JP4863043B2 - Proton conducting fuel cell manufacturing method - Google Patents

Description

  The present invention relates to a proton conductive fuel cell using a proton conductive metal oxide in an electrolyte layer and a method for manufacturing the same.

  In recent years, fuel cells that generate electricity by an electrochemical reaction between air (oxygen) and fuel gas (hydrogen or the like) have attracted attention as energy sources. Among fuel cells, a proton conductive fuel cell is known that uses a proton conductive polymer membrane such as Nafion (registered trademark) as an electrolyte layer. In general, proton conductive polymer membranes have low ionic conductivity and a high membrane resistance when the water content is low. Therefore, in a fuel cell using a proton conductive polymer membrane, in order to keep the membrane resistance within a practical range, it is necessary to operate at a low temperature that can avoid extreme evaporation of moisture. At present, the fuel cell is normally used at an operating temperature of 150 ° C. or lower.

  In general, the electrode reaction of a fuel cell proceeds more smoothly as the operating temperature is higher. On the other hand, when the operating temperature is extremely high, in a system using a fuel cell, it is necessary to use a component member or a structure that takes heat resistance into consideration, and design restrictions are increased. Against this background, a proton conduction fuel cell having an operating temperature in the range of about 200 to 500 ° C. is desired.

As a proton-conducting fuel cell that satisfies the above requirements, Non-Patent Document 1 proposes a proton-conducting fuel cell that uses a proton-conductive metal oxide as an electrolyte layer. In this proton conducting fuel cell, since the BaCeO ₃ perovskite type metal oxide is used for the electrolyte layer, the operating temperature can be increased as compared with a fuel cell using a conventional proton conducting polymer membrane.
11th Fuel Cell Symposium Lecture Proceedings A20 (73-75 pages)

  However, in the proton conduction fuel cell proposed in Non-Patent Document 1, since the electrolyte layer is formed by the laser ablation method, crystal grains that are substantially orthogonal to the thickness direction (that is, the proton movement direction) in the electrolyte layer. Since there are many boundaries, the proton conductivity of the electrolyte layer may be reduced. As a result, the electrical resistance (internal resistance) in the proton conducting fuel cell may increase.

  The present invention has been made in view of such circumstances, and it is possible to raise the operating temperature and to reduce the grain boundary that hinders the movement of protons in the electrolyte layer and a method for manufacturing the same. I will provide a.

The proton conductive fuel cell of the present invention is a proton conductive fuel cell having an electrolyte layer and a pair of porous electrode layers sandwiching at least a part of the electrolyte layer,
The region sandwiched between the pair of porous electrode layers in the electrolyte layer includes a crystal aggregate made of proton-conductive metal oxide,
The crystal has a columnar structure extending along a substantially normal direction of the surface of one of the porous electrode layers.

A method for producing a proton conductive fuel cell according to the present invention includes a porous electrode layer and an electrolyte layer formed on the porous electrode layer and made of a proton conductive metal oxide film. A manufacturing method of
The metal oxide film is formed by spraying a solution for forming a metal oxide film containing a metal source on the heated porous electrode layer.

  Since the proton conductive fuel cell of the present invention uses a proton conductive metal oxide in the electrolyte layer, the operating temperature can be increased. In addition, a region sandwiched between the pair of porous electrode layers in the electrolyte layer includes an aggregate of crystals, and a columnar structure in which the crystals extend along a substantially normal direction of the surface of one porous electrode layer. Therefore, grain boundaries that hinder the movement of protons in the electrolyte layer can be reduced. Thereby, since the proton conductivity of the electrolyte layer can be improved, for example, a proton conduction fuel cell capable of reducing the internal resistance can be provided. In addition, according to the method for producing a proton conducting fuel cell of the present invention, the above-described proton conducting fuel cell of the present invention can be easily produced.

  The proton conductive fuel cell of the present invention has an electrolyte layer and a pair of porous electrode layers that sandwich at least a part of the electrolyte layer, and is sandwiched by the pair of porous electrode layers among the electrolyte layers. The region includes an aggregate of crystals made of proton-conductive metal oxide. As a result, the operating temperature can be increased as compared with a fuel cell using a conventional proton conductive polymer membrane. In the proton conducting fuel cell of the present invention, the crystal has a columnar structure extending along a substantially normal direction of the surface of one of the porous electrode layers. Thereby, the grain boundary (for example, grain boundary of the direction orthogonal to the moving direction of a proton) which prevents the movement of the proton in an electrolyte layer can be reduced. Therefore, according to the proton conducting fuel cell of the present invention, the proton conductivity of the electrolyte layer can be improved, and therefore, for example, a proton conducting fuel cell capable of reducing internal resistance can be provided.

