fuel cells

Abstract

To provide a fuel battery of which manufacturing cost can be reduced while suppressing output drop.SOLUTION: A fuel battery comprises a membrane electrode gas diffusion layer assembly and a pair of separators arranged on both surfaces of the membrane electrode gas diffusion layer assembly, where the membrane electrode gas diffusion layer assembly comprises: an electrolyte membrane; an anode catalyst layer which is arranged on a surface on one side of the electrolyte membrane; a cathode catalyst layer which is arranged on a surface on the other side of the electrolyte membrane; an anode gas diffusion layer which is arranged on a surface on the opposite side to a surface on an electrolyte membrane side of the anode catalyst layer; and a cathode gas diffusion layer which is arranged on a surface on the opposite side to a surface on an electrolyte membrane side of the cathode catalyst layer, and the membrane electrode gas diffusion layer assembly further comprises iron foreign matter and cerium range which is arranged at a position overlapping the iron foreign matter in a lamination direction view, and the cerium range includes a cerium compound.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application relates to fuel cells.

Background Art

[0002] A fuel cell is a device that generates electricity by causing an electrochemical reaction between a fuel gas (e.g., hydrogen) and an oxidant gas (e.g., air).

[0003] A fuel cell is manufactured by disposing a pair of separators on both sides of a membrane electrode assembly (MEA: Membrane Electrode Assembly) in which a pair of catalyst layers are joined to both sides of a solid electrolyte membrane. In addition, in order to improve the diffusibility of the reaction gas (fuel gas and oxidant gas), a fuel cell is also manufactured in which a pair of separators are disposed on both sides of a membrane electrode gas diffusion layer assembly (MEGA: Membrane Electrode Gasdiffusionlayer Assembly) in which gas diffusion layers are further joined to both sides of the membrane electrode assembly.

[0004] During the manufacture of a fuel cell, iron foreign matter may be mixed into the membrane electrode assembly or the membrane electrode gas diffusion layer assembly. The iron foreign matter dissolves as iron ions in the fuel cell and also diffuses into the electrolyte membrane. A fuel cell also generates H2O2 (hydrogen peroxide) as a side reaction during power generation. Iron ions promote the generation of highly active oxygen species such as OH radicals from H2O2. Then, the reaction of this active oxygen with the electrolyte membrane accelerates the deterioration of the electrolyte membrane. Specifically, the electrolyte membrane undergoes membrane swelling.

[0005] To address these problems, a technique has been disclosed for adding cerium compounds, which have the effect of suppressing reactive oxygen species, to fuel cells. For example, Patent Document 1 discloses a fuel cell membrane electrode assembly in which the polymer electrolyte membrane contains cerium cations. Patent Document 2 also discloses a polymer electrolyte fuel cell in which Ag@CeO2 particles (particles having a core-shell structure in which the surface of the Ag core is coated with CeO2) are added to one or more of the group consisting of an electrolyte membrane, an anode-side catalyst layer, and a cathode-side catalyst layer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2009-514172 [Patent Document 2] Japanese Patent Publication No. 2019-114371 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The thinning of the electrolyte membrane is accelerated by an increase in the amount of iron ions, i.e., the amount of iron impurities. In conventional technology, the amount of cerium added to the fuel cell corresponded to the expected maximum amount of iron impurities. Therefore, a decrease in fuel cell output due to the addition of large amounts of cerium was a problem. In addition, there was the problem of increased costs due to the addition of large amounts of cerium.

[0008] Therefore, the main purpose of this disclosure is to provide a fuel cell that can reduce manufacturing costs while suppressing power output degradation, in light of the above circumstances. [Means for solving the problem]

[0009] This disclosure provides a fuel cell, as one embodiment for solving the above problems, comprising a membrane electrode gas diffusion layer assembly and a pair of separators disposed on both sides of the membrane electrode gas diffusion layer assembly, wherein the membrane electrode gas diffusion layer assembly comprises an electrolyte membrane, an anode catalyst layer disposed on one side of the electrolyte membrane, a cathode catalyst layer disposed on the other side of the electrolyte membrane, an anode gas diffusion layer disposed on the side of the anode catalyst layer opposite to the electrolyte membrane side, and a cathode gas diffusion layer disposed on the side of the cathode catalyst layer opposite to the electrolyte membrane side, and the membrane electrode gas diffusion layer assembly further comprises iron foreign matter and a cerium region disposed at a position overlapping with the iron foreign matter in a view in the stacking direction, the cerium region containing a cerium compound. [Effects of the Invention]

