WO2020235266A1 - Porous body, fuel cell equipped with same, and steam electrolysis device equipped with same - Google Patents

Abstract

A porous body provided with a backbone having a three-dimensional net-like structure, wherein the main body of the backbone contains at least two types of metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements.

Description

Porous material, fuel cell containing it, and steam electrolyzer including it

The present disclosure relates to a porous body, a fuel cell containing the porous body, and a steam electrolyzer including the porous body. This application claims priority based on Japanese Patent Application No. 2019-096108, which is a Japanese patent application filed on May 22, 2019. All the contents of the Japanese patent application are incorporated herein by reference.

Conventionally, porous materials such as metal porous materials have a high porosity and a large surface area, and therefore have been used in various applications such as battery electrodes, catalyst carriers, metal composite materials, and filters.

Japanese Unexamined Patent Publication No. 2012-132803 Japanese Unexamined Patent Publication No. 2012-119126 International Publication No. 2009/131180

The porous body according to one aspect of the present disclosure is a porous body having a skeleton having a three-dimensional network structure.
The main body of the skeleton contains at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements.

The fuel cell according to one aspect of the present disclosure is a fuel cell including a current collector for an air electrode and a current collector for a hydrogen electrode, and is at least one of the current collector for an air electrode or the current collector for a hydrogen electrode. Includes the above-mentioned porous body.

The steam electrolyzer according to one aspect of the present disclosure is a steam electrolyzer including a current collector for an air electrode and a current collector for a hydrogen electrode, which is the current collector for the air electrode or the current collector for the hydrogen electrode. At least one contains the above-mentioned porous body.

FIG. 1 is a schematic partial cross-sectional view showing an outline of a partial cross section of a skeleton in a porous body according to one aspect of the present disclosure. FIG. 2 is a cross-sectional view taken along the line AA of FIG. FIG. 3A is an enlarged schematic view focusing on one of the cell portions in the porous body in order to explain the three-dimensional network structure of the porous body according to one aspect of the present disclosure. FIG. 3B is a schematic view showing one aspect of the shape of the cell portion. FIG. 4A is a schematic view showing another aspect of the shape of the cell portion. FIG. 4B is a schematic view showing still another aspect of the shape of the cell portion. FIG. 5 is a schematic view showing aspects of the two joined cell portions. FIG. 6 is a schematic view showing aspects of the four joined cell portions. FIG. 7 is a schematic view showing one aspect of a three-dimensional network structure formed by joining a plurality of cell portions. FIG. 8 is a schematic cross-sectional view of the fuel cell according to one aspect of the present disclosure. FIG. 9 is a schematic cross-sectional view showing a fuel cell cell according to one aspect of the present disclosure. FIG. 10 is a schematic cross-sectional view showing a steam electrolyzer according to one aspect of the present disclosure. FIG. 11 is a schematic cross-sectional view showing a cell for a steam electrolyzer according to one aspect of the present disclosure.

[Issues to be resolved by this disclosure]
For example, Japanese Patent Application Laid-Open No. 2012-132803 (Patent Document 1) discloses a metal porous body having a skeleton containing a nickel-tin alloy as a main component as a metal porous body having properties of oxidation resistance and corrosion resistance. There is.

However, although the metal porous body described in Patent Document 1 is excellent in high temperature durability, when the metal porous body is used as an electrode of a solid oxide fuel cell (SOFC), it is conductive due to long-term use at 700 ° C. or higher. It was required to further suppress the decrease. As described above, when a porous body such as a metal porous body is used as an electrode of SOFC, there is room for further improvement.

This disclosure has been made in view of the above circumstances, and even when used as a current collector for an air electrode or a current collector for a hydrogen electrode of a fuel cell, the electric resistance is low and the operating voltage due to long-term use. It is an object of the present invention to provide a porous body in which a decrease in the voltage is suppressed, a fuel cell containing the same, and a steam electrolyzer including the same.

[Effect of this disclosure]
According to the above, even when used as a current collector for an air electrode or a current collector for a hydrogen electrode of a fuel cell, a porous body having low electrical resistance and suppressed decrease in operating voltage due to long-term use. A fuel cell including the above, and a steam electrolyzer including the same can be provided.

[Explanation of Embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.
[1] The porous body according to one aspect of the present disclosure is a porous body having a skeleton having a three-dimensional network structure.
The main body of the skeleton contains at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements. Even when the porous body having such characteristics is used as a current collector for an air electrode or a current collector for a hydrogen electrode of a fuel cell, the electric resistance is low and the decrease in operating voltage due to long-term use is suppressed. To.

[2] The main body of the skeleton is
When nickel is contained as a constituent element, cobalt is not contained and
When cobalt is contained as a constituent element, it is preferable that nickel is not contained.

[3] The main body of the skeleton preferably further contains oxygen as a constituent element. This aspect means that the porous body is in an oxidized state, and even in such a state, the porous body can maintain high conductivity in a high temperature environment.

[4] The oxygen is preferably contained in the main body of the skeleton in an amount of 0.1% by mass or more and 35% by mass or less. In this case, high conductivity can be maintained more effectively in a high temperature environment.

[5] The main body of the skeleton is the general formula (1):
A _x Z _3-x O ₄ (1)
Contains the metal oxides indicated by
In formula (1), A represents a metal element selected from the group consisting of nickel, manganese, cobalt, iron and copper, and Z represents a metal element selected from the group consisting of nickel, manganese, cobalt, iron and copper. As shown, x is preferably 1 or more and 2 or less. In this case, high electrolytic performance can be more effectively maintained in a high temperature environment without using expensive materials.

[6] The metal oxide contains at least one selected from the group consisting of MnNi ₂ O ₄ , MnCo ₂ O ₄ , CuNi ₂ O ₄ and FeCo ₂ O ₄ . In this case, it has the effect of exhibiting particularly high electrolytic performance.

[7] The main body of the skeleton preferably contains a spinel-type oxide. In this case as well, high conductivity can be maintained more effectively in a high temperature environment.

[8] The main body of the skeleton preferably does not contain chromium as a constituent element. As a result, the fuel cell using the porous body as an electrode can prevent performance deterioration due to chromium poisoning.

[9] The basis weight of the skeleton is preferably 200 g / m ² or more and 1000 g / m ² or less. By doing so, both mechanical strength and good gas diffusibility can be achieved.

[10] The skeleton preferably has an electrical resistivity of 2 Ω · cm ² or less at 800 ° C. By doing so, high conductivity can be maintained more effectively.

[11] When an observation image is obtained by observing the cross section of the main body of the skeleton at a magnification of 3000 times, the number of voids having a major axis of 1 μm or more appearing in an arbitrary 10 μm square region of the observation image is five. The following is preferable. Thereby, the strength can be sufficiently improved.

[12] The skeleton is preferably hollow. As a result, the porous body can be made lightweight, and the required amount of metal can be reduced.

[13] The porous body preferably has a sheet-like appearance and a thickness of 0.2 mm or more and 2 mm or less. As a result, it is possible to form an air electrode and a hydrogen electrode having a thinner thickness than in the past, and thus the required amount of metal can be reduced.

[14] The fuel cell according to one aspect of the present disclosure is a fuel cell including a current collector for an air electrode and a current collector for a hydrogen electrode, and is the current collector for the air electrode or the current collector for the hydrogen electrode. At least one of the above contains the porous body. A fuel cell having such characteristics has low electrical resistance in the air electrode current collector or the hydrogen electrode current collector, and suppresses a decrease in operating voltage due to long-term use, so that power can be generated efficiently. can do.

