JP4918995B2 - Method for producing solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell having an electrolyte layer and a pair of porous electrode layers sandwiching the electrolyte layer, and a method for manufacturing the same.

  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 the 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 passes through the pores in the air electrode layer and reaches the vicinity of the interface with the electrolyte layer, and receives electrons from the air electrode layer at this portion to form oxide ions (O ²⁻ ). Ionized. The oxide ions move (diffuse) in the electrolyte layer toward the fuel electrode layer. The oxide ions that reach 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 a material that satisfies this requirement, a metal oxide film made of stabilized zirconia (hereinafter abbreviated as “YSZ”) to which yttria is added 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 substituted 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, an electrolyte layer and the other electrode layer (fuel electrode layer or air electrode layer) are formed on a porous substrate that also serves as one electrode layer (fuel electrode layer or air electrode layer). Are sequentially formed, and these are sandwiched by plate-like current collectors (see, for example, Patent Document 2).
JP 2004-79332 A JP 2005-251490 A

  However, in the conventional solid oxide fuel cell, since the contact surface between the current collector and the electrode layer is limited, it is difficult to improve the current collecting performance.

  This invention is made | formed in view of such a situation, and provides the solid oxide fuel cell which can improve current collection performance, and its manufacturing method.

The solid oxide fuel cell of the present invention is a solid oxide fuel cell having an electrolyte layer and a pair of porous electrode layers sandwiching the electrolyte layer,
A current collecting material adheres along at least a part of the pore wall surface to at least one of the pair of porous electrode layers.

The method for producing a solid oxide fuel cell of the present invention is a method for producing a solid oxide fuel cell having an electrolyte layer and a pair of porous electrode layers sandwiching the electrolyte layer,
After forming at least one of the pair of porous electrode layers, the porous wall surface of the porous electrode layer is immersed in a solution containing a metal source having a metal as a current collecting material. A metal oxide is deposited along at least a part of the substrate.

  According to the solid oxide fuel cell and the method of manufacturing the same of the present invention, the current collecting material and the porous electrode layer are adhered by attaching the current collecting material along at least a part of the pore wall surface of the porous electrode layer. The contact surface can be increased. Thereby, current collection performance can be improved.

  The solid oxide fuel cell of the present invention has an electrolyte layer and a pair of porous electrode layers sandwiching the electrolyte layer, and at least one of the pair of porous electrode layers includes at least a pore wall surface thereof. A current collecting material adheres along a part. Thereby, since the contact surface of a current collection material and a porous electrode layer can be increased, current collection performance can be improved.

  As the pair of porous electrode layers, a fuel electrode layer and an air electrode layer can be used. In this case, the current collecting material adheres along at least a part of the pore wall surface of at least one of the fuel electrode layer and the air electrode layer.

  As the material for the fuel electrode layer, for example, a mixture of an oxide ion conductor such as a ceramic powder material and a metal catalyst can be used. As the oxide ion conductor, one having a fluorite-type or perovskite-type crystal structure can be preferably used. 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. Further, examples of those having a perovskite 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 materials, nickel having high hydrogen oxidation activity is preferable. Therefore, it is preferable to form the fuel electrode layer with a mixture of the oxide ion conductor and nickel. Note that the mixture of the ceramic powder material made of an oxide ion conductor and nickel may be a mixture of both of them, or a modification of the ceramic powder to nickel. Moreover, the ceramic powder material mentioned above may be used individually by 1 type, and may mix and use 2 or more types. Further, the fuel electrode layer can be composed of only a metal catalyst. In addition, the porosity of the fuel electrode layer is usually 20 to 50%, preferably 30 to 40%. The thickness of the fuel electrode layer is usually 5 to 50 μm.

