Reducing gas container and metal-supported electrochemical cell

Abstract

The reducing gas container (3) includes a metal support (10), a frame (20), and a first seal portion (40) that seals between the metal support (10) and the frame (20). The first seal portion (40) includes a first joint portion (41) that is integrally formed with the metal support (10) and the frame (20), and a second joint portion (42) that is sandwiched between the metal support (10) and the frame (20) and disposed on the inner space (3a) side of the first joint portion (41). The first joint portion (41) is made of a metal material. The second joint portion (42) is made of a crystalline metal oxide.

Description

Reducing gas container and metal-supported electrochemical cell

[0001] The present invention relates to a reducing gas container and a metal-supported electrochemical cell.

[0002] Patent Document 1 discloses a metal-supported fuel cell that includes a reducing gas container and a cell body disposed on the reducing gas container.

[0003] The reducing gas container is composed of a porous first metal member that supports the cell main body, a dense second metal member that forms an internal space between the first metal member and the second metal member through which the reducing gas (e.g., hydrogen) flows, and a sealing portion that seals the space between the first metal member and the second metal member.

[0004] The seal portion is composed of a first weld bead, a second weld bead, and glass paste. The first weld bead is integrally formed with each of the first and second metal members and exposed to the internal space. The second weld bead is integrally formed with each of the first and second metal members and positioned on the opposite side of the internal space from the first weld bead. The glass paste is filled between the first and second weld beads.

[0005] JP 2020-181763 A

[0006] In the reducing gas container described in Patent Document 1, the first weld bead is easily deteriorated by the reducing gas flowing through the internal space, and when the first weld bead deteriorates, the glass paste and second weld bead also deteriorate in turn, resulting in low mechanical reliability of the seal portion.

[0007] An object of the present invention is to provide a reducing gas container and a metal-supported electrochemical cell that can improve the mechanical reliability of the seal that seals between the first metal member and the second metal member.

[0008] A reducing gas container according to a first aspect of the present invention is a reducing gas container having an internal space through which a reducing gas flows, and includes a first metal member, a second metal member, and a seal portion that seals between the first metal member and the second metal member. The seal portion has a first bonding portion integrally formed with each of the first and second metal members, and a second bonding portion sandwiched between the first and second metal members and positioned on the internal space side of the first bonding portion. The first bonding portion is made of a metal material. The second bonding portion is made of a crystalline metal oxide.

[0009] A reducing gas container according to a second aspect of the present invention relates to the first aspect, and the crystalline metal oxide constituting the second bonding portion contains a metal element contained in at least one of the first and second metal members.

[0010] A reducing gas container according to a third aspect of the present invention is related to the second aspect, wherein the second bonding portion is substantially free of boron and silicon.

[0011] A reducing gas container according to a fourth aspect of the present invention relates to the second or third aspect, wherein the crystalline metal oxide constituting the second bonding portion is composed of at least one of chromium oxide, chromium manganese oxide, and iron oxide.

[0012] A reducing gas container according to a fifth aspect of the present invention is related to any one of the first to fourth aspects, wherein the thermal expansion coefficient of the second joint portion is smaller than the thermal expansion coefficients of the first and second metal members.

[0013] A reducing gas container according to a sixth aspect of the present invention relates to any one of the first to fifth aspects, wherein the second joint is formed in a ring shape so as to surround the internal space, and the first joint is formed in a ring shape so as to surround the second joint.

[0014] A reducing gas container according to a seventh aspect of the present invention is related to the sixth aspect, wherein the first joint portion has an intersection portion in plan view.

[0015] A reducing gas container according to an eighth aspect of the present invention relates to any one of the first to seventh aspects, and the sealing portion further includes a third bonding portion. The third bonding portion is sandwiched between the first and second metal members and is located on the opposite side of the second bonding portion with respect to the first bonding portion. The third bonding portion is made of a crystalline metal oxide.

