Electrode structure

Abstract

To provide a technique which can suppress variations in an effective region acting as an electrode even when the accuracy of formation ranges of catalyst layers is low.SOLUTION: An outer peripheral edge of a first gas diffusion layer 62 is positioned inside an outer peripheral edge of a porous transport layer 72, an outer peripheral edge of a first catalyst layer 61, and an outer peripheral edge of a second catalyst layer 71. In this way, an effective region A of the first catalyst layer 61 and the second catalyst layer 71 can be defined by the first gas diffusion layer 62. Therefore, variations in the effective region A acting as an electrode can be suppressed even when the accuracy of formation ranges of the first catalyst layer 61 and the second catalyst layer 71 is low.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an electrode structure. [Background technology]

[0002] Conventionally, a polymer electrolyte water electrolysis device is known that produces hydrogen (H2) by electrolyzing water (H2O). The polymer electrolyte water electrolysis device has a cell stack in which cells and separators are alternately stacked. Each cell has an electrolyte membrane and a catalyst layer formed on both sides of the electrolyte membrane. When the polymer electrolyte water electrolysis device is in use, a voltage is applied between the anode-side catalyst layer and the cathode-side catalyst layer, and water is supplied to the anode-side catalyst layer. This causes the following electrochemical reaction between the anode-side catalyst layer and the cathode-side catalyst layer. As a result, hydrogen is discharged from the cathode-side catalyst layer. (Anode side) 2H2O → 4H + + O2+ 4e - (Cathode side) 2H + + 2e - → H2

[0003] A conventional solid polymer water electrolysis apparatus is described in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-023996 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional solid polymer water electrolysis devices, the entire catalyst layer is used as an electrode. However, when the entire catalyst layer is used as an electrode, if the accuracy of the area in which the catalyst layer is formed relative to the electrolyte membrane is low, the effective area that actually acts as an electrode varies. Moreover, the same problem can occur not only in cells of solid polymer water electrolysis devices but also in cells of solid polymer fuel cells.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a technology that can suppress variations in the effective area that acts as an electrode even when the precision of the formation range of the catalyst layer is low. [Means for solving the problem]

[0007] In order to solve the above problems, a first invention of the present application is an electrode structure comprising an electrolyte membrane, a first catalyst layer formed on one side of the electrolyte membrane, a first gas diffusion layer laminated on a surface of the first catalyst layer, a second catalyst layer formed on the other side of the electrolyte membrane, and a porous transport layer or a second gas diffusion layer laminated on the surface of the second catalyst layer, wherein the outer peripheral edge of the first gas diffusion layer is located inside the outer peripheral edge of the porous transport layer or second gas diffusion layer, the outer peripheral edge of the first catalyst layer, and the outer peripheral edge of the second catalyst layer.

[0008] A second invention of the present application is an electrode structure of the first invention, wherein the first catalyst layer and the second catalyst layer have an overlapping region where they overlap each other when viewed in the stacking direction, the outer periphery of the first catalyst layer and the outer periphery of the second catalyst layer are misaligned, and the outer periphery of the first gas diffusion layer is located inside the outer periphery of the overlapping region.

[0009] The third invention of the present application is an electrode structure of the first or second invention, wherein, when viewed in the stacking direction, the first gas diffusion layer is rectangular, and all four sides of the outer periphery of the first gas diffusion layer are located inside the outer periphery of the porous transport layer or second gas diffusion layer, the outer periphery of the first catalyst layer, and the outer periphery of the second catalyst layer.

[0010] A fourth invention of the present application is an electrode structure comprising an electrolyte membrane, a first catalyst layer formed on one side of the electrolyte membrane, a first gas diffusion layer laminated on a surface of the first catalyst layer, a second catalyst layer formed on the other side of the electrolyte membrane, and a second gas diffusion layer laminated on the surface of the second catalyst layer, wherein the outer peripheral edge of the second gas diffusion layer is located inside the outer peripheral edge of the first gas diffusion layer, the outer peripheral edge of the first catalyst layer, and the outer peripheral edge of the second catalyst layer.