[0010] The fuel cell described herein can reduce manufacturing costs while suppressing power output degradation. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view of a fuel cell 100, which is one embodiment of the device. [Figure 2] This is a flowchart of a fuel cell manufacturing method, which is one embodiment of the process. [Figure 3] (a) This figure shows the process of performing an X-ray inspection on a membrane electrode gas diffusion layer assembly M. (b) This figure shows the detection and identification of an iron foreign object F by X-ray inspection. [Figure 4] This figure shows how the cerium region S is positioned in a location that overlaps with the iron foreign material F when viewed in the stacking direction. [Modes for carrying out the invention]

[0012] [Fuel cell] The fuel cell of this disclosure will be described using a fuel cell 100, which is one embodiment. Figure 1 shows a schematic cross-sectional view of the fuel cell 100.

[0013] One embodiment is a fuel cell 100 including a membrane electrode gas diffusion layer assembly 10 and a pair of separators 20 (21, 22) respectively disposed on both surfaces of the membrane electrode gas diffusion layer assembly 10. The membrane electrode gas diffusion layer assembly 10 includes an electrolyte membrane 11, an anode catalyst layer 12a disposed on one surface of the electrolyte membrane 11, a cathode catalyst layer 12b disposed on the other surface of the electrolyte membrane 11, an anode gas diffusion layer 13a disposed on a surface of the anode catalyst layer 12a opposite to the electrolyte membrane 11 side, and a cathode gas diffusion layer 13b disposed on a surface of the cathode catalyst layer 12b opposite to the electrolyte membrane 11 side. The membrane electrode gas diffusion layer assembly 10 further includes an iron foreign matter 14 and a cerium region 15 disposed at a position overlapping the iron foreign matter 14 in a stacking direction view, and the cerium region 15 contains a cerium compound.

[0014] <Membrane electrode gas assembly 10> The membrane electrode gas diffusion layer assembly 10 includes an electrolyte membrane 11, a cathode catalyst layer 12a, an anode catalyst layer 12b, an anode gas diffusion layer 13a, a cathode gas diffusion layer 13b, an iron foreign matter 14, and a cerium region 15.

[0015] (Electrolyte membrane 11) The electrolyte membrane 11 is an ion exchange membrane having a polymer membrane with ion conductivity as an electrolyte, and can selectively allow only protons to pass among electrons and protons generated by an electrochemical reaction. Such an electrolyte membrane 11 can be appropriately selected from known electrolyte membranes applicable to fuel cells. For example, a fluorine-based electrolyte or a carbon-based electrolyte can be mentioned. Examples of the fluorine-based electrolyte include polytetrafluoroethylene (PTFE) and perfluorosulfonic acid ionomer.

[0016] (Anode catalyst layer 12a) The anode catalyst layer 12a is disposed on one side surface of the electrolyte membrane 11. The anode catalyst layer 12a contains a catalyst or a catalyst supported on a single substance. The catalyst is not particularly limited as long as it is applicable to a fuel cell. For example, platinum, platinum alloys, and the like can be mentioned. Examples of the carrier for supporting the catalyst include carbon particles. Further, the anode catalyst layer 12a may contain an electrolyte having proton conductivity. For example, an electrolyte applicable to the electrolyte membrane 11 can be mentioned.

[0017] The method for forming the anode catalyst layer 12a is not particularly limited, but generally, the anode catalyst layer 12a can be formed by applying a catalyst ink in which the materials constituting the anode catalyst layer 12a are dissolved or dispersed in a solvent to the electrolyte membrane. Such a method for forming the anode catalyst layer 12a is known.

[0018] (Cathode catalyst layer 12b) The cathode catalyst layer 12b is disposed on the other side surface of the electrolyte membrane 11. The cathode catalyst layer 12b contains a catalyst or a catalyst supported on a single substance. The catalyst is not particularly limited as long as it is applicable to a fuel cell. For example, platinum, platinum alloys, and the like can be mentioned. Examples of the carrier for supporting the catalyst include carbon particles. Further, the cathode catalyst layer 12b may contain an electrolyte having proton conductivity. For example, an electrolyte applicable to the electrolyte membrane 11 can be mentioned.

