Electrode for proton-conductive ceramic cell, method for manufacturing the same, and proton-conductive ceramic cell using the same

Abstract

To provide an electrode for a proton-conducting ceramic cell having a low electrode resistance and a high current density, a proton-conducting ceramic cell using the same, and a method for producing the same.SOLUTION: An electrode for a proton-conducting ceramic cell is made of at least an electron-conducting material, or is made of a proton conductive material (1) including at least an electron-conducting material and a proton-conducting material containing Ba, the mass ratio of the electron-conductive material and the proton conductive material (1) is 100:0 to 20:80, the film thickness of the electrode is 7.0 μm or less, and the porosity of the electrode is 20.0% by volume or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrode for a proton-conductive ceramic cell, a method for producing the same, and a proton-conductive ceramic cell using the same. [Background technology]

[0002] Solid oxide cells for electrochemical reactions are devices that enable highly efficient energy conversion, and research and development toward their practical application is underway by ceramic manufacturers, the energy industry, the automotive industry, etc. For example, they are used in devices such as fuel cell systems, electrolysis systems, and hydrogen compressors.

[0003] Typical examples of devices using solid oxide cells include solid oxide fuel cells and solid oxide electrolysis cells. A solid oxide cell is composed of a dense electrolyte, primarily made of oxide, sandwiched between two porous electrodes: an air electrode and a fuel electrode. Depending on the constituent materials, a wide operating temperature range can be selected for this solid oxide cell, and it can be used in the range of 400 to 1000°C.

[0004] The electrode material is an electron-conductive oxide or metal with catalytic activity (hereinafter referred to as "electron-conductive material"). Although electron-conductive materials may be used alone, they may also be mixed with an ion-conductive material that conducts the same ions as the electrolyte or the same ions as the electrolyte ("ions" refers to all ions that act as conductive carriers, including oxide ions and protons), in order to expand the reaction field within the electrode. In general, the reaction resistance of the electrode is reduced by mixing an electron-conductive material with an ion-conductive material. The reaction resistance depends on the size of the reaction field (or the number of reaction active sites) per unit area of ​​the electrode and the activity per reaction field.

[0005] When mixing electronically conductive materials and ionically conductive materials, a mixture in which at least one of the materials has an average particle size of 1 μm or less is called a composite, and by combining these materials, the effect of reducing the reaction resistance of the electrode can be significantly achieved.

[0006] Conventionally, electrodes have been made porous so that the gas required for the electrochemical reaction can be supplied to the reaction field within the electrode and the gas generated by the electrochemical reaction can be removed (hereinafter, the supply and removal of gas is referred to as "gas diffusion"). This has led to an increase in the porosity of the electrode, thereby reducing the gas diffusion resistance within the electrode that occurs with gas diffusion. For example, in order to sufficiently reduce the gas diffusion resistance, the porosity of the electrode has been set to at least 30% by volume, and more often, the porosity has been set to about 40% by volume.

[0007] The combined resistance of the electrode reaction resistance and gas diffusion resistance is called the electrode resistance.

[0008] Examples of electron-conductive materials for the air electrode of solid oxide cells include perovskite-type oxide materials, such as (LaBa)MnO3, (LaBa)FeO3, (LaBa)CoO3, (LaBa)(CoFe)O3, etc. In the above electron-conductive materials, La can be substituted or partially substituted with other lanthanides (Pr, Sm, Gd), and Ba can be substituted or partially substituted with other alkaline earth metals (Ca, Sr).

[0009] Metallic materials (e.g., Ti, Mn, Fe, Co, Ni, and Cu) are used as electronically conductive materials for the anode of solid oxide cells. Metallic materials include those that are reduced by gases such as hydrogen, carbon monoxide, hydrocarbons, and biofuels. For example, if NiO (oxide) is used as a manufacturing material, the NiO is reduced to Ni (metal) when the solid oxide cell is constructed and operated with the above gases.

[0010] In solid oxide cells, the charge carrier ions are mainly oxide ions and protons. Among solid oxide cells, those in which the charge carrier ions are mainly protons are called proton-conducting ceramic cells. In proton-conducting ceramic cells, the material that conducts protons is called a proton-conducting electrolyte. Typical examples of proton-conducting electrolytes include perovskite-type oxide materials.

[0011] Compared to oxide-ion conducting ceramic cells, proton conducting ceramic cells have the advantage of being able to increase fuel utilization rate because water vapor is not generated at the anode when used in fuel cells, and being able to increase the hydrogen concentration by discharging hydrogen to the anode side when used as an electrolysis cell, resulting in higher energy conversion efficiency. Furthermore, because the activation energy of proton conduction is low, proton conducting ceramic cells have the advantage of being able to be used at lower operating temperatures than oxide-ion conducting ceramic cells.

[0012] Here, an important issue for the widespread use of proton-conducting ceramic cells is improving the energy conversion performance per unit volume, which directly leads to cost reduction. An important factor in the energy conversion performance per unit volume of a proton-conducting ceramic cell is the current per unit area of ​​the electrode (hereinafter referred to as "current density"), and various research and development efforts are currently underway with the aim of increasing the current density.

[0013] The dominant factor that determines the current density of a proton-conducting ceramic cell is the electrode resistance. Electrochemical reactions and gas diffusion occurring at the electrodes generate overvoltage (the voltage difference between the equilibrium state and the operating state). High-efficiency operation requires electrodes with low electrode resistance that can achieve high current densities even at low overvoltages.

[0014] Regarding the research and development of proton-conducting ceramic cells to date, for example, in Patent Document 1, there is an electrode for a solid oxide fuel cell that contains an electron-conducting material and an ion-conducting material, where the mass ratio of the electron-conducting material to the ion-conducting material is 75:25 to 25:75, the average particle diameter of the primary particles in each of the electron-conducting material and the ion-conducting material is 1 nm to 1 μm, the film thickness of the electrode is 0.5 μm to 50 μm, and the porosity of the electrode is 1 to 30% by volume. Also, in Patent Document 2, there is a membrane electrode assembly comprising an electrode composed of a composite material containing a metal and a first electrolyte having proton conductivity, and an electrolyte layer composed of a second electrolyte having proton conductivity, where the electrode and the electrolyte layer are laminated, and in the electrode, the volume ratio occupied by the metal is 57% or more, and the first electrolyte and the second electrolyte are Ba , Zr 1-x M x O3, Ba。 a Ce 1-x M x O3, and Ba a Zr 1-x-y Ce x M y O3 (M is at least one element selected from the group consisting of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, Sc, Mn, Fe, Co, Ni, Al, Ga, In, Lu, 0 < x <1, 0 < y <1, 0.95 ≦ a ≦ 1.05), and a membrane electrode assembly represented by any one of the composition formulas is disclosed. [Prior Art Documents] <​​​​​​​​​​​​​​​​​​​​ As described above, in order to reduce the cost of proton-conducting ceramic cells, it is necessary to dramatically reduce the electrode resistance compared to conventional technologies. However, although the above conventional technologies have succeeded in reducing the electrode resistance of proton-conducting ceramic cells, further reduction in electrode resistance and realization of higher current density are required for the early widespread use and commercialization of proton-conducting ceramic cells.

[0017] Therefore, an object of the present invention is to provide an electrode for a proton-conductive ceramic cell having low electrode resistance and high current density, a proton-conductive ceramic cell using the same, and a method for producing the same. [Means for solving the problem]

[0018] As a result of intensive research to solve the above problems, the present inventors have found that (1) when forming an electrode material precursor into a coating film and firing it, a nitrate-containing electrode material precursor in which nitrate is present in the electrode material precursor is used, and the coating film made of the nitrate-containing electrode material precursor is compressed under pressure and then fired, the degree of sintering of the oxide powder material for an electrode can be increased, the bonding area between particles can be increased, and the porosity can be reduced; and (2) by reducing the thickness of the electrode, the electrode resistance can be dramatically reduced. Furthermore, (3) by using a proton-conductive material (1) containing Ba together with an electron-conductive material as the oxide powder material for an electrode, the electrode resistance can be further reduced, and the present invention has been developed based on these findings.

[0019] That is, the present invention (1) is an electrode for a proton-conducting ceramic cell, at least , electric The electrode is formed of a proton conductive material and a proton conductive material containing Ba (1), The mass ratio of the electron conductive material to the proton conductive material (1) is 100:0 Exceeding 20:80 below and The proton-conducting material (1) is represented by the following general formula (1): (Baα 1 A1 (1-α 1) ) x1 B1 y1 O 3+z1 (1) (In formula (1), A1 is at least one of Ca, Sr, and La; B1 is at least one of Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu; α1 is 0.20 to 1.00; x1 is 0.80 to 1.20; y1 is 0.80 to 1.20; and z1 is −0.80 to 0.80.) is a perovskite oxide material represented by The electrode has a film thickness of 7.0 μm or less, the porosity of the electrode is 20.0% by volume or less; The present invention provides an electrode for a proton-conducting ceramic cell, characterized by the above.

[0021] In addition, the present invention ( 2 ) is characterized in that, in the electrode for a proton-conductive ceramic cell, when the thickness of the electrode is 0.1 μm≦thickness of the electrode<2.0 μm, the porosity of the electrode is 0.0 to 10.0% by volume. 1 ) an electrode for a proton-conducting ceramic cell.

