Laminate, membrane electrode assembly, water electrolysis device, and method for producing laminate

Abstract

A laminate according to the present invention comprises a porous metallic body on an electrolyte membrane. Fine metal particles are included at least in pores and / or in the electrolyte membrane-side surface of the porous metallic body. The average pore size of the porous metallic body is preferably 0.5-100 μm. The average particle size of the fine metal particles is preferably 5-200 nm. The thickness of the porous metallic body is preferably 1-500 μm. In addition, a fine metal particle layer is preferably provided between the electrolyte membrane and the porous metallic body. The porous metallic body is preferably a metal foam or a metal fiber mat.

Description

Stack, membrane electrode assembly, water electrolysis device, and method for manufacturing stack

[0001] The present disclosure relates to a laminate, a membrane electrode assembly, a water electrolysis device, and a method for manufacturing the laminate.

[0002] Technologies for storing and transporting renewable energy have been attracting attention. One possible example is using renewable energy to split water to produce hydrogen and oxygen, and then storing and transporting the hydrogen. Anion-exchange membrane water electrolysis, for example, is a water splitting method that can adapt to output fluctuations and allows the use of materials other than precious metals, such as stainless steel, for bipolar plates. This technology is expected to achieve both high performance and low cost, and is attracting attention as a next-generation technology. Current catalysts used in water electrolysis include those that have a catalyst layer in which precious metals, such as platinum or ruthenium, are supported on a porous support. Meanwhile, catalysts that do not use precious metals are desired from the perspective of cost reduction, and nickel-based catalysts are being considered, for example. The present inventors have disclosed base metal catalysts suitable for anode electrodes and methods for producing the same in Patent Documents 1 and 2.

[0003] US2024 / 0254639 A1 International Publication No. 2022 / 250122 Pamphlet

[0004] The catalyst is usually used in combination with an electrolyte membrane to form a membrane electrode assembly. The present inventors have found that the state of the interface between the catalyst and the electrolyte membrane and its surroundings affects catalyst performance.

[0005] An object of the present disclosure is to provide a membrane electrode assembly with higher activity, a laminate suitable for the assembly, and a method for producing the same.

[0006] The present disclosure includes the following aspects. [1] A laminate comprising a metal porous body on an electrolyte membrane, wherein the metal porous body has metal fine particles at least on the surface facing the electrolyte membrane and / or within the pores. [2] The laminate according to [1], wherein the metal porous body has an average pore size of 0.5 μm to 100 μm. [3] The laminate according to [1] or [2], wherein the metal fine particles have an average particle size of 5 nm to 200 nm. [4] The laminate according to any one of [1] to [3], wherein the metal porous body has a thickness of 1 μm to 500 μm. [5] The laminate according to any one of [1] to [4], wherein a metal fine particle layer is further provided between the electrolyte membrane and the metal porous body. [6] The laminate according to any one of [1] to [5], wherein the metal porous body is a metal foam or a metal fiber mat. [7] The laminate according to any one of [1] to [6], wherein the metal porous body contains NiOOH. [8] The laminate according to any one of [1] to [7], wherein the metal fine particles are fixed to the metal porous body. [9] The laminate according to any one of [1] to [8], wherein the metal fine particles comprise NiOOH.

[10] The laminate according to any one of [1] to [9], wherein the metal porous body is a catalyst.

[11] The laminate according to any one of [1] to

[10] , wherein the electrolyte membrane is an anion conductive membrane.

[12] A membrane electrode assembly comprising the laminate according to any one of [1] to

[11] and a cathode disposed on the electrolyte membrane side of the laminate.

[13] A water electrolysis device comprising the membrane electrode assembly according to

[12] .

[14] A method for producing a laminate according to any one of [1] to

[11] , comprising: a step (I) of adhering metal fine particles to at least one surface and / or inside pores of the metal porous body; and a step (II) of stacking the surface of the metal porous body to which the metal fine particles are attached to an electrolyte membrane.

[15] The method for producing a laminate according to

[14] , further comprising a step (III) of catalyzing the metal porous body and the metal fine particles between the steps (I) and (II).

[0007] An object of the present disclosure is to provide a membrane electrode assembly with higher activity, a laminate suitable for the assembly, and a method for producing the same.