As the material of the air electrode layer, for example, a metal oxide having a perovskite crystal structure can be used. Specifically, (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Sr) (Fe, Co , Ni) O _{3 and the} like, and (La, Sr) MnO ₃ is preferably used from the viewpoint of stability in an oxidizing atmosphere. One kind of the metal oxides described above may be used alone, or two or more kinds may be mixed and used. Moreover, noble metals, such as platinum, ruthenium, and palladium, can also be used as a material for forming the air electrode layer. The porosity of the air electrode layer is usually 20 to 50%, preferably 30 to 40%. The thickness of the air electrode layer is usually 5 to 50 μm.

  As the material of the electrolyte layer, for example, a composite metal oxide containing at least one selected from zirconium oxide, cerium oxide, and lanthanum oxide, which is widely known as an electrolyte material for a solid oxide fuel cell, can be used. Specific examples of such composite metal oxides include YSZ, scandia-stabilized zirconia (hereinafter abbreviated as “ScSZ”), Samaria doped ceria (hereinafter abbreviated as “SDC”), gadolinium doped ceria ( Hereinafter, abbreviated as “GDC”), lanthanum garade and the like. The composite metal oxide preferably has a fluorite-type or perovskite-type crystal structure from the viewpoint of oxide ion conductivity. The thickness of the electrolyte layer is usually 10 nm to 100 μm, preferably 10 nm to 10 μm, more preferably 100 nm to 5 μm, and most preferably 100 nm to 1 μm. When the thickness is less than 10 nm, the pair of porous electrode layers may come into contact with each other. On the other hand, when the thickness exceeds 100 μm, the oxide ion conductivity of the electrolyte layer may be lowered.

  The current collecting material may be granular or film-shaped. In particular, it is preferable to use a current collecting material made of particles having a diameter of 1 μm or less or a current collecting material made of a film having a thickness of 1 μm or less. This is because the gas diffusion function of the porous electrode layer can be maintained and the current collecting performance can be improved. In addition, when the said current collection material is granular, the particle size is 10 nm or more normally. Moreover, when the said current collection material is a film | membrane form, the film thickness is 10 nm or more normally.

As the current collecting material, a general current collecting material can be used. For example, a metal material or a metal oxide material can be used. Specifically, conductive metals such as Pt, Au, Pd, Ag, Ni, and Cu, and lanthanum such as La (Cr, Mg) O ₃ , (La, Ca) CrO ₃ , (La, Sr) CrO _3, etc. -Those containing chromite-based conductive ceramic materials can be used. The current collecting material may be made of the same material as the electron conductive material constituting the one porous electrode layer. This is because the adhesion between the current collecting material and the pore wall surface of the one porous electrode layer is improved. In addition, the “current collecting material” in the present specification may be any material that can exhibit a current collecting effect at least during power generation. For example, a material that can exhibit a current collecting effect by being reduced during power generation, such as nickel oxide, may be used.

  In this invention, it is preferable that the said current collection material adheres to a part of surface except the contact surface with the said electrolyte layer among the surfaces of said one porous electrode layer. This is because electricity can be taken out from the current collecting material attached to the surface of the porous electrode layer.

  The pores in the one porous electrode layer preferably have an average diameter of 1 μm to 100 μm, and more preferably 1 μm to 10 μm. When the average diameter of the pores is less than 1 μm, the gas permeability of the one porous electrode layer may be lowered. On the other hand, when the average diameter of the pores exceeds 100 μm, the strength of the one porous electrode layer may decrease. Note that the average diameter of the pores in the other porous electrode layer is also preferably within the above numerical range for the same reason as described above.

  Next, an example of a preferred method for producing the above-described solid oxide fuel cell of the present invention will be described.

  First, an electrolyte substrate formed using means such as press molding is prepared, and one porous electrode layer is formed on one main surface of the electrolyte substrate using means such as screen printing.

  Next, by immersing the one porous electrode layer in a solution containing a metal source having a metal as a current collecting material, a metal oxide (collector) is collected along at least a part of the pore wall surface of the porous electrode layer. (Electrical material) is adhered in the form of particles or film.

  Any metal source may be used as long as it contains a metal element constituting the current collecting material and dissolves in a solvent described later. 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.

