Electrochemical cell

Abstract

This electrochemical cell (1) comprises a cell body part (20) and a metal support (10). The cell body part (20) has an electroconductive gas diffusion layer (5) disposed on the first main surface (12) of the metal support (10), and a hydrogen electrode layer (6) disposed on the gas diffusion layer (5). The gas diffusion layer (5) includes a first portion (51) sandwiched between the first main surface (12) and the hydrogen electrode layer (6). The first portion (51) has a gas flow path (51a) having a length (D1) of 20% or more of the total thickness of the first portion (51) in the thickness direction.

Description

Technical Field

[0001] The present invention relates to an electrochemical cell.

Background Art

[0002] Conventionally, an electrochemical cell (such as an electrolytic cell or a fuel cell) including a cell main body portion disposed on a metal support is known. The metal support has a plurality of communication holes formed in a main surface thereof. The cell main body portion is formed on the main surface of the metal support and has a first electrode layer covering the plurality of communication holes, a second electrode layer, and an electrolyte layer disposed between the first electrode layer and the second electrode layer.

[0003] Here, Patent Document 1 discloses a fuel cell having a bonding layer interposed between a metal support and a first electrode layer. In Patent Document 1, it is described that by forming through holes in the bonding layer that are continuous with the communication holes of the metal support, it becomes easier to supply gas from the communication holes to the first electrode layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, since the gas diffusibility in the bonding layer has not been studied, there is a limit to making it easier to supply gas from the communication holes to the first electrode layer.

[0006] That is, by simply supplying gas from the communication holes to the first electrode layer through the through holes formed in the bonding layer, gas can only be supplied locally to the first electrode layer.

[0007] In order to efficiently supply gas to the first electrode layer, it is important to diffuse the gas supplied from the communication holes within the bonding layer.

[0008] An object of the present invention is to provide an electrochemical cell capable of efficiently supplying gas to a first electrode layer.

Means for Solving the Problems

[0009] The electrochemical cell according to the first aspect of the present invention includes a metal support having a plurality of communication holes formed in a main surface, and a cell main body portion disposed on the main surface. The cell main body portion includes a conductive gas diffusion layer disposed on the main surface, a first electrode layer disposed on the gas diffusion layer, a second electrode layer, and an electrolyte layer disposed between the first electrode layer and the second electrode layer. The gas diffusion layer includes a first portion sandwiched between the main surface and the first electrode layer, and a plurality of second portions sandwiched between the plurality of communication holes and the first electrode layer. In a cross section of the first portion along the thickness direction, the first portion has a gas flow path having a length of 20% or more of the total thickness of the first portion in the thickness direction.

[0010] The electrochemical cell according to the second aspect of the present invention pertains to the first aspect, and the gas flow path extends along the thickness direction.

[0011] The electrochemical cell according to the third aspect of the present invention pertains to the second aspect, and the ratio of the length of the gas flow path in the thickness direction to the width of the gas flow path in a plane direction perpendicular to the thickness direction is 10 or more.

[0012] The electrochemical cell according to the fourth aspect of the present invention pertains to any one of the first to third aspects, and the gas flow path is separated from the first electrode layer.

Advantages of the Invention

[0013] According to the present invention, an electrochemical cell capable of efficiently supplying gas to a first electrode layer can be provided.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0015] (Electrolytic Cell 1) FIG. 1 is a plan view of the electrolytic cell 1 according to the embodiment. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1.

[0016] The electrolytic cell 1 is an example of the "electrochemical cell" according to the present invention. The electrolytic cell 1 is a so-called metal-supported type electrolytic cell.

[0017] The electrolytic cell 1 is formed in a plate shape that spreads in the X-axis direction and the Y-axis direction. In the present embodiment, when the electrolytic cell 1 is viewed in plan from the Z-axis direction perpendicular to the X-axis direction and the Y-axis direction, it is formed in a rectangle extending in the Y-axis direction. However, the planar shape of the electrolytic cell 1 is not particularly limited, and it may be a polygon other than a rectangle, an ellipse, a circle, or the like.

[0018] As shown in FIG. 2, the electrolytic cell 1 includes a metal support 10, a cell main body portion 20, and a flow path member 30.

[0019] [Metal Support 10] The metal support 10 supports the cell main body portion 20. The metal support 10 is formed in a plate shape. The metal support 10 may be flat or curved.

