JP2007115536A - Manufacturing method of electrode for porous solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode for a porous solid oxide fuel cell having a number of fine pores. <P>SOLUTION: The manufacturing method of the electrode for the porous solid oxide fuel cell comprises a fluid dispersion preparing process preparing fluid dispersion containing metal salt and a pore-making agent, a spraying process for obtaining powdered metal oxide aggregate particles with pores by spraying the fluid dispersion in a heating furnace, an electrode-forming slurry preparation process for preparing slurries for electrode formation containing the powdered metal oxide aggregate particles with pores, and an electrode-forming process for obtaining an electrode for a porous solid oxide fuel cell by molding the slurries for electrode formation into a shape of an electrode, and then baking them. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an electrode for a solid oxide fuel cell having a porous structure.

  A cell of a solid oxide fuel cell is configured such that an electrolyte is sandwiched between a fuel electrode and an air electrode, and the electrolyte, the fuel electrode, and the air electrode are both composed of a metal oxide or a metal, and are all solid. is there.

  In the solid oxide fuel cell, the cell reaction occurs at a three-phase interface where any of gas, ions and electrons can react. Therefore, in order to improve battery performance, it is necessary to increase the three-phase interface.

  Therefore, conventionally, an electrolyte substance is mixed with an electrode substance, and the electrode is made to have a porous structure, so that the three-phase interface is formed not only on the contact surface between the electrolyte and the electrode but also inside the electrode. Increasing the phase interface has been done. Specifically, a child particle is fixed to the mother particle, and either one of the mother particle or the child particle is an electrolyte substance, and a powdery composite particle having the other as a fuel electrode substance or an air electrode substance, Electrode material is mixed with the electrode material by molding into an electrode, and a porous structure electrode has been manufactured (hereinafter, a porous structure electrode manufacturing method using composite particles is referred to as a conventional porous material). (It is also referred to as electrode manufacturing method (I)). In addition, by using a mixed slurry of electrode material particles having a small particle diameter and coarse powder of an electrolyte material having a large particle diameter, the electrolyte material is mixed with the electrode material and the porous structure has a porous structure. Electrodes have been manufactured (hereinafter referred to as a porous electrode manufacturing method using a mixed slurry of electrode material particles having a small particle diameter and electrolyte material coarse powder having a large particle diameter). II)))).

  In the present invention, the fuel electrode material refers to a material that generates water and electrons from hydrogen and oxide ions of the fuel and conducts electrons, and the air electrode material refers to oxides from oxygen and electrons. The substance which has the property which produces | generates ion and conducts an electron points out, and an electrolyte substance points out the substance which has the property which conducts the oxide ion produced | generated by an air electrode to a fuel electrode.

  As a conventional method (I) for producing a porous electrode, for example, Japanese Patent Laid-Open No. 10-144337 of Patent Document 1 discloses that the surface of an oxide having oxygen ion conductivity (for example, yttria stabilized zirconia) is used. A method for producing a fuel electrode for a solid oxide fuel cell using composite particles carrying a metal having electrode activity (for example, nickel oxide) is disclosed.

  As a conventional method (II) for producing a porous electrode, for example, Japanese Patent Application Laid-Open No. 9-245811 discloses a mixed slurry of an air electrode material and a coarse powder of a solid electrolyte material. A method for producing an air electrode ceramic molded body (air electrode) in which the mixed slurry is formed to roughen the surface is disclosed.

JP-A-10-144337 (Example 1) Japanese Patent Laid-Open No. 9-245811 (Example 1)

  In order to further improve battery performance in a porous electrode, the pore diameter in the porous electrode is reduced and the number of pores is increased, that is, a large number of fine pores are formed. Therefore, it is necessary to increase the specific surface area of the porous electrode. In order to form a large number of fine pores, the particles forming the electrode, that is, the composite particles according to the conventional porous electrode manufacturing method (I), or the conventional porous electrode manufacturing method ( The diameters of the electrolyte material particles, fuel electrode material particles, and air electrode material particles according to II) must be further reduced.

  However, if the diameter of the particles forming the electrode is too small, the particles aggregate in the electrode-forming slurry, so that an electrode-forming slurry in which the particles are uniformly dispersed cannot be obtained. And, as the slurry for electrode formation, such a slurry with non-uniform dispersion of particles cannot be used. Therefore, in the conventional method (I) or (II) for producing a porous electrode, particles having a small diameter are used. It was not possible to produce an electrode having many fine pores.

  Accordingly, an object of the present invention is to provide a method for producing an electrode for a porous solid oxide fuel cell having a large number of fine pores.

  As a result of intensive studies to solve the problems in the prior art, the present inventors have (1) spraying a dispersion containing a metal salt and a pore-forming agent into a heating furnace, thereby forming pores. Porous solid oxide having a large number of fine pores by forming powdered metal oxide aggregate particles having the shape of an electrode and then forming the obtained powdered metal oxide aggregate particles into an electrode shape And (2) by spraying a dispersion containing a metal salt and a pore-forming agent into a heating furnace having a temperature lower than the temperature at which the pore-forming agent burns, Porous agent-containing metal salt aggregate particles are obtained, and then the obtained powdery pore-former-containing metal salt aggregate particles are formed into an electrode shape and fired to obtain a porous material having a large number of fine pores. Found that a solid oxide fuel cell electrode can be obtained. Was able to complete.

  That is, the present invention (1) is a dispersion preparation step for preparing a dispersion containing a metal salt and a pore-forming agent, spraying the dispersion onto a heating furnace, and powdered metal oxide aggregates having pores A spraying step for obtaining particles, an electrode forming slurry preparation step for preparing a slurry for forming an electrode containing powdered metal oxide aggregate particles having pores, and the electrode forming slurry in the shape of an electrode The present invention provides a method for producing an electrode for a porous solid oxide fuel cell having an electrode forming step of forming and then firing to obtain an electrode for a porous solid oxide fuel cell.

