Membrane / catalyst layer structure, membrane / electrode assembly, fuel cell, water electrolysis cell, and water electrolysis device

Abstract

Provided is a membrane / catalyst layer structure that can maintain a good power generation performance or good electrolysis performance on a long-term basis. The membrane / catalyst layer structure has a first catalyst layer disposed opposite a second catalyst layer, and a diaphragm containing at least a polymer electrolyte membrane is sandwiched therebetween. The first catalyst layer and the second catalyst layer contain, as a first metal, the element platinum and / or the element iridium. The first catalyst layer and / or the second catalyst layer further contains, as a second metal, at least one element selected from the group consisting of gold, silver, copper, nickel, palladium, cobalt, rhodium, iron, ruthenium, and osmium. The diaphragm contains a compound N having a nitrogen-containing heterocycle.

Description

Membrane / catalyst layer structure, membrane / electrode assembly, fuel cell, water electrolysis cell, and water electrolysis device

[0001] The present invention relates to a membrane-catalyst layer structure, a membrane-electrode assembly, a fuel cell, a water electrolysis cell, and a water electrolysis device.

[0002] Fuel cells are a type of power generation device that generates electrical energy by electrochemically oxidizing fuels such as hydrogen and methanol, and are attracting attention as a clean energy source. Among these, polymer electrolyte fuel cells have a relatively low operating temperature and high energy density, and are therefore expected to be widely used as power generation devices for mobile vehicles such as automobiles and ships.

[0003] A polymer electrolyte fuel cell is composed of multiple cells in which an anode and a cathode are arranged facing each other with a membrane containing a polymer electrolyte membrane sandwiched therebetween, and generates electricity by supplying a fuel (hydrogen or methanol) to the anode and an oxidant gas (air or oxygen) to the cathode. In such polymer electrolyte fuel cells, an electrolyte membrane containing a nitrogen-containing heterocyclic compound has been proposed to suppress fuel crossover (for example, Patent Document 1).

[0004] On the other hand, in recent years, due to environmental issues such as global warming, hydrogen has been attracting attention as a clean energy source to replace fossil fuels. When hydrogen is burned, it basically only releases water, and does not emit carbon dioxide, which causes global warming, so it is expected to be a clean energy source. Hydrogen is mainly produced by electrolysis of water.

[0005] Alkaline water electrolysis and polymer electrolyte membrane (PEM) water electrolysis are known methods for producing hydrogen through water electrolysis. Among these, PEM water electrolysis has the advantage of being capable of operation at high current densities and being able to flexibly respond to fluctuations in renewable energy output.

[0006] The PEM water electrolysis method is a method in which water is supplied to a water electrolysis cell in which an anode and a cathode are arranged opposite each other with a membrane containing a polymer electrolyte membrane sandwiched therebetween, and oxygen is produced at the anode and hydrogen at the cathode.

[0007] It is known to use a fluorine-based polymer electrolyte or a hydrocarbon-based polymer electrolyte as the polymer electrolyte constituting the polymer electrolyte membrane, iridium as the anode catalyst, and platinum as the cathode catalyst (see, for example, Patent Documents 2 and 3).

[0008] JP-T-2019-507006 A JP-A-2023-112816 A JP-A-2018-159121 A

[0009] In the field of fuel cells, there is a demand for the ability to maintain relatively high power generation performance for a long period of time, but the techniques described in the above patent documents are still insufficient.

[0010] Meanwhile, in the field of water electrolysis, reduction in hydrogen production costs is required in order to popularize hydrogen energy. To reduce hydrogen production costs, it is effective to be able to maintain relatively high electrolysis performance for a long period of time using the same water electrolysis cell without replacing it. However, the technology described in the above patent documents is still insufficient.

[0011] In view of the above problems, an object of the present invention is to provide a membrane / catalyst layer assembly that can maintain good power generation performance or good electrolysis performance for a long period of time.

[0012] The above object of the present invention is achieved by the following invention: [1] A membrane-catalyst layer structure, in which a first catalyst layer and a second catalyst layer are disposed opposite each other with a membrane containing at least a polymer electrolyte membrane sandwiched therebetween, the first catalyst layer and the second catalyst layer contain platinum and / or iridium as a first metal, the first catalyst layer and / or the second catalyst layer further contain at least one element selected from the group consisting of gold, silver, copper, nickel, palladium, cobalt, rhodium, iron, ruthenium, and osmium as a second metal, and the membrane contains a compound N having a nitrogen-containing heterocycle.

[0013] [2] The membrane / catalyst layer construct according to [1], wherein the compound N having a nitrogen-containing heterocycle contains a nitrogen-containing aromatic five-membered ring or a nitrogen-containing aromatic six-membered ring.

