Patent Description:
Hydrogen is suitable for storage and transportation, and also imposes a small environmental load. For this reason, hydrogen is drawing attention as highly efficient clean energy. Most of hydrogen has been generated through steam reforming of a fossil fuel. However, in order to reduce a load on environment, generation of hydrogen through water electrolysis becomes increasingly important. Since the water electrolysis involves consumption of electric power, various improvements of electrolysis electrodes are also attempted in order to realize highly efficient hydrogen generation systems (see <CIT> (Patent Literature <NUM>), <CIT> (Patent Literature <NUM>), <CIT> (Patent Literature <NUM>), and <CIT> (Patent Literature <NUM>)).

For example, a hydrogen generation apparatus includes: a layered body in which a separating membrane is sandwiched between a pair of electrodes; and an electrolyzer configured to store the layered body therein. As a structure of the layered body, a zero gap structure is generally employed in which the separating membrane is in contact with the electrodes. A rib structure may be provided on a surface of each electrode not in contact with the separating membrane so as to secure a space for releasing gas bubbles. When a plurality of electrodes are used, a bipolar type involving series connection is generally employed.

<CIT> (Patent literature <NUM>) and Arthur J. Esswein et al (Non Patent literature <NUM>) disclose oxide-dispersed metal porous bodies comprising a porous metal framework, and oxide particles carried in the metal framework.

One aspect of the present invention is directed to an oxide-dispersed metal porous body including a porous metal framework, and oxide particles carried in the metal framework according to claim <NUM>.

Another aspect of the present invention is directed to an electrolysis electrode including the above-described oxide-dispersed metal porous body according to claim <NUM>.

Still another aspect of the present invention is directed to a hydrogen generation apparatus according to claim <NUM>, including: an electrolyzer configured to store an alkaline aqueous solution; an anode and a cathode each immersed in the alkaline aqueous solution; and a power supply configured to apply 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 is directed to a hydrogen generation apparatus according to claim <NUM>, including: an anode; a cathode; an electrolyte membrane disposed between the anode and the cathode; and a power supply configured to apply voltage between the anode and the cathode, wherein at least one of the anode and the cathode is the above-described electrolysis electrode.

An electrolysis electrode proposed for general water electrolysis has a two-dimensional structure and a small surface area. Accordingly, there is a limit as to improvement of efficiency of the water electrolysis. Use of a porous body having a two-dimensional structure, such as an expanded metal or a punching metal, has been also contemplated. However, gas generated through water splitting remains in fine holes of the porous body having the two-dimensional structure, with the result that an effective surface area for promoting electrolysis reaction is likely to be decreased.

According to the oxide-dispersed metal porous body according to the present invention, there can be provided an electrolysis electrode having excellent hydrophilicity and excellent hydrogen generation ability as well as a hydrogen generation apparatus including the electrolysis electrode.

First, contents of embodiments of the present invention are listed and described.

Embodiments of the present invention will be specifically described below. It should be noted that the present invention is defined by the terms of the claims, rather than the contents below, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. Here, in the present specification, the expression "A to B" represents a range of lower to upper limits (i.e., more than or equal to A and less than or equal to B). When no unit is indicated for A and a unit is indicated only for B, the unit of A is the same as the unit of B.

Hereinafter, explanation will be made with reference to <FIG>. <FIG> is a schematic view showing an exemplary structure of a portion of a framework of an oxide-dispersed metal porous body. <FIG> is a cross sectional view schematically showing a cross section of the portion of the framework in <FIG>. <FIG> is a schematic view illustrating an exemplary basic structure of a hydrogen generation apparatus. It should be noted that in each of the figures, oxide particles are not shown.

For example, the oxide-dispersed metal porous body includes a metal porous body base, and a plating layer formed on a surface of the metal porous body base. Here, the term "metal porous body base" refers to a base material including a metal framework. The above-described metal framework defines a two-dimensional hole (for example, an aperture described below) or a three-dimensional space (for example, a pore described below). The plating layer includes dispersed oxide particles. In this case, the oxide particles are carried in the metal framework (for example, fibrous portion <NUM> described below) unevenly at a surface layer portion. In other words, it can be understood that the oxide particles are carried in the metal framework as a portion of the plating layer. Moreover, the above-described oxide particles may be carried on the surface of the plating layer. The plating layer (hereinafter, referred to as "oxide-dispersed plating layer") including the dispersed oxide particles can be formed by the following method, for example.

