Solid oxide fuel cell

Abstract

This solid oxide fuel cell is provided with: a metal support; a bonding layer provided on the metal support; a fuel electrode layer provided on the bonding layer; an electrolyte layer provided on a fuel electrode; and an air electrode layer provided on the electrolyte layer. The metal support has a base material formed of an alloy containing Fe and Cr and having a porous structure, an oxide film containing Al or Si and covering the surface of the base material, and metallic reforming catalyst particles carried on the oxide film and having a reforming catalyst function for fuel. The bonding layer is formed of an alloy containing Fe and Cr, and has a porous structure.

Description

solid oxide fuel cell

[0001] The present invention relates to a solid oxide fuel cell.

[0002] Known solid oxide fuel cells (SOFCs) have a structure in which an anode layer is supported on a metal support. The metal support has a porous structure. During operation of such a cell, fuel is supplied to the anode layer through the metal support.

[0003] Furthermore, as a cell having the above-described configuration, a cell having a configuration in which a reforming catalyst is supported on a metal support is known. If a reforming catalyst is supported on a metal support, fuel can be reformed on the metal support. In other words, an internal reforming fuel cell is realized. Since there is no need to provide a separate reformer, this is advantageous in terms of space saving. For example, an example of an internal reforming fuel cell is the fuel cell structure described in Patent Document 1 (JP2021-170447A).

[0004] In the internal reforming type cell described above, a high-temperature mixture containing steam and hydrocarbons is supplied as raw fuel during internal reforming operation. The raw fuel is reformed by steam reforming on the metal support, resulting in the production of hydrogen as fuel.

[0005] Here, the metal support where the reforming reaction takes place is exposed to a high-temperature environment containing a large amount of water vapor. The fuel electrode layer side where the metal support is located is basically in a reducing atmosphere. However, in a high-temperature environment containing a large amount of water vapor, the metal support may oxidize even in a reducing atmosphere. Oxidation may cause a decrease in the performance (strength and electrical resistance) of the metal support. Therefore, it is desirable to suppress the oxidation of the metal support.

[0006] On the other hand, the metal support and the fuel electrode layer must be firmly bonded together. If the bonding strength between the metal support and the fuel electrode layer is weak, the metal support may peel off from the fuel electrode layer due to thermal stress or the like.

[0007] However, according to the investigations of the present inventors, when a metal support made of a material that is difficult to oxidize is used, it tends to be difficult to ensure sufficient bonding strength between the fuel electrode layer and the metal support.

[0008] Therefore, an object of the present invention is to provide a solid oxide fuel cell having a configuration in which oxidation of the metal support is suppressed and the metal support and the fuel electrode layer are firmly bonded together.

[0009] In one aspect, a solid oxide fuel cell according to the present invention includes a metal support, a bonding layer provided on the metal support, an anode layer provided on the bonding layer, an electrolyte layer provided on the anode layer, and a cathode layer provided on the electrolyte layer. The metal support includes a base material formed of an alloy containing Fe and Cr and having a porous structure, an oxide coating containing Al or Si that coats the surface of the base material, and metallic reforming catalyst particles supported on the oxide coating. The bonding layer is formed of an alloy containing Fe and Cr and has a porous structure.

[0010] In one aspect, a method of operating a solid oxide fuel cell according to the present invention includes the steps of providing the solid oxide fuel cell described above and supplying a fuel having an S / C greater than 1 to a metal support.

[0011] In one aspect, the present invention relates to a method for producing the above-mentioned solid oxide fuel cell, comprising the steps of: preparing a powder for a metal support, which is a precursor of the metal support, the powder being a powder formed of an alloy containing Fr and Cr and having Si and / or Al added thereto; forming the powder for a metal support into a sheet to obtain a green sheet for a metal support; firing the green sheet for a metal support in a reducing atmosphere to obtain a fired body; and heat-treating the fired body in an oxidizing atmosphere to form the oxide coating.