[0014] [3] The membrane catalyst layer construct according to [1] or [2], wherein the compound N having a nitrogen-containing heterocycle contains a nitrogen-containing aromatic six-membered ring.

[0015] [4] The membrane / catalyst layer construct according to any one of [1] to [3], wherein the compound N having a nitrogen-containing heterocycle contains a plurality of nitrogen-containing aromatic 6-membered rings. [5] The membrane / catalyst layer construct according to any one of [1] to [4], wherein the compound N having a nitrogen-containing heterocycle is a compound selected from the group consisting of general formulae (D1), (D2), and (D3):

[0016]

[0017] In the formula, R １ represents at least one group selected from the group consisting of a divalent or higher hydrocarbon group, an amino group, a sulfide group, a ketone group, a sulfonyl group, a sulfone group, and an ether group; n １ Q １ each independently represents a 5- or 6-membered nitrogen-containing aromatic heterocycle, a fused ring of these nitrogen-containing aromatic heterocycles, or a fused ring of these nitrogen-containing aromatic heterocycles with a hydrocarbon aromatic ring, and these nitrogen-containing aromatic heterocycles and hydrocarbon aromatic rings may each be substituted with any substituent. １ represents an integer of 2 to 10.

[0018]

[0019] In the formula, R ２ represents at least one group selected from the group consisting of a hydrocarbon group, an amino group, a sulfide group, a ketone group, a sulfonyl group, a sulfone group, and an ether group, or a direct bond; Q ２ represents a group in which 1 to 5 five- or six-membered nitrogen-containing aromatic heterocycles, fused rings of these nitrogen-containing aromatic heterocycles, or fused rings of these nitrogen-containing aromatic heterocycles and hydrocarbon-based aromatic rings are linked together, and these nitrogen-containing aromatic heterocycles and hydrocarbon-based aromatic rings may each be substituted with any substituent. ２ represents an integer of 1 to 20. １ and X ２each independently represents at least one group selected from the group consisting of a hydrogen atom, a halogen, a hydrocarbon group, an alkoxy group, an aryloxy group, a carboxyl group, a carboxylate ester group, a phosphino group, a phosphine oxide group, a phosphonate group, a phosphate ester group, a sulfonate group, a sulfate ester group, a hydroxyl group, an amino group, a cyano group, and a nitro group.

[0020]

[0021] In the formula, R ３ represents C(R) or a nitrogen atom, R represents a hydrogen atom or an alkyl group, and Q ３ represents a 5- or 6-membered nitrogen-containing aromatic heterocycle, a fused ring of these nitrogen-containing aromatic heterocycles, or a fused ring of these nitrogen-containing aromatic heterocycles with a hydrocarbon aromatic ring, and these nitrogen-containing aromatic heterocycles and hydrocarbon aromatic rings may each be substituted with any substituent. g represents an integer of 5 to 500.

[0022] [6] The membrane catalyst layer structure according to any one of [1] to [5], wherein the first catalyst layer is an oxygen generating catalyst layer and contains iridium element as a first metal, and the second catalyst layer is a proton reducing catalyst layer and contains platinum element as a first metal.

[0023] [7] The membrane / catalyst layer structure according to any one of [1] to [5], wherein the first catalyst layer is an oxygen reduction catalyst layer and contains platinum element as a first metal, and the second catalyst layer is a hydrogen oxidation catalyst layer and contains platinum element as a first metal.

[0024] [8] The membrane-catalyst layer structure according to [6], wherein the second catalyst layer contains ruthenium as the second metal.

[0025] [9] The membrane-catalyst layer structure according to [6] or [8], wherein the second catalyst layer contains carbon particles carrying platinum or carbon particles carrying platinum and ruthenium.

[0026]

[10] The membrane-catalyst layer structure according to [8] or [9], wherein the second catalyst layer contains carbon particles carrying a platinum-ruthenium alloy.

[0027]

[11] The membrane catalyst layer structure according to any one of [1], [6], and [8] to

[10] , wherein the first catalyst layer contains iridium element as a first metal, and the iridium element contains iridium oxide.

[0028]

[12] The membrane-catalyst layer structure according to any one of [1] to

[11] , wherein the first catalyst layer and the second catalyst layer further contain a polymer electrolyte.

[0029]

[13] The membrane catalyst layer structure according to any one of [1], [6], and [8] to

[12] , wherein the first catalyst layer contains iridium element as a first metal and a polymer electrolyte, and the ratio (Ya) of the mass of the polymer electrolyte to the mass of the iridium element is 0.05 or more and less than 0.5; and the second catalyst layer contains platinum element as a first metal, ruthenium element as a second metal, and a polymer electrolyte, and the ratio (Yc) of the mass of the polymer electrolyte to the total mass of the platinum element and the ruthenium element is 0.25 or more and 1.1 or less.