First, a plating bath in which the oxide particles are dispersed is prepared. The plating bath is preferably stirred to sufficiently disperse the oxide particles. When a nickel plating layer is to be formed, a general plating bath including nickel sulfamate may be used as the plating bath, for example. The plating bath is preferably stirred to hit a liquid flow against the surface of the metal porous body base.

An amount of the oxide particles added to the plating bath is preferably <NUM>/L to <NUM>/L, is more preferably <NUM>/L to <NUM>/L, and is further preferably <NUM>/L to <NUM>/L. Accordingly, an oxide-dispersed plating layer having a sufficient amount of oxide particles incorporated therein can be formed, and fine holes of the metal porous body base can be sufficiently avoided from being blocked by too many oxide particles.

An average particle diameter of the oxide particles obtained in accordance with a laser diffraction type particle diameter distribution based on volume as a reference is preferably more than or equal to <NUM> and less than or equal to <NUM>, is more preferably more than or equal to <NUM> and less than or equal to <NUM>, and is further preferably more than or equal to <NUM> and less than or equal to <NUM>. In other words, the average particle diameter of the oxide particles is preferably more than or equal to <NUM> and less than or equal to <NUM>, is more preferably more than or equal to <NUM> and less than or equal to <NUM>, and is further preferably more than or equal to <NUM> and less than or equal to <NUM>. When the average particle diameter falls within such a range, precipitation due to aggregation of the oxide particles in the plating liquid is likely to be suppressed, the fine holes of the metal porous body base are also sufficiently avoided from being blocked by too large oxide particles, and the oxide particles are likely to be incorporated in the plating layer. The above-described average particle diameter can be measured by Partica LA-<NUM> (trademark), which is a laser diffraction type particle size distribution measurement device provided by HORIBA, for example. The target powders are mixed with a solvent such as water, and are then dispersed using ultrasonic waves or the like. An appropriate refractive index is set to measure the particle size distribution and the average particle diameter is calculated.

Next, the metal porous body base may be immersed in the plating bath, which is being stirred to disperse the oxide particles, thereby forming an oxide-particle-dispersed plating layer on the surface of the metal porous body base. Moreover, the plating process is preferably performed while stirring the plating bath. In order to sufficiently secure an amount of the oxide particles carried therein and obtain a lightweight, inexpensive oxide-dispersed metal porous body, an amount of the metal for plating (amount of the oxide-particle-dispersed plating layer) is preferably <NUM>/m<NUM> to <NUM>/m<NUM>, is more preferably <NUM>/m<NUM> to <NUM>/m<NUM>, and is further preferably <NUM>/m<NUM> to <NUM>/m<NUM> per unit surface area of the metal porous body base. The amount of the metal for plating is determined by the following formula: {(the mass (g) of the oxide-dispersed metal porous body after performing the plating process) - (the mass (g) of the metal porous body base before performing the plating process)}/(the surface area (m<NUM>) of the metal porous body base before performing the plating process).

For the metal porous body base, a mesh, an expanded metal, a punching metal, a metal porous body having a three-dimensional mesh structure, or the like can be used. Among these, the metal porous body having the three-dimensional mesh structure is preferably used as the metal porous body base because an electrode surface can be made large. The material of the metal porous body base is stable in the electrolyte solution. It includes at least one selected from the group consisting of nickel or nickel alloy, aluminum or aluminum alloy, stainless steel, iron. For the material of the metal porous body base, stainless steel, iron, nickel is preferable. Nickel, which has a wide stable potential range in alkali, is particularly preferable.

The following illustratively further describes the oxide-dispersed metal porous body including the metal porous body base having the three-dimensional mesh structure.

