阅读说明：本技术 氧化物分散金属多孔体、电解电极以及氢制造装置 (Porous oxide-dispersed metal body, electrolytic electrode, and hydrogen production device ) 是由 奥野一树 真岛正利 东野孝浩 俵山博匡 光岛重德 于 2018-04-23 设计创作，主要内容包括：本发明提供了一种氧化物分散金属多孔体,该氧化物分散金属多孔体包括多孔金属骨架和担载在金属骨架中的氧化物颗粒。(The present invention provides an oxide-dispersed metal porous body including a porous metal skeleton and oxide particles supported in the metal skeleton.)

1. An oxide-dispersed metal porous body includes a porous metal skeleton and oxide particles supported in the metal skeleton.

2. The oxide-dispersed metal porous body according to claim 1, wherein the metal skeleton has a three-dimensional network structure.

3. The oxide-dispersed metal porous body according to claim 1 or 2, wherein the porosity of the oxide-dispersed metal porous body is 70 vol% or more.

4. The oxide-dispersed metal porous body according to any one of claims 1 to 3, wherein the opening diameter of the oxide-dispersed metal porous body is from 100 μm to 2000 μm.

5. The oxide-dispersed metal porous body according to any one of claims 1 to 4, wherein the oxide particles are non-uniformly supported in a surface layer portion of the metal skeleton.

6. The oxide-dispersed metal porous body according to any one of claims 1 to 5, wherein the average particle diameter of the oxide particles is 0.1 μm or more and 10 μm or less.

7. The oxide-dispersed metal porous body according to any one of claims 1 to 6, wherein the appearance of the oxide-dispersed metal porous body is a shape in a sheet form, and the mass per unit area of the shape is from 200g/m2 to 1500g/m 2.

8. The oxide-dispersed metal porous body according to any one of claims 1 to 7, wherein the appearance of the oxide-dispersed metal porous body is a shape in a sheet form, and the amount of the oxide particles supported per unit area of the shape is 10g/m2 to 100g/m 2.

9. The oxide-dispersed metal porous body according to any one of claims 1 to 8, wherein the appearance of the oxide-dispersed metal porous body is a shape in a sheet form, and the thickness of the shape is 0.1mm to 10 mm.

10. the oxide-dispersed metal porous body according to any one of claims 1 to 9, wherein each of the oxide particles comprises at least one selected from the group consisting of iron oxide, nickel oxide, chromium oxide, titanium oxide, aluminum oxide, zirconium oxide, cerium oxide, cobalt oxide, molybdenum oxide, ruthenium oxide, iridium oxide, tin oxide, and silicon oxide.

11. An electrolytic electrode comprising the oxide-dispersed metal porous body as recited in any one of claims 1 to 10.

12. A hydrogen production apparatus comprising:

An electrolytic cell configured to store an alkaline aqueous solution;

An anode and a cathode each immersed in the aqueous alkaline solution; and

A power supply configured to apply a voltage between the anode and the cathode, wherein

At least one of the anode and the cathode is an electrolytic electrode as recited in claim 11.

13. A hydrogen production apparatus comprising:

An anode;

A cathode;

an electrolyte membrane disposed between the anode and the cathode; and

a power supply configured to apply a voltage between the anode and the cathode, wherein

at least one of the anode and the cathode is an electrolytic electrode as recited in claim 11.

Technical Field

The invention relates to an oxide-dispersed metal porous body, an electrolytic electrode, and a hydrogen production apparatus. The present application claims priority based on japanese patent application No.2017-085698, filed 24.4.2017, the entire contents of which are incorporated herein by reference.

Background

Hydrogen is suitable for storage and transport and also has a small environmental load. Therefore, hydrogen is receiving attention as a highly efficient clean energy source. Most of the hydrogen is produced by steam reforming of fossil fuels. However, to reduce the environmental load, the production of hydrogen by water electrolysis is becoming more and more important. Since water electrolysis involves consumption of electric power, various improvements of electrolytic electrodes have also been attempted to realize a high-efficiency hydrogen production system (see japanese patent laid-open publication No.2016-148074 (patent document 1), japanese patent laid-open publication No.2016-204732 (patent document 2), japanese patent laid-open publication No.2017-057470 (patent document 3), and WO2015/064644 (patent document 4)).

For example, a hydrogen production apparatus, the apparatus comprising: a laminate in which a separator is sandwiched between a pair of electrodes; and an electrolytic cell configured to store the laminated body therein. As the structure of the laminated body, a zero-gap structure in which the separator is in contact with the electrode is generally employed. A rib structure may be provided on the surface of each electrode that is not in contact with the separator to ensure a space for releasing bubbles. When a plurality of electrodes are used, a bipolar type involving a series connection is generally employed.