[0008] FIG. 1 is a schematic cross-sectional view showing an example of a laminate. FIG. 2 is an enlarged view showing an example of part A in FIG. 1. FIG. 3 is an enlarged view showing an example of part A in FIG. 1. FIG. 4 is a schematic cross-sectional view showing an example of a membrane electrode assembly. FIG. 5 is a schematic cross-sectional view showing an example of a water electrolysis device. FIG. 6 is an SEM image of the inside of the metal porous body of Example 2. FIG. 7 is a graph showing current-voltage curves of the water electrolysis devices of Comparative Example 1 and Examples 1 to 3. FIG. 8 is a graph showing current-voltage curves of the water electrolysis devices of Comparative Example 2 and Examples 4 to 6.

[0009] Hereinafter, a laminate, a manufacturing method thereof, and a membrane electrode assembly according to the present invention will be described based on embodiments. For clarity of explanation, the following description and drawings have been simplified as appropriate. For ease of explanation, the scale of each component in the drawings may differ significantly. Furthermore, in this specification, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively, unless otherwise specified.

[0010] [Laminate] A laminate according to a first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic cross-sectional view showing an example of the laminate, and FIG. 2 is an enlarged view of portion A in FIG. 1. The laminate 30 shown in the example of FIGS. 1 and 2 includes a metal porous body 10 on an electrolyte membrane 5. The electrolyte membrane 5 and the metal porous body 10 are in direct contact with each other. While FIG. 1 shows the electrolyte membrane 5 and the metal porous body 10 as having the same length and width, the size relationship between the two is not limited thereto. For example, the electrolyte membrane 5 and the metal porous body 10 may have different sizes. Furthermore, the laminate 30 includes metal microparticles 16 on the surface and / or within the pores 15 of the metal porous body 10. The metal microparticles 16 may be disposed on at least the surface facing the electrolyte membrane 5 and / or within the pores 15. From the viewpoint of preventing unintended clogging of the pores of the metal porous body and thereby obtaining a laminate suitable for a highly efficient membrane-electrode assembly, it is preferable that the metal microparticles 16 be disposed within the pores 15. When metal microparticles 16 are disposed in pores 15, it is sufficient that the metal microparticles 16 are disposed at least in the pores 15 on the electrolyte membrane side of the metal porous body 10. Alternatively, the metal microparticles 16 may be disposed throughout the pores 15 of the metal porous body 10. Here, the "pores on the electrolyte membrane side" refers to pores formed within a range of up to 100 nm deep from the interface of the metal porous body on the electrolyte membrane side.

[0011] The metal microparticles 16 may be supported on the surface of the metal porous body 10, or may be fixed. Alternatively, they may exist in both supported and fixed states. Here, "supported" refers to a state in which the surface of the metal porous body 10 and the metal microparticles 16 are simply in contact with each other, with no bonding force between them. Furthermore, "fixed" refers to a state in which the surface of the metal porous body 10 and the metal microparticles 16 are bonded together in such a way that a mechanical bonding force (e.g., anchoring effect such as engagement and interlocking) or a chemical bonding force is generated between them. Whether the surface of the metal porous body 10 and the metal microparticles 16 are fixed to each other can be confirmed, for example, by observation using a transmission electron microscope. Furthermore, as shown in part B of FIG. 2 , other metal microparticles 16 may be stacked on the metal microparticles 16 supported on the surface of the metal porous body 10. In this case, the stacking may be by supporting or by fixing.

[0012] The material of the metal porous body 10 may be a metal element or an alloy, or may contain a metal oxide. Specific examples of materials for the metal porous body include platinum, cobalt, nickel, palladium, iron, silver, gold, copper, iridium, molybdenum, rhodium, chromium, tungsten, manganese, ruthenium, and alloys containing these metals, metal compounds containing the above metals, metal oxides, and combinations thereof. From the viewpoint of production cost, the metal porous body preferably contains nickel. Furthermore, from the viewpoint of obtaining a laminate suitable for a highly efficient membrane electrode assembly, the metal porous body 10 preferably has catalytic activity. From the viewpoint of improving catalytic activity, the metal porous body preferably contains NiOOH. For example, a layer containing NiOOH can be formed on the surface of the metal porous body by the method described below.