[0019] The method for forming the cathode catalyst layer 12b is not particularly limited, but generally, the cathode catalyst layer 12b can be formed by applying a catalyst ink in which the materials constituting the cathode catalyst layer 12b are dissolved or dispersed in a solvent to the electrolyte membrane. Such a method for forming the cathode catalyst layer 12b is known.

[0020] (Anode gas diffusion layer 13a) The anode gas diffusion layer 13a is positioned on the side of the anode catalyst layer 12a opposite to the side facing the electrolyte membrane 11. The anode gas diffusion layer 13a is a component that exchanges electrons generated by the electrochemical reaction and supplies fuel gas to the anode catalyst layer 12a. The material of the anode gas diffusion layer 13a is not particularly limited as long as it is a material applicable to fuel cells. Examples include gas-permeable conductive members such as carbon porous materials like carbon paper or carbon cloth, or metal porous materials like metal mesh or foamed metal.

[0021] (Cathode gas diffusion layer 13b) The cathode gas diffusion layer 13b is positioned on the side of the cathode catalyst layer 12b opposite to the side facing the electrolyte membrane 11. The cathode gas diffusion layer 13b is a component that exchanges electrons generated by the electrochemical reaction and supplies oxidizing gas to the cathode catalyst layer 12b. The material of the cathode gas diffusion layer 13b is not particularly limited as long as it is a material applicable to fuel cells. Examples include gas-permeable conductive members such as carbon porous materials like carbon paper or carbon cloth, or metal porous materials like metal mesh or foamed metal.

[0022] (Iron foreign object 14) The iron foreign matter 14 is a foreign substance containing iron and can be introduced during the manufacturing of the membrane electrode gas diffusion layer assembly 10. Therefore, the iron foreign matter 14 can be introduced into any layer of the membrane electrode gas diffusion layer assembly. Accordingly, the iron foreign matter 14 can be included in at least one of the electrolyte 11, anode catalyst layer 12a, cathode catalyst layer 12b, anode gas diffusion layer 13a, and cathode gas diffusion layer 13b. The number of iron foreign matter 14 introduced may be at least one, or it may be multiple.

[0023] Iron foreign matter 14 is mainly composed of iron, but may contain components other than iron. The size of iron foreign matter 14 is not particularly limited, but since iron foreign matter 14 that can be detected by visual inspection can be easily removed during manufacturing, typically iron foreign matter 14 is often too large to be easily removed by visual inspection.

[0024] Iron foreign matter 14 mixed into the membrane electrode gas diffusion layer assembly 10 can be detected by an X-ray measuring device or the like. Furthermore, the location of the iron foreign matter 14 can be identified from the measurement results.

[0025] (Cerium region 15) The cerium region 15 is positioned in a location that overlaps with the iron foreign matter 14 when viewed in the stacking direction of the membrane electrode gas diffusion layer assembly 10. Specifically, it is positioned on at least one surface of the electrolyte 11, anode catalyst layer 12a, cathode catalyst layer 12b, anode gas diffusion layer 13a, and cathode gas diffusion layer 13b, in a location that overlaps with the iron foreign matter 14 when viewed in the stacking direction. The cerium region 15 may also be directly placed on the iron foreign matter 14. Of these layers, from the viewpoint of simplifying the manufacturing process, the cerium region 15 may be placed on the anode gas diffusion layer 13a or the cathode gas diffusion layer 13b.

[0026] "Positions overlapping with the iron foreign matter 14 in the stacking direction view" refers to positions that overlap with at least a portion of the iron foreign matter 14 in the stacking direction view. From the viewpoint of enhancing the reactive oxygen species scavenging effect and reducing the amount of cerium compound added, it may also be a position that overlaps with the entire iron foreign matter 14. When the iron foreign matter 14 is located on the anode side, it may be placed on the surface of the electrolyte membrane 11 on the anode catalyst layer 12a side, on the surface of the anode catalyst layer 12a, or on the surface of the anode gas diffusion layer 12a. When the iron foreign matter 14 is located on the cathode side, it may be placed on the surface of the electrolyte membrane 11 on the cathode catalyst layer 12b side, on the surface of the cathode catalyst layer 12b, or on the surface of the cathode diffusion layer 13b.