CITATION LIST

Patent document

PTL 1: japanese patent unexamined publication No.2016-148074

PTL 2: japanese patent unexamined publication No.2016-204732

PTL 3: japanese patent unexamined publication No.2017-057470

PTL4：WO2015/064644

Disclosure of Invention

One aspect of the present invention relates to an oxide-dispersed metal porous body including a porous metal skeleton and oxide particles supported in the metal skeleton.

Another aspect of the present invention relates to an electrolytic electrode comprising the above oxide-dispersed metal porous body.

Yet another aspect of the present invention relates to a hydrogen production apparatus, including: an electrolytic cell configured to store an alkaline aqueous solution; an anode and a cathode each immersed in an alkaline aqueous solution; and a power supply configured to apply a voltage between the anode and the cathode, wherein at least one of the anode and the cathode is the above-described electrolysis electrode.

Yet another aspect of the present invention relates to a hydrogen production apparatus, including: an anode; a cathode; an electrolyte membrane disposed between the anode and the cathode; and a power supply configured to apply a voltage between the anode and the cathode, wherein at least one of the anode and the cathode is the above-described electrolysis electrode.

Drawings

Fig. 1 is a schematic diagram showing an exemplary structure of a part of the skeleton of the oxide-dispersed metal porous body.

Fig. 2 is a sectional view schematically showing a section of a part of the skeleton in fig. 1.

Fig. 3 is a schematic diagram showing an exemplary basic structure of a hydrogen production apparatus.

Fig. 4 shows a photograph representing an exemplary metallic porous body substrate having a three-dimensional network structure.

fig. 5 shows an SEM photograph showing an exemplary metallic porous body substrate having a three-dimensional network structure.

Detailed Description

[ problem to be solved by the present disclosure ]

the electrolytic electrode proposed for general water electrolysis has a two-dimensional structure and a small surface area. Therefore, improvement of the efficiency of water electrolysis is limited. It is also contemplated to use porous bodies having a two-dimensional structure, such as expanded metal or stamped metal. However, gas generated by water decomposition remains in the pores of the porous body having a two-dimensional structure, so that the effective surface area for promoting the electrolytic reaction is easily reduced.

[ advantageous effects of the present disclosure ]

According to the oxide-dispersed metal porous body of the present invention, an electrolytic electrode having excellent hydrophilicity and excellent hydrogen production ability and a hydrogen production apparatus including the electrolytic electrode can be provided.

[ description of the embodiments ]

first, the contents of the embodiments of the present invention are enumerated and described.

(1) An oxide-dispersed metal porous body according to an embodiment of the present invention includes a porous metal skeleton and oxide particles supported in the metal skeleton. Since the oxide particles are supported in the metal skeleton, the hydrophilicity of the metal porous body is improved. During water electrolysis, water easily permeates the oxide-dispersed metal porous body, and bubbles of gas such as hydrogen, oxygen, and the like generated by water electrolysis are easily released from the fine pores (for example, the openings 103, the pores 101, and the like described below) of the oxide-dispersed metal porous body. Therefore, the surface area of the metal skeleton can be effectively utilized for the electrolytic reaction, thereby improving the efficiency of water electrolysis.

(2) The porous metal skeleton preferably has a three-dimensional network structure. Therefore, the surface area of the oxide-dispersed porous metal body or the electrolytic electrode comprising the porous metal body is significantly increased. Although the volume of the pores is large in such a metal porous body, gas is easily released from the pores.

(3) The porosity of the oxide-dispersed metal porous body is preferably 70 vol% or more. Therefore, the surface area of the metallic porous body or the electrolytic electrode comprising the metallic porous body is further significantly increased.

(4) The opening diameter of the oxide-dispersed metal porous body is preferably 100 μm to 2000 μm. Therefore, the gas is more easily released from the fine pores.

(5) The oxide particles are preferably unevenly supported on the surface layer portion of the metal skeleton. Therefore, the hydrophilicity of the oxide-dispersed metal porous body is further improved. For example, the oxide particles may be contained in a plating layer that covers at least a part of the surface of the metal skeleton.

(6) The average particle diameter of the oxide particles is preferably 0.1 μm or more and 10 μm or less. This is because the oxide particles are easily mixed or supported in the metal skeleton.

(7) The mass per unit area of the oxide-dispersed metal porous body is preferably 200g/m2 to 1500g/m2, and more preferably 600g/m2 to 1500g/m 2. That is, the external appearance of the oxide-dispersed metal porous body is a shape of a sheet form, and the mass per unit area of the shape is preferably 200g/m2 to 1500g/m2, and more preferably 600g/m2 to 1500g/m 2. This is because a light-weight oxide-dispersed metal porous body having high strength and a large surface area or an electrolytic electrode comprising the metal porous body can be obtained.