[0022] In addition, the present invention ( 3 ) is characterized in that, in the electrode for a proton-conductive ceramic cell, when the thickness of the electrode is 2.0 μm≦thickness of the electrode≦7.0 μm, the porosity of the electrode is 0.0 to 20.0% by volume. 1 ) an electrode for a proton-conducting ceramic cell.

[0023] In addition, the present invention ( 4 ) is a value in which the electrical conductivity of the electrode is 1 to 2000 S / cm 2 (1) to ( 3 ) an electrode for a proton-conducting ceramic cell.

[0024] The present invention (5) also provides at least , electric a nitrate-containing electrode material precursor preparation step of preparing a nitrate-containing electrode material precursor containing a metal element of a proton-conductive material source and a metal element of a proton-conductive material (1) source, in which at least a portion of the metal element is present as a nitrate; a step of preparing a slurry for forming an electrode by mixing and dispersing the nitrate-containing electrode material precursor in a solvent to obtain a slurry for forming an electrode; an electrode coating film forming step of applying the electrode-forming slurry to an object to be coated and then drying the slurry to obtain a nitrate-containing electrode material precursor coating film; a pressing step of pressing the nitrate-containing electrode material precursor coating film at 10 to 500 MPa by cold isostatic pressing to obtain a pressurized product of the nitrate-containing electrode material precursor coating film; a firing step of firing the pressure-treated nitrate-containing electrode material precursor coating at 700 to 1200°C to obtain an electrode for a proton-conductive ceramic cell; The present invention provides a method for producing an electrode for a proton-conductive ceramic cell, characterized by comprising the steps of: (1)

[0025] The present invention (6) also provides the method for preparing a nitrate-containing electrode material precursor, ,before The present invention also provides a method for producing an electrode for a proton-conductive ceramic cell according to (5), characterized in that the method comprises a spray pyrolysis step of atomizing an aqueous solution for spraying containing metal ions of the electron-conductive material source, metal ions of the proton-conductive material (1) source, and nitrate ions, and then spray pyrolyzing the atomized aqueous solution for spraying to obtain a nitrate-containing electrode material precursor.

[0027] In addition, the present invention ( 7 ) comprises an electrolyte formed of at least a proton-conducting material (2), an air electrode; a fuel electrode; and Either one or both of the air electrode and the fuel electrode is (1) to ( 4 ) an electrode for a proton-conducting ceramic cell, The present invention provides a proton-conducting ceramic cell characterized by the above.

[0028] In addition, the present invention ( 8 ) is a proton-conductive material (2) represented by the following general formula (2): (Baα2A2 (1- α 2)) x2 B1 y2 O 3+z2 (2) (In formula (2), A2 is at least one of Ca, Sr, and La; B2 is at least one of Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu; α2 is 0.20 to 1.00; x2 is 0.80 to 1.20; y2 is 0.80 to 1.20; and z2 is −0.80 to 0.80.) It is characterized in that it is a perovskite-type oxide material represented by 7 ) proton conducting ceramic cell.

[0029] In addition, the present invention ( 9 ) is characterized in that the electrolyte contains the proton-conductive material (2) and has a first portion containing Me (Me is at least one of Ti, Mn, Fe, Co, Ni, and Cu) and a second portion having a different Me content from the first portion. 7 ) or ( 8 ) proton conducting ceramic cell.

[0030] In addition, the present invention ( 10 ) is characterized in that the electrolyte has a first layer containing Me in a range of 0.0 mass % or more and less than 2.0 mass %, and a second layer laminated on the first layer and containing Me in a range of 2.0 mass % to 20.0 mass %. 9 ) proton conducting ceramic cell.

[0031] In addition, the present invention ( 11 ) is characterized in that the electron conductive material is an electron conductive material for an air electrode, and the air electrode is an electrode for the proton conductive ceramic cell. 7 )~( 10 ) a proton-conducting ceramic cell.

[0032] In addition, the present invention ( 12) is characterized in that the electron conductive material is an electron conductive material for a fuel electrode, and the fuel electrode is an electrode for a proton conductive ceramic cell. 7 )~( 11 ) a proton-conducting ceramic cell.

[0033] The present invention (13) is characterized in that an intermediate layer is provided between the electrolyte and the air electrode ( 7 )~( 12 ) a proton-conducting ceramic cell.

[0034] In addition, the present invention ( 14 ) is characterized by having an intermediate layer between the electrolyte and the fuel electrode ( 7 )~( 13 ) a proton-conducting ceramic cell.

[0037] In this specification, when a numerical range is indicated using "to", the numerical range includes both ends of the range. [Effects of the Invention]

[0038] According to the present invention, it is possible to provide an electrode for a proton-conductive ceramic cell having low electrode resistance and high current density, a proton-conductive ceramic cell using the same, and a method for producing the same. [Brief explanation of the drawings]

[0039] [Figure 1] 1 is a schematic cross-sectional view of an example of an electrode for a proton-conductive ceramic cell according to the present invention. [Figure 2] 1 is an SEM image of a cross section of the electrode of Example 1. [Figure 3] 1 is an SEM image of a cross section of the electrode of Comparative Example 1. [Figure 4] 1 shows the image processing results of the porosity measurement in Example 1. [Figure 5] 1 shows the image processing results of the porosity measurement in Comparative Example 1. [Figure 6]1 is a graph showing the evaluation results of the output characteristics of the electrodes of Example 1, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0040] FIG. 1 is a schematic cross-sectional view of an example of the proton-conducting ceramic cell electrode of the present invention. In FIG. 1, the proton-conducting ceramic cell electrode 1 is formed on an electrolyte 2. The proton-conducting ceramic cell electrode 1 is formed of at least an electron-conducting material 3 and a proton-conducting material (1) 4, and the mass ratio of the electron-conducting material 1 to the proton-conducting material (1) 4 is 100:0 to 20:80. The proton-conducting ceramic cell electrode 1 has pores, and the porosity is 20.0% by volume or less. The film thickness of the proton-conducting ceramic cell electrode 1 is 7.0 μm or less. Although FIG. 1 shows that the proton-conducting ceramic cell electrode 1 is formed of the electron-conducting material 3 and the proton-conducting material (1) 4, in the present invention, the proton-conducting ceramic cell electrode 1 may be formed of at least the electron-conducting material and may not contain the proton-conducting material (1).

[0041] In FIG. 1, when the electrode is a cathode, the electronically conductive material 3 is an electronically conductive material for the cathode, whereas when the electrode is an anode, the electronically conductive material 3 is an electronically conductive material for the anode.

[0042] As shown in FIG. 1, an electrode 1 for a proton-conductive ceramic cell is formed on an electrolyte 2 made of a proton-conductive material (2). The electrolyte 2 has a dense layer to prevent gas cross-leakage. The entire electrolyte 2 may be dense. The relative density of the dense layer of the electrolyte 2 is 90 to 100% by volume. The thickness of the dense layer of the electrolyte 2 is 0.1 μm to 1 mm. In order to make the electrolyte 2 thin while preventing gas cross-leakage, it is desirable that the entire electrolyte 2 be dense.

[0043] The electrode for a proton-conductive ceramic cell of the present invention is an electrode for a proton-conductive ceramic cell, It is formed of at least an electron conductive material, or an electron conductive material and a proton conductive material containing Ba (1), the mass ratio of the electron conductive material to the proton conductive material (1) is 100:0 to 20:80; The electrode has a film thickness of 7.0 μm or less, the porosity of the electrode is 20.0% by volume or less; The electrode for a proton-conducting ceramic cell is characterized by the above.

[0044] The electrode for a proton-conductive ceramic cell of the present invention is an electrode for a proton-conductive ceramic cell that uses an electrolyte formed from at least a proton-conductive material (2) described below.

[0045] The electrode for a proton-conductive ceramic cell of the present invention is formed from at least an electron-conductive material, or from at least an electron-conductive material and a proton-conductive material (1) containing Ba. In the electrode for a proton-conductive ceramic cell, the electrode is formed by sintering the electron-conductive material, or by sintering the electron-conductive material and a proton-conductive material (1) containing Ba.

[0046] The proton-conducting material refers to a material that has the property of conducting ions that are oxidized or reduced at the air electrode. The proton-conducting material (1) is a proton-conducting material containing Ba, and is a proton-conducting oxide. The Ba content in the proton-conducting material (1) is preferably 30 to 50 mass %, particularly preferably 35 to 45 mass %, calculated as an atom. The proton-conducting material (1) may be one type or a combination of two or more types.

[0047] The proton conductive material (1) is preferably an oxide material that is an ABO type perovskite oxide and contains Ba at the A site.

[0048] The proton conductive material (1) is a compound represented by the following general formula (1): (Ba α1 A1(1-α1) ) x1 B1 y1 O 3+z1 (1) Particularly preferred is a perovskite oxide material represented by the following general formula (1): The perovskite oxide material represented by the general formula (1) is an oxide material having at least Ba at the A site of the perovskite oxide.