  Further, the present invention (2) is a dispersion preparation step for preparing a dispersion containing a metal salt and a pore-forming agent, spraying the dispersion on a heating furnace having a temperature lower than the temperature at which the pore-forming agent burns, A spraying step for obtaining powdery pore-former-containing metal salt aggregate particles, an electrode-forming slurry preparation step for preparing an electrode-forming slurry containing the powdery pore-former-containing metal salt aggregate particles, and Provided is a method for producing an electrode for a porous solid oxide fuel cell having an electrode forming step of forming an electrode forming slurry into an electrode shape and then firing it to obtain an electrode for a porous solid oxide fuel cell. Is.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode for porous solid oxide fuel cells which has many fine pores can be provided.

  The method for producing a porous solid oxide fuel cell electrode according to the first embodiment of the present invention (hereinafter also referred to as the production method of the first embodiment of the present invention) contains a metal salt and a pore former. A dispersion preparing step for preparing a dispersion to be sprayed, spraying the dispersion to a heating furnace to obtain powdered metal oxide aggregate particles having pores, and a powder having the pores The electrode forming slurry preparation step (A) for preparing the electrode forming slurry (A) containing the metal oxide aggregate particles is formed into an electrode shape, and then the electrode forming slurry (A) is formed into an electrode shape. There is an electrode forming step (A) for firing to obtain a porous solid oxide fuel cell electrode.

  First, in the dispersion preparation step, the dispersion containing the metal salt and the pore-forming agent is prepared.

  Next, the spraying step (A) is performed. The spraying step (A) will be described with reference to FIG. FIG. 1 is a schematic view showing a state where powdery metal oxide aggregate particles having pores are generated from a dispersion in the spraying step (A). In FIG. 1, (1-1) indicates a droplet 1 of the dispersion before entering the heating furnace (hereinafter also simply referred to as dispersion 1), and (1-2) indicates the structure. 1 shows metal salt aggregate particles 5 containing a pore agent, (1-3) shows metal salt aggregate particles 7 having pores, and (1-4a) shows metal oxide aggregates having pores. The particle | grains 10 are shown and (1-4b) shows the end surface of the metal oxide aggregate particle | grains 10 which have this pore. In (1-3) and (1-4a), the dotted line indicates the inner edge of the pore formed inside the metal salt aggregate particle 7 or the metal oxide aggregate particle 10 having the pore. Show.

  The droplet 1 of the dispersion is a droplet of the dispersion immediately after being sprayed from a nozzle or the like, and the pore-forming agent 3 is dispersed in the spherical metal salt aqueous solution 2. At this time, the pore-forming agent 3 is present inside the droplet 2 of the dispersion.

  Then, the dispersion liquid droplets 1 are heated in the heating furnace, so that water is first evaporated from the dispersion liquid droplets 1, and the metal salt aqueous solution 2 becomes a metal salt aggregate 6. Metal salt aggregate particles 5 containing the pore-forming agent 3 are produced.

  Next, the pore forming agent 3 in the metal salt aggregate particles 5 containing the pore forming agent burns. And when this pore making material 3 burns and burns, a pore is formed and the metal salt aggregate particle 7 which has this pore produces | generates. At this time, the pore-forming agent 3 present inside the metal salt aggregate particles 5 containing the pore-forming agent is burned away, and at the same time, pores are formed in the portion where the pore-forming agent 3 has been burned off. Communicating from the inside of the metal salt aggregate particles 5 containing the pore-forming agent toward the surface by a combustion gas such as carbon dioxide ejected to the outside of the metal salt aggregate particles 5 containing the pore-forming agent A hole 8 is formed.

  Next, the metal salt aggregates 6 of the metal salt aggregate particles 7 having pores are oxidized to form metal oxide aggregates 11 to generate metal oxide aggregate particles 10 having pores. And the structure of the metal oxide aggregate particle 10 which has this pore is a secondary particle which the metal oxide 12 (primary particle) aggregated, as shown to (1-4b).

  In this way, powder metal oxide aggregate particles having the pores are produced in the spraying step (A).

  Next, in the electrode forming slurry preparation step (A), the electrode forming slurry (A) containing the powdered metal oxide aggregate particles having the pores is prepared.

  Next, an electrode forming step (A) is performed. The electrode forming step (A) will be described with reference to FIG. FIG. 2 is a schematic view showing the electrode forming step (A). In (2-1), the electrode forming slurry layer (A) is formed by using the electrode forming slurry (A). It is typical sectional drawing which shows the electrolyte substrate in which (2) was formed, (2-2) is typical sectional drawing which shows the electrolyte substrate in which the electrode was formed. First, the electrode forming slurry (A) 16 containing the metal oxide aggregate particles 10 having the pores is applied to the surface of the electrolyte substrate 15 to form the electrolyte forming slurry (A) layer 17 (2 -1). That is, the electrode forming slurry (A) 16 is formed into an electrode shape. Next, the electrolyte substrate 18 on which the electrode forming slurry (A) layer 17 is formed is baked to obtain the electrolyte substrate 20 on which the electrode 19 is formed (2-2). By the firing, the metal oxide aggregate particles 10 having the pores are sintered at their contact points, and the electrode 19 is formed.

  The electrode 19 obtained by performing the electrode forming step (A) is a porous electrode having many fine pores. The electrode 19 will be described with reference to FIG. FIG. 3 is a schematic enlarged view showing a part of the electrode 19. As shown in FIG. 3 (3-1), the electrode 19 is formed by gathering a large number of metal oxide aggregate particles 10 having the pores. At this time, pores 21 are formed in the electrode 19 by the metal oxide aggregate particles 10a, 10b and 10c. That is, the gaps between the metal oxide aggregate particles 10 are the pores 21.

  (3-2) in FIG. 3 shows the end face of the electrode 19, but the metal oxide aggregate particle 10 is an aggregate of metal oxide 12 which is a primary particle. It is also a collection of many objects 12. That is, the electrode 19 is formed of the metal oxide 12 that is a primary particle, and is a porous electrode having the pores 8 and the pores 21. The pores 8 are very fine because they are formed in the metal oxide aggregate particles 10, and the pores 21 are between the metal oxide aggregate particles 10. It is extremely fine in the gap. In addition, the dotted line of (3-2) in FIG. 3 shows the outline of the powdery metal oxide aggregate particle 10 which has this pore.

  Thus, the porous solid oxide fuel cell electrode having a large number of fine pores is produced by the production method of the first aspect of the present invention.

