Solid oxide fuel cell, method for manufacturing solid oxide fuel cell, and solid oxide electrolysis cell

Abstract

To provide a technique that can prevent oxidation of a metal support layer in a metal-supported solid oxide fuel cell or solid oxide electrolysis cell.SOLUTION: A solid oxide fuel cell includes a metal support layer, a fuel electrode layer, an electrolyte layer, and a cathode layer. The metal support layer has a first region, and a second region located downstream of the first region. The exposed area per unit volume of the second region is smaller than the exposed area per unit volume of the first region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid oxide fuel cell, a method for manufacturing a solid oxide fuel cell, and a solid oxide electrolysis cell. [Background technology]

[0002] A known solid oxide fuel cell (SOFC) cell has a structure in which a fuel electrode layer, an electrolyte layer, and a cathode layer are stacked in this order on a gas-permeable metal support layer. Such a solid oxide fuel cell cell is sometimes called a metal-supported solid oxide fuel cell.

[0003] In relation to the above, Patent Document 1 (JP 2019-204612 A) discloses a single fuel cell having a cell section including an anode layer, a solid electrolyte layer, and a cathode layer, and a support layer disposed in contact with the anode layer and supporting the cell section, the support layer having a diffusion layer disposed in contact with the anode layer and diffusing fuel gas in the cell plane, and a crack layer disposed in contact with the diffusion layer and having cracks extending in the film thickness direction. Patent Document 1 also describes that the crack layer is made of a porous metal material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-204612 Summary of the Invention [Problem to be solved by the invention]

[0005] In a metal-supported solid oxide fuel cell, fuel gas is supplied to the anode layer through a metal support layer. Specifically, the fuel gas is supplied so that it flows over the metal support layer. A portion of the fuel gas is supplied to the anode layer through the metal support layer and consumed in the power generation reaction. As a result of the power generation reaction, water vapor is produced. Therefore, the metal support layer is exposed to an environment containing water vapor. Solid oxide fuel cells are operated at high temperatures. Exposure to a high-temperature environment with a high water vapor concentration can cause the metal support layer to oxidize. Oxidation of the metal support layer should be avoided because it indicates deterioration of the metal support layer.

[0006] Furthermore, solid oxide electrolysis cells are known as devices having a similar structure to solid oxide fuel cells. In solid oxide electrolysis cells, water vapor is supplied instead of fuel gas. In solid oxide electrolysis cells, the metal support layer is also exposed to an environment containing water vapor. As with solid oxide fuel cells, deterioration of the metal support layer due to water vapor oxidation can be a problem in solid oxide electrolysis cells.

[0007] Therefore, an object of the present invention is to provide a technique capable of preventing oxidation of a metal support layer in a metal-supported solid oxide fuel cell or solid oxide electrolysis cell. [Means for solving the problem]

[0008] In one aspect, a solid oxide fuel cell according to the present invention includes a gas-permeable metal support layer, an anode layer provided on the metal support layer, an electrolyte layer provided on the anode layer, and an air cathode layer provided on the electrolyte layer. The anode layer has a porous structure. The metal support layer is configured so that fuel gas flows over it in the fuel gas flow direction. The metal support layer has a first region and a second region provided downstream of the first region in the fuel gas flow direction. The exposed area per unit volume of the second region is smaller than the exposed area per unit volume of the first region.

[0009] In one aspect, the solid oxide fuel cell stack according to the present invention comprises a first stack having a first cell and a second stack having a second cell. The first cell and the second cell each have a gas-permeable metal support layer, an anode layer provided on the metal support layer, an electrolyte layer provided on the anode layer, and an air cathode layer provided on the electrolyte layer. The first cell and the second cell are each configured so that fuel gas flows over the metal support layer. The first stack and the second stack are connected so that fuel gas discharged from the first stack is supplied to the second stack. The exposed area per unit volume of the metal support layer of the second cell is smaller than the exposed area per unit volume of the metal support layer of the first cell.

[0010] In one aspect, a solid oxide electrolysis cell according to the present invention comprises a gas-permeable metal support layer, an anode layer disposed on an anode electron-conducting layer, an electrolyte layer disposed on the anode layer, and an air cathode layer disposed on the electrolyte layer. The anode layer has a porous structure. The metal support layer is configured so that water vapor flows over it in the water vapor flow direction. The metal support layer has a first region and a second region disposed downstream of the first region in the water vapor flow direction. The exposed area per unit volume of the first region is smaller than the exposed area per unit volume of the second region. [Effects of the Invention]

[0011] According to the present invention, a technique is provided that can prevent oxidation of a metal support layer in a metal-supported solid oxide fuel cell or solid oxide electrolysis cell. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a solid oxide fuel cell according to the first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a solid oxide fuel cell according to the second embodiment. [Figure 3]FIG. 3 is a schematic cross-sectional view showing a solid oxide fuel cell according to a third embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a solid oxide fuel cell stack according to the fourth embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing a solid oxide electrolysis cell according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0014] (1) First embodiment Fig. 1 is a cross-sectional view schematically showing a solid oxide fuel cell 1 according to this embodiment. Fig. 1 also schematically shows the flow direction of fuel gas, fuel concentration, and H2O concentration.