[0030]

[14] The membrane catalyst layer structure according to

[13] , wherein the ratio (Ya) is smaller than the ratio (Yc).

[0031]

[15] The membrane-catalyst layer structure according to any one of [1] to

[14] , wherein the thickness of the first catalyst layer and / or the second catalyst layer is 25% or less relative to 100% of the thickness of the membrane.

[0032]

[16] The membrane-catalyst layer structure according to any one of [1] to

[15] , wherein the polymer electrolyte membrane contains a hydrocarbon-based polymer electrolyte.

[0033]

[17] The membrane catalyst layer structure according to [1] or [7], wherein the first catalyst layer is an anode catalyst layer and the second catalyst layer is a cathode catalyst layer.

[0034]

[18] A fuel cell comprising the membrane catalyst layer assembly according to any one of [1] to

[17] .

[0035]

[19] A water electrolysis device comprising the membrane catalyst layer structure according to any one of [1] to

[17] .

[0036]

[20] A membrane-electrode assembly comprising an electrode substrate disposed on each side of the membrane-catalyst layer structure according to any one of [1] to

[17] .

[0037]

[21] A fuel cell comprising the membrane-electrode assembly according to

[20] .

[0038]

[22] A water electrolysis cell comprising the membrane-electrode assembly according to

[20] .

[0039]

[23] A water electrolysis device comprising the water electrolysis cell according to

[22] .

[0040] The membrane catalyst layer structure of the present invention can maintain good electrolysis performance in a fuel cell for a long period of time, and can maintain good electrolysis performance in water electrolysis for a long period of time.

[0041] 1 is a cross-sectional view schematically illustrating an example of a water electrolysis cell of the present invention. FIG.

[0042] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments and can be implemented with various modifications depending on the purpose and application.

[0043] The membrane catalyst layer structure according to an embodiment of the present invention has a configuration in which a first catalyst layer and a second catalyst layer are disposed opposite each other with a membrane containing a polymer electrolyte membrane sandwiched therebetween. The membrane contains compound N having a nitrogen-containing heterocycle (hereinafter, may be simply referred to as "compound N"), and the first catalyst layer and the second catalyst layer each contain the following metals, which in combination enable the membrane to maintain good power generation performance or good electrolysis performance for a long period of time.

[0044] That is, the first catalyst layer and the second catalyst layer contain platinum and / or iridium as a first metal, and the first catalyst layer and / or the second catalyst layer further contain at least one element selected from the group consisting of gold, silver, copper, nickel, palladium, cobalt, rhodium, iron, ruthenium, and osmium as a second metal.

[0045] [Divider Membrane] The diaphragm includes at least a polymer electrolyte membrane. The polymer electrolyte membrane contains a polymer electrolyte. The diaphragm may be composed of only a polymer electrolyte membrane, or may have a laminated structure of a polymer electrolyte membrane and other layers. The other layers will be described in detail below. When the diaphragm has a laminated structure of a polymer electrolyte membrane and other layers, compound N can be contained in any one or more layers constituting the diaphragm. In the present invention, compound N is preferably contained in at least the polymer electrolyte membrane.

[0046] From the viewpoint of maintaining good power generation performance or electrolysis performance for a long period of time, the content of compound N in the diaphragm is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and particularly preferably 0.2 parts by mass or more, relative to 100 parts by mass of the polymer electrolyte contained in the diaphragm, and the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and particularly preferably 1 part by mass or less.

[0047] From the viewpoint of maintaining good power generation performance in the fuel cell for a long period of time, the thickness of the diaphragm is preferably 2 μm or more, more preferably 3 μm or more, and particularly preferably 4 μm or more, and is preferably 30 μm or less, more preferably 20 μm or less, and particularly preferably 15 μm or less.

[0048] On the other hand, from the viewpoint of maintaining good electrolysis performance for a long period of time during water electrolysis, the thickness of the diaphragm is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, and particularly preferably 50 μm or more. The thickness is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 180 μm or less, and particularly preferably 150 μm or less.

[0049] [Compound N] Preferred examples of the nitrogen-containing heterocycle constituting Compound N include nitrogen-containing aromatic heterocycles and nitrogen-containing aliphatic heterocycles. Among these, nitrogen-containing aromatic heterocycles are preferred.

[0050] Examples of nitrogen-containing aromatic heterocycles include pyridine rings, pyridazine rings, pyrimidine rings, pyrazine rings, triazine rings, pyrrole rings, pyrazole rings, imidazole rings, triazole rings, tetrazole rings, oxazole rings, oxadiazole rings, thiazole rings, thiadiazole rings, and selenazole rings. The nitrogen-containing aromatic heterocycles may be those in which the above-mentioned heterocycles are fused together, such as imidazopyridine and imidazopyrimidine, or those in which a nitrogen-containing aromatic heterocycle is fused with a hydrocarbon aromatic ring, such as benzimidazole, benzoxazole, benzthiazole, quinoline, quinoxaline, and phenanthroline. The hydrocarbon aromatic rings are preferably benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, and more preferably benzene rings.