The three-dimensional mesh framework is a metal framework having a nonwoven-fabric-like structure or a sponge-like structure, and is provided with a plurality of pores defined by the framework, for example. In another aspect of the present embodiment, it can be also understood that the three-dimensional mesh framework is provided with a plurality of pores <NUM> defined by fibrous portion <NUM> described below. Such a metal framework and a pore surrounded by the framework constitute one cell. The external appearance of the metal porous body base has a shape in the form of a sheet. Moreover, the external appearance of the oxide-dispersed metal porous body has a shape in the form of a sheet.

As shown in <FIG>, one cell can be represented as a regular dodecahedron model, for example. Pore <NUM> is defined by a fibrous or bar-like metal portion (fibrous portion <NUM>). The plurality of pores <NUM> are connected three-dimensionally (not shown). The framework of the cell is formed by fibrous portion <NUM> extending consecutively. In the cell, an aperture (or window) <NUM> having a substantially pentagon shape surrounded by fibrous portion <NUM> is formed. Adjacent cells communicate with each other with one aperture <NUM> being shared therebetween. That is, the framework of the metal porous body is formed by fibrous portion <NUM> that forms a mesh network while defining the plurality of consecutive pores <NUM>. The framework having such a structure is referred to as "three-dimensional mesh framework".

As shown in <FIG>, a void 102a may be provided in fibrous portion <NUM>, i.e., fibrous portion <NUM> may be hollow. The metal porous body having such a hollow framework is very lightweight although it has a bulky three-dimensional structure. It should be noted that although not shown in the figures, fibrous portion <NUM> of the oxide-dispersed metal porous body has a two-layer structure including the metal framework of the metal porous body base and the oxide-dispersed plating layer. Moreover, the oxide-dispersed plating layer should be formed at least on a surface of the metal framework opposite to its surface facing void 102a.

The metal porous body base can be formed by coating, with a metal, a porous body composed of a resin (hereinafter, also referred to as "resin porous body") provided with communication pores, for example. The coating with the metal can be performed through a plating method, a vapor method (vapor deposition, plasma chemical vapor deposition, sputtering, or the like), application of a metal paste, or the like, for example. As a result of the coating with the metal, the three-dimensional mesh framework is formed. Among the above methods, the plating method is preferably used for the coating with the metal.

As the plating method, any method may be employed as long as a metal layer can be formed on the surfaces of the resin porous body (inclusive of the surface thereof at the inner space side) by the method. As the plating method, a known plating method can be employed, such as an electroplating method or a molten salt plating method. Through the plating method, a three-dimensional mesh metal porous body corresponding to the shape of the resin porous body is formed. That is, the aperture diameter and pore diameter (cell diameter) of the metal porous body to be obtained can be controlled in accordance with the pore diameter (cell diameter) of the resin porous body.

When the plating process is performed using the electroplating method, it is desirable to form an electrically conductive layer on the surface of the resin porous body prior to the electroplating. The electrically conductive layer may be formed on the surface of the resin porous body by electroless plating, vapor deposition, sputtering, or the like, may be formed thereon by application of an electrically conductive agent or the like, or may be formed thereon by immersing the resin porous body in a fluid dispersion including the electrically conductive agent.

The resin porous body is not particularly limited as long as the resin porous body is provided with the communication pores. A resin foam, a nonwoven fabric composed of a resin, or the like can be used for the resin porous body. Among these, the resin foam is preferable because the communication pores are likely to be formed in the metal porous body. As the resin for the porous body such as the resin foam, it is preferable to employ a resin that can be removed by decomposition or melting after the metal coating while the metal framework having the three-dimensional mesh structure remains. In this case, framework (fibrous portion) <NUM> can be hollow. Examples thereof include: thermosetting resins such as thermosetting polyurethane and melamine resins; thermoplastic resins such as olefin resins (polyethylene, polypropylene, and the like) and thermoplastic polyurethane; and the like. Among these, it is preferable to use the thermosetting polyurethane or the like because the pores are likely to be formed to have more uniform sizes or shapes.