[15] The steam electrolyzer according to one aspect of the present disclosure is a steam electrolyzer including an air electrode current collector and a hydrogen electrode current collector, and is the air electrode current collector or the hydrogen electrode collector. At least one of the electric bodies contains the above-mentioned porous body. A steam electrolyzer having such characteristics has a reduced resistance during electrolysis, and thus can efficiently electrolyze steam.

[Details of Embodiments of the present disclosure]
Hereinafter, one embodiment of the present disclosure (hereinafter, also referred to as “the present embodiment”) will be described. However, this embodiment is not limited to this. In the present specification, the notation in the form of "A to B" means the upper and lower limits of the range (that is, A or more and B or less), and when the unit is not described in A and the unit is described only in B, A The unit of and the unit of B are the same.

≪Perforated body≫
The porous body according to the present embodiment is a porous body having a skeleton having a three-dimensional network structure. The main body of the skeleton contains at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements. Even when the porous body having such characteristics is used as a current collector for an air electrode or a current collector for a hydrogen electrode of a fuel cell, the electric resistance is low and the decrease in operating voltage due to long-term use is suppressed. To. Here, examples of the "porous material" in the present embodiment include a porous body made of a metal, a porous body made of an oxide of the metal, and a porous body containing a metal and an oxide of the metal.

Alloys containing at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements and oxides of the alloys both have high conductivity. That is, an alloy containing at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements can maintain high conductivity even when oxidized.
As a result of considering the above circumstances, when the main body of the skeleton contains at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements, the porous body having the skeleton is provided. Even when the body is used as a current collector for the air electrode or a current collector for the hydrogen electrode of a fuel cell whose oxidation progresses due to use, the electrical resistance is low and the decrease in operating voltage due to long-term use is suppressed. The present inventors have found this for the first time.

Further, the surface of the current collector for an air electrode used in a conventional fuel cell is coated with a chromium film in order to impart oxidation resistance (for example, Japanese Patent Application Laid-Open No. 2012-119126 (Patent Document). 2), International Publication No. 2009/131180 (Patent Document 3)).
However, chromium tends to evaporate and scatter on the current collector for the air electrode, degrading the performance of the fuel cell (chromium poisoning). Since the porous body according to the present embodiment can maintain high conductivity even when oxidized, it is not necessary to coat the chromium film. Therefore, the porous body according to the present embodiment is more suitable as a current collector for the air electrode of the fuel cell without fear of deterioration of the performance of the fuel cell due to chromium poisoning.

The appearance of the porous body can have various shapes such as a sheet shape, a rectangular parallelepiped shape, a spherical shape, and a columnar shape. Among them, the porous body preferably has a sheet-like appearance and a thickness of 0.2 mm or more and 2 mm or less. The thickness of the porous body is more preferably 0.5 mm or more and 1 mm or less. Since the thickness of the porous body is 2 mm or less, the porous body is thinner than the conventional one, and the required amount of metal can be reduced. Since the thickness of the porous body is 0.2 mm or more, the required strength can be provided. The thickness can be measured by, for example, a commercially available digital thickness gauge.

<Skeleton>
The porous body has a skeleton having a three-dimensional network structure as described above. The body of the skeleton contains at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements.

As shown in FIG. 1, the skeleton has a three-dimensional network structure having pores 14. Here, the details of the three-dimensional network structure will be described later. The skeleton 12 includes a main body 11 (hereinafter, may be referred to as “skeleton main body 11”) containing at least two kinds of metal elements as a constituent element, and a hollow inner 13 surrounded by the skeleton main body 11. .. The skeleton 12 forms a strut portion and a node portion, which will be described later. As described above, the skeleton 12 is preferably hollow.

Further, as shown in FIG. 2, the skeleton 12 preferably has a triangular cross-sectional shape orthogonal to the longitudinal direction thereof. However, the cross-sectional shape of the skeleton 12 should not be limited to this. The cross-sectional shape of the skeleton 12 may be a polygon other than a triangle such as a quadrangle or a hexagon. Further, the cross-sectional shape of the skeleton 12 may be circular. Here, in the present embodiment, polygons such as triangles, quadrangles and hexagons, and shapes such as circles are not limited to geometric shapes. For example, in the present embodiment, "triangle" is a concept including a substantially triangular shape. The same applies to other shapes.

That is, the skeleton 12 preferably has a hollow tubular shape inside 13 surrounded by the skeleton body 11, and has a triangular or other polygonal or circular cross section orthogonal to the longitudinal direction. Since the skeleton 12 has a tubular shape, the skeleton main body 11 has an inner wall forming an inner surface of the cylinder and an outer wall forming an outer surface of the cylinder. Since the inside 13 of the skeleton 12 surrounded by the skeleton body 11 is hollow, the porous body can be made very lightweight. However, the skeleton is not limited to being hollow and may be solid. In this case, the strength of the porous body can be improved.

The skeleton preferably has a basis weight of 200 g / m ² or more and 1000 g / m ² or less. The basis weight is more preferably 250 g / m ² or more and 900 g / m ² or less. As will be described later, the basis weight can be appropriately adjusted when a predetermined alloy plating is performed on the conductive resin molded product which has been subjected to the conductivity treatment for imparting conductivity. For example, when the porous body has a sheet-like appearance, the basis weight can be calculated by the following formula. In one aspect of the present embodiment, the basis weight of the skeleton can be grasped as the basis weight of the porous body.
Metsuke amount (g / m ² ) = M (g) / S (m ² )
M: Skeleton mass [g]
S: Area of the main surface of the appearance in the skeleton [m ² ]

The above-mentioned basis weight is converted into the mass per unit volume of the skeleton (apparent density of the skeleton) as follows. That is, the apparent density of the skeleton is preferably 0.14 g / cm ³ or more and 0.75 g / cm ³ or less, and more preferably 0.18 g / cm ³ or more and 0.65 g / cm ³ or less. Here, the "apparent density of the skeleton" is defined by the following equation. In one aspect of the present embodiment, the apparent density of the skeleton can be grasped as the apparent density of the porous body.
Apparent density of skeleton (g / cm ³ ) = M (g) / V (cm ³ )
M: Skeleton mass [g]
V: Volume of appearance shape in skeleton [cm ³ ]

The porosity of the skeleton is preferably 40% or more and 98% or less, more preferably 45% or more and 98% or less, and most preferably 50% or more and 98% or less. When the porosity of the skeleton is 40% or more, the porous body can be made very lightweight, and the surface area of the porous body can be increased. When the porosity of the skeleton is 98% or less, the porous body can be provided with sufficient strength.

The porosity of the skeleton is defined by the following equation.
Porosity (%) = [1- {M / (V × d)}] × 100
M: Skeleton mass [g]
V: Volume of appearance shape in skeleton [cm ³ ]
d: Density of metal or metal oxide constituting the skeleton [g / cm ³ ]

The average pore diameter of the skeleton is preferably 350 μm or more and 3500 μm or less. When the average pore diameter of the skeleton is 350 μm or more, the strength of the porous body can be increased. When the average pore diameter of the skeleton is 3500 μm or less, the bendability (bending workability) of the porous body can be improved. From these viewpoints, the average pore diameter of the skeleton is more preferably 400 μm or more and 1000 μm or less, and most preferably 450 μm or more and 900 μm or less.