[0015] 1(a), a solid oxide fuel cell 1 has a metal support layer 2, a fuel electrode layer 3, an electrolyte layer 4, and a cathode layer 5. These are stacked in this order along the stacking direction.

[0016] The electrolyte layer 4 is configured to be conductive to oxide ions but not permeable to gases.

[0017] The fuel electrode layer 3 is a portion where a fuel such as hydrogen reacts with oxide ions to generate electrons. The fuel electrode layer 3 has a porous structure. The fuel electrode layer 3 has electron conductivity.

[0018] The air electrode layer 5 is a portion that converts oxygen molecules contained in the oxidant gas into oxide ions. Like the fuel electrode layer 3, the air electrode layer 5 also has electronic conductivity.

[0019] The metal support layer 2 is a portion that functions as a support material for the solid oxide fuel cell 1. The metal support layer 2 is gas permeable. Specifically, the metal support layer 2 has pores that allow gas to pass through in the thickness direction. The metal support layer 2 is also configured so that fuel gas flows over it (on the surface opposite to the fuel electrode layer 3) in the fuel gas flow direction. The fuel gas flow direction is perpendicular to the stacking direction of the cells.

[0020] The metal support layer 2 has a first region 2-1 and a second region 2-2. The second region 2-2 is located downstream of the first region 2-1 in the fuel gas flow direction. The first region 2-1 and the second region 2-2 have different exposed areas per unit volume. Specifically, the exposed area per unit volume in the second region 2-2 is smaller than that in the first region 2-1. In other words, the second region 2-2 has a denser structure than the first region 2-1.

[0021] In this specification, the term "exposed area per unit volume" refers to the BET specific surface area measured using nitrogen. In the following description, the term "exposed area per unit volume" may be simply referred to as "exposed area."

[0022] In this embodiment, during operation, a fuel gas is supplied to the anode layer 3, and an oxidant gas is supplied to the cathode layer 5. A gas containing hydrogen or a hydrocarbon is typically used as the fuel gas. The fuel gas is supplied to the metal support layer 2 (on the surface opposite the anode layer 3) so as to flow in the fuel gas flow direction. Because the metal support layer 2 is gas permeable, a portion of the fuel gas is supplied to the anode layer 3 through the metal support layer 2. The fuel gas supplied to the anode layer 3 is consumed by the power generation reaction. As a result of the power generation reaction, water vapor (HO) is generated. The generated water vapor flows downstream along with the fuel gas. Therefore, as shown in FIG. 1(b), the water vapor (HO) concentration increases from the upstream side to the downstream side. Here, the solid oxide fuel cell 1 is operated at high temperatures. When the metal support layer 2 is exposed to a high-temperature environment containing water vapor, it may be oxidized by water vapor oxidation. The metal support layer 2 is particularly susceptible to oxidation downstream, where the water vapor concentration is high.

[0023] However, in this embodiment, the exposed area in the second region 2-2 located downstream is smaller than that in the first region 2-1. A smaller exposed area reduces the area exposed to water vapor, making steam oxidation less likely to occur. In other words, this embodiment employs a configuration that makes steam oxidation less likely to occur in the portion exposed to an environment with a high water vapor concentration. Therefore, deterioration of the metal support layer 2 can be prevented.

[0024] In the second region 2-2, the exposed area is small, resulting in low gas permeability. Therefore, in the downstream portion, the amount of fuel gas supplied to the anode layer 3 via the second region 2-2 is small (see the dotted arrow in FIG. 1 ). However, as shown by the solid arrow in FIG. 1 , the fuel gas can be sufficiently supplied to the anode layer 3 via the first region 2-1. Because the anode layer 3 has a porous structure, the fuel gas supplied to the anode layer 3 can flow downstream within the anode layer 3. Therefore, although the gas permeability of the second region 2-2 is low, a sufficient amount of fuel gas can be supplied to the downstream portion of the anode layer 3. Furthermore, because the anode layer 3 has electronic conductivity, the current required for power generation can also be supplied to the downstream portion of the anode layer 3. Therefore, even though a portion of the metal support layer 2 (i.e., the second region 2-2) with low gas permeability is provided, the decrease in power generation efficiency downstream is minimized.

[0025] The above is an outline of this embodiment. Next, the details of this embodiment will be described.