After removing the resin in the framework through decomposition or melting, components (the resin, decomposed material, unreacted monomer, and the like) remaining in the framework may be removed by washing. The resin may be removed by heating while appropriately applying voltage as required. Moreover, the heating may be performed while applying voltage with the plated porous body being immersed in the molten salt plating bath. By thus removing the resin after the metal coating, the metal porous body base in which the void is formed inside the framework is obtained. Moreover, the metal porous body base has a three-dimensional mesh structure corresponding to the shape of the resin foam. It should be noted that examples of a commercially available metal porous body base include "Aluminum-Celmet®" or "Celmet®" of copper or nickel, both of which are provided by Sumitomo Electric Industries (<FIG> and <FIG>).

The external appearance of the metal porous body base has a shape in the form of a sheet, the mass per unit area of the shape is preferably <NUM>/m<NUM> to <NUM>/m<NUM>, and is more preferably <NUM>/m<NUM> to <NUM>/m<NUM>.

The average pore diameter in the metal porous body base is not particularly limited. For example, the average pore diameter in the metal porous body base may be <NUM> to <NUM>, may be <NUM> to <NUM>, may be <NUM> to <NUM>, or may be <NUM> to <NUM>. The above-described average pore diameter can be determined by the same method as a method for determining the diameter (average pore diameter) of pores <NUM> in the oxide-dispersed metal porous body described below.

Next, aperture diameter D of the oxide-dispersed metal porous body is determined as follows, for example. First, any one aperture 103a is selected from apertures <NUM> provided in the oxide-dispersed metal porous body. Diameter Dp of the maximum right circle C (see <FIG>) contained in the selected aperture 103a and the diameter of the minimum right circle that can contain aperture 103a are measured, and then the average value thereof is determined. This average value is regarded as aperture diameter Da of aperture 103a. Likewise, each of aperture diameters Db to Dj of a plurality of (for example, nine) any other apertures 103b to 103j of the oxide-dispersed metal porous body is determined. The average value of respective aperture diameters Da to Dj of these ten apertures 103a to 103j is regarded as aperture diameter D.

Specifically, in a SEM photograph of the main surface of the oxide-dispersed metal porous body, a region R is determined to include ten or more entire apertures <NUM>. From apertures <NUM> included in region R, for example, ten apertures <NUM> are selected randomly and respective aperture diameters Da to Dj of apertures 103a to 103j are calculated by the above-described method. The average value of the calculated aperture diameters Da to Dj of apertures 103a to 103j is regarded as aperture diameter D.

Aperture diameter D of the oxide-dispersed metal porous body is preferably <NUM> to <NUM>, and is more preferably <NUM> to <NUM>. In other words, the oxide-dispersed metal porous body preferably has an aperture diameter of <NUM> to <NUM>, and more preferably has an aperture diameter of <NUM> to <NUM>. Aperture diameter D can be determined by the following method, for example. In the SEM photograph of the main surface of the oxide-dispersed metal porous body, apertures suitable for measurement are selected, aperture diameters at ten or more positions are measured, and the average value thereof is determined, thereby determining aperture diameter D.

In order to improve release of gas, porosity P is more than or equal to <NUM> volume%, is preferably more than or equal to <NUM> volume%, and is particularly preferably more than or equal to <NUM> volume%. In other words, the oxide-dispersed metal porous body has a porosity of more than or equal to <NUM> volume%, preferably has a porosity of more than or equal to <NUM> volume%, and particularly preferably has a porosity of more than or equal to <NUM> volume%. Porosity P is less than <NUM> volume%, may be less than or equal to <NUM> volume%, or may be less than or equal to <NUM> volume%. These lower and upper limit values can be combined appropriately. The porosity (volume%) is determined by the following formula: {<NUM>-(the apparent specific gravity of the metal porous body/the actual specific gravity of the metal)} × <NUM>.