  As the pair of porous electrode layers, a fuel electrode layer and an air electrode layer can be used. In this case, the crystal has a columnar structure extending along a substantially normal direction of the surface of one of the fuel electrode layer and the air electrode layer. The pair of porous electrode layers only need to sandwich at least part of the electrolyte layer. Therefore, as described later, for example, a part of the electrolyte layer may be formed inside one of the pair of porous electrode layers. Further, one of the pair of porous electrode layers is not necessarily in contact with the electrolyte layer. For example, the pair of porous electrode layers may sandwich another layer (for example, a proton permeable membrane described later) together with the electrolyte layer.

Examples of the proton conductive metal oxide constituting the crystal include a metal oxide having a perovskite crystal structure. Of these, a metal oxide represented by the general formula ABO ₃ , wherein A is at least one element selected from the group consisting of alkaline earth metal elements, and B is a metal having an ionic radius smaller than that of A A metal oxide, which is at least one element selected from the group consisting of elements, is preferable because proton conductivity is good. Examples of such metal oxides include SrCeO ₃ , SrZrO ₃ , BaZrO ₃ , BaCeO ₃ , and CaZrO ₃ . In order to further improve the proton conductivity of the electrolyte layer, it is preferable that at least one of A and B is a plurality of metal elements having different valences. As such a metal oxide, a metal oxide having SrCeO ₃ as a base, in which about 1 to 15% of Ce as a constituent element is replaced with a trivalent metal element (for example, Sc), Examples thereof include metal oxides based on BaZrO _{3 in} which about 1 to 15% of the constituent element Zr is substituted with a trivalent metal element (for example, Y).

The materials for the fuel electrode layer and the air electrode layer are not particularly limited, and for example, the materials for the fuel electrode layer and the air electrode layer used in general solid polymer membrane fuel cells can be used. As an example, carbon fine particles carrying a platinum catalyst can be mentioned. Further, as a material of the fuel electrode layer, Y-added stabilized zirconia (hereinafter abbreviated as “YSZ”) and Ni cermet (Ni—YSZ), YSZ and Ru cermet (Ru—YSZ) Etc. can also be used. Further, as the material of the air electrode layer, lanthanum strontium manganate such as (La, Sr) MnO ₃ , (La, Sr) (Mn, Co) O _3, or (La, Sr) (Fe, Co) O ₃ etc. can also be used. The porosity of the fuel electrode layer and the air electrode layer is usually 20 to 60% by volume, preferably 30 to 50% by volume. The thicknesses of the fuel electrode layer and the air electrode layer are usually 5 to 50 μm. Moreover, the average diameter of the pores in the fuel electrode layer and the air electrode layer is preferably in the range of 0.1 to 100 μm, and more preferably in the range of 0.1 to 10 μm.

  In the present invention, in order to further improve the proton conductivity of the electrolyte layer, the aspect ratio of the crystal is preferably 2 or more. Here, the “aspect ratio” is obtained by dividing the crystal length in the substantially normal direction of the surface of the one porous electrode layer in the crystal by the crystal diameter in the direction orthogonal to the approximately normal direction in the crystal. Value. The crystal length in the substantially normal direction of the crystal is, for example, about 10 nm to 50 μm, and the crystal diameter of the crystal in the direction orthogonal to the substantially normal direction is, for example, about 5 nm to 25 nm.

  In the present invention, in order to further improve the proton conductivity of the electrolyte layer, the crystal is preferably a single crystal. In particular, it is preferable that both ends of the single crystal are in contact with the respective surfaces of the pair of porous electrode layers because proton conductivity can be further improved.

  The aggregate may be an aggregate in which the crystals are arranged along the surface of the one porous electrode layer. According to this configuration, since the crystals are in close contact with each other, the denseness of the electrolyte layer is improved. Thereby, the gas impermeability of the electrolyte layer can be improved.

  In the present invention, the electrolyte layer further includes a first film made of the metal oxide formed along the surface of the one porous electrode layer, and the assembly includes the first film. It may be an aggregate of the crystals arranged along the surface. According to this configuration, since the crystal contained in the first film is a crystal nucleus, and an aggregate of the crystals grown in a columnar shape from the crystal nucleus can be obtained, the aggregate in which the crystals are closer to each other is obtained. It can be. Thereby, the gas impermeability of the electrolyte layer can be further improved. In addition, in order to exhibit the said effect reliably, it is preferable that the thickness of the said 1st film is 10 nm or more and 10 micrometers or less, and it is more preferable that they are 10 nm or more and 1 micrometer or less.