[0051] Among the nitrogen-containing aromatic heterocycles, nitrogen-containing aromatic 5-membered rings and nitrogen-containing aromatic 6-membered rings are preferred, and nitrogen-containing aromatic 6-membered rings are particularly preferred.These nitrogen-containing aromatic 5-membered rings or nitrogen-containing aromatic 6-membered rings are more preferably fused with a hydrocarbon aromatic ring (e.g., a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring), and it is even more preferred that a nitrogen-containing aromatic 6-membered ring is fused with a hydrocarbon aromatic ring.It is particularly preferred that two nitrogen-containing aromatic 6-membered rings are fused with one hydrocarbon aromatic ring.The number of nitrogen-containing aromatic 6-membered rings constituting compound N is preferably 2 or more, more preferably 3 or more, and particularly preferably 4 or more.

[0052] The number of nitrogen-containing heterocycles in compound N is preferably 2 or more, more preferably 3 or more, and particularly preferably 4 or more. Moreover, the number is preferably 1,000 or less, more preferably 800 or less, and particularly preferably 500 or less. Compound N may be a non-polymer (low molecular weight) or a polymer (high molecular weight). When compound N is a non-polymer, the number of nitrogen-containing heterocycles is preferably less than 30, preferably 20 or less, and particularly preferably 15 or less. When compound N is a polymer, the number of nitrogen-containing heterocycles is preferably 30 or more, preferably 40 or more, and particularly preferably 50 or more.

[0053] In water electrolysis, from the viewpoint of maintaining good electrolysis performance for a longer period of time, compound N that is not easily eluted from the diaphragm during water electrolysis operation can also be suitably used. From this viewpoint, compound N used in water electrolysis preferably has a relatively large molecular weight, specifically, preferably 200 or more, more preferably 300 or more, and particularly preferably 400 or more. Furthermore, compound N is preferably easily mixed with the polymer electrolyte during preparation of the diaphragm, and from this viewpoint, compound N has a molecular weight of preferably 200,000 or less, more preferably 150,000 or less, and particularly preferably 100,000 or less. Here, when compound N is a polymer, the molecular weight means the number average molecular weight.

[0054] Compound N is preferably a compound represented by the following general formula (D1), (D2) or (D3).

[0055]

[0056] R １ represents at least one group selected from the group consisting of a divalent or higher hydrocarbon group, an amino group, a sulfide group, a ketone group, a sulfonyl group, a sulfone group, and an ether group; n １ Q １ each independently represents a 5- or 6-membered nitrogen-containing aromatic heterocycle, a fused ring of these nitrogen-containing aromatic heterocycles, or a fused ring of these nitrogen-containing aromatic heterocycles with a hydrocarbon aromatic ring, and these nitrogen-containing aromatic heterocycles and hydrocarbon aromatic rings may each be substituted with any substituent. １ represents an integer of 2 to 10.

[0057]

[0058] R ２ represents at least one group selected from the group consisting of a hydrocarbon group, an amino group, a sulfide group, a ketone group, a sulfonyl group, a sulfone group, and an ether group, or a direct bond; Q ２represents a group in which 1 to 5 five- or six-membered nitrogen-containing aromatic heterocycles, fused rings of these nitrogen-containing aromatic heterocycles, or fused rings of these nitrogen-containing aromatic heterocycles and hydrocarbon-based aromatic rings are linked together, and these nitrogen-containing aromatic heterocycles and hydrocarbon-based aromatic rings may each be substituted with any substituent. ２ represents an integer of 1 to 20. １ and X ２ each independently represents at least one group selected from the group consisting of a hydrogen atom, a halogen, a hydrocarbon group, an alkoxy group, an aryloxy group, a carboxyl group, a carboxylate ester group, a phosphino group, a phosphine oxide group, a phosphonate group, a phosphate ester group, a sulfonate group, a sulfate ester group, a hydroxyl group, an amino group, a cyano group, and a nitro group.

[0059]

[0060] R ３ represents C(R) or a nitrogen atom, R represents a hydrogen atom or an alkyl group, and Q ３ represents a 5- or 6-membered nitrogen-containing aromatic heterocycle, a fused ring of these nitrogen-containing aromatic heterocycles, or a fused ring of these nitrogen-containing aromatic heterocycles with a hydrocarbon aromatic ring, and these nitrogen-containing aromatic heterocycles and hydrocarbon aromatic rings may each be substituted with any substituent. g represents an integer of 5 to 500.

