Hydrogen electrode-solid electrolyte layer composite body, proton conducting cell structure, fuel cell, steam electrolysis cell, and method for producing hydrogen electrode-solid electrolyte layer composite body

Abstract

A hydrogen electrode-solid electrolyte layer composite body according to the present disclosure comprises: a hydrogen electrode which has pores; and a solid electrolyte layer which is in contact with the hydrogen electrode. The hydrogen electrode and the solid electrolyte layer each contain a metal oxide. The metal oxide has a perovskite structure and is represented by formula (1): AxB1-yMyO3-δ. (In the formula, the element A is at least one element that is selected from the group consisting of Ba, Ca, and Sr; the element B is at least one element that is selected from the group consisting of Ce and Zr; the element M is at least one element that is selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In, and Sc; δ represents the amount of oxygen deficiency; and 0.95≤x≤1 and 0<y≤0.5 are satisfied.) The hydrogen electrode has a nickel component in the pores, and the pores have a first average diameter or a second average diameter. The first average diameter is smaller than the second average diameter.

Description

Hydrogen electrode-solid electrolyte layer composite, proton conducting cell structure, fuel cell, steam electrolysis cell, and method for manufacturing hydrogen electrode-solid electrolyte layer composite

[0001] The present disclosure relates to a hydrogen electrode-solid electrolyte layer composite, a proton-conducting cell structure, a fuel cell, a steam electrolysis cell, and a hydrogen electrode-solid electrolyte layer composite. This application claims priority to Japanese Application No. 2023-101713, filed on June 21, 2023, and incorporates the entire contents of said Japanese application by reference.

[0002] Patent Document 1 discloses a method for manufacturing a hydrogen electrode-solid electrolyte layer composite that enables the formation of a proton-conducting cell structure with excellent current efficiency. The manufacturing method described in Patent Document 1 suppresses the diffusion of nickel into the solid electrolyte layer. As a result, steam electrolysis cells and fuel cells that use the hydrogen electrode-solid electrolyte layer composite obtained by the manufacturing method described in Patent Document 1 exhibit high current efficiency.

[0003] International Publication No. 2019 / 107194

[0004] One aspect of the present disclosure is a hydrogen electrode-solid electrolyte layer composite including a hydrogen electrode having pores and a solid electrolyte layer in contact with the hydrogen electrode, wherein the hydrogen electrode and the solid electrolyte layer each contain a metal oxide, and the metal oxide has a perovskite structure and is represented by the following formula (1): ｘ B １－ｙ M ｙ O ３－δ(1) (wherein the formula, element A is at least one selected from the group consisting of Ba, Ca, and Sr, element B is at least one selected from the group consisting of Ce and Zr, element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In, and Sc, and δ is the amount of oxygen deficiency, satisfying 0.95≦x≦1, 0<y≦0.5). The hydrogen electrode has a nickel component in the pores, and the pores have a first average diameter or a second average diameter. In a cross-sectional view parallel to the thickness direction of the hydrogen electrode, the first average diameter is the average value of the outer diameters of the 10 largest pores, selected from 100 pores of which 70% or more of the outer periphery is visible in a region from the contact surface between the hydrogen electrode and the solid electrolyte layer to a depth of 50 μm. The second average diameter is the average value of the outer diameters of the 10 largest pores, selected from 20 pores of which 70% or more of the outer periphery is visible in a region from the surface of the hydrogen electrode opposite the contact surface to a depth of 200 μm. The first average diameter is smaller than the second average diameter.

[0005] Another aspect of the present disclosure relates to a proton-conducting cell structure including the hydrogen electrode-solid electrolyte layer composite of the present disclosure and a porous oxygen electrode in contact with the solid electrolyte layer, the solid electrolyte layer being interposed between the oxygen electrode and the hydrogen electrode, and the oxygen electrode being a compound having a perovskite structure.

[0006] Yet another aspect of the present disclosure relates to a fuel cell comprising the proton-conducting cell structure of the present disclosure.

[0007] Yet another aspect of the present disclosure relates to a steam electrolysis cell comprising the proton-conducting cell structure of the present disclosure.

[0008] Yet another aspect of the present disclosure relates to a method for producing a hydrogen electrode-solid electrolyte layer composite. The method for producing a hydrogen electrode-solid electrolyte layer composite includes a hydrogen electrode having pores and a solid electrolyte layer in contact with the hydrogen electrode, and includes the following steps: a first step of preparing a first paste sheet that serves as a precursor of the solid electrolyte layer, and a second paste sheet and a third paste sheet that serve as precursors of the hydrogen electrode; a second step of stacking the first paste sheet, the second paste sheet, and the third paste sheet in the order of the first paste sheet, the second paste sheet, and the third paste sheet to obtain a paste sheet laminate; a third step of heat-treating the paste sheet laminate to obtain a sintered body; a fourth step of impregnating the sintered body with a nickel compound solution to obtain a nickel-impregnated sintered body; and a fifth step of heat-treating the nickel-impregnated sintered body to obtain the hydrogen electrode-solid electrolyte layer composite. The first paste sheet contains a metal oxide, and the metal oxide has a perovskite structure and is represented by the following formula (1): A ｘ B １－ｙ M ｙ O ３－δ (1) (wherein element A is at least one selected from the group consisting of Ba, Ca, and Sr, element B is at least one selected from the group consisting of Ce and Zr, element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In, and Sc, and δ is the amount of oxygen deficiency, satisfying 0.95≦x≦1, 0<y≦0.5). The second paste sheet includes the metal oxide and a first pore-forming material having a first median diameter. The third paste sheet includes the metal oxide and a second pore-forming material having a second median diameter. The first median diameter is smaller than the second median diameter.

[0009] FIG. 1 is a scanning electron microscope cross-sectional photograph showing the hydrogen electrode-solid electrolyte layer composite according to this embodiment. FIG. 2 is an enlarged photograph of the vicinity of the contact surface in FIG. 1. FIG. 3 is an enlarged photograph of the vicinity of the hydrogen electrode surface in FIG. 1. FIG. 4 is an explanatory diagram of porosity, coating rate, and impregnation rate. FIG. 5 is a flow chart of a method for manufacturing the hydrogen electrode-solid electrolyte layer composite. FIG. 6 is a schematic diagram of a proton-conducting cell structure including the hydrogen electrode-solid electrolyte layer composite according to this embodiment. FIG. 7 is a schematic diagram of a fuel cell including the proton-conducting cell structure according to this embodiment.

[0010] [Problem to be Solved by the Present Disclosure] The performance of steam electrolysis cells and fuel cells is improving day by day, and therefore there is a demand for further improvements in the current efficiency and power density of proton-conducting cell structures.

[0011] An object of the present disclosure is to provide a hydrogen electrode-solid electrolyte layer composite for forming a proton-conducting cell structure having excellent current efficiency and power density. Another object of the present disclosure is to provide a proton-conducting cell structure including the hydrogen electrode-solid electrolyte layer composite. A further object of the present disclosure is to provide a fuel cell and a steam electrolysis cell including the proton-conducting cell structure. Additionally, an object of the present disclosure is to provide a method for producing the hydrogen electrode-solid electrolyte layer composite.