[0026] (metal support layer) As shown in FIG. 1 , in this embodiment, the metal support layer 2 has a metal sintered body 7 having a porous structure as a skeletal material. The metal sintered body 7 is a structure in which metal particles are integrated by sintering. Using the metal sintered body 7, a metal support layer 2 with high gas permeability can be realized. For example, a stainless steel sintered body can be used as the metal sintered body 7. The size and number of pores in the metal sintered body 7 can be controlled, for example, by the concentration and size of a pore-forming agent used during production. By controlling the size and number of pores in the metal sintered body 7 during production, a first region 2-1 and a second region 2-2 with different exposed areas can be realized.

[0027] As described above, the exposed area in this embodiment means the BET specific surface area measured using nitrogen. The BET specific surface areas of the first region 2-1 and the second region 2-2 are not particularly limited. For example, the BET specific surface area of ​​the second region 2-2 is 0.001 to 0.1 m2 / g, preferably 0.01 to 0.05 m 2 / g.

[0028] The exposed area within each of the first region 2-1 and the second region 2-2 may or may not be constant. For example, the exposed area within the metal support layer 2 may increase stepwise from the upstream side to the downstream side in the fuel gas flow direction. Alternatively, the exposed area within the metal support layer 2 may be configured to gradually decrease from the upstream side to the downstream side. In such a case, any portion of the metal support layer 2 on the upstream side can be considered to be the first region 2-1, and any portion on the downstream side can be considered to be the second region 2-2.

[0029] There are no particular limitations on the thickness of the metal support layer 2. For example, the thickness of the metal support layer 2 is 50 to 1000 μm, and preferably 100 to 500 μm.

[0030] (Antioxidant layer) 1, an antioxidant layer 8 is preferably provided in the second region 2-2 so as to cover the surface of the metal support layer 2. The surface here refers to the surface including the inner surface of the metal support layer 2. Specifically, the antioxidant layer 8 is provided so as to cover the surface of each particle constituting the metal sintered body 7.

[0031] The oxidation resistance of the second region 2-2 can be further improved by providing the antioxidant layer 8. As a result, deterioration of the metal support layer 2 on the downstream side can be more reliably prevented.

[0032] The first region 2-1 may or may not have an antioxidant layer 8. Preferably, the thickness of the antioxidant layer 8 in the second region 2-2 is greater than the thickness of the antioxidant layer 8 covering the surface of the first region 2-1. If the antioxidant layer 8 is not provided in the first region 2-1, the thickness of the antioxidant layer 8 in the first region 2-1 can be said to be "zero." In other words, even if no antioxidant layer is provided in the first region 2-1 and an antioxidant layer is provided only in the second region 2-2, this also falls under the statement that "the thickness of the antioxidant layer 8 in the second region 2-2 is greater than the thickness of the antioxidant layer 8 covering the surface of the first region 2-1."

[0033] The thickness of the antioxidant layer 8 in the second region 2-2 is, for example, 0.01 to 10 μm.

[0034] The antioxidant layer 8 may be formed of any material that has the function of suppressing oxidation of the skeletal material (i.e., the metal sintered body 7) of the metal support layer 2. For example, the antioxidant layer 8 may be formed of a material containing at least one element selected from the group consisting of B, Na, Mg, Al, Si, K, Ca, Sc, Mn, Co, Ni, Cu, Zn, Y, Zr, Ru, Rh, Pd, Ba, Ir, Pt, Au, and Ce.

[0035] For example, the antioxidant layer 8 can be made of a ceramic glass material, such as a material containing at least one element selected from the group consisting of B, Na, Mg, Al, Si, K, and Ca.

[0036] Alternatively, the antioxidant layer 8 may be a layer formed by plating or electrodeposition. Examples of layers formed by such means include layers containing at least one element selected from the group consisting of Mn, Co, Ni, Cu, Zn, Y, and Zr.

[0037] Alternatively, the antioxidant layer 8 can be formed of a material with a reforming function. The reforming function here refers to the function of reforming fuel. The fuel reforming function refers, for example, to the function of generating hydrogen from hydrocarbons contained in fuel gas. Examples of materials with such a reforming function include materials containing at least one element selected from the group consisting of Ru, Rh, Pd, Ba, Ir, Pt, Au, and Ce. If such a material with a reforming function is provided in the metal support layer 2, the fuel can be reformed in the metal support layer 2, thereby realizing a so-called internal reforming fuel cell. However, the solid oxide fuel cell 1 according to this embodiment does not necessarily have to be an internal reforming type and may be an external reforming type.

[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, etc. The thickness of the electrolyte layer 4 is, for example, 0.5 to 20 μm, preferably 1 to 10 μm.