  Although the metal element which comprises the said current collection material is not specifically limited, For example, Ca, Cr, Sr, Nb, Mo, Sb, Te, Ba, W, 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, these metal elements are regions that exist as metal oxides (hereinafter referred to as “metal oxide regions”) or regions that exist as metal hydroxides (hereinafter referred to as “metal hydroxide regions”). Therefore, it is suitable as a main constituent element of a metal oxide.

  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 (ethyl acetoacetate), Titanium peroxo ammonium citrate tetrahydrate, Dicyclopentadienyl iron (II), Iron lactate (II) 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 monoacetylate Tonate, zirconium acetylacetonate bisethylacetoacetate, zirconium acetate, zirconium monostearate, penta-n-butoxyniobium, pentaethoxyniobium, pentaisopropoxyniobium, tris (acetylacetonato) indium (III), 2-ethylhexane Indium (III) oxide, tetraethyltin, dibutyltin (IV) oxide, tricyclohexyltin (IV) hydroxide, lanthanum acetylacetonate dihydrate, tri (methoxyethoxy) lanthanum, pentaisopropoxytantalum, pentaethoxytantalum, tantalum (V) Ethoxide, cerium (III) acetylacetonate n-hydrate, lead (II) citrate trihydrate, lead cyclohexanebutyrate and the like. In addition, chromium (III) acetylacetonate, gallium trifluoromethanesulfonate (III), strontium dipivaloylmethanate, niobium pentachloride, molybdenylacetylacetonate, palladium (II) acetylacetonate, antimony chloride (III ), Sodium tellurate, barium chloride dihydrate, tungsten chloride (VI), and the like.

  The solvent used for the solution containing the metal source is not particularly limited as long as it can dissolve the metal source. For example, when the metal source is a metal salt, a lower alcohol having a total carbon number of 5 or less such as methanol, ethanol, 2-propanol, 1-propanol, butanol, water, toluene, a mixed solvent thereof or the like may be used. In the case where the metal source is a metal complex or an organometallic compound, water, the above-described lower alcohol, toluene, a mixed solvent thereof or 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 solution can be obtained.

  The concentration of the metal source in the 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 formation reaction is unlikely to occur, and the desired metal oxide may not be obtained. If the concentration exceeds 10 mol / liter, a precipitate is formed. Because there is a possibility of doing.

  The solution preferably further contains at least one selected from an oxidizing agent and a reducing agent in addition to the metal source. This is because the formation reaction of the metal oxide can be promoted. For example, when an oxidizing agent is contained in the solution, oxidation of metal ions or the like formed by dissolving the metal source is rapidly performed, and thus a metal oxide generation reaction is promoted. In addition, for example, when a reducing agent is included in the solution, it is considered that the reducing agent decomposes and emits electrons to induce an electrolysis reaction of water (solvent). When water electrolysis occurs, hydroxide ions are generated, which increases the pH of the solution and shifts to the metal oxide region or metal hydroxide region in the Pourbaix diagram. The production reaction of 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 solution varies depending on the kind of the oxidizing agent, but is usually 0.001 to 1 mol / liter, and preferably 0.01 to 0.1 mol / liter. If the concentration is less than 0.001 mol / liter, the effect of promoting the metal oxide formation reaction may not be sufficiently exhibited. If the concentration exceeds 1 mol / liter, the effect is commensurate with the increase in concentration. 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 solution varies depending on the type of the reducing agent, but is usually 0.001 to 1 mol / liter, and preferably 0.01 to 0.1 mol / liter. If the concentration is less than 0.001 mol / liter, the effect of promoting the metal oxide formation reaction may not be sufficiently exhibited. If the concentration exceeds 1 mol / liter, the effect is commensurate with the increase in concentration. Is not preferable in terms of cost.

  The solution may contain additives such as an auxiliary ion source and a surfactant.