[0011] A fifth invention of the present application is an electrode structure of the fourth invention, wherein the first catalyst layer and the second catalyst layer have an overlapping region where they overlap each other when viewed in the stacking direction, the outer periphery of the first catalyst layer and the outer periphery of the second catalyst layer are misaligned, and the outer periphery of the second gas diffusion layer is located inside the outer periphery of the overlapping region.

[0012] The sixth invention of the present application is an electrode structure of the fourth or fifth invention, wherein, when viewed in the stacking direction, the second gas diffusion layer is rectangular, and all four sides of the outer periphery of the second gas diffusion layer are located inside the outer periphery of the first gas diffusion layer, the outer periphery of the first catalyst layer, and the outer periphery of the second catalyst layer.

[0013] A seventh aspect of the present invention is the electrode structure according to any one of the first to sixth aspects, wherein the first catalyst layer and the second catalyst layer are coating films. Effect of the Invention

[0014] According to the first to seventh aspects of the present invention, the first gas diffusion layer or the second gas diffusion layer defines the effective areas of the first and second catalyst layers, thereby making it possible to suppress variation in the effective areas acting as electrodes even if the precision of the formation ranges of the first and second catalyst layers is low.

[0015] In particular, according to the second aspect of the present invention, the first gas diffusion layer can define the effective areas of the first and second catalyst layers regardless of the positional misalignment between the first and second catalyst layers.

[0016] In particular, according to the third aspect of the present invention, the rectangular effective areas of the first catalyst layer and the second catalyst layer can be precisely defined by the first gas diffusion layer.

[0017] In particular, according to the fifth aspect of the present invention, the second gas diffusion layer can define the effective areas of the first and second catalyst layers regardless of the positional misalignment between the first and second catalyst layers.

[0018] In particular, according to the sixth aspect of the present invention, the rectangular effective areas of the first catalyst layer and the second catalyst layer can be precisely defined by the second gas diffusion layer. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram of a water electrolysis device. [Diagram 2] FIG. 2 is a schematic diagram of one cell and a pair of separators located on either side of the cell. [Diagram 3] FIG. 2 is a view of the electrode structure as viewed in the stacking direction from the anode side. [Figure 4] FIG. 2 is a cross-sectional view of an electrode structure. [Diagram 5] FIG. 11 is a cross-sectional view of an electrode structure according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] <1. Overview of water electrolysis equipment> FIG 1 is a schematic diagram of a water electrolysis apparatus 1. The water electrolysis apparatus 1 is an apparatus for producing hydrogen by solid polymer water electrolysis. As shown in FIG 1, the water electrolysis apparatus 1 includes a cell stack 30 including a plurality of cells 10 and a plurality of separators 20, and a power source 40. The cells 10 and the separators 20 are alternately stacked to form the cell stack 30. Hereinafter, the direction in which the cells 10 and the separators 20 are stacked is referred to as the "stacking direction".

[0022] 2 is a schematic diagram illustrating only one cell 10 and a pair of separators 20 located on either side of the cell 10 in the cell stack 30 of the water electrolysis device 1. As shown in FIG. 2, one cell 10 has an electrolyte membrane 51, a first catalyst layer 61, a first gas diffusion layer 62, a second catalyst layer 71, and a porous transport layer 72.

[0023] A laminate constituted by the electrolyte membrane 51, the first catalyst layer 61, the first gas diffusion layer 62, the second catalyst layer 71, and the porous transport layer 72 is called a membrane-electrode-assembly (MEA). Also, a laminate constituted by the electrolyte membrane 51, the first catalyst layer 61, and the second catalyst layer 71 is called a catalyst-coated membrane (CCM).

[0024] The electrolyte membrane 51 is a thin film (ion exchange membrane) having ion conductivity. The electrolyte membrane 51 of the present embodiment is a thin film that exchanges hydrogen ions (H + ) is a proton exchange membrane that conducts a current. A fluorine-based or hydrocarbon-based polymer electrolyte membrane is used for the electrolyte membrane 51. Specifically, for example, a polymer electrolyte membrane containing perfluorocarbon sulfonic acid is used for the electrolyte membrane 51. The thickness of the electrolyte membrane 51 is, for example, 5 μm to 200 μm.