  The metal salt according to the production method of the first aspect of the present invention varies depending on the type of electrode to be produced. When producing a fuel electrode, the metal salt is (1) converted into a fuel electrode material by being oxidized. Or (2) a mixture of a metal salt that is converted to a fuel electrode material by being oxidized, and a metal salt that is converted to an electrolyte material by being oxidized, yttrium, zirconium, scandium, cerium , Samarium, aluminum, titanium, magnesium, lanthanum, gallium, niobium, tantalum, silicon, gadolinium, strontium, ytterbium, iron, cobalt, nickel, and calcium salts of one or more metals. The metal salt is not particularly limited, and examples thereof include carbonates, sulfates, nitrates, and chloride salts. More specifically, (1) the metal salt that is converted into the fuel electrode material by being oxidized includes nickel carbonate, nickel sulfate, nickel nitrate, cerium nitrate, etc., and (2) by being oxidized. Mixtures of metal salts that can be converted into fuel electrode materials and metal salts that can be converted into electrolyte materials when oxidized include nickel carbonate, nickel sulfate, nickel nitrate or cerium nitrate, yttrium carbonate, scandium nitrate, and nitric acid. Examples thereof include a mixture with zirconium or samarium nitrate. The metal salt may be a combination of two or more metal salts having the same metal species, or a combination of two or more metal salts having different metal species.

  Moreover, when manufacturing an air electrode, the metal salt is (3) a metal salt that is converted into an air electrode material by being oxidized, or (4) a metal salt that is converted into an air electrode material by being oxidized. And yttrium, zirconium, scandium, cerium, samarium, aluminum, titanium, magnesium, lanthanum, gallium, niobium, tantalum, silicon, gadolinium, strontium , A salt of one or more metals selected from ytterbium, iron, cobalt, nickel, manganese and calcium. The metal salt is not particularly limited, and examples thereof include carbonates, sulfates, nitrates, and chloride salts. More specifically, (3) the metal salt that is converted into the air electrode material by being oxidized includes strontium carbonate, lanthanum nitrate, manganese nitrate, cobalt carbonate, etc., and (4) by being oxidized. Mixtures of metal salts that are converted to air electrode materials and metal salts that are converted to electrolyte materials when oxidized include strontium carbonate, lanthanum nitrate, manganese nitrate or cobalt carbonate, yttrium carbonate, scandium nitrate, nitric acid Examples thereof include a mixture with zirconium or samarium nitrate. The metal salt may be a combination of two or more metal salts having the same metal species, or a combination of two or more metal salts having different metal species.

  The pore-forming agent according to the production method of the first aspect of the present invention does not dissolve in the solvent in the dispersion but exists as a solid in the dispersion and burns down in the spraying step (A) (described later) In the case of the pore former according to the production method of the second aspect of the present invention, it does not dissolve in the solvent in the dispersion, exists as a solid in the dispersion, and is an electrode forming step (B) described later. There is no particular limitation as long as it is burned off by firing. Examples of the pore former include carbon powder, thermoplastic resin powder, thermoplastic resin fiber, thermosetting resin powder, thermosetting resin fiber, natural fiber, and natural fiber derivatives.

  The carbon powder related to the pore-forming agent is not particularly limited, and examples thereof include carbon black, activated carbon, graphite (graphite), and amorphous carbon. The content of the metal component in the carbon powder is preferably 100 mg / kg or less, and particularly preferably contains no metal component.

  The thermoplastic resin powder, thermoplastic resin fiber, thermosetting resin powder or thermosetting resin fiber according to the pore former is not particularly limited, and may be a hydrocarbon compound such as polyvinyl butyral or polystyrene. Oxygen-containing organic compounds such as polymethyl methacrylate, phenol resin, and epoxy resin; nitrogen-containing compounds such as polyamide, melamine resin, urea resin, and polyurethane; carbon atoms and hydrogen such as sulfur-containing compounds such as polysulfone It may be a compound containing atoms other than atoms. Of these, hydrocarbon compounds and oxygen-containing organic compounds are preferred in that no gas other than carbon dioxide gas is generated during combustion.

  Examples of natural fibers related to the pore-forming agent include cellulose fibers and protein fibers. The cellulose fibers include semi-artificial acetate and rayon. Examples of the natural fiber derivatives include ethyl esters of natural fibers such as ethyl cellulose.

  When the pore former is a powdery pore former, for example, the carbon powder, the thermoplastic resin powder or the thermosetting resin powder, the average particle diameter of the powder pore former is preferably 1 μm. Hereinafter, it is particularly preferably 0.01 to 0.6 μm, and more preferably 0.05 to 0.4 μm. When the average particle diameter of the powdery pore forming agent is in the above range, pores are also formed near the center of the powdered metal oxide aggregate particles. The specific surface area of the aggregate particles is increased, and the specific surface area of the obtained electrode is increased. Since the pore forming agent has a density lower than the liquid content of the dispersion, the pore forming agent present in the vicinity of the center of the droplet of the dispersion is dispersed in the dispersion droplet. It is easy to move near the surface of the liquid droplet. When a dispersion in which a large amount of the pore-forming agent is present in the vicinity of the surface of the droplet of the dispersion is heated in the heating furnace, the dispersion is only in the vicinity of the surface of the powdered metal oxide aggregate particles. Since pores are not formed, the specific surface area of the powdered metal oxide aggregate particles is reduced. The larger the average particle size of the powdery pore forming agent, the more easily the pore forming agent moves to the vicinity of the surface of the droplets of the dispersion, and therefore the average particle size of the powdered pore forming agent is 1 μm. If it exceeds 1, the specific surface area of the powdered metal oxide aggregate particles tends to be small.

  In addition, when the pore-forming agent is a fibrous pore-forming agent, for example, the thermoplastic resin fiber, the thermosetting resin fiber, the natural fiber, or a derivative of the natural fiber, the fibrous pore-forming agent. The average fiber diameter is 0.01 to 1 μm, preferably 0.05 to 0.5 μm, and the average fiber length of the fibrous pore former is 0.01 to 10 μm, preferably 0.1 to 5 μm. . The fibrous pore former is less likely to move in the vicinity of the surface of the dispersion liquid droplets in the dispersion liquid droplets than the powdery pore formation agent.

  Further, two or more of the carbon powder, the thermoplastic resin powder, the thermoplastic resin fiber, the thermosetting resin powder, the thermosetting resin fiber, natural fiber, and a derivative of natural fiber can be used in combination.