The average pore size of the skeleton can be determined by the following method. That is, first, an observation image obtained by magnifying the surface of the skeleton at a magnification of 3000 times is prepared for at least 10 visual fields using a microscope, and in each of these 10 visual fields, per arbitrary 1 inch (25.4 mm = 25400 μm) in the cell portion described later. Find the number of pores in. Furthermore, in terms of the number of pores in the 10 fields was defined as the average value (n _c), which the value calculated from substituted into the following equation, the average pore diameter of the skeleton.
Average pore diameter (μm) = 25400 μm / n _c

Here, the porosity and average pore diameter of the skeleton and the porosity and average pore diameter of the porous body refer to the same thing.

When an observation image is obtained by observing the cross section of the main body of the skeleton at a magnification of 3000 times, the number of voids having a major axis of 1 μm or more appearing in an arbitrary 10 μm square region of the observation image is 5 or less. Is preferable. The number of voids is more preferably 3 or less. Thereby, the strength of the porous body can be sufficiently improved. Further, it is understood that the main body of the skeleton is different from the molded body formed by sintering fine powder because the number of voids is 5 or less. This is because a large number of the above-mentioned voids is observed in the molded product obtained by sintering the fine powder. The lower limit of the number of voids observed is, for example, zero. Here, the "number of voids" means the average number of voids obtained by observing each of a plurality of (for example, 10) "10 μm square regions" in the cross section of the skeleton body.

The cross section of the skeleton can be observed by using an electron microscope. Specifically, it is preferable to obtain the above-mentioned "number of voids" by observing the cross section of the skeleton body in 10 visual fields. The cross section of the skeleton body may be a cross section orthogonal to the longitudinal direction of the skeleton, or may be a cross section parallel to the longitudinal direction of the skeleton. In the observed image, the voids can be distinguished from others by the color contrast (difference between light and dark). The upper limit of the major axis of the void should not be limited, but is, for example, 10000 μm.

The average thickness of the skeleton body is preferably 10 μm or more and 50 μm or less. Here, the "thickness of the skeleton body" means the shortest distance from the inner wall, which is the interface with the hollow inside the skeleton, to the outer wall outside the skeleton, and the average value thereof is defined as the "average thickness of the skeleton body". .. The thickness of the skeleton body can be determined by observing the cross section of the skeleton with an electron microscope.

Specifically, the average thickness of the skeleton body can be obtained by the following method. First, the sheet-shaped porous body is cut so that the cross section of the skeleton body appears. An observation image is obtained by selecting one cut cross section, magnifying it at a magnification of 3000 times, and observing it with an electron microscope. Next, the thickness of any one side of the polygon (for example, the triangle in FIG. 2) forming one skeleton appearing in this observation image is measured at the center of the one side, and this is measured as the skeleton. The thickness of the main body. Further, by performing such a measurement on 10 observation images (10 fields of view), the thickness of the skeleton body at 10 points can be obtained. Finally, by calculating these average values, the average thickness of the skeleton body can be obtained.

The skeleton is more preferable electrical resistivity at 800 ° C. it is preferably 2 [Omega · cm ² or less, 0.01 Ohm · cm ² or more 2 [Omega · cm ² or less. The electrical resistivity can be obtained, for example, as follows. The porous body to be evaluated is maintained at 800 ° C. in an air atmosphere, and the electrical resistivity (unit: Ω · cm ² ) is measured by the four-terminal method.
When the appearance of the porous body is sheet-like, the measurement direction of the electrical resistivity is the thickness direction of the porous body. In one aspect of the present embodiment, the electrical resistivity of the skeleton can be grasped as the electrical resistivity of the porous body.

(Three-dimensional network structure)
The porous body has a skeleton having a three-dimensional network structure. The skeleton includes a strut portion and a node portion connecting the plurality of strut portions. In the present embodiment, the "three-dimensional network structure" means a three-dimensional network structure. The three-dimensional network structure is formed by the skeleton. Hereinafter, the three-dimensional network structure will be described in detail.

As shown in FIG. 7, the three-dimensional network structure 30 has a cell portion 20 as a basic unit, and is formed by joining a plurality of cell portions 20. As shown in FIGS. 3A and 3B, the cell portion 20 includes a support column portion 1 and a node portion 2 that connects a plurality of support column portions 1. Although the terms of the support column 1 and the node section 2 are explained separately for convenience, there is no clear boundary between them. That is, in the three-dimensional network structure 30, a plurality of column portions 1 and a plurality of node portions 2 are integrally formed to form a cell portion 20, and the cell portion 20 is used as a constituent unit. Hereinafter, in order to facilitate understanding, the cell portion of FIG. 3A will be described as if it were a regular dodecahedron of FIG. 3B.

First, the support column portion 1 and the node portion 2 each form a frame portion 10 which is a planar polygonal structure due to the existence of a plurality of each. In FIG. 3B, the polygonal structure of the frame portion 10 is a regular pentagon, but it may be a polygon other than a regular pentagon such as a triangle, a quadrangle, or a hexagon. Here, with respect to the structure of the frame portion 10, it can be grasped that a plane polygonal hole is formed by the plurality of support columns 1 and the plurality of node portions 2. In the present embodiment, the hole diameter of the planar polygonal hole means the diameter of a circle circumscribing the planar polygonal hole defined by the frame portion 10. The frame portion 10 forms a cell portion 20 which is a three-dimensional polyhedral structure by combining a plurality of the frame portions 10. At this time, one support column portion 1 and one node portion 2 are shared by a plurality of frame portions 10.

As shown in the schematic view of FIG. 2 described above, the strut portion 1 preferably has a hollow tubular shape and has a triangular cross section, but is not limited to this. The support column 1 may have a polygonal shape other than a triangle such as a quadrangle or a hexagon, or a circular shape. The shape of the node portion 2 may be a shape of a sharp edge having vertices, a planar shape such that the vertices are chamfered, or a radius is given to the vertices. It may have a curved surface shape.

The polyhedron structure of the cell portion 20 is a dodecahedron in FIG. 3B, but may be another polyhedron such as a cube, an icosahedron (FIG. 4A), or a truncated icosahedron (FIG. 4B). Here, with respect to the structure of the cell portion 20, it can be grasped that a three-dimensional space (pore portion 14) surrounded by a virtual plane A defined by each of the plurality of frame portions 10 is formed. In the present embodiment, the pore diameter of the three-dimensional space (hereinafter, also referred to as “pore diameter”) can be grasped as the diameter of a sphere circumscribing the three-dimensional space defined by the cell portion 20. However, the pore diameter of the porous body in the present embodiment is calculated based on the above-mentioned calculation formula for convenience. That is, the pore diameter (pore diameter) of the three-dimensional space defined by the cell portion 20 refers to the same as the porosity and the average pore diameter of the skeleton.

The cell portion 20 forms a three-dimensional network structure 30 by combining a plurality of the cell portions 20 (FIGS. 5 to 7). At this time, the frame portion 10 is shared by the two cell portions 20. It can be grasped that the three-dimensional network structure 30 includes the frame portion 10 or the cell portion 20.

As described above, the porous body has a three-dimensional network structure that forms a planar polygonal hole (frame portion) and a three-dimensional space (cell portion). Therefore, it can be clearly distinguished from a two-dimensional network structure having only planar holes (for example, punching metal, mesh, etc.). Further, since the porous body has a plurality of support columns and a plurality of node portions integrally to form a three-dimensional network structure, it is like a non-woven fabric formed by entwining fibers, which are constituent units, with each other. It can be clearly distinguished from the structure. Since the porous body has such a three-dimensional network structure, it can have continuous ventilation holes.