[0025] The first catalyst layer 61 is a catalyst layer that causes an electrochemical reaction on the cathode side. The first catalyst layer 61 is formed on the cathode side surface of the electrolyte membrane 51. The first catalyst layer 61 includes a large number of carbon particles carrying catalyst particles. The catalyst particles are, for example, platinum particles. However, the catalyst particles may be platinum particles mixed with trace amounts of ruthenium or cobalt particles. When the water electrolysis device 1 is in use, hydrogen ions (H + ) and electrons (e - ) is supplied. A voltage is applied between the first catalyst layer 61 and the second catalyst layer 71 by the power source 40. Then, a reduction reaction occurs in the first catalyst layer 61 due to the voltage and the action of the catalyst particles, and hydrogen gas (H2) is generated from the hydrogen ions and electrons.

[0026] The first gas diffusion layer 62 is a layer for transmitting electrons from the separator 20 to the first catalyst layer 61 and transmitting hydrogen generated in the first catalyst layer 61 to the separator 20. The first gas diffusion layer 62 is laminated on the outer surface of the first catalyst layer 61 (the surface opposite to the electrolyte membrane 51). The first catalyst layer 61 is sandwiched between the electrolyte membrane 51 and the first gas diffusion layer 62. The first gas diffusion layer 62 is made of a conductive and porous material. For example, a porous substrate made of carbon (carbon paper) is used for the first gas diffusion layer 62.

[0027] The second catalyst layer 71 is a catalyst layer that causes an electrochemical reaction on the anode side. The second catalyst layer 71 is formed on the anode side surface of the electrolyte membrane 51 (the surface opposite to the first catalyst layer 61). The second catalyst layer 71 contains a large number of catalyst particles. The catalyst particles are, for example, iridium oxide (IrOx), platinum (Pt), an alloy of iridium (Ir) and ruthenium (Ru), or an alloy of iridium (Ir) and titanium dioxide (TiO2). When the water electrolysis device 1 is in use, water (H2O) is supplied to the second catalyst layer 71. Then, a voltage is applied between the first catalyst layer 61 and the second catalyst layer 71 by the power source 40. Then, due to the action of the voltage and the catalyst particles, the water is converted into hydrogen ions (H + ), oxygen (O2), and electrons (e - ) is electrolyzed into

[0028] The porous transport layer 72 is a layer for uniformly supplying water to the second catalyst layer 71 and transporting oxygen and electrons generated in the second catalyst layer 71 to the separator 20. The porous transport layer 72 is laminated on the outer surface of the second catalyst layer 71 (the surface opposite to the electrolyte membrane 51). The second catalyst layer 71 is sandwiched between the electrolyte membrane 51 and the porous transport layer 72. The porous transport layer 72 is made of a conductive and porous material. For example, a porous substrate made of a metal such as titanium or stainless steel is used for the porous transport layer 72.

[0029] The separator 20 is a layer that transfers electrons between adjacent cells 10 and forms paths for water, oxygen, and hydrogen. The separator 20 is interposed between the first gas diffusion layer 62 and the porous transport layer 72 of adjacent cells 10. The separator 20 is formed of a metal plate 21 that is electrically conductive and impermeable to gases and liquids. The metal plate 21 has a cathode surface 22 in contact with the first gas diffusion layer 62 and an anode surface 23 in contact with the porous transport layer 72.

[0030] The metal plate 21 has a plurality of cathode grooves 24 on the cathode surface 22. Hydrogen produced in the first catalyst layer 61 passes through the first gas diffusion layer 62 and the cathode grooves 24 of the separator 20, and is discharged to the outside.

[0031] The metal plate 21 also has a plurality of anode grooves 25 on the anode surface 23. Water passes through the anode grooves 25 of the separator 20 and is supplied to the porous transport layer 72. Oxygen generated in the second catalyst layer 71 passes through the porous transport layer 72 and passes through the anode grooves 25 of the separator 20 to be discharged to the outside.

[0032] The power supply 40 is a device that applies a voltage to the above-mentioned cell stack 30. As shown in Fig. 1, a positive terminal of the power supply 40 is electrically connected to the separator 20 located at the end of the cell stack 30 closest to the anode side. A negative terminal of the power supply 40 is electrically connected to the separator 20 located at the end of the cell stack 30 closest to the cathode side. The power supply 40 applies a voltage required for water electrolysis to the cell stack 30.