[0020] The metal support 10 only needs to be able to support the cell main body portion 20, and its thickness is not particularly limited, but for example, it can be 0.1 mm or more and 2.0 mm or less.

[0021] As shown in FIG. 2, the metal support 10 has a plurality of communication holes 11, a first main surface 12, and a second main surface 13.

[0022] Each communication hole 11 penetrates the metal support 10 from the first main surface 12 to the second main surface 13. Each communication hole 11 opens to each of the first main surface 12 and the second main surface 13. In the present embodiment, the opening of each communication hole 11 on the first main surface 12 side is covered by a gas diffusion layer 5 described later. The opening of each communication hole 11 on the second main surface 13 side is connected to a flow path 30a described later.

[0023] Each communication hole 11 can be formed by machining (for example, punching), laser processing, or chemical processing (for example, etching).

[0024] In the present embodiment, each communication hole 11 is formed linearly along the Z-axis direction. However, each communication hole 11 may be inclined with respect to the Z-axis direction, or may not be linear. Also, the communication holes 11 may be connected to each other.

[0025] The first main surface 12 is an example of the "main surface" according to the present invention. The first main surface 12 is provided on the opposite side of the second main surface 13. The cell main body 20 is disposed on the first main surface 12. The flow path member 30 is joined to the second main surface 13.

[0026] The metal support 10 is composed of a metal material. For example, the metal support 10 is composed of an alloy material containing Cr (chromium). Examples of such a metal material include Fe-Cr alloy steel (such as stainless steel) and Ni-Cr alloy steel. The content of Cr in the metal support 10 is not particularly limited, but can be 4% by mass or more and 30% by mass or less.

[0027] The metal support 10 may contain Ti (titanium) or Zr (zirconium). The content rate of Ti in the metal support 10 is not particularly limited, but it can be 0.01 mol% or more and 1.0 mol% or less. The content rate of Al in the metal support 10 is not particularly limited, but it can be 0.01 mol% or more and 0.4 mol% or less. The metal support 10 may contain Ti as TiO2 (titania), or may contain Zr as ZrO2 (zirconia).

[0028] The metal support 10 may have an oxide film formed by oxidation of the constituent elements of the metal support 10 on its surface. As the oxide film, for example, a chromium oxide film is typical. The chromium oxide film covers at least a part of the surface of the metal support 10. Also, the chromium oxide film may cover at least a part of the inner wall surface of each communication hole 11.

[0029] [Cell main body 20] The cell main body 20 is disposed on the metal support 10. The cell main body 20 is supported by the metal support 10. The cell main body 20 has a gas diffusion layer 5, a hydrogen electrode layer 6 (cathode), an electrolyte layer 7, a reaction prevention layer 8, and an oxygen electrode layer 9 (anode).

[0030] The gas diffusion layer 5, the hydrogen electrode layer 6, the electrolyte layer 7, the reaction prevention layer 8, and the oxygen electrode layer 9 are laminated in this order from the side of the metal support 10 in the Z-axis direction. The gas diffusion layer 5, the hydrogen electrode layer 6, the electrolyte layer 7, and the oxygen electrode layer 9 are essential components, and the reaction prevention layer 8 is an optional component.

[0031] [Gas diffusion layer 5] The gas diffusion layer 5 is formed on the first main surface 12 of the metal support 10. In the present embodiment, the gas diffusion layer 5 covers each communication hole 11 of the metal support 10. A part of the gas diffusion layer 5 may enter inside each communication hole 11 of the metal support 10.

[0032] The gas diffusion layer 5 is a porous body having conductivity. The gas diffusion layer 5 has gas diffusibility. The gas diffusion layer 5 supplies the raw material gas supplied from each communication hole 11 to the hydrogen electrode layer 6, and discharges the generated gas generated in the hydrogen electrode layer 6 to each communication hole 11.

[0033] The gas diffusion layer 5 contains a conductive material. As the conductive material, metal materials such as Ni (nickel) and Fe (iron), and conductive ceramic materials can be used.

[0034] The gas diffusion layer 5 may include a substrate that supports the conductive material. The substrate may be insulating. As the substrate, YSZ, CSZ, ScSZ, GDC, SDC, (La,Sr)(Cr,Mn)O3, (La,Sr)TiO3, Sr2(Fe,Mo)2O6, (La,Sr)VO3, (La,Sr)FeO3, LDC (lanthanum-doped ceria), LSGM (lanthanum gallate), and a mixed material obtained by combining two or more of these can be used.