[0016] A metal-supported electrochemical cell according to a ninth aspect of the present invention includes the reducing gas container according to any one of the first to eighth aspects and a cell main body disposed on the reducing gas container. The first metal member has a plurality of communication holes communicating with the internal space. The cell main body is disposed on the first metal member so as to cover the plurality of communication holes.

[0017] According to the present invention, it is possible to provide a reducing gas container and a metal-supported electrochemical cell that can improve the mechanical reliability of the seal portion that seals between the first metal member and the second metal member.

[0018] Fig. 1 is a plan view of an electrolysis cell according to an embodiment. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. Fig. 3 is a partially enlarged view of Fig. 2. Fig. 4 is a plan view of a first seal portion.

[0019] (Electrolytic cell 1) Fig. 1 is a plan view of an electrolytic cell 1 according to an embodiment. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1.

[0020] The electrolysis cell 1 is an example of a "metal-supported electrochemical cell" according to the present invention.

[0021] The electrolytic cell 1 is formed in a plate shape extending in the X-axis and Y-axis directions. In the present embodiment, the electrolytic cell 1 is formed in a rectangular shape extending in the Y-axis direction when viewed in a plan view from the Z-axis direction perpendicular to the X-axis and Y-axis directions. However, the planar shape of the electrolytic cell 1 is not particularly limited, and may be a polygon other than a rectangle, an ellipse, a circle, or the like.

[0022] As shown in FIGS. 1 and 2, the electrolysis cell 1 includes a cell body 2 and a reducing gas container 3 .

[0023] (Cell main body 2) The cell main body 2 is placed on the reducing gas container 3. The cell main body 2 is supported by a metal support 10 (described later) of the reducing gas container 3. The cell main body 2 has a hydrogen electrode 6 (cathode), an electrolyte 7, a reaction prevention layer 8, and an oxygen electrode 9 (anode).

[0024] The hydrogen electrode 6, electrolyte 7, reaction prevention layer 8, and oxygen electrode 9 are stacked in this order in the Z-axis direction from the reducing gas container 3 side. The hydrogen electrode 6, electrolyte 7, and oxygen electrode 9 are essential components, while the reaction prevention layer 8 is an optional component.

[0025] [Hydrogen Electrode 6 ] The hydrogen electrode 6 is disposed on the first main surface 12 of the metal support 10 .

[0026] The hydrogen electrode 6 is supplied with a source gas from each supply hole 11 of the metal support 10. The source gas contains at least water vapor (H ２ O).

[0027] The raw material gas is H ２ When the raw material gas contains only O, the hydrogen electrode 6 converts H ２ Generate.

[0028] Hydrogen electrode 6: H ２ O + 2e － →H ２ +O ２－ ...(1)

[0029] The raw material gas is H ２ O plus CO ２ In this case, the hydrogen electrode 6 converts the raw material gas into H according to the electrochemical reactions of co-electrolysis shown in the following formulas (2), (3), and (4). ２ , CO and O ２－ Generate.

[0030] Hydrogen electrode 6: CO ２ +H ２ O+4e － →CO+H ２ +20 ２－ ... (2) H ２ Electrochemical reaction of O: H ２ O + 2e － →H ２ +O ２－ ... (3) CO２ Electrochemical reaction of: CO ２ +2e － →CO+O ２－ ...(4)

[0031] H generated at the hydrogen electrode 6 ２ flows out from each supply hole 11 of the metal support 10 into the internal space 3a (described later). ２ is an example of the "reducing gas" flowing through the internal space 3a.

[0032] The hydrogen electrode 6 is a porous body having electron conductivity. The hydrogen electrode 6 contains nickel (Ni). In the case of co-electrolysis, Ni functions as an electron conductor and also functions as a conductor for the generated H ２ and CO contained in the raw material gas ２ It also functions as a thermal catalyst that promotes the thermal reaction with HCl and maintains an appropriate gas composition for methanation, Fischer-Tropsch (FT) synthesis, etc. The Ni contained in the hydrogen electrode 6 is basically present in the form of metallic Ni during operation of the electrolysis cell 1, but a portion of it may also be present in the form of nickel oxide (NiO).