[0033] When the water electrolysis device 1 is in use, water is supplied from the anode groove 25 of the separator 20 to the second catalyst layer 71 through the porous transport layer 72. Then, the voltage from the power source 40 and the action of the catalyst particles of the second catalyst layer 71 decompose the water into hydrogen ions, oxygen, and electrons. The hydrogen ions propagate through the electrolyte membrane 51 to the first catalyst layer 61. The oxygen passes through the porous transport layer 72 and the anode groove 25 of the separator 20 and is discharged to the outside. The electrons pass through the porous transport layer 72 and the separator 20 to flow to the adjacent cell 10. In the adjacent cell 10, the electrons pass through the first gas diffusion layer 62 to reach the first catalyst layer 61. Then, in the first catalyst layer 61, the hydrogen ions and the electrons combine to generate hydrogen. The generated hydrogen passes through the first gas diffusion layer 62 and the cathode groove 24 of the separator 20 and is discharged to the outside. In this way, hydrogen is produced.

[0034] <2. Electrode structure> As described above, the cell 10 is an "electrode structure" that functions as an electrode. The structure of the cell 10 will be described in more detail below. Fig. 3 is a view of one cell 10 viewed in the stacking direction from the anode side. Fig. 4 is a cross-sectional view of the cell 10.

[0035] The electrolyte membrane 51, the first catalyst layer 61, the first gas diffusion layer 62, the second catalyst layer 71, and the porous transport layer 72 are all rectangular when viewed in the stacking direction. As shown in FIG. 4, the outer periphery of the first catalyst layer 61 is located inside the outer periphery of the electrolyte membrane 51. Therefore, when viewed in the stacking direction, the area of ​​the first catalyst layer 61 is smaller than the area of ​​the electrolyte membrane 51. Also, as shown in FIG. 4, the outer periphery of the second catalyst layer 71 is located inside the outer periphery of the electrolyte membrane 51. Therefore, when viewed in the stacking direction, the area of ​​the second catalyst layer 71 is smaller than the area of ​​the electrolyte membrane 51.

[0036] The first catalyst layer 61 is a coating film formed by coating one surface of the electrolyte membrane 51 with a catalyst ink. The second catalyst layer 71 is a coating film formed by coating the other surface of the electrolyte membrane 51 with a catalyst ink. When coating the catalyst ink, the coating range is controlled so that the first catalyst layer 61 and the second catalyst layer 71 are located at substantially the same position when viewed in the stacking direction. Therefore, the first catalyst layer 61 and the second catalyst layer 71 have an overlapping region 90 in which they overlap each other when viewed in the stacking direction. However, it is extremely difficult to strictly match the coating range of the catalyst ink on both surfaces of the electrolyte membrane 51. For this reason, as shown in FIG. 4, the position of the outer periphery of the first catalyst layer 61 and the position of the outer periphery of the second catalyst layer 71 are slightly shifted. Also, when viewed in the stacking direction, the area of ​​the first catalyst layer 61 and the area of ​​the second catalyst layer 71 may not be strictly the same.

[0037] The first gas diffusion layer 62 is attached to the surface of the first catalyst layer 61 opposite the electrolyte membrane 51. The first gas diffusion layer 62 covers a portion of the first catalyst layer 61. The outer peripheral edge of the first gas diffusion layer 62 is located more inward than the outer peripheral edge of the first catalyst layer 61. The porous transport layer 72 is attached to the surface of the second catalyst layer 71 opposite the electrolyte membrane 51. The porous transport layer 72 covers the second catalyst layer 71. The outer peripheral edge of the porous transport layer 72 is located more outward than the outer peripheral edge of the second catalyst layer 71.

[0038] In such a cell 10, the region where the first catalyst layer 61, the first gas diffusion layer 62, the second catalyst layer 71, and the porous transport layer 72 overlap in the stacking direction becomes an effective region A that essentially acts as an electrode.

[0039] In the case of the cell 10 of this embodiment, the outer peripheral edge of the first gas diffusion layer 62 is located inside the outer peripheral edge of the porous transport layer 72, the outer peripheral edge of the first catalyst layer 61, and the outer peripheral edge of the second catalyst layer 71. Therefore, in this embodiment, the region of the first gas diffusion layer 62 is the effective area A that essentially acts as an electrode. That is, the first gas diffusion layer 62 can define the effective area A of the first catalyst layer 61 and the second catalyst layer 71. In this way, even if the precision of the formation range of the first catalyst layer 61 and the second catalyst layer 71 is low, the variation in the effective area A that acts as an electrode can be suppressed.