Diameter (also referred to as "cell diameter" or "average pore diameter") V1 of pore <NUM> in the oxide-dispersed metal porous body is not limited particularly. Pore diameter V1 may be <NUM> to <NUM>, may be <NUM> to <NUM>, or may be <NUM> to <NUM>, for example. Pore diameter V1 is determined as follows, for example. First, any one pore 101a is selected from pores <NUM> in the oxide-dispersed metal porous body. The diameter of the maximum sphere contained in the selected pore 101a and the diameter of the minimum sphere S (see <FIG>) that can contain pore 101a are measured, and the average value thereof is determined. This average value is regarded as pore diameter Va of pore 101a. Likewise, respective pore diameters Vb to Vj of a plurality (for example, nine) of any other pores 101b to 101j provided in the oxide-dispersed metal porous body are determined. The average value of pore diameters Va to Vj of these ten pores 101a to 101j is regarded as pore diameter V1.

Specifically, in a SEM photograph of the main surface of the oxide-dispersed metal porous body, a region V is determined to include ten or more entire pores <NUM>. From pores <NUM> included in region V, for example, ten pores <NUM> are selected randomly and respective aperture diameters Va to Vj of pores 101a to 101j are calculated by the above-described method. The average value of the calculated pore diameters Va to Vj of pores 101a to 101j is regarded as pore diameter V1.

When the shape of each pore is not truly spherical and has a specific aspect ratio, pore diameter (cell diameter) V1 in the present invention refers to a numerical value measured in a direction in which V1 is maximum.

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 metal porous body may be <NUM><NUM>/m<NUM> to <NUM><NUM>/m<NUM>, or may be <NUM><NUM>/m<NUM> to <NUM><NUM>/m<NUM>, for example.

Density d of apertures <NUM> in the oxide-dispersed metal porous body is also not particularly limited. Particularly, for resistance, density d is preferably <NUM>/<NUM> to <NUM>/<NUM>, and is more preferably <NUM>/<NUM> to <NUM>/<NUM>. It should be noted that density d refers to the number of apertures <NUM> on a straight line drawn on the surface of the oxide-dispersed metal porous body to have a length of <NUM> inch (= <NUM>). Here, when the straight line is terminated within an aperture located at an end portion of the straight line, this aperture is not counted.

Width Wf of framework (fibrous portion) <NUM> of the oxide-dispersed metal porous body is also not particularly limited. Particularly, for current collection, width Wf is preferably <NUM> to <NUM>, and is more preferably <NUM> to <NUM>.

Next, the following describes a hydrogen generation apparatus including the above-described oxide-dispersed metal porous body as an electrolysis electrode.

Hydrogen generation methods are roughly divided into: [<NUM>] an alkaline water electrolysis method using an alkaline aqueous solution; [<NUM>] a PEM method (Polymer Electrolyte Membrane method); and [<NUM>] a SOEC method (Solid Oxide Electrolysis Cell method). In each of the methods, the above-described metal porous body can be used as an electrolysis electrode (hereinafter, also simply referred to as "electrode").

In the alkaline water electrolysis method, an anode and a cathode are immersed in the alkaline aqueous solution (preferably, strong alkaline aqueous solution) and voltage is applied between the anode and the cathode, thereby electrolyzing the water. In this case, the above-described electrode can be used for at least one of the electrodes. At the anode, hydroxide ions are oxidized to generate oxygen and water. At the cathode, hydrogen ions are reduced to generate hydrogen. Since the electrode has large wettability with respect to water and has a large surface area, a contact area between each ion and the electrode is large, whereby the electrolysis efficiency of water is improved. Moreover, since the electrode has excellent electrical conductivity, the electrolysis efficiency of water is improved more. Further, since the porosity of the electrode is high, the generated hydrogen and oxygen can be released immediately. In order to improve the bubble releasability, water retentivity and electrical connection, one electrode may be constructed by layering a plurality of oxide-dispersed metal porous bodies having different pore diameters.

