JP4992206B2 - Method for producing electrode layer for solid oxide fuel cell - Google Patents

Description

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

  Solid oxide fuel cells (SOFCs) are currently being developed as third-generation power generation fuel cells, and three types are proposed: cylindrical, monolith, and flat plate stack. Each of them has a laminate in which a solid electrolyte (electrolyte layer) made of an oxide ion conductor is sandwiched between an air electrode layer (cathode) and a fuel electrode layer (anode). Usually, the single cell which consists of this laminated body is laminated | stacked alternately with a separator, and the fuel cell stack is comprised (for example, refer patent document 1).

In a solid oxide fuel cell, oxygen (air) is supplied to the air electrode layer side, and fuel gas (H ₂ , CO, CH _4, etc.) is supplied to the fuel electrode layer side. The air electrode layer and the fuel electrode layer are both porous layers so that the gas can reach the interface with the electrolyte layer. Oxygen supplied to the air electrode layer side passes through pores in the air electrode layer and reaches the vicinity of the interface with the electrolyte layer. At this portion, electrons are received from the air electrode layer and converted into oxide ions (O ²⁻ ). Ionized. The oxide ions move (diffuse) in the electrolyte layer toward the fuel electrode layer. The oxide ions that have reached the vicinity of the interface with the fuel electrode layer react with the fuel gas at this portion to become reaction products (H ₂ O, CO _2, etc.) and simultaneously release electrons. The electrons reach the air electrode layer after performing electrical work through an external electric circuit.

The electrode reaction that occurs on the air electrode layer side, that is, the ionization reaction from oxygen molecules to oxide ions (1 / 2O ₂ + 2e ⁻ → O ²⁻ ), involves the three components of oxygen molecules, electrons, and oxide ions. It occurs at a three-phase interface between an electrolyte layer that carries oxide ions, an air electrode layer that carries electrons, and a gas phase (air) that supplies oxygen molecules. Similarly, on the fuel electrode layer side, an electrode reaction occurs at the three-phase interface of the electrolyte layer, the fuel electrode layer, and the gas phase (fuel gas). Therefore, it is considered that increasing the three-phase interface is advantageous for smooth progress of the electrode reaction.

  The electrolyte layer is a moving medium for oxide ions and also functions as a partition wall for preventing the fuel gas and air from coming into direct contact with each other. Therefore, the electrolyte layer has a dense structure that is impermeable to gas. This electrolyte layer is composed of a material that has high oxide ion conductivity, is chemically stable under conditions from the oxidizing atmosphere on the air electrode layer side to the reducing atmosphere on the fuel electrode layer side, and is resistant to thermal shock. As materials satisfying these requirements, stabilized zirconia (hereinafter abbreviated as “YSZ”) added with yttria, scandia stabilized zirconia (hereinafter abbreviated as “ScSZ”), samaria doped ceria ( Hereinafter, a metal oxide film made of gadolinium-doped ceria (hereinafter abbreviated as “GDC”), lanthanum garade, or the like is generally used.

On the other hand, both the air electrode layer and the fuel electrode layer need to be made of a material having high electron conductivity. Since the material of the air electrode layer must be chemically stable in an oxidizing atmosphere at around 1000 ° C., metals are inappropriate. For example, perovskite type oxide materials having electron conductivity, specifically LaMnO ₃ or LaCoO ₃ or a solid solution in which a part of La in these materials is replaced with Sr, Ca or the like is generally used. Further, as a material for the fuel electrode layer, a metal such as Ni or a cermet such as Ni—YSZ is generally used. It should be noted that the metal such as Ni is normally in an oxide state such as NiO when the fuel electrode layer is formed, but is reduced to metal (Ni or the like) during operation of the fuel cell (during power generation).

  As this type of solid oxide fuel cell, for example, on a porous support substrate that also serves as one electrode layer (fuel electrode layer or air electrode layer), a thin-film electrolyte layer and the other electrode layer (fuel electrode layer or And an air electrode layer) are formed sequentially (see, for example, Patent Document 2).

As a method for forming the electrode layer, a paste is prepared by adding ceramic powder and a binder as an electrode material to a solvent, and this paste is applied on a substrate using a screen printing method or a doctor blade method, There is a method of firing these at a temperature of 1000 to 1500 ° C. In this method, a porous electrode layer can be formed by controlling the particle size and sintering conditions of the ceramic powder. Further, as a method of forming a porous fuel electrode substrate, for example, a method of adding several percent of a carbon material such as acetylene black to ceramic powder, mixing and pulverizing them in ethanol, and sintering at 1400 ° C. for 5 hours There is.
JP 2004-79332 A JP 2002-323362 A

  However, the above-described method requires a heat treatment step of 1000 ° C. or higher, and thus there is a problem in that the electrode layer is thermally contracted to cause breakage, warpage, peeling from the substrate, and the like.

  This invention is made | formed in view of such a situation, and provides the manufacturing method of the electrode layer for solid oxide fuel cells which can reduce a forming temperature.

A first manufacturing method of an electrode layer for a solid oxide fuel cell according to the present invention is for a solid oxide fuel cell having a porous base material and a metal oxide film formed on the porous base material. A method for producing an electrode layer, comprising:
The metal oxide film is formed by bringing a metal oxide film forming solution containing a metal source and an oxidizing agent or a reducing agent into contact with the heated porous substrate ,
The oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, sodium nitrite, potassium nitrite, sodium bromate, potassium bromate, silver oxide, dichromic acid and potassium permanganate. To do.

A second method for producing an electrode layer for a solid oxide fuel cell according to the present invention is for a solid oxide fuel cell having a porous substrate and a metal oxide film formed on the porous substrate. A method for producing an electrode layer, comprising:
The metal oxide film is formed by contacting a sol for forming a metal oxide film containing a metal source and an oxidizing agent or a reducing agent on the heated porous substrate ,
The oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, sodium nitrite, potassium nitrite, sodium bromate, potassium bromate, silver oxide, dichromic acid and potassium permanganate. To do.

