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WO2024201667A1 - Electrolytic cell - Google Patents

Electrolytic cell Download PDF

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Publication number
WO2024201667A1
WO2024201667A1 PCT/JP2023/012264 JP2023012264W WO2024201667A1 WO 2024201667 A1 WO2024201667 A1 WO 2024201667A1 JP 2023012264 W JP2023012264 W JP 2023012264W WO 2024201667 A1 WO2024201667 A1 WO 2024201667A1
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WO
WIPO (PCT)
Prior art keywords
region
oxygen electrode
central portion
metal member
electrode
Prior art date
Application number
PCT/JP2023/012264
Other languages
French (fr)
Japanese (ja)
Inventor
直哉 秋山
俊之 中村
誠 大森
Original Assignee
日本碍子株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日本碍子株式会社 filed Critical 日本碍子株式会社
Priority to PCT/JP2023/012264 priority Critical patent/WO2024201667A1/en
Publication of WO2024201667A1 publication Critical patent/WO2024201667A1/en

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C25B1/042—Hydrogen or oxygen by electrolysis of water by electrolysis of steam
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/23—Carbon monoxide or syngas
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/60—Constructional parts of cells
    • C25B9/65—Means for supplying current; Electrode connections; Electric inter-cell connections
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

  • the present invention relates to an electrolysis cell.
  • an electrolysis cell including a cell body having an electrolyte disposed between a hydrogen electrode and an oxygen electrode (see, for example, Patent Document 1).
  • a raw material gas is supplied to the hydrogen electrode, and oxygen (O 2 ) is produced at the oxygen electrode.
  • the electrolytic cell may have a metal member that is in contact with or faces the oxygen electrode.
  • the metal member include a separator used to stack the electrolytic cells and a current collecting member used to collect current.
  • the oxygen generated at the oxygen electrode may cause a noticeable oxide film to grow on the surface of the metal components.
  • the amount of oxygen generated is likely to increase due to current concentration caused by a rise in temperature due to heat buildup.
  • the part of the metal member that is in contact with or facing the center of the oxygen electrode is exposed to a highly oxidizing atmosphere.
  • the performance of the electrolysis cell is reduced due to the significant growth of an oxide film on the part of the metal member that is in contact with or facing the center of the oxygen electrode.
  • the objective of the present invention is to provide an electrolysis cell that can suppress performance degradation.
  • the electrolytic cell according to the first aspect of the present invention comprises a cell main body and a metal member.
  • the cell main body has a hydrogen electrode, an oxygen electrode, and an electrolyte disposed between the hydrogen electrode and the oxygen electrode.
  • the metal member is electrically connected to the oxygen electrode.
  • the oxygen electrode has a first region within 5 ⁇ m from the surface of the metal member and a second region more than 5 ⁇ m from the surface of the metal member.
  • the first region includes a central portion and an outer peripheral portion surrounding the central portion.
  • the porosity of the central portion is smaller than the porosity of the outer peripheral portion.
  • the electrolytic cell according to the second aspect of the present invention is the same as the first aspect, and the porosity of the second region is greater than the porosity of the central portion.
  • the present invention provides an electrolysis cell that can suppress performance degradation.
  • 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 of FIG.
  • FIG. 1 is a plan view of an electrolysis cell 1 according to an embodiment.
  • Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1.
  • Fig. 2 shows a cross section passing through a geometric center CP of an oxygen electrode 9, which will be described later.
  • a metal member 25 is omitted in Fig. 1.
  • Electrolytic cell 1 is a so-called metal-supported electrolytic cell.
  • the electrolytic cell 1 is formed in a plate shape extending in the X-axis and Y-axis directions.
  • 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.
  • 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, etc.
  • the X-axis direction and the Y-axis direction are the surface directions of the electrolytic cell 1
  • the Z-axis direction is the thickness direction of the electrolytic cell 1.
  • the electrolysis cell 1 includes a metal support 10, a cell body 20, a metal member 25, and a flow path member 30.
  • the metal support 10 supports the cell main body 20.
  • the metal support 10 is formed in a plate shape.
  • the metal support 10 may be in the shape of a flat plate or a curved plate.
  • the metal support 10 may have any thickness as long as it can support the cell main body 20, and may have any thickness, for example, 0.1 mm or more and 2.0 mm or less.
  • the thermal expansion coefficient of the metal support 10 is not particularly limited, and may have any thermal expansion coefficient, for example, 10 ⁇ 10 ⁇ 6 /° C. or more and 18 ⁇ 10 ⁇ 6 /° C. or less.
  • the metal support 10 has a plurality of communication holes 11, a first main surface 12, and a second main surface 13.
  • 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 both the first main surface 12 and the second main surface 13. The opening of each communication hole 11 on the first main surface 12 side is covered by the hydrogen electrode 6. The opening of each communication hole 11 on the second main surface 13 side is connected to a flow path 30a described below.
  • Each communication hole 11 can be formed by mechanical processing (e.g., punching), laser processing, or chemical processing (e.g., etching).
  • each communication hole 11 is formed linearly along the Z-axis direction.
  • each communication hole 11 may be inclined with respect to the Z-axis direction, and may not be linear.
  • the communication holes 11 may be connected to each other.
  • the first main surface 12 is provided on the opposite side to the second main surface 13.
  • the cell main body 20 is disposed on the first main surface 12.
  • the flow path member 30 is bonded to the second main surface 13.
  • the metal support 10 is made of a metal material.
  • the metal support 10 is 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.
  • Cr content in the metal support 10 can be 4% by mass or more and 30% by mass or less.
  • the metal support 10 may contain Ti (titanium) and 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 as TiO2 (titania) and Zr as ZrO2 (zirconia).
  • the metal support 10 may have an oxide film on its surface that is formed by oxidation of the constituent elements of the metal support 10.
  • a typical example of the oxide film is a chromium oxide film.
  • the chromium oxide film covers at least a portion of the surface of the metal support 10.
  • the chromium oxide film may also cover at least a portion of the inner wall surface of each communication hole 11.
  • the cell body 20 is disposed on the metal support 10.
  • the cell body 20 is supported by the metal support 10.
  • the cell body 20 has a hydrogen electrode 6 (cathode), an electrolyte 7, a reaction prevention layer 8, and an oxygen electrode 9 (anode).
  • the hydrogen electrode 6, electrolyte 7, reaction prevention layer 8, and oxygen electrode 9 are layered in this order in the Z-axis direction from the metal support 10 side.
  • the hydrogen electrode 6, electrolyte 7, and oxygen electrode 9 are required components, while the reaction prevention layer 8 is optional.
  • the hydrogen electrode 6 is disposed between the metal support 10 and the electrolyte 7.
  • the hydrogen electrode 6 is formed on a first main surface 12 of the metal support 10. In this embodiment, a portion of the hydrogen electrode 6 is disposed inside each of the communication holes 11 of the metal support 10, but the hydrogen electrode 6 does not have to extend into each of the communication holes 11 of the metal support 10.
  • a source gas is supplied to the hydrogen electrode 6 through each communication hole 11.
  • the source gas contains at least H2O .
  • the hydrogen electrode 6 produces H 2 from the source gas in accordance with the electrochemical reaction of water electrolysis shown in the following formula (1).
  • Hydrogen electrode 6 H 2 O + 2e ⁇ ⁇ H 2 + O 2 ⁇ (1)
  • the hydrogen electrode 6 produces H 2 , CO, and O 2 ⁇ from the source gas in accordance with the co-electrochemical reactions shown in the following formulas (2), (3), and (4).
  • Hydrogen electrode 6 CO 2 + H 2 O + 4e ⁇ ⁇ CO + H 2 + 2O 2 ⁇ (2) Electrochemical reaction of H 2 O: H 2 O + 2e ⁇ ⁇ H 2 + O 2 ⁇ (3) Electrochemical reaction of CO2 : CO2 + 2e- ⁇ CO + O2 -... (4)
  • the hydrogen electrode 6 is a porous body having electronic conductivity.
  • the hydrogen electrode 6 contains nickel (Ni) and an oxide ion conductive material.
  • Ni functions as an electronic conductor. In the case of co-electrolysis, Ni also functions as a thermal catalyst to promote the thermal reaction between the generated H2 and the CO2 contained in the feed gas to maintain a suitable gas composition for methanation, reverse water gas shift reaction, etc. Ni exists in the form of nickel oxide (NiO) in an oxidizing atmosphere and in the form of metallic Ni in a reducing atmosphere.
  • NiO nickel oxide
  • oxide ion conductive materials examples include YSZ, CSZ, ScSZ, GDC, SDC, (La,Sr)(Cr,Mn) O3 , (La,Sr) TiO3 , Sr2 (Fe,Mo) 2O6 , ( La ,Sr) VO3 , (La,Sr) FeO3 , and mixed materials of two or more of these.
  • the thickness of the hydrogen electrode 6 is not particularly limited, but can be, for example, 1 ⁇ m or more and 100 ⁇ m or less.
  • the method for forming the hydrogen electrode 6 is not particularly limited, and may be a sintering method, a spray coating method (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, etc.), a PVD method (sputtering, pulsed laser deposition, etc.), a CVD method, etc.
  • the electrolyte 7 is disposed between the hydrogen electrode 6 and the oxygen electrode 9.
  • the reaction prevention layer 8 is disposed between the electrolyte 7 and the oxygen electrode 9, so that the electrolyte 7 is sandwiched between the hydrogen electrode 6 and the reaction prevention layer 8.
  • the electrolyte 7 covers the hydrogen electrode 6 and also covers the area of the first main surface 12 of the metal support 10 that is exposed from the hydrogen electrode 6.
  • the electrolyte 7 transfers O 2- generated at the hydrogen electrode 6 to the oxygen electrode 9.
  • the electrolyte 7 is made of a dense material having oxide ion conductivity.
  • the electrolyte 7 can be made of, for example, YSZ (yttria-stabilized zirconia, e.g., 8YSZ), GDC (gadolinium-doped ceria), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), LSGM (lanthanum gallate), or the like.
  • the porosity of the electrolyte 7 is not particularly limited, but can be, for example, 0.1% to 7%.
  • the thickness of the electrolyte 7 is not particularly limited, but can be, for example, 1 ⁇ m to 100 ⁇ m.
  • the method for forming the electrolyte 7 is not particularly limited, and a baking method, a spray coating method, a PVD method, a CVD method, etc. can be used.