[0013] The metal porous body 10 may have any shape as long as it has pores capable of supporting the metal microparticles 16. Examples of such porous bodies include metal particle linked bodies formed by fusing together metal particles, foams of the above metals, felts (nonwoven fabrics, fiber mats) formed from wire-like or fibrous metals, and mesh-like porous bodies. When the metal porous body is a metal nonwoven fabric or a metal fiber mat, voids exist between the gaps between the wire-like or fibrous metals. In both the metal particle linked bodies and the porous body, the pores may or may not have a continuous pore structure. When the laminate of the present invention is used in a membrane / electrode assembly, the pores preferably have a continuous pore structure in order to further increase the efficiency of the membrane / electrode assembly. That is, the pores preferably open at the surface of the metal porous body, extend toward the interior of the metal porous body, and have the other end open at the surface of the metal porous body. The pores may branch within the metal porous body. Furthermore, the pores may intersect with each other within the metal porous body. The interconnected pore structure of the pores allows, for example, when metal fine particles are supported or fixed in the pores of the metal porous body to obtain a membrane electrode assembly, a larger amount of reactants can be supplied to the metal fine particles located in the pores through the multiple openings. As a result, the efficiency of the membrane electrode assembly can be improved. The interconnected pore structure can be confirmed, for example, by observing the metal porous body with a transmission electron microscope. From the standpoints of water and gas diffusibility and durability, the metal porous body 10 is preferably a metal foam or a metal fiber mat.

[0014] The pore size of the pores in the metal porous body 10 is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1 μm or more, even more preferably 10 μm or more, and even more preferably 13 μm or more, in terms of the diffusibility of water and gas and the ease with which the metal microparticles 16 penetrate into the pores. On the other hand, the upper limit of the average pore size is preferably 100 μm or less, more preferably 85 μm or less, even more preferably 75 μm or less, even more preferably 20 μm or less, even more preferably 18 μm or less, and particularly preferably 15 μm or less, in terms of the strength of the metal porous body. Here, the pore size refers to the pore size on the surface of the metal porous body 10. The average pore size is determined by observing the surface of the metal porous body 10 using a scanning electron microscope, randomly selecting at least 30 pores, measuring the longest diameter of each pore, and averaging the measured values.

[0015] The thickness of the metal porous body 10 is preferably 1 μm or more, more preferably 1.5 μm or more, even more preferably 2 μm or more, even more preferably 20 μm or more, and even more preferably 30 μm or more, from the viewpoint of the strength of the metal porous body and improving the performance of a water electrolysis device using the laminate. On the other hand, the upper limit of the thickness of the metal porous body 10 is not particularly limited, but 500 μm or less is sufficient, preferably 400 μm or less, more preferably 250 μm or less, even more preferably 50 μm or less, even more preferably 45 μm or less, and even more preferably 40 μm or less. The thickness of the metal porous body represents the average value of values ​​measured at any five points on the metal porous body. The thickness can be measured, for example, using a micrometer.

[0016] The material of the metal microparticles 16 may be a simple metal or an alloy, or may contain a metal oxide. Specific examples of the material of the metal microparticles include platinum, cobalt, nickel, palladium, iron, silver, gold, copper, titanium, iridium, molybdenum, rhodium, chromium, tungsten, manganese, ruthenium, and alloys containing these metals, metal compounds containing the above metals, metal oxides, and combinations thereof. From the viewpoint of production cost, the metal microparticles preferably contain nickel. Furthermore, from the viewpoint of obtaining a laminate suitable for a highly efficient membrane electrode assembly, the metal microparticles 16 preferably have catalytic activity. From the viewpoint of improving catalytic activity, the metal microparticles preferably contain NiOOH. For example, a layer containing NiOOH can be formed on the surface of the metal microparticles by the method described below.

[0017] The particle size of the metal microparticles 16 is preferably an average pore size of 200 nm or less, more preferably 150 nm or less, and even more preferably 120 nm or less, from the viewpoint of effectively disposing the metal microparticles in the pores of the metal porous body 10. On the other hand, the lower limit of the particle size of the metal microparticles 16 is not particularly limited, but from the viewpoint of ease of manufacturing the metal microparticles, the average particle size is preferably 5 nm or more, more preferably 8 nm or more, and even more preferably 10 nm or more. Here, the average particle size is determined by observing the metal microparticles 16 using a scanning electron microscope, randomly selecting at least 30 metal microparticles 16, measuring the longest diameter of each particle, and averaging the measured diameters.

[0018] The electrolyte membrane 5 may be selected appropriately depending on the configuration of the water electrolysis device, and may be either an anion conductive membrane or a proton conductive membrane. When the metallic porous body 10 is used on the anode side, the electrolyte membrane 5 is preferably an anion conductive membrane.

[0019] Examples of polymers constituting anion conductive membranes include polymers having quaternary ammonium groups and imidazolium groups. From the viewpoint of chemical durability such as alkali durability, the polymers have an ether bond (—O—) or a sulfonyl group (—S(═O)) in the main chain skeleton. ２Polymers that do not have a carbonyl group (-C(=O)-) are preferred. Examples of such polymers include the polymers described in JP 2021-161472 A and JP 2021-042351 A. Among them, from the viewpoint of further increasing the efficiency of the membrane electrode assembly, polymers that include a structure represented by the following formula (1) are preferred.