  According to the method for producing an electrode layer for a solid oxide fuel cell of the present invention, a metal oxide film-forming solution containing a metal source or a metal oxide film-forming sol is brought into contact with a heated porous substrate. Thus, since the metal oxide film is formed, for example, a heat treatment step for joining particles constituting the electrode material layer becomes unnecessary, and the molding temperature can be reduced. Thereby, for example, deterioration of the cell due to thermal contraction of the obtained electrode layer for a solid oxide fuel cell can be prevented.

  In the method for producing an electrode layer for a solid oxide fuel cell of the present invention (hereinafter simply referred to as “electrode layer”), a metal oxide film-forming solution containing a metal source or a metal oxide film-forming sol is heated. A metal oxide film is formed by contacting on the porous substrate. Therefore, for example, a heat treatment step (usually 1000 ° C. or higher) for joining the particles constituting the electrode material layer becomes unnecessary, and the molding temperature can be reduced. Thereby, for example, deterioration of the cell due to thermal contraction of the obtained electrode layer can be prevented. Further, for example, the electrode layer can be manufactured with an inexpensive material. Furthermore, the manufacturing process can be simplified.

  Any metal source may be used as long as it contains the metal constituting the metal oxide film. For example, a metal salt, a metal complex in which an inorganic substance or an organic substance is coordinated with a metal ion, an organometallic compound having a metal-carbon bond in the molecule, or the like can be used. The said metal source may be used individually by 1 type, and may mix and use 2 or more types.

  The metal element constituting the metal source is not particularly limited as long as a metal oxide film having a desired metal composition can be obtained, but Mg, Al, Si, Ti, V, Mn, Fe, Co, It is preferably at least one metal element selected from Ni, Cu, Zn, Y, Zr, Ag, In, Sn, Ce, Sm, Pb, La, Hf, Sc, Gd, Ga and Ta. In the Pourbaille diagram, the metal element is a region present as a metal oxide (hereinafter referred to as “metal oxide region”) or a region present as a metal hydroxide (hereinafter referred to as “metal hydroxide region”). Therefore, it is suitable as a main constituent element of the metal oxide film. More preferably, Co, Ni, Pb, Zr, Y, Ce, Gd, and Sm, which are widely known as electrode materials, are suitable. The said metal source (1 type or multiple types) may contain 2 or more types of the said metal element.

  Examples of the metal salt include chlorides, nitrates, sulfates, perchlorates, acetates, phosphates, bromates and the like containing the above metal elements. Among these, in the present invention, it is preferable to use chloride, nitrate, and acetate. This is because these compounds are easily available as general-purpose products.

  Specific examples of the metal complex and the organometallic compound include magnesium diethoxide, aluminum acetylacetonate, calcium acetylacetonate dihydrate, calcium di (methoxyethoxide), and calcium gluconate monohydrate. , Calcium citrate tetrahydrate, calcium salicylate dihydrate, titanium lactate, titanium acetylacetonate, tetraisopropyl titanate, tetranormal butyl titanate, tetra (2-ethylhexyl) titanate, butyl titanate dimer, titanium bis (ethylhexoxy) Bis (2-ethyl-3-hydroxyhexoxide), diisopropoxytitanium bis (triethanolamate), dihydroxybis (ammonium lactate) titanium, diisopropoxytita Bis (ethylacetoacetate), Titanium peroxo ammonium citrate tetrahydrate, Dicyclopentadienyl iron (II), Iron (II) lactate trihydrate, Iron (III) acetylacetonate, Cobalt (II) Acetylacetonate, nickel (II) acetylacetonate dihydrate, copper (II) acetylacetonate, copper (II) dipivaloylmethanate, copper (II) ethylacetoacetate, zinc acetylacetonate, zinc lactate Hydrates, zinc salicylate trihydrate, zinc stearate, strontium dipivaloylmethanate, yttrium dipivaloylmethanate, zirconium tetra-n-butoxide, zirconium (IV) ethoxide, zirconium normal propyrate, zirconium Normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate , Zirconium acetylacetonate bisethylacetoacetate, zirconium acetate, zirconium monostearate, penta-n-butoxyniobium, pentaethoxyniobium, pentaisopropoxyniobium, tris (acetylacetonato) indium (III), 2-ethyl Indium hexanoate (III), tetraethyltin, dibutyltin oxide (IV), tricyclohexyltin (IV) hydroxide, lanthanum acetylacetonate dihydrate, tri (methoxyethoxy) lanthanum, pentaisopropoxytantalum, pentaethoxytantalum Tantalum (V) ethoxide, cerium (III) acetylacetonate, lead (II) citrate trihydrate, lead cyclohexanebutyrate and the like. Among these, magnesium diethoxide, aluminum acetylacetonate, calcium acetylacetonate dihydrate, titanium lactate, titanium acetylacetonate, tetraisopropyl titanate, tetranormal butyl titanate, tetra (2) are easily available and easy to handle. -Ethylhexyl) titanate, butyl titanate dimer, diisopropoxytitanium bis (ethyl acetoacetate), iron (II) lactate trihydrate, iron (III) acetylacetonate, zinc acetylacetonate, zinc lactate trihydrate, strontium Dipivaloylmethanate, pentaethoxyniobium, tris (acetylacetonato) indium (III), indium (III) 2-ethylhexanoate, tetraethyltin, dibutyltin oxide (IV), lanthanum acetylacetate Over preparative dihydrate, tri (methoxyethoxy) lanthanum, it is preferable to use a cerium (III) acetylacetonate.

  The solvent used in the metal oxide film forming solution is not particularly limited as long as it can dissolve the metal source described above. For example, lower alcohols having a total carbon number of 5 or less, such as methanol, ethanol, isopropanol, n-propanol, and butanol, water, toluene, a mixed solvent thereof and the like can be used. In the present invention, the above solvents may be used in combination. For example, a metal complex having low solubility in water but high solubility in an organic solvent and a material having low solubility in an organic solvent but high solubility in water (for example, a reducing agent described later) are used. In the case, a mixed solvent of water and an organic solvent is used to dissolve both of them, and a uniform metal oxide film forming solution can be obtained.