[0027] At least one cerium region 15 is required to be located in the membrane electrode gas diffusion layer assembly 10. If multiple iron foreign matter 14 is present, the cerium region 15 may be located at a position corresponding to each iron foreign matter 14. Also, one cerium region 15 and multiple iron foreign matter 14 may overlap when viewed in the stacking direction.

[0028] The cerium region 15 includes cerium compounds. The cerium compounds are not particularly limited, but examples include cerium oxide (CeO2), cerium fluoride (CeF3), cerium hydroxide (Ce(OH)4), and cerium carbonate (Ce2(CO3)3). Cerium oxide is preferred.

[0029] The shape of the cerium region 15 is not particularly limited and may be polygonal, circular, or elliptical. Circular is preferred. The size of the cerium region 15 is not particularly limited. For example, it may be 10% or less, 5% or less, 2% or less, 0.1% or more, 0.5% or more, or 1% or more of the surface area on which the cerium region 15 is placed. Alternatively, the size of the cerium region 15 may be 5 mm or more, 10 mm or more, 50 mm or less, 30 mm or less, or 20 mm or less. The size of the cerium region 15 refers to the length of the longer side of the rectangle circumscribing the cerium region.

[0030] The amount of cerium compound added to cerium region 15 is not particularly limited; even a small amount of cerium compound will produce an reactive oxygen species scavenging effect. From the perspective of further improving the effect, the amount of cerium compound added per unit area in cerium region 15 is 5 μg / cm². 2 The above is also acceptable, or 10 μg / cm³. 2 The above is also acceptable, at 20 μg / cm³. 2 The above is also acceptable, 30 μg / cm³ 2 The above is also acceptable, 100 μg / cm³ 2 The following is also acceptable: 80 μg / cm³ 2 The following is also acceptable: 60 μg / cm³ 2 The following is also acceptable: 50 μg / cm³ 2 The following is also acceptable.

[0031] The cerium region 15 may be formed simply by placing a cerium compound on the surface, or by coating the surface with a solution (cerium solution) in which a cerium compound is dissolved in a solvent. When using a cerium solution, the volume concentration (v / v%) of the cerium compound in the solution is not particularly limited, but may be, for example, 0.1% or more, 0.5% or more, 1% or more, 10% or less, 5% or less, or 3% or less. The type of solvent is not particularly limited as long as it can dissolve the cerium compound. Examples include water, alcohol, ether, ketone, ester, etc. Water is preferred. The method of adding the solution to the surface is not particularly limited, but for example, the solution may be added to the surface so that the thickness is about 5 μm.

[0032] <Separator 20> The separator 20 is a conductive plate-shaped member. The separator 20 is not particularly limited as long as it is used in a fuel cell. For example, a carbon separator made of a composite material with a high concentration of carbon fibers and resin, or a metal separator made of a metal material can be used. Examples of metal separators include those made of a metal material with excellent corrosion resistance, or those coated with a coating that enhances corrosion resistance by covering the surface with carbon or a metal material with excellent corrosion resistance.

[0033] A pair of separators 20 consists of an anode separator 21 and a separator cathode 22. The anode separator 21 is located on the surface of the anode gas diffusion layer 13a opposite to the anode catalyst layer 12a, and the cathode separator 22 is located on the surface of the cathode gas diffusion layer 13b opposite to the cathode catalyst layer 12b. Generally, the anode separator 21 has a fuel gas channel 21a formed on the surface facing the anode gas diffusion layer 13a, and a refrigerant channel (not shown) formed on the surface opposite to the anode gas diffusion layer 13a. Also generally, the cathode separator 22 has an oxidizer gas channel 22a formed on the surface facing the cathode gas diffusion layer 13b, and a refrigerant channel (not shown) formed on the surface opposite to the cathode gas diffusion layer 13b.