It should be noted that the unit area of the oxide-dispersed metal porous body refers to a unit area of a projected area of the oxide-dispersed metal porous body when the oxide-dispersed metal porous body having a shape in a sheet form is viewed from a normal direction of a main surface thereof (the same applies to the following description).

(8) The amount of the oxide particles supported per unit area of the oxide-dispersed metal porous body is preferably 10g/m2 to 100g/m2, and more preferably 15g/m2 to 50g/m 2. That is, the external appearance of the oxide-dispersed metal porous body is a shape of a sheet form, and the amount of oxide particles supported per unit area of the shape is preferably 10g/m2 to 100g/m2, and more preferably 15g/m2 to 50g/m 2. This is because the balance between the effect of improving hydrophilicity and the area of the electrode for promoting the electrolytic reaction is improved. For example, the amount of the oxide particles supported per unit area can be determined from the weight of the unmelted oxide residue remaining after the porous metal body is melted using the acid.

(9) The thickness T of the oxide-dispersed metal porous body is preferably 0.1mm to 10mm, more preferably 0.3mm to 5mm, and further preferably 1.4mm to 5 mm. That is, the external appearance of the oxide-dispersed metal porous body is a shape of a sheet form, and the thickness of the shape is preferably 0.1mm to 10mm, more preferably 0.3mm to 5mm, and further preferably 1.4mm to 5 mm. This is because it is easy to ensure high porosity and also to promote the release of gas from the fine pores. Further, a hydrogen production apparatus having high volumetric efficiency can be designed. It should be noted that the thickness T is, for example, an average value of the thicknesses at arbitrary ten positions of the oxide-dispersed metal porous body. For example, the thickness can be measured using a digital thickness gauge.

(10) The oxide particles can be any inorganic oxide particles. For example, at least one selected from the group consisting of iron oxide, nickel oxide, chromium oxide, titanium oxide, aluminum oxide, zirconium oxide, cerium oxide, cobalt oxide, molybdenum oxide, ruthenium oxide, iridium oxide, tin oxide, and silicon oxide may be used. As long as the oxide is stable during electrolysis, the valence state of the oxide is not interrogated. This is because these oxides are not easily reduced during electrolysis and have high stability. Among them, chromium oxide, titanium oxide, aluminum oxide, zirconium oxide, and cerium oxide are less prone to reduction. One type of oxide particles may be used alone, or a plurality of types of oxide particles may be used in combination.

In another embodiment of the present invention, each oxide particle preferably includes at least one selected from the group consisting of iron oxide, nickel oxide, chromium oxide, titanium oxide, aluminum oxide, zirconium oxide, cerium oxide, cobalt oxide, molybdenum oxide, ruthenium oxide, iridium oxide, tin oxide, and silicon oxide. Further, the above oxide particles more preferably include at least one selected from the group consisting of chromium oxide, titanium oxide, aluminum oxide, zirconium oxide, and cerium oxide.

(11) An electrolytic electrode according to an embodiment of the present invention includes the above-described oxide-dispersed metal porous body. Therefore, a high hydrogen production capacity can be exhibited in water electrolysis.

(12) A hydrogen production apparatus according to an embodiment of the present invention includes: an electrolytic cell configured to store an alkaline aqueous solution; an anode and a cathode each immersed in an alkaline aqueous solution in the electrolytic bath; and a power supply configured to apply a voltage between the anode and the cathode, wherein at least one of the anode and the cathode is the above-described electrolysis electrode. According to the hydrogen production apparatus, hydrogen can be efficiently produced.

(13) A hydrogen production apparatus according to an embodiment of the present invention includes: an anode; a cathode; an electrolyte membrane disposed between the anode and the cathode; and a power supply configured to apply a voltage between the anode and the cathode, wherein at least one of the anode and the cathode is the above-described electrolysis electrode. According to the hydrogen production apparatus, hydrogen can be efficiently produced. The electrolyte membrane may be a polymer electrolyte membrane or may be a solid oxide electrolyte membrane.

[ detailed description of embodiments of the invention ]

Embodiments of the present invention will be specifically described below. It should be noted that the present invention is defined by the claims, not by the following, and is intended to include any modifications within the scope and meaning equivalent to the claims. Here, in the present specification, the expression "a to B" represents the lower limit to the upper limit of the range (i.e., a to B). When no unit is described after a and only a unit is described after B, the unit of a is the same as that of B.