[0035] The gas diffusion layer 5 may contain a metal element contained in the metal support 10. This is preferable because the adhesion between the gas diffusion layer 5 and the metal support 10 is improved. Note that the above-described conductive material is different from the metal element contained in the metal support 10. Therefore, the conductive material contained in the gas diffusion layer 5 may not be contained in the metal support 10.

[0036] The thickness of the gas diffusion layer 5 is not particularly limited, but can be, for example, 1 μm or more and 50 μm or less. In this specification, the thickness means the thickness in the thickness direction of the cell main body 20. The thickness direction is a direction perpendicular to the plane direction parallel to the first main surface 12 of the metal support 10. The plane direction is defined by an approximate straight line of the first main surface 12 obtained by the least squares method in the cross section of the metal support 10 along the Z-axis direction.

[0037] The method for forming the gas diffusion layer 5 is not particularly limited, and a firing method, a spray coating method (such as a thermal spraying method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, a cold spray method, etc.), a PVD method (such as a sputtering method, a pulsed laser deposition method, etc.), a CVD method, etc. can be used.

[0038] As shown in FIG. 2, the gas diffusion layer 5 includes a first portion 51 and a plurality of second portions 52.

[0039] The first portion 51 is the portion of the gas diffusion layer 5 that is sandwiched between the first main surface 12 of the metal support 10 and the hydrogen electrode layer 6 in the thickness direction. The first portion 51 is the portion of the gas diffusion layer 5 excluding the second portion 52.

[0040] The second portion 52 is the portion of the gas diffusion layer 5 between the communication hole 11 of the metal support 10 and the hydrogen electrode layer 6 in the thickness direction. Since there are a plurality of communication holes 11, there are also a plurality of second portions 52.

[0041] Here, FIG. 3 is a partial enlarged view of FIG. 2. In FIG. 3, an enlarged view of the gas diffusion layer 5 is schematically shown.

[0042] The first portion 51 of the gas diffusion layer 5 has a gas flow path 51a. The gas flow path 51a is a flow path for the source gas supplied from each communication hole 11 and the product gas generated in the hydrogen electrode layer 6.

[0043] The gas flow path 51a has a length D1 of 20% or more of the total thickness of the first portion 51 in the thickness direction. Thereby, the gas (source gas or product gas) flowing into the gas flow path 51a can be efficiently circulated in the thickness direction. In this way, since the gas flow path 51a functions as a bypass for circulating the gas in the thickness direction, the gas can be widely supplied from the gas flow path 51a to the inside of the first portion 51 as water is supplied from the trunk to the branches in a tree. As a result, the gas diffusibility in the first portion 51 can be significantly improved.

[0044] The gas flow path 51a preferably extends along the thickness direction. That is, the length D1 of the gas flow path 51a in the thickness direction is preferably greater than the width D2 of the gas flow path 51a in the plane direction. Thereby, it is possible to suppress the conductive path extending in the thickness direction within the first portion 51 from being cut off by the gas flow path 51a.

[0045] The ratio of the length D1 of the gas flow path 51a in the thickness direction to the width D2 of the gas flow path 51a is preferably 10 or more. Thereby, it is possible to further suppress the conductive path from being cut off by the gas flow path 51a.

[0046] The value of the length D1 of the gas flow path 51a is not particularly limited, but can be, for example, 1 μm or more and 50 μm or less. The value of the width D2 of the gas flow path 51a is not particularly limited, but can be, for example, 0.2 μm or more and 0.5 μm or less.

[0047] Here, the total thickness of the first portion 51 is obtained by measuring the total thickness of the first portion 51 at 10 randomly selected locations in the SEM image of the first portion 51 and calculating their arithmetic mean. The length D1 of the gas flow path 51a is obtained by measuring the total length of the gas flow path 51a in the thickness direction in the SEM image of the first portion 51. The width D2 of the gas flow path 51a is obtained by measuring the total width of the gas flow path 51a in the plane direction in the SEM image of the first portion 51.

[0048] The SEM image is acquired using a FE-SEM (Field Emission Scanning Electron Microscope) using an in-lens secondary electron detector. The observation magnification of the FE-SEM is set to a magnification at which the gas flow path 51a can be confirmed (for example, 5000 to 30000 times).