  In the dispersion, the metal salt may exist as an aqueous solution dissolved in a dispersion medium, or may exist in a suspended state dispersed in the dispersion medium as a solid. When the metal salt is difficult to dissolve in water, an acid can be added to dissolve the metal salt. The pore-forming agent is present in the dispersion in a suspended state dispersed in the dispersion medium.

  The content of the metal salt in the dispersion is 0.001 to 100 mol / L, preferably 0.001 to 10 mol / L, particularly preferably 0.01 to 10 mol / L. If the content of the metal salt in the dispersion is less than 0.001 mol / L, the powdered metal oxide aggregate particles are not formed or the powdered metal oxide aggregate particles are likely to be brittle. Moreover, when it exceeds 100 mol / L, the metal salt tends to block the nozzle or the like.

  Further, since the particle size of the powdered metal oxide aggregate particles varies depending on the content of the metal salt in the dispersion, the pores can be formed by appropriately selecting the content of the metal salt. The average particle diameter of the powdered metal oxide aggregate particles can be controlled.

  The content of the pore-forming agent in the dispersion is preferably 0.1% by mass or more, particularly preferably 0.5 to 10% by mass, and further preferably 1 to 5% by mass. When the content of the pore-forming agent is in the above range, the specific surface area of the powdered metal oxide aggregate particles is increased, so that the specific surface area of the obtained electrode is increased. Since the pore-forming agent easily moves to the vicinity of the surface of the droplet in the dispersion liquid droplets, if the content of the pore-forming agent is too small, the pore-forming agent is present inside the dispersion liquid droplets. The pore-forming agent tends to decrease. Therefore, when the content of the pore former is less than 0.1% by mass, the specific surface area of the powdered metal oxide aggregate particles tends to be small.

  The method for preparing the dispersion is not particularly limited. For example, the metal salt is dissolved in water to obtain an aqueous solution containing the metal salt, and then the pore former is mixed with the aqueous solution. Examples thereof include a method of dispersing, or a method of simultaneously mixing the metal salt and the pore-forming agent in water and simultaneously dissolving or dispersing the metal salt and dispersing the pore-forming agent.

  The spraying step (A) according to the production method of the first aspect of the present invention comprises (i) evaporating water from the droplets of the dispersion, (ii) the pore-forming agent in the metal salt aggregate particles And (iii) oxidizing the metal salt in the metal salt aggregate particles. Further, (i), (ii) and (iii) may be performed simultaneously or stepwise.

  The method for spraying the dispersion liquid on the heating furnace is not particularly limited. For example, the dispersion liquid is pressurized with a pump and the droplets of the dispersion liquid are sprayed from the tip of a nozzle, or the method using an ultrasonic spray element. And a method of placing a droplet of the dispersion on a rotatable disk and flying the droplet by centrifugal force.

  In the spraying step (A), the metal salt is oxidized and converted into a metal oxide. Therefore, the heating furnace according to the spraying step (A) has a region set to a temperature equal to or higher than the temperature at which the metal salt is oxidized, and varies depending on the type of the metal salt, preferably 500 ° C. or higher, Particularly preferably, it has a region set at 500 to 1200 ° C, more preferably 800 to 1200 ° C.

  The heating furnace may be a single-stage heating furnace or a multi-stage heating furnace in which a plurality of heating furnaces having different set temperatures are connected. The temperatures for performing the above (i), (ii) and (iii) are different, and increase in the order of (i) <(ii) <(iii).

  Therefore, when the heating furnace has one stage, all of (i) to (iii) are performed in the one-stage heating furnace. In this case, the temperature of the heating furnace is equal to or higher than the temperature at which the metal salt is oxidized, preferably 500 ° C. or higher, particularly preferably 500 to 1200 ° C., and more preferably 800 to 1200 ° C.

  In addition, the heating furnace can be a two-stage heating furnace, and (i) can be performed in the first stage, and (ii) and (iii) can be performed in the second stage. In this case, the temperature in the first stage is preferably 100 to 600 ° C. Is 100 to 400 ° C, and the temperature of the latter stage is 400 to 1200 ° C, preferably 600 to 1200 ° C. Alternatively, (i) and (ii) can be performed in the former stage and (iii) can be performed in the latter stage. In this case, the temperature in the former stage is 100 to 800 ° C., preferably 300 to 800 ° C., and the temperature in the latter stage is 600. It is -1200 degreeC, Preferably it is 800-1200 degreeC.

  Moreover, this heating furnace can be made into a three-stage heating furnace, (i) can be performed in the preceding heating furnace, (ii) can be performed in the middle heating furnace, and (iii) can be performed in the subsequent heating furnace. In this case, the temperature of the former stage is 100 to 600 ° C., preferably 100 to 500 ° C., the temperature of the middle stage is 400 to 800 ° C., preferably 600 to 800 ° C., and the temperature of the latter stage is 600 to 1200 ° C., preferably 800 to 1200 ° C. It is.

  Further, the heating furnace can be a four-stage heating furnace. In this case, the first stage temperature is 100 to 400 ° C., preferably 100 to 300 ° C., the second stage temperature is 300 to 700 ° C., preferably 300 to 600 ° C., and the third stage temperature is 500 to 900 ° C. Preferably, the temperature in the fourth stage is 700 to 1200 ° C, preferably 800 to 1200 ° C.

  Furthermore, the set temperature of the heating furnace can be further subdivided to make the heating furnace into a heating furnace having five or more stages.

  And the particle | grains which passed this heating furnace are collected using a filter etc., and the powdery metal oxide aggregate particle | grains which have this pore are obtained.