Hereinafter, description will be made with reference to fig. 1 to 3. Fig. 1 is a schematic diagram showing an exemplary structure of a part of the skeleton of the oxide-dispersed metal porous body. Fig. 2 is a sectional view schematically showing a section of a part of the skeleton in fig. 1. Fig. 3 is a schematic diagram showing an exemplary basic structure of a hydrogen production apparatus. It should be noted that in each figure, the oxide particles are not shown.

(porous Metal oxide Dispersion)

For example, the oxide-dispersed porous metal body includes a porous metal body base and a plating layer formed on a surface of the porous metal body base. As used herein, the term "metallic porous substrate" refers to a substrate comprising a metal skeleton. The metal skeleton defines a two-dimensional hole (for example, an opening described below) or a three-dimensional space (for example, an air hole described below). The plating layer contains dispersed oxide particles. In this case, the oxide particles are unevenly supported on the surface layer portion of the metal skeleton (for example, the fiber portion 102 described below). That is, it is understood that the oxide particles are carried in the metal skeleton as a part of the plating layer. Further, the above oxide particles may be supported on the surface of the plating layer. For example, a plating layer containing dispersed oxide particles (hereinafter, referred to as "oxide dispersion plating layer") can be formed by the following method.

First, a plating bath in which oxide particles are dispersed is prepared. The plating bath is preferably stirred to sufficiently disperse the oxide particles. For example, when a nickel plating layer is formed, a general plating bath containing nickel sulfamate may be used as the plating bath. The plating bath is preferably stirred so that the liquid flow impinges on the surface of the porous metal body substrate.

the amount of the oxide particles added to the plating bath is preferably 50g/L to 500g/L, more preferably 100g/L to 300g/L, and further preferably 200g/L to 300 g/L. Therefore, the oxide dispersion plating layer in which a sufficient amount of oxide particles is mixed can be formed, and clogging of the pores of the metal porous body base material with an excessive amount of oxide particles can be sufficiently avoided.

The average particle diameter of the oxide particles on a volume basis obtained from the laser diffraction type particle diameter distribution is preferably 0.1 μm or more and 10 μm or less, more preferably 0.1 μm or more and 3 μm or less, and further preferably 0.1 μm or more and 1 μm or less. That is, the average particle diameter of the oxide particles is preferably 0.1 μm or more and 10 μm or less, more preferably 0.1 μm or more and 3 μm or less, and further preferably 0.1 μm or more and 1 μm or less. When the average particle diameter falls within this range, precipitation caused by agglomeration of oxide particles in the plating solution is easily suppressed, clogging of the fine pores of the metal porous body base material with excessively large oxide particles is also sufficiently avoided, and the oxide particles are easily mixed in the plating layer. The above average particle diameter can be measured, for example, by a laser diffraction type particle size distribution measuring apparatus, particle LA-960 (trade name), supplied from HORIBA. The target powder is mixed with a solvent (such as water), and then dispersed using ultrasonic waves or the like. The appropriate refractive index was set to determine the particle size distribution and the average particle size was calculated.

Then, the metallic porous body base material may be immersed in a plating bath that is being stirred to disperse oxide particles, thereby forming an oxide particle-dispersed plated layer on the surface of the metallic porous body base material. Further, it is preferable to perform the plating treatment while stirring the plating bath. In order to sufficiently secure the amount of the oxide particles supported therein and obtain a lightweight, inexpensive oxide-dispersed metal porous body, the amount of the metal for plating per unit surface area (the amount of the oxide particle-dispersed plating layer) of the metal porous body base material is preferably 100g/m2 to 700g/m2, more preferably 150g/m2 to 400g/m2, and further preferably 150g/m2 to 300g/m 2. The amount of metal used for plating is determined by the following formula: { (mass (g) of the oxide-dispersed porous metal body after the plating treatment)) - (mass (g) of the porous metal body base material before the plating treatment) }/(surface area (m2) of the porous metal body base material before the plating treatment).

As the metal porous body substrate, a mesh, an expanded metal, a pressed metal, a metal porous body having a three-dimensional mesh structure, or the like can be used. Among them, a metal porous body having a three-dimensional network structure is preferably used as the metal porous body substrate because the electrode surface can be made large. The material of the metallic porous body base material may be any material as long as the material is stable in the electrolyte solution. Examples of materials include nickel or nickel alloys, aluminum or aluminum alloys, stainless steel, iron, and the like. As the material of the metal porous body base material, stainless steel, iron, nickel, and the like are preferable. Nickel having a wide stable potential range in alkali is particularly preferred.

The oxide-dispersed metal porous body comprising a metal porous body substrate having a three-dimensional network structure is further illustratively described below.