[0012] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a hydrogen electrode-solid electrolyte layer composite for forming a proton-conducting cell structure having excellent current efficiency and power density. Furthermore, according to the present disclosure, it is possible to provide a proton-conducting cell structure including the hydrogen electrode-solid electrolyte layer composite. Furthermore, according to the present disclosure, it is possible to provide a fuel cell and a steam electrolysis cell including the proton-conducting cell structure. In addition, according to the present disclosure, it is possible to provide a method for manufacturing the hydrogen electrode-solid electrolyte layer composite.

[0013] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. (1) A hydrogen electrode-solid electrolyte layer composite according to one embodiment of the present disclosure is a hydrogen electrode-solid electrolyte layer composite including a hydrogen electrode having pores and a solid electrolyte layer in contact with the hydrogen electrode, wherein the hydrogen electrode and the solid electrolyte layer each contain a metal oxide, and the metal oxide has a perovskite structure and is represented by the following formula (1): A ｘ B １－ｙ M ｙ O ３－δ (1) (wherein element A is at least one selected from the group consisting of Ba, Ca, and Sr, element B is at least one selected from the group consisting of Ce and Zr, element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In, and Sc, and δ is the amount of oxygen deficiency, satisfying 0.95≦x≦1 and 0<y≦0.5). The hydrogen electrode has a nickel component in the pores, and the pores have a first average diameter or a second average diameter. In a cross-sectional view parallel to the thickness direction of the hydrogen electrode, the first average diameter is the average value of the outer diameters of the 10 largest pores, selected from 100 pores whose outer peripheries are visible to a depth of 50 μm from the contact surface between the hydrogen electrode and the solid electrolyte layer, and the second average diameter is the average value of the outer diameters of the 10 largest pores, selected from 20 pores whose outer peripheries are visible to a depth of 200 μm from the surface of the hydrogen electrode on the opposite side from the contact surface, and the first average diameter is smaller than the second average diameter.

[0014] According to the hydrogen electrode-solid electrolyte layer composite described in (1) above, a proton conducting cell structure having excellent current efficiency and power density can be formed.

[0015] (2) In the hydrogen electrode-solid electrolyte layer composite of (1) above, the ratio of the second average diameter to the first average diameter (second average diameter / first average diameter) may be 2.0 or more and 10 or less.

[0016] (3) In the hydrogen electrode-solid electrolyte layer composite of (1) or (2) above, the first average diameter may be 10 μm or more and 40 μm or less, and the second average diameter may be 30 μm or more and 200 μm or less.

[0017] (4) In the hydrogen electrode-solid electrolyte layer composite of any one of (1) to (3) above, the hydrogen electrode may include a first area including the contact surface, a second area including the surface, and an interface between the first area and the second area, and the first area may have a porosity of 60% or more and 90% or less, and the second area may have a porosity of 40% or more and 90% or less.

[0018] (5) In the hydrogen electrode-solid electrolyte layer composite of any one of (1) to (4) above, the hydrogen electrode may include a first area including the contact surface, a second area including the surface, and an interface between the first area and the second area, and the average film thickness from the contact surface to the interface may be 50 μm or more and 300 μm or less, and the average film thickness from the surface to the interface may be 200 μm or more and 1000 μm or less.

[0019] (6) In the hydrogen electrode-solid electrolyte layer composite of any one of (1) to (5) above, a coating rate of the nickel component in the pores in the first area may be 20% or more and 75% or less.

[0020] (7) In the hydrogen electrode-solid electrolyte layer composite of any one of (1) to (6) above, the impregnation rate of the nickel component in the pores in the first area may be 15% or more and less than 45%.

[0021] (8) In the hydrogen electrode-solid electrolyte layer composite of any one of (1) to (7) above, the element A may be Ba, the element B may be Zr, and the element M may be Y or Yb.

[0022] According to the hydrogen electrode-solid electrolyte layer composite of the above items (2) to (8), a proton conducting cell structure having superior current efficiency and power density can be formed.

[0023] (9) A proton-conducting cell structure according to another embodiment of the present disclosure includes the hydrogen electrode-solid electrolyte layer composite according to any one of (1) to (8) above, and a porous oxygen electrode in contact with the solid electrolyte layer, wherein the solid electrolyte layer is interposed between the oxygen electrode and the hydrogen electrode, and the oxygen electrode is a compound having a perovskite structure.

[0024] The proton conductive cell structure (9) above has excellent current efficiency and power density.

[0025] (10) In the proton conductive cell structure of (9) above, the oxygen electrode may be lanthanum strontium cobalt ferrite or lanthanum strontium cobaltite.

[0026] The proton conducting cell structure (10) above has better current efficiency and power density.

[0027] (11) A fuel cell according to another embodiment of the present disclosure includes the proton-conducting cell structure described in (9) or (10) above.

[0028] (12) A steam electrolysis cell according to another embodiment of the present disclosure includes the proton-conducting cell structure described in (9) or (10) above.

[0029] The fuel cell of (11) above and the steam electrolysis cell of (12) above are provided with a proton-conducting cell structure having excellent current efficiency and power density.

[0030] (13) Another embodiment of a method for producing a hydrogen electrode-solid electrolyte layer composite according to the present disclosure includes a hydrogen electrode-solid electrolyte layer composite including a hydrogen electrode having pores and a solid electrolyte layer in contact with the hydrogen electrode, the method comprising the steps of: a first step of preparing a first paste sheet serving as a precursor of the solid electrolyte layer, and a second paste sheet and a third paste sheet serving as precursors of the hydrogen electrode; a second step of stacking the first paste sheet, the second paste sheet, and the third paste sheet in the order of the first paste sheet, the second paste sheet, and the third paste sheet to obtain a paste sheet laminate; a third step of heat-treating the paste sheet laminate to obtain a sintered body; a fourth step of impregnating the sintered body with a nickel compound solution to obtain a nickel-impregnated sintered body; and a fifth step of heat-treating the nickel-impregnated sintered body to obtain a hydrogen electrode-solid electrolyte layer composite. The first paste sheet contains a metal oxide, and the metal oxide has a perovskite structure and is represented by the following formula (1): A ｘ B １－ｙ M ｙ O ３－δ (1) (wherein element A is at least one selected from the group consisting of Ba, Ca, and Sr, element B is at least one selected from the group consisting of Ce and Zr, element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In, and Sc, and δ is the amount of oxygen deficiency, satisfying 0.95≦x≦1, 0<y≦0.5). The second paste sheet includes the metal oxide and a first pore-forming material having a first median diameter, and the third paste sheet includes the metal oxide and a second pore-forming material having a second median diameter. The first median diameter is smaller than the second median diameter.

[0031] The manufacturing method (13) above can manufacture a hydrogen electrode-solid electrolyte layer composite that can form a proton-conducting cell structure having excellent current efficiency and power density.

[0032] (14) In the manufacturing method of (13) above, the third step may be a step of heat-treating the paste sheet laminate at 400°C or more and 1000°C or less to remove at least a portion of the first pore-forming material and the second pore-forming material, and then heat-treating the paste sheet laminate at 1400°C or more and 1650°C or less to obtain a sintered body.

[0033] (15) In the manufacturing method of (13) or (14), the fifth step may be a step of heat-treating the nickel-impregnated sintered body at 200°C or higher and 600°C or lower to fix the nickel component in the pores of the hydrogen electrode, thereby obtaining a hydrogen electrode-solid electrolyte layer composite.

[0034] (16) In any of the manufacturing methods (13) to (15) above, the ratio of the second median diameter to the first median diameter (second median diameter / first median diameter) may be 2.5 or more and 10 or less.