The powdered metal oxide aggregate particles having pores obtained by the spraying step (A), when producing a fuel electrode, (5) an aggregate of metal oxide as a fuel electrode material, or ( 6) It is an aggregate of a metal oxide that is a fuel electrode material and a metal oxide that is an electrolyte material. When an air electrode is manufactured, (7) an aggregate of metal oxide that is an air electrode material Or (8) an aggregate of a metal oxide that is an air electrode material and a metal oxide that is an electrolyte material. The metal oxide as the anode material is yttrium, zirconium, scandium, cerium, samarium, aluminum, titanium, magnesium, lanthanum, gallium, niobium, tantalum, silicon, gadolinium, strontium, ytterbium, iron, cobalt, nickel and calcium. More specifically, the metal oxide as the fuel electrode material may be, for example, nickel oxide (NiO) and samaria-doped ceria (Sm ₂ O). aggregates of mixtures of ₃ -CeO _2), aggregates of mixtures of nickel oxide and yttria-stabilized zirconia (NiO-YSZ) aggregates of a mixture of nickel oxide and scandia-stabilized zirconia (NiO-ScSZ), nickel oxide Yttria stabilized zirconia and summary Aggregates of mixtures of doped ceria, aggregates of mixtures of nickel oxide and scandia-stabilized zirconia and samaria-doped ceria, aggregates of mixtures of nickel oxide and yttria-stabilized zirconia and oxide ceria (CeO _2), nickel oxide and scandia-stabilized Aggregates of a mixture of zirconia and ceria oxide, aggregates of a mixture of cobalt oxide (Co ₃ O ₄ ) and yttria stabilized zirconia, aggregates of a mixture of cobalt oxide and scandia stabilized zirconia, ruthenium oxide (RuO ₂ ) and yttria Aggregates of a mixture of stabilized zirconia, aggregates of a mixture of ruthenium oxide and scandia stabilized zirconia, aggregates of a mixture of nickel oxide and gadolinia doped ceria (Gd ₂ O ₃ —CeO ₂ ), and the like can be given. Further, the metal oxide as the air electrode material is yttrium, zirconium, scandium, cerium, samarium, aluminum, titanium, magnesium, lanthanum, gallium, niobium, tantalum, silicon, gadolinium, strontium, ytterbium, iron, cobalt, nickel. , An oxide of one or more metals selected from calcium and manganese (Mn). More specifically, examples of the metal oxide as the air electrode material include lanthanum strontium manganate (La _0.8 Sr _0.2 MnO ₃ ), lanthanum calcium cobaltate (La _0.9 Ca _0.1 CoO ₃ ), lanthanum strontium cobaltate (La _0.9 Sr _0.1 CoO ₃ ), lanthanum cobaltate (LaCoO) _3), lanthanum calcium Manganate _{(La 0.9 Ca} 0.1 MnO _3), and the like. Further, the metal oxide as the electrolyte substance is selected from yttrium, zirconium, scandium, cerium, samarium, aluminum, titanium, magnesium, lanthanum, gallium, niobium, tantalum, silicon, gadolinium, strontium, ytterbium, iron, cobalt, and nickel. One or more metal oxides, and more specifically, examples of the metal oxide that is the electrolyte material include scandia-stabilized zirconia (ScSZ; Sc ₂ O ₃ —ZrO ₂ ), Lanthanum gallate such as yttria stabilized zirconia (YSZ; Y ₂ O ₃ —ZrO ₂ ), lanthanum strontium magnesium gallate (LSGM; La _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O ₃ ), and gadolinia stabilization zirconia _{(Gd 2} O 3 -Z O _2), samaria-doped ceria _{(Sm 2 O 3 -CeO 2)} , gadolinia-doped ceria _{(Gd 2 O 3 -CeO 2)} , like can be mentioned yttrium oxide solid solution of bismuth oxide _{(Y 2 O 3 -Bi 2 O} 3) It is done. In the case of (6) above, each secondary particle is formed by agglomeration of metal oxide primary particles that are fuel electrode materials and metal oxide primary particles that are electrolyte materials. In the case of 8), each secondary particle is formed by agglomeration of metal oxide primary particles that are air electrode materials and metal oxide primary particles that are electrolyte materials. That is, in the case of the above (6), the powdered metal oxide aggregate particles having the pores obtained by the spraying step (A) are the metal oxide that is the fuel electrode material and the metal oxide that is the electrolyte material. In the case of the above (8), both a metal oxide that is an air electrode material and a metal oxide that is an electrolyte material are included.

The specific surface area of the powdered metal oxide aggregate particles having pores is 1 to 50 m ² / g, preferably 3 to 40 m ² / g, particularly preferably 5 to 30 m ² / g.

  Confirmation that the powdered metal oxide aggregate particles having the pores have communication holes therein is obtained by, for example, melting the powdered metal oxide aggregate particles having the pores. After being added to the epoxy resin, it is cooled and included in the epoxy resin, and then the obtained inclusions are cut out using an ultramicrotome to obtain a measurement sample with a thickness on the order of several tens of nm, and then the measurement sample Is observed with a transmission electron microscope.

  In the electrode-forming slurry preparation step (A), for example, the powdered metal oxide aggregate particles having the pores are mixed in a solvent and stirred, whereby the powdered metal having the pores is stirred. The oxide aggregate particles are dispersed in a solvent, and an electrode forming slurry (A) containing the powdery metal oxide aggregate particles having the pores is prepared.

  The average particle diameter of the powdered metal oxide aggregate particles having pores is 0.05 to 10 μm, preferably 0.1 to 5 μm, and particularly preferably 0.1 to 2 μm. When the average particle diameter of the powdered metal oxide aggregate particles having the pores is in the above range, the powdered metal oxide aggregate particles having the pores are uniformly dispersed. A slurry (A) is obtained. The average particle diameter of the powdered metal oxide aggregate particles having pores may be controlled by the size of droplets of the dispersant sprayed to the heating furnace in the spraying step (A). it can.

  The electrode-forming slurry (A) can further contain powdered electrolyte substance aggregate particles. The powdery electrolyte substance aggregate particles are not particularly limited as long as they are powdery electrolyte substance aggregate particles usually used in solid oxide fuel cells. The powder-like electrolyte substance aggregate particles are aggregates of metal oxide that is an electrolyte substance. The metal oxide as the electrolyte substance is the same as the metal oxide as the electrolyte substance described in the explanation of the powdered metal oxide aggregate particles having the pores obtained by the spraying step (A). It is.

  In addition, the electrode forming slurry (A) is dissolved in a solvent, so that a polyvinyl butyral resin that functions as a binder, a binder component such as ethyl cellulose, and a plasticizer component such as di-n-butyl phthalate that functions as a plasticizer. Further, it can contain a dispersant component such as a nonionic dispersant and an antifoam component such as octylphenyl ether. The binder component, plasticizer component, dispersant component or antifoam component is present dissolved in the liquid component of the electrode forming slurry (A).