  The concentration of the metal source in the metal oxide film forming solution is usually 0.001 to 10 mol / liter, and preferably 0.01 to 1 mol / liter. If the concentration is less than 0.001 mol / liter, the metal oxide film formation reaction hardly occurs and the desired metal oxide film may not be obtained. If the concentration exceeds 10 mol / liter, precipitation occurs. This is because things may be generated.

  In the present invention, the metal oxide film forming solution may further contain at least one selected from an oxidizing agent and a reducing agent. This is because the deposition reaction of the metal oxide film can be promoted. For example, if the metal oxide film forming solution contains an oxidizing agent, the metal ions dissolved by the metal source are rapidly oxidized, which accelerates the metal oxide film formation reaction. To do. Further, for example, when a reducing agent is contained in the metal oxide film forming solution, it is considered that this reducing agent decomposes and emits electrons, thereby inducing an electrolysis reaction of water (solvent). When water electrolysis occurs, hydroxide ions are generated, which raises the pH of the metal oxide film forming solution and shifts to the metal oxide region or metal hydroxide region in the Pourbaix diagram. The film formation reaction of the metal oxide film is promoted.

  The oxidizing agent is not particularly limited as long as it can be dissolved in the above-described solvent and can oxidize a metal ion or the like formed by dissolving the metal source. For example, hydrogen peroxide, sodium nitrite, Examples thereof include potassium nitrite, sodium bromate, potassium bromate, silver oxide, dichromic acid, and potassium permanganate. Among them, hydrogen peroxide and potassium nitrite are preferably used.

  The concentration of the oxidizing agent in the metal oxide film forming solution varies depending on the type of the oxidizing agent, but is usually 0.001 to 1 mol / liter, particularly 0.01 to 0.1 mol / liter. Is preferred. If the concentration is less than 0.001 mol / liter, there is a possibility that the effect of promoting the film formation reaction of the metal oxide film may not be sufficiently exhibited. If the concentration exceeds 1 mol / liter, the concentration increases. This is because a suitable effect cannot be obtained and this is not preferable in terms of cost.

  The reducing agent is not particularly limited as long as it is soluble in the above-described solvent and can release electrons by a decomposition reaction. For example, borane-tert-butylamine complex, borane-N, N diethylaniline. Examples include complexes, borane complexes such as borane-dimethylamine complex and borane-trimethylamine complex, sodium cyanoborohydride, sodium borohydride, etc. Among them, it is preferable to use borane complex.

  The concentration of the reducing agent in the metal oxide film forming solution varies depending on the type of the reducing agent, but is usually 0.001 to 1 mol / liter, particularly 0.01 to 0.1 mol / liter. Is preferred. If the concentration is less than 0.001 mol / liter, there is a possibility that the effect of promoting the film formation reaction of the metal oxide film may not be sufficiently exhibited. If the concentration exceeds 1 mol / liter, the concentration increases. This is because a suitable effect cannot be obtained and this is not preferable in terms of cost.

  Further, the metal oxide film forming solution used in the present invention may contain additives such as an auxiliary ion source and a surfactant.

  The auxiliary ion source reacts with electrons to generate hydroxide ions, and can raise the pH of the metal oxide film forming solution and promote the film forming reaction of the metal oxide film. This is a function of guiding to a metal oxide region or a metal hydroxide region in the Pourbaix diagram. Therefore, the auxiliary ion source is effective when combined with a reducing agent that decomposes by heat and emits electrons. Even if the reducing agent is not contained in the metal oxide film forming solution, oxygen is generated by heating. Can be used alone as an oxidizing agent. In addition, what is necessary is just to set the usage-amount of the said auxiliary ion source suitably according to the metal source etc. to be used.

Specific examples of such auxiliary ion sources include chlorate ions, perchlorate ions, chlorite ions, hypochlorite ions, bromate ions, hypobromate ions, nitrate ions, nitrite ions, etc. Can be mentioned. These auxiliary ion sources are believed to cause the following reactions in solution.
(Formula ^{_{1) ClO 4 - + H 2}} O + 2e - ⇔ ClO 3 - + 2OH -
(Formula ^{_{2) ClO 3 - + H 2}} O + 2e - ⇔ ClO 2 - + 2OH -
(Chemical Formula 3) ClO ₂ ⁻ + H ₂ O + 2e ⁻ ⇔ ClO ⁻ + 2OH ⁻
(Formula _{^{4) 2ClO - + 2H 2 O}} + 2e - ⇔ Cl 2 + 4OH -
(Formula ^{_{5) BrO 3 - + 2H 2}} O + 4e - ⇔ BrO - + 4OH -
Embedded image 2BrO ⁻ + 2H ₂ O + 2e ⁻ ＯBr ₂ + 4OH ⁻
(Chemical Formula 7) NO ₃ ⁻ + H ₂ O + 2e ⁻ ⇔ NO ₂ ⁻ + 2OH ⁻
(Chemical Formula 8) NO ₂ ⁻ + 3H ₂ O + 3e ⁻ ＮＨ NH ₃ + 3OH ⁻

  The surfactant can improve the wettability of the metal oxide film forming solution with respect to the surface of the porous substrate and promote the film formation reaction of the metal oxide film. Specific examples of such surfactants include Surfinol 485, Surfinol SE, Surfinol SE-F, Surfinol 504, Surfinol GA, Surfinol 104A, Surfinol 104BC, Surfinol 104PPM, Surfinol 104E. Surfynol series such as Surfinol 104PA (all are trade names manufactured by Nissin Chemical Industry Co., Ltd.), NIKKOL AM301, NIKKOL AM313ON (all are trade names manufactured by Nikko Chemical Co., Ltd.), and the like. In addition, what is necessary is just to set the usage-amount of the said surfactant suitably according to the metal source etc. to be used.

  As a solvent for the metal oxide film forming sol, a solvent capable of hydrolyzing a metal source is preferable. For example, a solvent containing an alcohol such as ethanol is preferable. Other conditions (for example, additives) of the metal oxide film forming sol are the same as those of the metal oxide film forming solution. In addition, as a metal source hydrolyzed, the metal alkoxide containing the metal which comprises the said metal oxide film is preferable.