[0061] In the general formulas (D1) and (D2), the amino group represents a primary to tertiary amino group or a quaternary ammonium cation, and the bonding site with a valency of i (i=1 to 3) or more means that the unit has i or more bonding sites capable of bonding to other structural units.

[0062] Also, R １ , R ２ , X １ , X ２ Examples of the hydrocarbon group represented by the general formula C ｍ H ｎ(m and n represent integers, and m is preferably 1 to 20) and may be a hydrocarbon group having a linear, cyclic, or branched structure. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, but an aromatic hydrocarbon group is preferred. The hydrocarbon group may be substituted with any substituent.

[0063] In the description of all the above groups, the "optional substituent" is not particularly limited, but is preferably a halogen, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, a carboxyl group, a carboxylate ester group, a phosphino group, a phosphine oxide group, a phosphonate group, a phosphate ester group, a sulfonate group, a sulfate ester group, a hydroxyl group, an amino group, a cyano group, or a nitro group.

[0064] Examples of the compound represented by the general formula (D1) are shown below, but the compound is not limited to these.

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] Among the compounds represented by the above general formula (D1), compounds having a nitrogen-containing aromatic 6-membered ring are preferred, and compounds represented by the following general formula (D1a) are more preferred.

[0074]

[0075] In general formula (D1a), Ar １ represents a k-valent arylene group, R ４each independently represents at least one group selected from a halogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a carboxyl group, a carboxylate group, a phosphino group, a phosphine oxide group, a phosphonate group, a phosphate group, a sulfonate group, a sulfate group, a hydroxyl group, an amino group, a cyano group, and a nitro group. j represents an integer of 0 to 7, and k represents an integer of 2 or more.

[0076] Next, examples of the compound represented by the above general formula (D2) are shown below, but the invention is not limited to these.

[0077]

[0078]

[0079]

[0080]

[0081] Among the compounds represented by the above general formula (D2), compounds having a nitrogen-containing aromatic six-membered ring are preferred, and compounds represented by the following general formula (D2a) are more preferred.

[0082]

[0083] In general formula (D2a), Ar ２ represents an arylene group, R ５ each independently represents at least one group selected from the group consisting of a halogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a carboxyl group, a carboxylate ester group, a phosphino group, a phosphine oxide group, a phosphonic acid group, a phosphate ester group, a sulfonic acid group, a sulfate ester group, a hydroxyl group, an amino group, a cyano group, and a nitro group; X ３ and X ４each independently represents at least one group selected from the group consisting of a hydrogen atom, a halogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a carboxyl group, a carboxylate group, a phosphino group, a phosphine oxide group, a phosphonate group, a phosphate group, a sulfonate group, a sulfate group, a hydroxyl group, an amino group, a cyano group, and a nitro group. m represents an integer of 0 to 6, and n ３ represents an integer of 2 or more and 4 or less.) Next, examples of the compound represented by general formula (D3) are shown below, but the compound is not limited to these.

[0084]

[0085] Compound N may be any compound having a nitrogen-containing heterocycle, even if it does not fall into any of the general formulae (D1), (D2), and (D3). Examples of such compounds include, but are not limited to, the following: (H1) 1,10-phenanthroline (H2) 5-amino-1,10-phenanthroline (H3) polybenzimidazole (PBI).

[0086] The polybenzimidazole (PBI) includes all compounds having a benzimidazole structure in the main chain. The PBI is preferably represented by the following formula (H3):

[0087]

[0088] Furthermore, as compound N, a macrocyclic compound can be suitably used as a compound that does not fall under any of general formulas (D1), (D2), and (D3). Examples of macrocyclic compounds include compounds having a corrin skeleton, a porphyrin skeleton, or a phthalocyanine skeleton, and compounds having an azacalixarene skeleton. Specific examples include, but are not limited to, corrin, porphyrin, protoporphyrin, phthalocyanine, corrole, chlorin, bacteriochlorin, coproporphyrinogen I, coproporphyrinogen III, uroporphyrinogen I, uroporphyrinogen III, protoporphyrinogen IX, and azacalixarene. Among these, corrin, porphyrin, phthalocyanine, and azacalixarene are preferred, and porphyrin and phthalocyanine are more preferred.

[0089] [Polymer Electrolyte Membrane] The polymer electrolyte membrane contains a polymer electrolyte as described above. In the present invention, the polymer electrolyte membrane means a membrane containing 50% by mass or more of the polymer electrolyte relative to 100% by mass of the total solid content of the polymer electrolyte membrane. The content of the polymer electrolyte is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0090] Preferred examples of the polymer electrolyte in the present invention include a fluorine-based polymer electrolyte, a hydrocarbon-based polymer electrolyte, etc. In the present invention, the polymer electrolyte membrane preferably contains a hydrocarbon-based polymer electrolyte.