[0012] Fig. 1 is a schematic cross-sectional view showing a solid oxide fuel cell according to an embodiment. Fig. 2 is a schematic diagram showing the cross-sectional structure of a fuel cell and the relationship between the amount of water, the amount of hydrocarbon fuel, and the amount of hydrogen. Fig. 3 is a flowchart showing an example of a method for manufacturing a fuel cell.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] 1 is a schematic cross-sectional view showing the cell structure of a solid oxide fuel cell 1 according to this embodiment. In the following, the solid oxide fuel cell 1 may also be simply referred to as the fuel cell 1.

[0015] As shown in FIG. 1( a), the fuel cell 1 has a metal support 2, a bonding layer 6 provided on the metal support 2, a fuel electrode layer 3 provided on the bonding layer 6, an electrolyte layer 4 provided on the fuel electrode layer 3, and an air electrode layer 5 provided on the electrolyte layer 4.

[0016] The metal support 2 is provided to support the fuel electrode layer 3 etc. The metal support 2 has a porous structure to allow gas to pass through.

[0017] 1( b ) is an enlarged view showing the metal support 2. The metal support 2 has a base material 7, an oxide coating 8, and reforming catalyst particles 9.

[0018] The base material 7 has a porous structure and is made of an alloy containing Fe and Cr. Preferably, the base material 7 is a porous stainless steel body.

[0019] The oxide coating 8 is a coating formed from an oxide containing Al and / or Si. The oxide coating 8 covers the surface of the base material 7. The surface of the base material 7, including the inside of pores, is covered with the oxide coating 8. The oxide coating 8 is provided to suppress oxidation of the base material 7. The oxide coating 8 can be formed, for example, by using a manufacturing method described below.

[0020] The reforming catalyst particles 9 are supported on the oxide coating 8. The reforming catalyst particles 9 are metal particles and have the function of promoting the fuel reforming reaction. In the example shown in Fig. 1, the reforming catalyst particles 9 are supported on the oxide coating 8 so as to form a layer as a whole. The provision of the reforming catalyst particles 9 realizes an internal reforming function.

[0021] The bonding layer 6 is provided to bond the metal support 2 and the fuel electrode layer 3. The bonding layer 6 is made of the same material as the base material 7. That is, the bonding layer 6 is made of an alloy containing Fe and Cr. The bonding layer 6 also has a porous structure. As a result, the bonding layer 6 is gas permeable.

[0022] On the other hand, the content (concentration) of Al and Si in the bonding layer 6 is lower than the content (concentration) of Al and Si in the metal support 2. In other words, the oxide coating 8 contained in the metal support 2 is not contained in the bonding layer 6. Or, even if it is contained, the amount thereof is lower than that of the metal support 2.

[0023] The above is a schematic configuration of the fuel cell 1 according to this embodiment.

[0024] During operation of the fuel cell 1 (during internal reforming operation), an oxidant gas (e.g., air) is supplied to the air electrode layer 5. Furthermore, a mixed gas containing water vapor and a hydrocarbon (e.g., methane) is supplied at high temperature as a raw fuel to the metal support 2. The raw fuel reaches the fuel electrode layer 3 via the metal support 2 and the bonding layer 6. On the way there, the raw fuel is reformed in the metal support 2, producing hydrogen and the like. The produced hydrogen and the like are used as fuel in the fuel electrode layer 3. As a result, power is generated.

[0025] If the metal support 2 does not have the oxide coating 8, the base material 7 would be directly exposed to a high-temperature environment containing a large amount of water vapor. Direct exposure to such an environment could cause the base material 7 to oxidize. However, according to this embodiment, a coating of an oxide containing Al and / or Si is provided as the oxide coating 8. Oxides containing Al and / or Si are stable compounds. Therefore, the presence of the oxide coating 8 suppresses oxidation of the base material 7. This can prevent deterioration of the metal support 2 due to oxidation (such as a decrease in mechanical strength or electrical resistance).

[0026] On the other hand, if the surface of the base material 7 is covered with the oxide coating 8, the bonding strength between the metal support 2 and the fuel electrode layer 3 is likely to be low. As a result, the metal support 2 is likely to peel off from the fuel electrode layer 3 due to thermal stress and the like generated during the reforming reaction. However, in this embodiment, the bonding layer 6 is provided. Therefore, the metal support 2 and the fuel electrode layer 3 can be firmly bonded to each other.