[0020] In formula (1), each R is independently -N+(R １ ) ３ A quaternary ammonium group represented by R １ are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and a plurality of R １ They may be linked together to form a nitrogen-containing ring structure; A is a monovalent cation; m is an integer of 1 to 18; and n is an integer of 1 or more.

[0021] The thickness of the electrolyte membrane 5 is preferably within a predetermined range. Specifically, when the laminate is used in a membrane electrode assembly, the thickness of the electrolyte membrane 5 can be appropriately adjusted within a range of 1 μm to 100 μm, and is preferably 2 μm to 80 μm, in order to further increase the efficiency of the membrane electrode assembly. The thickness of the electrolyte membrane represents the average value of values ​​measured at any five points on the electrolyte membrane. The thickness can be measured, for example, with a micrometer.

[0022] In the laminate of this embodiment, the amount of metal fine particles arranged in the metal porous body is preferably within a predetermined range. Specifically, in order to obtain a laminate suitable for a highly active membrane electrode assembly, the amount of metal fine particles arranged is set to 1 cm of the metal porous body. ２ 0.5 mg / cm ２ It is preferable that the concentration is 1.0 mg / cm or more. ２ More preferably, it is 1.5 mg / cm or more. ２ From the viewpoint of reducing the manufacturing cost, the amount of metal fine particles to be arranged is preferably 1 / cm 2 of the porous metal body. ２ 10.0 mg / cm ２ Preferably, it is 8.5 mg / cm or less. ２ More preferably, it is 6.5 mg / cm or less.２ The amount of metal microparticles disposed can be measured, for example, by subtracting the mass of the metal porous body before the metal microparticles are disposed from the mass of the metal porous body after the metal microparticles are disposed, and dividing the result by the surface area of ​​the metal porous body.

[0023] The laminate 30 of the first embodiment has the above-described configuration, which increases the total surface area of ​​the porous metal body and the metal fine particles. Therefore, for example, when a membrane electrode assembly using the laminate is used for water electrolysis, the contact area with water increases, accelerating the reaction. Furthermore, the metal fine particles within the pores subdivide the flow paths, preventing the generated gas from accumulating, thereby preventing a decrease in reaction efficiency even during continuous use of the water electrolysis device. Furthermore, the metal fine particles arranged on the surface of the porous metal body prevent the porous metal body from coming into direct contact with the electrolyte membrane, thereby preventing mechanical damage to the electrolyte membrane, even when force is applied in the plane direction of the laminate.

[0024] Next, a laminate of a second embodiment will be described with reference to FIG. 3 . FIG. 1 is common to the first embodiment, and FIG. 3 is an enlarged view showing an example of portion A in FIG. 1 . The laminate shown in the example of FIG. 3 has a metal fine particle layer 50 between an electrolyte membrane 5 and a metal porous body 10. That is, the electrolyte membrane 5 and the metal porous body 10 are respectively arranged on different sides of the metal fine particle layer 50. In the laminate of this embodiment, the electrolyte membrane 5, the metal fine particle layer 50, and the metal porous body 10 are arranged in this order. The electrolyte membrane 5 and the metal fine particle layer 50 are in direct contact with each other, and the metal fine particle layer 50 and the metal porous body 10 are also in direct contact with each other. In FIG. 3 , the electrolyte membrane 5, the metal fine particle layer, and the metal porous body 10 are shown to have the same length, but the size relationship between the three is not limited thereto. For example, the electrolyte membrane 5, the metal fine particle layer 50, and the metal porous body 10 may be different sizes.

[0025] In this embodiment, the metal microparticle layer 50 refers to a layer formed by the aggregation of a plurality of metal microparticles 16. The metal microparticles constituting the metal microparticle layer 50 can be the same as the metal microparticles 16 disposed on the surface and / or within the pores 15 of the metal porous body 10. The thickness of the metal microparticle layer 50 is preferably within a predetermined range. Specifically, from the viewpoints of mass transfer and catalyst surface area, the thickness of the metal microparticle layer is preferably 5 nm to 40 μm, more preferably 10 nm to 20 μm, even more preferably 15 nm to 10 μm, even more preferably 15 nm to 500 nm, even more preferably 15 nm to 450 nm, and particularly preferably 15 nm to 400 nm. The thickness of the metal microparticle layer represents the average value of values ​​measured at any five points on the metal microparticle layer. The thickness can be measured, for example, using a micrometer.