  The auxiliary ion source generates hydroxide ions by reacting with electrons, and can raise the pH of the solution and promote the formation reaction of metal oxides. 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, but even if the solution does not contain a reducing agent, it is separated from oxygen by heating. It 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.
(Chemical formula 1) ClO ₄ ⁻ + H ₂ O + 2e ⁻ ⇔ ClO ₃ ⁻ + 2OH ⁻
(Chemical 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 -
(Of _{^{6) 2BrO - + 2H 2 O}} + 2e - ⇔ Br 2 + 4OH -
(Chemical Formula 7) NO ₃ ⁻ + H ₂ O + 2e ⁻ ＮＯ NO ₂ ⁻ + 2OH ⁻
(Chemical Formula 8) NO ₂ ⁻ + 3H ₂ O + 3e ⁻ ＮＨ NH ₃ + 3OH ⁻
The hydroxide ions generated according to the above reaction formula can increase the pH of the solution and promote the metal oxide formation reaction.

  The said surfactant can improve the wettability of the said solution with respect to the pore wall surface of a porous electrode layer, and can promote the production | generation reaction of a metal oxide. 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.

  When immersing the porous electrode layer in the solution, at least one (preferably both) of the solution and the porous electrode layer may be maintained at a temperature of 10 ° C. or higher. This is because the formation reaction of the metal oxide can be promoted. In order to further promote the formation reaction of the metal oxide, heating to a temperature of 50 ° C. or higher is preferable, and heating to a temperature of 60 ° C. or higher is more preferable. In this case, the heating temperature is preferably set to a temperature not higher than the boiling point of the solution from the viewpoint of workability. For example, at least one (preferably both) of the solution and the porous electrode layer may be normally maintained in a range of 10 to 100 ° C, and may be heated to a range of 50 to 90 ° C from the viewpoint of productivity. preferable.

  When the porous electrode layer is immersed in the solution, a bubble-like oxidizing gas may be brought into contact with a portion where the porous electrode layer and the solution are in contact with each other. This is because oxidation of metal ions or the like formed by dissolving the metal source is promptly performed, so that the formation reaction of the metal oxide 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, the method for introducing the bubble-like oxidizing gas described above is not particularly limited, and examples thereof include a method using a bubbler. By using a bubbler, the contact area between the porous electrode layer and the solution in contact with the oxidizing gas can be increased, and the metal oxide production rate can be improved efficiently. Because you can. As such a bubbler, a general bubbler can be used, and examples thereof include a Naflon bubbler (manufactured by ASONE). In addition, the oxidizing gas can be normally supplied to the solution from a gas cylinder, and ozone can be supplied to the solution from an ozone generator.

  Further, when the porous electrode layer is immersed in the solution, the portion where the porous electrode layer and the solution are in contact may be irradiated with ultraviolet rays. 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. It is because the production | generation reaction of can be accelerated | stimulated. Moreover, by irradiating with ultraviolet rays, hydroxide ions can be generated from the auxiliary ion source described above, and the crystallinity of the resulting metal oxide 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 accelerate the production reaction. The intensity of the ultraviolet rays is usually 1 to 20 mW / cm ² , and preferably 5 to 15 mW / cm ² in order to further promote the production 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.

  After the metal oxide (that is, the current collecting material) is attached along at least a part of the pore wall surface of the one porous electrode layer by the above method, the main surface of the electrolyte substrate in contact with the one porous electrode layer The other porous electrode layer is formed on the main surface on the opposite side by using a method such as screen printing. With the above method, the solid oxide fuel cell of the present invention is obtained.

  In addition, as a method for attaching the current collecting material to the pore wall surface of the porous electrode layer, a method other than the above method may be used. For example, the current collecting material may be attached to the pore wall surface of the porous electrode layer by bringing the solution into contact with the one porous electrode layer.

  The method of bringing the solution into contact with the one porous electrode layer is not particularly limited, but the method does not lower the temperature of the porous electrode layer when the solution and the porous electrode layer are in contact with each other. It is preferable that This is because when the temperature of the porous electrode layer is lowered, a metal oxide formation reaction is difficult to occur, and a desired metal oxide (that is, a current collecting material) may not be obtained. Examples of a method that does not lower the temperature of the porous electrode layer include a method of bringing the above solution into contact with the porous electrode layer as droplets. At this time, the droplets preferably have a small diameter of, for example, about 0.001 to 1000 μm. If the diameter of the droplet is within the above range, the solvent of the solution can be instantly evaporated, and the temperature drop of the porous electrode layer can be suppressed. This is because a metal oxide can be obtained.