[0049] In general formula (1), A1 is at least one of Ca, Sr, and La, and B1 is at least one of Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu. α1 is 0.20 to 1.00, preferably 0.60 to 1.00. x1 is 0.80 to 1.20, preferably 0.90 to 1.10. y1 is 0.80 to 1.20, preferably 0.90 to 1.10. z1 is -0.80 to 0.80, preferably -0.40 to 0.40.

[0050] Examples of the proton-conducting material (1) include barium zirconate, barium cerate, barium zirconate cerate, barium strontium zirconate, barium strontium cerate, and barium strontium zirconate cerate.

[0051] The electronically conductive material is an electronically conductive material for the air electrode when the electrode is a cathode, and is an electronically conductive material for the anode when the electrode is anode.

[0052] An electron-conductive material for an air electrode refers to a material that can be used in a high-temperature oxidizing atmosphere, has catalytic activity for the oxidation or reduction reaction of the gas on the air electrode side, and has the property of conducting electrons. The electron-conductive oxide for an air electrode may be a single material or a combination of two or more materials.

[0053] The electron conductive material for the air electrode is not particularly limited, and examples thereof include oxides such as (LaBa)MnO3, (LaBa)FeO3, (LaBa)CoO3, and (LaBa)(CoFe)O3.

[0054] The electron conductive material for the air electrode may be a material represented by the following general formula (4): A4 (1-x4) B4 x4 C y4 O 3-z4 (4) A perovskite oxide material represented by the following formula is preferred.

[0055] In general formula (4), A4 is one or more of Y, La, Ce, Pr, Sm, and Gd, preferably one or more of La, Sm, and Gd. B4 is one or more of Sr, Ca, and Ba, preferably Sr. C is one or more of Cr, Mn, Fe, Co, Ni, and Cu, preferably one or more of Mn, Fe, and Co. x4 is 0.20 to 0.60, preferably 0.25 to 0.50, and particularly preferably 0.30 to 0.50. y4 is 0.95 to 1.15, preferably 1.00 to 1.10, and particularly preferably 1.00 to 1.05. z4 is -1.00 to 1.00, preferably -0.50 to 0.50, and particularly preferably -0.30 to 0.30.

[0056] The electron-conductive material for the anode refers to a material that can be used in a high-temperature reducing atmosphere, has catalytic activity for the oxidation or reduction reaction of the anode-side gas, and has the property of conducting electrons. The electron-conductive oxide for the anode may be a single material or a combination of two or more materials.

[0057] The electron conductive material for the fuel electrode is not particularly limited, and examples thereof include iron oxide, nickel oxide, copper oxide, etc., and among these, nickel oxide is preferred.

[0058] The electrode for a proton-conductive ceramic cell of the present invention is a porous body containing at least an electron-conductive material. The electrode for a proton-conductive ceramic cell of the present invention is formed at least from an electron-conductive material, or from at least an electron-conductive material and a proton-conductive material (1) containing Ba. The mass ratio of the electron-conductive material to the proton-conductive material (1) in the electrode (electron-conductive material:proton-conductive material (1)) is 100:0 to 20:80, preferably 80:20 to 30:70, and particularly preferably 60:40 to 40:60. When the mass ratio of the electron-conductive material to the proton-conductive material (1) in the electrode is within the above range, the number of contact points between the electron-conductive material and the proton-conductive material (1) increases, thereby expanding the reaction field, reducing the electrode resistance and increasing the current density.

[0059] The amount of other material components other than the electron conductive material and the proton conductive material (1) contained in the electrode for a proton conductive ceramic cell of the present invention is in the range of 0.0 to 20.0 parts by mass when the combined mass of the electron conductive material and the proton conductive material (1) is taken as 100.0 parts by mass.

[0060] In the electrode for proton-conductive ceramic cells of the present invention, the average particle size of the primary particles of the electron-conductive material and the proton-conductive material (1) is 1 nm to 1.0 μm, preferably 5 nm to 0.5 μm, and particularly preferably 10 nm to 0.2 μm. When the average particle size of the primary particles of the electron-conductive material and the proton-conductive material (1) in the electrode is within the above range, the number of contact points between the electron-conductive material and the proton-conductive material (1) increases and the specific surface area within the electrode increases, thereby expanding the reaction field, reducing the electrode resistance and increasing the current density.

[0061] In the present invention, the average particle size of the primary particles is calculated by X-ray diffraction (for example, SmartLab manufactured by Rigaku) ​​and Scherrer's equation (Scherrer constant: 0.9).

[0062] The electrode for a proton-conducting ceramic cell of the present invention has a film thickness of 7.0 μm or less, preferably 0.1 to 6.0 μm, and particularly preferably 0.1 to 5.0 μm. When the electrode film thickness is within the above range, gas diffusion resistance, which is part of the electrode resistance, is reduced, resulting in lower electrode resistance and higher current density. Regarding the lower limit of the electrode film thickness, the thinner the better in order to reduce gas diffusion resistance, but a minimum film thickness of 0.1 μm is required to prevent an increase in reaction resistance due to a shortage of electrode material that serves as a catalyst.

[0063] The porosity of the electrode for a proton-conducting ceramic cell of the present invention is 20.0% by volume or less, preferably 0.0 to 19.0% by volume, and particularly preferably 0.0 to 18.0% by volume. When the porosity of the electrode is within the above range, the contact area with the electrolyte and the reaction field within the electrode are expanded, thereby reducing the electrode resistance and increasing the current density. Note that when the electrode thickness is 7.0 μm or less, the electrode resistance is dominated by the electrode reaction resistance, so the lower the porosity related to the gas diffusion resistance, the better.

[0064] In the electrode for a proton conducting ceramic cell of the present invention, when the electrode thickness is 0.1 μm≦electrode thickness<2.0 μm, preferably 0.5 μm≦electrode thickness≦1.0 μm, the electrode porosity is 0.0 to 20.0 volume %, more preferably 0.0 to 19.0 volume %, and particularly preferably 0.0 to 18.0 volume %, thereby further reducing the electrode resistance and increasing the current density.

[0065] In the electrode for a proton conducting ceramic cell of the present invention, when the electrode thickness is 2.0 μm≦electrode thickness≦7.0 μm, preferably 3.0 μm≦electrode thickness≦5.0 μm, the electrode porosity is 0.0 to 20.0 volume %, more preferably 0.0 to 19.0 volume %, and particularly preferably 0.0 to 18.0 volume %, thereby further reducing the electrode resistance and increasing the current density.

[0066] The conductivity of the electrode for a proton-conductive ceramic cell of the present invention is preferably 1 to 2000 S / cm 2 , more preferably 10 to 2000 S / cm2 , particularly preferably 100 to 2000 S / cm 2 In the electrode for a proton-conductive ceramic cell of the present invention, the conductivity of the electrode is an index showing the degree of sintering of the electron-conductive material and the proton-conductive material (1) in the electrode, and a higher conductivity indicates a higher degree of sintering of the electron-conductive material and the proton-conductive material (1) and a larger bonding area between the particles.

[0067] The method for producing an electrode for a proton-conductive ceramic cell of the present invention includes a step of preparing a nitrate-containing electrode material precursor, which contains at least a metal element of an electron-conductive material source, or a metal element of an electron-conductive material source and a metal element of a proton-conductive material (1) source, and in which at least a part of the metal element is present as a nitrate; a step of preparing a slurry for forming an electrode by mixing and dispersing the nitrate-containing electrode material precursor in a solvent to obtain a slurry for forming an electrode; an electrode coating film forming step of applying the electrode-forming slurry to an object to be coated and then drying the slurry to obtain a nitrate-containing electrode material precursor coating film; a pressing step of pressing the nitrate-containing electrode material precursor coating film at 10 to 500 MPa by cold isostatic pressing to obtain a pressurized product of the nitrate-containing electrode material precursor coating film; a firing step of firing the pressure-treated nitrate-containing electrode material precursor coating at 700 to 1200°C to obtain an electrode for a proton-conductive ceramic cell; The present invention relates to a method for producing an electrode for a proton-conducting ceramic cell, comprising the steps of:

[0068] The method for producing an electrode for a proton-conductive ceramic cell of the present invention comprises a step of preparing a nitrate-containing electrode material precursor, a step of preparing an electrode-forming slurry, a step of forming an electrode coating film, a step of pressing, and a step of firing.

[0069] The nitrate-containing electrode material precursor preparation step is a step of preparing a nitrate-containing electrode material precursor that contains at least metal elements of an electron conductive material source, at least a part of which metal elements are present as nitrates, or a nitrate-containing electrode material precursor that contains at least metal elements of an electron conductive material source and metal elements of a proton conductive material (1) source, at least a part of which metal elements are present as nitrates.

[0070] In the nitrate-containing electrode material precursor, the metal element of the electron conductive material source and / or the metal element of the proton conductive material (1) source exists in any one or more states of a nitrate of the metal element, an amorphous metal oxide, and a crystalline metal oxide. That is, the nitrate-containing electrode material precursor contains any one or more states of a nitrate of the metal element of the electron conductive material source, an amorphous oxide of the metal element of the electron conductive material source, a crystalline oxide of the metal element of the electron conductive material source, a nitrate of the metal element of the proton conductive material (1) source, an amorphous oxide of the metal element of the proton conductive material (1) source, and a crystalline oxide of the metal element of the proton conductive material (1) source.