[0034] <Mechanism and Effects> Electricity generation by the fuel cell 100 is carried out as follows: Fuel gas and oxidizer gas are supplied to the fuel cell 100 from an external source. The fuel gas supplied to the fuel cell 100 passes through the fuel gas flow path 21a of the anode separator 21, is diffused by the anode gas diffusion layer 13a, and reaches the anode catalyst layer 12a. The oxidizer gas supplied to the fuel cell 100 passes through the oxidizer gas flow path 22a of the cathode separator 22, is diffused by the cathode gas diffusion layer 13b, and reaches the cathode catalyst layer 12b. Electrochemical reactions occur in each catalyst layer, generating electricity and producing water. The generated water is discharged to the outside through the fuel gas flow path 21a or the oxidizer gas flow path 22a. Although the temperature of the fuel cell 100 rises due to power generation, it is cooled by the refrigerant (cooling water or cooling gas, etc.) supplied to the refrigerant flow paths of each separator 20, and maintained at an appropriate temperature.

[0035] In this case, if iron foreign matter 14 is present in the fuel cell 100, the generation of reactive oxygen species is promoted by iron ions dissolved by the generated water, etc. However, the fuel cell 100 has a cerium region 15 located in a position that overlaps with the iron foreign matter 14 when viewed in the stacking direction. Since the cerium region 15 contains a cerium compound, it dissolves as cerium ions within the fuel cell 100. The dissolved cerium ions easily penetrate in the stacking direction. Through penetration, a cerium ion concentration sufficient to remove reactive oxygen species can be secured. Therefore, even if iron foreign matter 14 (iron ions) is present in the fuel cell 100, reactive oxygen species can be sufficiently removed.

[0036] Conventional technology did not identify the location of iron impurities, but instead added an amount of cerium corresponding to the maximum expected amount of iron impurities to the fuel cell to remove the generated reactive oxygen species. However, the problem was that adding large amounts of cerium reduced the output of the fuel cell and increased costs.

[0037] In contrast, the fuel cell 100 solves the problem caused by reactive oxygen species by arranging cerium regions 15 in a spot-like manner at positions corresponding to the iron foreign matter 14 in the stacking direction. As a result, the amount of cerium compound added can be reduced compared to conventional technology, and the harmful effects of adding a large amount of cerium compound are suppressed. Therefore, the fuel cell 100 can reduce manufacturing costs while suppressing power output degradation.

[0038] Furthermore, the proportion of iron foreign matter 14 is only a few per 100 fuel cell cells, and in most cases, there is only one iron foreign matter 14 per surface. Therefore, by inspecting for iron foreign matter 14 and adding the cerium compound only to the membrane electrode gas diffusion layer assemblies where iron foreign matter 14 is present, the amount of cerium compound used can be reduced, and manufacturing costs can be further lowered.

[0039] Furthermore, conventionally, cells containing iron foreign matter 14 were discarded, but by arranging the cerium region 15 as in the fuel cell 100, cells containing iron foreign matter 14 can also be used, thereby further reducing costs.

[0040] [Method of manufacturing a fuel cell] The method for manufacturing a fuel cell according to this disclosure will be described using one embodiment. Figure 2 shows a flowchart of the method for manufacturing a fuel cell according to one embodiment.

[0041] One embodiment is a method for manufacturing a fuel cell including a membrane electrode gas diffusion layer assembly and a pair of separators disposed on both sides of the membrane electrode gas diffusion layer assembly, the method including: a step of manufacturing a membrane electrode gas diffusion layer assembly (MEGA manufacturing step S1) including an electrolyte membrane, an anode catalyst layer disposed on one surface of the electrolyte membrane, a cathode catalyst layer disposed on the other surface of the electrolyte membrane, an anode gas diffusion layer disposed on a surface opposite to the electrolyte membrane side surface of the anode catalyst layer, and a cathode gas diffusion layer disposed on a surface opposite to the electrolyte membrane side surface of the cathode catalyst layer; a step of inspecting whether the membrane electrode gas diffusion layer assembly contains iron foreign matter (inspection step S2); a step of disposing a cerium region at a position overlapping the iron foreign matter of the membrane electrode gas diffusion layer assembly in a stacking direction view when iron foreign matter is detected in the inspection step (cerium region disposition step S3); and a step of disposing separators on both sides of the membrane electrode gas diffusion layer assembly (separator disposition step S4), wherein the cerium region contains a cerium compound.

[0042] <MEGA manufacturing step S1> The MEGA manufacturing step S1 is a step of manufacturing a membrane electrode gas diffusion layer assembly (MEGA) including an electrolyte membrane, an anode catalyst layer disposed on one surface of the electrolyte membrane, a cathode catalyst layer disposed on the other surface of the electrolyte membrane, an anode gas diffusion layer disposed on a surface opposite to the electrolyte membrane side surface of the anode catalyst layer, and a cathode gas diffusion layer disposed on a surface opposite to the electrolyte membrane side surface of the cathode catalyst layer.