  The electrolyte layer may further include a second coating that covers at least a part of a wall surface that forms pores in the one porous electrode layer. For example, when the second coating is present on the surface layer of the porous electrode layer located near the interface between the porous electrode layer and the electrolyte layer, the adhesion between the porous electrode layer and the electrolyte layer is improved. Therefore, it is preferable. In addition, when the second coating is present, the reaction field of the electrode reaction increases, so that the electrode reaction can be facilitated. In order to exhibit the effect more reliably, at least 10 nm (more preferably at least 100 nm, particularly preferably at least 1 μm) in the depth direction of the porous electrode layer from the interface between the porous electrode layer and the electrolyte layer. It is preferable that the second coating is present in the pores existing in the range up to. The thickness of the second coating is preferably 10 nm or more and 10 μm or less, and more preferably 10 nm or more and 1 μm or less. Within this range, it is possible to increase the reaction field of the electrode reaction while maintaining good gas permeability of the porous electrode layer. In addition, the material of the said 2nd film should just be the same as that of the said 1st film, for example.

  The thickness of the region sandwiched between the pair of porous electrode layers in the electrolyte layer is usually 10 nm to 50 μm, preferably 10 nm to 10 μm, more preferably 100 nm to 5 μm, and most preferably. Is 100 nm or more and 1 μm or less. 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, if the thickness exceeds 50 μm, the proton conductivity of the electrolyte layer may be reduced. The proportion of the aggregate of crystals having the columnar structure in the region of the electrolyte layer is, for example, 95% by volume or more, and is 98% by volume or more in order to further improve proton conductivity. Preferably, it is 100% by volume.

  In addition, the proton conducting fuel cell of the present invention may further include a proton permeable membrane that is disposed between the fuel electrode layer and the electrolyte layer and selectively transmits protons. For example, when a hydrogen-rich gas obtained by reforming a hydrocarbon-based fuel is used as a fuel gas, carbon dioxide contained in the hydrogen-rich gas can be prevented from diffusing into the electrolyte layer by the proton permeable membrane. This is because deterioration of the electrolyte layer due to carbon or the like can be prevented. In this case, in order to reliably separate only protons from the hydrogen rich gas, the proton permeable membrane preferably contains palladium. The proton permeable membrane has a thickness of usually 0.5 to 30 μm, preferably 1 to 15 μm.

  Next, the manufacturing method of the proton conduction fuel cell of the present invention will be described.

  In the method for producing a proton conducting fuel cell of the present invention, a solution for forming a metal oxide film containing a metal source on the porous electrode layer in a state where the porous electrode layer (fuel electrode layer or air electrode layer) is heated. To form an electrolyte layer made of a proton-conductive metal oxide film. The electrolyte layer obtained by this method includes an aggregate of crystals having a columnar structure extending along a substantially normal direction of the surface of the porous electrode layer. In addition, according to this method, for example, a heat treatment step at a high temperature of 1000 ° C. or higher is not required, and the electrolyte layer can be easily densified, so that the manufacturing process can be further simplified.

  The heating temperature of the porous electrode layer is preferably equal to or higher than the metal oxide film forming temperature. Here, the “metal oxide film formation temperature” is the lowest temperature at which a metal element constituting the metal source is combined with oxygen to form a metal oxide film on the porous electrode layer. The metal oxide film forming temperature varies greatly depending on the composition of the metal oxide film forming solution such as the type of metal source and solvent, and is usually in the range of 200 to 500 ° 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 in the range of 300 to 400 ° C. When the metal oxide film forming solution contains an oxidizing agent or a reducing agent described later, the metal oxide film forming temperature is usually in the range of 150 to 400 ° C., particularly 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 in the range of 300 to 400 ° C.

  The metal oxide film formation temperature can be measured by the following method. First, a metal oxide film forming solution containing a desired metal source is prepared. Next, by changing the heating temperature of the porous electrode layer and bringing the metal oxide film forming solution into contact with the porous electrode layer, a porous electrode layer capable of forming a metal oxide film Of these heating temperatures, the lowest heating temperature is measured. This minimum heating temperature can be referred to as a “metal oxide film forming temperature” in this specification. At this time, whether or not the metal oxide film is formed can be determined from the result obtained by, for example, an X-ray diffraction apparatus (RINT-1500, manufactured by Rigaku).