[0026] The other configurations of the second embodiment are the same as those of the first embodiment, and therefore will not be described here.

[0027] The laminate of the second embodiment has the above-described configuration, which increases the total surface area of ​​the metal porous body and the metal fine particles. Therefore, for example, when a membrane electrode assembly using the laminate is used for water electrolysis, the contact area with water increases, accelerating the reaction. Furthermore, the metal fine particles in the pores subdivide the flow paths, preventing the generated gas from accumulating, thereby preventing a decrease in reaction efficiency even during continuous use of the water electrolysis device. Furthermore, the metal fine particles and metal fine particle layer arranged on the surface of the metal porous body can prevent the metal porous body from coming into direct contact with the electrolyte membrane, preventing mechanical damage to the electrolyte membrane even when force is applied in the plane direction of the laminate, for example.

[0028] In both the first and second embodiments, it is preferable that at least one of the metal porous body and the metal fine particles be catalyzed. This is because catalyzing the metal porous body and / or the metal fine particles (hereinafter also referred to as "metal porous body, etc.") enables the production of a membrane electrode assembly with higher activity. Among the catalyzed metal porous bodies, those having a nickel oxide layer containing NiOOH are preferred, and those having a layer containing NiFe on the nickel oxide layer are even more preferred. Specific methods for catalysis will be described later. Furthermore, the catalyst surface may be coated with a known electrolyte polymer (ionomer). On the other hand, in this embodiment, ionic conductivity is exhibited by the movement of water (solution) within the membrane electrode assembly described later, resulting in excellent ionic conductivity even without the use of an electrolyte polymer.

[0029] [Membrane Electrode Assembly] A membrane electrode assembly will be described with reference to FIG. 4. FIG. 4 is a schematic cross-sectional view showing an example of a membrane electrode assembly. The membrane electrode assembly 8 shown in the example of FIG. 4 includes at least a cathode 20, an electrolyte membrane 5, and a metal porous body 10. The stack of the electrolyte membrane 5 and the metal porous body 10 in this embodiment is the stack 30 in Embodiment 1 or 2. In the membrane electrode assembly 8 of this embodiment, the cathode 20 is disposed on the electrolyte membrane 5 side of the stack 30. The electrolyte membrane 5 and the cathode 20 are in direct contact with each other. The membrane electrode assembly 8 may also include other layers, such as a gas diffusion layer used in a water electrolysis device. In the membrane electrode assembly 8, the metal porous body 10 functions as an anode.

[0030] The cathode 20 can be appropriately selected from known materials. An example of the cathode 20 is a catalyst layer containing metal particles supported on carbon. The metal particles may be a simple metal or an alloy, or may contain a metal oxide. Specific examples of the material of the metal particles include platinum, cobalt, nickel, palladium, iron, silver, gold, copper, titanium, iridium, molybdenum, rhodium, chromium, tungsten, manganese, ruthenium, alloys containing these metals, metal compounds containing these metals, metal oxides, and combinations thereof. To further increase the efficiency of the membrane electrode assembly, the metal particles preferably contain at least one metal selected from the group consisting of platinum, ruthenium, nickel, cobalt, and manganese. The cathode 20 may further include a diffusion layer. Examples of the diffusion layer include a foam metal layer such as nickel foam and a porous carbon layer such as carbon paper. To further increase the efficiency of the membrane electrode assembly, a porous carbon layer is preferred. When a porous carbon layer is used as the diffusion layer, the thickness thereof can be set to 50 μm or more and 300 μm or less.

[0031] [Water Electrolysis Apparatus] A water electrolysis apparatus will be described with reference to FIG. 5 . FIG. 5 is a schematic cross-sectional view showing an example of a water electrolysis apparatus. The water electrolysis apparatus 1 shown in the example of FIG. 5 includes an electrolyte membrane 5, an anode 10 disposed on one side of the electrolyte membrane 5, a cathode 20 disposed on the other side, a power source 7 connected to the anode 10 and the cathode 20, and a water supply unit (not shown) that supplies water or an alkaline aqueous solution to the anode 10. In this embodiment, the anode 10 is the porous metal body 10 described above and functions as an anode catalyst 11 and a first diffusion layer 12. The cathode 20 only needs to include at least a cathode catalyst 21 and may further include a second diffusion layer 22. The membrane electrode assembly 8 includes at least the anode 10 disposed on one side of the electrolyte membrane 5 and the cathode 20 disposed on the other side. In the example of FIG. 5 , a cell 6 is configured, further including separators 13 and 23 on the outer sides of the anode 10 and the cathode 20, respectively. The water electrolysis device 1 may be a single cell 6 or may be a stack of a plurality of cells 6. The water supply unit may supply water to at least one of the cathode and the anode.