[0027] The bonding layer 6 is more susceptible to oxidation than the metal support 2. However, the bonding layer 6 is disposed in an environment where oxidation is less likely to occur than the metal support 2. FIG. 2 is a schematic diagram showing the cross-sectional structure of the fuel cell 1 and the relationship between the amount of water, the amount of hydrocarbon, and the amount of hydrogen. In the metal support 2, fuel is reformed by a steam reforming reaction. As a result, hydrocarbons and water are consumed and hydrogen is produced. That is, in the metal support 2, the amounts of water and hydrocarbons decrease and the amount of hydrogen increases toward the inside (the fuel electrode layer 3 side). Metal oxidation is more likely to occur in areas with a higher water content. That is, in the metal support 2, oxidation is more likely to occur toward the outside and less likely to occur toward the inside. The bonding layer 6 is disposed inside the metal support 2. That is, the bonding layer 6 is disposed in an environment where oxidation is less likely to occur. As a result, oxidation of the bonding layer 6 is less likely to be a problem.

[0028] The above is an outline of this embodiment. For the reasons explained above, this embodiment provides a solid oxide fuel cell in which oxidation of the metal support is suppressed and the metal support and the fuel electrode layer are firmly bonded to each other.

[0029] Next, the detailed configuration of the fuel cell 1 will be described.

[0030] (Metal Support) The metal support 2 is preferably thicker than the bonding layer 6. By making the metal support 2 thicker than the bonding layer 6, the surface area of ​​the portion where the reforming reaction takes place can be increased. This can further improve the reforming performance. The thickness of the metal support 2 is, for example, 50 to 1000 μm, preferably 100 to 500 μm.

[0031] The porosity of the metal support 2 is preferably greater than the porosity of the bonding layer 6. This configuration increases the surface area of ​​the portion where the reforming reaction occurs. As a result, the reforming performance can be further improved. The porosity of the metal support 2 and the bonding layer 6 can be determined, for example, by obtaining a micrograph of the cross section and analyzing the image.

[0032] The pore diameter of the metal support 2 is preferably smaller than the pore diameter of the bonding layer 6. That is, it is preferable that the metal support 2 has a large number of small-diameter pores. With such a configuration, the surface area of ​​the portion where the reforming reaction takes place can be increased. As a result, the reforming performance can be further improved. The pore diameters of the metal support 2 and the bonding layer 6 can be determined, for example, by taking a micrograph of the cross section, performing image analysis, calculating the circle-equivalent diameter from the area of ​​each pore, and then calculating the number average.

[0033] As described above, in the metal support 2, an oxide coating 8 containing Al and / or Si is provided on the base material 7. The oxide coating 8 may be provided in an amount that sufficiently suppresses oxidation of the base material 7. For example, the amount of Al and Si in the metal support 2 is 0.1 to 10 mass %, and preferably 0.5 to 8 mass %.

[0034] As described above, the metal support 2 contains reforming catalyst particles. The reforming catalyst particles may be any particles that have the function of promoting the steam reforming reaction. For example, particles containing at least one element selected from the group consisting of Ni, Ru, Pt, Rh, and Co can be used as the reforming catalyst particles. The size of the reforming catalyst particles is, for example, at the nano-level.

[0035] The reforming catalyst particles are preferably contained not only in the metal support 2 but also in the fuel electrode layer 3. In the fuel electrode layer 3, water is produced as a result of the power generation reaction. Therefore, there is an abundant amount of moisture in the fuel electrode layer 3. If the fuel electrode layer 3 contains the reforming catalyst particles, the moisture can be used to promote the reforming reaction in the fuel electrode layer 3 as well. As a result, the reforming performance can be further improved.

[0036] (Bonding Layer) As described above, the bonding layer 6 is provided to bond the metal support 2 and the fuel electrode layer 3. As described above, the bonding layer 6 is formed of an alloy of Fe and Cr. For example, the bonding layer 6 is formed of stainless steel.