In the present embodiment, the three-dimensional network structure is not limited to the above-mentioned structure. For example, the cell portion may be formed by a plurality of frame portions having different sizes and planar shapes. Further, the three-dimensional network structure may be formed by a plurality of cell portions having different sizes and three-dimensional shapes. The three-dimensional network structure may partially include a frame portion in which a planar polygonal hole is not formed, or a cell portion in which a three-dimensional space is not formed (a cell portion whose inside is solid). ) May be included in a part.

(Metal elements that make up the body of the skeleton)
The body of the skeleton contains at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements as described above. The main body of the skeleton does not exclude containing a third component other than the above-mentioned metal element as long as it does not affect the action and effect of the porous body of the present disclosure. However, the main body of the skeleton is preferably composed of the above two kinds of metal elements as a metal component. Examples of the combination of the above two types of metal elements include nickel and manganese, nickel and iron, nickel and copper, manganese and cobalt, iron and cobalt, and iron and copper. In one aspect of the present embodiment, the main body of the skeleton preferably does not contain nickel when it contains nickel as a constituent element, and does not contain nickel when it contains cobalt as a constituent element. In another aspect of this embodiment, the at least two metal elements are preferably the main components in the body of the skeleton. Here, the "main component" in the skeleton means the component having the largest mass ratio in the skeleton. More specifically, the "main component" refers to a component having a content ratio of more than 50% by mass in the skeleton. That is, it is preferable that the total content of at least the two metal elements in the skeleton exceeds 50% by mass.

The total content ratio of the above two metal elements in the main body of the skeleton is, for example, the state before using the porous body as the current collector for the air electrode or the current collector for the hydrogen electrode of SOFC, that is, the porous body is 700 ° C. or higher. In the state before being exposed to the high temperature of the above, it is preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 95% by mass or more. The total content ratio of the at least two kinds of metal elements may be 100% by mass.

The higher the total content of the above two metal elements, the more the oxide produced when the porous body is used for the SOFC air electrode current collector or hydrogen electrode current collector is at least the above. The proportion of spinel-type oxides consisting of at least one of the two metal elements and oxygen tends to increase. As a result, the porous body can maintain high conductivity even when used in a high temperature environment.

(oxygen)
The body of the skeleton preferably further contains oxygen as a constituent element. Specifically, oxygen is more preferably contained in the main body of the skeleton in an amount of 0.1% by mass or more and 40% by mass or less. Oxygen in the body of the skeleton can be detected, for example, after using a porous body as a current collector for the air electrode or a current collector for the hydrogen electrode of an SOFC. That is, in the state after the porous body is exposed to a high temperature of 700 ° C. or higher, oxygen is preferably contained in the main body of the skeleton in an amount of 0.1% by mass or more and 40% by mass or less. Oxygen is more preferably 10 to 30% by mass, still more preferably 25 to 28% by mass in the main body of the skeleton. Oxygen in the main body of the skeleton may be detected immediately after the production of the porous body.

When oxygen is contained as a constituent element in the main body of the skeleton in an amount of 0.1% by mass or more and 40% by mass or less, it is possible to know the thermal history that the porous body was exposed to a high temperature of 700 ° C. or more. Further, when the porous body is used as a current collector for an air electrode or a current collector for a hydrogen electrode of SOFC, it is exposed to a high temperature of 700 ° C. or higher, and at least one of the above two metal elements is contained in the main body of the skeleton. , And when a spinel-type oxide composed of oxygen is produced, the main body of the skeleton tends to contain oxygen in an amount of 0.1% by mass or more and 40% by mass or less as a constituent element.

(Metal oxide)
In the present embodiment, the main body of the skeleton is the general formula (1):
A _x Z _3-x O ₄ (1)
(In the formula (1), A represents a metal element selected from the group consisting of nickel, manganese, cobalt, iron and copper, and Z represents a metal element selected from the group consisting of nickel, manganese, cobalt, iron and copper. , And x is 1 or more and 2 or less.) It is preferable to contain the metal oxide represented by.

(Mole ratio of metal element A to the total number of moles of metal element A and metal element Z)
In the main body of the skeleton, the molar ratio of the metal element A to the total number of moles of the metal element A and the metal element Z is preferably 0.1 or more and 0.8 or less, and preferably 0.2 or more and 0.5 or less. More preferred. When a porous body having a skeleton having such a composition is used as an electrode of SOFC or the like, as described above, A _x Z _3-x O ₄ (however, 1 ≦ x ≦ 2), typically, is generated by oxidation. A spinel-type oxide represented by the chemical formula of AZ ₂ O ₄ or A ₂ ZO ₄ is produced in the skeleton. Oxidation of the skeleton may produce spinel-type oxides represented by the chemical formula of AZ ₂ O ₄ (where A is the same element as Z). The spinel-type oxide exhibits high conductivity, so that the porous body can maintain high conductivity even when the entire skeleton is oxidized by use in a high temperature environment.

That is, the main body of the skeleton preferably contains a spinel-type oxide. As a result, the porous body can more effectively maintain high conductivity even when it is oxidized. When the oxygen content in the main body of the skeleton is out of the above range, the porous body tends not to have the ability to more effectively maintain high conductivity when oxidized, as desired.

Specific examples of the above metal oxides include Nimn ₂ O ₄ , MnNi ₂ O ₄ , MnCo ₂ O ₄ , Comn ₂ O ₄ , CuFe ₂ O ₄ , CuNi ₂ O ₄ , NiFe ₂ O ₄ , FeCo ₂ O ₄ , Examples include FeNi ₂ O ₄ and CoFe ₂ O ₄ . In the present embodiment, the metal oxide preferably contains at least one selected from the group consisting of MnNi ₂ O ₄ , MnCo ₂ O ₄ , CuNi ₂ O ₄ and FeCo ₂ O ₄ . These can maintain particularly high electrolytic performance.

(Third component)
The main body of the skeleton can further contain a third component as a constituent element as described above, as long as it does not affect the action and effect of the porous body of the present disclosure. The body of the skeleton contains, for example, silicon, magnesium, carbon, tin, aluminum, sodium, tungsten, titanium, phosphorus, boron, silver, gold, molybdenum, nitrogen, sulfur, fluorine, chlorine, etc. as the third component. May be good. In one aspect of this embodiment, it is preferable that the main body of the skeleton does not contain chromium as a constituent element. The third component may be contained as an unavoidable impurity that is inevitably mixed in, for example, in the production method described later. For example, as an example of unavoidable impurities, an element contained in the conductive coating layer formed by the conductive treatment described later can be mentioned. Further, the main body of the skeleton may contain the above-mentioned oxygen as a third component in a state before using the porous body as a current collector for an air electrode or a current collector for a hydrogen electrode of SOFC. The third component in the main body of the skeleton is preferably 5% by mass or less by itself, and preferably 10% by mass or less in total.

In one aspect of the present embodiment, the main body of the skeleton may further contain at least one non-metal element selected from the group consisting of nitrogen, sulfur, fluorine, and chlorine as a constituent element, and the non-metal element may further contain. , The total content ratio may be 5 ppm or more and 10000 ppm or less with respect to the main body of the skeleton. Preferably, the total content of the non-metal element is 10 ppm or more and 8000 ppm or less with respect to the main body of the skeleton.
Further, the main body of the skeleton may further contain phosphorus as a constituent element, and the content ratio thereof may be 5 ppm or more and 50,000 ppm or less with respect to the main body of the skeleton. Preferably, the phosphorus content is 10 ppm or more and 40,000 ppm or less.