  Examples of the material for the porous substrate used in the present invention include ceramics and metals. In particular, a metal is preferable because of its current collecting effect. The metal that can be used may be an alloy such as stainless steel or iron-nickel, or a pure metal such as nickel, iron, gold, or platinum. Examples of ceramics that can be used include alumina and silica. The average diameter of the pores in the porous substrate is usually about 1 μm to 1 mm. The porosity of the porous substrate is usually 20 to 50% by volume, and preferably 30 to 40% by volume in order to improve the gas permeability of the obtained electrode layer. In addition, it does not specifically limit about the manufacturing method of the said porous base material, For example, well-known methods, such as the method proposed by Unexamined-Japanese-Patent No. 2003-346843, can be used.

  When the fuel electrode layer is formed as the electrode layer, for example, a metal source including a metal constituting an oxide ion conductor such as a ceramic powder material and a metal constituting a metal catalyst can be used as the metal source. . Examples of the oxide ion conductor include those having a fluorite-type or perovskite-type crystal structure. Examples of those having a fluorite-type crystal structure include ceria-based oxides doped with samarium and gadolinium, zirconia-based oxides containing scandium and yttrium, and the like. In addition, examples of those having a perovskite-type crystal structure include lanthanum galide oxides doped with strontium and magnesium. As a metal constituting the metal catalyst, a material that is stable in a reducing atmosphere and has a hydrogen oxidation activity can be used. For example, nickel, iron, cobalt, or the like, or a noble metal (platinum, ruthenium, palladium, or the like) ) Etc. can be used. Among the above metals, nickel having high hydrogen oxidation activity is preferable. The porosity of the fuel electrode layer is usually 20 to 50% by volume, and preferably 30 to 40% by volume. The thickness of the fuel electrode layer is usually 5 to 50 μm.

When an air electrode layer is formed as the electrode layer, for example, a metal source containing a metal constituting a metal oxide having a perovskite crystal structure can be used. Specific examples of the metal oxide include (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Examples thereof include metal oxides such as Sr) (Fe, Co, Ni) O _3, and (La, Sr) MnO ₃ is preferable from the viewpoint of stability in an oxidizing atmosphere. Moreover, what contains noble metals, such as platinum, ruthenium, palladium, can also be used as said metal source for forming an air electrode layer. In addition, the porosity of an air electrode layer is 20-50 volume% normally, Preferably it is 30-40 volume%. The thickness of the air electrode layer is usually 5 to 50 μm.

  Next, a method for contacting the metal oxide film forming solution or the metal oxide film forming sol (hereinafter referred to as “metal oxide film forming liquid”) on the porous substrate in the present invention will be described. The contact method in the present invention is not particularly limited, but is preferably a method that does not lower the temperature of the porous substrate when the metal oxide film-forming liquid and the porous substrate come into contact with each other. . This is because when the temperature of the porous base material is lowered, the film formation reaction is difficult to occur, and a desired metal oxide film may not be obtained. Examples of a method that does not lower the temperature of the porous substrate include a method of bringing the metal oxide film forming liquid into contact with the porous substrate as droplets. At this time, the droplet preferably has a small diameter of, for example, about 0.1 to 1000 μm. If the diameter of the droplet is within the above range, the solvent of the metal oxide film forming liquid can be instantly evaporated to prevent the temperature of the porous substrate from being lowered, and the droplet diameter is small. This is because a uniform metal oxide film can be obtained.

  The method of bringing the metal oxide film-forming liquid droplets into contact with the porous substrate is not particularly limited. Specifically, the porous substrate is sprayed with the metal oxide film-forming liquid. A method of bringing the metal oxide film forming liquid into contact therewith, or passing the porous base material through a space in which the metal oxide film forming liquid is made into a mist, so that the metal oxide film is formed on the porous base material. The method etc. which make a forming liquid contact are mentioned. In addition, the method of contacting the metal oxide film forming liquid onto the porous substrate in the present invention may be a method other than the method of bringing the metal oxide film forming liquid into contact with the porous substrate as droplets. . For example, the porous substrate surface may be brought into direct contact with the liquid surface of the metal oxide film forming liquid.

  Examples of the method of spraying the metal oxide film forming liquid onto the porous substrate include a method of spraying using a spray device or the like. When spraying using the said spray apparatus etc., the diameter of a droplet is 0.1-1000 micrometers normally, and it is preferable that it is 0.5-300 micrometers especially. This is because, if the diameter of the droplet is within the above range, a decrease in the temperature of the porous substrate can be suppressed, and a uniform metal oxide film can be obtained.

  The spray gas of the spray device is not particularly limited as long as it does not inhibit the formation of the metal oxide film, and examples thereof include air, nitrogen, argon, helium, oxygen and the like. Active gases such as nitrogen, argon and helium are preferred. Further, the injection amount of the metal oxide film forming liquid is usually 0.001 to 1 liter / min. In order to obtain a more uniform metal oxide film, 0.001 to 0.05 liter / min. Preferably there is. At this time, the thickness of the formed metal oxide film can be arbitrarily adjusted by spraying repeatedly. In the metal oxide film formed according to the present invention, the thickness of the region existing on the porous substrate is preferably 10 nm or more. This is because a uniform metal oxide film can be obtained when the thickness is 10 nm or more. The spray device may be a fixed device, a movable device, a device that ejects the solution by rotation, a device that ejects the solution by pressure, or the like. As such a spray device, a commonly used spray device can be used, and for example, hand spray (manufactured by ASONE) or the like can be used.

  In the present invention, for example, when the metal oxide film is formed by using the above-described method of spraying the metal oxide film forming liquid onto the porous substrate, the resulting metal oxide film has a columnar shape in which crystals are grown in the stacking direction. Includes a collection of crystals having a structure. In such a metal oxide film, the conductivity of electrons and ions is improved and the resistance is lowered. In order to exert the above-mentioned effect reliably, a value obtained by dividing the crystal length in the stacking direction of the metal oxide film in the crystal by the crystal diameter in a direction perpendicular to the stacking direction of the metal oxide film in the crystal. However, it is preferable to select a material and a solvent so that it becomes 2 or more.