[0035] (17) In the manufacturing method of (16) above, the first median diameter may be 15 μm or more and 50 μm or less, and the second median diameter may be 30 μm or more and 200 μm or less.

[0036] According to any one of the manufacturing methods (14) to (17) above, it is possible to manufacture a hydrogen electrode-solid electrolyte layer composite that enables the formation of a proton-conducting cell structure having superior current efficiency and power density.

[0037] [Details of the embodiments of the present disclosure] The embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the present invention is not limited to these examples. The scope of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0038] [Hydrogen Electrode-Solid Electrolyte Layer Composite] Figure 1 is a cross-sectional scanning electron microscope photograph (hereinafter sometimes simply referred to as a "cross-sectional SEM photograph") showing a hydrogen electrode-solid electrolyte layer composite according to this embodiment. The hydrogen electrode-solid electrolyte layer composite 1 shown in Figure 1 comprises a hydrogen electrode 10 having pores 13, and a solid electrolyte layer 20. The hydrogen electrode 10 is porous. The solid electrolyte layer 20 is dense. The hydrogen electrode 10 and the solid electrolyte layer 20 are adjacent to each other and in contact at a contact surface 41. The hydrogen electrode 10 has a first area 11 having the contact surface 41. The hydrogen electrode 10 includes a second area 12 having a hydrogen electrode surface 42, which is the surface of the hydrogen electrode. The first area and the second area are adjacent to each other and in contact at a boundary surface 40.

[0039] Fig. 2 is an enlarged photograph of the vicinity of the contact surface 41 surrounded by dotted line A in Fig. 1. Fig. 3 is an enlarged photograph of the vicinity of the hydrogen electrode surface 42 surrounded by dotted line B in Fig. 1. As shown in Figs. 2 and 3, the hydrogen electrode 10 has nickel components 14 in the pores 13. Here, the nickel components 14 refer to those determined to be nickel by SEM-EDX.

[0040] The hydrogen electrode-solid electrolyte layer composite 1 is configured so that the outer diameter of the pores 13 present in the first area 11 is smaller than the outer diameter of the pores 13 present in the second area 12. That is, in the hydrogen electrode-solid electrolyte layer composite 1, the first average diameter of the pores 13 present in the first area 11 is smaller than the second average diameter of the pores 13 present in the second area 12. This enables the hydrogen electrode-solid electrolyte layer composite 1 to form a proton conducting cell structure having excellent current efficiency and power density.

[0041] Here, the first average diameter is the average value of the outer diameters of the 10 largest pores 13 selected from 100 pores 13 whose outer peripheries are visible at 70% or more in a region of the hydrogen electrode 10 from the contact surface 41 to a depth of 50 μm in a cross section parallel to the thickness direction of the hydrogen electrode 10. Here, "pores 13 whose outer peripheries are visible at 70% or more" refer to pores 13 whose outer peripheries are visible at 70% or more in a cross-sectional SEM photograph. Specifically, the first average diameter is obtained by the steps (A-1) to (A-5) described below. The outer diameter of the pores 13 is the outermost diameter of the pores 13. The "outermost diameter" refers to the diameter of the circle if the cross-sectional shape of the pores 13 is a perfect circle, and refers to the longest distance between two points on the outer periphery if the cross-sectional shape is not a perfect circle. (A-1) A cross-sectional SEM photograph of the hydrogen electrode-solid electrolyte layer composite 1 is obtained, the cross-sectional SEM photograph including 100 or more pores 13 in which 70% or more of the periphery is visible in a region from the contact surface 41 to a depth of 50 μm. (A-2) 100 pores 13 are selected from the obtained cross-sectional SEM photograph. (A-3) The outer diameters of the selected 100 pores 13 are measured. (A-4) Of the measured outer diameters, the 10 largest outer diameters are extracted. (A-5) The average value of the extracted 10 outer diameters is obtained as a first average diameter.

[0042] The second average diameter is the average of the outer diameters of the 10 largest pores 13, selected from a region extending from the hydrogen electrode surface 42 to a depth of 200 μm in a cross section parallel to the thickness direction of the hydrogen electrode 10, for which 70% or more of the periphery is visible. Specifically, the second average diameter is obtained by the following steps (B-1) to (B-5): (B-1) A cross-sectional SEM photograph of the hydrogen electrode-solid electrolyte layer composite 1 is obtained, the cross-sectional SEM photograph including 20 or more pores 13 for which 70% or more of the periphery is visible in a region extending from the hydrogen electrode surface 42 to a depth of 200 μm. (B-2) Twenty pores 13 are selected from the obtained cross-sectional SEM photograph. (B-3) The outer diameters of the selected 20 pores 13 are measured. (B-4) The 10 largest outer diameters are extracted from the measured outer diameters. (B-5) The average value of the extracted 10 outer diameters is obtained as a second average diameter.

[0043] The ratio of the second average diameter to the first average diameter (second average diameter / first average diameter) can be 2.0 or more and 10 or less, particularly 2.0 or more and 8 or less. In the above ratio, the first average diameter can be 10 μm or more and 40 μm or less, particularly 10 μm or more and 35 μm or less. In the above ratio, the second average diameter can be 30 μm or more and 200 μm or less, particularly 30 μm or more and 125 μm or less. This makes it possible for the hydrogen electrode-solid electrolyte layer composite 1 to form a proton-conducting cell structure having better current efficiency and power density.

[0044] In FIG. 1 , the average thickness of the first area 11 from the contact surface 41 to the boundary surface 40 is a first average thickness 51. The first average thickness 51 can be 50 μm or more and 300 μm or less. The average thickness of the second area 12 from the hydrogen electrode surface 42 to the boundary surface 40 is a second average thickness 52. The second average thickness 52 can be 200 μm or more and 1000 μm or less. The average thickness 50 of the hydrogen electrode 10 can be 250 μm or more and 1300 μm or less. The average thickness 53 of the solid electrolyte layer 20 can be 20 μm or more and 40 μm or less. The average thickness is the average value of thicknesses measured at three locations within the same field of view.

[0045] (Metal Oxide Having a Perovskite Structure) The hydrogen electrode 10 and the solid electrolyte layer 20 each contain a metal oxide. The metal oxide has a perovskite structure and is represented by the following formula (1): ｘ B １－ｙ M ｙ O ３－δ (1) The A site is occupied by element A, and the B site is occupied by element B (not representing boron). A portion of the B site is substituted with element M in order to ensure high proton conductivity.

[0046] The ratio x of element A to the sum of element B and element M can be 0.95≦x≦1, particularly 0.98≦x≦1. This ensures high proton conductivity and ion transport number. Furthermore, by not exceeding 1, precipitation of element A is suppressed, and corrosion of the metal oxide due to the action of moisture is suppressed. The ratio y of element M can be 0<y≦0.5, particularly 0.1<y≦0.3. This ensures proton conductivity. The amount of oxygen vacancy δ is determined according to the ratio y of element M. For example, the amount of oxygen vacancy δ is 0≦δ≦0.15. The ratio of each element in the metal oxide can be determined, for example, by wavelength dispersive X-ray analysis using an electron probe microanalyzer.

[0047] The element A is at least one element selected from the group consisting of Ba (barium), Ca (calcium), and Sr (strontium). The element A can contain Ba. This can provide excellent proton conductivity. The proportion of Ba in the element A can be 50 atomic % or more, particularly 80 atomic % or more. The element A can be composed of Ba only.