  • 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 to the hydrogen electrode 6. The reaction prevention layer 8 prevents a layer having a high electrical resistance from being formed due to a reaction between a constituent element of the electrolyte 7 and a constituent element of the oxygen electrode 9.
  • the reaction prevention layer 8 is made of an oxide ion conductive material.
  • the reaction prevention layer 8 can be made of GDC, SDC, etc.
  • the porosity of the reaction prevention layer 8 is not particularly limited, but can be, for example, 0.1% to 50%.
  • the thickness of the reaction prevention layer 8 is not particularly limited, but can be, for example, 1 ⁇ m to 50 ⁇ m.
  • the method for forming the reaction prevention layer 8 is not particularly limited, and a baking method, a spray coating method, a PVD method, a CVD method, etc. can be used.
  • the oxygen electrode 9 is disposed on the opposite side of the hydrogen electrode 6 with respect to the electrolyte 7. In this embodiment, since the reaction prevention layer 8 is disposed between the electrolyte 7 and the oxygen electrode 9, 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.
  • the oxygen electrode 9 has a surface 93 on the metal member 25 side (hereinafter referred to as the "metal member side surface").
  • the oxygen electrode 9 produces oxygen (O 2 ) from O 2 ⁇ transferred from the hydrogen electrode 6 via the electrolyte 7 in accordance with the chemical reaction of the following formula (5).
  • Oxygen electrode 9 2O 2 ⁇ ⁇ O 2 + 4e ⁇ (5)
  • the porosity of the oxygen electrode 9 is not particularly limited, but can be, for example, 20% or more and 60% or less.
  • the thickness of the oxygen electrode 9 is not particularly limited, but can be, for example, 1 ⁇ m or more and 100 ⁇ m or less. The detailed configuration of the oxygen electrode 9 will be described later.
  • the method for forming the oxygen electrode 9 is not particularly limited, and methods such as baking, spray coating, PVD, and CVD can be used.
  • the metal member 25 is electrically connected to the oxygen electrode 9.
  • the metal member 25 is electrically connected to the oxygen electrode 9 via a conductive bonding material 26.
  • the metal member 25 may be electrically connected to the oxygen electrode 9 by direct contact with the oxygen electrode 9. In this case, the metal member 25 does not need to be fixed to the oxygen electrode 9.
  • the metal member 25 in this embodiment functions as a current collecting member.
  • the metal member 25 is electrically connected to the interconnector 32 (described later) that is provided in the other electrolysis cells.
  • the metal member 25 may be made of, for example, ferritic stainless steel, but the material of the metal member 25 is not particularly limited.
  • the surface of the metal member 25 may be covered with a conductive coating.
  • At least a portion of the surface of the metal member 25 may be covered with an oxide film formed by oxidation of the constituent elements of the metal member 25.
  • a typical example of the oxide film is a chromium oxide film. When an oxide film is present, the oxide film is considered to constitute a part of the metal member 25.
  • At least a portion of the surface of the metal member 25, or at least a portion of the oxide film covering the surface of the metal member 25, may be covered with an oxidation-resistant coating film.
  • a typical example of an oxidation-resistant coating film is a manganese-cobalt composite oxide film.
  • the oxide film constitutes a part of the metal member 25.
  • the oxidation-resistant coating film constitutes a part of the metal member 25.
  • the oxidation-resistant coating film can suppress the oxidation of the metal member 25, it is generally difficult to completely prevent the oxidation of the metal member 25 using the oxidation-resistant coating film.
  • the metal member 25 is exposed to a strongly oxidizing atmosphere, the oxidation of the metal member 25 cannot be completely prevented even if an oxidation-resistant coating film is formed, and an oxide film grows on the surface of the metal member 25.
  • 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 itself and the metal support 10.
  • a source gas is supplied to the flow path 30a.
  • the source gas supplied to the flow path 30a is supplied to the hydrogen electrode 6 of the cell main body 20 through each communication hole 11 of the metal support 10.
  • the flow path member 30 can be made of, for example, an alloy material.
  • the flow path member 30 may be made 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.
  • 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 body 10.
  • the interconnector 32 is a plate-shaped member for electrically connecting an external power source or another electrolysis cell in series with the electrolysis cell 1.
  • the interconnector 32 is joined to the frame body 31.
  • the frame body 31 and the interconnector 32 are separate members, but the frame body 31 and the interconnector 32 may be an integrated member.
  • the oxygen electrode 9 has a first region 91 and a second region 92.
  • the first region 91 is a region of the oxygen electrode 9 that is within 5 ⁇ m from the metal member side surface 93.
  • the second region 92 is a region of the oxygen electrode 9 that is more than 5 ⁇ m from the metal member side surface 93. In other words, the second region 92 is a region of the oxygen electrode 9 excluding the first region 91.
  • the first region 91 is made of a porous material having electron conductivity.
  • the first region 91 may be made of, for example, one or more of (La,Sr)(Co,Fe) O3 , (La,Sr) FeO3 , La(Ni,Fe) O3 , (La,Sr)CoO3, (Sm,Sr) CoO3 , La(Ni,Fe,Cu) O3 , and (La,Sr) MnO3 .
  • the first region 91 may further include an oxide ion conductive material (such as GDC).
  • the second region 92 is made of a porous material having electron conductivity.
  • the first region 91 can be made of, for example, one or more of (La,Sr)(Co,Fe) O3 , (La,Sr) FeO3 , La(Ni,Fe) O3 , (La,Sr)CoO3, (Sm,Sr) CoO3 , La(Ni,Fe,Cu) O3 , and (La,Sr) MnO3 .
  • the second region 92 may further include an oxide ion conductive material (such as GDC).
  • composition of the first region 91 may be the same as or different from the composition of the second region 92.
  • the central portion 91a is a portion including the geometric center CP of the oxygen electrode 9 in plan view.
  • the planar shape of the oxygen electrode 9 in plan view is rectangular, and the planar shape of the central portion 91a in plan view is also rectangular.
  • the central portion 91a is located inside the oxygen electrode 9.
  • the planar shape of the central portion 91a is similar to the planar shape of the oxygen electrode 9.
  • the predetermined magnification is not particularly limited, but can be, for example, 1.2 times or more and 4 times or less. In this embodiment, the predetermined magnification is 2.0 times, and when the outer edge of the central portion 91a is enlarged by 2 times, it becomes congruent with the outer edge of the oxygen electrode 9.
  • the planar shape and size of each of the oxygen electrode 9 and the central portion 91a can be changed as appropriate. Therefore, the planar shapes of the oxygen electrode 9 and the central portion 91a may each be a shape other than a rectangle (for example, a polygon other than a rectangle, an ellipse, a circle, etc.). The planar shape of the central portion 91a may also be different from the planar shape of the oxygen electrode 9. The total area of the oxygen electrodes 9 in a planar view can be 1.44 to 16 times the area of the central portion 91a in a planar view.
  • the outer peripheral portion 91b is a portion that surrounds the central portion 91a in a plan view.
  • the outer peripheral portion 91b is formed in a ring shape in a plan view.
  • the planar shape of the outer peripheral portion 91b can be changed as appropriate according to the planar shapes of the oxygen electrode 9 and the central portion 91a.
  • the porosity of the central portion 91a is smaller than that of the outer peripheral portion 91b. This can prevent the oxide film from growing significantly on the metal member 25. Specifically, this is as follows. In the oxygen electrode 9, heat is likely to accumulate in the central portion 92a (see FIG. 2) of the second region 92, which is in contact with the central portion 91a of the first region 91. Therefore, a large amount of oxygen is generated in the central portion 92a due to current concentration caused by a rise in temperature. However, since the porosity of the central portion 91a is smaller than that of the outer peripheral portion 91b, the oxygen generated in the central portion 92a is likely to flow toward the outer peripheral portion 91b rather than the central portion 91a.
  • the porosity of the second region 92 is preferably greater than the porosity of the central portion 91a. This allows oxygen generated in the central portion 92a of the second region 92 to flow more easily toward the outer periphery 91b. This makes it possible to further suppress the growth of an oxide film in the portion of the metal member 25 that comes into contact with the central portion 91a.
  • the porosity of the central portion 91a is not particularly limited, but can be, for example, 20% to 40%.
  • the porosity of the outer peripheral portion 91b is not particularly limited, but can be, for example, 25% to 45%.
  • the porosity of the second region 92 is not particularly limited, but can be, for example, 20% or more and 45% or less.
  • the porosity of the outer peripheral portion 91b of the first region 91 is calculated by dividing the total area of the pores by the total area of the backscattered electron image of the outer peripheral portion 91b, similar to the porosity of the central portion 91a.
  • the oxygen electrode 9 is produced by forming a second region 92 on the reaction prevention layer 8 using the constituent material for the second region, forming a central portion 91a on the second region 92 using the constituent material for the central portion of the first region 91, and then forming a peripheral portion 91b surrounding the central portion 91a using the constituent material for the peripheral portion of the first region 91.
  • the porosity of each of the central portion 91a of the first region 91, the outer peripheral portion 91b of the first region 91, and the second region 92 can be adjusted by the amount of pore-forming material added, the particle size of the raw material powder, the material composition, and the material type, but adjustment by the amount of pore-forming material added is preferred because it has little effect on electrode performance.
  • the metal member 25 functions as a current collecting member, but is not limited thereto.
  • the metal member 25 may be electrically connected to the air electrode 9.
  • the metal member 25 may be an interconnector 32 provided in another electrolysis cell.
  • the metal support type electrolytic cell 1 has been described as an example of an electrolytic cell.
  • the electrolytic cell according to the present invention may be a flat plate type that does not include a metal support 10.
  • a slurry for the hydrogen electrode layer was prepared by mixing GDC powder, NiO powder, butyral resin, polymethyl methacrylate beads as a pore-forming material, a plasticizer, a dispersant, and a solvent.
  • the slurry for the hydrogen electrode layer was then printed on the first main surface of the metal support by the doctor blade method to form a hydrogen electrode layer compact.
  • a slurry for the electrolyte layer was prepared by mixing YSZ powder, butyral resin, plasticizer, dispersant, and solvent.
  • the electrolyte slurry was then printed using a doctor blade method to cover the green body of the hydrogen electrode layer, forming a green body for the electrolyte layer.
  • a slurry for the reaction prevention layer was prepared by mixing GDC powder, polyvinyl alcohol, and a solvent.
  • the slurry for the reaction prevention layer was then printed on the electrolyte layer compact by the doctor blade method to form a reaction prevention layer compact.