In another aspect of the present embodiment, the body of the skeleton may further contain at least two or more non-metal elements selected from the group consisting of nitrogen, sulfur, fluorine, chlorine, and phosphorus as constituent elements. The total content of the non-metal elements may be 5 ppm or more and 50,000 ppm or less with respect to the main body of the skeleton. Preferably, the total content of the non-metal element is 10 ppm or more and 10000 ppm or less with respect to the main body of the skeleton.

When the porous body is used as a current collector for an air electrode or a current collector for a hydrogen electrode of a fuel cell, it is exposed to a high temperature environment of 700 ° C. or higher as described above, but the main body of the skeleton is the non-metal described above. By containing an element as a constituent element, high strength (creep characteristics) can be maintained.

(Measuring method of content ratio of each element)
Regarding the oxygen content ratio (mass%) in the main body of the skeleton, the EDX device (for example, SEM part: product) attached to the electron microscope (SEM) is compared with the observation image (electron microscope image) of the cross section of the main body of the cut skeleton. It can be obtained by analysis using the name "SUPRA35VP", manufactured by Carl Zeiss Microscopy Co., Ltd., EDX part: trade name "octane super", manufactured by Ametec Co., Ltd.). It is also possible to determine the content ratio of metal elements in the main body of the skeleton by the above EDX device. Specifically, the mass%, mass ratio, and the like of oxygen and metal elements in the main body of the skeleton can be obtained based on the atomic concentration of each element detected by the EDX device. Further, regarding whether or not the main body of the skeleton has a spinel-type oxide composed of a metal element and oxygen, an X-ray diffraction (XRD) method is performed in which the cross section is irradiated with X-rays and the diffraction pattern is analyzed. It can be specified by using it.

Regarding the measuring device for identifying whether or not the main body of the skeleton has a spinel-type oxide, for example, an X-ray diffractometer (for example, trade name (model number): "Empyrene", manufactured by Spectris Co., Ltd., analysis software: "integrated powder" X-ray analysis software PDXL ”, manufactured by Rigaku Co., Ltd.) can be used. The measurement conditions may be as follows, for example.

(Measurement condition)
X-ray diffraction method: θ-2θ method Measurement system: Parallel beam optical system Mirror scan range (2θ): 10 to 90 °
Accumulation time: 1 second / step Step: 0.03 °.

≪Fuel cell≫
The fuel cell according to the present embodiment is a fuel cell including a current collector for an air electrode and a current collector for a hydrogen electrode. At least one of the current collector for the air electrode and the current collector for the hydrogen electrode contains the porous body. When the above-mentioned current collector for air electrode or current collector for hydrogen electrode is used as the current collector for air electrode or hydrogen electrode of a fuel cell as described above, the electric resistance is low and the electric resistance is long. Includes a porous body that suppresses a decrease in operating voltage due to use. Therefore, the above-mentioned current collector for air electrode or current collector for hydrogen electrode can be suitably used as at least one of the current collector for air electrode or current collector for hydrogen electrode of SOFC. In the fuel cell, since the porous body contains at least two kinds of metal elements, it is more preferable to use the porous body as a current collector for an air electrode.

FIG. 8 is a schematic cross-sectional view showing a fuel cell according to one aspect of the present disclosure. The fuel cell 150 includes a current collector 110 for a hydrogen electrode, a current collector 120 for an air electrode, and a cell 100 for a fuel cell. The fuel cell cell 100 is provided between the hydrogen electrode current collector 110 and the air electrode current collector 120. Here, the "current collector for hydrogen electrode" means a current collector on the side of supplying hydrogen in the fuel cell. The “air electrode current collector” means a current collector on the side that supplies a gas containing oxygen (for example, air) in a fuel cell.

FIG. 9 is a schematic cross-sectional view showing a fuel cell cell according to one aspect of the present disclosure. The fuel cell cell 100 includes an air electrode 102, a hydrogen electrode 108, an electrolyte layer 106 provided between the air electrode 102 and the hydrogen electrode 108, and the electrolyte layer 106 and the air electrode 102. An intermediate layer 104 provided between them is provided to prevent a reaction. As the air electrode, for example, an oxide of LaSrCo (LSC) is used. As the electrolyte layer, for example, a Y-doped Zr oxide (YSZ) is used. As the intermediate layer, for example, a Gd-doped Ce oxide (GDC) is used. Examples of the hydrogen electrode include a mixture of YSN and NiO ₂ , metallic Ni, and the like.

The fuel cell 150 further includes a first interconnector 112 having a fuel flow path 114 and a second interconnector 122 having an oxidant flow path 124. The fuel flow path 114 is a flow path for supplying fuel (for example, hydrogen) to the hydrogen electrode 108. The fuel flow path 114 is provided on the main surface of the first interconnector 112, which faces the current collector 110 for hydrogen poles. The oxidant flow path 124 is a flow path for supplying an oxidant (for example, oxygen) to the air electrode 102. The oxidant flow path 124 is provided on the main surface of the second interconnector 122 facing the air electrode current collector 120.

≪Steam electrolyzer≫
The steam electrolyzer according to the present embodiment (also referred to as "steam electrolyzer") is a steam electrolyzer including a current collector for an air electrode and a current collector for a hydrogen electrode, and has the same structure as the above fuel cell. Be prepared. At least one of the current collector for the air electrode and the current collector for the hydrogen electrode contains the porous body. The current collector for the air electrode or the current collector for the hydrogen electrode includes a porous body having an appropriate strength as a current collector for the steam electrolyzer as described above. Therefore, the above-mentioned current collector for air electrode or current collector for hydrogen electrode is suitable as at least one of the current collector for air electrode or the current collector for hydrogen electrode of the steam electrolyzer. In the steam electrolyzer, since the porous body contains at least two kinds of metal elements, it is more preferable to use the porous body as a current collector for an air electrode. As an example, the resistance is lowered and the electrolytic voltage is lowered. is there.

FIG. 10 is a schematic cross-sectional view showing a steam electrolyzer according to one aspect of the present disclosure. The steam electrolyzer 250 includes a current collector 210 for a hydrogen electrode, a current collector 220 for an air electrode, and a cell 200 for a steam electrolyzer. The steam electrolyzer cell 200 is provided between the hydrogen electrode current collector 210 and the air electrode current collector 220. Here, the "hydrogen electrode current collector" means a current collector on the side where hydrogen is generated in the steam electrolyzer. The “air electrode current collector” means a current collector on the side that supplies a gas containing water vapor (for example, humidified air) in the water vapor electrolyzer. The current collector for the air electrode can also be grasped as a current collector on the side where oxygen is generated in the steam electrolyzer. Further, in one aspect of the present embodiment, the gas containing water vapor may be supplied from the side of the current collector for the hydrogen electrode.