[0048] The element B is at least one element selected from the group consisting of Ce (cerium) and Zr (zirconium). The element B may contain Zr, which improves the durability of the hydrogen electrode 10 and the solid electrolyte layer 20. The ratio of Zr in the element B may be 50 atomic % or more, particularly 80 atomic % or more. The element B may consist of only Zr.

[0049] The element M is at least one element selected from the group consisting of Y (yttrium), Yb (ytterbium), Er (erbium), Ho (holmium), Tm (thulium), Gd (gadolinium), In (indium), and Sc (scandium). The element M is a dopant that generates oxygen vacancies, allowing the metal oxide having a perovskite structure to exhibit proton conductivity.

[0050] A specific example of a metal oxide having a perovskite structure is yttrium-doped barium zirconate [Ba ｘ Zr １－ｙ Y ｙO ３－δ ] (hereinafter, sometimes simply referred to as "BZY"), ytterbium-doped barium zirconate [Ba ｘ Zr １－ｙ Yb ｙ O ３－δ ] (hereinafter, sometimes simply referred to as "BZYb"), yttrium-doped barium cerate [Ba ｘ Ce １－ｙ Y ｙ O ３－δ ], yttrium-doped barium zirconate / barium cerate mixed oxide [Ba ｘ Zr １－ｙ－ｚ Ce ｚ Y ｙ O ３－δ The hydrogen electrode 10 and the solid electrolyte layer 20 may contain at least one selected from BZY and BZYb.

[0051] (Porosity, Coating Rate, and Impregnation Rate) Figure 4 is an explanatory diagram of the porosity, coating rate, and impregnation rate. The upper side of Figure 4 shows a schematic diagram illustrating the results of energy dispersive X-ray analysis (hereinafter, sometimes simply referred to as "EDX") of the hydrogen electrode-solid electrolyte layer composite 1. The lower side of Figure 4 shows, from top to bottom, a schematic diagram visually illustrating the formula for calculating the porosity, a schematic diagram visually illustrating the formula for calculating the coating rate, and a schematic diagram visually illustrating the formula for calculating the impregnation rate.

[0052] To determine the porosity, coating rate, and impregnation rate, a mapping image is obtained by mapping Ba and Ni in the hydrogen electrode-solid electrolyte layer composite 1 using EDX. Next, an analysis image is obtained by analyzing the pores 13 and nickel components 14 in the mapping image. The analysis of the pores 13 and nickel components 14 in the mapping image was performed using a general program created using Python (registered trademark). The porosity, coating rate, and impregnation rate are determined based on the acquired analysis image.

[0053] The porosity is a value indicating the proportion of the pores 13 in the target area of ​​the hydrogen electrode 10. The porosity is calculated from the cross-sectional area of ​​the pores 13 and the cross-sectional area of ​​the target area, which are obtained from the above-mentioned analytical image. The porosity is calculated using the following formula (2). When expressing the porosity as a percentage, the value obtained from the following formula (2) is multiplied by 100. Porosity = Cross-sectional area of ​​pores ÷ Cross-sectional area of ​​target area (2)

[0054] The coating rate is a value indicating the proportion of the area of ​​the inner surface of the pore 13 that is covered with the nickel component 14. The coating rate is calculated from the cross-sectional length of the nickel component 14 and the cross-sectional length of the pore 13, which are obtained from the above-mentioned analysis image. Here, the cross-sectional length of the pore 13 is the outer periphery length of the cross-section of the pore 13. Furthermore, the cross-sectional length of the nickel component 14 is the total periphery length surrounding the area of ​​the nickel component 14 within the cross-section of the pore 13. The formula for calculating the coating rate is expressed by the following formula (3). Note that when expressed as a percentage, the value obtained by the following formula (3) is multiplied by 100. Coating rate = Cross-sectional length of the nickel component ÷ 2 ÷ Cross-sectional length of the pore (3)

[0055] The impregnation rate is a value indicating the proportion of the nickel component 14 in the pores 13. The impregnation rate is calculated from the cross-sectional area of ​​the nickel component 14 and the cross-sectional area of ​​the pores, which are obtained from the above-mentioned analytical image. The impregnation rate is calculated using the following formula (4). When expressing the impregnation rate as a percentage, the value obtained from the following formula (4) is multiplied by 100. Impregnation rate = Cross-sectional area of ​​nickel component ÷ Cross-sectional area of ​​pores (4)

[0056] In the hydrogen electrode-solid electrolyte layer composite 1, the porosity of the first area 11 can be 60% or more and 90% or less, particularly 60% or more and 80% or less. The porosity of the second area 12 can be 40% or more and 90% or less, particularly 40% or more and 80% or less. This allows the hydrogen electrode-solid electrolyte layer composite 1 to form a proton-conducting cell structure with better current efficiency and power density.

[0057] In the hydrogen electrode-solid electrolyte layer composite 1, the coating rate of the nickel component 14 in the hydrogen electrode 10 can be 10% or more and 90% or less, particularly 20% or more and 75% or less. The impregnation rate of the hydrogen electrode 10 can be 3% or more and 60% or less, particularly 15% or more and 40% or less. The coating rate of the first area 11 is preferably 20% or more and 75% or less. The impregnation rate of the nickel component in the first area 11 is preferably 15% or more and less than 45%. This ensures that the nickel component 14 functions as a catalytic component in the hydrogen electrode 10. Furthermore, the electrical conductivity of the hydrogen electrode 10 is ensured. Therefore, the hydrogen electrode-solid electrolyte layer composite 1 can form a proton-conducting cell structure with superior current efficiency and power density.

[0058] [Method for manufacturing hydrogen electrode-solid electrolyte layer composite] Fig. 5 is a flow diagram of a method for manufacturing the hydrogen electrode-solid electrolyte layer composite 1. As shown in Fig. 5, the method for manufacturing the hydrogen electrode-solid electrolyte layer composite 1 includes five steps, a first step S1 to a fifth step S5.

[0059] (First Step) The first step S1 is a step of preparing a first paste sheet that serves as a precursor for the solid electrolyte layer 20, and a second paste sheet and a third paste sheet that serve as precursors for the hydrogen electrode 10. The first paste sheet contains a metal oxide but does not contain a pore-forming material. The metal oxide has a perovskite structure and is represented by the above formula (1). The second paste sheet contains a metal oxide and a first pore-forming material. The metal oxide has a perovskite structure and is represented by the above formula (1). The third paste sheet contains a metal oxide and a second pore-forming material. The metal oxide has a perovskite structure and is represented by the above formula (1). It is preferable that the metal oxides contained in the first paste sheet, the second paste sheet, and the third paste sheet are the same.

[0060] The second paste sheet is a precursor of the first area 11. The third paste sheet is a precursor of the second area 12. The first pore-forming material contained in the second paste sheet has a first median diameter. The second pore-forming material contained in the third paste sheet has a second median diameter. The first median diameter is smaller than the second median diameter. This makes it possible to produce a hydrogen electrode-solid electrolyte layer composite 1 having a first average diameter smaller than the second average diameter.