[0049] As shown in FIG. 3, the gas flow path 51a is preferably away from the hydrogen electrode layer 6. That is, the end portion of the gas flow path 51a on the hydrogen electrode layer 6 side is preferably buried inside the first portion 51 and not in contact with the hydrogen electrode layer 6. This can suppress the direct and local supply of the raw material gas to the hydrogen electrode layer 6, so that the raw material gas can be supplied from the gas flow path 51a to the entire hydrogen electrode layer 6 through the inside of the first portion 51.

[0050] Note that the gas flow path 51a can be formed by embedding a string-shaped pore former along the thickness direction in a slurry (including the constituent material of the gas diffusion layer 5) applied to the first main surface 12 of the metal support 10 when forming the molded body of the gas diffusion layer 5.

[0051] In FIG. 3, a gas flow path 51a curved in the plane direction is shown, but the shape of the gas flow path 51a can be appropriately changed. The shape of the gas flow path 51a can be changed by adjusting the shape of the pore former.

[0052] Also, in FIG. 3, a gas flow path 51a in contact with the metal support 10 and away from the hydrogen electrode layer 6 is shown, but the position of the gas flow path 51a can be appropriately changed. The position of the gas flow path 51a can be changed by adjusting the embedding position of the pore former.

[0053] [Hydrogen electrode layer 6] The hydrogen electrode layer 6 is an example of the "first electrode layer" according to the present invention. The hydrogen electrode layer 6 is formed on the gas diffusion layer 5. The hydrogen electrode layer 6 is disposed between the gas diffusion layer 5 and the electrolyte layer 7.

[0054] The raw material gas is supplied to the hydrogen electrode layer 6 from each communication hole 11 through the gas diffusion layer 5. The raw material gas contains at least H2O.

[0055] When the raw material gas contains only H2O, the hydrogen electrode layer 6 generates H2 from the raw material gas according to the electrochemical reaction of water electrolysis represented by the following formula (1).

[0056] · Hydrogen electrode layer 6: H2O + 2e- →H2 + O 2- ···(1)

[0057] When the raw material gas contains CO2 in addition to H2O, the hydrogen electrode layer 6 generates H2, CO, and O from the raw material gas according to the electrochemical reactions of co-electrolysis shown in the following formulas (2), (3), and (4). 2- is generated.

[0058] · Hydrogen electrode layer 6: CO2 + H2O + 4e - → CO + H2 + 2O 2- ···(2) · Electrochemical reaction of H2O: H2O + 2e - → H2 + O 2- ···(3) · Electrochemical reaction of CO2: CO2 + 2e - → CO + O 2- ···(4)

[0059] The hydrogen electrode layer 6 is a porous body having conductivity. The hydrogen electrode layer 6 has gas diffusibility. The raw material gas is supplied to the hydrogen electrode layer 6 from the gas diffusion layer 5. The hydrogen electrode layer 6 discharges the generated gas generated inside to the gas diffusion layer 5 side.

[0060] The hydrogen electrode layer 6 contains a conductive material. As the conductive material, metal materials such as Ni (nickel) and Fe (iron), and conductive ceramic materials can be used. In the case of co-electrolysis, Ni also functions as a thermal catalyst that promotes the thermal reaction between the generated H2 and CO2 contained in the raw material gas and maintains an appropriate gas composition for methanation and the reverse water gas shift reaction.

[0061] The conductive material exists in the state of an oxide (for example, NiO) in an oxidizing atmosphere and in the state of a metal (for example, Ni) in a reducing atmosphere. In this embodiment, it is assumed that the electrolytic cell 1 is exposed to a reducing atmosphere.

[0062] The hydrogen electrode layer 6 contains an oxide ion conductive material. The oxide ion conductive material is an example of the "ion conductive material" according to the present invention. As the oxide ion conductive material, YSZ, CSZ, ScSZ, GDC, SDC, (La,Sr)(Cr,Mn)O3, (La,Sr)TiO3, Sr2(Fe,Mo)2O6, (La,Sr)VO3, (La,Sr)FeO3, LDC, LSGM, and a mixed material obtained by combining two or more of these can be used.

[0063] In the present embodiment, the hydrogen electrode layer 6 has a single-layer structure composed of a single composition, but may have a multilayer structure composed of different compositions.

[0064] The thickness of the hydrogen electrode layer 6 is not particularly limited, but can be, for example, 1 μm or more and 500 μm or less.