  The method of bringing the solution droplets into contact with the porous electrode layer is not particularly limited. Specifically, the method of bringing the solution into contact with the porous electrode layer by spraying the solution. For example, a method of bringing the solution into contact with the porous electrode layer by passing the porous electrode layer through a space in which the solution is mist-like may be used. According to the above method, the solution enters from the pore opening formed on the surface of the porous electrode layer, and the solution adheres to the pore wall surface of the porous electrode layer.

  Examples of the method of spraying the solution onto the porous electrode layer 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 0.001-1000 micrometers normally, It is preferable that it is 0.01-100 micrometers especially. This is because, if the diameter of the droplet is within the above range, a decrease in the temperature of the porous electrode layer can be suppressed, and a homogeneous metal oxide can be obtained.

  Further, the spray gas of the spray device is not particularly limited as long as it does not inhibit the production of metal oxides, and examples thereof include air, nitrogen, argon, helium, oxygen, etc. Preferred gases are nitrogen, argon, and helium. 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. For example, a hand spray (manufactured by ASONE), an ultrasonic nepriser (manufactured by OMRON), or the like can be used.

  In the case of using a method in which the porous electrode layer is passed through a mist-like space of the above solution, the droplet diameter is usually 0.001 to 1000 μm, and preferably 0.01 to 100 μm. This is because, if the diameter of the droplet is within the above range, a decrease in the temperature of the porous electrode layer can be suppressed, and a homogeneous metal oxide can be obtained.

  Moreover, in order to promote the production | generation reaction of a metal oxide, when making the said solution contact on a porous electrode layer, it is preferable to heat the said porous electrode layer. For example, the porous electrode layer may be heated to the metal oxide generation temperature or higher. Here, the “metal oxide formation temperature” is the lowest temperature at which the metal element forming the metal source combines with oxygen to form a metal oxide on the porous electrode layer. The metal oxide formation temperature varies greatly depending on the type of the metal source and the composition of the solution such as a solvent, and is usually in the range of 300 to 1000 ° C. In particular, from the viewpoint of productivity, it is preferable to select the type of metal source, the solvent, and the like so as to be within a range of 400 to 700 ° C. On the other hand, when the solution contains an oxidizing agent or a reducing agent, the metal oxide formation temperature is usually in the range of 150 to 800 ° C., and particularly in the range of 300 to 500 ° C. from the viewpoint of productivity. Thus, it is preferable to select the type of metal source, the solvent, and the like.

  The metal oxide formation temperature can be measured by the following method. First, the above solution containing a desired metal source is prepared. Next, by changing the surface temperature of the porous electrode layer by heating the porous electrode layer, the solution is brought into contact with the porous electrode layer to thereby form a metal electrode to generate a metal oxide. Of the surface temperatures, the lowest surface temperature is measured. This minimum surface temperature can be referred to as a “metal oxide formation temperature” in the present specification. At this time, whether or not the metal oxide is generated is obtained by judging from the result obtained by, for example, an X-ray diffractometer (manufactured by Rigaku, RINT-1500) when the obtained metal oxide has crystallinity. In the case where the metal oxide is an amorphous film, it can be judged from the result obtained by, for example, a photoelectron spectroscopic analyzer (manufactured by VG Scientific, ESCALAB 200i-XL).

  The heating method for the porous electrode layer 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 electrode layer can be reliably maintained at a desired temperature.