[0091] The fluorine-based polymer electrolyte is preferably a fluorine-based polymer having an ionic group, which means a polymer in which most or all of the hydrogen atoms in the alkyl and / or alkylene groups in the molecule are substituted with fluorine atoms.

[0092] Preferred examples of the fluorine-based polymer electrolyte include perfluorocarbon sulfonic acid polymers, perfluorocarbon phosphonic acid polymers, trifluorostyrene sulfonic acid polymers, trifluorostyrene phosphonic acid polymers, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymers, ethylene-tetrafluoroethylene copolymers, and polyvinylidene fluoride-perfluorocarbon sulfonic acid polymers.

[0093] Among these, perfluorocarbon sulfonic acid polymers are preferred from the viewpoint of heat resistance and chemical stability, and examples of such polymers include commercially available products such as "Nafion" (registered trademark) (manufactured by Chemours), "Flemion" (registered trademark) (manufactured by AGC Inc.), and "Aciplex" (registered trademark) (manufactured by Asahi Kasei Corporation).

[0094] Preferred examples of hydrocarbon-based polymer electrolytes include hydrocarbon-based polymers having ionic groups. A hydrocarbon-based polymer refers to a polymer having a main chain whose main structural unit is hydrocarbon. Preferred examples of the hydrocarbon-based polymer include aromatic hydrocarbon-based polymers having an aromatic ring in the main chain. That is, among hydrocarbon-based polymer electrolytes, aromatic hydrocarbon-based polymer electrolytes are preferred.

[0095] Preferred examples of the aromatic hydrocarbon polymer include polymers having, in the main chain, an aromatic ring and a structure selected from polysulfone, polyethersulfone, polyphenylene oxide, polyarylene ether, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymer, polyarylene ketone, polyether ketone, polyarylene phosphine oxide, polyether phosphine oxide, polybenzoxazole, polybenzothiazole, polybenzimidazole, polyamide, polyimide, polyetherimide, and polyimide sulfone.

[0096] The polysulfone is a general term for a structure having a sulfone bond in the molecular chain, the polyethersulfone is a general term for a structure having an ether bond and a sulfone bond in the molecular chain, and the polyetherketone is a general term for a structure having an ether bond and a ketone bond in the molecular chain. The aromatic hydrocarbon polymer may have a plurality of these structures.

[0097] As the aromatic hydrocarbon polymer, a polyetherketone polymer is particularly preferred. Preferred examples of the polyetherketone polymer include polyetherketone, polyetherketoneketone, polyetheretherketone, polyetheretherketoneketone, and polyetherketoneetherketoneketone.

[0098] Furthermore, among aromatic hydrocarbon polymers, block copolymers are preferred. Here, the term "block copolymer" refers to a block copolymer of a segment containing a structural unit containing an ionic group and a segment containing a structural unit not containing an ionic group.

[0099] The ionic group may be an ionic group having either cation exchange ability or anion exchange ability, but in the present invention, it is preferable to use a proton-exchangeable ionic group. Examples of such functional groups include a sulfonic acid group, a sulfonimide group, a sulfate group, a phosphonic acid group, a phosphate group, a carboxylic acid group, an ammonium group, a phosphonium group, and an amino group. Two or more types of ionic groups can be contained in the polymer. Among them, a sulfonic acid group, a sulfonimide group, and a sulfate group are preferred because of their excellent water electrolysis performance, and a sulfonic acid group is more preferred from the viewpoint of raw material costs.

[0100] As described above, it is preferable to use an aromatic hydrocarbon-based block copolymer as the polymer electrolyte, and it is more preferable to use a polyetherketone-based block copolymer. As the polyetherketone-based block copolymer, it is particularly preferable to use one that contains a segment containing a structural unit (S1) containing an ionic group as shown below and a segment containing a structural unit (S2) that does not contain an ionic group.

[0101]

[0102] In general formula (S1), Ar １１ ~Ar １４ represents any divalent arylene group, Ar １１ and / or Ar １２ contains an ionic group, and Ar １３ and Ar １４ may or may not contain an ionic group. １１ ~Ar １４ may be optionally substituted, and two or more types of arylene groups may be used independently. * represents a bonding site to general formula (S1) or other structural units.

[0103]

[0104] In general formula (S2), Ar １５ ~Ar １８ represents any divalent arylene group, which may be optionally substituted but does not contain an ionic group. １５ ~Ar １８ may independently use two or more types of arylene groups. * represents a bonding site with general formula (S2) or another structural unit.