  The heating method of 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. Among them, a hot plate is used. Then, since the temperature of a porous electrode layer can be reliably hold | maintained at desired temperature, it is preferable.

  As the porous electrode layer used as a support substrate when forming the electrolyte layer, the above-described fuel electrode layer or air electrode layer can be used. The constituent materials and the like are the same as described above, and will be omitted. The porous electrode layer itself may be used as a support substrate for forming the electrolyte layer, or a porous support layer coated with a material for the electrode layer is used as the porous electrode layer. This may be used as a support substrate for forming the electrolyte layer. As a material for the porous support substrate, heat-resistant ceramics, heat-resistant metals, or the like can be used.

  Any metal source may be used as long as it contains the metal constituting the metal oxide film 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.

  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, Ca, Sr, Ba, Al, Si, Sc, Ti, It is at least one metal element selected from V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Ag, In, Sn, Hf, Ta, Pb, La, Ce, Sm, and Gd. Is preferred. 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, Ca, Sr, Ba, Sc, Y, Zr, and Ce, which can constitute a metal oxide having good proton conductivity, 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.

  By appropriately selecting the metal source, for example, a metal oxide film having a perovskite crystal structure suitable as an electrolyte material for a proton conducting fuel cell can be formed.

  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, 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 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.

  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, if a reducing agent is contained in the metal oxide film forming solution, it is considered that the reducing agent decomposes and emits electrons, thereby inducing an electrolysis reaction of water (solvent). When water electrolysis occurs, hydroxide ions are generated, which increases the pH of the metal oxide film forming solution and shifts to the metal oxide region or metal hydroxide region in the Pourbaix diagram. Therefore, 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.

  The metal oxide film forming 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 increase 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.
(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 surfactant can improve the wettability of the metal oxide film forming solution with respect to the surface of the porous electrode layer 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.

  Examples of the method of spraying the metal oxide film forming 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 0.1-1000 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 electrode layer due to spraying 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 solution for forming a metal oxide film is usually 0.001 to 1 liter / min. In order to further improve the denseness of the resulting metal oxide film, 0.001 to 0.001. It is preferably 05 liter / min. At this time, the thickness of the formed metal oxide film can be arbitrarily adjusted by spraying repeatedly. 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.

  Further, after forming a metal oxide film, that is, an electrolyte layer by the above method, the electrolyte layer may be washed and dried. The washing of the electrolyte layer is performed to remove impurities present on the surface of the electrolyte layer. Examples of the cleaning method include a method of cleaning using a solvent used in the metal oxide film forming solution. When the electrolyte layer is dried, the electrolyte layer may be left at room temperature to dry, or may be dried in a heating apparatus such as an oven.

  Next, on the electrolyte layer obtained by the above method, a porous electrode layer (fuel electrode layer or air electrode layer) paired with the porous electrode layer used as a support substrate when forming the electrolyte layer is formed. An example of a forming method will be described. First, a paste is prepared by adding the electrode layer material and a binder to a solvent, and this paste is applied onto the electrolyte layer by an application method such as a screen printing method or a doctor blade method. And these are dried at the temperature of about 100 degreeC, for example, and a fuel electrode layer or an air electrode layer is formed on the said electrolyte layer. By the above method, the proton conductive fuel cell of the present invention is obtained.

  The method for manufacturing a proton conductive fuel cell of the present invention has been described above. However, the method for manufacturing a proton conductive fuel cell of the present invention may include steps other than those described above. Below, the manufacturing method (only the formation method of an electrolyte layer) of the proton conduction type fuel cell of this invention to which processes other than the content mentioned above were added is demonstrated.

  First, (1) a porous electrode layer (fuel electrode layer or air electrode layer) is immersed in a solution for forming a first metal oxide film containing a metal source and an oxidizing agent or a reducing agent. A first metal oxide film (proton conductive metal oxide film) in contact with the electrode layer is formed. Next, (2) in a state where the first metal oxide film is heated to the metal oxide film formation temperature or higher, a second metal oxide film forming solution containing a metal source is sprayed on the first metal oxide film. As a result, a second metal oxide film (proton conductive metal oxide film) is formed, and an electrolyte layer composed of the first metal oxide film and the second metal oxide film is obtained. As a result, the same effects as those of the manufacturing method described above can be exhibited, and when the second metal oxide film is formed, the crystals contained in the first metal oxide film are used as crystal nuclei to form crystals in a columnar shape. Since it can be made to grow, the 2nd metal oxide film containing the aggregate | assembly which the crystals which consist of the said columnar structure closely_contact | adhered can be obtained. Therefore, the gas impermeability of the obtained electrolyte layer can be further improved. Note that a region of the first metal oxide film formed on the porous electrode layer corresponds to the “first coating”.