[0039] (air cathode layer) The air electrode layer 5 is a portion that converts oxygen molecules contained in the oxidant gas into oxide ions. The air electrode layer 5 is formed of a conductive ceramic material such as lanthanum strontium cobalt composite oxide (LSC) and lanthanum strontium cobalt iron oxide (LSCF). The thickness of the air electrode layer 5 is, for example, 0.3 to 50 μm, and preferably 0.5 to 30 μm.

[0040] (Fuel electrode layer) The fuel electrode layer 3 is a portion that reacts a fuel such as hydrogen with oxide ions to generate electrons. The material of the fuel electrode layer 3 is not particularly limited. The fuel electrode layer 3 can be formed from a material containing, for example, SUS and stabilized zirconia (SSZ). The thickness of the fuel electrode layer 3 is, for example, 0.3 to 50 μm, and preferably 0.5 to 30 μm.

[0041] (Manufacturing method) Next, a manufacturing method will be described. There are no particular limitations on the manufacturing method of the solid oxide fuel cell 1 according to this embodiment. For example, the solid oxide fuel cell 1 according to this embodiment can be obtained by the method described below.

[0042] First, a green sheet for the metal support layer is prepared. The green sheet for the metal support layer can be obtained, for example, by screen printing. Specifically, first, a material for the first region is prepared to form the first region. For example, a slurry containing metal particles constituting the metal support layer 2 and a pore-forming agent for forming a porous structure is prepared as the material for the first region. Similarly, a material for the second region is prepared to form the second region. At this time, the content of the pore-forming agent is reduced compared to the material for forming the first region. Next, the material for the first region and the material for the second region are separately applied to some kind of substrate by screen printing. This allows for the production of a green sheet for the metal support layer including a region intended to become the first region and a region intended to become the second region.

[0043] Furthermore, a green sheet for the fuel electrode layer and a green sheet for the electrolyte are prepared. These green sheets can be prepared, for example, by tape casting. The green sheet for the metal support layer, the green sheet for the fuel electrode layer, and the green sheet for the electrolyte are then laminated together to obtain a green sheet laminate. If necessary, the obtained green sheet laminate is cut to adjust the size. Thereafter, the green sheet laminate is fired in a reducing atmosphere (for example, at 1000 to 1500°C).

[0044] Thereafter, if necessary, an antioxidant layer is formed on the metal support layer. For example, a slurry containing constituent materials of the antioxidant layer is prepared, and the prepared slurry is supplied to the metal support layer and heat-treated in an oxidizing or inert gas atmosphere. This allows the antioxidant layer to be formed. Alternatively, the antioxidant layer can be formed by plating or electrodeposition. In this case, after the plating or electrodeposition, heat treatment is performed in a reducing atmosphere. This densifies the film formed by the plating or electrodeposition and functions as an antioxidant layer. This method also allows the antioxidant layer to be formed.

[0045] Then, an air electrode layer is formed on the electrolyte layer. For example, a green sheet for the air electrode layer is prepared and laminated on the electrolyte layer. Then, the laminate is fired. This allows the air electrode layer to be obtained.

[0046] Next, if necessary, a slurry containing an electrode catalyst (a fuel electrode catalyst and an air electrode catalyst) is supplied to the fuel electrode layer and the air electrode layer. Then, a heat treatment is performed to support the electrode catalyst on each electrode. This allows the solid oxide fuel cell 1 having the configuration shown in FIG. 1 to be obtained.

[0047] (2) Second embodiment Next, a second embodiment will be described. Detailed description will be omitted for the fact that the same configuration as the first embodiment can be adopted.

[0048] 2 is a schematic cross-sectional view showing a solid oxide fuel cell 1 according to this embodiment. In the first embodiment, the metal support layer 2 contains a metal sintered body as a skeletal material. In contrast, in this embodiment, the metal support layer 2 includes a metal plate having through holes. The metal plate is preferably a stainless steel plate.

[0049] The number of through holes per unit area in the second region 2-2 is smaller than the number of through holes per unit area in the first region 2-1, resulting in a smaller exposed area in the second region 2-2 than in the first region 2-1.

[0050] Even when the metal support layer 2 having the configuration of this embodiment is used, the same effects as those of the first embodiment are achieved. That is, since the exposed area is small in the second region 2-2 located on the downstream side, steam oxidation is unlikely to progress. This makes it possible to prevent deterioration of the metal support layer 2 on the downstream side exposed to a high water vapor concentration.

[0051] Furthermore, the through holes can be easily formed during manufacturing. For example, a metal plate is prepared and through holes are formed using a laser to obtain the metal support layer 2. Alternatively, the metal support layer 2 can be obtained by rolling a punched metal.