[0065] The method for forming the hydrogen electrode layer 6 is not particularly limited, and a firing method, a spray coating method, a PVD method, a CVD method, or the like can be used.

[0066] [Electrolyte layer 7] The electrolyte layer 7 is disposed between the hydrogen electrode layer 6 and the oxygen electrode layer 9. In the present embodiment, since the reaction prevention layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9, the electrolyte layer 7 is sandwiched between the hydrogen electrode layer 6 and the reaction prevention layer 8.

[0067] The electrolyte layer 7 covers the hydrogen electrode layer 6 and covers the region of the first main surface 12 of the metal support 10 that is exposed from the gas diffusion layer 5.

[0068] The electrolyte layer 7 transfers the O 2- generated in the hydrogen electrode layer 6 to the oxygen electrode layer 9 side. The electrolyte layer 7 is composed of a dense material having oxide ion conductivity. The electrolyte layer 7 can be composed of, for example, YSZ (yttria-stabilized zirconia, such as 8YSZ), GDC (gadolinium-doped ceria), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), LSGM (lanthanum gallate), or the like.

[0069] The porosity of the electrolyte layer 7 is not particularly limited, and can be, for example, 0.1% or more and 7% or less. The thickness of the electrolyte layer 7 is not particularly limited, and can be, for example, 1 μm or more and 100 μm or less.

[0070] The method for forming the electrolyte layer 7 is not particularly limited, and a firing method, a spray coating method, a PVD method, a CVD method, etc. can be used.

[0071] [Reaction prevention layer 8] The reaction prevention layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9. The reaction prevention layer 8 is disposed on the side opposite to the hydrogen electrode layer 6 with respect to the electrolyte layer 7. The reaction prevention layer 8 suppresses the formation of a layer with a large electrical resistance due to the reaction between the constituent elements of the electrolyte layer 7 and the constituent elements of the oxygen electrode layer 9.

[0072] The reaction prevention layer 8 is composed of an oxide ion conductive material. The reaction prevention layer 8 can be composed of GDC, SDC, etc.

[0073] The porosity of the reaction prevention layer 8 is not particularly limited, and can be, for example, 0.1% or more and 50% or less. The thickness of the reaction prevention layer 8 is not particularly limited, and can be, for example, 1 μm or more and 50 μm or less.

[0074] The method for forming the reaction prevention layer 8 is not particularly limited, and a firing method, a spray coating method, a PVD method, a CVD method, etc. can be used.

[0075] [Oxygen electrode layer 9] The oxygen electrode layer 9 is an example of the "second electrode layer" according to the present invention. The oxygen electrode layer 9 is disposed on the side opposite to the hydrogen electrode layer 6 with respect to the electrolyte layer 7. In the present embodiment, since the reaction prevention layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9, the oxygen electrode layer 9 is connected to the reaction prevention layer 8. When the reaction prevention layer 8 is not disposed between the electrolyte layer 7 and the oxygen electrode layer 9, the oxygen electrode layer 9 is connected to the electrolyte layer 7.

[0076] The oxygen electrode layer 9 generates O2 from O transmitted from the hydrogen electrode layer 6 through the electrolyte layer 7 according to the chemical reaction of the following formula (5). 2- from O

[0077] ·Oxygen electrode layer 9: 2O 2- →O2 + 4e - ···(5) The oxygen electrode layer 9 is a porous body having oxide ion conductivity and conductivity. The oxygen electrode layer 9 can be composed of a composite material of one or more of, for example, (La, Sr)(Co, Fe)O3, (La, Sr)FeO3, La(Ni, Fe)O3, (La, Sr)CoO3, and (Sm, Sr)CoO3 and an oxide ion conductive material (such as GDC).

[0078] The porosity of the oxygen electrode layer 9 is not particularly limited, but can be, for example, 20% or more and 60% or less. The thickness of the oxygen electrode layer 9 is not particularly limited, but can be, for example, 1 μm or more and 100 μm or less.

[0079] The method for forming the oxygen electrode layer 9 is not particularly limited, and a firing method, a spray coating method, a PVD method, a CVD method, etc. can be used.

[0080] [Flow path member 30] The flow path member 30 is joined to the second main surface 13 of the metal support 10. The flow path member 30 forms a flow path 30a between it and the metal support 10. A raw material gas is supplied to the flow path 30a. The raw material gas supplied to the flow path 30a is supplied to the hydrogen electrode layer 6 of the cell main body 20 through each communication hole 11 of the metal support 10.