[0032] When the water electrolysis device is an anion exchange membrane type water electrolysis device, for example, when a voltage is applied to both electrodes while water or an alkaline aqueous solution is supplied to the anode 10 side, water is also supplied to the cathode electrode side, and the following reaction occurs on the cathode 20 side, generating hydrogen gas: 2H ２ O + 2e － →2OH － +H ２ Hydroxide ion (OH － ) permeates the electrolyte membrane 5 and moves to the anode 10. At the anode 10, the following reaction occurs, generating oxygen gas: － →H ２ O+1 / 2O ２ +2e － The generated hydrogen and oxygen are discharged from the cell 6 through gas flow paths 14 and 24 provided in the separators 13 and 23, respectively. The gas flow paths are connected to a storage tank or the like via a gas-liquid separator (not shown), and the hydrogen and oxygen are each stored in the storage tank or the like after water is separated from them in the gas-liquid separator.

[0033] The water supplied to the water electrolysis apparatus may be pure water or an alkaline aqueous solution. By using an alkaline aqueous solution, water electrolysis can be performed more efficiently than with pure water. The solute in the alkaline aqueous solution is not particularly limited, and may be, for example, potassium hydroxide of 1 M or less.

[0034] The water electrolysis apparatus may have separators 13 and 23 on the outside of the anode 10 and the cathode 20, respectively. The separator material does not need to be a platinum-coated material, and may be made of an appropriate material such as carbon or stainless steel. When the separators 13 and 23 are conductive, the separator 13 may be used as a first main electrode, the separator 23 may be used as a second main electrode, and a power source 7 may be connected to the first main electrode and the second main electrode to apply a voltage to the cathode and the anode.

[0035] The separators 13 and 23 may have gas flow channels 14 and 24. The oxygen generated at the anode 10 and the hydrogen generated at the cathode 20 are discharged through the gas flow channels 14 and 24, respectively, and stored in a storage tank or the like.

[0036] The power supply 7 is not particularly limited and can be appropriately selected from known DC power supplies. Because the water electrolysis apparatus has excellent response to input power, it can be suitably used with renewable energy sources such as solar power generation and wind power generation, which have large fluctuations.

[0037] [Manufacturing Method of Laminate] An embodiment of a manufacturing method of the laminate will be described. Note that the laminate is not limited to those manufactured by the manufacturing method below, but the laminate can be easily manufactured by the manufacturing method below. The manufacturing method of the laminate of this embodiment includes at least a step (I) of adhering metal fine particles to at least one surface and / or inside the pores of the metal porous body, and a step (II) of placing the surface of the metal porous body to which the metal fine particles are attached on an electrolyte membrane and laminating them, and may include other steps as necessary. Note that the division of each step is for convenience, and is not necessarily clearly distinguished when multiple steps are performed simultaneously or consecutively, for example.

[0038] Examples of methods for attaching metal microparticles to a metal porous body include the following: (Ia) a method in which a metal porous body is immersed in a dispersion of metal microparticles and the dispersion medium is removed to attach metal microparticles to the pores of the metal porous body; (Ib) a method in which a metal porous body is immersed in a solution containing metal ions that will become the metal microparticles and the metal microparticles are purified on the surface of the metal porous body by a chemical reduction method or the like; (Ic) a method in which a dispersion of metal microparticles is applied to the surface of a metal porous body by a known coating method or printing method and dried to attach metal microparticles to the pores of the metal porous body; (Id) a method in which a metal microparticle layer is formed on the surface of an electrolyte membrane by a known coating method or printing method, a metal porous body is placed on the metal microparticle layer, and pressure is applied to attach metal microparticles to the pores of the metal porous body. Note that in the above method (Id), steps (I) and (II) are performed simultaneously. By any of the above methods (Ia), (Ib), (Ic) and (Id), metal fine particles can be supported or fixed on the surface of the metal porous body.

[0039] Next, the surface of the metal porous body to which the metal fine particles are attached is placed on the electrolyte membrane and laminated. The electrolyte membrane and the metal porous body may be simply overlapped, or may be bonded or pressed together, or may be fixed with a jig. Alternatively, the anode may be laminated at the same time to produce a membrane electrode assembly, and the separator and other elements may also be laminated at the same time. When producing the laminate of the second embodiment, a metal fine particle layer may be formed in advance on the surface of the electrolyte membrane and / or the metal porous body, and then the electrolyte membrane and the metal porous body may be laminated. The metal fine particle layer can be formed by applying an ink containing a mixture of metal fine particles and a polymer, etc., to the surface of the electrolyte membrane and / or the metal porous body. The method of applying the ink is not particularly limited, and for example, spray coating can be used.