[0033] The hydrogen electrode 6 may contain an ion-conductive material, such as yttria-stabilized zirconia (YSZ), calcia-stabilized zirconia (CSZ), scandia-stabilized zirconia (ScSZ), gadolinium-doped ceria (GDC), samarium-doped ceria (SDC), (La, Sr)(Cr, Mn)O, or the like. ３ , (La,Sr)TiO ３ , Sr ２ (Fe, Mo) ２ O ６ , (La, Sr)VO ３ , (La,Sr)FeO ３ and mixed materials of two or more of these.

[0034] The thickness of the hydrogen electrode 6 is not particularly limited, but may be, for example, 1 μm or more and 100 μm or less. The thermal expansion coefficient of the hydrogen electrode 6 is not particularly limited, but may be, for example, 12×10 ―６ / ℃ or more 20 x 10 －６ / °C or less.

[0035] The method for forming the hydrogen electrode 6 is not particularly limited, and may be 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, or a cold spray method), a PVD method (such as a sputtering method or a pulsed laser deposition method), or a CVD method.

[0036] [Electrolyte 7] The electrolyte 7 is formed on the hydrogen electrode 6. The electrolyte 7 is disposed between the hydrogen electrode 6 and the oxygen electrode 9. In this embodiment, the electrolyte 7 is sandwiched between the hydrogen electrode 6 and the reaction prevention layer 8 and connected to both of them.

[0037] The electrolyte 7 covers the hydrogen electrode 6 and also covers the region of the first main surface 12 of the metal support 10 that is exposed from the hydrogen electrode 6 .

[0038] The electrolyte 7 is a dense body having oxide ion conductivity. ２－ The electrolyte 7 is made of an oxide ion conductive material, such as YSZ, GDC, ScSZ, SDC, or LSGM (lanthanum gallate), with YSZ being particularly suitable.

[0039] The thickness of the electrolyte 7 is not particularly limited, but may be, for example, 1 μm or more and 100 μm or less. The thermal expansion coefficient of the electrolyte 7 is not particularly limited, but may be, for example, 10×10 ―６ / ℃ or more 12 x 10 ―６ / °C or less.

[0040] The method for forming the electrolyte 7 is not particularly limited, and may be a baking method, a spray coating method, a PVD method, a CVD method, or the like.

[0041] [Reaction prevention layer 8] The reaction prevention layer 8 is disposed between the electrolyte 7 and the oxygen electrode 9. The reaction prevention layer 8 is disposed on the opposite side of the electrolyte 7 from the hydrogen electrode 6. The reaction prevention layer 8 prevents the constituent elements of the electrolyte 7 from reacting with the constituent elements of the oxygen electrode 9 to form a layer with high electrical resistance.

[0042] The reaction prevention layer 8 is made of an oxide ion conductive material, such as GDC or SDC.

[0043] The porosity of the reaction prevention layer 8 is not particularly limited, but may be, for example, 0.1% to 50%. The thickness of the reaction prevention layer 8 is not particularly limited, but may be, for example, 1 μm to 50 μm.

[0044] The method for forming the reaction prevention layer 8 is not particularly limited, and may be a baking method, a spray coating method, a PVD method, a CVD method, or the like.

[0045] [Oxygen Electrode 9] The oxygen electrode 9 is disposed on the opposite side of the hydrogen electrode 6 with respect to the electrolyte 7. In this embodiment, the reaction prevention layer 8 is disposed between the electrolyte 7 and the oxygen electrode 9, and therefore the oxygen electrode 9 is connected to the reaction prevention layer 8. If the reaction prevention layer 8 is not disposed between the electrolyte 7 and the oxygen electrode 9, the oxygen electrode 9 is connected to the electrolyte 7.