  Further, according to the above-described method, the first metal oxide film can be formed not only on the surface of the porous electrode layer but also on the wall surface forming the pores in the porous electrode layer. Usually, a part of the first metal oxide film obtained by the above-described method is formed along at least a part of the wall surface of the porous electrode layer. A part of the first metal oxide film formed along the wall surface forming pores in the porous electrode layer corresponds to the “second coating”.

  In addition, since said (2) process is the same as that of the above-mentioned, below, only the said (1) process is demonstrated and the overlapping description is abbreviate | omitted.

  The first metal oxide film forming solution used in the step (1) includes a metal source and an oxidizing agent or a reducing agent. Specific examples of the metal source, the oxidizing agent, and the reducing agent are the same as described above, and thus the description thereof is omitted. Further, the other components (solvent, additive, etc.) of the first metal oxide film forming solution are the same as described above, and thus the description thereof is omitted. The first metal oxide film forming solution and the second metal oxide film forming solution may be the same or different from each other. When the first metal oxide film forming solution is different from the second metal oxide film forming solution, the crystal of the first metal oxide film obtained by the first metal oxide film forming solution It is preferable to select each solution composition so that the system and the crystal system of the second metal oxide film obtained by the second metal oxide film forming solution are approximated (or matched).

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

  When the porous electrode layer is immersed in the first metal oxide film forming solution, a bubble-like oxidation is formed in a portion where the porous electrode layer and the first metal oxide film forming solution are in contact with each other. A sex gas may be contacted. This is because the metal ions and the like formed by dissolving the metal source are rapidly oxidized, so that the film formation reaction of the first 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, 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 portion where the porous electrode layer and the first metal oxide film forming solution are in contact with the oxidizing gas can be increased. This is because the deposition rate of the physical film can be improved efficiently. As such a bubbler, a general bubbler can be used, and examples thereof include a Naflon bubbler (manufactured by ASONE). Further, the oxidizing gas can be normally supplied from the gas cylinder to the first metal oxide film forming solution, and ozone can be supplied from the ozone generator to the first metal oxide film forming solution. .

  In addition, when the porous electrode layer is immersed in the first metal oxide film forming solution, ultraviolet light is applied to a portion where the porous electrode layer and the first metal oxide film forming solution are in contact with each other. It may be irradiated. 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. As described above, the first metal is generated by the generated hydroxide ions. This is because the film formation reaction of the oxide 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 first 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.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings as appropriate.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 to be referred to is a schematic cross-sectional view showing a proton conducting fuel cell according to the first embodiment of the present invention.

  As shown in FIG. 1, the proton conduction fuel cell 10 according to the first embodiment includes an electrolyte layer 11, and a fuel electrode layer 12 and an air electrode layer 13 that sandwich a part of the electrolyte layer 11. A region of the electrolyte layer 11 sandwiched between the fuel electrode layer 12 and the air electrode layer 13 includes an aggregate of crystals 11a made of proton conductive metal oxide. As a result, the operating temperature can be increased as compared with a fuel cell using a conventional proton conductive polymer membrane.

  The crystal 11 a has a columnar structure extending along the direction of the normal line of the surface 12 a of the fuel electrode layer 12, and these crystals 11 a are aggregates arranged along the surface 12 a of the fuel electrode layer 12. Is forming. This can reduce the grain boundaries that hinder the movement of protons in the electrolyte layer 11 (for example, the grain boundaries in the direction perpendicular to the direction of proton movement), thereby improving the proton conductivity of the electrolyte layer 11. Can do. Furthermore, since the crystals 11a are in close contact with each other, the denseness of the electrolyte layer 11 is improved. Thereby, the gas impermeability of the electrolyte layer 11 can be improved.

  Further, a part 11 b of the electrolyte layer 11 covers a part of the wall surface 12 b that forms pores in the fuel electrode layer 12. Thereby, since the reaction field of an electrode reaction increases, the electrode reaction in the fuel electrode layer 12 can be facilitated. The part 11b of the electrolyte layer 11 corresponds to the “second coating” described above.