[0040] The metal porous body and / or the metal fine particles are preferably catalyzed. The catalysis may be carried out separately for the metal porous body and the metal fine particles, but by carrying out the catalysis between the above steps (I) and (II), the catalysis can be carried out simultaneously.

[0041] The catalytic method is appropriately selected depending on the metal species constituting the metal porous body and / or metal fine particles. As an example, a suitable catalytic method when the metal porous body and / or metal fine particles contain nickel will be described below.

[0042] As a method for forming a nickel oxide layer containing NiOOH on a nickel-containing porous metal body and / or metal fine particles, a method of oxidizing the surface of the porous metal body and / or metal fine particles is preferred from the viewpoint of maintaining the state in which the metal fine particles are attached within the pores of the porous metal body. Electrochemical oxidation is preferred as a method for oxidizing the surface. Examples of electrochemical oxidation include a method in which a porous metal body having metal fine particles attached thereto is prepared, the porous metal body is immersed in an alkaline electrolyte, or the like, and oxidized by applying a voltage. The thickness of the nickel oxide layer can be adjusted by adjusting the voltage application time. Next, if necessary, a layer containing NiFe is formed on the nickel oxide layer. Examples of methods for forming a NiFe-containing layer on the nickel oxide layer include a method in which NiFe particles are sprayed by aerosol deposition or the like, and a method in which Fe is electrodeposited. The method of electrodepositing Fe is preferred because it is easy to form a NiFe-containing layer even within the pores of the porous metal body. The electrodeposition of Fe can be performed, for example, by ２＋ and a method for electrodeposition by applying a voltage to the porous metal body and / or metal fine particles having the nickel oxide layer in an electrolyte solution containing the nickel oxide layer. The thickness of the NiFe-containing layer and the proportion of Fe in the layer can be adjusted by adjusting the voltage application time.

[0043] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples, and the present invention can be modified appropriately without departing from the spirit and scope of the present invention.

[0044] [Examples 1 to 6 and Comparative Examples 1 and 2] Membrane electrode assemblies (MEAs) were manufactured having the layer configurations shown in Table 1. Figures 6(a) to 6(d) show SEM images of nickel foam 2 used in Example 2, which has metal fine particles on its surface and in its pores. In Figures 6(a) to 6(d), a layer of metal fine particles is observed stacked on the surface of a porous metal body having a skeleton of approximately several tens to several hundred micrometers. The details of each component in Table 1 are as follows. Ni Foam 1: A nickel foam (average pore size 35 μm, thickness 200 μm) having a nickel oxide layer containing NiOOH and a layer containing NiFe on the surface. The unmodified nickel foam is made of Celmet (registered trademark) Ni-#8 manufactured by Sumitomo Electric Industries, Ltd., which has been washed and compressed. Ni Foam 2: A nickel foam (average pore size 35 μm, thickness 200 μm) having nickel fine particles with an average particle size of 50 nm on the surface and within the pores. The nickel foam and nickel fine particles have a nickel oxide layer containing NiOOH and a layer containing NiFe on the surface. Celmet (registered trademark) Ni-#8 manufactured by Sumitomo Electric Industries, Ltd., which has been washed and compressed. Ni Foam 2 is formed by spraying an ink containing a mixture of nickel fine particles and an anion exchange polymer onto unmodified nickel foam. Metal fine particle layer: 1 mg / cm of nickel fine particles with an average particle size of 50 nm. ２A metal microparticle layer (approximately 3 μm thick) was deposited on the anion exchange membrane in an amount of 100 μm. The nickel microparticle layer was formed by spraying an ink containing nickel microparticles and an anion exchange polymer onto the surface of the anion exchange membrane. Ni fiber mat 1: A nickel fiber mat (sintered nickel fiber, average pore size 69 μm, thickness 200 μm) with a nickel oxide layer containing NiOOH and a layer containing NiFe on its surface. The unmodified nickel fiber mat was a cleaned 2Ni06-0.20 manufactured by Bekaert Toko Metal Fiber Co., Ltd. Ni fiber mat 2: A nickel fiber mat (sintered nickel fiber, average pore size 69 μm, thickness 200 μm) with nickel microparticles with an average particle size of 50 nm on its surface and within the pores. The nickel fiber mat and nickel microparticles had a nickel oxide layer containing NiOOH and a layer containing NiFe on their surface. Examples 4 to 6 had different amounts of nickel microparticles, as shown in Table 1. The unmodified nickel fiber mat used was a washed version of 2Ni06-0.20 manufactured by Bekaert Toko Metal Fiber Co., Ltd. Polymer 1: A polymer in which m is 10 and R is a trimethylammonium group in the formula (1). This is the same as polymer IV-C10-TMA obtained in Example 4 of Japanese Patent No. 7432918. Pt ３２．６ Ru １６．９ / C: A catalyst in which PtRu particles are supported on a carbon support at a weight ratio of Pt:Ru = 32.6:16.9. TEC66E50 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. is used. Carbon paper: SIGRACET GDL 29AA (thickness: approximately 190 μm) manufactured by SGL Carbon Co., Ltd.