FIG. 11 is a schematic cross-sectional view showing a cell for a steam electrolyzer according to one aspect of the present disclosure. The cell 200 for a steam electrolyzer has an air electrode 202, a hydrogen electrode 208, an electrolyte layer 206 provided between the air electrode 202 and the hydrogen electrode 208, and the electrolyte layer 206 and the air electrode 202. An intermediate layer 204 provided between them is provided in order to prevent a reaction with the above. As the air electrode, for example, an oxide of LaSrCo (LSC) is used. As the electrolyte layer, for example, a Y-doped Zr oxide (YSZ) is used. As the intermediate layer, for example, a Gd-doped Ce oxide (GDC) is used. As the hydrogen electrode, for example, a mixture of YSZ and NiO ₂ is used.

The steam electrolyzer 250 further includes a first interconnector 212 having a hydrogen flow path 214 and a second interconnector 222 having a steam flow path 224. The hydrogen flow path 214 is a flow path for recovering hydrogen from the hydrogen electrode 208. The hydrogen flow path 214 is provided on the main surface of the first interconnector 212, which faces the current collector 210 for the hydrogen electrode. The water vapor flow path 224 is a flow path for supplying water vapor (for example, humidified air) to the air electrode 202. The water vapor flow path 224 is provided on the main surface of the second interconnector 222, which faces the current collector 220 for the air electrode.

≪Manufacturing method of porous body≫
The porous body according to the present embodiment can be produced by appropriately using a conventionally known method. Examples of the method for producing the porous body include an electrolytic plating method, a dipping method, a sputtering method, a chemical vapor deposition method (CVD method), and an electroless plating method. The method for producing the porous body is preferably, for example, an electrolytic plating method or a dipping method described later.

(Electroplating method)
First, a manufacturing method using the electrolytic plating method will be described. That is, a step of obtaining a conductive resin molded body by forming a conductive coating layer on a resin molded body having a three-dimensional network structure (first step), and at least two kinds of metals on the conductive resin molded body. A step of obtaining a porous body precursor by plating an alloy containing an element as a constituent element (second step) and a step of heat-treating the porous body precursor to remove resin components in a conductive resin molded product. It is preferable to produce a porous body by a method for producing a porous body, which includes a step of incineration and removing the porous body to obtain a porous body (third step).
The manufacturing method may further include a step (fourth step) of oxidizing the porous body after the third step.

<First step>
First, a sheet of a resin molded body having a three-dimensional network structure (hereinafter, also simply referred to as “resin molded body”) is prepared. A polyurethane resin, a melamine resin, or the like can be used as the resin molded product. Further, as a conductive treatment for imparting conductivity to the resin molded body, a conductive coating layer is formed on the surface of the resin molded body. Examples of the conductive treatment include the following methods.
(1) Forming a conductive coating layer on the surface of a resin molded product by means such as coating or dipping a conductive paint containing conductive particles such as carbon and conductive ceramic and a binder.
(2) Forming a layer of conductive metal such as nickel and copper on the surface of the resin molded product by electroless plating.
(3) Forming a layer made of conductive metal on the surface of a resin molded body by a vapor deposition method or a sputtering method.
As a result, a conductive resin molded product can be obtained.

<Second step>
Next, a porous precursor is obtained by plating an alloy containing at least two kinds of metal elements as constituent elements on the conductive resin molded product. Although electroless plating can be applied to the above alloy plating method, it is preferable to use electrolytic plating (so-called electroplating) from the viewpoint of efficiency. In the electrolytic plating of the above alloy, a conductive resin molded body is used as a cathode. Here, as a method for obtaining the porous precursor by electroplating, the following two methods can be mentioned.
(Method 1) Electroplating is performed on the conductive resin molded product using a plating bath containing at least two metal elements as constituent elements.
(Method 2) First, electroplating is performed on the conductive resin molded body using a plating bath containing the first metal element (for example, nickel element) among the at least two kinds of metal elements. Next, the conductive resin molded body plated with the first metal element using a plating bath containing the second metal element (for example, copper element) among the at least two kinds of metal elements. Electroplating is performed on top. At this time, the electrolytic plating of the first metal element and the electrolytic plating of the second metal element may be alternately repeated. Then, a high temperature (for example, 1000 ° C.) heat diffusion treatment is performed in a hydrogen atmosphere.

As the plating bath used for electrolytic plating of the above alloy, a known one can be used. For example, in the case of nickel plating, a watt bath, a chloride bath, a sulfamic acid bath and the like can be used. An example of a plating bath for electrolytic plating of nickel, copper, and iron is shown below.

(Bath composition)
(For nickel plating)
Salt (aqueous solution): Nickel sulfamate (450 g / L)
Boric acid: 30 g / L

(For copper plating)
Salt (aqueous solution): copper pyrophosphate (90 g / L), potassium pyrophosphate (375 g / L)
Ammonia water: 3 mL / L (specific gravity 0.9)
Orthophosphoric acid: 80 g / L

(In the case of iron plating)
Salt _{(aq): FeCl 2 · 4H 2 O} (2M), CaCl 2 (1.6M)
Saccharin: 9 mM
Sodium dodecyl sulfate: 0.3 mM
Gluconic acid: 10 mM

(Electrolysis conditions)
Temperature: 40-60 ° C
Current density: 0.5-10A / dm ²
Anode: Insoluble anode or soluble anode

From the above, it is possible to obtain a porous precursor in which a predetermined alloy is plated on the conductive resin molded body. When non-metal elements such as nitrogen, sulfur, fluorine, chlorine, and phosphorus are added, they can be contained in the porous precursor by adding various additives into the plating bath. Examples of various additives include, but are not limited to, sodium nitrate, sodium sulfate, sodium fluoride, sodium chloride, and sodium phosphate, as long as each non-metal element is contained.

<Third step>
Subsequently, the porous body precursor is heat-treated to incinerate the resin component in the conductive resin molded body, and the resin component is removed to obtain a porous body having a hollow skeleton. Thereby, a porous body having a skeleton having a three-dimensional network structure can be obtained. The temperature and atmosphere of the heat treatment for removing the resin component may be, for example, 600 ° C. or higher, and may be an oxidizing atmosphere such as air.

Here, the average pore diameter of the porous body obtained by the above method is substantially equal to the average pore diameter of the resin molded product. Therefore, the average pore diameter of the resin molded product used to obtain the porous body may be appropriately selected according to the application to which the porous body is applied. Since the porosity of the porous body is finally determined by the amount of metal to be plated (weight), the basis weight of the alloy to be plated should be appropriately selected according to the porosity required for the final product, the porous body. Just do it. The porosity and average pore diameter of the resin molded product are defined in the same manner as the porosity and average pore diameter of the skeleton described above, and by replacing "skeleton" with "resin molded product" and applying the above formula. Can be obtained based on.

<4th process>
If necessary, the porous body may be further subjected to an oxidation treatment to obtain an alloy constituting the porous body as a metal oxide. The oxidation treatment is not particularly limited, and examples thereof include oxidation treatment (100 to 1500 ° C., 1 to 1000 minutes) of the porous body in an oxidizing atmosphere (oxygen concentration of 20 to 100%).

(Dipping method)
Specific examples of the manufacturing method using the dipping method are as follows. First, zirconia balls are added to a metal oxide powder containing at least two of the above metal elements as constituent elements, an alcohol (for example, 1-methoxy-2-propanol), and a binder (for example, hydroxypropyl cellulose), and painted. Mix using a shaker. Next, a base material having a three-dimensional network structure is dipped in a mixed solution containing the powder of the metal oxide, pulled up, and then dried in a constant temperature bath adjusted to 50 ° C. Then, the dried base material is fired at 1000 ° C. for 2 hours using an electric furnace, and then cooled to obtain a porous body.