[0105] Here, Ar １１ ~Ar １８ Preferred divalent arylene groups as Ar include hydrocarbon arylene groups such as phenylene, naphthylene, biphenylene, and fluorenediyl groups, and heteroarylene groups such as pyridinediyl, quinoxalinediyl, and thiophenediyl, but are not limited thereto. Here, the term "phenylene group" can be classified into three types, namely, o-phenylene, m-phenylene, and p-phenylene, depending on the bonding site between the benzene ring and other structural units, and unless otherwise specified, the term will be used as a general term for these in the present specification. The same applies to other divalent arylene groups such as "naphthylene" and "biphenylene". Ar １１ ~Ar １４ is preferably a phenylene group and a phenylene group containing an ionic group, and most preferably a p-phenylene group and a p-phenylene group containing an ionic group.１５ ~Ar １８ may be substituted with a group other than an ionic group, but is preferably unsubstituted in terms of proton conductivity, chemical stability, and physical durability.

[0106] The ion exchange capacity (IEC) of the polymer electrolyte is preferably 0.5 meq / g or more and 3.5 meq / g or less. From the viewpoint of obtaining good electrolysis performance and good power generation performance, in the case of a hydrocarbon-based polymer electrolyte, the IEC is more preferably 1.0 meq / g or more and 3.5 meq / g or less, even more preferably 1.4 meq / g or more and 3.0 meq / g or less, and particularly preferably 1.6 meq / g or more and 2.7 meq / g or less. In the case of a fluorine-based polymer electrolyte, the IEC is more preferably 0.5 meq / g or more and 2.0 meq / g or less, even more preferably 0.7 meq / g or more and 1.7 meq / g or less, and particularly preferably 0.8 meq / g or more and 1.5 meq / g or less.

[0107] Here, IEC is the molar amount of ionic groups introduced per unit dry weight of the polymer electrolyte P, and a larger value indicates a larger amount of ionic groups introduced. In the present invention, IEC is defined as a value determined by neutralization titration.

[0108] In order to obtain better electrolysis performance and better power generation performance, the polymer electrolyte constituting the polymer electrolyte membrane preferably has an IEC of 1.6 meq / g or more, more preferably 1.7 meq / g or more, and particularly preferably 1.8 meq / g or more. In terms of durability, the IEC of the polymer electrolyte is preferably 3.0 meq / g or less, more preferably 2.7 meq / g or less, and particularly preferably 2.5 meq / g or less.

[0109] Among the above-mentioned polymer electrolytes, hydrocarbon-based polymer electrolytes are preferred because of their high electrolytic performance and power generation performance. Among hydrocarbon-based polymer electrolytes, aromatic hydrocarbon-based polymer electrolytes are preferred, and polyether ketone-based block copolymers are particularly preferred.

[0110] The content of the hydrocarbon-based polymer electrolyte is preferably 60% by mass or more, more preferably 75% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass, relative to the total mass (100% by mass) of the polymer electrolyte contained in the polymer electrolyte membrane.

[0111] The polymer electrolyte membrane may be composed of multiple layers. When the polymer electrolyte membrane is composed of multiple layers, the polymer electrolytes contained in each layer may have the same or different structures. Examples of the multiple layers include a laminated structure of a layer containing a hydrocarbon-based polymer electrolyte and a layer containing a fluorine-based polymer electrolyte, and a structure in which a non-composite layer containing a polymer electrolyte but not a porous substrate is provided on one or both sides of a composite layer containing a porous substrate and a polymer electrolyte. The composite layer is a layer in which the pores of the porous substrate are filled with a polymer electrolyte. Examples of the porous substrate include woven fabric, nonwoven fabric, porous film, and mesh fabric.

[0112] The thickness ratio of the composite layer is preferably 10 to 90%, more preferably 20 to 80%, and particularly preferably 30 to 70%, relative to the thickness of the polymer electrolyte membrane (100%). Here, the thickness of the composite layer refers to the thickness of the porous substrate. In an electrolyte membrane used for water electrolysis, the specific thickness of the composite layer is preferably in the range of 22 to 47 μm, more preferably 25 to 45 μm, and particularly preferably 30 to 43 μm. Furthermore, the thickness of each non-composite layer is preferably 3 μm or more, more preferably 5 μm or more, and particularly preferably 10 μm or more. Furthermore, the thickness of each non-composite layer is preferably 45 μm or less, more preferably 40 μm or less, and particularly preferably 35 μm or less.

[0113] When the polymer electrolyte membrane is composed of multiple layers, it may be configured such that all layers contain compound N, or such that some layers contain compound N. In the latter configuration, it is preferable that compound N is contained at least in the layer closest to the cathode catalyst layer.

[0114] The polymer electrolyte membrane may contain various additives, such as antioxidants, surfactants, radical scavengers, hydrogen peroxide decomposers, non-electrolytic polymers, elastomers, and fillers, as long as they do not impair the effects of the present invention.

[0115] From the viewpoint of maintaining good electrolysis performance in water electrolysis for a long period of time, the thickness of the polymer electrolyte membrane is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, and particularly preferably 50 μm or more. The thickness is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 180 μm or less, and particularly preferably 150 μm or less.