[0046] The oxygen electrode 9 converts O 2 transferred from the hydrogen electrode 6 through the electrolyte 7 according to the chemical reaction of the following formula (5): ２－ From O ２ Generate.

[0047] Oxygen electrode 9:2O ２－ →O ２ +4e － ...(5)

[0048] The oxygen electrode 9 is a porous body having oxide ion conductivity and electron conductivity. The oxygen electrode 9 is, for example, (La, Sr)(Co, Fe)O ３ , (La,Sr)FeO ３ , La(Ni,Fe)O ３ , (La,Sr)CoO ３ , and (Sm,Sr)CoO ３ and an oxide ion conductive material (such as GDC).

[0049] The porosity of the oxygen electrode 9 is not particularly limited, but may be, for example, 20% to 60%. The thickness of the oxygen electrode 9 is not particularly limited, but may be, for example, 1 μm to 100 μm.

[0050] The method for forming the oxygen electrode 9 is not particularly limited, and may be a baking method, a spray coating method, a PVD method, a CVD method, or the like.

[0051] (Reducing Gas Container 3) The reducing gas container 3 contains a raw material gas supplied to the hydrogen electrode 6 and a reducing gas (in this embodiment, H ２ ) and has an internal space 3a through which the

[0052] In this embodiment, the reducing gas container 3 includes a metal support 10, a frame 20, an interconnector 30, a first seal portion 40, and a second seal portion 50. The internal space 3a is a space surrounded by the metal support 10, the frame 20, the interconnector 30, the first seal portion 40, and the second seal portion 50. The first seal portion 40 and the second seal portion 50 are each an example of a "seal portion" according to the present invention.

[0053] In this embodiment, one of the metal support 10 and the frame body 20 is an example of the "first metal member" according to the present invention, and the other is an example of the "second metal member" according to the present invention. Also, in this embodiment, one of the frame body 20 and the interconnector 30 is an example of the "first metal member" according to the present invention, and the other is an example of the "second metal member" according to the present invention.

[0054] [Metal Support 10] The metal support 10 supports the cell main body 2. In this embodiment, the metal support 10 is formed in a plate shape. The metal support 10 may be in a flat plate shape or a curved plate shape.

[0055] The metal support 10 is only required to be able to support the cell body 2, and its thickness is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less.

[0056] As shown in FIG. 2 , the metal support 10 has a plurality of supply holes 11 , a first main surface 12 and a second main surface 13 .

[0057] Each supply hole 11 penetrates the metal support 10 from the first main surface 12 to the second main surface 13. Each supply hole 11 opens to the first main surface 12 and the second main surface 13. Each supply hole 11 is covered by the cell main body 2. Specifically, the opening of each supply hole 11 on the first main surface 12 side is covered by the hydrogen electrode 6. The opening of each supply hole 11 on the second main surface 13 side is connected to the internal space 3 a.

[0058] Each supply hole 11 can be formed by mechanical processing (for example, punching), laser processing, chemical processing (for example, etching), or the like.

[0059] In this embodiment, each supply hole 11 is formed linearly along the Z-axis direction. However, each supply hole 11 may be inclined with respect to the Z-axis direction or may not be linear. Furthermore, the supply holes 11 may be connected to each other.

[0060] The first main surface 12 is provided on the opposite side to the second main surface 13. The cell main body 2 is disposed on the first main surface 12. The frame 20 is joined to the second main surface 13 via a first seal portion 40.

[0061] The metal support 10 is made of a metal material. For example, the metal support 10 can be made of an alloy material containing Cr (chromium). Examples of such metal materials include Fe—Cr alloy steel (stainless steel, etc.) and Ni—Cr alloy steel. The Cr content in the metal support 10 is not particularly limited, but can be set to 4 mass % or more and 30 mass % or less.