[0037] As described above, the Al and Si contents in the bonding layer 6 are lower than the Al and Si contents in the metal support 2. Specifically, it is preferable that the bonding layer 6 is substantially free of an oxide coating containing Al or Si. However, as the fuel cell 1 continues to operate, components of the oxide coating 8 in the metal support 2 may diffuse into the bonding layer 6. As a result, some Al and Si may also be contained in the bonding layer 6. This Al and Si may be contained in the bonding layer 6 in the form of oxides. However, even if such diffusion occurs, the concentrations of Al and Si contained in the bonding layer 6 are lower than the concentrations of Al and Si contained in the metal support 2. Even if such diffusion occurs, the functionality of the bonding layer 6 is maintained. That is, the bonding strength between the metal support 2 and the anode layer 3 is enhanced compared to when the metal support 2 and the anode layer 3 are directly bonded. Therefore, the bonding layer 6 may be configured so that the Al and Si concentrations therein are lower than the Al and Si concentrations in the metal support 2.

[0038] (Electrolyte Layer) The electrolyte layer 4 may be configured to be oxide ion conductive but gas impermeable. Preferably, the electrolyte layer 4 is made of dense ceramics. For example, the electrolyte layer 4 may be made of solid oxide ceramics. Examples of solid oxide ceramics include, but are not limited to, zirconia-containing materials and perovskite oxides. Examples of zirconia-containing materials include stabilized zirconia doped with yttria, neodymium oxide, samarium, gadolinium, scandium, and the like. The thickness of the electrolyte layer 4 is, for example, 0.5 to 20 μm, preferably 1 to 10 μm.

[0039] (Fuel Electrode Layer and Air Electrode Layer) The air electrode layer 5 is a layer that converts oxygen molecules contained in an oxidant gas into oxide ions, while the fuel electrode layer 3 is a layer that reacts a fuel such as hydrogen with the oxide ions to generate electrons.

[0040] The air electrode layer 5 and the fuel electrode layer 3 are formed of, for example, porous ceramics. Examples of porous ceramics include solid oxide ceramics. Examples of solid oxide ceramics include stabilized zirconia and perovskite oxide. Examples of stabilized zirconia include stabilized zirconia doped with yttria, neodymium oxide, samarium, gadolinium, scandium, or the like.

[0041] The thickness of each of the air electrode layer 5 and the fuel electrode layer 3 is, for example, 0.3 to 50 μm, and preferably 0.5 to 30 μm.

[0042] An air electrode catalyst for promoting the electrode reaction may be supported on the air electrode layer 5. Examples of such catalysts include praseodymium oxide.

[0043] An anode catalyst for promoting the electrode reaction may also be supported on the anode layer 3. Examples of such anode catalyst include nickel (Ni), palladium (Pd), platinum (Pt), ruthenium (Ru), Ni—Fe alloy, Ni—Co alloy, Fe—Co alloy, Ni—Cu alloy, and Pd—Pt alloy.

[0044] (Operating Method) As described above, when the fuel cell 1 according to this embodiment is operated, an oxidant gas (typically air) is supplied to the air electrode layer 5. On the other hand, on the fuel electrode layer 3 side, a hydrocarbon raw material containing a large amount of water vapor is supplied as a raw fuel to the metal support 2. The raw fuel is then reformed in the metal support 2 to produce hydrogen and the like. The produced hydrogen and the like are used as fuel in the fuel electrode layer 3.

[0045] Here, it is preferable to supply a raw fuel having an S / C ratio of more than 1 to the metal support 2 as the raw fuel. S / C means the steam-carbon ratio. That is, S / C is the ratio of the number of moles of water to the number of moles of carbon (i.e., flow rate ratio). Supplying a raw fuel having an S / C ratio of more than 1 makes it easier to generate hydrogen, and the reforming efficiency can be improved. For example, when the hydrocarbon raw material is methane, the following reaction is more likely to proceed. (Steam reforming reaction) CH ４ +H ２ O → 3H ２ + CO (water gas shift reaction) CO + H ２ O → H ２ +CO ２

[0046] Incidentally, S / C is more preferably 2 or more.