  • the molded bodies of the hydrogen electrode layer, electrolyte layer, and reaction prevention layer arranged in sequence on the metal support were fired in air (1050°C, 1 hour) to form the hydrogen electrode layer, electrolyte layer, and reaction prevention layer.
  • a slurry for the oxygen electrode layer was prepared by mixing (La, Sr) (Co, Fe) O3 powder, polyvinyl alcohol, a solvent, and a pore former. At this time, the amount of the pore former added was adjusted to change the porosity of the entire oxygen electrode for each comparative example, as shown in Table 1. Then, the slurry for the oxygen electrode layer was printed on the reaction prevention layer by the doctor blade method to form a compact for the oxygen electrode layer.
  • the oxygen electrode layer compact was sintered in air (1000°C, 1 hour) to form the oxygen electrode.
  • Examples 1 to 7 Electrolytic cells according to Examples 1 to 7 were fabricated in the same manner as in Comparative Examples 1 and 2, except that the oxygen electrode layer had a two-layer structure.
  • a slurry for the second region was prepared by mixing (La, Sr) (Co, Fe) O3 powder, polyvinyl alcohol, a solvent, and a pore former.
  • the amount of the pore former added was adjusted to change the porosity of the second region of the oxygen electrode for each example, as shown in Table 1.
  • the slurry for the second region was printed on the reaction prevention layer by a doctor blade method to form a compact for the second region of the oxygen electrode.
  • a slurry for the center of the first region was prepared by mixing (La,Sr)(Co,Fe) O3 powder, polyvinyl alcohol, a solvent, and a pore former.
  • the amount of the pore former added was adjusted to change the porosity of the center of the first region of the oxygen electrode for each example, as shown in Table 1.
  • the slurry for the center of the first region was printed on the center of the compact for the second region by a doctor blade method, thereby forming a compact for the center of the first region of the oxygen electrode.
  • a slurry for the outer periphery of the first region was prepared by mixing (La, Sr) (Co, Fe) O 3 powder, polyvinyl alcohol, a solvent, and a pore former.
  • the amount of the pore former added was adjusted to change the porosity of the outer periphery of the first region of the oxygen electrode for each example, as shown in Table 1.
  • the slurry for the outer periphery of the first region was printed by a doctor blade method so as to surround the compact of the first region, thereby forming a compact of the outer periphery of the first region of the oxygen electrode.
  • the molded bodies of the first and second regions were sintered in air (1000°C, 1 hour) to form an oxygen electrode.
  • a mixed gas of water vapor and hydrogen (mixing ratio 90:10) was supplied to the hydrogen electrode layer while a mixed gas of oxygen and nitrogen (mixing ratio 21:79) was supplied to the oxygen electrode layer, and a current was passed so that the current density per hydrogen electrode layer area was constant at 0.5 A/ cm2 to perform electrolysis, and the cell voltage (hereinafter referred to as "initial cell voltage”) was measured.
  • cell voltage after durability test the cell voltage after 1000 hours of holding in a state where the current density was fixed at 0.5 A/cm 2 while supplying the mixed gas to each of the hydrogen electrode layer and the oxygen electrode layer.
  • Performance degradation rate (%) 100 ⁇ (cell voltage after durability test - initial cell voltage) / initial cell voltage... (6)
  • a performance degradation rate of less than 4% was evaluated as "A”
  • a performance degradation rate of 4% or more and less than 7% was evaluated as "O”
  • a performance degradation rate of 7% or more was evaluated as "X”.
  • Electrolysis cell 10
  • Metal support 11 Through hole 12
  • First main surface 13
  • Second main surface 20
  • Cell body 6
  • Hydrogen electrode 7
  • Electrolyte 8
  • Reaction prevention layer 9
  • Oxygen electrode 91
  • First region 91a Central portion 91b Outer peripheral portion 92
  • Second region 92a Central portion 30
  • Flow path member 30a Flow path

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Abstract

An electrolytic cell (1) comprises a cell body (20) and a metal member (25). An oxygen electrode (9) of the cell body (20) has a first region (91) within 5 μm from a metal member-side surface (93). The first region (91) includes a central part (91a) and an outer peripheral part (91b). The porosity of the central part (91a) is smaller than the porosity of the outer peripheral part (91b).

Description

電解セルElectrolysis Cell
　本発明は、電解セルに関する。 The present invention relates to an electrolysis cell.
　従来、水素極と酸素極の間に配置された電解質を有するセル本体部を備える電解セルが知られている（例えば、特許文献１参照）。水素極には原料ガスが供給され、酸素極では酸素（Ｏ２）が生成される。 Conventionally, there has been known an electrolysis cell including a cell body having an electrolyte disposed between a hydrogen electrode and an oxygen electrode (see, for example, Patent Document 1). A raw material gas is supplied to the hydrogen electrode, and oxygen (O 2 ) is produced at the oxygen electrode.
　また、セル本体部が金属支持体上に配置された電解セルも知られている（例えば、特許文献２参照）。 Also known is an electrolytic cell in which the cell body is arranged on a metal support (see, for example, Patent Document 2).
特開２０２３－００４３９９号JP 2023-004399 A 特開２０２０－１５５３３７号JP 2020-155337 A
　ここで、電解セルは、酸素極と接触又は対向する金属部材を備える場合がある。金属部材としては、例えば、電解セルをスタックするために用いられるセパレータや、集電のために用いられる集電部材などが挙げられる。 Here, the electrolytic cell may have a metal member that is in contact with or faces the oxygen electrode. Examples of the metal member include a separator used to stack the electrolytic cells and a current collecting member used to collect current.
　電解セルが金属部材を備える場合、酸素極において生成される酸素によって金属部材の表面に酸化皮膜が顕著に成長してしまう場合がある。 If the electrolytic cell includes metal components, the oxygen generated at the oxygen electrode may cause a noticeable oxide film to grow on the surface of the metal components.
　具体的には、酸素極を平面視したときの中央部では、熱ごもりによる温度上昇で電流集中が生じることに起因して酸素の生成量が増加しやすい。加えて、中央部で発生した酸素はスタック外部へ排出されづらいため、金属部材のうち酸素極の中央部と接触又は対向する部分が強酸化性雰囲気に曝される。その結果、金属部材のうち酸素極の中央部と接触又は対向する部分における酸化皮膜の顕著な成長に起因する電解セルの性能低下が生じてしまう。 Specifically, in the center of the oxygen electrode when viewed from above, the amount of oxygen generated is likely to increase due to current concentration caused by a rise in temperature due to heat buildup. In addition, since the oxygen generated in the center is difficult to discharge to the outside of the stack, the part of the metal member that is in contact with or facing the center of the oxygen electrode is exposed to a highly oxidizing atmosphere. As a result, the performance of the electrolysis cell is reduced due to the significant growth of an oxide film on the part of the metal member that is in contact with or facing the center of the oxygen electrode.
　本発明の課題は、性能低下を抑制可能な電解セルを提供することにある。 The objective of the present invention is to provide an electrolysis cell that can suppress performance degradation.
　本発明の第１の側面に係る電解セルは、セル本体部と、金属部材とを備える。セル本体部は、水素極と、酸素極と、前記水素極及び前記酸素極の間に配置される電解質とを有する。金属部材は、前記酸素極と電気的に接続される。前記酸素極は、金属部材側表面から５μｍ以内の第１領域と、前記金属部材側表面から５μｍ超の第２領域とを有する。前記第１領域は、中央部と、前記中央部を取り囲む外周部とを含む。前記中央部の気孔率は、前記外周部の気孔率より小さい。 The electrolytic cell according to the first aspect of the present invention comprises a cell main body and a metal member. The cell main body has a hydrogen electrode, an oxygen electrode, and an electrolyte disposed between the hydrogen electrode and the oxygen electrode. The metal member is electrically connected to the oxygen electrode. The oxygen electrode has a first region within 5 μm from the surface of the metal member and a second region more than 5 μm from the surface of the metal member. The first region includes a central portion and an outer peripheral portion surrounding the central portion. The porosity of the central portion is smaller than the porosity of the outer peripheral portion.
　本発明の第２の側面に係る電解セルは、上記第１の側面に係り、前記第２領域の気孔率は、前記中央部の気孔率より大きい。 The electrolytic cell according to the second aspect of the present invention is the same as the first aspect, and the porosity of the second region is greater than the porosity of the central portion.
　本発明によれば、性能低下を抑制可能な電解セルを提供することができる。 The present invention provides an electrolysis cell that can suppress performance degradation.
図１は、実施形態に係る電解セルの平面図である。FIG. 1 is a plan view of an electrolysis cell according to an embodiment. 図２は、図１のＡ－Ａ断面図である。FIG. 2 is a cross-sectional view taken along line AA of FIG.
　（電解セル１）
　図１は、実施形態に係る電解セル１の平面図である。図２は、図１のＡ－Ａ断面図である。図２には、後述する酸素極９の幾何中心ＣＰを通る断面が図示されている。ただし、図１では、金属部材２５が省略されている。 (Electrolysis Cell 1)
Fig. 1 is a plan view of an electrolysis cell 1 according to an embodiment. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 2 shows a cross section passing through a geometric center CP of an oxygen electrode 9, which will be described later. However, a metal member 25 is omitted in Fig. 1.
　電解セル１は、いわゆるメタルサポート型の電解セルである。 Electrolytic cell 1 is a so-called metal-supported electrolytic cell.
　電解セル１は、Ｘ軸方向及びＹ軸方向に広がる板状に形成される。本実施形態において、電解セル１は、Ｘ軸方向及びＹ軸方向に垂直なＺ軸方向から平面視した場合、Ｙ軸方向に延びる長方形に形成される。ただし、電解セル１の平面形状は特に限られず、長方形以外の多角形、楕円形、円形などであってもよい。 The electrolytic cell 1 is formed in a plate shape extending in the X-axis and Y-axis directions. In this 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, etc.
　なお、Ｘ軸方向及びＹ軸方向それぞれは電解セル１の面方向であり、Ｚ軸方向は電解セル１の厚み方向である。 Note that the X-axis direction and the Y-axis direction are the surface directions of the electrolytic cell 1, and the Z-axis direction is the thickness direction of the electrolytic cell 1.
　図２に示すように、電解セル１は、金属支持体１０、セル本体部２０、金属部材２５、及び流路部材３０を備える。 As shown in FIG. 2, the electrolysis cell 1 includes a metal support 10, a cell body 20, a metal member 25, and a flow path member 30.