[0040] In particular, when the first catalyst layer 61 and the second catalyst layer 71 are coating films, as described above, there is a slight misalignment between the position of the outer periphery of the first catalyst layer 61 and the position of the outer periphery of the second catalyst layer 71. However, in this embodiment, the outer periphery of the first gas diffusion layer 62 is located inside the outer periphery of the overlapping region 90 of the first catalyst layer 61 and the second catalyst layer 71. Therefore, regardless of the misalignment between the first catalyst layer 61 and the second catalyst layer 71, the effective area A of the first catalyst layer 61 and the second catalyst layer 71 can be defined by the first gas diffusion layer 62.

[0041] In this embodiment, the first gas diffusion layer 62 has a rectangular shape when viewed in the stacking direction. All four sides of the outer periphery of the first gas diffusion layer 62 are located inside the outer periphery of the porous transport layer 72, the outer periphery of the first catalyst layer 61, and the outer periphery of the second catalyst layer 71. Therefore, the rectangular effective area A of the first catalyst layer 61 and the second catalyst layer 71 can be precisely defined by the first gas diffusion layer 62.

[0042] <3. Modifications> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Various modified examples will be described below, focusing on the differences from the above embodiment.

[0043] <3-1. First modified example> In the above embodiment, all four sides of the rectangular first gas diffusion layer 62 are located inside the outer periphery of the porous transport layer 72, the outer periphery of the first catalyst layer 61, and the outer periphery of the second catalyst layer 71. However, only some of the four sides of the first gas diffusion layer 62 may be located inside the outer periphery of the porous transport layer 72, the outer periphery of the first catalyst layer 61, and the outer periphery of the second catalyst layer 71. For example, of the two long sides and two short sides of the first gas diffusion layer 62 shown in FIG. 3, only two long sides or only two short sides may be located inside the outer periphery of the porous transport layer 72, the outer periphery of the first catalyst layer 61, and the outer periphery of the second catalyst layer 71.

[0044] <3-2. Second modified example> In the above embodiment, the cell 10 used in the water electrolysis device 1 has been described. However, a configuration equivalent to that of the above embodiment may be applied to the cell 10 used in a fuel cell. In the case of the cell 10 for a fuel cell, the porous transport layer 72 is replaced with a second gas diffusion layer. For example, a porous substrate made of carbon (carbon paper) is used for the second gas diffusion layer. Even in this case, if the outer periphery of the first gas diffusion layer 62 is positioned inside the outer periphery of the second gas diffusion layer, the outer periphery of the first catalyst layer 61, and the outer periphery of the second catalyst layer 71, the first gas diffusion layer 62 can define the effective area A as an electrode.

[0045] <3-3.Third modified example> In the case of the cell 10 for a fuel cell, the effective area A may be defined by the second gas diffusion layer. FIG. 5 is a cross-sectional view of the cell 10 according to the modification. In the example of FIG. 5, the outer periphery of the first gas diffusion layer 62 is located outside the outer periphery of the first catalyst layer 61 and the outer periphery of the second catalyst layer 71. The outer periphery of the second gas diffusion layer 73 is located inside the outer periphery of the first gas diffusion layer 62, the outer periphery of the first catalyst layer 61, and the outer periphery of the second catalyst layer 71. Therefore, in the example of FIG. 5, the region of the second gas diffusion layer 73 is the effective area A that essentially acts as an electrode. That is, the second gas diffusion layer 73 can define the effective area A of the first catalyst layer 61 and the second catalyst layer 71. Therefore, even if the precision of the formation range of the first catalyst layer 61 and the second catalyst layer 71 is low, the variation of the effective area A that acts as an electrode can be suppressed.

[0046] 5, the outer periphery of the second gas diffusion layer 73 is located inside the outer periphery of the overlapping region 90 of the first catalyst layer 61 and the second catalyst layer 71. Therefore, regardless of the misalignment between the first catalyst layer 61 and the second catalyst layer 71, the second gas diffusion layer 73 can define the effective area A of the first catalyst layer 61 and the second catalyst layer 71.