  In the electrode forming step (A), the method for forming the electrode forming slurry (A) into an electrode shape is not particularly limited, and examples thereof include a screen printing method and a doctor plate method. After the electrode-forming slurry (A) is formed into an electrode shape, that is, after the electrode-forming slurry (A) layer is formed, the electrode-forming slurry (A) layer can be dried as necessary. .

  In the electrode forming step (A), the firing temperature when firing the electrode forming slurry (A) formed into the shape of the electrode is 1100 to 1600 ° C., preferably 1100 to 1500 ° C., and the firing time is 1 -20 hours, preferably 3-10 hours.

  Confirmation that the porous solid oxide fuel cell electrode obtained by performing the electrode forming step (A) has a large number of fine pores is made by surface observation with a scanning electron microscope (SEM). Is called.

  In the production method of the first aspect of the present invention, the particles to be contained in the electrode forming slurry (the powdered metal oxide aggregate particles having the pores) do not aggregate in the electrode forming slurry. Since it has a particle size large enough to be uniformly dispersed, the electrode-forming slurry (A) can be used as the electrode-forming slurry. And the electrode manufactured using this slurry for electrode formation (A) is formed with the metal oxide 12 (primary particle) with a small particle size, as shown to (3-2) in FIG. This is a porous structure having a large number of pores 8 and 21. On the other hand, in the conventional electrode manufacturing methods (I) and (II), an electrode having the same number of pore diameters of the same size as the electrodes obtained by the manufacturing method of the first embodiment of the present invention is manufactured. In order to achieve this, an electrode-forming slurry must be prepared using metal oxide particles having a particle size similar to that of the metal oxide 12, that is, particles having a particle size approximately equal to that of the primary particles. However, the smaller the particle size of the metal oxide aggregate particles, the easier it is to aggregate in the electrode forming slurry. If the particle size is the same as that of the metal oxide 12, the metal oxide aggregate particles in the electrode forming slurry. Since a large number of particles are aggregated, only a slurry with nonuniform dispersion of particles can be obtained. Such a slurry with non-uniform particle dispersion cannot be used as a slurry for forming an electrode. That is, in the conventional electrode manufacturing methods (I) and (II), an electrode having the same number of pore diameters as the electrodes obtained by the manufacturing method of the first aspect of the present invention is manufactured. It is not possible.

  The method for producing a porous solid oxide fuel cell electrode according to the second aspect of the present invention (hereinafter also referred to as the production method according to the second aspect of the present invention) contains a metal salt and a pore former. A dispersion preparing step for preparing a dispersion, and a spraying step for spraying the dispersion onto a heating furnace having a temperature lower than the temperature at which the pore forming agent burns to obtain powdery pore forming agent-containing metal salt aggregate particles (B ), An electrode-forming slurry preparation step (B) for preparing the electrode-forming slurry (B) containing the powdery pore-former-containing metal salt aggregate particles, and the electrode-forming slurry (B) as an electrode The electrode forming step (B) is then performed to obtain a porous solid oxide fuel cell electrode.

The metal salt, pore former and dispersion preparation step according to the production method of the second aspect of the present invention include:
This is the same as the metal salt, pore former and dispersion preparation step according to the production method of the first aspect of the present invention.

  In the spraying step (B), the dispersion liquid is sprayed onto a heating furnace at a temperature higher than the temperature at which water in the droplets of the dispersion liquid evaporates and less than the temperature at which the pore-forming agent burns. Moisture in the droplets of the dispersion liquid is evaporated, and the pore-forming agent is present inside the metal salt aggregate as shown in (1-2) in FIG. Metal salt aggregate particles are obtained. In addition, the powdery pore-former-containing metal salt aggregate particles obtained by performing the spraying step (B) may be partially oxidized.

  The temperature of the heating furnace related to the spraying step (B) is a temperature higher than the temperature at which the water in the droplets of the dispersion evaporates and a temperature lower than the temperature at which the pore former burns, and the pore former The temperature is preferably 100 to 700 ° C, particularly preferably 100 to 600, and more preferably 100 to 400 ° C.

  In the spraying step (B), the method of spraying the dispersion liquid to the heating furnace is the same as the method of spraying the dispersion liquid to the heating furnace in the spraying step (A).

  In the electrode-forming slurry preparation step (B), the electrode-forming slurry (B) is prepared by dispersing the powdery pore-former-containing metal salt aggregate particles in a solvent.

  The average particle size of the powdery pore-former-containing metal salt aggregate particles is 0.1 to 20 μm, preferably 0.1 to 10 μm, and particularly preferably 0.1 to 5 μm. When the average particle diameter of the powdery pore forming agent-containing metal salt aggregate particles is in the above range, an electrode forming slurry in which the powdery pore forming agent-containing metal salt aggregate particles are uniformly dispersed is obtained. It is done. The average particle size of the powdery pore-former-containing metal salt aggregate particles can be controlled by the size of droplets of the dispersion sprayed to the heating furnace in the spraying step (B). .

The electrode-forming slurry (B) can further contain powdered electrolyte substance aggregate particles. The powdery electrolyte substance aggregate particles are not particularly limited as long as they are powdery electrolyte substance aggregate particles usually used in solid oxide fuel cells. The powder-like electrolyte substance aggregate particles are aggregates of metal oxide as an electrolyte substance, and the metal oxides constituting the powder-like electrolyte substance aggregate particles are yttrium, zirconium, scandium, cerium, samarium. An oxide of one or more metals selected from aluminum, titanium, magnesium, lanthanum, gallium, niobium, tantalum, silicon, gadolinium, strontium, ytterbium, iron, cobalt and nickel. More specifically, as the metal oxide constituting the powdery electrolyte material aggregate particles, e.g., scandia-stabilized zirconia _{(ScSZ; Sc 2 O 3 -ZrO} 2), yttria stabilized zirconia (YSZ; Y Lanthanum gallate such as ₂ O ₃ —ZrO ₂ ), lanthanum strontium magnesium gallate (LSGM; La _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O ₃ ), gadolinia stabilized zirconia (Gd ₂ O ₃ —ZrO) ₂ ), samaria doped ceria (Sm ₂ O ₃ —CeO ₂ ), gadolinia doped ceria (Gd ₂ O ₃ —CeO ₂ ), yttrium oxide solid solution bismuth oxide (Y ₂ O ₃ —Bi ₂ O ₃ ) and the like. .