　［金属支持体１０］
　金属支持体１０は、セル本体部２０を支持する。金属支持体１０は、板状に形成される。金属支持体１０は、平板状であってもよいし、曲板状であってもよい。 [Metal support 10]
The metal support 10 supports the cell main body 20. The metal support 10 is formed in a plate shape. The metal support 10 may be in the shape of a flat plate or a curved plate.
　金属支持体１０はセル本体部２０を支持できればよく、その厚みは特に制限されないが、例えば０．１ｍｍ以上２．０ｍｍ以下とすることができる。金属支持体１０の熱膨張係数の値は特に限られないが、例えば１０×１０―６／℃以上１８×１０―６／℃以下とすることができる。 The metal support 10 may have any thickness as long as it can support the cell main body 20, and may have any thickness, for example, 0.1 mm or more and 2.0 mm or less. The thermal expansion coefficient of the metal support 10 is not particularly limited, and may have any thermal expansion coefficient, for example, 10×10 −6 /° C. or more and 18×10 −6 /° C. or less.
　図２に示すように、金属支持体１０は、複数の連通孔１１、第１主面１２及び第２主面１３を有する。 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.
　各連通孔１１は、第１主面１２から第２主面１３まで金属支持体１０を貫通する。各連通孔１１は、第１主面１２及び第２主面１３それぞれに開口する。各連通孔１１の第１主面１２側の開口は、水素極６によって覆われる。各連通孔１１の第２主面１３側の開口は、後述する流路３０ａに繋がる。 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 both the first main surface 12 and the second main surface 13. The opening of each communication hole 11 on the first main surface 12 side is covered by the hydrogen electrode 6. The opening of each communication hole 11 on the second main surface 13 side is connected to a flow path 30a described below.
　各連通孔１１は、機械加工（例えば、パンチング加工）、レーザ加工、或いは、化学加工（例えば、エッチング加工）などによって形成することができる。 Each communication hole 11 can be formed by mechanical processing (e.g., punching), laser processing, or chemical processing (e.g., etching).
　本実施形態において、各連通孔１１は、Ｚ軸方向に沿って直線状に形成される。ただし、各連通孔１１は、Ｚ軸方向に対して傾斜していてもよいし、直線状でなくてもよい。また、連通孔１１どうしが互いに連なっていてもよい。 In this 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, and may not be linear. Furthermore, the communication holes 11 may be connected to each other.
　第１主面１２は、第２主面１３の反対側に設けられる。第１主面１２には、セル本体部２０が配置される。第２主面１３には、流路部材３０が接合される。 The first main surface 12 is provided on the opposite side to the second main surface 13. The cell main body 20 is disposed on the first main surface 12. The flow path member 30 is bonded to the second main surface 13.
　金属支持体１０は、金属材料によって構成される。例えば、金属支持体１０は、Ｃｒ（クロム）を含有する合金材料によって構成される。このような金属材料としては、Ｆｅ－Ｃｒ系合金鋼（ステンレス鋼など）やＮｉ－Ｃｒ系合金鋼などが挙げられる。金属支持体１０におけるＣｒの含有率は特に制限されないが、４質量％以上３０質量％以下とすることができる。 The metal support 10 is made of a metal material. For example, the metal support 10 is 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. There are no particular restrictions on the Cr content in the metal support 10, but it can be 4% by mass or more and 30% by mass or less.
　金属支持体１０は、Ｔｉ（チタン）やＺｒ（ジルコニウム）を含有していてもよい。金属支持体１０におけるＴｉの含有率は特に制限されないが、０．０１ｍｏｌ％以上１．０ｍｏｌ％以下とすることができる。金属支持体１０におけるＡｌの含有率は特に制限されないが、０．０１ｍｏｌ％以上０．４ｍｏｌ％以下とすることができる。金属支持体１０は、ＴｉをＴｉＯ２（チタニア）として含有していてもよいし、ＺｒをＺｒＯ２（ジルコニア）として含有していてもよい。 The metal support 10 may contain Ti (titanium) and 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 as TiO2 (titania) and Zr as ZrO2 (zirconia).
　金属支持体１０は、金属支持体１０の構成元素が酸化することによって形成される酸化皮膜を表面に有していてよい。酸化膜としては、例えば酸化クロム膜が代表的である。酸化クロム膜は、金属支持体１０の表面の少なくとも一部を覆う。また、酸化クロム膜は、各連通孔１１の内壁面の少なくとも一部を覆っていてもよい。 The metal support 10 may have an oxide film on its surface that is formed by oxidation of the constituent elements of the metal support 10. A typical example of the oxide film is a chromium oxide film. The chromium oxide film covers at least a portion of the surface of the metal support 10. The chromium oxide film may also cover at least a portion of the inner wall surface of each communication hole 11.
　［セル本体部２０］
　セル本体部２０は、金属支持体１０上に配置される。セル本体部２０は、金属支持体１０によって支持される。セル本体部２０は、水素極６（カソード）、電解質７、反応防止層８、及び酸素極９（アノード）を有する。 [Cell body 20]
The cell body 20 is disposed on the metal support 10. The cell body 20 is supported by the metal support 10. The cell body 20 has a hydrogen electrode 6 (cathode), an electrolyte 7, a reaction prevention layer 8, and an oxygen electrode 9 (anode).
　水素極６、電解質７、反応防止層８、及び酸素極９は、Ｚ軸方向において、この順で金属支持体１０側から積層されている。水素極６、電解質７、及び酸素極９は必須の構成であり、反応防止層８は任意の構成である。 The hydrogen electrode 6, electrolyte 7, reaction prevention layer 8, and oxygen electrode 9 are layered in this order in the Z-axis direction from the metal support 10 side. The hydrogen electrode 6, electrolyte 7, and oxygen electrode 9 are required components, while the reaction prevention layer 8 is optional.
　［水素極６］
　水素極６は、金属支持体１０及び電解質７の間に配置される。水素極６は、金属支持体１０の第１主面１２上に形成される。本実施形態では、水素極６の一部が、金属支持体１０の各連通孔１１の内側に配置されているが、水素極６は、金属支持体１０の各連通孔１１に入り込んでいなくてもよい。 [Hydrogen electrode 6]
The hydrogen electrode 6 is disposed between the metal support 10 and the electrolyte 7. The hydrogen electrode 6 is formed on a first main surface 12 of the metal support 10. In this embodiment, a portion of the hydrogen electrode 6 is disposed inside each of the communication holes 11 of the metal support 10, but the hydrogen electrode 6 does not have to extend into each of the communication holes 11 of the metal support 10.
　水素極６には、各連通孔１１を介して原料ガスが供給される。原料ガスは、少なくともＨ２Ｏを含む。 A source gas is supplied to the hydrogen electrode 6 through each communication hole 11. The source gas contains at least H2O .
　原料ガスがＨ２Ｏのみを含む場合、水素極６は、下記（１）式に示す水電解の電気化学反応に従って、原料ガスからＨ２を生成する。 When the source gas contains only H 2 O, the hydrogen electrode 6 produces H 2 from the source gas in accordance with the electrochemical reaction of water electrolysis shown in the following formula (1).
　・水素極６：Ｈ２Ｏ＋２ｅ－→Ｈ２＋Ｏ２－・・・（１） Hydrogen electrode 6: H 2 O + 2e − → H 2 + O 2− (1)
　原料ガスがＨ２Ｏに加えてＣＯ２を含む場合、水素極６は、下記（２）、（３）、（４）式に示す共電解の電気化学反応に従って、原料ガスからＨ２、ＣＯ及びＯ２－を生成する。 When the source gas contains CO 2 in addition to H 2 O, the hydrogen electrode 6 produces H 2 , CO, and O 2− from the source gas in accordance with the co-electrochemical reactions shown in the following formulas (2), (3), and (4).
　・水素極６：ＣＯ２＋Ｈ２Ｏ＋４ｅ－→ＣＯ＋Ｈ２＋２Ｏ２－・・・（２）
　・Ｈ２Ｏの電気化学反応：Ｈ２Ｏ＋２ｅ－→Ｈ２＋Ｏ２－・・・（３）
　・ＣＯ２の電気化学反応：ＣＯ２＋２ｅ－→ＣＯ＋Ｏ２－・・・（４） Hydrogen electrode 6: CO 2 + H 2 O + 4e − → CO + H 2 + 2O 2− (2)
Electrochemical reaction of H 2 O: H 2 O + 2e − → H 2 + O 2− (3)
Electrochemical reaction of CO2 : CO2 + 2e- → CO + O2 -... (4)
　水素極６は、電子伝導性を有する多孔体である。水素極６は、ニッケル（Ｎｉ）と酸化物イオン伝導性材料とを含有する。 The hydrogen electrode 6 is a porous body having electronic conductivity. The hydrogen electrode 6 contains nickel (Ni) and an oxide ion conductive material.
　Ｎｉは、電子伝導物質として機能する。共電解の場合、Ｎｉは、生成されるＨ２と原料ガスに含まれるＣＯ２との熱的反応を促進してメタネーションや逆水性ガスシフト反応などに適切なガス組成を維持する熱触媒としても機能する。Ｎｉは、酸化雰囲気において酸化ニッケル（ＮｉＯ）の状態で存在し、還元雰囲気において金属Ｎｉの状態で存在する。 Ni functions as an electronic conductor. In the case of co-electrolysis, Ni also functions as a thermal catalyst to promote the thermal reaction between the generated H2 and the CO2 contained in the feed gas to maintain a suitable gas composition for methanation, reverse water gas shift reaction, etc. Ni exists in the form of nickel oxide (NiO) in an oxidizing atmosphere and in the form of metallic Ni in a reducing atmosphere.
　酸化物イオン伝導性材料としては、ＹＳＺ、ＣＳＺ、ＳｃＳＺ、ＧＤＣ、ＳＤＣ、（Ｌａ，Ｓｒ）（Ｃｒ，Ｍｎ）Ｏ３、（Ｌａ，Ｓｒ）ＴｉＯ３、Ｓｒ２（Ｆｅ,Ｍｏ）２Ｏ６、（Ｌａ，Ｓｒ）ＶＯ３、（Ｌａ，Ｓｒ）ＦｅＯ３、及びこれらのうち２つ以上を組み合わせた混合材料などを用いることができる。 Examples of oxide ion conductive materials that can be used include YSZ, CSZ, ScSZ, GDC, SDC, (La,Sr)(Cr,Mn) O3 , (La,Sr) TiO3 , Sr2 (Fe,Mo) 2O6 , ( La ,Sr) VO3 , (La,Sr) FeO3 , and mixed materials of two or more of these.