[0047] When the second gas diffusion layer 73 has a rectangular shape when viewed in the stacking direction, it is desirable that all four sides of the outer periphery of the second gas diffusion layer 73 are located inside the outer periphery of the first gas diffusion layer 62, the outer periphery of the first catalyst layer 61, and the outer periphery of the second catalyst layer 71. This allows the second gas diffusion layer 73 to accurately define the rectangular effective area A of the first catalyst layer 61 and the second catalyst layer 71.

[0048] <3-4. Other variations> In the above embodiment, a description has been given of the cell 10 using a proton exchange membrane as the electrolyte membrane 51. However, the electrode structure of the present invention may also use an anion exchange membrane as the electrolyte membrane.

[0049] In addition, a configuration equivalent to the above embodiment may be applied to an electrode structure used in a Liquid Organic Hydrogen Carrier (LOHC) process for producing an organic hydride (e.g., toluene-methylcyclohexane) by hydrogenating an aromatic compound such as toluene.

[0050] Furthermore, within the scope of the present invention, some of the configurations of the above-described embodiments and modified examples may be deleted, and other configurations may be added. [Explanation of symbols]

[0051] 1 Water electrolysis device 10 Cells 20 Separator 30 Cell Stack 40 Power supply 51 Electrolyte membrane 61 1st catalyst layer 62 First gas diffusion layer 71 Second catalyst layer 72 Porous transport layer 73 Second gas diffusion layer 90 Overlapping area A. Effective Area

Claims

1. An electrolyte membrane; a first catalyst layer formed on one surface of the electrolyte membrane; a first gas diffusion layer laminated on a surface of the first catalyst layer; a second catalyst layer formed on the other surface of the electrolyte membrane; a porous transport layer or a second gas diffusion layer laminated on a surface of the second catalyst layer; Equipped with an electrode structure, wherein the outer peripheral edge of the first gas diffusion layer is located inside the outer peripheral edge of the porous transport layer or the second gas diffusion layer, the outer peripheral edge of the first catalyst layer, and the outer peripheral edge of the second catalyst layer.

2. 2. The electrode structure according to claim 1, the first catalytic layer and the second catalytic layer have an overlapping region where they overlap each other when viewed in a stacking direction, and an outer periphery of the first catalytic layer and an outer periphery of the second catalytic layer are misaligned with each other, an outer periphery of the first gas diffusion layer is located inside an outer periphery of the overlap region.

3. The electrode structure according to claim 1 or 2, an electrode structure, wherein when viewed in the stacking direction, the first gas diffusion layer is rectangular, and all four sides of the outer periphery of the first gas diffusion layer are located inside the outer periphery of the porous transport layer or the second gas diffusion layer, the outer periphery of the first catalyst layer, and the outer periphery of the second catalyst layer.

4. An electrolyte membrane; a first catalyst layer formed on one surface of the electrolyte membrane; a first gas diffusion layer laminated on a surface of the first catalyst layer; a second catalyst layer formed on the other surface of the electrolyte membrane; a second gas diffusion layer laminated on a surface of the second catalyst layer; Equipped with an outer periphery of the second gas diffusion layer is located more inward than an outer periphery of the first gas diffusion layer, an outer periphery of the first catalyst layer, and an outer periphery of the second catalyst layer.

5. 5. The electrode structure according to claim 4, the first catalytic layer and the second catalytic layer have an overlapping region where they overlap each other when viewed in a stacking direction, and an outer periphery of the first catalytic layer and an outer periphery of the second catalytic layer are misaligned with each other, an outer periphery of the second gas diffusion layer is located inside an outer periphery of the overlap region.

6. The electrode structure according to claim 4 or 5, an electrode structure, wherein when viewed in the stacking direction, the second gas diffusion layer has a rectangular shape, and all four sides of an outer periphery of the second gas diffusion layer are located more inward than an outer periphery of the first gas diffusion layer, an outer periphery of the first catalyst layer, and an outer periphery of the second catalyst layer.

7. 6. The electrode structure according to claim 1, claim 2, claim 4, or claim 5, The electrode structure, wherein the first catalyst layer and the second catalyst layer are coated films.

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