  In this method, the solution may be contacted on the porous electrode layer in an oxidizing gas atmosphere. This is because oxidation of metal ions or the like formed by dissolving the metal source is promptly performed, so that the formation reaction of the metal oxide 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 method, when contacting the said solution on a porous electrode layer, you may irradiate an ultraviolet-ray to the location where a porous electrode layer and the said solution 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. It is because the production | generation reaction of can be accelerated | stimulated. Moreover, by irradiating with ultraviolet rays, hydroxide ions can be generated from the auxiliary ion source described above, and the crystallinity of the resulting metal oxide 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 accelerate the production reaction. The intensity of the ultraviolet rays is usually 1 to 20 mW / cm ² , and preferably 5 to 15 mW / cm ² in order to further promote the production 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 method, ultraviolet rays may be irradiated to a portion where the porous electrode layer and the solution are in contact with each other in the above-described oxidizing gas atmosphere.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings as appropriate. FIG. 1 to be referred to is a schematic cross-sectional view showing a solid oxide fuel cell according to an embodiment of the present invention. FIG. 2 to be referred to is a schematic cross-sectional enlarged view of the fuel electrode layer of the solid oxide fuel cell shown in FIG.

  As shown in FIG. 1, the solid oxide fuel cell 10 includes an electrolyte layer 11, and a fuel electrode layer 12 and an air electrode layer 13 that sandwich the electrolyte layer 11. As shown in FIG. 2, the current collecting material 14 adheres along a part of the pore wall surface 12 a of the fuel electrode layer 12. Thereby, since the contact surface of the current collection material 14 and the fuel electrode layer 12 can be increased, current collection performance can be improved.

  Further, as shown in FIG. 1, the current collecting material 14 is also attached to the surface 12 b of the fuel electrode layer 12. Thereby, electricity can be taken out from the current collecting material 14 attached to the surface 12 b of the fuel electrode layer 12.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, the case where the current collecting material is attached along a part of the pore wall surface of the fuel electrode layer has been described as an example, but the present invention is not limited to this, and the pore wall surface of the air electrode layer The current collecting material may adhere along a part, or the current collecting material may adhere along a part of the pore wall surfaces of both the fuel electrode layer and the air electrode layer.

  Next, an example of a method for manufacturing the above-described solid oxide fuel cell 10 will be described with reference to the drawings. FIGS. 3A and 3B and FIGS. 4A and 4B to be referred to are schematic process diagrams showing an example of a method for manufacturing the solid oxide fuel cell 10 described above. 3 and 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  First, as shown in FIG. 3A, the fuel electrode layer 12 is formed on the electrolyte layer 11 (electrolyte substrate) by means of screen printing or the like. Next, a metal source having a metal to be the current collecting material 14 (see FIG. 1) and, for example, a reducing agent are dissolved in a solvent such as water to prepare a solution 1 (see FIG. 3B). Then, as shown in FIG. 3B, the fuel electrode layer 12 is immersed in the solution 1. Thereby, as shown in FIG. 4A, the current collecting material 14 adheres along a part of the pore wall surface 12 a of the fuel electrode layer 12. Thereafter, the fuel electrode layer 12 is taken out from the solution 1.

  Next, as shown in FIG. 4B, the air electrode layer 13 is formed on the electrolyte layer 11 by means of screen printing or the like, and the solid oxide fuel 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.

In this example, a single cell having the structure shown in FIG. 1 was manufactured. First, GDC (Ce _0.9 Gd _0.1 O _1.9 ) powder (average particle size: 0.5 μm) is placed in a pressure-resistant container, molded with a uniaxial press at a pressure of 1 t / cm ² , packaged in a vacuum pack, Molding was again performed at a pressure of ² t / cm ^{2 with} a hydraulic press. Then, sintering (1450 degreeC, 10 hours) was performed, and the electrolyte substrate (thickness: 0.5 mm) was produced.

Next, NiO powder (average particle size: 1 μm) and SDC (Ce _0.8 Sm _0.2 O _1.9 ) powder (average particle size: 1 μm) are added to ethyl carbitol, and the mass ratio (NiO: SDC) is 7: 3. In addition, ethyl cellulose was further added as a binder, and these were mixed by a ball mill to prepare a fuel electrode paste (viscosity: 5 × 10 ⁵ mPa · s) for forming a fuel electrode layer. Next, the fuel electrode paste was printed on the electrolyte substrate by a screen printing method. Thereafter, these were dried in an oven at 130 ° C. for 15 minutes and fired at 1450 ° C. for 1 hour to form a fuel electrode layer (thickness: 50 μm) on the electrolyte substrate.