　水素極６の厚みは特に制限されないが、例えば１μｍ以上１００μｍ以下とすることができる。 The thickness of the hydrogen electrode 6 is not particularly limited, but can be, for example, 1 μm or more and 100 μm or less.
　水素極６の形成方法は特に制限されず、焼成法、スプレーコーティング法（溶射法、エアロゾルデポジション法、エアロゾルガスデポジッション法、パウダージェットデポジッション法、パーティクルジェットデポジション法、コールドスプレー法など）、ＰＶＤ法（スパッタリング法、パルスレーザーデポジション法など）、ＣＶＤ法などを用いることができる。 The method for forming the hydrogen electrode 6 is not particularly limited, and may be a sintering method, a spray coating method (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, etc.), a PVD method (sputtering, pulsed laser deposition, etc.), a CVD method, etc.
　［電解質７］
　電解質７は、水素極６及び酸素極９の間に配置される。本実施形態では、電解質７及び酸素極９の間に反応防止層８が配置されているので、電解質７は、水素極６及び反応防止層８の間に挟まれている。 [Electrolyte 7]
The electrolyte 7 is disposed between the hydrogen electrode 6 and the oxygen electrode 9. In this embodiment, the reaction prevention layer 8 is disposed between the electrolyte 7 and the oxygen electrode 9, so that the electrolyte 7 is sandwiched between the hydrogen electrode 6 and the reaction prevention layer 8.
　電解質７は、水素極６を覆うとともに、金属支持体１０の第１主面１２のうち水素極６から露出する領域を覆う。 The electrolyte 7 covers the hydrogen electrode 6 and also covers the area of the first main surface 12 of the metal support 10 that is exposed from the hydrogen electrode 6.
　電解質７は、水素極６において生成されたＯ２－を酸素極９側に伝達させる。電解質７は、酸化物イオン伝導性を有する緻密質材料によって構成される。電解質７は、例えば、ＹＳＺ（イットリア安定化ジルコニア、例えば８ＹＳＺ）、ＧＤＣ（ガドリニウムドープセリア）、ＳｃＳＺ（スカンジア安定化ジルコニア）、ＳＤＣ（サマリウム固溶セリア）、ＬＳＧＭ（ランタンガレート）などによって構成することができる。 The electrolyte 7 transfers O 2- generated at the hydrogen electrode 6 to the oxygen electrode 9. The electrolyte 7 is made of a dense material having oxide ion conductivity. The electrolyte 7 can be made of, for example, YSZ (yttria-stabilized zirconia, e.g., 8YSZ), GDC (gadolinium-doped ceria), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), LSGM (lanthanum gallate), or the like.
　電解質７の気孔率は特に制限されないが、例えば０．１％以上７％以下とすることができる。電解質７の厚みは特に制限されないが、例えば１μｍ以上１００μｍ以下とすることができる。 The porosity of the electrolyte 7 is not particularly limited, but can be, for example, 0.1% to 7%. The thickness of the electrolyte 7 is not particularly limited, but can be, for example, 1 μm to 100 μm.
　電解質７の形成方法は特に制限されず、焼成法、スプレーコーティング法、ＰＶＤ法、ＣＶＤ法などを用いることができる。 The method for forming the electrolyte 7 is not particularly limited, and a baking method, a spray coating method, a PVD method, a CVD method, etc. can be used.
　［反応防止層８］
　反応防止層８は、電解質７及び酸素極９の間に配置される。反応防止層８は、電解質７を基準として水素極６の反対側に配置される。反応防止層８は、電解質７の構成元素が酸素極９の構成元素と反応して電気抵抗の大きい層が形成されることを抑制する。 [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 to the hydrogen electrode 6. The reaction prevention layer 8 prevents a layer having a high electrical resistance from being formed due to a reaction between a constituent element of the electrolyte 7 and a constituent element of the oxygen electrode 9.
　反応防止層８は、酸化物イオン伝導性材料によって構成される。反応防止層８は、ＧＤＣ、ＳＤＣなどによって構成することができる。 The reaction prevention layer 8 is made of an oxide ion conductive material. The reaction prevention layer 8 can be made of GDC, SDC, etc.
　反応防止層８の気孔率は特に制限されないが、例えば０．１％以上５０％以下とすることができる。反応防止層８の厚みは特に制限されないが、例えば１μｍ以上５０μｍ以下とすることができる。 The porosity of the reaction prevention layer 8 is not particularly limited, but can be, for example, 0.1% to 50%. The thickness of the reaction prevention layer 8 is not particularly limited, but can be, for example, 1 μm to 50 μm.
　反応防止層８の形成方法は特に制限されず、焼成法、スプレーコーティング法、ＰＶＤ法、ＣＶＤ法などを用いることができる。 The method for forming the reaction prevention layer 8 is not particularly limited, and a baking method, a spray coating method, a PVD method, a CVD method, etc. can be used.
　［酸素極９］
　酸素極９は、電解質７を基準として水素極６の反対側に配置される。本実施形態では、電解質７及び酸素極９の間に反応防止層８が配置されているので、酸素極９は反応防止層８に接続される。電解質７及び酸素極９の間に反応防止層８が配置されない場合、酸素極９は電解質７に接続される。 [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, since the reaction prevention layer 8 is disposed between the electrolyte 7 and the oxygen electrode 9, 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.
　酸素極９は、金属部材２５側の表面（以下、「金属部材側表面」という。）９３を有する。 The oxygen electrode 9 has a surface 93 on the metal member 25 side (hereinafter referred to as the "metal member side surface").
　酸素極９は、下記（５）式の化学反応に従って、水素極６から電解質７を介して伝達されるＯ２－から酸素（Ｏ２）を生成する。 The oxygen electrode 9 produces oxygen (O 2 ) from O 2− transferred from the hydrogen electrode 6 via the electrolyte 7 in accordance with the chemical reaction of the following formula (5).
　・酸素極９：２Ｏ２－→Ｏ２＋４ｅ－・・・（５） Oxygen electrode 9: 2O 2− →O 2 + 4e − (5)
　酸素極９の気孔率は特に制限されないが、例えば２０％以上６０％以下とすることができる。酸素極９の厚みは特に制限されないが、例えば１μｍ以上１００μｍ以下とすることができる。酸素極９の詳細な構成については後述する。 The porosity of the oxygen electrode 9 is not particularly limited, but can be, for example, 20% or more and 60% or less. The thickness of the oxygen electrode 9 is not particularly limited, but can be, for example, 1 μm or more and 100 μm or less. The detailed configuration of the oxygen electrode 9 will be described later.
　酸素極９の形成方法は特に制限されず、焼成法、スプレーコーティング法、ＰＶＤ法、ＣＶＤ法などを用いることができる。 The method for forming the oxygen electrode 9 is not particularly limited, and methods such as baking, spray coating, PVD, and CVD can be used.
　［金属部材２５］
　金属部材２５は、酸素極９と電気的に接続される。本実施形態において、金属部材２５は、導電性接合材２６を介して、酸素極９と電気的に接続されている。ただし、金属部材２５は、酸素極９と直接接触することによって電気的に接続されていてもよい。この場合、金属部材２５は、酸素極９に固定されていなくてもよい。 [Metal member 25]
The metal member 25 is electrically connected to the oxygen electrode 9. In this embodiment, the metal member 25 is electrically connected to the oxygen electrode 9 via a conductive bonding material 26. However, the metal member 25 may be electrically connected to the oxygen electrode 9 by direct contact with the oxygen electrode 9. In this case, the metal member 25 does not need to be fixed to the oxygen electrode 9.
　本実施形態に係る金属部材２５は、集電部材として機能する。金属部材２５は、他の電解セルが備える後述するインターコネクタ３２と電気的に接続される。 The metal member 25 in this embodiment functions as a current collecting member. The metal member 25 is electrically connected to the interconnector 32 (described later) that is provided in the other electrolysis cells.
　金属部材２５は、例えば、フェライト系ステンレスにより構成することができるが、金属部材２５の構成材料は特に限られない。金属部材２５の表面は、導電性のコートによって覆われていてもよい。 The metal member 25 may be made of, for example, ferritic stainless steel, but the material of the metal member 25 is not particularly limited. The surface of the metal member 25 may be covered with a conductive coating.
　金属部材２５の表面の少なくとも一部は、金属部材２５の構成元素が酸化することによって形成された酸化皮膜によって覆われていてもよい。酸化皮膜としては、例えば酸化クロム膜が代表的である。酸化皮膜が存在する場合、酸化皮膜は、金属部材２５の一部を構成するものとする。 At least a portion of the surface of the metal member 25 may be covered with an oxide film formed by oxidation of the constituent elements of the metal member 25. A typical example of the oxide film is a chromium oxide film. When an oxide film is present, the oxide film is considered to constitute a part of the metal member 25.
　また、金属部材２５の表面の少なくとも一部、或いは、金属部材２５の表面を覆う酸化皮膜の少なくとも一部は、耐酸化性コーティング膜によって覆われていてもよい。耐酸化性コーティング膜としては、例えばマンガン-コバルト複合酸化物膜が代表的である。本実施形態において、酸化皮膜は、金属部材２５の一部を構成する。耐酸化性コーティング膜が存在する場合、耐酸化性コーティング膜は、金属部材２５の一部を構成するものとする。 In addition, at least a portion of the surface of the metal member 25, or at least a portion of the oxide film covering the surface of the metal member 25, may be covered with an oxidation-resistant coating film. A typical example of an oxidation-resistant coating film is a manganese-cobalt composite oxide film. In this embodiment, the oxide film constitutes a part of the metal member 25. When an oxidation-resistant coating film is present, the oxidation-resistant coating film constitutes a part of the metal member 25.
　なお、耐酸化性コーティング膜によって金属部材２５の酸化を抑制することはできるが、一般的には、耐酸化性コーティング膜によって金属部材２５の酸化を完全に防止することは困難である。特に、金属部材２５が強酸化性雰囲気に曝されている場合、耐酸化性コーティング膜が形成されていたとしても金属部材２５の酸化を完全には防止できず、金属部材２５の表面には酸化皮膜が成長してしまう。 Although the oxidation-resistant coating film can suppress the oxidation of the metal member 25, it is generally difficult to completely prevent the oxidation of the metal member 25 using the oxidation-resistant coating film. In particular, when the metal member 25 is exposed to a strongly oxidizing atmosphere, the oxidation of the metal member 25 cannot be completely prevented even if an oxidation-resistant coating film is formed, and an oxide film grows on the surface of the metal member 25.