[0062] The metal support 10 may contain Ti (titanium) or Zr (zirconium). The Ti content in the metal support 10 is not particularly limited, but may be 0.01 mol % or more and 1.0 mol % or less. The Al content in the metal support 10 is not particularly limited, but may be 0.01 mol % or more and 0.4 mol % or less. The metal support 10 may contain Ti in the form of TiO ２ (titania), or Zr may be contained as ZrO ２ It may be contained as (zirconia).

[0063] [Frame 20] The frame 20 is a spacer for forming the internal space 3a. In this embodiment, the frame 20 is formed in an annular shape.

[0064] The frame 20 is joined to the metal support 10 via the first seal portion 40 , and is joined to the interconnector 30 via the second seal portion 50 .

[0065] The thickness of the frame body 20 is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less.

[0066] The frame 20 is made of a metal material. For example, the frame 20 can be made of the alloy material described above. The composition of the frame 20 may be the same as or different from that of the metal support 10.

[0067] [Interconnector 30] The interconnector 30 is disposed on the opposite side of the metal support 10 with respect to the frame 20. The interconnector 30 is a member for electrically connecting the electrolytic cell 1 to an external power source or another electrolytic cell.

[0068] In this embodiment, the interconnector 30 is formed in a plate shape. The interconnector 30 may be in a flat plate shape or a curved plate shape.

[0069] The interconnector 30 is joined to the frame 20 via the second seal portion 50 .

[0070] The thickness of the interconnector 30 is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less.

[0071] The interconnector 30 is made of a metal material. For example, the interconnector 30 can be made of the above-mentioned alloy material. The composition of the interconnector 30 may be the same as or different from that of the metal support 10. The composition of the interconnector 30 may be the same as or different from that of the frame 20.

[0072] [First Seal Portion 40] The first seal portion 40 is disposed between the metal support body 10 and the frame body 20. The first seal portion 40 is joined to both the metal support body 10 and the frame body 20.

[0073] The first seal 40 seals the gap between the metal support 10 and the frame 20. This prevents the source gas supplied to the hydrogen electrode 6 and the reducing gas generated in the hydrogen electrode 6 from leaking to the outside through the gap between the metal support 10 and the frame 20. The detailed configuration of the first seal 40 will be described later.

[0074] [Second seal portion 50] The second seal portion 50 is disposed between the frame body 20 and the interconnector 30. The second seal portion 50 is joined to both the frame body 20 and the interconnector 30.

[0075] The second seal portion 50 seals the gap between the frame 20 and the interconnector 30. This prevents the raw material gas supplied to the hydrogen electrode 6 and the reducing gas generated in the hydrogen electrode 6 from leaking to the outside through the gap between the frame 20 and the interconnector 30.

[0076] The configuration of the second seal portion 50 is the same as the configuration of the first seal portion 40, which will be described next, and therefore, in this embodiment, a description of the configuration of the second seal portion 50 will be omitted.

[0077] (Detailed Configuration of First Seal Portion 40) Fig. 3 is a partially enlarged view of Fig. 2. Fig. 3 shows a cross section of the first seal portion 40.

[0078] The first seal portion 40 has a first joint portion 41 , a second joint portion 42 and a third joint portion 43 .

[0079] [First joint portion 41] The first joint portion 41 is disposed between the metal support body 10 and the frame body 20. The first joint portion 41 is joined to each of the metal support body 10 and the frame body 20. The first joint portion 41 is formed integrally with each of the metal support body 10 and the frame body 20.

[0080] The first bonding portion 41 is made of a metal material. The composition of the first bonding portion 41 may be the same as the composition of the metal support 10, may be the same as the composition of the frame body 20, or may be a mixture of the metal support 10 and the frame body 20. Furthermore, the composition of the first bonding portion 41 may be different from the composition of the metal support 10 and the frame body 20.

[0081] The first joint portion 41 can be formed, for example, by welding the metal support body 10 and the frame body 20 together, or by brazing the metal support body 10 and the frame body 20 together. The first joint portion 41 according to this embodiment is formed by lap-welding the metal support body 10 and the frame body 20 together.