  The metal oxide film formed in the present invention includes not only the outer surface of the porous substrate but also at least the wall surface (hereinafter also referred to as “inner surface”) that forms pores in the porous substrate. A part may be covered. For example, in the surface layer of the porous substrate in the vicinity of the interface between the porous substrate and the metal oxide film, a part of the metal oxide film covers at least a part of the inner surface. Since the adhesion between the metal oxide film and the porous substrate is improved, it is preferable. In addition, when a part of the metal oxide film covers at least a part of the inner surface, the electrode reaction field is increased, so that the smoothness of the electrode reaction can be promoted. In order to exhibit the effect more reliably, at least 10 nm (more preferably at least 100 nm, particularly preferably) in the depth direction of the porous substrate from the interface between the porous substrate and the metal oxide film. The spraying conditions and the like may be adjusted so that a part of the metal oxide film covers at least a part of the inner surface in the pores existing in a range of at least 1 μm).

  When using a method in which a porous substrate is passed through a space in which the metal oxide film forming liquid is made into a mist, the diameter of the droplets is usually 0.01 to 300 μm, and in particular, 1 to 100 μm. preferable. This is because, if the diameter of the droplet is within the above range, a decrease in the temperature of the porous substrate can be suppressed, and a uniform metal oxide film can be obtained. At this time, the thickness of the formed metal oxide film can be arbitrarily adjusted by allowing the porous substrate to pass through or repeatedly passing, for example, controlling the thickness of the obtained metal oxide film within the above-described range. can do.

  In the present invention, in order to promote the film formation reaction of the metal oxide film, the porous substrate is heated when the metal oxide film forming liquid is brought into contact with the porous substrate. For example, what is necessary is just to heat the said porous base material more than metal oxide film formation temperature. Here, the “metal oxide film forming temperature” is the lowest temperature at which the metal element constituting the metal source is combined with oxygen to form a metal oxide film on the porous substrate. . The metal oxide film forming temperature varies greatly depending on the type of metal source and the composition of the metal oxide film forming liquid such as a solvent, and is usually in the range of 150 to 800 ° C. In particular, from the viewpoint of productivity, it is preferable to select the type of metal source, the solvent, and the like so that the temperature is within a range of 400 to 550 ° C. On the other hand, when the metal oxide film forming liquid contains an oxidizing agent or a reducing agent, the metal oxide film forming temperature is usually in the range of 25 to 800 ° C., particularly from the viewpoint of productivity, 70 to It is preferable to select the type of metal source, the solvent, and the like so that the temperature is within the range of 400 ° C.

  The metal oxide film formation temperature can be measured by the following method. First, a metal oxide film forming liquid containing a desired metal source is prepared. Next, the metal oxide film is formed by contacting the metal oxide film forming liquid on the porous substrate while changing the surface temperature of the porous substrate by heating the porous substrate. Among the surface temperatures of the porous substrate that can be measured, the lowest surface temperature is measured. This minimum surface temperature can be referred to as a “metal oxide film forming temperature” in the present specification. At this time, whether or not the metal oxide film is formed is determined from the result obtained by, for example, an X-ray diffraction apparatus (Rigaku, RINT-1500) when the obtained metal oxide film has crystallinity, When the obtained metal oxide film is an amorphous film, it can be determined from, for example, a result obtained by a photoelectron spectroscopic analyzer (manufactured by V. G. Scientific, ESCALAB 200i-XL).

  Further, the heating method of the porous substrate is not particularly limited, and examples thereof include a heating method using a hot plate, oven, firing furnace, infrared lamp, hot air blower, etc. Is preferable because the temperature of the porous substrate can be reliably maintained at a desired temperature.

  In the present invention, the metal oxide film forming liquid may be brought into contact with the porous substrate in an oxidizing gas atmosphere. This is because oxidation of metal ions or the like formed by dissolving the metal source is rapidly performed, so that the film formation reaction of the metal oxide film is promoted. Such an oxidizing gas is not particularly limited as long as it can oxidize metal ions and the like obtained by dissolving the metal source. For example, oxygen, ozone, nitrous acid gas, nitrogen dioxide, chlorine dioxide In particular, oxygen and ozone are preferably used, and ozone is particularly preferably used. This is because it is easy to obtain industrially and can realize cost reduction.

  Moreover, in this invention, when making a metal oxide film formation liquid contact on a porous base material, you may irradiate an ultraviolet-ray to the location where a porous base material and a metal oxide film formation liquid contact. By irradiating with ultraviolet rays, it is considered that the electrolysis reaction of water can be promoted or the decomposition of the reducing agent described above can be promoted. This is because the film formation reaction of the film can be promoted. Further, by irradiating with ultraviolet rays, hydroxide ions can be generated from the auxiliary ion source described above, and the crystallinity of the obtained metal oxide film can be improved. The ultraviolet light includes near ultraviolet light having a wavelength of 470 nm or less.

The wavelength of the ultraviolet light is usually 185 to 470 nm, and preferably 185 to 260 nm in order to further promote the film forming reaction. The intensity of the ultraviolet light is usually 1 to 20 mW / cm ² , and preferably 5 to 15 mW / cm ² in order to further promote the film forming reaction. As an ultraviolet irradiation apparatus for performing such ultraviolet irradiation, for example, a commercially available ultraviolet irradiation apparatus can be used, and specifically, HB400X-21 manufactured by SEN Special Light Source Co., Ltd. can be used. In the present invention, ultraviolet rays may be irradiated to the place where the porous substrate and the metal oxide film forming liquid are in contact with each other in the above-described oxidizing gas atmosphere.

  In the present invention, the obtained metal oxide film may be washed and dried. The cleaning of the metal oxide film is performed to remove impurities present on the surface of the metal oxide film. Examples of the cleaning method include a method of cleaning using a solvent used in the metal oxide film forming liquid. In addition, when the metal oxide film is dried, it may be dried by leaving it at room temperature, or may be dried in a heating apparatus such as an oven.