The three-dimensional mesh skeleton is, for example, a metal skeleton having a nonwoven fabric-like structure or a sponge-like structure, and has a plurality of pores defined by the skeleton. In another aspect of this embodiment, it is also understood that the three-dimensional reticulated framework has a plurality of pores 101 defined by the fibrous portions 102 described below. Such a metal skeleton and the pores surrounded by the skeleton constitute one cell (cell). The appearance of the metal porous body base material may be in a shape such as a sheet, a cube, a sphere, or a cylinder. Further, the external appearance of the oxide-dispersed metal porous body may be in a shape such as a sheet, a cube, a sphere, or a cylinder.

As shown in fig. 1, for example, one cell can be represented as a regular dodecahedron model. The pores 101 are defined by metal portions (fiber portions 102) in a fiber or rod shape. The plurality of air holes 101 are three-dimensionally connected (not shown). The skeleton of the cell is formed by the continuously extending fiber portions 102. In the cell, a substantially pentagonal opening (or window) 103 is formed surrounded by the fiber portion 102. Adjacent cells communicate with each other, sharing one opening 103 between adjacent cells. That is, the skeleton of the metallic porous body is formed by the fiber part 102, and the fiber part 102 forms a mesh network while defining a plurality of continuous pores 101. A skeleton having such a structure is called a "three-dimensional network skeleton".

As shown in fig. 2, a cavity 102a may be provided in the fiber part 102, i.e., the fiber part 102 may be hollow. The porous metal body having such a hollow skeleton has a bulky three-dimensional structure, but is extremely lightweight. It should be noted that, although not shown in the drawings, the fiber part 102 of the oxide-dispersed metallic porous body has a two-layer structure including the metallic skeleton of the metallic porous body base material and the oxide-dispersed plated layer. Further, the oxide dispersion plating layer should be formed at least on the surface of the metal skeleton opposite to the surface thereof facing the cavity 102 a.

The metal porous body base material can be formed by, for example, coating a porous body composed of a resin having through-holes (hereinafter, also referred to as "resin porous body") with a metal. For example, coating with a metal can be performed by a plating method, a vapor phase method (vapor deposition, plasma chemical vapor deposition, sputtering, or the like), application of a metal paste, or the like. Due to the coating with metal, a three-dimensional network skeleton is formed. Among the above methods, the plating method is preferably used for coating with a metal.

as the plating method, any method may be employed as long as a metal layer can be formed on the surface of the porous resin body (including the surface thereof on the internal space side) by the method. As the plating method, a known plating method, such as an electroplating method or a molten salt plating method, may be employed. By the plating method, a three-dimensional porous metal mesh corresponding to the shape of the porous resin body is formed. That is, the opening diameter and pore diameter (cell diameter) of the obtained metal porous body can be controlled according to the pore diameter (cell diameter) of the resin porous body.

When the plating treatment is performed using the electroplating method, it is desirable to form a conductive layer on the surface of the resin porous body before the electroplating. The conductive layer may be formed on the surface of the porous resin body by electroless plating, vapor deposition, sputtering, or the like, may be formed on the surface of the porous resin body by coating a conductive agent or the like, or may be formed on the surface of the porous resin body by dipping the porous resin body into a dispersion containing a conductive agent.

The porous resin body is not particularly limited as long as the porous resin body has communicating pores. Resin foams, nonwoven fabrics made of resins, and the like can be used for the porous resin bodies. Among them, the resin foam is preferable because the communicating pores are easily formed in the metal porous body. As the resin used for the porous body such as the resin foam, it is preferable to employ a resin which can be removed by decomposition or melting while leaving a metal skeleton having a three-dimensional network structure after metal coating. In this case, the skeleton (fiber part) 102 may be hollow. Examples of the resin include: thermosetting resins such as thermosetting polyurethane and melamine resins; thermoplastic resins such as olefin resins (polyethylene, polypropylene, etc.) and thermoplastic polyurethanes; and the like. Among them, thermosetting polyurethane or the like is preferably used because pores having a more uniform size or shape are easily formed.

After the resin in the skeleton is removed by decomposition or melting, the components (resin, decomposed material, unreacted monomer, etc.) remaining in the skeleton can be removed by washing. The resin can be removed by heating while applying a voltage as appropriate as necessary. Further, the plated porous body may be heated while applying a voltage in a state of being immersed in a molten salt plating bath. After the metal coating, the resin was removed in this manner, and a metal porous body substrate in which a cavity was formed inside the skeleton was obtained. The metal porous body base material has a three-dimensional network structure corresponding to the shape of the resin foam. It should be noted that examples of commercially available metallic porous body substrates include both copper or nickel, which are provided by sumitomo electrical industries co (fig. 4 and 5).