[0045] <Water electrolysis test> Cell temperature: 80°C, 1M KOH aqueous solution (flow rate: 5 mL min) was added to the anode side. －１ ) was supplied to the cells, and the performance of the anion exchange membrane water electrolysis cells equipped with the MEAs of Examples 1 to 6 and Comparative Examples 1 and 2 was evaluated. A charge / discharge device (HJ1010SD8, manufactured by Hokuto Denko) was used for the cell evaluation. PFOTFPh-C10 was used as the ionomer contained in the electrolyte membrane and catalyst layer. The anion exchange membrane water electrolysis performance of the MEA is shown in Figures 7 and 8 (current-voltage curves). When the current density was 1, 2, and 4 A / cm ２The voltage required to achieve this is shown in Table 2. Fig. 7 shows the results of Comparative Example 1 and Examples 1 to 3, which used nickel foam, and Fig. 8 shows the results of Comparative Example 2 and Examples 4 to 6, which used nickel fiber mat.

[0046] In Comparative Example 1 and Examples 1 to 3, which used nickel foam, the MEAs of Examples 1 to 3, which contained nickel microparticles, had a lower voltage at a predetermined current density than the MEA of Comparative Example 1, and exhibited higher water electrolysis performance ( FIG. 7 and Table 2 ). In particular, it was shown that higher water electrolysis performance was obtained in Examples 2 and 3, in which nickel microparticles were introduced into nickel foam and Fe was electrodeposited. A similar trend was observed in Comparative Example 2 and Examples 4 to 6, which used a nickel fiber mat, and the MEAs of Examples 4 to 6, which contained nickel microparticles, exhibited higher water electrolysis performance than the MEA of Comparative Example 2 ( FIG. 8 and Table 2 ). It was shown that higher water electrolysis performance was obtained in Example 6, in which a larger amount of nickel microparticles was introduced.

[0047] The present disclosure provides a membrane electrode assembly with higher activity, a laminate suitable for the assembly, and a method for producing the same.

Claims

1. A laminate comprising a metal porous body on an electrolyte membrane, wherein the metal porous body has metal fine particles at least on the surface facing the electrolyte membrane and / or within the pores.

2. The laminate according to claim 1, wherein the average pore size of the porous metal body is 0.5 μm to 100 μm.

3. The laminate according to claim 1, wherein the average particle size of the metal particles is 5 nm to 200 nm.

4. The laminate according to claim 1, wherein the thickness of the porous metal body is 1 μm to 500 μm.

5. The laminate according to claim 1, further comprising a metal fine particle layer between the electrolyte membrane and the metal porous body.

6. The laminate according to claim 1, wherein the porous metal body is a metal foam or a metal fiber mat.

7. The laminate according to claim 1, wherein the porous metal body contains NiOOH.

8. The laminate according to claim 1, wherein the metal fine particles are fixed to the metal porous body.

9. The laminate according to claim 1, wherein the metal particles comprise NiOOH.

10. The laminate according to claim 1, wherein the porous metal body is a catalyst.

11. The laminate according to claim 1, wherein the electrolyte membrane is an anion-conducting membrane.

12. A membrane electrode assembly comprising the stack according to any one of claims 1 to 11 and a cathode disposed on the electrolyte membrane side of the stack.

13. A water electrolysis device comprising the membrane electrode assembly according to claim 12.

14. A method for producing a laminate according to any one of claims 1 to 11, comprising the steps of: (I) attaching metal fine particles to at least one surface and / or inside the pores of the metal porous body; and (II) placing the surface of the metal porous body to which the metal fine particles are attached on an electrolyte membrane and laminating the surface.

15. The method for producing a laminate according to claim 14, further comprising a step (III) between the steps (I) and (II) of catalyzing the porous metal body and the fine metal particles.

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