　［流路部材３０］
　流路部材３０は、金属支持体１０の第２主面１３に接合される。流路部材３０は、金属支持体１０との間に流路３０ａを形成する。流路３０ａには、原料ガスが供給される。流路３０ａに供給された原料ガスは、金属支持体１０の各連通孔１１を介して、セル本体部２０の水素極６に供給される。 [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 itself and the metal support 10. A source gas is supplied to the flow path 30a. The source gas supplied to the flow path 30a is supplied to the hydrogen electrode 6 of the cell main body 20 through each communication hole 11 of the metal support 10.
　流路部材３０は、例えば、合金材料によって構成することができる。流路部材３０は、金属支持体１０と同様の材料によって形成されていてもよい。この場合、流路部材３０は、金属支持体１０と実質的に一体であってもよい。 The flow path member 30 can be made of, for example, an alloy material. The flow path member 30 may be made 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.
　流路部材３０は、枠体３１及びインターコネクタ３２を有する。枠体３１は、流路３０ａの側方を取り囲む環状部材である。枠体３１は、金属支持体１０の第２主面１３に接合される。インターコネクタ３２は、外部電源又は他の電解セルを電解セル１と電気的に直列に接続するための板状部材である。インターコネクタ３２は、枠体３１に接合される。 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 body 10. The interconnector 32 is a plate-shaped member for electrically connecting an external power source or another electrolysis cell in series with the electrolysis cell 1. The interconnector 32 is joined to the frame body 31.
　本実施形態では、枠体３１とインターコネクタ３２が別部材となっているが、枠体３１とインターコネクタ３２は一体の部材であってもよい。 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 integrated member.
　（酸素極９の構成）
　図２に示すように、酸素極９は、第１領域９１と第２領域９２とを有する。第１領域９１は、酸素極９のうち金属部材側表面９３から５μｍ以内の領域である。第２領域９２は、酸素極９のうち金属部材側表面９３から５μｍ超の領域である。すなわち、第２領域９２は、酸素極９のうち第１領域９１を除いた領域である。 (Configuration of oxygen electrode 9)
2 , the oxygen electrode 9 has a first region 91 and a second region 92. The first region 91 is a region of the oxygen electrode 9 that is within 5 μm from the metal member side surface 93. The second region 92 is a region of the oxygen electrode 9 that is more than 5 μm from the metal member side surface 93. In other words, the second region 92 is a region of the oxygen electrode 9 excluding the first region 91.
　第１領域９１は、電子伝導性を有する多孔質材料によって構成される。第１領域９１は、例えば、（Ｌａ，Ｓｒ）（Ｃｏ，Ｆｅ）Ｏ３、（Ｌａ，Ｓｒ）ＦｅＯ３、Ｌａ（Ｎｉ，Ｆｅ）Ｏ３、（Ｌａ，Ｓｒ）ＣｏＯ３、（Ｓｍ，Ｓｒ）ＣｏＯ３、Ｌａ（Ｎｉ，Ｆｅ，Ｃｕ）Ｏ３、（Ｌａ，Ｓｒ）ＭｎＯ３のうち１つ以上によって構成することができる。第１領域９１は、酸化物イオン伝導性材料（ＧＤＣなど）を更に含んでいてもよい。 The first region 91 is made of a porous material having electron conductivity. The first region 91 may be made of, for example, one or more of (La,Sr)(Co,Fe) O3 , (La,Sr) FeO3 , La(Ni,Fe) O3 , (La,Sr)CoO3, (Sm,Sr) CoO3 , La(Ni,Fe,Cu) O3 , and (La,Sr) MnO3 . The first region 91 may further include an oxide ion conductive material (such as GDC).
　第２領域９２は、電子伝導性を有する多孔質材料によって構成される。第１領域９１は、例えば、（Ｌａ，Ｓｒ）（Ｃｏ，Ｆｅ）Ｏ３、（Ｌａ，Ｓｒ）ＦｅＯ３、Ｌａ（Ｎｉ，Ｆｅ）Ｏ３、（Ｌａ，Ｓｒ）ＣｏＯ３、（Ｓｍ，Ｓｒ）ＣｏＯ３、Ｌａ（Ｎｉ，Ｆｅ，Ｃｕ）Ｏ３、（Ｌａ，Ｓｒ）ＭｎＯ３のうち１つ以上によって構成することができる。第２領域９２は、酸化物イオン伝導性材料（ＧＤＣなど）を更に含んでいてもよい。 The second region 92 is made of a porous material having electron conductivity. The first region 91 can be made of, for example, one or more of (La,Sr)(Co,Fe) O3 , (La,Sr) FeO3 , La(Ni,Fe) O3 , (La,Sr)CoO3, (Sm,Sr) CoO3 , La(Ni,Fe,Cu) O3 , and (La,Sr) MnO3 . The second region 92 may further include an oxide ion conductive material (such as GDC).
　なお、第１領域９１の組成は、第２領域９２の組成と同じであってもよいし異なっていてもよい。 The composition of the first region 91 may be the same as or different from the composition of the second region 92.
　図２に示すように、第１領域９１は、中央部９１ａ及び外周部９１ｂを有する。 As shown in FIG. 2, the first region 91 has a central portion 91a and an outer peripheral portion 91b.
　中央部９１ａは、平面視における酸素極９の幾何中心ＣＰを含む部位である。本実施形態では、図１に示すように、平面視における酸素極９の平面形状は長方形であり、平面視における中央部９１ａの平面形状も長方形である。平面視において、中央部９１ａは、酸素極９の内部に位置する。中央部９１ａの平面形状は、酸素極９の平面形状と相似である。すなわち、中央部９１ａの外縁を所定の倍率で拡大すると、中央部９１ａの外縁と酸素極９の外縁が合同になる。所定の倍率は特に限られないが、例えば、１．２倍以上４倍以下とすることができる。本実施形態では、所定の倍率は２．０倍であり、中央部９１ａの外縁を２倍に拡大すると酸素極９の外縁と合同になる。 The central portion 91a is a portion including the geometric center CP of the oxygen electrode 9 in plan view. In this embodiment, as shown in FIG. 1, the planar shape of the oxygen electrode 9 in plan view is rectangular, and the planar shape of the central portion 91a in plan view is also rectangular. In plan view, the central portion 91a is located inside the oxygen electrode 9. The planar shape of the central portion 91a is similar to the planar shape of the oxygen electrode 9. In other words, when the outer edge of the central portion 91a is enlarged by a predetermined magnification, the outer edge of the central portion 91a and the outer edge of the oxygen electrode 9 become congruent. The predetermined magnification is not particularly limited, but can be, for example, 1.2 times or more and 4 times or less. In this embodiment, the predetermined magnification is 2.0 times, and when the outer edge of the central portion 91a is enlarged by 2 times, it becomes congruent with the outer edge of the oxygen electrode 9.
　ただし、中央部９１ａが幾何中心ＣＰを含んでいる限り、酸素極９及び中央部９１ａそれぞれの平面形状及びサイズは適宜変更可能である。従って、酸素極９及び中央部９１ａの平面形状は、それぞれ長方形以外の形状（例えば、長方形以外の多角形、楕円形、円形など）であってもよい。また、中央部９１ａの平面形状は、酸素極９の平面形状と異なっていてもよい。平面視における酸素極９の総面積は、平面視における中央部９１ａの面積の１．４４倍以上１６倍以下とすることができる。 However, as long as the central portion 91a includes the geometric center CP, the planar shape and size of each of the oxygen electrode 9 and the central portion 91a can be changed as appropriate. Therefore, the planar shapes of the oxygen electrode 9 and the central portion 91a may each be a shape other than a rectangle (for example, a polygon other than a rectangle, an ellipse, a circle, etc.). The planar shape of the central portion 91a may also be different from the planar shape of the oxygen electrode 9. The total area of the oxygen electrodes 9 in a planar view can be 1.44 to 16 times the area of the central portion 91a in a planar view.
　外周部９１ｂは、平面視において中央部９１ａを取り囲む部位である。外周部９１ｂは、平面視において環状に形成される。外周部９１ｂの平面形状は、酸素極９及び中央部９１ａそれぞれの平面形状に応じて適宜変更可能である。 The outer peripheral portion 91b is a portion that surrounds the central portion 91a in a plan view. The outer peripheral portion 91b is formed in a ring shape in a plan view. The planar shape of the outer peripheral portion 91b can be changed as appropriate according to the planar shapes of the oxygen electrode 9 and the central portion 91a.
　ここで、中央部９１ａの気孔率は、外周部９１ｂの気孔率より小さい。これによって、金属部材２５において酸化皮膜が顕著に成長してしまうことを抑制することができる。具体的には、次の通りである。酸素極９では、第２領域９２のうち、第１領域９１の中央部９１ａと接触する中央部９２ａ（図２参照）に熱ごもりしやすい。そのため、中央部９２ａでは、温度上昇に起因する電流集中に伴って、多量の酸素が生成される。しかしながら、中央部９１ａの気孔率が外周部９１ｂの気孔率より小さいため、中央部９２ａで生成された酸素は、中央部９１ａではなく外周部９１ｂに向かって流れやすい。従って、中央部９２ａで生成された多量の酸素が中央部９１ａから放出されることを抑制できるため、金属部材２５のうち中央部９１ａと接触する部分が強酸化性雰囲気に曝されることを抑制できる。その結果、金属部材２５のうち中央部９１ａと接触する部分における酸化皮膜の顕著な成長に起因する電解セル１の性能低下を抑制できる。 Here, the porosity of the central portion 91a is smaller than that of the outer peripheral portion 91b. This can prevent the oxide film from growing significantly on the metal member 25. Specifically, this is as follows. In the oxygen electrode 9, heat is likely to accumulate in the central portion 92a (see FIG. 2) of the second region 92, which is in contact with the central portion 91a of the first region 91. Therefore, a large amount of oxygen is generated in the central portion 92a due to current concentration caused by a rise in temperature. However, since the porosity of the central portion 91a is smaller than that of the outer peripheral portion 91b, the oxygen generated in the central portion 92a is likely to flow toward the outer peripheral portion 91b rather than the central portion 91a. Therefore, it is possible to prevent a large amount of oxygen generated in the central portion 92a from being released from the central portion 91a, and therefore it is possible to prevent the portion of the metal member 25 in contact with the central portion 91a from being exposed to a strong oxidizing atmosphere. As a result, it is possible to suppress the deterioration of the performance of the electrolysis cell 1 caused by the significant growth of an oxide film on the portion of the metal member 25 that contacts the central portion 91a.