When the external appearance of the metallic porous body substrate is a shape in the form of a sheet, the mass per unit area of the shape is preferably 200g/m2 to 1000g/m2, and more preferably 300g/m2 to 500g/m 2.

The average pore diameter of the porous metal substrate is not particularly limited. For example, the average pore diameter in the porous metal body substrate may be 100 μm to 4000 μm, may be 100 μm to 3000 μm, may be 200 μm to 1000 μm, or may be 500 μm to 1000 μm. The above average pore diameter can be determined by the same method as that used for determining the diameter (average pore diameter) of the pores 101 in the oxide-dispersed metal porous body described below.

Then, the opening diameter D of the oxide-dispersed metal porous body is determined, for example, as follows. First, any one of the openings 103a is selected from the openings 103 of the oxide-dispersed metal porous body. The diameter Dp of the largest perfect circle C (see fig. 2) contained in the selected opening 103a and the diameter of the smallest perfect circle that can contain the opening 103a are measured, and then the average values thereof are determined. This average value is regarded as the opening diameter Da of the opening 103 a. Likewise, the respective opening diameters Db to Dj of a plurality of (for example, nine) arbitrary other openings 103b to 103j of the oxide-dispersed metal porous body are determined. The average value of the respective opening diameters Da to Dj of the ten openings 103a to 103j is regarded as the opening diameter D.

Specifically, in an SEM photograph of the main surface of the oxide-dispersed metal porous body, a region R including ten or more openings 103 as a whole is determined. For example, ten openings 103 are randomly selected from among the openings 103 included in the region R, and the respective opening diameters Da to Dj of the openings 103a to 103j are calculated by the above-described method. The calculated average value of the opening diameters Da to Dj of the openings 103a to 103j is regarded as the opening diameter D.

The opening diameter D of the oxide-dispersed metal porous body is preferably 100 to 2000 μm, and more preferably 400 to 1000 μm. That is, the opening diameter of the oxide-dispersed metal porous body is preferably 100 μm to 2000 μm, and more preferably 400 μm to 1000 μm. The opening diameter D can be determined, for example, by the following method. In the SEM photograph of the main surface of the oxide-dispersed metal porous body, openings suitable for measurement were selected, the opening diameters at ten or more positions were measured, and the average value thereof was determined, thereby determining the opening diameter D.

Although the porosity P of the oxide-dispersed metal porous body is not particularly limited, the porosity P is preferably 70 vol% or more, more preferably 80 vol% or more, and particularly preferably 85 vol% or more, in order to improve the release of gas. That is, the porosity of the oxide-dispersed metal porous body is preferably 70 vol% or more, more preferably 80 vol% or more, and particularly preferably 85 vol% or more. The porosity P is less than 100% by volume, may be 99.5% by volume or less, or may be 99% by volume or less. These lower and upper limit values may be combined as appropriate. The porosity (% by volume) is determined by the following formula: {1- (apparent specific gravity of metal porous body/actual specific gravity of metal) } × 100.

The diameter (also referred to as "cell diameter" or "average pore diameter") V1 of the pores 101 in the oxide-dispersed metal porous body is not particularly limited. For example, the pore diameter V1 may be 100 μm to 4000 μm, may be 200 μm to 1000 μm, or may be 500 μm to 1000 μm. For example, the vent diameter V1 is determined as follows. First, any one of the pores 101a is selected from the pores 101 of the oxide-dispersed metal porous body. The diameter of the largest sphere included in the selected air holes 101a and the diameter of the smallest sphere S (see fig. 1) that can include the air holes 101a are measured, and then the average values thereof are determined. This average value is regarded as the pore diameter Va of the pores 101 a. Also, the pore diameters Vb to Vj of each of a plurality of (for example, nine) any other pores 101b to 101j that are present in the oxide-dispersed metal porous body are determined. The average value of the pore diameters Va to Vj of the ten pores 101a to 101j is regarded as the pore diameter V1.

Specifically, in the SEM photograph of the main surface of the oxide-dispersed metal porous body, a region V including ten or more pores 101 as a whole was identified. For example, ten air holes 101 are randomly selected from the air holes 101 included in the region V, and the respective air hole diameters Va to Vj of the air holes 101a to 101j are calculated by the above-described method. The average value of the calculated pore diameters Va to Vj of the pores 101a to 101j is regarded as the pore diameter V1.

The vent diameter (cell diameter) V1 of the present invention refers to a value measured in the direction in which V1 is largest when the shape of each vent is not true sphere and has a specific aspect ratio.