[0071] The nitrate-containing electrode material precursor contains nitrates of at least some of the metal elements of the electron conductive material source and / or the metal elements of the proton conductive material (1) source. That is, the nitrate-containing electrode material precursor contains at least nitrates.

[0072] The nitrate-containing electrode material precursor preparation step is not particularly limited as long as it is a step that can obtain a nitrate-containing electrode material precursor, but the spray pyrolysis step described below is preferred.

[0073] The spray pyrolysis step is a step of atomizing an aqueous solution for spraying containing metal ions of an electron conductive material source and nitrate ions, or an aqueous solution for spraying containing metal ions of an electron conductive material source, metal ions of a proton conductive material (1) source, and nitrate ions, and then spray pyrolyzing the atomized aqueous solution for spraying to obtain a nitrate-containing electrode material precursor.

[0074] The aqueous solution for spraying contains at least metal ions of a source of an electron conductive material and nitrate ions, or at least metal ions of a source of an electron conductive material, metal ions of a source of a proton conductive material (1), and nitrate ions.

[0075] Ba ions are essential as metal ions for the source of proton-conductive material (1), and other metal ions are not particularly limited as long as they provide the proton-conductive material (1), and are appropriately selected depending on the type of proton-conductive material (1) to be obtained. Examples of metal ions for the source of proton-conductive material (1) include ions of Ba, Ca, Sr, La, Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu.

[0076] The metal ions for the source of the electron conductive material for the air electrode are not particularly limited as long as they provide an electron conductive material for the air electrode, and are appropriately selected depending on the type of electron conductive material to be obtained. Examples of metal ions for the source of the electron conductive material for the air electrode include ions of Y, La, Ce, Pr, Sm, Gd, Sr, Ca, Ba, Cr, Mn, Fe, Co, Ni, and Cu.

[0077] The metal ions of the source of the electron conductive material for the anode are not particularly limited as long as they provide an electron conductive material for the anode, and are appropriately selected depending on the type of electron conductive material to be obtained. Examples of metal ions of the source of the electron conductive material for the anode include ions of Ni, Cu, Fe, etc.

[0078] The contents of the metal ions of the electron conductive material source and the metal ions of the proton conductive material (1) source in the aqueous solution for spraying are appropriately selected depending on the compositions of the electron conductive material and the proton conductive material (1) of the electrode for a proton conductive ceramic cell to be obtained.

[0079] The aqueous solution for spraying contains nitrate ions. The nitrate ions in the aqueous solution for spraying may be present as counter anions for all or part of the metal ions of the source of the electron conductive material and / or the source of the proton conductive material (1). By containing nitrate ions in the aqueous solution for spraying, the degree of sintering of the oxide powder material for an electrode, i.e., the electron conductive material, or the electron conductive material and the proton conductive material (1), is increased in the firing step.

[0080] The aqueous solution for spraying is prepared, for example, by dissolving a metal salt of the source of the electron conductive material, or a metal salt of the source of the electron conductive material and a metal salt of the source of the proton conductive material (1), and a nitrate ion source in an aqueous solvent. All or part of the metal salt of the source of the electron conductive material and / or the metal salt of the source of the proton conductive material (1) may be nitrate salts that serve as the source of nitrate ions.

[0081] In the spray pyrolysis step, the spray aqueous solution is atomized, and then the atomized spray aqueous solution is spray pyrolyzed to pyrolyze and / or oxidize the components in the spray aqueous solution, thereby obtaining a nitrate-containing electrode material precursor. Examples of methods for atomizing the spray aqueous solution include atomization using ultrasonic vibrations (e.g., vibrations with a frequency of 1.0 to 3 MHz, preferably 1.5 to 2.0 MHz). Examples of methods for spray pyrolyzing the atomized spray aqueous solution include introducing droplets of the atomized spray aqueous solution along with a carrier gas into a heating furnace, where water is evaporated and removed from the droplets of the spray aqueous solution, and the components in the droplets are pyrolyzed and / or oxidized to obtain a nitrate-containing electrode material precursor. The pyrolysis temperature during spray pyrolysis is appropriately selected and is, for example, 200 to 1000°C. The heating furnace for spray pyrolysis may be a single-stage heating furnace or a multi-stage heating furnace with two or more stages. The atmosphere for spray pyrolysis is an oxidizing atmosphere such as an oxygen-containing gas or air.

[0082] Other examples of the nitrate-containing electrode material precursor preparation process include a nitrate-containing electrode material precursor precipitation process in which citric acid is mixed and dissolved in a raw material mixed aqueous solution containing metal ions of an electron conductive material source and nitrate ions, or a raw material mixed aqueous solution containing metal ions of an electron conductive material source, metal ions of a proton conductive material (1) source, and nitrate ions, in an amount that is in excess of the molar amount of all metal ions, preferably 2.0 to 4.0 times, and particularly preferably 2.5 to 3.5 times the molar amount of all metal ions, and then heated at 250 to 400°C, preferably 275 to 350°C, to evaporate, dry, and denitrate the resulting solution, and if necessary, heat-treat the remaining nitrate-containing electrode material precursor at a predetermined temperature below the denitration temperature to obtain the nitrate-containing electrode material precursor.

[0083] The electrode-forming slurry preparation step is a step of mixing and dispersing a nitrate-containing electrode material precursor in a solvent to obtain an electrode-forming slurry.

[0084] In the electrode-forming slurry preparation step, the nitrate-containing electrode material precursor obtained in the spray pyrolysis step is added to a solvent such as water, ethanol, isopropanol, acetone, toluene, butanol, or terpineol, and the mixture is kneaded and mixed using a ball mill, kneader, stirrer, defoamer, or the like to prepare an electrode-forming slurry.

[0085] The solid content of the electrode-forming slurry is not particularly limited, but is preferably 25 to 75 mass %. The electrode-forming slurry may contain additives such as a binder, a dispersant, a plasticizer, and an antifoaming agent, as needed.

[0086] The electrode coating film forming step is a step in which the electrode-forming slurry is applied to an object to be coated, and then dried to obtain a nitrate-containing electrode material precursor coating film.

[0087] Examples of methods for applying the electrode-forming slurry to the application target include screen printing, spin coating, tape casting, hot pressing, and gravure printing.

[0088] The object to which the electrode-forming slurry is applied is, for example, an object on which an electrode is to be formed in the manufacturing process of a proton-conductive ceramic cell, such as an electrolyte, an intermediate layer, or a support for a proton-conductive ceramic cell.

[0089] The thickness of the coating film of the electrode-forming slurry is appropriately selected so that the thickness of the electrode for a proton-conductive ceramic cell obtained after the application of the electrode-forming slurry and the subsequent drying, pressing and firing steps is 7.0 μm or less, preferably 0.5 to 5.0 μm, and particularly preferably 1.0 to 3.0 μm.

[0090] In the electrode coating film forming process, after the electrode-forming slurry is applied to the coating object, the formed coating film of the electrode-forming slurry is dried, preferably by heating at 70 to 170°C, to remove the solvent in the electrode-forming slurry, and a nitrate-containing electrode material precursor coating film is formed on the coating object.

[0091] The pressing step is a step in which the nitrate-containing electrode material precursor coating film formed on the coating object is pressed at 10 to 500 MPa by cold isostatic pressing (CIP) to obtain a pressurized product of the nitrate-containing electrode material precursor coating film.

[0092] Cold isostatic pressing (CIP) is a method in which a sample is sealed in a molding mold with low deformation resistance and hydraulic pressure is applied to the sample surface, thereby applying a uniform pressure equivalent to the hydraulic pressure. Examples of cold isostatic pressing devices used in CIP include the ECIP series manufactured by ENERGYN and the CL series manufactured by Nikkiso Co., Ltd.

[0093] In the pressurizing step, the nitrate-containing electrode material precursor coating film formed on the coating object is pressed by cold isostatic pressing, thereby uniformly compressing the nitrate-containing electrode material precursor coating film and uniformly pressing the nitrate-containing electrode material precursor coating film against the coating object.

[0094] The pressure applied by cold isostatic pressing in the pressing step is 10 to 500 MPa, preferably 100 to 300 MPa. When the pressure applied by cold isostatic pressing is within the above range, the sinterability of the oxide powder material for an electrode is increased, resulting in lower electrode resistance and higher current density. The pressing time by cold isostatic pressing in the pressing step is appropriately selected. The temperature during pressing is about room temperature.

[0095] In the pressurizing step, the nitrate-containing electrode material precursor coating film formed on the coating object is introduced into a cold isostatic pressing device together with the coating object, and the nitrate-containing electrode material precursor coating film together with the coating object is cold isostatically pressed in the cold isostatic pressing device.

[0096] The firing step is a step in which the pressure-treated nitrate-containing electrode material precursor coating is fired at 700 to 1200°C to convert the nitrate-containing electrode material precursor into a crystalline oxide and sinter the electrode oxide powder material, thereby obtaining an electrode for a proton-conductive ceramic cell.

[0097] In the firing step, the firing temperature of the pressure-treated nitrate-containing electrode material precursor coating film is 700 to 1200°C, preferably 800 to 1000°C. The firing time of the pressure-treated nitrate-containing electrode material precursor coating film is appropriately selected. The firing atmosphere of the pressure-treated nitrate-containing electrode material precursor coating film is air.