[0052] Also in this embodiment, similarly to the previously described embodiments, it is preferable that the surface (including the inner surface of the through hole) of the second region 2-2 is covered with the antioxidant layer 8. This makes it possible to more reliably prevent oxidation in the second region 2-2.

[0053] The method for manufacturing the solid oxide fuel cell 1 according to this embodiment is not particularly limited. For example, first, a metal plate is prepared. Then, through holes are formed so as to form the first region 2-1 and the second region 2-2. The through holes can be formed, for example, by a laser. Alternatively, the through holes may be formed by punching. After the through holes are formed, a rolling process or the like may be performed. That is, the metal support layer 2 may be obtained by rolling a punched metal.

[0054] Thereafter, the fuel electrode layer 3 and the electrolyte layer 4 are formed on the metal support layer 2 using screen printing or the like. Then, firing (1000 to 1500°C) is performed in a reducing atmosphere or an inert gas atmosphere. Thereafter, as in the first embodiment, an antioxidant layer 8 is formed as needed. Furthermore, an air electrode layer 5 is formed on the electrolyte layer 4. Then, as needed, an electrode catalyst is supplied to each electrode by impregnation or screen printing, and heat treatment is performed. In this way, the solid oxide fuel cell 1 according to this embodiment can be obtained.

[0055] (3) Third embodiment Next, a third embodiment will be described. Note that detailed description will be omitted for the points where the same configuration as in the above-described embodiments can be adopted.

[0056] 3 is a schematic cross-sectional view showing a solid oxide fuel cell 1 according to this embodiment. As shown in FIG. 3, in this embodiment, an anode electron conductive layer 6 is provided between the anode layer 3 and the metal support layer 2.

[0057] The anode electron conductive layer 6 has a porous structure and is electron conductive.

[0058] According to this embodiment, the provision of the anode electron conductive layer 6 can improve power generation efficiency. That is, during operation, as shown by the arrows in FIG. 3 , the fuel gas and current flow more easily downstream in the anode electron conductive layer 6. Therefore, the current necessary for the power generation reaction is sufficiently supplied to the downstream portion of the anode layer 3. This improves power generation efficiency.

[0059] The thickness of the anode electron conductive layer 6 is preferably greater than the thickness of the anode layer 3. For example, the thickness of the anode electron conductive layer 6 is 20 μm or more. With such a thickness, a sufficient amount of current flows downstream in the anode electron conductive layer 6. In a more preferred embodiment, the thickness of the anode layer 3 is 2 to 10 μm, and the thickness of the anode electron conductive layer 6 is 20 μm or more. There is no particular upper limit to the thickness of the anode electron conductive layer 6, but it is, for example, 50 μm or less, preferably 30 μm or less.

[0060] The anode electron conductive layer 6 preferably contains at least one element selected from the group consisting of Ni, Pt, Ru, Rh, and Co. If the anode electron conductive layer 6 contains such an element, high electron conductivity is achieved in the anode electron conductive layer 6 during operation, thereby improving power generation efficiency.

[0061] For example, anode electron conductive layer 6 can be formed of a cermet containing at least one element selected from the group consisting of Ni, Pt, Ru, Rh, and Co.

[0062] Alternatively, anode electron conductive layer 6 can be formed from a ceramic material carrying at least one metal selected from the group consisting of Ni, Pt, Ru, Rh, and Co.

[0063] (4) Fourth embodiment Next, a fourth embodiment will be described. Note that detailed description will be omitted for the points where the same configuration as in the above-described embodiments can be adopted.

[0064] In the above-described embodiments, a solid oxide fuel cell 1 has been described. In contrast, the present embodiment will describe a solid oxide fuel cell stack 9. In the solid oxide fuel cell stack 9 according to the present embodiment, the technology described for the solid oxide fuel cell 1 in the above-described embodiments is applied to the solid oxide fuel cell stack 9.

[0065] FIG. 4 is a schematic diagram showing a solid oxide fuel cell stack 9 according to this embodiment. For reference, FIG. 4 also shows a schematic representation of the fuel concentration and water vapor (H2O) concentration. The solid oxide fuel cell stack 9 has a first stack 9-1 and a second stack 9-2. The first stack 9-1 includes at least one first cell. Meanwhile, the second stack 9-2 includes at least one second cell. The first stack 9-1 and the second stack 9-2 are connected so that fuel gas discharged from the first stack 9-1 is supplied to the second stack 9-2.

[0066] The first cell and the second cell both have substantially the same configuration (see, for example, FIG. 1 ) as the solid oxide fuel cell described in the previous embodiment. That is, the first cell and the second cell each have a gas-permeable metal support layer 2, a fuel electrode layer 3 provided on the metal support layer 2, an electrolyte layer 4 provided on the fuel electrode layer 3, and an air cathode layer 5 provided on the electrolyte layer 4. Each cell is configured so that fuel gas flows over the metal support layer 2.