[0043] For example, the membrane electrode gas diffusion layer assembly can be manufactured as follows. First, a catalyst ink containing components of the anode catalyst layer is applied to one surface of the electrolyte membrane and dried, thereby bonding the anode catalyst layer to the electrolyte membrane. Next, a catalyst ink containing components of the cathode catalyst layer is applied to the other surface of the electrolyte membrane and dried, thereby bonding the cathode catalyst layer to the electrolyte membrane. Subsequently, the anode gas diffusion layer is disposed on a surface opposite to the electrolyte membrane side surface of the anode catalyst layer, and the cathode gas diffusion layer is disposed on a surface opposite to the electrolyte membrane side surface of the cathode catalyst layer. Thereby, the membrane electrode gas diffusion layer assembly can be manufactured.

[0044] The above method for fabricating the membrane electrode gas diffusion layer assembly is just one example, and other methods may be used to fabricate the membrane electrode gas diffusion layer assembly.

[0045] <Inspection process S2> Inspection step S2 is a step to inspect whether or not the membrane electrode gas diffusion layer assembly produced in step S1 contains iron foreign matter. For example, an X-ray measuring device can be used to inspect for iron foreign matter. By using an X-ray measuring device, it is possible to detect iron foreign matter and also identify its location. The location of the iron foreign matter is at least the location in the planar direction of the membrane electrode gas diffusion layer assembly in which the iron foreign matter is contained. The location in both the planar direction and the thickness direction of the membrane electrode gas diffusion layer assembly in which the iron foreign matter is contained may also be identified.

[0046] Figure 3 shows the detection and location of iron foreign matter F when an X-ray inspection is performed on the membrane electrode gas diffusion layer assembly M. In Figure 3, the iron foreign matter F was mixed inside the membrane electrode gas diffusion layer assembly M, and its location is indicated by a dotted line.

[0047] <Cerium area placement process S3> The cerium region placement step S3 is performed when iron foreign matter is detected in the inspection step S2, and involves placing a cerium region at a position that overlaps with the iron foreign matter in the film electrode gas diffusion layer assembly when viewed in the stacking direction. The method for placing the cerium region has been described above, so it will not be explained here.

[0048] Figure 4 shows how the cerium region S is positioned to overlap the iron foreign matter F detected in Figure 3. In this embodiment, the cerium region S is positioned in a spot-like manner. Note that in Figure 4, the cerium region S is positioned on the surface of the gas diffusion layer.

[0049] <Separator placement process S4> The separator placement step S4 is performed after the inspection step S2 or the cerium region placement step S3, and is a step of placing separators on both sides of the membrane electrode gas diffusion layer assembly. The method of placing the separators is not particularly limited and can be carried out by known methods. For example, the membrane electrode gas diffusion layer assembly may be placed inside a frame-shaped member, separators may be placed on both sides thereof, and the frame-shaped member and the separators may be bonded together.

[0050] Based on the above, the fuel cell of this disclosure can be manufactured.

Claims

[Claim 1] A fuel cell comprising a membrane electrode gas diffusion layer assembly and a pair of separators disposed on both sides of the membrane electrode gas diffusion layer assembly, The membrane electrode gas diffusion layer assembly comprises an electrolyte membrane, an anode catalyst layer disposed on one side of the electrolyte membrane, a cathode catalyst layer disposed on the other side of the electrolyte membrane, an anode gas diffusion layer disposed on the side of the anode catalyst layer opposite to the side facing the electrolyte membrane, and a cathode gas diffusion layer disposed on the side of the cathode catalyst layer opposite to the side facing the electrolyte membrane. Equipped with, The aforementioned film electrode gas diffusion layer assembly further comprises an iron foreign material and a cerium region positioned to overlap with the entire iron foreign material in a view in the stacking direction, The cerium region includes a cerium compound. The size of the cerium region is 0.1% or more and 10% or less of the surface area on which the cerium region is placed. The amount of cerium compound added per unit area in the cerium region is 5 μg / cm² or more and 100 μg / cm² or less. fuel cell.

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