[0082] In this embodiment, the first bonding portion 41 is disposed on the opposite side of the internal space 3a from the second bonding portion 42. That is, the first bonding portion 41 is isolated from the internal space 3a by the second bonding portion 42. Therefore, the first bonding portion 41 is not exposed to the internal space 3a.

[0083] As a result, the reducing gas (in this embodiment, H ２ ) can be prevented from coming into contact with the first bonding portion 41, thereby preventing the first bonding portion 41 from being deteriorated (e.g., embrittlement) by the reducing gas. Furthermore, in this embodiment, water vapor flowing through the internal space 3 a can be prevented from coming into contact with the first bonding portion 41, thereby preventing the first bonding portion 41 from being corroded by water vapor.

[0084] In the present embodiment, the first bonding portion 41 is disposed on the opposite side of the external space 3b from the third bonding portion 43. That is, the first bonding portion 41 is isolated from the external space 3b by the third bonding portion 43. Therefore, the first bonding portion 41 is not exposed to the external space 3b.

[0085] This prevents water vapor contained in the air in the external space 3b from coming into contact with the first joint portion 41, thereby further preventing the first joint portion 41 from being corroded by water vapor.

[0086] [Second joint portion 42] The second joint portion 42 is disposed between the metal support body 10 and the frame body 20. The second joint portion 42 is sandwiched between the metal support body 10 and the frame body 20. The second joint portion 42 is disposed on the internal space 3a side of the first joint portion 41. The inner peripheral surface of the second joint portion 42 is exposed to the internal space 3a.

[0087] The second bonding portion 42 is made of a crystalline metal oxide. Crystalline metal oxides have higher chemical stability against reducing gas and water vapor than metallic materials. Therefore, by making the second bonding portion 42, which comes into contact with the reducing gas and water vapor flowing through the internal space 3a, of a crystalline metal oxide, deterioration of the second bonding portion 42 can be suppressed. Therefore, in addition to being able to suppress deterioration of the first bonding portion 41 as described above, the mechanical reliability of the first seal portion 40 can be improved.

[0088] The crystalline metal oxide constituting the second bonding portion 42 preferably contains a metal element contained in at least one of the metal support 10 and the frame 20. This can improve the adhesion between the second bonding portion 42 and at least one of the metal support 10 and the frame 20. As a result, the sealing performance of the gap between the metal support 10 and the frame 20 can be improved, and the first bonding portion 41 can be further prevented from coming into contact with reducing gas or water vapor.

[0089] It is preferable that the second bonding portion 42 is substantially free of boron (element B) and silicon (element Si). Since the second bonding portion 42 does not contain glass, the chemical stability of the second bonding portion 42 against reducing gas and water vapor can be further improved. Note that being substantially free of boron and silicon means that, when the boron and silicon contents are measured using an energy dispersive spectroscopy (EDS) device, the respective contents are below the detection limit or 1 mol% or less.

[0090] The crystalline metal oxide constituting the second bonding portion 42 is preferably composed of at least one of chromium oxide, chromium manganese oxide, and iron oxide. These oxides have high chemical stability against reducing gas and water vapor, and therefore can further suppress deterioration of the second bonding portion 42.

[0091] Chromium oxides include Cr ２ O ３ Examples of chromium manganese oxide include MnCr ２ O ４ (Spinel), Mn １，５ Cr １，５O ４ (spinel), etc. Examples of iron oxides include FeO, Fe ２ O ３ , Fe ３ O ４ Examples include:

[0092] The thermal expansion coefficient of the second joint 42 is preferably smaller than that of the metal support 10 and smaller than that of the frame 20. This allows compressive forces to be applied to the second joint 42 from both the metal support 10 and the frame 20 when the temperature of the reducing gas container 3 drops, thereby improving the strength of the second joint 42.