[0081] The flow path member 30 can be composed of, for example, an alloy material. The flow path member 30 may be formed of the same material as the metal support 10. In this case, the flow path member 30 may be substantially integral with the metal support 10.

[0082] The flow path member 30 has a frame body 31 and an interconnector 32. The frame body 31 is an annular member that surrounds the side of the flow path 30a. The frame body 31 is joined to the second main surface 13 of the metal support 10. The interconnector 32 is a plate-like member for electrically connecting the external power source or another electrolytic cell to the electrolytic cell 1 in series. The interconnector 32 is joined to the frame body 31.

[0083] In this embodiment, the frame body 31 and the interconnector 32 are separate members, but the frame body 31 and the interconnector 32 may be an integral member.

[0084] (Detailed configuration of the gas diffusion layer 5 and the hydrogen electrode layer 6) FIG. 4 is a partially enlarged view of FIG. 2. In FIG. 4, cross-sections of the gas diffusion layer 5, the hydrogen electrode layer 6, and the metal support 10 along the thickness direction are schematically shown. Note that in FIG. 4, the first portion 51 of the gas diffusion layer 5 is shown.

[0085] The gas diffusion layer 5 has a plurality of first conductive particles 5a, a plurality of base material particles 5b, and a plurality of first pores 5c. The plurality of first conductive particles 5a and the plurality of first pores 5c are essential components, and the plurality of base material particles 5b are optional components.

[0086] The first conductive particles 5a are connected to each other. Thereby, a conductive path extending in the thickness direction within the gas diffusion layer 5 is formed. The first conductive particles 5a are connected at the neck portion L1. The neck portion L1 is formed by the mass transfer between the first conductive particles 5a due to heating when forming the gas diffusion layer 5.

[0087] The base material particles 5b are connected to each other. Thereby, a skeleton for holding the conductive path is formed. The base material particles 5b are connected at the neck portion L2. The neck portion L2 is formed by the mass transfer between the base material particles 5b due to heating when forming the gas diffusion layer 5.

[0088] The first pores 5c are connected to each other. Thereby, a gas flow path that spreads three-dimensionally within the gas diffusion layer 5 is formed. The first pore 5c is a gap between the first conductive particles 5a and the base material particles 5b.

[0089] The hydrogen electrode layer 6 has a plurality of second conductive particles 6a, a plurality of ion conductive particles 6b, and a plurality of second pores 6c.

[0090] The second conductive particles 6a are connected to each other. Thereby, a conductive path extending in the thickness direction within the hydrogen electrode layer 6 is formed. The second conductive particles 6a are connected at the neck portion M1. The neck portion M1 is formed by the mass transfer between the second conductive particles 6a accompanying the heating when forming the hydrogen electrode layer 6.

[0091] The ion conductive particles 6b are connected to each other. Thereby, an ion conduction path that spreads three-dimensionally within the hydrogen electrode layer 6 is formed. The ion conductive particles 6b are connected at the neck portion M2. The neck portion M2 is formed by the mass transfer between the ion conductive particles 6b accompanying the heating when forming the hydrogen electrode layer 6.

[0092] The second pores 6c are connected to each other. Thereby, a gas flow path that spreads three-dimensionally within the hydrogen electrode layer 6 is formed. The second pore 6c is a gap between the second conductive particles 6a and the ion conductive particles 6b.

[0093] It is preferable that the average equivalent circle diameter of the plurality of first pores 5c included in the gas diffusion layer 5 is smaller than the average equivalent circle diameter of the plurality of second pores 6c included in the hydrogen electrode layer 6. That is, it is preferable that the gas diffusion layer 5 contains more pores with a smaller diameter than the hydrogen electrode layer 6. Further, it is preferable that the porosity of the gas diffusion layer 5 is larger than the porosity of the hydrogen electrode layer 6. That is, it is preferable that the volume ratio of the gas flow path per unit volume of the gas diffusion layer 5 is larger than the volume ratio of the gas flow path per unit volume of the hydrogen electrode layer 6.

[0094] As a result, the gas diffusibility of the gas diffusion layer 5 can be improved, so that gas can be diffused not only in the thickness direction but also in the plane direction in the gas diffusion layer 5. Therefore, the gas diffusion layer 5 can efficiently supply the raw material gas supplied from each communication hole 11 of the metal support 10 to the entire hydrogen electrode layer 6, and can efficiently discharge the product gas generated in the hydrogen electrode layer 6 from the entire hydrogen electrode layer 6 to each communication hole 11.