　第２領域９２の気孔率は、中央部９１ａの気孔率より大きいことが好ましい。これによって、第２領域９２の中央部９２ａで生成された酸素を、外周部９１ｂに向かってより流れやすくすることができる。従って、金属部材２５のうち中央部９１ａと接触する部分における酸化皮膜の成長をより抑制できる。 The porosity of the second region 92 is preferably greater than the porosity of the central portion 91a. This allows oxygen generated in the central portion 92a of the second region 92 to flow more easily toward the outer periphery 91b. This makes it possible to further suppress the growth of an oxide film in the portion of the metal member 25 that comes into contact with the central portion 91a.
　中央部９１ａの気孔率は特に限られないが、例えば、２０％以上４０％以下とすることができる。外周部９１ｂの気孔率は特に限られないが、例えば、２５％以上４５％以下とすることができる。 The porosity of the central portion 91a is not particularly limited, but can be, for example, 20% to 40%. The porosity of the outer peripheral portion 91b is not particularly limited, but can be, for example, 25% to 45%.
　第２領域９２の気孔率は特に限られないが、例えば、２０％以上４５％以下とすることができる。 The porosity of the second region 92 is not particularly limited, but can be, for example, 20% or more and 45% or less.
　第１領域９１のうち中央部９１ａの気孔率は、次の手法により算出される。まず、Ｚ軸方向に沿った中央部９１ａの断面を露出させる。次に、ＳＥＭ装置（日本電子株式会社製、ＦＥ－ＳＥＭ　ＪＳＭ－７９００Ｆ）を用いて、中央部９１ａの断面の反射電子像を１００００倍で取得する。次に、ＭＥＤＩＡＣＹＢＥＲＮＥＴＩＣＳ社製の画像解析ソフトＩｍａｇｅ－Ｐｒｏを用いて、反射電子像において黒色で表示された部分（気孔に相当）を特定する。そして、中央部９１ａの反射電子像の全面積で気孔の合計面積を割ることによって、中央部９１ａの気孔率が算出される。 The porosity of the central portion 91a of the first region 91 is calculated by the following method. First, a cross section of the central portion 91a along the Z-axis direction is exposed. Next, a backscattered electron image of the cross section of the central portion 91a is obtained at 10,000x magnification using an SEM device (FE-SEM JSM-7900F, manufactured by JEOL Ltd.). Next, the areas displayed in black in the backscattered electron image (corresponding to pores) are identified using image analysis software Image-Pro, manufactured by MEDIACYBERNETICS. The porosity of the central portion 91a is then calculated by dividing the total area of the pores by the total area of the backscattered electron images of the central portion 91a.
　第１領域９１のうち外周部９１ｂの気孔率は、中央部９１ａの気孔率と同様、外周部９１ｂの反射電子像の全面積で気孔の合計面積を割ることによって算出される。 The porosity of the outer peripheral portion 91b of the first region 91 is calculated by dividing the total area of the pores by the total area of the backscattered electron image of the outer peripheral portion 91b, similar to the porosity of the central portion 91a.
　第２領域９２の気孔率は、中央部９１ａの気孔率と同様、第２領域９２の反射電子像の全面積で気孔の合計面積を割ることによって算出される。 The porosity of the second region 92, like the porosity of the central portion 91a, is calculated by dividing the total area of the pores by the total area of the backscattered electron image of the second region 92.
　酸素極９は、第２領域用の構成材料を用いて反応防止層８上に第２領域９２を形成した後、第１領域９１の中央部用の構成材料を用いて第２領域９２上に中央部９１ａを形成し、さらに、第１領域９１の外周部用の構成材料を用いて中央部９１ａを取り囲むように外周部９１ｂを形成することによって作製される。 The oxygen electrode 9 is produced by forming a second region 92 on the reaction prevention layer 8 using the constituent material for the second region, forming a central portion 91a on the second region 92 using the constituent material for the central portion of the first region 91, and then forming a peripheral portion 91b surrounding the central portion 91a using the constituent material for the peripheral portion of the first region 91.
　第１領域９１の中央部９１ａ、第１領域９１の外周部９１ｂ、及び第２領域９２それぞれの気孔率は、造孔材の添加量、原料粉体の粒径、材料組成及び材料種によって調整することができるが、造孔材の添加量による調整は電極性能への影響が少ないため好ましい。 The porosity of each of the central portion 91a of the first region 91, the outer peripheral portion 91b of the first region 91, and the second region 92 can be adjusted by the amount of pore-forming material added, the particle size of the raw material powder, the material composition, and the material type, but adjustment by the amount of pore-forming material added is preferred because it has little effect on electrode performance.
　（実施形態の変形例）
　以上、本発明の実施形態について説明したが、本発明はこれらに限定されるものではなく、本発明の趣旨を逸脱しない限りにおいて種々の変更が可能である。 (Modification of the embodiment)
Although the embodiments of the present invention have 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.
　［変形例１］
　上記実施形態において、金属部材２５は、集電部材として機能することとしたが、これに限られない。金属部材２５は、空気極９と電気的に接続されていればよい。例えば、金属部材２５は、他の電解セルが備えるインターコネクタ３２であってもよい。 [Modification 1]
In the above embodiment, the metal member 25 functions as a current collecting member, but is not limited thereto. The metal member 25 may be electrically connected to the air electrode 9. For example, the metal member 25 may be an interconnector 32 provided in another electrolysis cell.
　［変形例２］
　上記実施形態では、電解セルの一例として、メタルサポート型の電解セル１について説明したが、本発明に係る電解セルは、金属支持体１０を備えていない平板型であってもよい。 [Modification 2]
In the above embodiment, the metal support type electrolytic cell 1 has been described as an example of an electrolytic cell. However, the electrolytic cell according to the present invention may be a flat plate type that does not include a metal support 10.
　以下において本発明に係る電気化学セルの実施例について説明するが、本発明は以下に説明する実施例に限定されるものではない。 　Below, we will explain examples of the electrochemical cell according to the present invention, but the present invention is not limited to the examples described below.
　（比較例１，２）
　比較例１，２に係る電解セルを次の通り作製した。 (Comparative Examples 1 and 2)
Electrolytic cells according to Comparative Examples 1 and 2 were prepared as follows.
　まず、複数の連通孔が形成されたＦｅ－Ｃｒ－Ｍｎ系合金鋼製の金属支持体を準備した。 First, a metal support made of Fe-Cr-Mn alloy steel with multiple communicating holes was prepared.
　次に、ＧＤＣ粉末、ＮｉＯ粉末、ブチラール樹脂、造孔材としてのポリメタクリル酸メチル製ビーズ、可塑剤、分散剤、及び溶剤を混合することによって水素極層用スラリーを調製した。そして、ドクターブレード法により水素極層用スラリーを金属支持体の第１主面上に印刷することによって水素極層の成形体を形成した。 Next, a slurry for the hydrogen electrode layer was prepared by mixing GDC powder, NiO powder, butyral resin, polymethyl methacrylate beads as a pore-forming material, a plasticizer, a dispersant, and a solvent. The slurry for the hydrogen electrode layer was then printed on the first main surface of the metal support by the doctor blade method to form a hydrogen electrode layer compact.
　次に、ＹＳＺ粉末、ブチラール樹脂、可塑剤、分散剤、及び溶剤を混合することによって電解質層用スラリーを調製した。そして、ドクターブレード法により水素極層の成形体を覆うように電解質用スラリーを印刷することによって電解質層の成形体を形成した。 Next, a slurry for the electrolyte layer was prepared by mixing YSZ powder, butyral resin, plasticizer, dispersant, and solvent. The electrolyte slurry was then printed using a doctor blade method to cover the green body of the hydrogen electrode layer, forming a green body for the electrolyte layer.
　次に、ＧＤＣ粉末、ポリビニルアルコール、及び溶媒を混合することによって反応防止層用スラリーを調製した。そして、ドクターブレード法により電解質層の成形体上に反応防止層用スラリーを印刷することによって反応防止層の成形体を形成した。 Next, a slurry for the reaction prevention layer was prepared by mixing GDC powder, polyvinyl alcohol, and a solvent. The slurry for the reaction prevention layer was then printed on the electrolyte layer compact by the doctor blade method to form a reaction prevention layer compact.
　次に、金属支持体上に順次配置された水素極層、電解質層、及び反応防止層それぞれの成形体を大気中で焼成（１０５０℃、１時間）することによって、水素極層、電解質層、及び反応防止層を形成した。 Next, the molded bodies of the hydrogen electrode layer, electrolyte layer, and reaction prevention layer arranged in sequence on the metal support were fired in air (1050°C, 1 hour) to form the hydrogen electrode layer, electrolyte layer, and reaction prevention layer.
　次に、（Ｌａ，Ｓｒ）（Ｃｏ，Ｆｅ）Ｏ３粉末、ポリビニルアルコール、溶媒及び造孔材を混合することによって酸素極層用スラリーを調製した。この際、造孔材の添加量を調整することによって、酸素極全体の気孔率を表１に示すように比較例ごとに変更した。そして、ドクターブレード法により反応防止層上に酸素極層用スラリーを印刷することによって酸素極層の成形体を形成した。 Next, a slurry for the oxygen electrode layer was prepared by mixing (La, Sr) (Co, Fe) O3 powder, polyvinyl alcohol, a solvent, and a pore former. At this time, the amount of the pore former added was adjusted to change the porosity of the entire oxygen electrode for each comparative example, as shown in Table 1. Then, the slurry for the oxygen electrode layer was printed on the reaction prevention layer by the doctor blade method to form a compact for the oxygen electrode layer.
　次に、酸素極層の成形体を大気中で焼成（１０００℃、１時間）することによって酸素極を形成した。 Then, the oxygen electrode layer compact was sintered in air (1000°C, 1 hour) to form the oxygen electrode.
　最後に、酸素極層上に金属部材及び電流板を順次取り付け、金属支持体に電流線を取り付けた。以上により、比較例１，２に係る電解セルが完成した。 Finally, a metal member and a current plate were attached in sequence onto the oxygen electrode layer, and a current wire was attached to the metal support. This completed the electrolysis cells for Comparative Examples 1 and 2.