The specific surface area (BET specific surface area) of the oxide-dispersed metal porous body is also not particularly limited. The specific surface area of the metallic porous body may be, for example, 100m2/m3 to 9000m2/m3, or may be 200m2/m3 to 6000m2/m 3.

The density d of the openings 103 of the oxide-dispersed metal porous body is also not particularly limited. In particular, the density d is preferably 10/2.54cm to 100/2.54cm, and more preferably 30/2.54cm to 80/2.54cm for the electrical resistance. It should be noted that the density d refers to the number of openings 103 on a straight line when a straight line having a length of 1 inch (═ 2.54cm) is drawn on the surface of the oxide-dispersed metal porous body. Here, when the straight line ends in the opening located at the end of the straight line, the opening is not counted.

The width Wf of the skeleton (fiber portion) 102 of the oxide-dispersed metal porous body is also not particularly limited. In particular, the width Wf is preferably 3 μm to 500 μm, and more preferably 10 μm to 500 μm for the current collection property.

Next, a hydrogen production apparatus including the oxide-dispersed metal porous body as an electrolysis electrode will be described below.

The hydrogen production method is roughly divided into: [1] alkaline water electrolysis using an alkaline aqueous solution; [2] PEM method (polymer electrolyte membrane method); and [3] SOEC method (solid oxide electrolytic cell method). In each method, the above-described metal porous body can be used as an electrolytic electrode (hereinafter, also simply referred to as "electrode").

[1] Alkaline water electrolysis

In the alkaline water electrolysis method, an anode and a cathode are immersed in an alkaline aqueous solution (preferably a strongly alkaline aqueous solution) and a voltage is applied between the anode and the cathode, thereby electrolyzing water. In this case, the above-described electrode may be used for at least one of the electrodes. At the anode, the hydroxide ions are oxidized to produce oxygen and water. At the cathode, the hydrogen ions are reduced to produce hydrogen. Since the wettability of the electrode to water is large and the surface area is large, the contact area between various ions and the electrode is large, whereby the electrolysis efficiency of water is improved. In addition, since the electrode has excellent conductivity, the electrolysis efficiency of water is further improved. In addition, since the porosity of the electrode is high, the generated hydrogen and oxygen may be immediately released. In order to improve the bubble releasing property, the water retaining property, and the electrical connection, one electrode may be constructed by stacking a plurality of oxide-dispersed metal porous bodies having different pore diameters.

In order to prevent the generated hydrogen and oxygen from mixing, a separator is preferably disposed between the anode and the cathode. The material of the separator is not particularly limited as long as the material has wettability, ion permeability, alkali resistance, non-conductivity, non-gas permeability, thermal stability, and the like. Examples of materials for such separators include: fluorine resin impregnated with potassium titanate; a poly-antimonate; polysulfones; hydrophilized polyphenylene sulfide; polyvinylidene fluoride; polytetrafluoroethylene, and the like. When a plurality of cells each composed of an anode, a cathode, and a separator are used in a stack, it is preferable to dispose a separator (e.g., one of the above) between the cells to prevent short-circuiting.

The dissolved substance of the alkaline aqueous solution is also not particularly limited. Examples include hydroxides of alkali metals (lithium, sodium, potassium, rubidium, cesium or francium) or alkaline earth metals (calcium, strontium, barium or radium), and the like. Among them, a hydroxide of an alkali metal (particularly, NaOH or KOH) is preferable because a strongly alkaline aqueous solution can be obtained. The concentration of the alkaline aqueous solution is also not particularly limited, and may be 20 to 40 mass% from the viewpoint of electrolytic efficiency. The operating temperature is, for example, about 50 ℃ to 90 ℃, and the current density is, for example, about 0.1A/cm2 to 0.3A/cm 2.

[2] PEM method

In the PEM process, water is electrolyzed using a polymer electrolyte membrane. Specifically, in the PEM method, an anode and a cathode are provided on each surface of a polymer electrolyte membrane, water is introduced into the anode, and a voltage is applied between the anode and the cathode, thereby electrolyzing the water. In this case, the above-described electrodes may also be used for at least one of the electrodes. In the PEM method, the anode side and the cathode side are completely separated from each other by a polymer electrolyte membrane as an electrolyte membrane. Therefore, hydrogen of high purity can be conveniently extracted as compared with the alkaline water electrolysis. Further, since the above-mentioned electrode has a large surface area, has a large wettability with water, and has excellent conductivity, the electrode is suitable as an anode of a hydrogen production apparatus (PEM-type hydrogen production apparatus) employing a PEM method.