In order to prevent mixing of the generated hydrogen and oxygen, it is preferable to dispose a separating membrane (separator) between the anode and the cathode. The material of the separating membrane is not particularly limited as long as the material has wettability, ionic permeability, alkali resistance, non-electrical conductivity, non-gas permeability, thermal stability, and the like. Examples of the material of such a separator include: a fluororesin impregnated with potassium titanate; polyantimonate; polysulfone; hydrophilized polyphenylene sulfide; polyvinylidene fluoride; polytetrafluoroethylene; and the like. When a plurality of cells each constituted of the anode, the cathode, and the separator are stacked for use, it is preferable to dispose a separator, such as the one described above, between the cells in order to prevent short circuit.

A dissolved substance of the alkaline aqueous solution is also not particularly limited. Examples thereof include a hydroxide or the like of an alkali metal (lithium, sodium, potassium, rubidium, cesium, or francium) or an alkaline earth metal (calcium, strontium, barium, or radium). Among these, the hydroxide (particularly, NaOH or KOH) of the alkali metal is preferable because a strong alkaline aqueous solution is obtained. The concentration of the alkaline aqueous solution is also not particularly limited, and may be <NUM> mass% to <NUM> mass% in view of electrolysis efficiency. An operation temperature is, for example, about <NUM> to <NUM>, and a current density is, for example, about <NUM> A/cm<NUM> to <NUM> A/cm<NUM>.

In the PEM method, water is electrolyzed using a polymer electrolyte membrane. Specifically, in the PEM method, an anode and a cathode are disposed on respective surfaces of the polymer electrolyte membrane, water is introduced into the anode, and voltage is applied between the anode and the cathode, thereby electrolyzing the water. Also in this case, the above-described electrode can 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 the polymer electrolyte membrane, which is an electrolyte membrane. Hence, as compared with the alkaline water electrolysis method, a high-purity hydrogen can be extracted, advantageously. Moreover, since the above-described electrode has a large surface area, has large wettability with respect to water, and has excellent electrical conductivity, the electrode is suitable as the anode of the hydrogen generation apparatus (PEM type hydrogen generation apparatus) employing the PEM method.

Here, protons generated by the PEM type hydrogen generation apparatus are moved to the cathode through the polymer electrolyte membrane, and are extracted as the hydrogen at the cathode side. The operation temperature of the PEM type hydrogen generation apparatus is about <NUM>. As the polymer electrolyte membrane, it is possible to use a polymer having proton conductivity, such as perfluorosulfonate polymer, which has been conventionally used for a solid polymer fuel cell or the PEM type hydrogen generation apparatus. In some methods, a membrane having anion conductivity may be used. When the cathode includes the above-described electrode, the generated hydrogen can be released immediately.

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

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

When the above-described electrode is used as the electrode into which water vapor is to be introduced, the electrolysis efficiency of the water vapor is improved because the above-described electrode has a large surface area and large wettability with respect to water and therefore the contact area between the water vapor and the electrode is also large. Further, since the above-described electrode has excellent electrical conductivity, the electrolysis efficiency of the water vapor is improved more.

Next, based on Examples, the present invention will be more specifically described. The Examples below, however, do not limit the present invention.

An oxide-dispersed metal porous body was produced in the following procedure.

As a metal porous body base, a metal porous body composed of nickel (Celmet® provided by Sumitomo Electric Industries) was used which had a mass of <NUM>/m<NUM> per unit area, had a thickness of <NUM>, and had an average pore diameter of <NUM>. A plating bath including nickel sulfamate was prepared, and <NUM>/L of nickel oxide powder having an average particle diameter of <NUM> was added to the plating bath. This plating bath was used to perform nickel plating onto a surface of the metal porous body base while stirring the plating bath. A mass per unit area of the plated metal porous body (electrolysis electrode A) was <NUM>/m<NUM>.

Except that <NUM>/L of titanium oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode B) having a mass of <NUM>/m<NUM> per unit area.

Except that <NUM>/L of aluminum oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode C) having a mass of <NUM>/m<NUM> per unit area.

Except that <NUM>/L of zirconium oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode D) having a mass of <NUM>/m<NUM> per unit area.

Except that <NUM>/L of cerium oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode E) having a mass of <NUM>/m<NUM> per unit area.

Except that <NUM>/L of cobalt (II) oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode F) having a mass of <NUM>/m<NUM> per unit area.