[0098] In this manner, the electrode for a proton-conductive ceramic cell of the present invention can be produced by carrying out the method for producing the electrode for a proton-conductive ceramic cell of the present invention.

[0099] The electrode for a proton-conductive ceramic cell of the present invention includes a nitrate-containing electrode material precursor preparation step of preparing a nitrate-containing electrode material precursor containing at least a metal element of an electron-conductive material source, or a metal element of an electron-conductive material source and a metal element of a proton-conductive material (1) source, wherein at least a part of the metal element is present as a nitrate; a step of preparing a slurry for forming an electrode by mixing and dispersing the nitrate-containing electrode material precursor in a solvent to obtain a slurry for forming an electrode; an electrode coating film forming step of applying the electrode-forming slurry to an object to be coated and then drying the slurry to obtain a nitrate-containing electrode material precursor coating film; a pressing step of pressing the nitrate-containing electrode material precursor coating film at 10 to 500 MPa by cold isostatic pressing to obtain a pressurized product of the nitrate-containing electrode material precursor coating film; a firing step of firing the pressure-treated nitrate-containing electrode material precursor coating at 700 to 1200°C to obtain an electrode for a proton-conductive ceramic cell; The electrode for a proton-conducting ceramic cell is obtained by carrying out the steps described above. The nitrate-containing electrode material precursor preparation step, spray pyrolysis step, electrode-forming slurry preparation step, electrode coating film formation step, pressurizing step, and firing step in the electrode for a proton-conductive ceramic cell of the present invention are the same as the nitrate-containing electrode material precursor preparation step, spray pyrolysis step, electrode-forming slurry preparation step, electrode coating film formation step, pressurizing step, and firing step in the method for producing an electrode for a proton-conductive ceramic cell of the present invention.

[0100] The proton-conducting ceramic cell of the present invention comprises: an electrolyte formed of at least a proton-conductive material (2); an air electrode; a fuel electrode; and one or both of the air electrode and the fuel electrode is the electrode for a proton-conducting ceramic cell of the present invention; The proton-conducting ceramic cell is characterized by the above.

[0101] The proton-conducting ceramic cell of the present invention comprises an electrolyte formed of at least a proton-conducting material (2), an air electrode, and a fuel electrode. The proton-conducting ceramic cell of the present invention may also comprise an intermediate layer containing a proton-conducting material (3) between the electrolyte formed of at least the proton-conducting material (2) and the air electrode. The proton-conducting ceramic cell of the present invention may also comprise an intermediate layer containing a proton-conducting material (3) between the electrolyte formed of at least the proton-conducting material (2) and the fuel electrode.

[0102] At least one of the electrodes in the proton-conducting ceramic cell of the present invention is the electrode for the proton-conducting ceramic cell of the present invention. That is, in the proton-conducting ceramic cell of the present invention, either one or both of the air electrode and the fuel electrode is the electrode for the proton-conducting ceramic cell of the present invention. The electrode in the proton-conducting ceramic cell of the present invention is formed on an electrolyte formed of at least the proton-conducting material (2) or on an intermediate layer containing the proton-conducting material (3).

[0103] The electrolyte in the proton-conducting ceramic cell of the present invention is formed from at least the proton-conducting material 2. That is, the electrolyte contains at least the proton-conducting material 2.

[0104] The proton-conducting material (2) is not particularly limited as long as it is a proton-conducting oxide having the property of conducting ions oxidized or reduced at the air electrode. The proton-conducting material (2) is preferably a proton-conducting material containing Ba. When the proton-conducting material (2) contains Ba, the Ba content in the proton-conducting material (2) is preferably 30 to 50 mass %, particularly preferably 35 to 45 mass %, calculated as an atom. The proton-conducting material (2) may be one type or a combination of two or more types.

[0105] The proton conductive material (2) is preferably an ABO type perovskite oxide containing Ba at the A site.

[0106] The proton conductive material (2) may be a compound represented by the following general formula (2): (Ba α2 A2 (1-α2) ) x2 B1 y2 O 3+z2 (2) Particularly preferred is a perovskite oxide material represented by the following general formula (2): The perovskite oxide material represented by the general formula (2) is an oxide material having at least Ba at the A site of the perovskite oxide.

[0107] In general formula (2), A2 is at least one of Ca, Sr, and La, and B2 is at least one of Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu. α2 is 0.20 to 1.00, preferably 0.60 to 1.00. x2 is 0.80 to 1.20, preferably 0.90 to 1.10. y2 is 0.80 to 1.20, preferably 0.90 to 1.10. z2 is -0.80 to 0.80, preferably -0.40 to 0.40.

[0108] Examples of the proton-conducting material (2) include barium zirconate, barium cerate, barium zirconate cerate, barium strontium zirconate, barium strontium cerate, and barium strontium zirconate cerate.

[0109] The electrolyte is generally a dense body to prevent gas leakage. The relative density of the electrolyte is 90 to 100% by volume, more preferably 97 to 100% by volume, and particularly preferably 98 to 100% by volume. When the porosity of the electrolyte is within the above range, the gas cross leakage prevention function can be enhanced. Furthermore, the thickness of the electrolyte is preferably 0.5 to 30.0 μm, more preferably 1.0 to 15.0 μm, and particularly preferably 1.5 to 10.0 μm. When the thickness of the electrolyte is within the above range, the resistance of the dense body layer of the electrolyte can be reduced while maintaining the gas cross leakage prevention function. In order to make the electrolyte thin while preventing gas cross leakage, it is desirable that the entire electrolyte be a dense body.

[0110] The electrolyte is formed by preparing an electrolyte-forming slurry in which at least a powdery proton-conductive material (2) is dispersed, then applying the electrolyte-forming slurry to an object on which the electrolyte is to be formed by screen printing or the like to form an electrolyte-forming slurry coating, and then drying and sintering the coating by firing at a firing temperature, for example, 1200 to 1600°C.

[0111] The electrolyte may be an electrolyte (A) containing a proton-conductive material (2) and having a first portion containing Me (Me is at least one of Ti, Mn, Fe, Co, Ni, and Cu) and a second portion having a different Me content from the first portion. The first portion having a low Me content is a portion where no or very little electron leakage occurs, and functions as an electron leakage prevention layer to suppress electron leakage. Furthermore, the second portion having a high Me content is highly dense due to the sintering-promoting effect of Me during the firing process during production, and therefore is a portion where no or very little gas cross leakage occurs, and functions as a gas cross leakage prevention layer to suppress gas cross leakage.

[0112] An example of the electrolyte (A) is an electrolyte (A1) having a first layer containing Me in the range of 0.0 mass % or more but less than 2.0 mass % and a second layer laminated on the first layer and containing Me in the range of 2.0 mass % to 20.0 mass %. In the electrolyte (A1), the first layer with a low Me content is a layer in which no or very little electron leakage occurs, and functions as an electron leakage prevention layer to suppress electron leakage. Furthermore, the second layer with a high Me content is highly dense due to the sintering-promoting effect of Me during the firing process during production, and therefore is a layer in which no or very little gas cross leakage occurs, and functions as a gas cross leakage prevention layer to suppress gas cross leakage.

[0113] The electrolyte (A1) is formed by preparing a first layer-forming slurry in which at least a powdered proton-conducting material (2) and a predetermined amount of Me are dispersed; then, the first layer-forming slurry is applied to an object on which the first layer is to be formed by screen printing or the like to form a first layer-forming slurry coating; then, after drying, the slurry is fired and sintered at a firing temperature, for example, 1200 to 1600°C to form the first layer; then, a second layer-forming slurry in which at least a powdered proton-conducting material (2) and a predetermined amount of Me are dispersed; then, the second layer-forming slurry is applied to the first layer by screen printing or the like to form a second layer-forming slurry coating; then, after drying, the slurry is fired and sintered at a firing temperature, for example, 1000 to 1400°C to form the second layer.

[0114] The electrolyte (A) may be an electrolyte (A2) having a gradation of Me content in the film thickness direction within a single electrolyte layer, where a first portion has a relatively low Me content and a second portion has a relatively high Me content within the single electrolyte layer.

[0115] The electrolyte (A2) is formed by preparing an electrolyte-forming slurry in which at least a powdery proton-conductive material (2) is dispersed, then applying the electrolyte-forming slurry to a fuel electrode formed of an oxide containing Me by screen printing or the like to form an electrolyte-forming slurry coating, and then drying and then firing at a firing temperature, for example, 1200 to 1600°C to sinter the electrolyte and diffuse the Me element of the fuel electrode into the electrolyte.

[0116] In the proton-conducting ceramic cell of the present invention, an intermediate layer may be formed between the electrolyte and the air electrode, or an intermediate layer may be formed between the electrolyte and the fuel electrode.

[0117] The intermediate layer in the proton-conductive ceramic cell of the present invention contains a proton-conductive material (3).