[0061] The ratio of the second median diameter to the first median diameter (second median diameter / first median diameter) can be 2.5 or more and 10 or less. In this ratio, the first median diameter can be 15 μm or more and 50 μm or less, particularly 20 μm or more and 45 μm or less. In this ratio, the second median diameter can be 30 μm or more and 200 μm or less, particularly 35 μm or more and 160 μm or less. This makes it possible to produce a hydrogen electrode-solid electrolyte layer composite 1 having the above-mentioned ratio of the second average diameter to the first average diameter, and the above-mentioned first average diameter and second average diameter.

[0062] Each of the above-mentioned paste sheets may contain a binder, if necessary. Examples of the binder include, but are not limited to, known materials used in the production of ceramic materials, such as polymer binders and waxes. Examples of the polymer binder include butyral resins, cellulose derivatives, vinyl acetate resins, and acrylic resins. Examples of the butyral resin include polyvinyl butyral. Examples of the cellulose derivative include ethyl cellulose and cellulose ether. The concept of vinyl acetate resins also includes saponified vinyl acetate resins such as propyl alcohol. Examples of the wax include paraffin wax.

[0063] Each of the paste sheets described above may contain a dispersion medium as needed. Examples of the dispersion medium include, but are not limited to, water and organic solvents. Examples of the organic solvent include hydrocarbons such as toluene; alcohols such as ethanol and isopropanol; and carbitols such as butyl carbitol acetate.

[0064] Each of the above paste sheets may contain various additives such as surfactants, deflocculants, and plasticizers, if necessary.

[0065] (Second Step) The second step S2 is a step of obtaining a paste sheet laminate by stacking the first paste sheet, the second paste sheet, and the third paste sheet in the order of the first paste sheet, the second paste sheet, and the third paste sheet. This makes it possible to produce a hydrogen electrode-solid electrolyte layer composite 1 having a layer structure in which the solid electrolyte 20, the first area 11, and the second area 12 are arranged in that order. The stacking of the paste sheets may be performed by screen printing or using green sheets, and is not particularly limited. The paste sheet laminate obtained in the second step S2 of this embodiment is obtained by stacking green sheets.

[0066] (Third Step) The third step S3 is a step of heat treating the paste sheet laminate obtained in the second step S2 to obtain a sintered body. In the third step S3 of this embodiment, the paste sheet laminate in which the green sheets are laminated is heated at 60°C to 80°C and 20 kgf / cm ２ Over 40 kgf / cm ２The paste sheet laminate is treated under a pressure of 400°C or higher and 1000°C or lower. This removes at least a portion of the binder, the first pore-forming material contained in the second paste sheet, and the second pore-forming material contained in the third paste sheet. Next, the paste sheet laminate after the heat treatment is further heated at 1400°C or higher and 1650°C or lower to obtain a sintered body. The heat treatment may also be performed under conditions of 1500°C or higher and 1650°C or lower. This produces a hydrogen electrode-solid electrolyte layer composite 1 that can form a proton-conducting cell structure with superior current efficiency and power density. The heat treatment for removing the binder, first pore-forming material, and second pore-forming material can be omitted. In this case, the paste sheet laminate is heated at 1400°C or higher and 1650°C or lower to obtain a sintered body.

[0067] (Fourth Step) In the fourth step S4, the sintered body obtained in the third step S3 is impregnated with a nickel compound solution to obtain a nickel-impregnated sintered body. The nickel compound solution may be, for example, a solution containing nickel powder, a dispersant, and α-terpineol. The particle size of the nickel powder is, for example, 1 μm or less. The respective contents of the nickel powder, dispersant, and α-terpineol are, for example, 82 mass%, 2 mass%, and 16 mass%, respectively. In the fourth step S4, the nickel compound solution is impregnated into the pores of the sintered body. The impregnation process with the nickel compound solution may be appropriately selected depending on the type and state of the nickel compound solution, and is not particularly limited. For example, when the impregnation ability of the nickel compound solution is low, reduced pressure impregnation or pressurized impregnation is selected. When the impregnation ability of the nickel compound solution is high, an impregnation method such as dripping the nickel compound solution onto the sintered body or immersing the sintered body in the nickel compound solution is selected. In the fourth step S4 of this embodiment, a nickel-impregnated sintered body is obtained by dripping a nano-Ni slurry, which is a nickel compound solution, onto the surface of the sintered body that will become the hydrogen electrode 10 (hereinafter, this may be simply referred to as "drop impregnation").

[0068] The nickel compound solution penetrates the pores of the sintered body of the second paste sheet via the pores of the sintered body of the third paste sheet. As described above, the first median diameter of the first pore-forming material contained in the second paste sheet is smaller than the second median diameter of the second pore-forming material contained in the third paste sheet. Therefore, the pores of the sintered body of the third paste sheet are larger than the pores of the sintered body of the second paste sheet. The nickel compound solution easily passes through the sintered body of the third paste sheet, which has larger pores. This promotes the impregnation of the nickel compound solution into the pores of the sintered body of the second paste sheet. As a result, the application rate and impregnation rate in the first area 11 of the hydrogen electrode-solid electrolyte layer composite 1 produced by the manufacturing method of this embodiment are ensured. Therefore, the manufacturing method of this embodiment produces a hydrogen electrode-solid electrolyte layer composite 1 capable of forming a proton-conducting cell structure with sufficient current efficiency and power density.

[0069] (Fifth Step) In the fifth step S5, the nickel-impregnated sintered body obtained in the fourth step S4 is heat-treated to obtain a hydrogen electrode-solid electrolyte layer composite 1. In the fifth step S5, the nickel-impregnated sintered body is heat-treated at 200°C or higher and 600°C or lower. This heat treatment coats the inner surfaces of the pores 13 of the hydrogen electrode-solid electrolyte layer composite 1 with nickel components 14. Furthermore, by heat-treating the nickel-impregnated sintered body at 200°C or higher and 600°C or lower, diffusion of nickel into the solid electrolyte layer 20 can be suppressed. The heat treatment may also be performed under conditions of 300°C or higher and 500°C or lower. As a result, according to the manufacturing method of this embodiment, a hydrogen electrode-solid electrolyte layer composite 1 is manufactured that can form a proton-conducting cell structure with superior current efficiency and power density.

[0070] The impregnation treatment in the fourth step S4 and the heat treatment in the fifth step S5 may be repeated multiple times, thereby improving the coating rate and impregnation rate of the hydrogen electrode 10, particularly the first area 11.

[0071] [Proton Conductive Cell Structure] Figure 6 is a schematic diagram of a proton conductive cell structure 2 including a hydrogen electrode-solid electrolyte layer composite 1. The proton conductive cell structure 2 includes the hydrogen electrode-solid electrolyte layer composite 1 and a porous oxygen electrode 30 in contact with the solid electrolyte layer 20. The proton conductive cell structure 2 has excellent current efficiency and output density because it includes the hydrogen electrode-solid electrolyte layer composite 1. The proton conductive cell structure 2 has a configuration in which the solid electrolyte layer 20 is interposed between the oxygen electrode 30 and the hydrogen electrode 10. The average thickness of the oxygen electrode 30 is not particularly limited, but may be approximately 5 µm to 40 µm.