  Next, an example of a method for manufacturing the proton conductive fuel cell 10 according to the first embodiment will be described with reference to the drawings. 2A to 2C to be referred to are schematic process diagrams showing an example of a method for manufacturing the proton conductive fuel cell 10 according to the first embodiment of the present invention. 2A to 2C, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  First, a metal source is dissolved in a solvent such as water to prepare a metal oxide film forming solution 1 (see FIG. 2A). Next, as shown in FIG. 2A, the fuel electrode layer 12 is heated to a metal oxide film formation temperature or higher by, for example, a hot plate (not shown) or the like, and the metal oxide film forming solution is sprayed by the spray device 2. 1 is sprayed on the fuel electrode layer 12. As a result, as shown in FIG. 2B, the electrolyte layer 11 including the aggregate of the crystals 11 a is formed on the fuel electrode layer 12. At this time, the part 11 b of the electrolyte layer 11 covers a part of the wall surface 12 b that forms pores in the fuel electrode layer 12.

  Subsequently, as shown in FIG. 2C, the air electrode layer 13 is formed on the electrolyte layer 11 by means of a screen printing method or the like, and the proton conduction fuel cell 10 according to the first embodiment is obtained.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 to be referred to is a schematic cross-sectional view showing a proton conducting fuel cell according to a second embodiment of the present invention. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 3, the proton conduction fuel cell 20 according to the second embodiment includes an electrolyte layer 21, and a fuel electrode layer 12 and an air electrode layer 13 that sandwich a part of the electrolyte layer 21. A region of the electrolyte layer 21 sandwiched between the fuel electrode layer 12 and the air electrode layer 13 includes an aggregate of crystals 21a made of proton conductive metal oxide. The electrolyte layer 21 further includes a coating 21b made of the metal oxide. The coating 21 b includes a region 211 b formed along the surface 12 a of the fuel electrode layer 12 and a region 212 b formed along a part of the wall surface 12 b that forms pores in the fuel electrode layer 12. The region 211b corresponds to the “first coating”, and the region 212b corresponds to the “second coating”.

  The crystals 21a have a columnar structure extending along a substantially normal direction of the surface 12a of the fuel electrode layer 12, and these crystals 21a form an aggregate arranged along the region 211b of the coating 21b. is doing. Thereby, the proton conduction fuel cell 20 according to the second embodiment has the same effect as the proton conduction fuel cell 10 according to the first embodiment described above, and crystallizes the crystals contained in the region 211b of the coating 21b. Since it is possible to obtain an aggregate of the crystals 21a that are grown as a nucleus from the crystal nucleus in a columnar shape, the aggregates of the crystals 21a can be made closer to each other. Thereby, the gas impermeability of the electrolyte layer 21 can be further improved.

  Next, an example of a method for manufacturing the proton conductive fuel cell 20 according to the second embodiment will be described with reference to the drawings. 4A and 4B and FIGS. 5A to 5C to be referred to are schematic process diagrams showing an example of a method for manufacturing the proton conductive fuel cell 20 according to the second embodiment of the present invention. 4A and 4B and FIGS. 5A to 5C, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

  First, a metal source and a reducing agent, for example, are dissolved in a solvent such as water to prepare a first metal oxide film forming solution 1a (see FIG. 4A). Then, as shown in FIG. 4A, the fuel electrode layer 12 is immersed in the first metal oxide film forming solution 1a. As a result, as shown in FIG. 4B, a coating 21b in contact with the fuel electrode layer 12 is formed. Thereafter, the fuel electrode layer 12 covered with the coating 21b is taken out from the first metal oxide film forming solution 1a.

  Next, as shown in FIG. 5A, the coating 21b and the fuel electrode layer 12 are heated to a temperature higher than the metal oxide film formation temperature by, for example, a hot plate (not shown) or the like, and then the second metal oxidation is performed by the spray device 2. The material film forming solution 1b (for example, the same composition as the first metal oxide film forming solution 1a) is sprayed onto the region 211b of the coating 21b. Thereby, as shown in FIG. 5B, an aggregate of the crystals 21a is formed on the region 211b of the film 21b, and the electrolyte layer 21 including the film 21b and the aggregate of the crystals 21a is obtained.

  Subsequently, as shown in FIG. 5C, the air electrode layer 13 is formed on the electrolyte layer 21 using means such as a screen printing method, and the proton conduction fuel cell 20 is obtained.

  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 crystals constituting the assembly have a columnar structure extending along the substantially normal direction of the surface of the fuel electrode layer is exemplified, but the crystals constituting the assembly are the air electrode layer. It may be a crystal having a columnar structure extending along a substantially normal direction of the surface. In that case, as shown in FIG. 6, a proton permeable membrane 30 such as a Pd alloy membrane may be disposed between the fuel electrode layer 12 and the electrolyte layer 11.

  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, Example 1 will be described.