[0095] Note that the average equivalent circle diameter of the pores is the arithmetic average value of the equivalent circle diameters of a plurality of pores. The equivalent circle diameter of a pore is the diameter of a circle having the same area as the area of the pore appearing in the cross section along the thickness direction.

[0096] The porosity of the gas diffusion layer 5 and the hydrogen electrode layer 6 can be obtained as follows. Since the measurement method of the porosity is common to each layer, the case of obtaining the porosity of the gas diffusion layer 5 will be described below as an example.

[0097] First, by supplying hydrogen to the gas diffusion layer 5 and the hydrogen electrode layer 6 in a state where the temperature of the electrolytic cell 1 is raised to 750 ° C., the conductive materials contained in the gas diffusion layer 5 and the hydrogen electrode layer 6 are reduced.

[0098] Next, while maintaining the reducing atmosphere, the temperature of the electrolytic cell 1 is lowered, and the electrolytic cell 1 is cut along the thickness direction (Z-axis direction) to expose the cross sections of the gas diffusion layer 5 and the hydrogen electrode layer 6.

[0099] Next, after the cross section is polished by a precision machine, ion milling processing is performed by IM4000 of Hitachi High-Technologies Corporation.

[0100] Next, an SEM image of the cross section of the gas diffusion layer 5 is enlarged at a magnification (for example, 5000 to 30000 times) that allows the first conductive particles 5a, the base material particles 5b, and the first pores 5c to be confirmed using FE-SEM using an in-lens secondary electron detector.

[0101] Next, by classifying the brightness of the SEM image into 256 gradations, the brightness differences among the first conductive particles 5a, the base material particles 5b, and the first pores 5c are binarized. For example, the first conductive particles 5a can be displayed in dark gray, the base material particles 5b in light gray, and the first pores 5c in black.

[0102] Next, using the image analysis software HALCON manufactured by MVTec (Germany), the SEM image is analyzed to obtain an analysis image in which the first pores 5c are highlighted.

[0103] Next, the total area of the first pores 5c (gas phase) is obtained from the analysis image, and the porosity in one analysis image is calculated by dividing the total area of the first pores 5c by the area of the entire analysis image.

[0104] Then, the above analysis is performed at five randomly selected locations in the same cross-section of the gas diffusion layer 5, and the arithmetic mean value of the porosities calculated at the five locations is taken as the porosity of the gas diffusion layer 5.

[0105] As shown in FIG. 4, it is preferable that the number of the first pores 5c per unit area of the gas diffusion layer 5 is larger than the number of the second pores 6c per unit area of the hydrogen electrode layer 6. Thereby, since the gas can be diffused to every corner of the gas diffusion layer 5, the gas diffusibility of the gas diffusion layer 5 can be further improved. The number of pores can be obtained from the analysis image used for obtaining the porosity.

[0106] Also, it is preferable that the average neck diameter among the first conductive particles 5a included in the gas diffusion layer 5 is smaller than the average neck diameter among the second conductive particles 6a included in the hydrogen electrode layer 6. Thereby, it becomes easier to form a structure in the gas diffusion layer 5 that contains many small-diameter pores and has a large volume ratio of the gas flow path.

[0107] The average neck diameter between the first conductive particles 5a is the arithmetic mean value of the neck diameters of the neck portions L1 between the first conductive particles 5a. The neck diameter of the neck portion L1 is the width of the narrowest part between two first conductive particles 5a. The average neck diameter between the first conductive particles 5a can be obtained by arithmetically averaging the neck diameters of 10 randomly selected neck portions L1 from the analysis image used for obtaining the porosity. The average neck diameter between the first conductive particles 5a is not particularly limited, but can be, for example, 0.05 μm or more and 0.5 μm or less.

[0108] Similarly, the average neck diameter between the second conductive particles 6a is the arithmetic mean value of the neck diameters of the neck portions M1 between the second conductive particles 6a. The neck diameter of the neck portion M1 is the width of the narrowest part between two second conductive particles 6a. The average neck diameter between the second conductive particles 6a can be obtained by arithmetically averaging the neck diameters of 10 randomly selected neck portions M1 from the analysis image used for obtaining the porosity. The average neck diameter between the second conductive particles 6a is not particularly limited, but can be, for example, 0.1 μm or more and 3 μm or less.