  In addition, the electrode forming slurry (B) is dissolved in a solvent, so that a polyvinyl butyral resin that functions as a binder, a binder component such as ethyl cellulose, and a plasticizer component such as di-n-butyl phthalate that functions as a plasticizer. Further, it can contain a dispersant component such as a nonionic dispersant and an antifoam component such as octylphenyl ether. The binder component, plasticizer component, dispersant component or antifoaming agent component is present dissolved in the liquid component of the electrode forming slurry (B).

  In the electrode forming step (B), the method for forming the electrode forming slurry (B) into an electrode shape is not particularly limited, and examples thereof include a screen printing method and a doctor plate method. After the electrode-forming slurry (B) is formed into an electrode shape, that is, after the electrode-forming slurry (B) layer is formed, the electrode-forming slurry (B) layer can be dried as necessary. .

  In the electrode forming step (B), the firing temperature when firing the electrode forming slurry (B) formed into the shape of the electrode is 1100 to 1600 ° C., preferably 1100 to 1500 ° C., and the firing time is 1 -20 hours, preferably 3-10 hours. By performing the firing, the pore-forming agent present inside the powdery pore-former-containing metal salt aggregate particles is burned out, and communication holes are formed in the metal salt aggregate, The metal salt is oxidized to a metal oxide. That is, the powdery pore-former-containing metal salt aggregate particles are converted into powdered metal oxide aggregate particles having the pores. In the firing, the powdered metal oxide aggregate particles having the pores are further sintered to form an electrode.

  Confirmation that the porous solid oxide fuel cell electrode obtained by carrying out the electrode forming step (B) has a large number of fine pores is made by surface observation with a scanning electron microscope (SEM). Is called.

  In the production method of the second embodiment of the present invention and the production method of the first embodiment of the present invention, the timing for forming pores in the metal oxide aggregate particles forming the electrode depends on the shape of the electrode. Although the latter is different from that after forming into the shape of the electrode, the latter is different in the manufacturing method of the second embodiment of the present invention from the manufacturing method of the first embodiment of the present invention. Similarly, in the preparation of the slurry for electrode formation, particles having a particle size large enough to be uniformly dispersed without aggregation in the slurry for electrode formation (the powdery pore-forming metal-containing salt aggregates) In the slurry for electrode formation (B) according to the production method of the second aspect of the present invention, the powdery pore-former-containing metal salt aggregate particles are uniformly dispersed in the slurry. Yes. That is, the electrode forming slurry (B) can be used as the electrode forming slurry. Then, by firing the electrode forming slurry (B) formed into the shape of the electrode, pores are formed in the metal salt aggregate particles, and further, the metal salt is converted into a metal oxide. As in the case of the electrode obtained by the manufacturing method according to the first aspect of the present invention, the fine pores 8 and the metal oxide 12 are formed as primary particles as shown in (3-2) in FIG. An electrode having a large number of pores 21 is obtained.

  Thus, according to the manufacturing method of the first aspect of the present invention and the manufacturing method of the second aspect of the present invention, an electrode having a large number of fine pores can be manufactured as compared with the conventional manufacturing method. Therefore, an electrode having a large specific surface area, that is, an electrode having many three-phase interfaces can be manufactured.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.

Example 1
(Preparation of dispersion)
3.12 g of lanthanum nitrate hexahydrate, 0.38 g of strontium nitrate and 2.87 g of manganese nitrate hexahydrate were weighed, added to 100 ml of pure water, and heated to 50-80 ° C. with stirring to prepare an aqueous solution. . To this aqueous solution, 1.5% by mass of polymethyl methacrylate particles (manufactured by Soken Chemical Co., Ltd.) having an average particle diameter of 400 nm was added and stirred to prepare a dispersion.

(Dispersion spray)
Next, the dispersion is placed in an electric furnace of an ultrasonic spray pyrolysis apparatus (manufactured by Nishiyama Seisakusho Co., Ltd.) in which the temperature of the former stage is set to 300 ° C., the temperature of the middle stage is set to 650 ° C., and the temperature of the latter stage is set to 1000 ° C. , Sprayed at an air flow rate of 1 L / min, and collected particles passed through a subsequent electric furnace with a filter made of Teflon (registered trademark). It is described as powdered metal oxide aggregate particles A.). The powdered metal oxide aggregate particles A are particles having a particle diameter of 0.2 to 2 μm, an average particle diameter of 1.5 μm, a specific surface area of 10.2 m ² / g, and X-ray diffraction analysis As a result, it was found to be lanthanum-strontium-manganate (La _0.8 Sr _0.2 MnO ₃ ).

(Observation with a scanning electron microscope)
When the surface of the powdered metal oxide aggregate particles A was observed using a scanning electron microscope, 0.2 μm pores were observed on the surface as shown in FIG.

(Observation with transmission electron microscope)
The powdered metal oxide aggregate particles A were added to a molten epoxy resin in a 10 × 10 mm container, then cooled and included in the epoxy resin. Next, the obtained inclusion was cut out using an ultramicrotome to obtain a measurement sample having a thickness of 0.05 μm. When the measurement sample was observed with a transmission electron microscope, it was confirmed that a large number of pores were formed inside the powdered metal oxide particles A as shown in FIG.

(Create electrode)
The powdered metal oxide aggregate particles A and scandia-stabilized zirconia powder (ScSZ; containing 10 mol% of Sc ₂ O ₃ in ZrO _{2 and} having an average particle size of 0.5 μm) are added to isopropyl alcohol as a solvent. An electrode forming slurry was prepared by mixing at a ratio of 80:20 and further mixing polyvinyl butyral as a binder. And using this slurry for electrode formation, it formed into a film by the doctor plate method and created the electrode tape. Next, the electrode tape was baked at 1250 ° C. to prepare an electrode B.

(Observation with a scanning electron microscope)
FIG. 6 shows the result of surface observation of the electrode B using a scanning electron microscope.