Example 1
Platinum supported carbon, SrCeO ₃ powder (particle size range: 0.01 to 10 μm, average particle size: 1 μm), and cellulose-based binder resin have a mass ratio (platinum-supported carbon: SrCeO ₃ : cellulose-based binder resin). A paste was prepared in addition to 2-propanol so as to be 60:30:10. And after apply | coating this paste to the polyester film (thickness: 25 micrometers) which performed the silicon process with the blade coater, these were dried at 100 degreeC and the fuel electrode used as a porous electrode layer on the said polyester film ( (Thickness: 25 μm) was formed.

Subsequently, cerium (III) chloride (manufactured by Kanto Chemical Co., Inc.), strontium nitrate (manufactured by Wako Pure Chemical Industries, Ltd.), and yttrium chloride (manufactured by Junsei Chemical Co., Ltd.) were added at concentrations of 0.1 mol / liter and 0.03 mol, respectively. A solution for forming a metal oxide film was prepared by dissolving in pure water so as to be / mol and 0.01 mol / liter. Then, the metal oxide film-forming solution (150 ml) is sprayed onto the fuel electrode heated to 450 ° C. by hand spray (manufactured by ASONE), and the electrolyte layer made of SrCe _0.95 Y _0.05 O ₃ is applied to the fuel electrode. (Thickness on the fuel electrode: 1 μm) was formed. The injection amount at this time was 0.005 liter / min.

Subsequently, a platinum-supporting composite oxide-carbon composed of platinum, Sr _0.95 La _0.05 TiO ₃ and carbon and a cellulose-based binder resin have a mass ratio of 90 (platinum-supporting composite oxide-carbon: cellulose-based binder resin). : In addition to 2-propanol, a paste was prepared so as to be 10. The paste was applied onto the electrolyte layer with a blade coater, and then dried at 100 ° C. to form an air electrode (thickness: 20 μm) to obtain a proton conduction fuel cell (single cell). .

(Example 2)
Since Example 2 differs from Example 1 described above only in the formation method of the electrolyte layer, only the formation method of the electrolyte layer will be described.

Cerium (III) acetylacetonate (manufactured by Kanto Chemical Co., Inc.), strontium acetate (manufactured by Kishida Chemical Co., Ltd.), and yttrium chloride (manufactured by Junsei Chemical Co., Ltd.), with respective concentrations of 0.1 mol / liter and 0.03 mol / liter And it was made to melt | dissolve in the mixed solvent which consists of toluene, isopropanol, ethanol, and methyl ethyl ketone so that it might become 0.01 mol / liter, and the solution for metal oxide film formation was prepared. The mixed solvent used had a volume ratio (toluene: isopropanol: ethanol: methyl ethyl ketone) of 50: 20: 20: 10. Then, the metal oxide film-forming solution (150 ml) is sprayed onto the fuel electrode heated to 350 ° C. by hand spray (manufactured by ASONE), and the electrolyte layer made of SrCe _0.95 Y _0.05 O ₃ is applied to the fuel electrode. (Thickness on the fuel electrode: 3 μm) was formed. The injection amount at this time was 0.005 liter / min.

(Example 3)
Since Example 3 differs from Example 1 described above only in the formation method of the electrolyte layer, only the formation method of the electrolyte layer will be described.

Zirconium chloride oxide octahydrate (manufactured by Kanto Chemical Co., Inc.), barium nitrate (manufactured by Kishida Chemical Co., Ltd.) and yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.), with respective concentrations of 0.1 mol / liter and 0.01 mol / liter And it was made to melt | dissolve in the mixed solvent which consists of water, isopropanol, and ethanol so that it might become 0.01 mol / l, and the solution for metal oxide film formation was prepared. The mixed solvent used had a volume ratio (water: isopropanol: ethanol) of 30:50:20. Then, the metal oxide film forming solution (100 ml) is sprayed on the fuel electrode heated to 450 ° C. by hand spray (manufactured by ASONE), and the electrolyte layer made of BaZr _0.9 Y _0.1 O ₃ is applied on the fuel electrode. (Thickness on the fuel electrode: 3 μm) was formed. The injection amount at this time was 0.001 liter / min.

Example 4
Since Example 4 differs from Example 1 described above only in the formation method of the electrolyte layer, only the formation method of the electrolyte layer will be described.