[0072] The oxygen electrode 30 is a compound having a perovskite structure. Examples of the compound include compounds having a perovskite structure containing lanthanum (such as ferrite, manganite, and / or cobaltite). The compound having a perovskite structure containing lanthanum may contain strontium. Specifically, lanthanum strontium cobalt ferrite (LSCF: La １－ｘ Sr ｘ Fe １－ｙ Co ｙ O ３－δ , 0<x<1, 0<y<1), lanthanum strontium manganite (LSM: La １－ｘ Sr ｘ MnO ３－δ , 0<x<1), lanthanum strontium cobaltite (LSC: La １－ｘ Sr ｘ CoO ３－δ , 0<x<1). The oxygen electrode 30 of the proton conductive cell structure 2 may be LSCF or LSC. This allows the proton conductive cell structure 2 to have better current efficiency and power density. Here, δ represents the amount of oxygen vacancy.

[0073] [Method for Manufacturing Proton Conductive Cell Structure] The proton conductive cell structure 2 can be manufactured by laminating a fourth paste sheet, which serves as a precursor of the oxygen electrode 30, on the surface of a sintered body that will become the solid electrolyte layer 20 of the hydrogen electrode-solid electrolyte layer composite 1, and then performing a heat treatment at 800°C to 1100°C. More specifically, in a first step S1 shown in FIG. 5 , a fourth paste sheet is further prepared. In a third step S3, a fourth paste sheet is laminated on the surface of the solid electrolyte layer 20 of the first sintered body that includes a sintered body of the first paste sheet, the second paste sheet, and the third paste sheet. By heat treating the first sintered body on which the fourth paste sheet is laminated, a second sintered body that includes a sintered body of the fourth paste sheet is obtained. By treating the second sintered body in a fourth step S4 and a fifth step S5, the proton conductive cell structure 2 is obtained.

[0074] The fourth paste sheet includes the compound having a perovskite structure containing lanthanum. The fourth paste sheet may include a catalyst such as Pt to promote the reaction between protons and oxide ions. The fourth paste sheet may also include the binder, dispersion medium, and / or additives as needed.

[0075] [Fuel Cell] FIG. 7 is a schematic diagram of a fuel cell 3 including a proton-conducting cell structure 2. The fuel cell 3 according to this embodiment may have the same configuration as a conventional fuel cell except for the proton-conducting cell structure 2. Specifically, the fuel cell 3 may include a first separator 62 having an oxidant flow path 64. For example, an oxidant is supplied from the oxidant flow path 64 to the oxygen electrode 30 through a first current collector 60 located near the oxygen electrode 30 of the proton-conducting cell structure 2. The fuel cell 3 may further include a second separator 63 having a fuel flow path 65. A fuel is supplied from the fuel flow path 65 to the hydrogen electrode 10 through a second current collector 61 located near the hydrogen electrode 10 of the proton-conducting cell structure 2. The fuel cell 3 according to this embodiment has excellent current efficiency and power density because it includes the proton-conducting cell structure 2. Apart from the use of the proton-conducting cell structure 2, the fuel cell can be manufactured by a known method.

[0076] [Steam Electrolysis Cell] The steam electrolysis cell according to this embodiment may have the same configuration as a conventional steam electrolysis cell, except that it includes the proton-conducting cell structure 2. For example, it may have the same structure as the fuel cell shown in FIG. 7. The steam electrolysis cell according to this embodiment includes the proton-conducting cell structure 2, and therefore has excellent current efficiency and power density. The steam electrolysis cell can be manufactured by a known method, except that it uses the proton-conducting cell structure 2.

[0077] [Other Embodiments] The hydrogen electrode-solid electrolyte layer composite 1 and the proton conducting cell structure 2 have a laminated shape, but are not limited to this. For example, they may have a cylindrical shape rolled up with the hydrogen electrode on the inside so as to have a hollow center.

[0078] The proton conductive cell structure 2 can also be applied to a gas decomposition device. Examples of gas decomposition devices include those having the same configuration as conventional gas decomposition devices except for including the proton conductive cell structure 2. The gas decomposition device can be manufactured by a known method except for using the proton conductive cell structure 2.

[0079] Next, the present disclosure will be described in more detail based on examples, but the present disclosure is not limited to only the examples.

[0080] [BaZr ０．８ Y ０．２ O ２．９ Preparation of Powder] Barium carbonate, zirconium oxide, and yttrium oxide were mixed in a ball mill for 24 hours in a molar ratio such that the Ba ratio was 1.0 and the Y ratio was 0.2. The mixture was then calcined at 1000°C for 10 hours. The calcined mixture was then processed in a ball mill for 10 hours, uniaxially molded, and then calcined in an air atmosphere at 1300°C for 10 hours. The calcined sample was pulverized in a mortar and then processed in a ball mill for 10 hours. The obtained powder was then again uniaxially molded, calcined at 1300°C for 10 hours, and then processed in a ball mill for 10 hours to obtain BaZr ０．８ Y ０．２ O ２．９A powder (hereinafter also referred to as BZY powder) was obtained.

[0081] [Preparation of First Paste Sheet (Precursor of Solid Electrolyte Layer)] 100 g of BZY powder and a dispersion medium (a mixed dispersion medium of toluene:ethanol = 4:6 (parts by weight)) were mixed in a ball mill to obtain a mixture. 15 g of PVB (polyvinyl butyral) as a binder and 4.5 g of dibutyl phthalate as a plasticizer were added to the obtained mixture and further mixed to obtain a slurry mixture with a viscosity of 12 Pa·s. The obtained slurry mixture was applied to a silicone-treated polyester film substrate in the atmosphere using a doctor blade method to a thickness of 100 μm, and then left in a thermostatic chamber at 80 °C for 30 minutes to remove the solvent. The first paste sheet was then peeled off from the substrate to obtain a 40 μm thick green sheet.

[0082] [Preparation of Second Paste Sheet (Precursor of the First Area of ​​the Hydrogen Electrode)] 50 g of BZY powder, a pore-forming material (described below), and a dispersion medium (a toluene:ethanol = 4:6 (parts by weight) mixture) were mixed in a ball mill to obtain a mixture. 15 g of PVB (polyvinyl butyral) as a binder and 4.5 g of dibutyl phthalate as a plasticizer were added to the resulting mixture and further mixed to obtain a slurry mixture with a viscosity of 10 Pa·s. The resulting slurry mixture was applied to a silicone-treated polyester film substrate in the atmosphere using a doctor blade method to a thickness of 500 μm, and then left in a thermostatic chamber at 80 °C for 30 minutes to remove the solvent. The second paste sheet was then peeled off from the substrate to prepare a 180 μm thick green sheet.

[0083] [Preparation of Third Paste Sheet (Precursor of Second Area of ​​Hydrogen Electrode)] 50 g of BZY powder, a pore-forming material described below, and a dispersion medium (a toluene:ethanol = 4:6 (parts by weight) mixed dispersion medium) were mixed in a ball mill to obtain a mixture. 15 g of PVB (polyvinyl butyral) as a binder and 4.5 g of dibutyl phthalate as a plasticizer were added to the resulting mixture and further mixed to obtain a slurry mixture with a viscosity of 8 Pa·s. The resulting slurry mixture was applied to a silicone-treated polyester film substrate in the atmosphere using a doctor blade method to a thickness of 500 μm, and then left in a thermostatic chamber at 80 °C for 30 minutes to remove the solvent. The third paste sheet was then peeled off from the substrate to prepare a 180 μm thick green sheet.