[0047] (Manufacturing Method) Next, a manufacturing method of the fuel cell 1 according to this embodiment will be described. The manufacturing method of the fuel cell 1 according to this embodiment includes the steps of: preparing a powder for a metal support, which is a precursor of the metal support, and preparing a powder formed of an alloy containing Fr and Cr and having Si and / or Al added thereto (S1); obtaining a green sheet for a metal support using the powder for a metal support (S2); firing the green sheet for a metal support in a reducing atmosphere to obtain a fired body (S4); and heat-treating the fired body in an oxidizing atmosphere to produce a metal support having an oxide coating (S7).

[0048] An example of the method for manufacturing the fuel cell 1 will be described below in detail. Fig. 3 is a flowchart showing an example of the method for manufacturing the fuel cell 1 according to this embodiment.

[0049] Step S1: Preparation of Powder for Metal Support First, a powder for a metal support is prepared as a precursor of the metal support 2. Specifically, a powder formed from an alloy containing Fr and Cr (e.g., stainless steel powder) to which Si and / or Al have been added is prepared as the powder for a metal support. The amount of Si and Al in the powder for a metal support is, for example, 0.1 to 20 mass %, preferably 0.5 to 10 mass %.

[0050] The powder for the metal support can be prepared, for example, by powder metallurgy. For example, a molten metal containing Fr and Cr is prepared, and Si and / or Al is added to the molten metal. Then, the prepared molten metal is granulated by water atomization or gas atomization to produce powder with a size of about 5 to 50 μm. This produces the powder for the metal support.

[0051] Step S2: Preparation of Metal Support Green Sheet Next, a metal support green sheet is prepared using the metal support powder. For example, a slurry containing the metal support powder and, if necessary, other additives (binder, pore-forming agent, etc.) is prepared. The prepared slurry is then molded into a sheet. For example, a tape casting method can be used for molding. This results in a metal support green sheet.

[0052] In addition, similar to the green sheet for the metal support, a green sheet for the bonding layer, a green sheet for the fuel electrode layer, and a green sheet for the electrolyte layer are also prepared. These green sheets can also be prepared by preparing a slurry containing precursors of the constituent materials of each layer and using a tape casting method or the like. In addition, when preparing the green sheet for the bonding layer, unlike when preparing the green sheet for the metal support, Si and Al are not added, or even if they are added, the amount (concentration) is less than that of the green sheet for the metal support.

[0053] Step S3: Lamination Next, the green sheet for the metal support, the green sheet for the bonding layer, the green sheet for the fuel electrode layer, and the green sheet for the electrolyte are laminated together to obtain a green sheet laminate. If necessary, the green sheet laminate is cut to a desired size.

[0054] Step S4: Firing (reducing atmosphere) Next, the green sheet laminate is fired in a reducing atmosphere, thereby obtaining a laminate including the metal support, the bonding layer, the fuel electrode layer, and the electrolyte layer.

[0055] Step S5: Impregnation of anode catalyst and heat treatment Next, a slurry containing the anode catalyst is prepared. The prepared slurry is supplied to the anode layer from the metal support 2 side and allowed to impregnate. Note that a mask may be formed before the slurry is impregnated to prevent the slurry from impregnating unnecessary areas. For example, a mask can be formed by applying a sealant to the outer periphery of the laminate. After the slurry is impregnated, a heat treatment is performed. This causes the anode catalyst to be supported as particles on the anode layer.

[0056] Step S6: Impregnation of reforming catalyst and heat treatment Subsequently, a slurry containing the reforming catalyst is prepared. The prepared slurry is then supplied to the metal support 2 and impregnated therein. Then, a heat treatment is performed. As a result, the reforming catalyst particles are supported on the metal support 2.

[0057] Step S7: Fabrication of Air Electrode Layer After that, the air electrode layer is formed on the electrolyte layer. The air electrode layer can be formed by, for example, screen printing. For example, a perovskite oxide (e.g., LaSrCoFeO ３ The ink is prepared by mixing the electrolyte powder with an organic binder solution. The ink is then screen-printed onto the surface of the electrolyte layer and baked in an air atmosphere (oxidizing atmosphere) at 800 to 1200°C. This completes the formation of the air electrode layer.

[0058] In this case, by performing firing in an oxidizing atmosphere, the additive Si and / or Al in the metal support oxidizes to form an oxide coating 8. As a result, a configuration is obtained in which the surface of the base material 7 is covered with the oxide coating 8.