[0093] The second bonding portion 42 can be formed as follows. First, a paste containing a crystalline metal oxide is applied to the surface of at least one of the metal support 10 and the frame 20. Next, the metal support 10 and the frame 20 are welded together to form the first bonding portion 41. Next, the paste is fired to form the second bonding portion 42. The firing conditions can be set as appropriate, but can be, for example, 600°C to 1100°C and 0.5 hours to 24 hours.

[0094] [Third Joint 43] The third joint 43 is disposed between the metal support 10 and the frame 20. The third joint 43 is sandwiched between the metal support 10 and the frame 20. The third joint 43 is disposed on the opposite side of the second joint 42 with respect to the first joint 41. The outer peripheral surface of the third joint 43 is exposed to the external space 3b.

[0095] The third bonding portion 43 is made of a crystalline metal oxide. This prevents the third bonding portion 43 from being chemically deteriorated by water vapor contained in the air in the external space 3 b. This, combined with the ability to prevent deterioration of the first bonding portion 41 and the second bonding portion 42 as described above, further improves the mechanical reliability of the first seal portion 40.

[0096] The crystalline metal oxide constituting the third bonding portion 43 may be the same as or different from the crystalline metal oxide constituting the second bonding portion 42 .

[0097] The crystalline metal oxide constituting the third bonding portion 43 preferably contains a metal element contained in at least one of the metal support 10 and the frame body 20. This can improve the adhesion between the third bonding portion 43 and at least one of the metal support 10 and the frame body 20. As a result, the sealing performance of the gap between the metal support 10 and the frame body 20 can be improved, which can further prevent the first bonding portion 41 from coming into contact with water vapor contained in the air in the external space 3b.

[0098] It is preferable that the third bonding portion 43 is substantially free of boron and silicon. Since the third bonding portion 43 does not contain any glass, chemical deterioration of the third bonding portion 43 due to water vapor can be further suppressed.

[0099] The crystalline metal oxide constituting the third bonding portion 43 is preferably composed of at least one of chromium oxide, chromium manganese oxide, and iron oxide, which can further suppress deterioration of the third bonding portion 43.

[0100] The thermal expansion coefficient of the third joint 43 is preferably smaller than that of the metal support 10 and smaller than that of the frame 20. This allows compressive forces to be applied to the third joint 43 from both the metal support 10 and the frame 20 when the temperature of the reducing gas container 3 drops, thereby improving the strength of the third joint 43.

[0101] The third bonding portion 43 can be formed as follows. First, a paste containing a crystalline metal oxide is applied to the surface of at least one of the metal support 10 and the frame 20. Next, the metal support 10 and the frame 20 are welded together to form the first bonding portion 41. Next, the paste is fired to form the second bonding portion 42. The firing conditions can be set appropriately, but can be, for example, 600°C or higher and 1100°C or lower, and 0.5 hours or higher and 24 hours or lower. The third bonding portion 43 can be formed simultaneously with the second bonding portion 42.

[0102] (Planar Shape of First Seal Portion 40) FIG. 4 is a plan view of the first seal portion 40 as viewed from the metal support body 10 side.

[0103] In this embodiment, the first seal portion 40 is formed in an annular shape so as to surround the internal space 3 a. Specifically, the second bonding portion 42 is formed in an annular shape so as to surround the internal space 3 a, the first bonding portion 41 is formed in an annular shape so as to surround the second bonding portion 42, and the third bonding portion 43 is formed in an annular shape so as to surround the first bonding portion 41. This ensures a reliable sealing of the internal space 3 a.

[0104] 4, the first joint 41 has a plurality of short joints 41x and a plurality of intersections 41y. The first joint 41 is formed by connecting the short joints 41x to each other at the intersections 41y.

[0105] The cross-connection of the short joint portions 41x in this manner can prevent gaps from occurring between the short joint portions 41x compared to the case of butt-connection, thereby further improving the sealing performance of the first seal portion 40.