[0118] The proton-conducting material (3) is not particularly limited as long as it is a proton-conducting oxide having the property of conducting ions oxidized or reduced at the air electrode. The proton-conducting material (3) is preferably a proton-conducting material containing Ba. When the proton-conducting material (3) contains Ba, the Ba content in the proton-conducting material (3) is preferably 30 to 50 mass %, particularly preferably 35 to 45 mass %, calculated as an atom. The proton-conducting material (3) may be one type or a combination of two or more types.

[0119] The proton conductive material (3) is preferably an ABO type perovskite oxide containing Ba at the A site.

[0120] The proton conductive material (3) is a compound represented by the following general formula (3): (Ba α3 A3 (1-α3) ) x3 B1 y3 O 3+z3 (3) Particularly preferred is a perovskite oxide material represented by the following general formula (3): The perovskite oxide material represented by the general formula (3) is an oxide material having at least Ba at the A site of the perovskite oxide.

[0121] In general formula (3), A3 is at least one of Ca, Sr, and La, and B3 is at least one of Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu. α3 is 0.20 to 1.00, preferably 0.60 to 1.00. x3 is 0.80 to 1.20, preferably 0.90 to 1.10. y3 is 0.80 to 1.20, preferably 0.90 to 1.10. z3 is -0.80 to 0.80, preferably -0.40 to 0.40.

[0122] Examples of the proton-conducting material (3) include barium zirconate, barium cerate, barium zirconate cerate, barium strontium zirconate, barium strontium cerate, and barium strontium zirconate cerate.

[0123] The intermediate layer contains a proton conductive material (3), but may contain an electron conductive material, an oxide ion conductive material, etc. in addition to the proton conductive material (3) depending on the function of the intermediate layer.

[0124] The intermediate layer is provided for various purposes, such as preventing gas leakage, suppressing electron leakage, reducing the reaction resistance of the air electrode, and improving the adhesive strength of the interface.

[0125] The intermediate layer may be either dense or porous, but preferably has a high relative density to reduce the resistance of the intermediate layer. Specifically, the relative density of the intermediate layer is preferably 40 to 100% by volume, more preferably 55 to 100% by volume, and particularly preferably 70 to 100% by volume.

[0126] The intermediate layer is formed by preparing an intermediate layer-forming slurry in which at least a powdery proton-conductive material (3) is dispersed, then applying the intermediate layer-forming slurry to an object on which the intermediate layer is to be formed by screen printing or the like to form an intermediate layer-forming slurry coating, and then drying and sintering the coating by firing at a firing temperature, for example, 1000 to 1400°C.

[0127] The proton-conducting ceramic cell of the present invention includes a proton-conducting ceramic cell in which the electron-conducting material is an electron-conducting material for an air electrode and the proton-conducting ceramic cell electrode is the air electrode. The electron-conducting material for the air electrode in the proton-conducting ceramic cell of the present invention is the same as the electron-conducting material for the air electrode in the proton-conducting ceramic cell electrode of the present invention.

[0128] The proton-conducting ceramic cell of the present invention includes a proton-conducting ceramic cell in which the electron-conducting material is an electron-conducting material for an anode and the electrode for a proton-conducting ceramic cell is the anode. The electron-conducting material for the anode in the proton-conducting ceramic cell of the present invention is the same as the electron-conducting material for the anode in the electrode for a proton-conducting ceramic cell of the present invention.

[0129] The air electrode (or fuel electrode) is formed by preparing an electrode-forming slurry in which at least a powdered electron-conductive material for the air electrode (or a powdered electron-conductive material for the fuel electrode) is dispersed, then applying the electrode-forming slurry to an object on which the electrode is to be formed to form an electrode-forming slurry coating, and then drying and sintering the coating by firing at a firing temperature, for example, 700 to 1200°C.

[0130] The proton-conducting ceramic cell of the present invention may be formed on a support. It is preferable that the support is porous, as this allows for good gas diffusion. The porosity of the porous support is, for example, 10 to 60% by volume. The shape of the porous support may be, but is not particularly limited to, a flat plate or a tube. Examples of materials for the support include oxides such as alumina or zirconia, or heat-resistant metals.

[0131] Examples of the proton-conducting ceramic cell of the present invention include the following. (i) A proton-conductive ceramic cell in which a fuel electrode (a fuel electrode corresponding to the electrode for a proton-conductive ceramic cell of the present invention or a fuel electrode other than the electrode for a proton-conductive ceramic cell of the present invention) / an electrolyte formed of the proton-conductive material (2) / an air electrode corresponding to the electrode for a proton-conductive ceramic cell of the present invention are stacked in this order. (ii) A proton-conducting ceramic cell in which a fuel electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention, an electrolyte formed of the proton-conducting material (2), and an air electrode (an air electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention or an air electrode other than the electrode for a proton-conducting ceramic cell of the present invention) are laminated in this order. (iii) A proton-conductive ceramic cell in which a fuel electrode (a fuel electrode corresponding to the electrode for a proton-conductive ceramic cell of the present invention or a fuel electrode other than the electrode for a proton-conductive ceramic cell of the present invention) / an intermediate layer containing the proton-conductive material (3) / an electrolyte formed of the proton-conductive material (2) / an air electrode corresponding to the electrode for a proton-conductive ceramic cell of the present invention are stacked in this order. (iv) A proton-conductive ceramic cell in which a fuel electrode (a fuel electrode corresponding to the electrode for a proton-conductive ceramic cell of the present invention or a fuel electrode other than the electrode for a proton-conductive ceramic cell of the present invention) / an electrolyte formed of the proton-conductive material (2) / an intermediate layer containing the proton-conductive material (3) / an air electrode corresponding to the electrode for a proton-conductive ceramic cell of the present invention are stacked in this order. (v) A proton-conducting ceramic cell in which a fuel electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention, an intermediate layer containing the proton-conducting material (3), an electrolyte formed of the proton-conducting material (2), and an air electrode (an air electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention or an air electrode other than the electrode for a proton-conducting ceramic cell of the present invention) are laminated in this order. (vi) A proton-conducting ceramic cell in which the following are stacked in this order: a fuel electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention; an electrolyte formed of the proton-conducting material (2); an intermediate layer containing the proton-conducting material (3); and an air electrode (an air electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention or an air electrode other than the electrode for a proton-conducting ceramic cell of the present invention). (vii) A proton-conducting ceramic cell in which a fuel electrode (a fuel electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention or a fuel electrode other than the electrode for a proton-conducting ceramic cell of the present invention) / an intermediate layer containing the proton-conducting material (3) / an electrolyte formed of the proton-conducting material (2) / an intermediate layer containing the proton-conducting material (3) / an air electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention are stacked in this order. (viii) A proton-conducting ceramic cell in which a fuel electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention, an intermediate layer containing the proton-conducting material (3), an electrolyte formed of the proton-conducting material (2), an intermediate layer containing the proton-conducting material (3), and an air electrode (an air electrode corresponding to the electrode for a proton-conducting ceramic cell of the present invention or an air electrode other than the electrode for a proton-conducting ceramic cell of the present invention) are laminated in this order. Moreover, examples of the proton-conducting ceramic cell of the present invention include an embodiment in which the above (i) to (viii) are formed on a support.

[0132] The proton-conducting ceramic cell of the present invention may have a porous layer on an electrode (air electrode or anode) having a porosity higher than that of the electrode. The porosity of the porous layer is higher than that of the electrode, preferably 25.0 to 55.0% by volume. As the material for the porous layer, the electron-conductive material for the air electrode includes perovskite-type oxide materials such as (LaBa)MnO3, (LaBa)FeO3, (LaBa)CoO3, and (LaBa)(CoFe)O3. In the electron-conductive materials, La can be substituted or partially substituted with other lanthanides (Pr, Sm, Gd), and Ba can be substituted or partially substituted with other alkaline earth metals (Ca, Sr). Furthermore, as the material for the porous layer, the electron-conductive material for the anode is a metal-based material (Ti, Mn, Fe, Co, Ni, Cu, etc.). Metal-based materials include those reduced by gases such as hydrogen, carbon monoxide, hydrocarbons, and biofuels. For example, if NiO (oxide) is used as a manufacturing material, when a solid oxide cell is constructed and operated with the above gas, NiO is reduced to Ni (metal). An example of a proton-conducting ceramic cell of the present invention having a porous layer includes an example in which a porous layer having a higher porosity than the electrode of any of the above proton-conducting ceramic cells (i) to (viii) is provided on the electrode of the proton-conducting ceramic cell.

[0133] The nitrate-containing electrode material precursor of the present invention is a nitrate-containing electrode material precursor, The catalyst contains at least a metal element of an electron conductive material source, or at least a metal element of an electron conductive material source and a metal element of a proton conductive material (1) source, and at least a part of the metal element is present as a nitrate; the mass ratio of the metal element of the electron conductive material to the metal element of the proton conductive material (1) in terms of oxide is 100:0 to 20:80; The nitrate-containing electrode material precursor is characterized by:

[0134] The nitrate-containing electrode material precursor of the present invention is a nitrate-containing electrode material precursor, and is oxidized or decomposed by calcining at 700 to 1200°C, preferably 800 to 1000°C, to convert it into an oxide powder material for an electrode, i.e., a crystalline oxide of a metal element of an electron conductive material, or a crystalline oxide of a metal element of an electron conductive material and a crystalline oxide of a metal element of a proton conductive material (1). The resulting oxide powder material for an electrode is then sintered to form an electrode for a proton conductive ceramic cell, which is formed at least of an electron conductive material, or at least of an electron conductive material and a proton conductive material (1) containing Ba.