  When producing a solid oxide fuel cell using the electrode layer obtained by the present invention, for example, first, a paste containing an electrolyte material is screen-printed or doctor-bladed on the electrode layer. An electrolyte layer is formed by applying the powder by a coating method such as the above, and sintering them. Next, on the electrolyte layer, for example, a paste containing a material of an electrode layer different from the electrode layer is applied by a coating method such as a screen printing method or a doctor blade method, and these are sintered. Thus, an electrode layer (fuel electrode layer or air electrode layer) different from the above electrode layer may be formed.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings as appropriate. 1A and 1B to be referred to are schematic process diagrams showing a method for manufacturing an electrode layer according to an embodiment of the present invention.

  First, a metal source is dissolved in a solvent such as water to prepare a metal oxide film forming solution 1. Then, as shown in FIG. 1A, the metal oxide film forming solution is sprayed by the spray device 2 in a state where the porous substrate 11 is heated to the metal oxide film forming temperature or higher by, for example, a hot plate (not shown). 1 is sprayed onto the porous substrate 11. As a result, as shown in FIG. 1B, a metal oxide film 12 in contact with the porous substrate 11 is formed, and an air electrode layer 13 composed of the porous substrate 11 and the metal oxide film 12 can be obtained. it can. At this time, the inner surface 11 a of the surface layer of the porous substrate 11 located in the vicinity of the interface between the porous substrate 11 and the metal oxide film 12 is covered with a part of the metal oxide film 12. In the present embodiment, the air electrode layer 13 composed of the porous substrate 11 and the metal oxide film 12 is formed. However, the present invention is not limited to this, and a fuel electrode layer may be formed. In this embodiment, the metal oxide film forming solution is used, but a metal oxide film forming sol may be used instead of the metal oxide film forming solution.

  Next, an example of a method for producing a solid oxide fuel cell using the electrode layer obtained by the present invention will be described with reference to the drawings as appropriate. 2A and 2B to be referred to are schematic process diagrams showing an example of a method for producing a solid oxide fuel cell using the electrode layer (air electrode layer 13) obtained by the present invention.

  First, as shown in FIG. 2A, an electrolyte layer 14 is formed on the metal oxide film 12 of the air electrode layer 13 by using a screen printing method or the like. Next, as shown in FIG. 2B, the fuel electrode layer 15 is formed on the electrolyte layer 14 by means of a screen printing method or the like, and the solid oxide fuel cell (single cell) 10 is obtained.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

Example 1
Alumina powder (particle size range: 0.01 to 10 μm, average particle size: 1 μm) and acetylene black powder were added to ethanol and mixed while being pulverized in ethanol. Next, these were dried at a temperature of 100 ° C. for 15 minutes, pressed and hardened with an isostatic press, and then sintered at 1400 ° C. for 5 hours to prepare a porous substrate (thickness: 800 μm).

  Next, cobalt chloride (manufactured by Kanto Chemical Co., Inc.), samarium nitrate (manufactured by Kanto Chemical Co., Ltd.) and strontium chloride (manufactured by Kanto Chemical Co., Ltd.) were added at concentrations of 0.1 mol / liter, 0.05 mol / liter and 0.05 mol, respectively. A solution for forming a metal oxide film was prepared by dissolving in ethanol so as to be 1 / liter. Then, in the state where the porous substrate is heated to 400 ° C., the metal oxide forming solution (300 ml) is sprayed by hand spray (manufactured by ASONE Co., Ltd.), and the metal oxide is brought into contact with the porous substrate. A material film (thickness on the porous substrate: 3 μm) was formed to obtain an air electrode layer composed of the porous substrate and the metal oxide film.

Subsequently, GDC (Ce: Gd: O = 0.9: 0.1: 1.9) powder (particle size range: 0.05 to 5 μm, average particle size: 0.5 μm) and cellulose binder resin, A paste was prepared by adding to diethylene glycol monobutyl ether acetate so that the mass ratio (GDC: cellulose-based binder resin) was 95: 5. The viscosity of the paste at this time was 5 × 10 ⁵ mPa · s. The paste is applied on the air electrode layer by screen printing, dried at 130 ° C. for 5 minutes, sintered at 1200 ° C. for 1 hour, and an electrolyte layer (thickness) made of GDC on the air electrode layer. : 50 μm).

  Subsequently, NiO powder (particle size range: 0.01 to 10 μm, average particle size: 1 μm) and SDC (Ce: Sm: O = 0.8: 0.2: 1.9) powder (particle size range: 1 10 μm, average particle diameter: 0.1 μm) after mixing so that the mass ratio (NiO: SDC) is 70:30, together with the cellulose binder resin, the mass ratio (mixture of NiO and SDC: binder resin) Was added to diethylene glycol monobutyl ether acetate so as to be 80:20 to prepare a paste. And after applying this paste on the said electrolyte layer by screen printing, these are sintered at 1200 degreeC for 5 hours, a fuel electrode layer (thickness: 30 micrometers) is formed, and a solid oxide fuel cell is formed. A single cell was obtained.

(Example 2)
Iron-nickel powder (particle size range: 0.01 to 10 μm, average particle size: 1 μm) and acetylene black powder were added to ethanol and mixed while being pulverized in ethanol. Next, these were dried at a temperature of 100 ° C. for 15 minutes, pressed and hardened with an isostatic press, and then sintered at 1400 ° C. for 5 hours to prepare a porous substrate (thickness: 800 μm).

  Next, nickel nitrate (manufactured by Kanto Chemical Co., Inc.), cerium acetate (manufactured by Kanto Chemical Co., Ltd.) and samarium nitrate (manufactured by Kanto Chemical Co., Ltd.) were added at concentrations of 0.1 mol / liter, 0.1 mol / liter and 0.04 mol, respectively. A solution for forming a metal oxide film was prepared by dissolving in a mixed solvent consisting of water and ethanol so as to be 1 / liter. The mixed solvent used had a volume ratio (water: ethanol) of 40:60. Then, in the state where the porous substrate is heated to 400 ° C., the metal oxide forming solution (150 ml) is sprayed by hand spray (manufactured by ASONE Co., Ltd.), and the metal oxidation contacting the porous substrate is performed. A material film (thickness on the porous substrate: 1 μm) was formed to obtain a fuel electrode layer composed of the porous substrate and the metal oxide film.

