of a YSZ (8 mol% Y ₂ O ₃ stabilized ZrO ₂ ) solid electrolyte plate processed to φ18 mm and a thickness of 0.5 mm. Time sintering was performed. In all other respects, a solid oxide fuel cell was produced in the same manner as in Example 3.

(Comparative example)
0.7 g of water was added to 3 g of SDC particles having an average particle diameter of 0.25 μm, and the mixture was made into a paste with a kneader and screen-printed on a YSZ solid electrolyte plate (φ18 mm, thickness 0.5 mm). This was baked in the atmosphere at 1300 ° C. for 2 hours. Further, the current collecting paste is screen-printed thereon, baked at 1300 ° C. for 2 hours, then screen-printed with platinum paste at φ6 mm on the counter electrode, and baked in the atmosphere at 960 ° C. for 30 minutes to form an air electrode. A solid oxide fuel cell was obtained.

In Examples 1 and 3, after the composite oxide film was formed, the EDX composition analysis of the film part was performed. As a result, it was found that the oxide was composed of nickel and aluminum. Separately from this experiment, NiAl ₂ O ₄ was detected by X-ray diffraction analysis of the powder obtained by sintering the composite nitrate at 1300 ° C. (see FIG. 3). Since nickel and aluminum hardly dissolve in the SDC as the base material, the formed complex oxide film is considered to be NiAl ₂ O ₄ which is a spinel type oxide.

  Similarly, in Example 2, NiO and MgO are detected when X-ray diffraction analysis is performed on a powder obtained by sintering composite nitrate at 1300 ° C. Separately, the formed composite oxide film is NiO and MgO. It is inferred that it is a solid solution oxide.

  FIG. 4 is a photograph of the structural structure of the fuel electrode produced in Example 1. It can be seen that nickel fine particles having a size of about 80 nm are present isolated and dispersed. As a result of EDX analysis, it was also found that the layer supporting the nickel particles was an extremely thin aluminum oxide layer.

In addition, Table 1 summarizes the maximum power density in the cell power generation tests of Examples 1 to 5 and Comparative Example. The operating conditions were H ₂ humidified at 30 ° C. at 50 mL / min, and 100 mL / min of dry air was introduced into the oxygen electrode at 900 ° C.

  As apparent from Table 1, the cells of the solid oxide fuel cells in Examples obtained according to the present invention have higher output than the cells of the solid oxide fuel cells obtained in Comparative Examples different from the present invention. It can be seen that it has performance.

  In Examples 1 and 4, in the cell in which the porous sintered body was previously formed, even if an electron-ion mixed conductive layer was formed on the outermost surface portion, there was almost no difference in performance. This is presumably because the porous sintered body composed of SDC has already formed a solid electron-ion conduction network.

  On the other hand, in Example 3, the output characteristics are slightly deteriorated. This is presumably because the oxide covering the ceramic particles was interposed between the particles even in the sintering process, which hindered some of the electron / ion conduction paths. As shown in Example 5, it can be seen that a new conductive path is formed by coating the outermost surface with the SDC film, thereby improving the characteristics.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Solid oxide fuel cell 11 Solid electrolyte layer 12 Fuel electrode 121 Porous sintered body 122 Oxide film | membrane 123 Metal particle 13 Air electrode 15,16 Current collector 17,18 Current collection layer

Claims (11)

A solid electrolyte layer having oxygen ion conductivity;
A porous sintered body formed on one main surface side of the solid electrolyte layer and made of an electron-ion mixed conductive material, and a metal formed on at least a part of the surface of the porous sintered body A fuel electrode including an oxide film in which particles are dispersed and supported;
An air electrode formed on the other main surface side of the solid electrolyte layer;
A solid oxide fuel cell comprising:   2. The solid oxide fuel cell according to claim 1, wherein the metal particles are in contact with the porous sintered body and protrude from the oxide film. 3.   3. The solid oxide fuel cell according to claim 1, wherein a ratio of the oxide film in the fuel electrode is 0.1% by volume to 20% by volume.   The solid oxide fuel cell according to claim 1, wherein the metal particles include at least one metal selected from the group consisting of nickel, cobalt, iron, and copper.   The solid oxide fuel cell according to claim 1, wherein the oxide film includes at least one of aluminum oxide and magnesium oxide. The electron-ion mixed conductive material includes at least one selected from the group consisting of Sm ₂ O ₃ -doped CeO ₂ , Gd ₂ O ₃ -doped CeO ₂ , and Y ₂ O ₃ -doped CeO _2. The solid oxide fuel cell according to any one of claims 1 to 5. If ceramic particles are laminated on one main surface of the solid electrolyte layer having oxygen ion conductivity from an electron-ion mixed conductive material, then the ceramic particles are heated to form the electron-ion mixed conductivity. A step of forming a porous sintered body comprising a fuel electrode and constituting a fuel electrode;
The porous sintered body is impregnated with a metal nitrate solution or a metal sulfate solution and heated to a temperature higher than the decomposition temperature of the metal nitrate or the metal sulfate to decompose the metal nitrate or the metal sulfate. A step of forming an oxide film made of the oxide obtained by
A reduction treatment is performed on the oxide film, the metal contained in the oxide film is deposited in the form of particles, and the deposited metal particles are dispersedly supported to form an oxide film constituting the fuel electrode. And a process of
Forming an air electrode on the other main surface of the solid electrolyte layer;
A method for producing a solid oxide fuel cell, comprising:   The metal nitrate includes a first metal nitrate containing at least one metal selected from the group consisting of nickel, cobalt, iron, and copper, and a second metal nitrate containing at least one of aluminum and magnesium, The solid oxide according to claim 7, wherein the metal particles include a metal in the first metal nitrate, and the oxide film includes an oxide of the metal in the second metal nitrate. Physical fuel cell.   The metal sulfate includes a first metal sulfate containing at least one metal selected from the group consisting of nickel, cobalt, iron, and copper, and a second metal sulfate containing at least one of aluminum and magnesium. The metal particle includes a metal in the first metal sulfate, and the oxide film includes an oxide of a metal in the second metal sulfate. A solid oxide fuel cell according to 1. The ceramic particles are formed by laminating ceramic particles made of an electron-ion mixed conductive material and coated with a metal oxide on one main surface of a solid electrolyte layer having oxygen ion conductivity. A step of forming a porous sintered body made of the electron-ion mixed conductive material and constituting the fuel electrode;
Reduction treatment is performed on the metal oxide, the metal contained in the metal oxide is precipitated in particles, and the deposited metal particles are dispersed and supported to form an oxide film constituting the fuel electrode. And a process of
Forming an air electrode on the other main surface side of the solid electrolyte layer;
A method for producing a solid oxide fuel cell, comprising:   The metal oxide includes a first metal oxide containing at least one metal selected from the group consisting of nickel, cobalt, iron, and copper, and a second metal oxide containing at least one of aluminum and magnesium. 11. The metal particle according to claim 10, wherein the metal particle includes a metal of the first metal oxide, and the oxide film includes an oxide of a metal in the second metal oxide. The manufacturing method of the solid oxide fuel cell of description.

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