[0059] The fuel cell 1 according to this embodiment can be obtained by the method described above. In the above example, an oxide film is formed in step S7, but if the heat treatments in steps S5 and S6 are performed in an oxidizing atmosphere, it is also possible to form the oxide film 8 in these steps. In other words, if a heat treatment is performed in an oxidizing atmosphere after step S4 (firing), the oxide film 8 can be formed on the surface of the base material 7 of the metal support 2.

[0060] (Applications) The application of the fuel cell according to this embodiment is not particularly limited. A preferred application is for use in a vehicle. Fuel cells for use in a vehicle are limited in terms of space. The fuel cell 1 according to this embodiment is an internal reforming type cell, so there is no need to provide a separate reformer. This has the advantage of saving space. Therefore, it is suitable as a fuel cell for use in a vehicle, where space saving is required.

[0061] (Examples) Next, in order to explain the present invention in more detail, examples carried out by the present inventors will be described.

[0062] Example 1 A stainless steel powder containing 1% by mass of Si was used as the metal support powder, and a fuel cell according to Example 1 was fabricated according to the method described in steps S1 to S7 above. The size of the fuel cell was 0.5 mm thick, 40 mm long, and 10 mm wide.

[0063] Example 2 A fuel cell according to Example 2 was fabricated in the same manner as in Example 1, except that Fe and Cr powders to which 5% by mass of Al had been added were used as the powder for the metal support.

[0064] Comparative Example 1 A fuel cell according to Comparative Example 1 was fabricated in the same manner as in Example 1, except that Si was not added.

[0065] (Measurement of the rate of change in electrical resistance) A voltage line and a current line were connected to the fuel cells according to Examples 1 and 2 and Comparative Example 1. Then, the fuel cells were heated at 600° C. with H ２ / H ２ The fuel cell 1 was operated while supplying a gas having a volume ratio of O of 50:50% to the metal support 2. Then, the rate of change in electrical resistance before and after a predetermined time period was measured.

[0066] (Measurement Results) Compared to Comparative Example 1, Example 1, in which Si was added, had a resistance change rate that was half. Furthermore, Example 2, in which Al was added, had a resistance change rate that was one-tenth of that of Comparative Example 1. These results confirm that by using a powder to which Si or Al was added as the powder for the metal support, an oxide film is formed on the base material of the metal support 2, oxidation of the metal support is suppressed, and the resistance change rate is reduced.

[0067] [Additional Notes] The following is a summary of the typical configuration and effects of this embodiment.

[0068] (Supplementary Note 1) A solid oxide fuel cell comprising: a metal support 2; a bonding layer 6 provided on the metal support 2; an anode layer 3 provided on the bonding layer 6; an electrolyte layer 4 provided on the anode layer 3; and an air cathode layer 5 provided on the electrolyte layer 4; the metal support 2 has a base material 7 formed of an alloy containing Fe and Cr and having a porous structure; an oxide coating 8 containing Al or Si and coating the surface of the base material 7; and metallic reforming catalyst particles 9 supported on the oxide coating 8; and the bonding layer 6 is formed of an alloy containing Fe and Cr and has a porous structure.

[0069] According to the above-described configuration, the oxide coating 8 is provided, which prevents oxidation of the metal support 2. Furthermore, the bonding layer 6 is provided, which allows the metal support 2 and the fuel electrode layer 3 to be firmly bonded together despite the presence of the oxide coating 8.

[0070] (Supplementary Note 2) The solid oxide fuel cell according to Supplementary Note 1, wherein the concentrations of Al and Si contained in the bonding layer are lower than the concentrations of Al and Si contained in the metal support.

[0071] By using a bonding layer having such a structure, the metal support 2 and the fuel electrode layer 3 can be bonded with sufficient strength.

[0072] (Supplementary Note 3) The solid oxide fuel cell according to Supplementary Note 1 or 2, wherein the reforming catalyst particles contain at least one selected from the group consisting of Ni, Ru, Pt, Rh, and Co.

[0073] By adopting such a configuration, it is possible to impart a fuel reforming function to the metal support.

[0074] (Supplementary Note 4) The solid oxide fuel cell according to Supplementary Note 3, wherein the reforming catalyst particles are also contained in the fuel electrode layer.