[0067] However, in this embodiment, the metal support layer 2 does not necessarily have to include the first region 2-1 and the second region 2-2 in each cell. Instead, the exposed area of ​​the metal support layer differs between the first cell and the second cell. Specifically, the exposed area of ​​the metal support layer in the second cell is smaller than the exposed area of ​​the metal support layer in the first cell.

[0068] The above is the configuration of the solid oxide fuel cell stack 9 according to this embodiment. In this embodiment, during operation, fuel gas is first supplied to the first stack 9-1. The fuel gas is consumed in each of the first cells included in the first stack 9-1 and then sent to the second stack 9-2. The fuel gas sent to the second stack 9-2 is consumed in each of the second cells and then exhausted. Here, the water vapor concentration contained in the fuel gas is higher in the second stack located downstream than in the first stack located upstream. That is, the metal support layer included in the second cell is exposed to an environment with a higher water vapor concentration than the metal support layer in the first cell. However, the metal support layer in the second cell is less susceptible to oxidation because its exposed area is small. Therefore, deterioration of the metal support layer due to oxidation can be suppressed.

[0069] In this embodiment, the metal support layer included in the first cell corresponds to the first region 2-1 in the previously described embodiment, and the metal support layer included in the second cell corresponds to the second region 2-2 in the previously described embodiment. Therefore, the improvements regarding the first region 2-1 and the second region 2-2 described in the previously described embodiment can also be applied to the metal support layers included in the first cell and the second cell, respectively. For example, similar to the second region 2-2 in the previously described embodiment, the surface of the metal support layer included in the second cell may be covered with an antioxidant layer.

[0070] (5) Fifth embodiment Next, a fifth embodiment will be described. Note that detailed description will be omitted for the fact that the same configuration as the previously described embodiments can be adopted.

[0071] In the above-described embodiments, a "solid oxide fuel cell" has been described, whereas in this embodiment, a "solid oxide electrolysis cell" will be described.

[0072] Figure 5 is a schematic cross-sectional view showing a solid oxide electrolysis cell 10 according to this embodiment. This solid oxide electrolysis cell 10 basically has the same configuration as the solid oxide fuel cell of the first embodiment (see Figure 1). That is, the solid oxide electrolysis cell 10 has a metal support layer 2, a fuel electrode layer 3, an electrolyte layer 4, and a cathode layer 5. The metal support layer 2 also has a first region 2-1 and a second region 2-2 located downstream of the first region 2-1.

[0073] However, unlike the solid oxide fuel cell 1, the solid oxide electrolysis cell 10 is supplied with water vapor instead of fuel gas. The water vapor is supplied so as to flow over the metal support layer 2 in the direction of water vapor flow. Some of the water vapor is then supplied to the anode layer 3 via the metal support layer 2 and consumed, producing hydrogen and oxide ions. The oxide ions move through the electrolyte layer 4 to the cathode layer 5, where they are converted to oxygen. The water vapor concentration in the environment containing the metal support layer 2 increases upstream and decreases downstream. That is, in the solid oxide electrolysis cell 10, contrary to solid oxide fuel cells, the metal support layer 2 is more likely to oxidize upstream.

[0074] Therefore, in the present embodiment, the exposed area of ​​the first region 2-1 located on the upstream side of the metal support layer 2 is smaller than that of the second region 2-2 located on the downstream side. That is, the configurations of the first region 2-1 and the second region 2-2 are reversed compared to the previously described embodiments. The first region 2-1 located on the upstream side is configured to be less susceptible to oxidation than the second region 2-2 located on the downstream side. With this configuration, deterioration of the metal support layer 2 in the solid oxide electrolysis cell 10 is suppressed, as in the previously described embodiments.

[0075] Note that, in this embodiment, it is possible to make the same improvements as those described for the solid oxide fuel cell according to the previous embodiment. For example, in a preferred embodiment, an antioxidant layer 8 is provided in the first region 2-1, as shown in Fig. 5. The thickness of the antioxidant layer 8 in the first region 2-1 is preferably greater than the thickness in the second region 2-2.

[0076] Furthermore, as with the fourth embodiment, the principles of the solid oxide electrolysis cell 10 according to this embodiment can also be applied to the "stack." That is, it is also possible to adopt a configuration in which the "stack" of the solid oxide electrolysis cell includes a first stack having a first cell and a second stack having a second cell, and the exposed area of ​​the metal support layer included in the first cell is smaller than that of the second cell. Adoption of such a configuration also has an advantageous effect in preventing oxidation of the metal support layer 2.

[0077] (Addendum) Representative configurations included in the present invention and their effects are summarized below as appendices.