Next, Sm _0.5 Sr _0.5 CoO ₃ (average particle size: 3 μm) is added to ethyl carpitol, and ethyl cellulose is further added as a binder, and these are mixed by a ball mill to form an air electrode layer. A paste (viscosity: 5 × 10 ⁵ mPa · s) was prepared. Next, the air electrode paste was printed on the surface of the electrolyte substrate opposite to the surface on which the fuel electrode layer was formed by a screen printing method. Thereafter, these were dried in an oven at 130 ° C. for 15 minutes and fired at 1200 ° C. for 1 hour to form an air electrode layer (thickness: 50 μm) on the electrolyte substrate. In the above process, a laminate comprising a fuel electrode / electrolyte substrate / air electrode was obtained.

Subsequently, in a mixed solvent of water and isopropyl alcohol (IPA) (volume ratio of water: IPA is 80:20), indium chloride tetrahydrate (InCl ₃ .4H ₂ O), tin chloride, and a reducing agent. A solution in which borane-dimethylamine complex (manufactured by Kanto Chemical Co., Inc.) was dissolved so as to have respective concentrations of 0.01 mol / liter, 0.001 mol / liter, and 0.02 mol / liter was prepared. Then, the laminate is immersed in the solution (temperature: 70 ° C.) for 24 hours, and ITO (indium oxide) is formed along a part of the pore wall surface of the fuel electrode layer and a part of the pore wall surface of the air electrode layer. A single cell was fabricated by attaching a current collecting material made of tin.

1 is a schematic cross-sectional view showing a solid oxide fuel cell according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional enlarged view of a fuel electrode layer of the solid oxide fuel cell shown in FIG. 1. A and B are schematic process diagrams showing an example of a method for producing a solid oxide fuel cell 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 according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solution 10 Solid oxide fuel cell 11 Electrolyte layer 12 Fuel electrode layer 12a Porous wall surface 12b Surface 13 Air electrode layer 14 Current collection material

Claims (7)

A method for producing a solid oxide fuel cell comprising an electrolyte layer and a pair of porous electrode layers sandwiching the electrolyte layer,
After forming at least one of the pair of porous electrode layers, the porous wall surface of the porous electrode layer is immersed in a solution containing a metal source having a metal as a current collecting material. A metal oxide is deposited along at least a part of the solid oxide fuel cell. The method for producing a solid oxide fuel cell according to claim 1, wherein the solution further includes at least one selected from an oxidizing agent and a reducing agent. The solution further includes at least one ionic species selected from chlorate ion, perchlorate ion, chlorite ion, hypochlorite ion, bromate ion, hypobromate ion, nitrate ion and nitrite ion. The method for producing a solid oxide fuel cell according to claim 1 or 2. The solid oxide fuel according to claim 1, wherein when immersing the one porous electrode layer in the solution, at least one of the solution and the one porous electrode layer is maintained at a temperature of 10 ° C or higher. Battery manufacturing method. The solid oxide according to claim 4, wherein when immersing the one porous electrode layer in the solution, at least one of the solution and the one porous electrode layer is heated to a temperature not higher than the boiling point of the solution. Of manufacturing a fuel cell. The method for producing a solid oxide fuel cell according to claim 1, wherein the metal source is at least one selected from a metal salt, a metal complex, and an organometallic compound. The metal source is Ca, Cr, Sr, Nb, Mo, Sb, Te, Ba, W, Mg, Al, Si, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Ag. The method for producing a solid oxide fuel cell according to claim 1 or 6, comprising at least one metal element selected from In, Sn, Ce, Sm, Pb, La, Hf, Sc, Gd, Ga, and Ta.

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