Except that <NUM>/L of molybdenum oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode G) having a mass of <NUM>/m<NUM> per unit area.

Except that <NUM>/L of iridium oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode H) having a mass of <NUM>/m<NUM> per unit area.

Except that <NUM>/L of ruthenium oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode I) having a mass of <NUM>/m<NUM> per unit area.

Except that <NUM>/L of silicon oxide powder having an average particle diameter of <NUM> was added to the plating bath instead of nickel oxide, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode J) having a mass of <NUM>/m<NUM> per unit area.

Except that a plating bath having no oxide particles added therein was used, the same operation as that in Example <NUM> was performed to obtain a plated metal porous body (electrolysis electrode R) having a mass of <NUM>/m<NUM> per unit area.

An electrolyte solution (KOH aqueous solution having a concentration of <NUM>) was dropped onto the surface of each electrolysis electrode as a droplet having a diameter of about <NUM>. A time until the electrolyte solution completely permeated was measured. As a result, in the electrode of Comparative Example <NUM>, it took <NUM> seconds until the electrolyte solution completely permeated, whereas in each of the electrodes of Example <NUM> to Example <NUM>, it took approximately <NUM> second until the electrolyte solution completely permeated. This is presumably because the hydrophilicity of the metal porous body was improved by the plating layer having the oxide particles dispersed therein.

A hydrogen generation apparatus <NUM> as shown in <FIG> was assembled and a container <NUM> was filled with an electrolyte solution <NUM>, which was the same as the one described above. In electrolyte solution <NUM>, linear sweep voltammetry was performed and a measurement instrument <NUM> was used to find a relation between voltage and current corresponding to generation of hydrogen. A test temperature was set to <NUM>. A potential scanning range was set to -<NUM> V to -<NUM> V (vs. Hg/HgO reference electrode <NUM>). A workpiece <NUM> for the electrolysis electrode had a size of <NUM> squares. For a counter electrode <NUM>, the above-described metal porous body base having a size of <NUM> squares was used. An distance between the electrodes was <NUM>. A current value upon -<NUM> V (vs. Hg/HgO electrode) is shown in Table <NUM>.

As shown in Table <NUM>, the current value of each of electrolysis electrode A to electrolysis electrode J of Example <NUM> to Example <NUM> was higher than that of electrolysis electrode R of Comparative Example <NUM>. That is, the hydrogen generation ability of each of electrolysis electrode A to electrolysis electrode J of Example <NUM> to Example <NUM> was higher than that of electrolysis electrode R of Comparative Example <NUM>. From the above result, it was proved that the hydrogen generation ability of the electrolysis electrode is improved by the plating layer having the oxide particles dispersed therein.

The metal porous body according to the present invention is useful as various types of electrolysis electrodes.

Claim 1:
An oxide-dispersed metal porous body comprising a porous metal framework, and oxide particles carried in the metal framework, wherein the oxide-dispersed metal porous body has a porosity of more than or equal to <NUM> volume%, and wherein a material of the porous metal framework includes at least one selected from the group consisting of nickel, nickel alloy, aluminum, aluminum alloy, stainless steel, and iron, characterized in that:
an external appearance of the oxide-dispersed metal porous body has a shape in a form of a sheet,
a mass per unit area of the shape is <NUM>/m<NUM> to <NUM>/m<NUM>, wherein the unit area of the shape is a unit area of a projected area of the oxide-dispersed metal porous body having the shape in the form of a sheet, when the oxide-dispersed metal porous body is seen in a direction normal to the main surface thereof,
an amount of the oxide particles carried per unit area of the shape is <NUM>/m<NUM> to <NUM>/m<NUM>, wherein the amount of oxide particles carried per unit area of the shape is measured using the method described in the description, and
each of the oxide particles includes at least one selected from a group consisting of iron oxide, nickel oxide, titanium oxide, aluminum oxide, zirconium oxide, cerium oxide, cobalt (II) oxide, molybdenum oxide, ruthenium oxide, iridium oxide, tin oxide, and silicon oxide.