[0078] (Appendix 1) a fuel cell comprising: a gas-permeable metal support layer (2); an anode layer (3) provided on the metal support layer; an electrolyte layer (4) provided on the anode layer; and an air cathode layer (5) provided on the electrolyte layer; the anode layer has a porous structure; the metal support layer is configured so that a fuel gas flows over it in a fuel gas flow direction; the metal support layer has a first region (2-1) and a second region (2-2) provided downstream of the first region in the fuel gas flow direction; and the exposed area per unit volume of the second region is smaller than the exposed area per unit volume of the first region.

[0079] According to this configuration, in the second region exposed to high-concentration water vapor, the area of ​​the portion exposed to water vapor is small, so that deterioration of the metal support layer due to water vapor oxidation can be prevented.

[0080] (Appendix 2) 2. The solid oxide fuel cell according to claim 1, wherein the surface of the metal support layer in the second region is covered with an antioxidant layer 8.

[0081] According to this configuration, the antioxidant layer 8 can more reliably prevent oxidation of the metal support layer.

[0082] (Appendix 3) 3. The solid oxide fuel cell according to claim 2, wherein the thickness of the antioxidant layer in the second region is greater than the thickness of the antioxidant layer covering the surface of the first region.

[0083] With this configuration, the second region 2-2 can be made more resistant to oxidation.

[0084] (Appendix 4) 4. The solid oxide fuel cell according to claim 2 or 3, wherein the antioxidant layer in the second region contains at least one element selected from the group consisting of B, Na, Mg, Al, Si, K, Ca, Sc, Mn, Co, Ni, Cu, Zn, Y, Zr, Ru, Rh, Pd, Ba, Ir, Pt, Au, and Ce.

[0085] With this configuration, the second region 2-2 can be made more resistant to oxidation.

[0086] (Appendix 5) 5. The solid oxide fuel cell according to any one of claims 1 to 4, wherein the metal support layer comprises a metal sintered body having a porous structure.

[0087] With this configuration, it is possible to realize a metal support layer with high gas permeability.

[0088] (Appendix 6) A solid oxide fuel cell according to any one of appendices 1 to 4, wherein the metal support layer has a metal plate having through holes, and the number of through holes per unit area in the second region is smaller than the number of through holes per unit area in the first region.

[0089] With this configuration, the metal support layer 2 can be easily realized.

[0090] (Appendix 7) 7. The solid oxide fuel cell according to any one of claims 1 to 6, further comprising an anode electron-conducting layer 6 having a porous structure and disposed between the anode layer and the metal support layer.

[0091] With this configuration, anode electron conductive layer 6 can supply a sufficient amount of current required for the power generation reaction also downstream of anode layer 3. This can improve power generation efficiency.

[0092] (Appendix 8) 8. The solid oxide fuel cell according to claim 7, wherein the anode electron conductive layer contains at least one element selected from the group consisting of Ni, Pt, Ru, Rh, and Co.

[0093] With this configuration, it is possible to realize an anode electron conductive layer 6 with high electron conductivity.

[0094] (Appendix 9) a first stack (9-1) having a first cell; and a second stack (9-2) having a second cell, wherein the first cell and the second cell each have a gas-permeable metal support layer, an anode layer provided on the metal support layer, an electrolyte layer provided on the anode layer, and an air cathode layer provided on the electrolyte layer, wherein the first cell and the second cell are each configured to allow a fuel gas to flow over the metal support layer, the first stack and the second stack are connected so that the fuel gas discharged from the first stack is supplied to the second stack, and the exposed area per unit volume of the metal support layer of the second cell is smaller than the exposed area per unit volume of the metal support layer of the first cell.

[0095] According to this configuration, the metal support layer is configured to be resistant to oxidation in the second cell, which is exposed to an environment with a high water vapor concentration, and therefore oxidation of the metal support layer can be more effectively prevented.

[0096] (Appendix 10) A method for manufacturing a solid oxide fuel cell according to any one of appendices 1 to 5, comprising the steps of preparing a material for a first region to form the first region, preparing a material for a second region to form the second region, and forming a metal support layer using the material for the first region and the material for the second region.

[0097] According to this method, it is possible to manufacture a solid oxide fuel cell comprising a metal support layer having a first region and a second region.

[0098] (Appendix 11) A method for manufacturing a solid oxide fuel cell according to claim 6, comprising the steps of: preparing a metal plate; and forming through holes in the metal plate so that the first region and the second region are formed.

[0099] According to this method, it is possible to manufacture a solid oxide fuel cell comprising a metal support layer having a first region and a second region.