By the above manufacturing method, the porous body according to the present embodiment can be manufactured. The porous body has a skeleton having a three-dimensional network structure, and the main body of the skeleton contains at least two kinds of metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements. Therefore, even when the porous body is used as a current collector for an air electrode or a current collector for a hydrogen electrode of a fuel cell, the electric resistance is low and a decrease in operating voltage due to long-term use is suppressed.
Further, the porous body according to the present embodiment is also suitable as an electrode used for steam electrolysis in which a reaction opposite to the chemical reaction occurring in the fuel cell is occurring. That is, the porous body can have an appropriate strength as a current collector for an air electrode or a current collector for a hydrogen electrode of a steam electrolyzer.

The above description includes the features described below.
(Appendix 1)
A porous body having a skeleton having a three-dimensional network structure.
The main body of the skeleton is a porous body containing at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements.
(Appendix 2)
The porous body according to Appendix 1, wherein the main body of the skeleton further contains oxygen as a constituent element.
(Appendix 3)
The main body of the skeleton has the general formula (1):
A _x Z _3-x O ₄ (1)
(In the formula (1), A represents a metal element selected from the group consisting of nickel, manganese, cobalt, iron and copper, and Z represents a metal element selected from the group consisting of nickel, manganese, cobalt, iron and copper. The porous body according to Appendix 2, which contains the metal oxide represented by (x) of 1 or more and 2 or less.
(Appendix 4)
The skeleton is the porous body according to any one of Appendix 1 to Appendix 3, which has a basis weight of 200 to 1000 g / m ² .

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

≪Preparation of porous body≫
<Sample 1 to Sample 5>
The porous bodies of Samples 1 to 5 were produced by using the dipping method described above. Here, the metal oxide powders shown in Table 1 below were used as raw materials.

<Sample 6>
The porous body of Sample 6 was produced by using an electrolytic plating method. First, a 1.5 mm thick polyurethane resin sheet was prepared as a resin molded body having a three-dimensional network structure (first step). When the porosity and the average porosity of the polyurethane resin sheet were calculated based on the above formula, the porosity was 96% and the average porosity was 450 μm.

Next, a conductive coating material was prepared by dispersing 100 g of carbon black, which is an amorphous carbon having a particle size of 0.01 to 0.2 μm, in 0.5 L of a 10 mass% acrylic acid ester resin aqueous solution. The conductive coating material was impregnated into the resin molded product, then squeezed with a roll and dried to form a conductive coating layer on the surface of the resin molded product. As a result, a conductive resin molded product was obtained.

Electroplating was performed using the conductive resin molded product as a cathode under the following bath composition and electrolytic conditions (second step). First, copper plating was performed, then nickel plating was performed, and then heat treatment was performed in a reducing atmosphere to attach 700 g / m ² of a Cu—Ni alloy onto the conductive resin molded body, thereby obtaining a porous precursor.

<Bath composition>
(For copper plating)
Salt (aqueous solution): copper pyrophosphate (90 g / L), potassium pyrophosphate (375 g / L)
Ammonia water: 3 mL / L (specific gravity 0.9)
Orthophosphoric acid: 80 g / L
(For nickel plating)
Salt (aqueous solution): Nickel sulfamate (450 g / L)
Boric acid: 30 g / L.

<Electrolysis conditions>
(Common to all plating)
Temperature: 40-60 ° C
Current density: 0.5-10A / dm ²
Anode: Soluble anode.

The porous precursor was heat-treated (650 ° C., air atmosphere) to incinerate the resin component in the conductive resin molded product, and the resin component was removed (third step). Then, the porous precursor (that is, the porous body) heat-treated at 1000 ° C. for 24 hours in a reducing atmosphere (100% hydrogen) is subjected to an oxidation treatment (800 ° C., 900 minutes) in an atmospheric atmosphere (fourth step). ), A porous body (Celmet) in which the main body of the skeleton is CuNi ₂ O ₄ was obtained. The skeleton was hollow.

<Sample 7>
The bath composition used in the electrolytic plating was an aqueous solution of nickel sulfamate (150 g / L) and iron sulfamate (300 g / L). By making the same as Sample 6 except for the above bath composition, a porous body (Celmet) having a skeleton body of NiFe ₂ O ₄ was obtained.

<Sample 8>
The bath composition used in the electrolytic plating was an aqueous solution of iron sulfamate (150 g / L) and cobalt sulfamate (300 g / L). By making the same as Sample 6 except for the above bath composition, the main body of the skeleton was FeCo ₂ O ₄ (Celmet).

<Sample 9>
The bath composition used in the electrolytic plating was an aqueous solution of cobalt sulfamate (150 g / L) and iron sulfamate (300 g / L). By making the same as Sample 6 except for the above bath composition, a porous body (Celmet) having a skeleton body of CoFe ₂ O ₄ was obtained.

<Sample 10>
A porous body in which the main body of the skeleton is MgMn ₂ O ₄ by the same method (dipping method) as <Sample 1 to Sample 5> except that the powder of MgMn ₂ O ₄ is used as the powder of the metal oxide as the raw material. Obtained (Celmet).

<Sample 11>
The bath composition used in electrolytic plating was an aqueous solution of nickel sulfamate (450 g / L). By making the same as Sample 6 except that the bath composition and the oxidation treatment were not performed, a porous body (Celmet) having a skeleton body of Ni was obtained.

<Sample 12 and Sample 13>
As sample 12, stainless steel 430 mesh (linear 0.1 mm, 100 mesh) was used. Further, as sample 13, an iron-chromium alloy mesh (manufactured by Magnex, linear 0.1 mm, 70 mesh) was used.

By the above procedure, the porous bodies of Samples 1 to 11 and the metal meshes of Samples 12 and 13 were obtained. Here, Samples 1 to 9 correspond to Examples, and Samples 10 to 13 correspond to Comparative Examples.

≪Performance evaluation of porous body≫
<Analysis of physical properties of porous body>
With respect to the porous bodies of Samples 1 to 11 obtained by the above method, the mass ratios and molar ratios of the constituent elements in the main body of these skeletons are determined by the EDX device (SEM part: trade name "SUPRA35VP") attached to the SEM, respectively. Investigated using Carl Zeiss Microscopy Co., Ltd., EDX part: trade name "octane super", manufactured by Ametec Co., Ltd.). Specifically, first, the porous body of each sample was cut. Next, the cross section of the skeleton body of the cut porous body was observed by the above EDX device, and the mass ratio of the constituent elements and the composition of the porous body were determined based on the atomic concentration of each detected element. As a result, it was found that the porous bodies of Samples 1 to 11 had the compositions shown in Table 1.

Further, for the porous bodies of Samples 1 to 11, the average pore diameter and porosity of the skeleton were determined according to the above calculation formula. As a result, it was consistent with the porosity and the average pore diameter of the resin molded product, the porosity was 96%, and the average pore diameter was 450 μm. Further, the porous bodies of Samples 1 to 11 had a thickness of 1.5 mm. In the porous bodies of Samples 1 to 11, the total basis weight of the metal oxide or metal was 600 g / m ² .

<Power generation evaluation>
Further, using the porous bodies of Samples 1 to 11 and the metal meshes of Samples 12 and 13 as current collectors for the air electrode, a fuel cell (FIG. 8) was produced together with a YSZ cell (FIG. 9) manufactured by Elkogen. Power generation was evaluated using the following evaluation items.