[0106] However, the first joint portion 41 does not necessarily have to include a plurality of short joint portions 41x. Even in this case, it is preferable that both ends of the first joint portion 41 are connected at the intersection portion 41y.

[0107] (Modifications of the Embodiment) Although the embodiment of the present invention has been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention.

[0108] [Modification 1] In the above embodiment, the frame body 20 and the interconnector 30 are separate members, but the frame body 20 and the interconnector 30 may be an integrated member. In this case, the reducing gas container 3 does not include the second seal portion 50.

[0109] [Modification 2] In the above embodiment, the metal support 10 and the frame 20 are separate members, but the metal support 10 and the frame 20 may be an integrated member. In this case, the reducing gas container 3 does not include the first seal portion 40.

[0110] [Modification 3] In the above embodiment, the first joint portion 41 is formed by lap welding the metal support body 10 and the frame body 20, but it may also be formed by edge welding the outer edges of the metal support body 10 and the frame body 20. In this case, the first seal portion 40 does not need to have the third joint portion 43.

[0111] [Variation 4] In the above embodiment, an electrolytic cell has been described as an example of an electrochemical cell, but the electrochemical cell is not limited to an 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, electrochemical cells include, for example, fuel cells that use oxide ions or protons as carriers.

[0112] [Modification 5] In the above embodiment, the reducing gas container according to the present invention is applied to an electrochemical cell, but the reducing gas container can be used for various applications using a reducing gas. For example, the reducing gas container can be applied to a methanation reactor that synthesizes methane from hydrogen and carbon dioxide.

[0113] REFERENCE SIGNS LIST 1 Electrolytic cell 2 Cell main body 3 Reducing gas container 3a Internal space 6 Hydrogen electrode 7 Electrolyte 8 Reaction prevention layer 9 Oxygen electrode 10 Metal support 11 Supply hole 12 First main surface 13 Second main surface 20 Frame 30 Interconnector 40 First seal portion 50 Second seal portion

Claims

1. A reducing gas container having an internal space through which a reducing gas flows, comprising: a first metal member; a second metal member; and a seal portion that seals between the first metal member and the second metal member, wherein the seal portion has a first joint portion that is integrally formed with each of the first and second metal members, and a second joint portion that is sandwiched between the first and second metal members and positioned on the internal space side of the first joint portion, wherein the first joint portion is made of a metal material, and the second joint portion is made of a crystalline metal oxide.

2. The reducing gas container according to claim 1, wherein the crystalline metal oxide constituting the second bonding portion contains a metal element contained in at least one of the first and second metal members.

3. The reducing gas container according to claim 2, wherein the second joint portion is substantially free of boron and silicon.

4. The reducing gas container according to claim 2 or 3, wherein the crystalline metal oxide constituting the second bonding portion is composed of at least one of chromium oxide, chromium manganese oxide and iron oxide.

5. The reducing gas container according to claim 1, wherein the thermal expansion coefficient of the second joint portion is smaller than the thermal expansion coefficients of the first and second metal members.

6. The reducing gas container according to claim 1, wherein the second joint portion is formed in an annular shape so as to surround the internal space, and the first joint portion is formed in an annular shape so as to surround the second joint portion.

7. The reducing gas container according to claim 6, wherein the first joint portion has an intersection portion in a plan view.

8. The reducing gas container as described in claim 1, wherein the sealing portion further has a third joint portion, the third joint portion being sandwiched between the first and second metal members and positioned on the opposite side of the second joint portion with respect to the first joint portion, and the third joint portion being composed of the crystalline metal oxide.

9. A metal-supported electrochemical cell comprising: a reducing gas container as described in claim 1; and a cell main body portion disposed on said reducing gas container, wherein said first metal member has a plurality of communication holes leading to said internal space, and said cell main body portion is disposed on said first metal member so as to cover said plurality of communication holes.

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