[0100] (Appendix 12) 1. A solid oxide electrolysis cell comprising: a gas-permeable metal support layer (2); an anode layer (3) provided on the metal support layer; an electrolyte layer (4) provided on the anode layer; and an air cathode layer (5) provided on the electrolyte layer, wherein the anode layer has a porous structure; the metal support layer is configured so that water vapor flows thereover in a water vapor flow direction; the metal support layer has a first region (2-1) and a second region (2-2) provided downstream of the first region in the water vapor flow direction; and the exposed area per unit volume of the first region (2-1) is smaller than the exposed area per unit volume of the second region (2-2).

[0101] According to this configuration, in the first region exposed to high concentration water vapor, the area of ​​the portion exposed to water vapor is small, so oxidation due to water vapor can be suppressed. [Explanation of symbols]

[0102] 1 Solid oxide fuel cell, 2 Metal support layer, 2-1 First region, 2-2 Second region, 3 Anode layer, 4 Electrolyte layer, 5 Cathode layer, 6 Anode electron conducting layer, 7 Metal sintered body, 8 Antioxidant layer, 9 Solid oxide fuel cell stack, 9-1 First stack, 9-2 Second stack, 10 Solid oxide electrolysis cell

Claims

1. a gas-permeable metal support layer; a fuel electrode layer provided on the metal support layer; an electrolyte layer provided on the fuel electrode layer; an air electrode layer provided on the electrolyte layer; Equipped with the fuel electrode layer has a porous structure, the metal support layer is configured so that fuel gas flows thereover in a fuel gas flow direction; The metal support layer is A first region; a second region provided downstream of the first region in the fuel gas flow direction, an exposed area per unit volume in the second region is smaller than an exposed area per unit volume in the first region; Solid oxide fuel cell.

2. The solid oxide fuel cell according to claim 1, the surface of the metal support layer in the second region is coated with an antioxidant layer; Solid oxide fuel cell.

3. 3. The solid oxide fuel cell according to claim 2, The thickness of the antioxidant layer in the second region is greater than the thickness of the antioxidant layer covering the surface of the first region. Solid oxide fuel cell.

4. 3. The solid oxide fuel cell according to claim 2, the antioxidant layer in the second region contains at least one element selected from the group consisting of B, Na, Mg, Al, Si, K, Ca, Sc, Mn, Co, Ni, Cu, Zn, Y, Zr, Ru, Rh, Pd, Ba, Ir, Pt, Au, and Ce; Solid oxide fuel cell.

5. 3. The solid oxide fuel cell according to claim 1 or 2, The metal support layer has a metal sintered body having a porous structure. Solid oxide fuel cell.

6. 3. The solid oxide fuel cell according to claim 1 or 2, the metal support layer includes a metal plate having a through hole; the number of the through holes per unit area in the second region is smaller than the number of the through holes per unit area in the first region; Solid oxide fuel cell.

7. 3. The solid oxide fuel cell according to claim 1 or 2, Furthermore, an anode electron conductive layer provided between the anode layer and the metal support layer and having a porous structure; Equipped with Solid oxide fuel cell.

8. The solid oxide fuel cell according to claim 7, the anode electron conductive layer contains at least one element selected from the group consisting of Ni, Pt, Ru, Rh, and Co; Solid oxide fuel cell.

9. a first stack having a first cell; a second stack having a second cell; Equipped with The first cell and the second cell each include: a gas-permeable metal support layer; a fuel electrode layer provided on the metal support layer; an electrolyte layer provided on the fuel electrode layer; an air electrode layer provided on the electrolyte layer; and The first cell and the second cell are each configured so that a fuel gas flows over the metal support layer, the first stack and the second stack are connected to each other so that fuel gas discharged from the first stack is supplied to the second stack; an exposed area per unit volume of the metal support layer of the second cell is smaller than an exposed area per unit volume of the metal support layer of the first cell; Solid oxide fuel cell stack.

10. 3. A method for producing a solid oxide fuel cell according to claim 1 or 2, comprising the steps of: preparing a first region material for forming the first region; preparing a second region material for forming the second region; forming the metal support layer using the material for the first region and the material for the second region; Equipped with Manufacturing method.

11. 7. A method for producing a solid oxide fuel cell according to claim 6, comprising the steps of: providing a metal plate; forming a through hole in the metal plate so that the first region and the second region are formed; Equipped with Manufacturing method.

12. a gas-permeable metal support layer; a fuel electrode layer provided on the metal support layer; an electrolyte layer provided on the fuel electrode layer; an air electrode layer provided on the electrolyte layer; Equipped with the fuel electrode layer has a porous structure, the metal support layer is configured so that water vapor flows thereover in a water vapor flow direction; The metal support layer is A first region; a second region provided downstream of the first region in the water vapor flow direction, an exposed area per unit volume in the first region is smaller than an exposed area per unit volume in the second region; Solid oxide electrolysis cell.

Images