Subsequently, GDC (Ce: Gd: O = 0.9: 0.1: 1.9) powder (particle size range: 0.05 to 5 μm, average particle size: 0.5 μm) and cellulose binder resin, A paste was prepared by adding to diethylene glycol monobutyl ether acetate so that the mass ratio (GDC: cellulose-based binder resin) was 95: 5. The viscosity of the paste at this time was 5 × 10 ⁵ mPa · s. The paste is applied onto the fuel electrode layer by a screen printing method, dried at 130 ° C. for 5 minutes, sintered at 1200 ° C. for 1 hour, and an electrolyte layer (thickness) made of GDC on the fuel electrode layer. : 50 μm).

Next, (Sm, Sr) CoO ₃ (Sm: Sr: Co: O = 0.5: 0.5: 1: 3) powder (particle size range: 0.1 to 10 μm, average particle size: 3 μm) and A paste was prepared by adding a cellulose binder resin to diethylene glycol monobutyl ether acetate so that the mass ratio ((Sm, Sr) CoO ₃ : binder resin) was 80:20. And after applying this paste on the said electrolyte layer by screen printing, these are sintered at 1200 degreeC for 5 hours, an air electrode layer (thickness: 30 micrometers) is formed, and a solid oxide fuel cell is formed. A single cell was obtained.

(Example 3)
On the porous substrate formed by the same method as in Example 2, a metal oxide film (thickness on the porous substrate: 2 μm) is formed by the same method as in Example 1, and the above porous substrate An air electrode layer composed of the material and the metal oxide film was obtained.

  Subsequently, cerium (III) nitrate (manufactured by Kanto Chemical Co., Inc.), gadolinium nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) and borane-dimethylamine complex (manufactured by Kanto Chemical Co., Ltd.) as a reducing agent were each added at a concentration of 0.03 mol / A metal oxide film-forming solution was prepared by dissolving in a mixed solvent consisting of ethanol and water so as to be 1 liter, 0.0045 mol / liter, and 0.05 mol / liter. The mixed solvent used had a volume ratio (ethanol: water) of 50:50. Then, the air electrode layer is immersed in the metal oxide film forming solution (70 ° C.) for 24 hours, and an electrolyte layer (thickness on the air electrode layer: 0.6 μm) is formed on the air electrode layer. Formed.

  And on the said electrolyte layer, the fuel electrode layer (thickness: 30 micrometers) was formed by the method similar to Example 1, and the single cell of the solid oxide fuel cell was obtained.

Example 4
On the porous substrate formed by the same method as in Example 2, a metal oxide film (thickness on the porous substrate: 2 μm) is formed by the same method as in Example 1, and the above porous substrate An air electrode layer composed of the material and the metal oxide film was obtained.

  Next, zirconium tetraacetylacetonate (manufactured by Kanto Chemical Co., Inc.) and yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.) are added to toluene: ethanol so that the respective concentrations are 0.1 mol / liter and 0.008 mol / liter. A solution for forming a metal oxide film was prepared by dissolving in a mixed solvent of = 85: 15. Then, the metal oxide film forming solution (100 ml) is sprayed onto the air electrode layer heated to 450 ° C. by hand spray (manufactured by ASONE), and an electrolyte layer made of YSZ (on the air electrode layer) A thickness on the air electrode layer: 10 μm) was formed. The injection amount at this time was 0.001 liter / min.

  And on the said electrolyte layer, the fuel electrode layer (thickness: 30 micrometers) was formed by the method similar to Example 1, and the single cell of the solid oxide fuel cell was obtained.

(Example 5)
On the porous substrate formed by the same method as in Example 2, a metal oxide film (thickness on the porous substrate: 2 μm) is formed by the same method as in Example 1, and the above porous substrate An air electrode layer composed of the material and the metal oxide film was obtained.

  Subsequently, zirconium chloride oxide octahydrate (manufactured by Kanto Chemical Co., Inc.), yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.) and borane-dimethylamine complex (manufactured by Kanto Chemical Co., Ltd.) as a reducing agent, each having a concentration of 0.02 mol. First metal oxide film-forming solution was prepared by dissolving in a mixed solvent consisting of ethanol and water so that it would be / liter, 0.002 mol / liter, and 0.04 mol / liter. The mixed solvent used had a volume ratio (ethanol: water) of 50:50. Then, the air electrode layer is immersed in the first metal oxide film forming solution (60 ° C.) for 12 hours, and the first metal oxide film (thickness on the air electrode layer is formed on the air electrode layer). : 0.1 μm).

  Next, zirconium tetraacetylacetonate (manufactured by Kanto Chemical Co., Inc.) and yttrium acetate (manufactured by Kanto Chemical Co., Ltd.) are made of toluene and ethanol so that the respective concentrations are 0.1 mol / liter and 0.008 mol / liter. A second metal oxide film forming solution was prepared by dissolving in a mixed solvent. The mixed solvent used had a volume ratio (toluene: ethanol) of 85:15. Then, the second metal oxide film-forming solution (200 ml) is sprayed on the first metal oxide film heated to 400 ° C. by hand spray (manufactured by ASONE), and the first metal oxide film A second metal oxide film (thickness: 10 μm) was formed thereon. Thus, an electrolyte layer composed of the first metal oxide film and the second metal oxide film was obtained.

  And on the said electrolyte layer, the fuel electrode layer (thickness: 30 micrometers) was formed by the method similar to Example 1, and the single cell of the solid oxide fuel cell was obtained.

(Example 6)
Since Example 6 differs from Example 1 described above only in the formation method of the air electrode layer, only the formation method of the air electrode layer will be described.

  Alumina powder (particle size range: 0.01 to 10 μm, average particle size: 1 μm) and acetylene black powder were added to ethanol and mixed while being pulverized in ethanol. Next, these were dried at a temperature of 100 ° C. for 15 minutes, pressed and hardened with an isostatic press, and then sintered at 1400 ° C. for 5 hours to prepare a porous substrate (thickness: 800 μm).