[0084] [Pore-forming material] In preparing the second paste sheet and the third paste sheet described above, spherical carbons having the following three types of median diameters were used as pore-forming materials: First spherical carbon: median diameter 20 μm (manufactured by Nippon Carbon Co., Ltd., "ICB-2020") Second spherical carbon: median diameter 40 μm (manufactured by Nippon Carbon Co., Ltd., "ICB-15020") Third spherical carbon: median diameter 100 μm (manufactured by Sekisui Plastics Co., Ltd., "Techpolymer MBX-100") Fourth spherical carbon: median diameter 150 μm (manufactured by Nippon Carbon Co., Ltd., "ICB-15020")

[0085] Table 1 shows the types and amounts of the pore-forming materials in the second paste sheet and the third paste sheet used in the production of each sample of the proton-conducting cell structure.

[0086]

[0087] [Obtaining a sintered body] A paste sheet laminate was produced by stacking the first paste sheet, the second paste sheet, and the third paste sheet in this order. The obtained paste sheet laminate was subjected to a sintering treatment at 70°C and 30 kgf / cm ２ The paste sheet laminate after the pressure bonding process was heat treated at 800°C for 1 hour in an air atmosphere to remove the binder and the pore-forming material. The paste sheet laminate after the removal process was heat treated at 1500°C for 10 hours in an air atmosphere to obtain a first sintered body.

[0088] LSCF (La) was used as the oxygen electrode material. ０．６ Sr ０．４ Fe ０．８ Co ０．２ O ３－δ An LSCF paste was prepared by mixing 50 g of powder of α-pyrrolidone (α-pyrrolidone), 50 g of butyl carbitol acetate as a dispersion medium, and 10 g of ethyl cellulose as a binder. This LSCF paste was applied to a thickness of 30 μm by screen printing on the surface of the first sintered body that would become the solid electrolyte layer. The LSCF was then sintered by heat treatment at 1000°C for 2 hours, obtaining a second sintered body with an oxygen electrode of 25 μm in thickness.

[0089] [Obtaining a proton-conducting cell structure] (Obtaining a nickel-impregnated sintered body) A nano-Ni slurry containing nano-Ni powder (manufactured by Sigma-Aldrich) with a median diameter of 200 nm was dripped onto the surface of the second sintered body that would become the hydrogen electrode to obtain a nickel-impregnated sintered body. In order to coat the inner surfaces of the pores of the hydrogen electrode with nickel, the nickel-impregnated sintered body was heat-treated at 400°C for 1 hour. The above dripping impregnation and heat treatment were repeated four times to obtain a proton-conducting cell structure (φ16 mm).

[0090] [Measurement of Average Film Thickness, First Average Diameter, Second Average Diameter, Porosity, Coating Rate, and Impregnation Rate] The porosity, coating rate, and impregnation rate were measured for each of the proton conductive cell structures of Samples 1 to 9 and Samples 10 to 12, which were manufactured using the second paste sheet and the third paste sheet shown in Table 1. Cross-sectional SEM photographs of each proton conductive cell structure were taken using a scanning electron microscope ("JSM-7800F" manufactured by JEOL Ltd.). Analysis of the pores and nickel components of each proton conductive cell structure by EDX was performed using an energy dispersive X-ray analyzer ("X-MAX80 EDS System" manufactured by OXFORD) attached to the scanning electron microscope.

[0091] The average film thickness, outer diameter of the pores, cross-sectional area of ​​the pores, cross-sectional area of ​​the target area, cross-sectional length of the nickel component, cross-sectional length of the pores, cross-sectional area of ​​the nickel component, and cross-sectional area of ​​the pores were obtained using a cross-sectional SEM photograph analysis program developed in Python. The first average diameter was obtained by the above-mentioned procedures (A-1) to (A-5). The second average diameter was obtained by the above-mentioned procedures (B-1) to (B-5). The porosity, coating rate, and impregnation rate were obtained as percentages (%) by multiplying the values ​​obtained by the above-mentioned formulas (2) to (4) by 100.

[0092] [Output Characteristics and Electrolytic Evaluation of Proton Conductive Cell Structures] The output characteristics of the proton conductive cell structures of Samples 1 to 9 and 10 to 12 were measured by open circuit voltage (OCV) and maximum power density. Electrolytic evaluation of each proton conductive cell structure was performed by measuring current density and current efficiency. To measure the OCV, maximum power density, current density, and current efficiency, platinum meshes with welded lead wires were attached to the surfaces of the oxygen and hydrogen electrodes of each proton conductive cell structure using platinum electrode paste. The other ends of the lead wires were connected to a measuring instrument so that the current and voltage values ​​between the lead wires could be measured.

[0093] (OCV Measurement) The operating temperature was set to 600°C, and hydrogen was flowed as fuel gas at 1 L / min to the hydrogen electrode of each proton conductive cell structure, and synthetic air (a mixture of only oxygen and nitrogen) with a dew point of -40°C or lower was flowed to the air electrode at 1 L / min, and the OCV was measured.

[0094] (Measurement of maximum power density) The operating temperature was set to 600°C, and 100 cm of hydrogen was supplied as fuel gas to the hydrogen electrode of each proton-conducting cell structure. ３ / min, and 200 cm of air was supplied to the air electrode. ３ The air and hydrogen were humidified to a dew point of 25°C. The voltage was measured while changing the current density, and the maximum power density (mW / cm) was calculated from the current density and voltage. ２ ) was sought.

[0095] (Measurement of Current Density) A voltage of 1.3 V was applied to each proton conductive cell structure, and the current was measured as a current density (A / cm ２) was measured.

[0096] (Measurement of current efficiency) The air electrode was humidified at 80°C, and steam electrolysis evaluation was performed at an operating temperature of 600°C. The voltage was measured as the current density was gradually increased using an electronic load device. A current-voltage curve was obtained based on the measured voltage, and an approximate equation was calculated. From the approximate equation, the current density (Ifc) at 1.3 V was calculated. Next, the current density was gradually increased using a DC power supply, and the voltage at that time was read to calculate the current density (Iec) at 1.3 V. The current efficiency was calculated from the equation Ifc / Iec×100.

[0097] [Measurement Results] Tables 2 and 3 show various measurement results for each of the proton conductive cell structures of Sample No. 1 to Sample No. 12. The average film thicknesses of the first area and the second area were 150 μm and 300 μm, respectively. In Table 2, the coating rate and content rate indicate the coating rate and content rate of the first area.

[0098]

[0099]

[0100] As shown in Tables 2 and 3, the proton conductive cell structures of Samples 1 to 9 had a maximum power density of 99 mW / cm ２ or more and a current efficiency of 22% or more, whereas the proton conductive cell structures of sample numbers 10 to 12 have a maximum power density of 25 mW / cm ２ In the following cases, the current efficiency was below the measurement limit. The hydrogen electrodes of the proton conductive cell structures of sample numbers 1 to 9 were configured so that the first average diameter of the pores present in the first area was smaller than the second average diameter of the pores present in the second area. On the other hand, the hydrogen electrodes of the proton conductive cell structures of sample numbers 10 to 12 were configured so that the average diameters of the pores present in the first area and the second area were the same. This experimentally demonstrated that proton conductive cell structures having a configuration in which the first average diameter was smaller than the second average diameter had excellent current efficiency and power density.