[0075] By adopting such a configuration, reforming can also be carried out in the fuel electrode layer, and reforming performance can be improved.

[0076] (Supplementary Note 5) The solid oxide fuel cell according to any one of Supplementary Notes 1 to 4, wherein the metal support is thicker than the bonding layer.

[0077] With this configuration, the surface area of ​​the portion where the reforming reaction takes place can be increased, thereby improving the reforming performance.

[0078] (Supplementary Note 6) The solid oxide fuel cell according to any one of Supplementary Notes 1 to 5, wherein the porosity of the metal support is greater than the porosity of the bonding layer.

[0079] With this configuration, the surface area of ​​the portion where the reforming reaction takes place can be increased, thereby improving the reforming performance.

[0080] (Supplementary Note 7) The solid oxide fuel cell according to any one of Supplementary Notes 1 to 6, wherein the pore size of the metal support is smaller than the pore size of the bonding layer.

[0081] With this configuration, the surface area of ​​the portion where the reforming reaction takes place can be increased, thereby improving the reforming performance.

[0082] (Supplementary Note 8) A method for operating a solid oxide fuel cell, comprising the steps of: providing a solid oxide fuel cell according to any one of Supplementary Notes 1 to 7; and supplying a fuel having an S / C ratio of greater than 1 to a metal support.

[0083] According to this method, the reforming reaction can be facilitated.

[0084] (Appendix 9) A method for producing a solid oxide fuel cell according to any one of Appendices 1 to 7, comprising the steps of: preparing a powder for a metal support, which is a precursor of the metal support, the powder for the metal support being a powder formed of an alloy containing Fr and Cr and having Si and / or Al added thereto (S1); forming the powder for the metal support into a sheet to obtain a green sheet for the metal support (S2); firing the green sheet for the metal support in a reducing atmosphere to obtain a fired body (S4); and heat-treating the fired body in an oxidizing atmosphere to form an oxide coating (S7).

[0085] According to this method, a fuel cell having a metal support provided with an oxide coating can be obtained.

Claims

1. A solid oxide fuel cell comprising: a metal support; a bonding layer provided on the metal support; an anode layer provided on the bonding layer; an electrolyte layer provided on the anode layer; and an air cathode layer provided on the electrolyte layer, wherein the metal support comprises: a base material formed of an alloy containing Fe and Cr and having a porous structure; an oxide coating containing Al or Si and coating the surface of the base material; and metallic reforming catalyst particles supported on the oxide coating, wherein the bonding layer is formed of an alloy containing Fe and Cr and has a porous structure.

2. A solid oxide fuel cell according to claim 1, wherein the concentrations of Al and Si contained in the bonding layer are lower than the concentrations of Al and Si contained in the metal support.

3. A solid oxide fuel cell according to claim 1 or 2, wherein the reforming catalyst particles contain at least one element selected from the group consisting of Ni, Ru, Pt, Rh and Co.

4. A solid oxide fuel cell according to claim 3, wherein the reforming catalyst particles are also contained in the fuel electrode layer.

5. A solid oxide fuel cell according to claim 1 or 2, wherein the metal support is thicker than the bonding layer.

6. A solid oxide fuel cell according to claim 1 or 2, wherein the porosity of the metal support is greater than the porosity of the bonding layer.

7. A solid oxide fuel cell according to claim 1 or 2, wherein the pore size of the metal support is smaller than the pore size of the bonding layer.

8. A method for operating a solid oxide fuel cell, comprising the steps of: providing a solid oxide fuel cell according to claim 1 or 2; and supplying a fuel having an S / C ratio of greater than 1 to the metal support.

9. A method for producing a solid oxide fuel cell as claimed in claim 1, comprising the steps of: preparing a powder for a metal support, which is a precursor of the metal support, and which is a powder formed from an alloy containing Fr and Cr and to which Si and / or Al has been added; forming the powder for a metal support into a sheet to obtain a green sheet for a metal support; firing the green sheet for a metal support in a reducing atmosphere to obtain a fired body; and heat treating the fired body in an oxidizing atmosphere to form the oxide coating.