Zirconium chloride oxide octahydrate (manufactured by Kanto Chemical Co., Inc.), calcium acetate (manufactured by Kishida Chemical Co., Ltd.) and yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.), with respective concentrations of 0.1 mol / liter and 0.01 mol / liter And it was made to melt | dissolve in the mixed solvent which consists of water, isopropanol, and ethanol so that it might become 0.01 mol / l, and the solution for metal oxide film formation was prepared. The mixed solvent used had a volume ratio (water: isopropanol: ethanol) of 50:30:20. Then, the metal oxide film forming solution (80 ml) is sprayed onto the fuel electrode heated to 400 ° C. by hand spray (manufactured by ASONE), and the electrolyte layer made of CaZr _0.9 Y _0.1 O ₃ is applied onto the fuel electrode. (Thickness on the fuel electrode: 3 μm) was formed. The injection amount at this time was 0.001 liter / min.

1 is a schematic cross-sectional view showing a proton conduction fuel cell according to a first embodiment of the present invention. FIGS. 4A to 4C are schematic process diagrams illustrating an example of a method for manufacturing a proton conductive fuel cell according to the first embodiment of the present invention. FIGS. It is a schematic cross section showing a proton conduction type fuel cell concerning a 2nd embodiment of the present invention. A and B are schematic process diagrams showing an example of a method for manufacturing a proton conducting fuel cell according to a second embodiment of the present invention. FIGS. 8A to 8C are schematic process diagrams illustrating an example of a method for manufacturing a proton conduction fuel cell according to a second embodiment of the present invention. FIGS. It is a schematic cross section which shows the proton conduction type fuel cell concerning another embodiment of the present invention.

Explanation of symbols

1,1a, 1b Metal oxide film forming solution 10,20 Proton conduction type fuel cell 11,21 Electrolyte layer 11a, 21a Crystal 12 Fuel electrode layer 12a Surface 12b Wall surface 13 Air electrode layer 21b Coating 30 Proton permeable membrane

Claims (11)

A method for producing a proton conductive fuel cell, comprising: a porous electrode layer; and an electrolyte layer made of a proton conductive metal oxide film formed on the porous electrode layer,
The proton conductive metal oxide film includes a first metal oxide film and a second metal oxide film,
By immersing the porous electrode layer in a first metal oxide film forming solution containing a metal source, the first metal oxide film in contact with the porous electrode layer is formed,
A method for producing a proton conduction fuel cell, wherein the second metal oxide film is formed by spraying a solution for forming a second metal oxide film containing a metal source on the heated first metal oxide film . The heating temperature of the first metal oxide film is equal to or higher than a minimum temperature at which the metal element constituting the metal source is combined with oxygen to form the second metal oxide film on the first metal oxide film. A method for producing a proton conducting fuel cell according to claim 1. The method for producing a proton conduction 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 Mg, Ca, Sr, Ba, Al, Si, Sc, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Ag, In, Sn, Hf, Ta The method for producing a proton-conducting fuel cell according to any one of claims 1 to 3, comprising at least one metal element selected from Pb, La, Ce, Sm, and Gd . 5. The method for producing a proton conductive fuel cell according to claim 1, wherein the first metal oxide film forming solution further includes at least one selected from an oxidizing agent and a reducing agent . The first metal oxide film forming solution is selected from chlorate ions, perchlorate ions, chlorite ions, hypochlorite ions, bromate ions, hypobromate ions, nitrate ions and nitrite ions. The method for producing a proton conduction fuel cell according to any one of claims 1 to 5, further comprising at least one ionic species . The method for producing a proton conductive fuel cell according to claim 1, wherein the second metal oxide film forming solution further includes at least one selected from an oxidizing agent and a reducing agent . The second metal oxide film forming solution is selected from chlorate ions, perchlorate ions, chlorite ions, hypochlorite ions, bromate ions, hypobromate ions, nitrate ions and nitrite ions. The method for producing a proton conductive fuel cell according to claim 1, further comprising at least one ionic species . When immersing the porous electrode layer in the first metal oxide film forming solution, at least one of the first metal oxide film forming solution and the porous electrode layer is maintained at a temperature of 10 to 100 ° C. A method for producing a proton conducting fuel cell according to any one of claims 1 to 8 . When the porous electrode layer is immersed in the first metal oxide film forming solution, a bubble-like oxidation is formed in a portion where the porous electrode layer and the first metal oxide film forming solution are in contact with each other. The manufacturing method of the proton conduction type fuel cell according to any one of claims 1 to 9, wherein a property gas is contacted. When the porous electrode layer is immersed in the first metal oxide film forming solution, the portion where the porous electrode layer is in contact with the first metal oxide film forming solution is irradiated with ultraviolet rays. The manufacturing method of the proton conduction type fuel cell of any one of Claims 1-10 .

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