　（実施例１～７）
　酸素極層を二層構造にしたこと以外は上記比較例１，２と同じ工程にて実施例１～７に係る電解セルを作製した。 (Examples 1 to 7)
Electrolytic cells according to Examples 1 to 7 were fabricated in the same manner as in Comparative Examples 1 and 2, except that the oxygen electrode layer had a two-layer structure.
　具体的には、（Ｌａ，Ｓｒ）（Ｃｏ，Ｆｅ）Ｏ３粉末、ポリビニルアルコール、溶媒、及び造孔材を混合することによって第２領域用スラリーを調製した。この際、造孔材の添加量を調整することによって、酸素極のうち第２領域の気孔率を表１に示すように実施例ごとに変更した。そして、ドクターブレード法により反応防止層上に第２領域用スラリーを印刷することによって酸素極のうち第２領域の成形体を形成した。 Specifically, a slurry for the second region was prepared by mixing (La, Sr) (Co, Fe) O3 powder, polyvinyl alcohol, a solvent, and a pore former. At this time, the amount of the pore former added was adjusted to change the porosity of the second region of the oxygen electrode for each example, as shown in Table 1. Then, the slurry for the second region was printed on the reaction prevention layer by a doctor blade method to form a compact for the second region of the oxygen electrode.
　次に、（Ｌａ，Ｓｒ）（Ｃｏ，Ｆｅ）Ｏ３粉末、ポリビニルアルコール、溶媒、及び造孔材を混合することによって第１領域の中央部用スラリーを調製した。この際、造孔材の添加量を調整することによって、酸素極のうち第１領域の中央部の気孔率を表１に示すように実施例ごとに変更した。そして、ドクターブレード法により第２領域の成形体の中央部上に第１領域の中央部用スラリーを印刷することによって酸素極のうち第１領域の中央部の成形体を形成した。 Next, a slurry for the center of the first region was prepared by mixing (La,Sr)(Co,Fe) O3 powder, polyvinyl alcohol, a solvent, and a pore former. At this time, the amount of the pore former added was adjusted to change the porosity of the center of the first region of the oxygen electrode for each example, as shown in Table 1. Then, the slurry for the center of the first region was printed on the center of the compact for the second region by a doctor blade method, thereby forming a compact for the center of the first region of the oxygen electrode.
　次に、（Ｌａ，Ｓｒ）（Ｃｏ，Ｆｅ）Ｏ３粉末、ポリビニルアルコール、溶媒、及び造孔材を混合することによって第１領域の外周部用スラリーを調製した。この際、造孔材の添加量を調整することによって、酸素極のうち第１領域の外周部の気孔率を表１に示すように実施例ごとに変更した。そして、ドクターブレード法により第１領域の成形体を取り囲むように第１領域の外周部用スラリーを印刷することによって酸素極のうち第１領域の外周部の成形体を形成した。 Next, a slurry for the outer periphery of the first region was prepared by mixing (La, Sr) (Co, Fe) O 3 powder, polyvinyl alcohol, a solvent, and a pore former. At this time, the amount of the pore former added was adjusted to change the porosity of the outer periphery of the first region of the oxygen electrode for each example, as shown in Table 1. Then, the slurry for the outer periphery of the first region was printed by a doctor blade method so as to surround the compact of the first region, thereby forming a compact of the outer periphery of the first region of the oxygen electrode.
　次に、第１領域及び第２領域の成形体を大気中で焼成（１０００℃、１時間）することによって酸素極を形成した。 Next, the molded bodies of the first and second regions were sintered in air (1000°C, 1 hour) to form an oxygen electrode.
　（耐久評価）
　まず、実施例１～７及び比較例１，２の電解セルを７００℃まで昇温した状態で、酸素極層に空気を供給しながら水素極層に水素を供給することによって、水素極層が含有するＮｉＯをＮｉに還元した。 (Durability evaluation)
First, in the electrolytic cells of Examples 1 to 7 and Comparative Examples 1 and 2, the temperature was raised to 700° C., and hydrogen was supplied to the hydrogen electrode layer while air was supplied to the oxygen electrode layer, thereby reducing NiO contained in the hydrogen electrode layer to Ni.
　次に、水素極層に水蒸気及び水素の混合ガス（混合比９０：１０）を供給しながら酸素極層に酸素及び窒素の混合ガス（混合比２１：７９）を供給し、水素極層面積当たりの電流密度が０．５Ａ／ｃｍ２で一定になるように電流を流して電解したときのセル電圧（以下、「初期セル電圧」という。）を測定した。 Next, a mixed gas of water vapor and hydrogen (mixing ratio 90:10) was supplied to the hydrogen electrode layer while a mixed gas of oxygen and nitrogen (mixing ratio 21:79) was supplied to the oxygen electrode layer, and a current was passed so that the current density per hydrogen electrode layer area was constant at 0.5 A/ cm2 to perform electrolysis, and the cell voltage (hereinafter referred to as "initial cell voltage") was measured.
　続いて、水素極層及び酸素極層それぞれに上記混合ガスを供給しながら電流密度を０．５Ａ／ｃｍ２に固定した状態で１０００時間保持した後のセル電圧（以下、「耐久後セル電圧」という。）を測定した。 Next, the cell voltage after 1000 hours of holding in a state where the current density was fixed at 0.5 A/cm 2 while supplying the mixed gas to each of the hydrogen electrode layer and the oxygen electrode layer (hereinafter referred to as “cell voltage after durability test”) was measured.
　そして、下記（６）式を用いて性能低下率を算出した。 Then, the performance degradation rate was calculated using the following formula (6).
　性能低下率（％）＝１００×（耐久後セル電圧－初期セル電圧）／初期セル電圧…（６）
　表１では、性能低下率が４％未満の場合を「◎」と評価し、４％以上７％未満の場合を「〇」と評価し、７％以上の場合を「×」と評価した。 Performance degradation rate (%) = 100 × (cell voltage after durability test - initial cell voltage) / initial cell voltage... (6)
In Table 1, a performance degradation rate of less than 4% was evaluated as "A", a performance degradation rate of 4% or more and less than 7% was evaluated as "O", and a performance degradation rate of 7% or more was evaluated as "X".
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示すように、酸素極層において第１領域の中央部の気孔率を第１領域の外周部の気孔率より小さくした実施例１～７では、比較例１，２に比べて性能低下率を低くすることができた。このような結果が得られたのは、第２領域で生成された酸素を第１領域の外周部に流すことによって、金属部材における酸化皮膜の顕著な成長を抑制できたためである。 As shown in Table 1, in Examples 1 to 7, in which the porosity of the center of the first region in the oxygen electrode layer was made smaller than the porosity of the outer periphery of the first region, the performance degradation rate was lower than in Comparative Examples 1 and 2. This result was obtained because the significant growth of the oxide film on the metal member was suppressed by flowing the oxygen generated in the second region to the outer periphery of the first region.
　また、酸素極層において第２領域の気孔率を第１領域の中央部の気孔率より大きくした実施例６，７では、実施例１～５に比べて性能低下率を低くすることができた。このような結果が得られたのは、第２領域で生成された酸素を第１領域の外周部により流れやすくできたためである。 In addition, in Examples 6 and 7, in which the porosity of the second region in the oxygen electrode layer was made greater than the porosity of the central part of the first region, the rate of performance degradation was reduced compared to Examples 1 to 5. This result was achieved because the oxygen generated in the second region was able to flow more easily to the outer periphery of the first region.
１　　　電解セル
１０　　金属支持体
１１　　連通孔
１２　　第１主面
１３　　第２主面
２０　　セル本体部
６　　　水素極
７　　　電解質
８　　　反応防止層
９　　　酸素極
９１　　第１領域
９１ａ　　中央部
９１ｂ　　外周部
９２　　第２領域
９２ａ　　中央部
３０　　流路部材
３０ａ　流路 Reference Signs List 1 Electrolysis cell 10 Metal support 11 Through hole 12 First main surface 13 Second main surface 20 Cell body 6 Hydrogen electrode 7 Electrolyte 8 Reaction prevention layer 9 Oxygen electrode 91 First region 91a Central portion 91b Outer peripheral portion 92 Second region 92a Central portion 30 Flow path member 30a Flow path

Claims (2)

  1. 　水素極と、酸素極と、前記水素極及び前記酸素極の間に配置される電解質とを有するセル本体部と、
    　前記酸素極と電気的に接続される金属部材と、
    を備え、
    　前記酸素極は、金属部材側表面から５μｍ以内の第１領域と、前記金属部材側表面から５μｍ超の第２領域とを有し、
    　前記第１領域は、中央部と、前記中央部を取り囲む外周部とを含み、
    　前記中央部の気孔率は、前記外周部の気孔率より小さい、
    電解セル。     a cell body having a hydrogen electrode, an oxygen electrode, and an electrolyte disposed between the hydrogen electrode and the oxygen electrode;
    a metal member electrically connected to the oxygen electrode;
    Equipped with
    the oxygen electrode has a first region within 5 μm from the metal member side surface and a second region more than 5 μm from the metal member side surface,
    The first region includes a central portion and an outer periphery surrounding the central portion,
    The porosity of the central portion is smaller than the porosity of the peripheral portion.
    Electrolysis cell.
  2. 　前記第２領域の気孔率は、前記中央部の気孔率より大きい、
    電解セル。     The porosity of the second region is greater than the porosity of the central portion.
    Electrolysis cell.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0757737A (en) * 1993-08-19 1995-03-03 Mitsubishi Heavy Ind Ltd Flame splaying electrode material of solid electrolyte type electrolytic cell
WO2018198352A1 (en) * 2017-04-28 2018-11-01 株式会社 東芝 Solid oxide electrochemical cell and production method therefor
WO2022045141A1 (en) * 2020-08-24 2022-03-03 京セラ株式会社 Cell, cell stack device, module, and module accommodating device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0757737A (en) * 1993-08-19 1995-03-03 Mitsubishi Heavy Ind Ltd Flame splaying electrode material of solid electrolyte type electrolytic cell
WO2018198352A1 (en) * 2017-04-28 2018-11-01 株式会社 東芝 Solid oxide electrochemical cell and production method therefor
WO2022045141A1 (en) * 2020-08-24 2022-03-03 京セラ株式会社 Cell, cell stack device, module, and module accommodating device

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