[0135] The nitrate-containing electrode material precursor is a nitrate-containing electrode material precursor that contains at least a metal element of an electron conductive material source, at least a part of which is present as a nitrate, or a nitrate-containing electrode material precursor that contains at least a metal element of an electron conductive material source and a metal element of a proton conductive material (1) source, at least a part of which is present as a nitrate.

[0136] In the nitrate-containing electrode material precursor, the metal element of the electron conductive material source and / or the metal element of the proton conductive material (1) source exists in any one or more states of a nitrate of the metal element, an amorphous metal oxide, and a crystalline metal oxide. That is, the nitrate-containing electrode material precursor contains any one or more states of a metal element of the electron conductive material source, an amorphous oxide of the metal element of the electron conductive material source, a crystalline oxide of the metal element of the electron conductive material source, a metal element of the proton conductive material (1) source, an amorphous oxide of the metal element of the proton conductive material (1) source, and a crystalline oxide of the metal element of the proton conductive material (1) source.

[0137] The nitrate-containing electrode material precursor contains nitrates of at least some of the metal elements of the electron conductive material source and / or the metal elements of the proton conductive material (1) source. That is, the nitrate-containing electrode material precursor contains at least nitrates.

[0138] The metal element of the source of the proton conductive material (1) is Ba, at least one of Ca, Sr, and La, and at least one of Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu.

[0139] The metal element that serves as the electron conductive material for the air electrode is not particularly limited as long as it provides an electron conductive material for the air electrode, and may be appropriately selected depending on the type of electron conductive material to be obtained. Examples of metal elements that serve as electron conductive materials for the air electrode include ions of Y, La, Ce, Pr, Sm, Gd, Sr, Ca, Ba, Cr, Mn, Fe, Co, Ni, and Cu, with Ba being preferred.

[0140] The metal element that serves as the electron conductive material for the anode is not particularly limited as long as it provides an electron conductive material for the anode, and is appropriately selected depending on the type of electron conductive material to be obtained. Examples of metal elements that serve as electron conductive materials for the anode include ions of Ni, Cu, Fe, etc.

[0141] In the nitrate-containing electrode material precursor, the mass ratio of the metal element of the electron conductive material to the metal element of the proton conductive material (1) calculated as oxides is 100:0 to 20:80, preferably 80:20 to 30:70, particularly preferably 60:40 to 40:60. [Example]

[0142] Next, the present invention will be explained in more detail with reference to examples, but these are merely illustrative and do not limit the present invention.

[0143] Air electrodes with different thicknesses and porosities were fabricated according to the following procedure: The oxide powder material used as the raw material for the air electrodes was fabricated by spray pyrolysis.

[0144] <Synthesis of oxide powder materials by spray pyrolysis method> Spray pyrolysis is one of the methods for synthesizing nano-sized oxide powder materials. It is possible to synthesize a single oxide powder material, but it is also possible to synthesize an oxide powder material that is a composite of two or more oxides. In this case, a good dispersion state can be obtained for the composite of two or more oxides. Another feature is that the primary particle size can be controlled over a wide range. The synthesis of oxide powder materials by spray pyrolysis in the following examples is described.

[0145] The spray pyrolysis process involves preparing an aqueous solution for spraying containing a metal salt of a source of an electron-conductive material for an air electrode and a metal salt of a source of a proton-conductive material (1), atomizing the aqueous solution for spraying by ultrasonic vibration, and then introducing the atomized aqueous solution for spraying into a heating furnace to obtain an oxide powder material for an air electrode.

[0146] The composition ratio of the various metal elements constituting the primary particles of the electron conductive material for the air electrode and the primary particles of the proton conductive material (1) was adjusted by appropriately selecting the concentration ratio of each metal element contained in the aqueous solution to be sprayed.

[0147] The spray solution in the spraying device was atomized by ultrasonic vibration (1.75 MHz), and then the atomized solution was introduced into a heating furnace through a pipe connected to the spraying device. The metal salt of the source of the electron conductive material for the air electrode and the metal salt of the source of the proton conductive material (1) in the spraying solution were thermally decomposed and oxidized to obtain an oxide powder material for the air electrode. A four-stage electric furnace (furnace temperatures from the front stage: 300, 500, 700, and 900°C, heating times from the front stage: 8 seconds, 8 seconds, 8 seconds, and 8 seconds) was used as the heating furnace. <Preparation of aqueous solution for spraying> (1) Aqueous solution for spraying s1 Lanthanum nitrate hexahydrate (6.96 g), barium nitrate (8.87 g), cobalt nitrate hexahydrate (7.80 g), zirconium nitrate oxide dihydrate (5.58 g), and ytterbium nitrate pentahydrate (1.04 g) were weighed and dissolved in pure water. Then, pure water was added to make the total volume of the solution 1000 ml, to prepare aqueous solution s1 for spraying. 50 parts by mass of 0.05 mol of La per 1 L was obtained by spray pyrolysis of the aqueous solution s1 for spraying. 0.6 Ba 0.4 CoO3 (hereinafter referred to as LBC) - 50 parts by mass BaZr 0.9 Yb 0.1 O3 (hereinafter referred to as BZYb10) can be synthesized.

[0148] <Preparation of nitrate-containing electrode material precursor> (1) Nitrate-containing electrode material precursor p1 The sprayed aqueous solution s1 was used to carry out spray pyrolysis by ultrasonic spray pyrolysis to obtain a nitrate-containing electrode material precursor p1 of LBC-BZYb10.

[0149] X-ray diffraction analysis of the LBC-BZYb10 nitrate-containing electrode material precursor revealed diffraction peaks identifiable as LBC and BZYb, confirming that the powder material contained crystalline LBC and BZYb10. Additionally, diffraction peaks identifiable as barium nitrate were also observed, confirming that the material contained not only crystalline oxide but also nitrate.

[0150] <Fabrication of fuel electrode> NiO and BaZr 0.8 Yb 0.2 O3 (hereinafter referred to as BZYb20) and carbon were mixed in a mass ratio of 6:4:1, and a toluene-based solvent (Fujifilm Wako Pure Chemical Industries, Ltd., 204-01861), binder, plasticizer, and dispersant were added. The mixture was then mixed in a ball mill for 48 hours to obtain a slurry for the anode. The slurry for the anode was tape-cast to obtain a green sheet for the anode. The green sheets for the anode were stacked to a thickness of approximately 0.7 μm, and the thickness of the green sheet for the anode was adjusted by hot pressing. <Preparation of electrolyte> Toluene-based solvent, binder, plasticizer, and dispersant were added to BZYb20 and mixed in a ball mill for 48 hours to obtain electrolyte slurry. The electrolyte slurry was applied to the anode green sheet by spin coating at 3000 rpm. The anode and electrolyte were then co-sintered at 1475°C for 2 hours to obtain an integrated body of electrolyte and anode. The resulting electrolyte was densified by high-temperature co-sintering.

[0151] <Creating the air electrode> Ethyl cellulose, a plasticizer, a dispersant, and α-terpineol were added to the nitrate-containing electrode material precursor p1, and the mixture was kneaded in a kneader at room temperature for 1 minute and 30 seconds to obtain a slurry c1 for an air electrode.

[0152] Commercially available LBC powder (manufactured by Kusaka Rare Metals Laboratory) and BaZr 0.7 Ce 0.1 Y 0.1 Yb 0.1 O3 powder (hereafter referred to as BZCYYb, manufactured by DOWA Electronics) was mixed in a 5:5 mass ratio, and ethyl cellulose, plasticizer, dispersant, and α-terpineol were added. The mixture was kneaded in a kneader at room temperature for 1 minute and 30 seconds to obtain air electrode slurry c2. X-ray diffraction analysis of the mixture of commercially available LBC powder and BZCYYb powder revealed diffraction peaks identifiable as LBC and BZCYYb, confirming that the powder material contained crystalline LBC and BZCYYb. Furthermore, no diffraction peaks identifiable as metal nitrates such as barium nitrate were observed, confirming that the powder material did not contain nitrates.

[0153] <Fabrication of an Air Electrode as an Example> (1) Example 1 The air electrode slurry c1 was applied to the electrolyte surface of the integrated electrolyte and fuel electrode body by screen printing using a 5 μm mesh to a diameter of φ6 mm. After drying at 150°C for 30 minutes, the body was subjected to cold isostatic pressing (CIP) at 300 MPa to obtain a pressed electrode material precursor coating. The body was then fired at 900°C for 1 hour to obtain an air electrode. In this way, a proton-conducting ceramic cell having the air electrode of Example 1 was obtained.

[0154] <Fabrication of an Air Electrode as a Comparative Example> (1) Comparative Example 1 The cathode slurry c1 was applied to the electrolyte surface of the integrated electrolyte / anode body by screen printing using a 30 μm mesh to a diameter of φ6 mm. After drying at 150°C for 30 minutes, the resulting mixture was fired at 900°C for 1 hour to obtain an cathode. In this way, a proton-conducting ceramic cell having the cathode of Comparative Example 1 was obtained.