Here, protons produced by the PEM-type hydrogen production apparatus move to the cathode through the polymer electrolyte membrane, and are extracted as hydrogen at the cathode side. The operating temperature of a PEM-type hydrogen production plant is about 100 ℃. As the polymer electrolyte membrane, a polymer having proton conductivity, such as perfluorosulfonate polymer, which is generally used for a solid polymer fuel cell or a PEM-type hydrogen production device, may be used. In some methods, membranes having anion conductivity can be used. When the cathode includes the above-described electrode, the produced hydrogen can be released immediately.

[3] SOEC process

In the SOEC method (also referred to as "water vapor electrolysis method"), water vapor is electrolyzed using a solid oxide electrolyte membrane. Specifically, in the SOEC method, an anode and a cathode are arranged on respective surfaces of a solid oxide electrolyte membrane, water vapor is introduced into one of the electrodes, and a voltage is applied between the anode and the cathode, thereby electrolyzing the water vapor.

In the SOEC method, an electrode to which water vapor is introduced differs depending on whether the solid oxide electrolyte membrane has proton conductivity or oxide ion conductivity. On the one hand, when the solid oxide electrolyte membrane has oxide ion conductivity, water vapor is introduced to the cathode. The water vapor is electrolyzed at the cathode and protons and oxide ions are generated. The generated protons are reduced at the cathode without modification and extracted as hydrogen. The oxide ions move to the anode through the solid oxide electrolyte membrane, are subsequently oxidized at the anode, and are extracted as oxygen. On the other hand, when the solid oxide electrolyte membrane has proton conductivity, water vapor is introduced into the anode. The water vapor is electrolyzed at the anode and protons and oxide ions are generated. The generated protons move to the cathode through the solid oxide electrolyte membrane, are subsequently reduced at the cathode, and are extracted as hydrogen. The oxide ions are oxidized at the anode without modification and extracted as oxygen.

When the above-mentioned electrode is used as an electrode for introducing water vapor, the electrolysis efficiency of water vapor is improved because the above-mentioned electrode has a large surface area and a large wettability with water, and therefore the contact area between water vapor and the electrode is also large. In addition, since the above-mentioned electrode has excellent conductivity, the electrolysis efficiency of water vapor is further improved.

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The above description includes the features additionally enumerated below.

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An oxide-dispersed metal porous body includes a porous metal skeleton and oxide particles supported in the metal skeleton.

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The porous oxide-dispersed metal body according to note 1, wherein the metal skeleton has a three-dimensional network structure.

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The porous oxide-dispersed metal body according to note 1 or 2, wherein the porous oxide-dispersed metal body has a porosity of 70 vol% or more.

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The porous oxide-dispersed metal body according to any one of notes 1 to 3, wherein the opening diameter of the porous oxide-dispersed metal body is 100 μm to 2000 μm.

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The oxide-dispersed metal porous body according to any one of notes 1 to 4, wherein the oxide particles are non-uniformly supported in a surface layer portion of the metal skeleton.

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the porous oxide-dispersed metal body according to any one of notes 1 to 5, wherein the particle diameter of the oxide particles is 0.1 μm or more and 10 μm or less.

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The porous oxide-dispersed metal body according to any one of notes 1 to 6, wherein the mass per unit area is 200g/m2 to 1500g/m 2.

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The oxide-dispersed metal porous body according to any one of notes 1 to 7, wherein an amount of the oxide particles supported per unit area is 10g/m2 to 100g/m 2.

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The porous oxide-dispersed metal body according to any one of notes 1 to 8, wherein the thickness of the porous oxide-dispersed metal body is 0.1mm to 10 mm.

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The oxide-dispersed metal porous body according to any one of notes 1 to 9, wherein each oxide particle comprises at least one selected from the group consisting of iron oxide, nickel oxide, chromium oxide, titanium oxide, aluminum oxide, zirconium oxide, cerium oxide, cobalt oxide, molybdenum oxide, ruthenium oxide, iridium oxide, tin oxide, and silicon oxide.

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An electrolytic electrode comprising the oxide-dispersed metal porous body described in notes 1 to 10.

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A hydrogen production apparatus comprising:

An electrolytic cell configured to store an alkaline aqueous solution;

An anode and a cathode each immersed in an alkaline aqueous solution; and

A power supply configured to apply a voltage between the anode and the cathode, wherein

At least one of the anode and the cathode is the electrolytic electrode described in reference 11.

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A hydrogen production apparatus comprising:

An anode;

A cathode;

An electrolyte membrane disposed between the anode and the cathode; and

A power supply configured to apply a voltage between the anode and the cathode, wherein

At least one of the anode and the cathode is the electrolytic electrode described in reference 11.