[0101] Furthermore, from Tables 2 and 3, the proton conductive cell structures of Sample Nos. 1 to 5 have a maximum power density of 302 mW / cm ２ It was experimentally shown that the proton conductive cell structures of sample numbers 1 to 5 had a ratio of the second average diameter to the first average diameter (second average diameter / first average diameter) of 2.1 to 7.6, a porosity of the first area of ​​62% to 79%, a porosity of the second area of ​​44% to 80%, a coating rate of 21% to 75%, and an impregnation rate of 15% to 38%. This shows that proton conductive cell structures having a second average diameter / first average diameter ratio of 2.0 to 8, a porosity of the first area of ​​60% to 80%, a porosity of the second area of ​​40% to 80%, a coating rate of 20% to 75%, and an impregnation rate of 15% to 40% have better current efficiency and power density.

[0102] REFERENCE SIGNS LIST 1 Hydrogen electrode-solid electrolyte layer composite 2 Proton conducting cell structure 3 Fuel cell 10 Hydrogen electrode 11 First area 12 Second area 13 Pore 14 Nickel component 20 Solid electrolyte layer 30 Oxygen electrode 40 Boundary surface 41 Contact surface 42 Hydrogen electrode surface 50 Average film thickness of hydrogen electrode 51 First average film thickness 52 Second average film thickness 53 Average film thickness of solid electrolyte layer 60 First current collector 61 Second current collector 62 First separator 63 Second separator 64 Oxidant flow path 65 Fuel flow path

Claims

1. A hydrogen electrode-solid electrolyte layer composite comprising a hydrogen electrode having pores and a solid electrolyte layer in contact with the hydrogen electrode, The hydrogen electrode and the solid electrolyte layer each contain a metal oxide. The aforementioned metal oxide has a perovskite-type structure and is defined by the following formula (1): A ｘ B １－ｙ M ｙ O ３－δ (1) (In the formula, element A is at least one selected from the group consisting of Ba, Ca, and Sr, Element B is at least one selected from the group consisting of Ce and Zr. Element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In, and Sc. δ is the oxygen deficiency, satisfying 0.95 ≤ x ≤ 1 and 0 < y ≤ 0.

5. It is represented as, The hydrogen electrode has a nickel component in the pores, The aforementioned pores have a first average diameter or a second average diameter, In a cross-sectional view parallel to the thickness direction of the hydrogen electrode, the first average diameter is the average of the outer diameters of the 10 largest pores selected from 100 pores where 70% or more of the outer circumference is visible in the region from the contact surface between the hydrogen electrode and the solid electrolyte layer to a depth of 50 μm, and the second average diameter is the average of the outer diameters of the 10 largest pores selected from 20 pores where 70% or more of the outer circumference is visible in the region from the surface of the hydrogen electrode opposite the contact surface to a depth of 200 μm. The first average diameter is smaller than the second average diameter. Hydrogen electrode-solid electrolyte layer composite.

2. The hydrogen electrode-solid electrolyte layer composite according to claim 1, wherein the ratio of the second average diameter to the first average diameter (second average diameter / first average diameter) is 2.0 or more and 10 or less.

3. The first average diameter is 10 μm or more and 40 μm or less. The aforementioned second average diameter is 30 μm or more and 200 μm or less. The hydrogen electrode-solid electrolyte layer composite according to claim 1.

4. The hydrogen electrode includes a first area including the contact surface, a second area including the surface, and an interface between the first area and the second area. In the aforementioned first area, the porosity is 60% or more and 90% or less. In the aforementioned second area, the porosity is 40% or more and 90% or less. The hydrogen electrode-solid electrolyte layer composite according to claim 1.

5. The hydrogen electrode includes a first area including the contact surface, a second area including the surface, and an interface between the first area and the second area. The average film thickness from the contact surface to the interface surface is 50 μm or more and 300 μm or less. The average film thickness from the aforementioned surface to the aforementioned interface is 200 μm or more and 1000 μm or less. The hydrogen electrode-solid electrolyte layer composite according to claim 1.

6. The hydrogen electrode-solid electrolyte layer composite according to claim 1, wherein the coating rate of the nickel component in the pores in the first area is 20% or more and 75% or less.

7. The hydrogen electrode-solid electrolyte layer composite according to claim 1, wherein the impregnation rate of the nickel component in the pores in the first area is 15% or more and less than 45%.

8. The hydrogen electrode-solid electrolyte layer composite according to claim 1, wherein element A is Ba, element B is Zr, and element M is Y or Yb.

9. A hydrogen electrode-solid electrolyte layer composite according to any one of claims 1 to 8, and a porous oxygen electrode in contact with the solid electrolyte layer, The solid electrolyte layer is interposed between the oxygen electrode and the hydrogen electrode. The oxygen electrode is a compound having a perovskite structure. Proton-conducting cell structure.

10. The proton-conducting cell structure according to claim 9, wherein the oxygen electrode is lanthanum strontium cobalt ferrite or lanthanum strontium cobaltite.

11. A fuel cell comprising the proton-conducting cell structure described in claim 9.

12. A water vapor electrolytic cell comprising the proton-conducting cell structure described in claim 9.

13. A method for manufacturing a hydrogen electrode-solid electrolyte layer composite comprising a hydrogen electrode having pores and a solid electrolyte layer in contact with the hydrogen electrode, A first step of preparing a first paste sheet which will be a precursor to the solid electrolyte layer, and a second paste sheet and a third paste sheet which will be precursors to the hydrogen electrode, The second step involves stacking a first paste sheet, a second paste sheet, and a third paste sheet in the order of the first paste sheet, the second paste sheet, and the third paste sheet to obtain a paste sheet laminate, A third step involves heat-treating the paste sheet laminate to obtain a sintered body, A fourth step involves impregnating the sintered body with a nickel compound solution to obtain a nickel-impregnated sintered body. The fifth step involves heat-treating the nickel-impregnated sintered body to obtain a hydrogen electrode-solid electrolyte layer composite, The first paste sheet contains a metal oxide, The aforementioned metal oxide has a perovskite-type structure and is defined by the following formula (1): A ｘ B １－ｙ M ｙ O ３－δ (1) (In the formula, element A is at least one selected from the group consisting of Ba, Ca, and Sr, Element B is at least one selected from the group consisting of Ce and Zr. Element M is at least one selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In, and Sc. δ is the oxygen deficiency, satisfying 0.95 ≤ x ≤ 1 and 0 < y ≤ 0.

5. It is represented as, The second paste sheet comprises the metal oxide and a first pore-forming material having a first median diameter. The third paste sheet comprises the metal oxide and a second pore-forming material having a second median diameter. The first median diameter is smaller than the second median diameter. A method for manufacturing a hydrogen electrode-solid electrolyte layer composite.

14. The third step described above is The paste sheet laminate is heat-treated at a temperature of 400°C to 1000°C to remove at least a portion of the first and second pore-forming materials, This is a process of obtaining a sintered body by heat treatment at a temperature between 1400°C and 1650°C. The manufacturing method according to claim 13.

15. The fifth step is to heat-treat the nickel-impregnated sintered body at a temperature of 200°C to 600°C to fix the nickel component within the pores of the hydrogen electrode, thereby obtaining a hydrogen electrode-solid electrolyte layer composite. The manufacturing method according to claim 13.

16. The manufacturing method according to any one of claims 13 to 15, wherein the ratio of the second median diameter to the first median diameter (second median diameter / first median diameter) is 2.5 or more and 10 or less.

17. The first median diameter is 15 μm or more and 50 μm or less. The second median diameter is 30 μm or more and 200 μm or less. The manufacturing method according to claim 16.