[0155] (2) Comparative Example 2 The cathode slurry c2 was applied to the electrolyte surface of the integrated electrolyte and anode body by screen printing using a 30 μm mesh to a diameter of φ6 mm. After drying at 150°C for 30 minutes, the cathode was obtained by firing at 900°C for 1 hour. In this way, a proton-conducting ceramic cell having the cathode of Comparative Example 2 was obtained.

[0156] <Measurement of electrode film thickness> The film thickness of the cathode in Example 1 was determined by observing the cross section of the cathode with a scanning electron microscope (SEM, JSM-5600, manufactured by JEOL Ltd.) or a field emission scanning electron microscope (FE-SEM, JSM-6330F, manufactured by JEOL Ltd.). The observation results are shown in Figure 2. The film thickness was also determined in the same manner for the air electrodes of Comparative Examples 1 and 2. The observation results for Comparative Example 1 are shown in FIG. As a result, the thickness of the air electrode in Example 1 was 4.7 μm, the thickness of the air electrode in Comparative Example 1 was 25.0 μm, and the thickness of the air electrode in Comparative Example 2 was 30.0 μm.

[0157] <Measurement of electrode porosity> The cross section of the cathode of Example 1 was smoothed using a cross-section polisher (Ar ion beam, IB-09020CP model, manufactured by JEOL Ltd.), and then observed with a FE-SEM (JSM-6330F, manufactured by JEOL Ltd.). The contrast of the SEM image was processed to obtain the porosity of the electrode. As a result, the porosity of Example 1 was found to be 17.9% by volume. The image processing results of Example 1 are shown in Figure 4. The same procedure was carried out to determine the porosity of the air electrode of Comparative Example 1. As a result, the porosity of Comparative Example 1 was found to be 37.8% by volume. As an example, the image processing results of Comparative Example 1 are shown in FIG. 5. The same procedure was carried out to determine the porosity of the air electrode of Comparative Example 2. As a result, the porosity of Comparative Example 2 was 28.0% by volume.

[0158] <Performance evaluation of proton-conducting ceramic cells> For the proton-conducting ceramic cell equipped with the air electrode of Example 1, hydrogen humidified at 25°C was supplied to the fuel electrode and air humidified at 25°C was supplied to the air electrode using an electrochemical measurement system (potentiostat / galvanostat, VSP-300, manufactured by Biologic), and the power generation characteristics were measured at 600°C. The results are shown in Figure 6. Similarly, the proton-conductive ceramic cell equipped with the air electrode of Comparative Example 1 was subjected to measurement of the power generation characteristics at 600° C. The results are shown in FIG. Similarly, the proton-conductive ceramic cell equipped with the air electrode of Comparative Example 2 was subjected to measurement of the power generation characteristics at 600° C. The results are shown in FIG.

[0159] As a result, Example 1 exhibited a significantly improved current density and a high output density compared to Comparative Examples 1 and 2. This is because, by setting the mass ratio of the electron conductive material to the proton conductive material (1), the electrode film thickness, and the electrode porosity within specific ranges, it was possible to simultaneously obtain the effect of reducing reaction resistance by expanding the reaction field within the electrode and the effect of reducing gas diffusion resistance by good gas diffusibility, thereby realizing low electrode resistance. [Industrial Applicability]

[0160] According to the present invention, it is possible to manufacture an electrode for a proton-conducting ceramic cell and a proton-conducting ceramic cell that have excellent performance, such as low electrode resistance and high current density. [Explanation of symbols]

[0161] 1. Proton-conducting ceramic cell electrodes 2 Electrolytes 3. Electronically Conductive Materials 4 Proton Conducting Materials (1)

Claims

1. An electrode for a proton-conducting ceramic cell, It is formed of at least an electron conductive material and a proton conductive material (1) containing Ba, the mass ratio of the electron conductive material to the proton conductive material (1) is greater than 100:0 and not greater than 20:80; The proton-conducting material (1) is represented by the following general formula (1): (Ba α１ A1 （１－α１） ) ｘ１ B1 ｙ１ O ３＋ｚ１ (1) (In formula (1), A1 is at least one of Ca, Sr, and La; B1 is at least one of Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu; α1 is 0.20 to 1.00; x1 is 0.80 to 1.20; y1 is 0.80 to 1.20; and z1 is −0.80 to 0.80.) is a perovskite oxide material represented by The electrode has a film thickness of 7.0 μm or less, the porosity of the electrode is 20.0% by volume or less; An electrode for a proton-conducting ceramic cell, characterized by:

2. 2. The electrode for a proton conducting ceramic cell according to claim 1, wherein when the thickness of the electrode is 0.1 μm≦thickness of the electrode<2.0 μm, the porosity of the electrode is 0.0 to 10.0 vol %.

3. 2. The electrode for a proton conducting ceramic cell according to claim 1, wherein when the thickness of the electrode is 2.0 μm≦thickness of the electrode≦7.0 μm, the porosity of the electrode is 0.0 to 20.0 vol %.

4. The electrical conductivity of the electrode is 1 to 2000 S / cm ２ 4. The electrode for a proton-conducting ceramic cell according to claim 1, wherein the electrode is a SiO 2 -SiO 3 ...

5. a nitrate-containing electrode material precursor preparation step of preparing a nitrate-containing electrode material precursor containing at least a metal element of an electron conductive material source and a metal element of a proton conductive material (1) source, in which at least a part of the metal elements are present as nitrates; a step of preparing a slurry for forming an electrode by mixing and dispersing the nitrate-containing electrode material precursor in a solvent to obtain a slurry for forming an electrode; an electrode coating film forming step of applying the electrode-forming slurry to an object to be coated and then drying the slurry to obtain a nitrate-containing electrode material precursor coating film; a pressing step of pressing the nitrate-containing electrode material precursor coating film at 10 to 500 MPa by cold isostatic pressing to obtain a pressurized product of the nitrate-containing electrode material precursor coating film; a firing step of firing the pressure-treated nitrate-containing electrode material precursor coating at 700 to 1200°C to obtain an electrode for a proton-conductive ceramic cell; 2. The method for producing an electrode for a proton-conducting ceramic cell according to claim 1, further comprising the steps of:

6. 6. The method for producing an electrode for a proton conducting ceramic cell according to claim 5, wherein the nitrate-containing electrode material precursor preparation step is a spray pyrolysis step of atomizing an aqueous solution for spraying containing metal ions of the electron conductive material source, metal ions of the proton conductive material (1) source, and nitrate ions, and then spray pyrolyzing the atomized aqueous solution for spraying to obtain a nitrate-containing electrode material precursor.

7. an electrolyte formed of at least a proton-conducting material (2); an air electrode; a fuel electrode; and Either one or both of the air electrode and the fuel electrode is the electrode for a proton-conducting ceramic cell according to any one of claims 1 to 4; A proton conducting ceramic cell characterized by:

8. The proton conductive material (2) is represented by the following general formula (2): <h2 style=";text-align:left;direction:ltr">(Ba<h2 style=";text-align:left;direction:ltr"> α２ <h2 style=";text-align:left;direction:ltr"> A2<h2 style=";text-align:left;direction:ltr"> （１－α２） <h2 style=";text-align:left;direction:ltr"> )<h2 style=";text-align:left;direction:ltr"> ｘ２ <h2 style=";text-align:left;direction:ltr"> B1<h2 style=";text-align:left;direction:ltr"> ｙ２ <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> ３＋ｚ２ <h2 style=";text-align:left;direction:ltr"> (2) (In formula (2), A2 is at least one of Ca, Sr, and La; B2 is at least one of Zr, Ce, Hf, Sc, Ga, Y, In, Gd, Dy, Ho, Tm, Er, Yb, and Lu; α2 is 0.20 to 1.00; x2 is 0.80 to 1.20; y2 is 0.80 to 1.20; and z2 is −0.80 to 0.80.) 8. The proton-conducting ceramic cell according to claim 7, wherein the perovskite oxide material is represented by the formula:

9. 9. The proton-conducting ceramic cell according to claim 7, wherein the electrolyte comprises a first portion containing the proton-conducting material (2) and Me (Me is at least one of Ti, Mn, Fe, Co, Ni, and Cu), and a second portion having a different Me content from that of the first portion.

10. 10. The proton-conducting ceramic cell according to claim 9, wherein the electrolyte comprises a first layer containing Me in a range of 0.0 mass % or more and less than 2.0 mass %, and a second layer laminated on the first layer and containing Me in a range of 2.0 mass % to 20.0 mass %.

11. 11. The proton conducting ceramic cell according to claim 7, wherein the electron conducting material is an electron conducting material for an air electrode, and the air electrode is an electrode for the proton conducting ceramic cell.

12. 12. The proton conducting ceramic cell according to claim 7, wherein the electron conducting material is an electron conducting material for a fuel electrode, and the fuel electrode is an electrode for the proton conducting ceramic cell.

13. 13. The proton-conducting ceramic cell according to claim 7, further comprising an intermediate layer between the electrolyte and the air electrode.

14. 14. The proton-conducting ceramic cell according to claim 7, further comprising an intermediate layer between the electrolyte and the fuel electrode.

Images