(Electrode performance evaluation)
On one surface of a scandia-stabilized zirconia sintered body (diameter: 16 mm, thickness: 2 mm), the electrode-forming slurry used to prepare the electrode B was screen-printed to form a film having a thickness of 30 μm and a diameter of 6 mm. . Next, platinum was screen-printed in the same manner on the other surface and baked at 1250 ° C. A platinum net with a platinum wire was pressed on both sides, and a platinum wire was wound around the side surface of the zirconia sintered body to obtain a reference electrode. When the reaction resistance of the oxygen reduction reaction was determined by an alternating current impedance method at 1000 ° C. in oxygen, the reaction resistance was 0.16 Ω · cm ² .

(Comparative Example 1)
(Preparation of dispersion, spraying of dispersion, creation of electrode, performance evaluation of electrode)
As a dispersion, 3.12 g of lanthanum nitrate hexahydrate, 0.38 g of strontium nitrate and 2.87 g of manganese nitrate hexahydrate were weighed, added to 100 ml of pure water, and heated to 50-80 ° C. with stirring. An electrode E was prepared in the same manner as in Example 1 except that the prepared dispersion was used. That is, the electrode E and the electrode B are different in the manufacturing process in that the dispersion does not contain a pore-forming agent while the latter contains a pore-forming agent, and the others are the same. The reaction resistance of the electrode E was 0.22 Ω · cm ² .

(Observation with a scanning electron microscope)
The result of surface observation of the electrode E using a scanning electron microscope is shown in FIG.

  Comparing the structure of the electrode B obtained in Example 1 and the electrode E obtained in Comparative Example 1, the size of the particles constituting the electrode B is larger than that of the particles constituting the electrode E. The diameter of the pores formed in the electrode B is smaller than the diameter of the pores formed in the electrode E, and the number of pores formed in the electrode B is More than the number of pores formed in As a result, according to the method for producing an electrode for a porous solid oxide fuel cell of the present invention, many fine pores are formed as compared with the conventional method for producing an electrode for a porous solid oxide fuel cell. It shows that it can be done.

(Example 2)
(Preparation of dispersion)
A dispersion was prepared in the same manner as in Example 1.

(Dispersion spray)
Next, the dispersion is sprayed at an air flow rate of 1 L / min into an electric furnace of an ultrasonic spray pyrolysis apparatus set at 400 ° C., and particles passing through the electric furnace are made of Teflon (registered trademark). To obtain powdery pore-forming agent-containing metal salt aggregate particles F. The powdery pore-former-containing metal salt aggregate particles F had a particle size of 0.5 to 4 μm, an average particle size of 3.1 μm, and a specific surface area of 6.1 m ² / g.

(Create electrode)
In isopropyl alcohol as a solvent, the powdery pore-former-containing metal salt aggregate particles F and scandia-stabilized zirconia powder (containing 10 mol% of Sc ₂ O ₃ in ScSZ, ZrO ₂ , average particle diameter of 0.5 μm) Were mixed at a mass ratio of 80:20, and polyvinyl butyral was further mixed as a binder to prepare a slurry for electrode formation. And using this slurry for electrode formation, it formed into a film by the doctor plate method and created the electrode tape. Next, the electrode tape was baked at 1250 ° C. to prepare an electrode G.

(Electrode performance evaluation)
The reaction resistance of the electrode was measured by the same method as in Example 1 except that the electrode forming slurry used for the production of the electrode G was used. The reaction resistance of the electrode was 0.18 Ω · cm ² . there were.

(Observation with a scanning electron microscope)
As a result of observing the surface of the electrode G using a scanning electron microscope, the electrode G may have many fine pores as in the case of the electrode B obtained in the electrode example 1. confirmed.

It is a schematic diagram which shows a mode that the powder-form metal oxide aggregate particle | grains which have a pore are produced | generated from a dispersion liquid by the spraying process (A). It is a schematic diagram which shows an electrode formation process (A). 3 is a schematic enlarged view showing a part of an electrode 19. FIG. 2 is a SEM photograph of powdered metal oxide aggregate particles A according to Example 1. 2 is a TEM photograph of powdered metal oxide aggregate particles A according to Example 1. FIG. 2 is a SEM photograph of electrode B obtained in Example 1. 4 is a SEM photograph of electrode E obtained in Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Droplet of dispersion liquid 2 Metal salt aqueous solution 3 Pore forming agent 5 Metal salt aggregate particle 6 containing pore forming agent Metal salt aggregate 7 Metal salt aggregate particle 8 having pores 21, 21 Pore 10, 10a, 10b, 10c Metal oxide aggregate particles having pores 11 Metal oxide aggregate 12 Metal oxide (primary particles)
15 Electrolyte substrate 16 Slurry for electrode formation (A)
17 Electrode forming slurry (A) layer 18 Electrolyte substrate 19 on which electrode forming slurry (A) layer 17 is formed Electrode 20 Electrolyte substrate on which electrode 19 is formed

Claims (4)

  A dispersion preparation step for preparing a dispersion containing a metal salt and a pore forming agent, a spraying step for spraying the dispersion onto a heating furnace to obtain powdered metal oxide aggregate particles having pores, the pores An electrode forming slurry preparation step for preparing an electrode forming slurry containing powdered metal oxide aggregate particles having a shape, and the electrode forming slurry is formed into an electrode shape, then fired, and porous A method for producing an electrode for a porous solid oxide fuel cell, comprising an electrode forming step for obtaining an electrode for a solid oxide fuel cell.   Dispersion preparation step for preparing a dispersion containing a metal salt and a pore forming agent, spraying the dispersion on a heating furnace having a temperature lower than the temperature at which the pore forming agent burns, and forming a powdery pore forming agent-containing metal salt A spraying step for obtaining aggregate particles, an electrode forming slurry preparation step for preparing an electrode forming slurry containing the powdery pore forming agent-containing metal salt aggregate particles, and forming the electrode forming slurry into an electrode shape A method for producing an electrode for a porous solid oxide fuel cell, comprising the step of forming and then firing to obtain an electrode for a porous solid oxide fuel cell.   3. The production of a porous solid oxide fuel cell electrode according to claim 1, wherein the content of the pore-forming agent in the dispersion is 0.01 to 10% by mass. 4. Method.   The method for producing an electrode for a porous solid oxide fuel cell according to any one of claims 1 to 3, wherein an average diameter of the pore former is 0.01 to 1 µm.

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