(Evaluation of electrical resistivity)
In order to evaluate the conductivity in a high temperature environment, the electrical resistivity of the porous bodies of Samples 1 to 11 and the metal meshes of Samples 12 and 13 was measured by the following method.

Specifically, the porous bodies of Samples 1 to 11 and the metal meshes of Samples 12 and 13 are continuously heat-treated at 800 ° C. in an air atmosphere, and before heat treatment using the four-terminal method ( The electrical resistivity (unit: Ω · cm ² ) at the time when the heat treatment was continued for a predetermined time (1000 hours) was measured. The measurement direction of the electrical resistivity is the thickness direction of the porous body or the metal mesh. The results are shown in Table 1.

(Evaluation of operating voltage maintenance rate after 1000 hours of power generation)
For the produced fuel cell, the initial operating voltage V1 and the operating voltage V2 after 1000 hours were determined. The operating voltages V1 and V2 were measured three times and the results were averaged to obtain the respective operating voltages. From the obtained V1 and V2, the operating voltage retention rate after 1000 hours was obtained by the following formula. The results are shown in Table 1 below.
Operating voltage maintenance rate (%) = (V2 / V1) x 100 after 1000 hours of power generation

<Discussion>
According to Table 1, the porous bodies of Samples 1 to 9 containing at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements in the main body of the skeleton are collected for the air electrode. In the fuel cell included as an electric body, the electrical resistivity at 800 ° C. was 0.44 to 1.78 Ω · cm ² , and the operating voltage retention rate after 1000 hours was 90 to 98%. Further, from the above results, the porous body of the metal oxide containing at least two kinds of metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements is a current collector for the air electrode of the fuel cell. Alternatively, it was found that even when used as a current collector for hydrogen poles, the electrical resistance is low and the decrease in operating voltage due to long-term use is suppressed.

On the other hand, in the fuel cell in which the porous body of the sample 10 containing MgMn ₂ O ₄ is contained as the current collector for the air electrode in the main body of the skeleton, the electrical resistivity is more than 10Ω · cm ² and the operating voltage is maintained after 1000 hours. The rate was too low to measure. In a fuel cell containing a porous body of sample 11 containing Ni in the main body of the skeleton as a current collector for the air electrode, the electrical resistivity is more than 10 Ω · cm ² and the operating voltage retention rate after 1000 hours is too low. It was impossible to measure. Further, in the fuel cell containing the stainless steel 430 mesh of the sample 12 as the current collector for the air electrode, the electrical resistivity is 0.33 Ω · cm ² , but the operating voltage retention rate after 1000 hours is reduced to 63%. Was. In the fuel cell containing the iron-chromium alloy mesh of sample 13 as a current collector for the air electrode, the electrical resistance is 0.80 Ω · cm ² , but the operating voltage retention rate after 1000 hours drops to 72%. Was.

Considering the above points, the porous body of Samples 1 to 9 containing at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements in the main body of the skeleton is Sample 10. And, compared to the porous body of sample 11, even when used as a current collector for an air electrode or a current collector for a hydrogen electrode of a fuel cell, the electric resistance is low and the decrease in operating voltage due to long-term use is suppressed. It turned out to be a porous body.
Further, since the porous bodies of Samples 1 to 9 do not contain chromium as a constituent element, they do not volatilize like chromium oxides and cause deterioration of fuel cell performance. From this point of view, it was found that the porous bodies of Samples 1 to 9 are suitable for the current collector for the air electrode or the current collector for the hydrogen electrode of the fuel cell.

Although the embodiments and examples of the present invention have been described as described above, it is planned from the beginning that the configurations of the above-described embodiments and examples are appropriately combined.

It should be considered that the embodiments and examples disclosed this time are examples in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims rather than the embodiments and examples described above, and is intended to include meaning equivalent to the scope of claims and all modifications within the scope.

1 strut part, 2 node part, 10 frame part, 11 skeleton body, 12 skeleton, 13 inside, 14 pores, 20 cell part, 30 three-dimensional network structure, 100 fuel cell cell, 102 air electrode, 104 intermediate layer , 106 Electrolyte layer, 108 hydrogen electrode, 110 hydrogen electrode current collector, 112 first interconnector, 114 fuel flow path, 120 air electrode current collector, 122 second interconnector, 124 oxidant flow path, 150 fuel Battery, 200 cell for steam electrolyzer, 202 air electrode, 204 intermediate layer, 206 electrolyte layer, 208 hydrogen electrode, 210 hydrogen electrode current collector, 212 first interconnector, 214 hydrogen flow path, 220 air electrode current collector Body, 222 second interconnector, 224 steam flow path, 250 steam electrolyzer, A virtual plane

Claims (15)

1. A porous body having a skeleton having a three-dimensional network structure.
   The main body of the skeleton is a porous body containing at least two metal elements selected from the group consisting of nickel, manganese, cobalt, iron and copper as constituent elements.
2. The body of the skeleton
   When nickel is contained as a constituent element, cobalt is not contained and
   The porous body according to claim 1, wherein when cobalt is contained as a constituent element, nickel is not contained.
3. The porous body according to claim 1 or 2, wherein the main body of the skeleton further contains oxygen as a constituent element.
4. The porous body according to claim 3, wherein the oxygen is contained in the main body of the skeleton in an amount of 0.1% by mass or more and 40% by mass or less.
5. The main body of the skeleton has the general formula (1):
   A _x Z _3-x O ₄ (1)
   Contains the metal oxides indicated by
   In formula (1), A represents a metal element selected from the group consisting of nickel, manganese, cobalt, iron and copper, and Z represents a metal element selected from the group consisting of nickel, manganese, cobalt, iron and copper. The porous body according to claim 3 or 4, wherein x is 1 or more and 2 or less.
6. The porous body according to claim 5, wherein the metal oxide contains at least one selected from the group consisting of MnNi ₂ O ₄ , MnCo ₂ O ₄ , CuNi ₂ O ₄ and FeCo ₂ O ₄ .
7. The porous body according to claim 5 or 6, wherein the main body of the skeleton contains a spinel-type oxide.
8. The porous body according to any one of claims 1 to 7, wherein the main body of the skeleton does not contain chromium as a constituent element.
9. The porous body according to any one of claims 1 to 8, wherein the skeleton has a basis weight of 200 g / m ² or more and 1000 g / m ² or less.
10. The porous body according to any one of claims 1 to 9, wherein the skeleton has an electrical resistivity of 2 Ω · cm ² or less at 800 ° C.
11. When an observation image is obtained by observing the cross section of the main body of the skeleton at a magnification of 3000 times, the number of voids having a major axis of 1 μm or more appearing in an arbitrary 10 μm square region of the observation image is 5 or less. , The porous body according to any one of claims 1 to 10.
12. The porous body according to any one of claims 1 to 11, wherein the skeleton is hollow.
13. The porous body according to any one of claims 1 to 12, wherein the porous body has a sheet-like appearance and a thickness of 0.2 mm or more and 2 mm or less.
14. A fuel cell including a current collector for an air electrode and a current collector for a hydrogen electrode.
    A fuel cell comprising the porous body according to any one of claims 1 to 13, at least one of the current collector for an air electrode and the current collector for a hydrogen electrode.
15. A steam electrolyzer equipped with a current collector for an air electrode and a current collector for a hydrogen electrode.
    A steam electrolyzer comprising the porous body according to any one of claims 1 to 13, wherein at least one of the current collector for an air electrode and the current collector for a hydrogen electrode is included.

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