  Next, cobalt (III) acetylacetonate (manufactured by Kanto Chemical Co., Inc.), samarium nitrate (manufactured by Kanto Chemical Co., Ltd.) and strontium chloride (manufactured by Kanto Chemical Co., Ltd.) were added at concentrations of 0.1 mol / liter and 0.05 mol / liter, respectively. A sol for forming a metal oxide film was prepared by dissolving in a mixed solvent consisting of toluene, ethanol and water so as to be 1 liter and 0.05 mol / liter. The mixed solvent used had a volume ratio (toluene: ethanol: water) of 70: 25: 5. Then, with the porous substrate heated to 450 ° C., the metal oxide-forming sol (200 ml) is sprayed with a hand spray (manufactured by AS ONE), and the metal oxide is brought into contact with the porous substrate. A material film (thickness on the porous substrate: 2 μm) was formed to obtain an air electrode layer composed of the porous substrate and the metal oxide film.

A and B are schematic process diagrams showing a method for manufacturing an electrode layer according to an embodiment of the present invention. A and B are schematic process diagrams showing an example of a method for producing a solid oxide fuel cell using the electrode layer obtained according to the present invention.

Explanation of symbols

1 Solution for forming metal oxide film 2 Spray device 10 Solid oxide fuel cell (single cell)
DESCRIPTION OF SYMBOLS 11 Porous base material 11a Inner surface 12 Metal oxide film 13 Air electrode layer 14 Electrolyte layer 15 Fuel electrode layer

Claims (17)

A method for producing an electrode layer for a solid oxide fuel cell comprising a porous substrate and a metal oxide film formed on the porous substrate,
The metal oxide film is formed by bringing a metal oxide film forming solution containing a metal source and an oxidizing agent or a reducing agent into contact with the heated porous substrate ,
The oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, sodium nitrite, potassium nitrite, sodium bromate, potassium bromate, silver oxide, dichromic acid and potassium permanganate. A method for producing an electrode layer for a solid oxide fuel cell.   When the metal oxide film forming solution is brought into contact with the porous substrate, the metal element constituting the metal source is combined with oxygen to form the metal oxide film on the porous substrate. The manufacturing method of the electrode layer for solid oxide fuel cells of Claim 1 which heats the said porous base material more than minimum temperature.   The metal oxide film is formed by spraying the metal oxide film forming solution onto the porous substrate to bring the metal oxide film forming solution into contact with the porous substrate. A method for producing an electrode layer for a solid oxide fuel cell according to claim 1 or 2. The method for producing an electrode layer for a solid oxide fuel cell according to any one of claims 1 to 3, wherein the metal oxide film forming solution contains a metal source and a reducing agent .   The metal oxide film forming solution is at least one selected from chlorate ions, perchlorate ions, chlorite ions, hypochlorite ions, bromate ions, hypobromate ions, nitrate ions and nitrite ions. The method for producing an electrode layer for a solid oxide fuel cell according to any one of claims 1 to 4, further comprising one ionic species. A method for producing an electrode layer for a solid oxide fuel cell comprising a porous substrate and a metal oxide film formed on the porous substrate,
The metal oxide film is formed by contacting a sol for forming a metal oxide film containing a metal source and an oxidizing agent or a reducing agent on the heated porous substrate ,
The oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, sodium nitrite, potassium nitrite, sodium bromate, potassium bromate, silver oxide, dichromic acid and potassium permanganate. A method for producing an electrode layer for a solid oxide fuel cell.   When the metal oxide film-forming sol is brought into contact with the porous substrate, the metal element constituting the metal source is combined with oxygen to form the metal oxide film on the porous substrate. The manufacturing method of the electrode layer for solid oxide fuel cells of Claim 6 which heats the said porous base material more than minimum temperature.   The metal oxide film is formed by spraying the metal oxide film-forming sol onto the porous substrate to bring the metal oxide film-forming sol into contact with the porous substrate. A method for producing an electrode layer for a solid oxide fuel cell according to claim 6 or 7. The method for producing an electrode layer for a solid oxide fuel cell according to any one of claims 6 to 8, wherein the sol for forming a metal oxide film includes a metal source and a reducing agent .   The sol for forming a metal oxide film is at least one selected from chlorate ion, perchlorate ion, chlorite ion, hypochlorite ion, bromate ion, hypobromate ion, nitrate ion and nitrite ion. The method for producing an electrode layer for a solid oxide fuel cell according to any one of claims 6 to 9, further comprising one ionic species. The said metal source is at least one chosen from a metal salt, a metal complex, and an organometallic compound, The manufacture of the electrode layer for solid oxide fuel cells of any one of Claim 1, 2, 6, 7 Method.   The metal source is Mg, Al, Si, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Ag, In, Sn, Ce, Sm, Pb, La, Hf, Sc, Gd. The method for producing an electrode layer for a solid oxide fuel cell according to any one of claims 1, 2, 6, 7, and 11, comprising at least one metal element selected from Ga, Ta, and Ga. The electrode layer for the solid oxide fuel cell is a fuel electrode layer,
The solid oxide form according to claim 1, wherein the metal oxide film includes an oxide ion conductor having a fluorite-type or perovskite-type crystal structure and a metal catalyst. A method for producing an electrode layer for a fuel cell. The electrode layer for the solid oxide fuel cell is an air electrode layer,
9. The solid oxide fuel cell according to claim 1, wherein the metal oxide film includes at least one selected from a metal oxide having a perovskite crystal structure and a noble metal. Method for manufacturing an electrode layer.   The method for producing an electrode layer for a solid oxide fuel cell according to any one of claims 1 to 3 and 6 to 8, wherein the porous substrate is made of ceramics or metal.   The electrode for a solid oxide fuel cell according to any one of claims 1 to 3 and 6 to 8, wherein a thickness of a region existing on the porous substrate in the metal oxide film is 10 nm or more. Layer manufacturing method.   The part of the metal oxide film covers at least a part of a wall surface that forms pores in the porous substrate, according to any one of claims 1 to 3, 6 to 8, and 16. A method for producing an electrode layer for a solid oxide fuel cell.

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