[0109] Also, it is preferable that the average neck diameter between the base material particles 5b included in the gas diffusion layer 5 is smaller than the average neck diameter between the ion conductive particles 6b included in the hydrogen electrode layer 6. Thereby, it becomes easier to form a structure having many small pores and a large volume ratio of the gas flow path by the gas diffusion layer 5.

[0110] The average neck diameter between the base material particles 5b is the arithmetic mean value of the neck diameters of the neck portions L2 between the base material particles 5b. The neck diameter of the neck portion L2 is the width of the narrowest part between two base material particles 5b. The average neck diameter between the base material particles 5b can be obtained by arithmetically averaging the neck diameters of 10 randomly selected neck portions L2 from the analysis image used for obtaining the porosity. The average neck diameter between the base material particles 5b is not particularly limited, but can be, for example, 0.1 μm or less.

[0111] Similarly, the average neck diameter between the ionic conductive particles 6b is the arithmetic mean value of the neck diameters of the neck portions M2 between the ionic conductive particles 6b. The neck diameter of the neck portion M2 is the width of the narrowest portion between two ionic conductive particles 6b. The average neck diameter between the ionic conductive particles 6b can be obtained by arithmetically averaging the neck diameters of 10 neck portions M2 randomly selected from the analysis image used for obtaining the porosity. The average neck diameter between the ionic conductive particles 6b is not particularly limited, but can be, for example, 1 μm or more and 3 μm or less.

[0112] (Modification of the embodiment) As described above, the embodiments of the present invention have been described. However, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention.

[0113] [Modification 1] In the above embodiment, the opening on the first main surface 12 side of each communication hole 11 of the metal support 10 is covered by the gas diffusion layer 5, but it is not limited to this. The gas diffusion layer 5 may not cover the opening on the first main surface 12 side of each communication hole 11. That is, the gas diffusion layer 5 may not include the second portion 52. In this case, since through holes connected to each communication hole 11 are formed in the gas diffusion layer 5, more efficient gas supply and discharge can be performed through the through holes.

[0114] [Modification 2] In the above embodiment, the electrolytic cell 1 has been described as an example of the electrochemical cell. However, the electrochemical cell is not limited to the electrolytic cell. An electrochemical cell is a general term for an element in which a pair of electrodes are arranged so that an electromotive force is generated from an overall oxidation-reduction reaction in order to convert electrical energy into chemical energy, and an element for converting chemical energy into electrical energy. Therefore, the electrochemical cell includes, for example, a fuel cell that uses oxide ions or protons as carriers.

Explanation of symbols

[0115] 1 Electrolytic cell 10 Metal support 11 Continuous through-holes 12 First main surface 13 Second main surface 20 Cell main body part 5 Gas diffusion layer 5a First conductive particles 5b Substrate particles 5c First pores 5d Neck part of the first conductive particles 5e Neck part of the substrate particles 6 Hydrogen electrode layer 6a Second conductive particles 6b Ion conductive particles 6c Second pores 6d Neck part of the second conductive particles 6e Neck part of the ion conductive particles 7 Electrolyte layer 8 Reaction prevention layer 9 Oxygen electrode layer 30 Flow path member 30a Flow path

Claims

1. A metal support having a plurality of communication holes formed on a main surface, A cell body portion disposed on the main surface, Comprising, The cell body portion is, A conductive gas diffusion layer disposed on the main surface, A first electrode layer disposed on the gas diffusion layer, A second electrode layer, An electrolyte layer disposed between the first electrode layer and the second electrode layer, Having, The gas diffusion layer includes a first portion sandwiched between the main surface and the first electrode layer, and a plurality of second portions sandwiched between the plurality of communication holes and the first electrode layer, In a cross-section of the first portion along the thickness direction, the first portion has a gas flow path having a length of 20% or more of the total thickness of the first portion in the thickness direction, An electrochemical cell.

2. The gas flow path extends along the thickness direction, The electrochemical cell according to claim 1.

3. The ratio of the length of the gas flow path in the thickness direction to the width of the gas flow path in a plane direction perpendicular to the thickness direction is 10 or more, The electrochemical cell according to claim 2.

4. The gas flow path is away from the first electrode layer, The electrochemical cell according to any one of claims 1 to 3.

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