[0116] [Other Layers] The membrane may contain layers other than the polymer electrolyte membrane. Here, the other layers refer to layers in which the polymer electrolyte content is less than 50% by mass relative to 100% by mass of the total solid content of the other layers. The other layers are not particularly limited, and include various functional layers. Examples include a protective layer (protecting the polymer electrolyte membrane), an adhesive layer (strengthening the adhesion between the polymer electrolyte membrane and the catalyst layer), and a gas transfer suppression layer (decomposing or capturing gases such as hydrogen, oxygen, and hydrogen peroxide). The other layers may also be layers for incorporating compound N into the membrane. The other layers may contain a polymer electrolyte to the extent that their functions are not impaired.

[0117] When other layers are provided, the thickness thereof is preferably in the range of 0.1 to 30 μm, more preferably in the range of 0.5 to 20 μm, and particularly preferably in the range of 1 to 15 μm.

[0118] [Catalyst Layer] A membrane-catalyst layer structure according to an embodiment of the present invention has a first catalyst layer disposed on one surface of a membrane and a second catalyst layer disposed on the other surface of the membrane, wherein the first catalyst layer and the second catalyst layer contain platinum and / or iridium as a first metal, and the first catalyst layer and / or the second catalyst layer further contains at least one element selected from the group consisting of gold, silver, copper, nickel, palladium, cobalt, rhodium, iron, ruthenium, and osmium as a second metal.

[0119] In the fuel cell, it is preferable that the first catalyst layer functions as an oxygen reduction catalyst layer and the second catalyst layer functions as a hydrogen oxidation catalyst layer. It is also preferable that the first catalyst layer (oxygen reduction catalyst layer) contains platinum as a first metal, and the second catalyst layer (hydrogen oxidation catalyst layer) contains platinum as a first metal. Furthermore, it is preferable that the first catalyst layer and / or the second catalyst layer contain at least one element selected from the group consisting of cobalt, nickel, and ruthenium as a second metal.

[0120] In water electrolysis, it is preferable that the first catalytic layer functions as an oxygen generating catalytic layer and the second catalytic layer functions as a proton reducing catalytic layer. It is also preferable that the first catalytic layer (oxygen generating catalytic layer) contains iridium as a first metal, and the second catalytic layer (proton reducing catalytic layer) contains platinum as a first metal. It is more preferable that the second catalytic layer contains ruthenium as a second metal.

[0121] The catalytic layers used in water electrolysis are described in detail below. In water electrolysis, the first catalytic layer (oxygen generating catalytic layer) corresponds to the anode catalytic layer, and the second catalytic layer (proton reducing catalytic layer) corresponds to the cathode catalytic layer. Hereinafter, the first catalytic layer may be referred to as the "anode catalytic layer" and the second catalytic layer as the "cathode catalytic layer."

[0122] [Anode catalyst layer (first catalyst layer)] In water electrolysis, the anode electrolyzes water to produce oxygen and protons, and therefore the anode catalyst is sometimes called an oxygen-evolving catalyst. The anode catalyst layer preferably contains iridium as the first metal. Iridium is useful as an oxygen-evolving catalyst. That is, the anode catalyst layer improves electrolysis performance by containing iridium as a catalyst.

[0123] As the catalyst containing iridium element, zero-valent iridium, iridium oxide, iridium carbide, iridium nitride, etc. can be used, but iridium oxide is preferred from the viewpoint of maintaining good electrolytic performance for a longer period of time. The catalyst containing iridium element is preferably in the form of particles.

[0124] The catalyst containing iridium element may be catalyst-supported particles supported on a support made of a metal oxide such as titanium oxide, tin oxide, tantalum oxide, niobium oxide, zirconium oxide, or tungsten oxide. Because the anode in water electrolysis is in a high-potential environment, a support having relatively high electrochemical oxidation resistance is preferred. In this regard, the above-mentioned metal oxides are preferred because of their relatively high electrochemical oxidation resistance.

[0125] As the catalyst containing iridium element, it is preferable to use particles containing iridium element alone, or catalyst-supported particles supported on a carrier made of metal oxide, and among these, it is particularly preferable to use particles containing iridium element alone.

[0126] On the other hand, carbon particles such as carbon black are generally known as supports for catalyst-supported particles, but in water electrolysis, it is preferable to reduce the content of carbon particles from the viewpoint of durability of the anode catalyst layer. Here, carbon particles include spherical, flat, and fibrous substances. The content of carbon particles in the anode catalyst layer is 0.1 mg / cm. ２ Preferably less than 0.05 mg / cm ２ More preferably, less than 0.02 mg / cm ２ It is more preferable that the content is less than 100%, and it is particularly preferable that the content is zero.

[0127] The content of iridium element in the anode catalyst layer is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 70 mass% or more, and particularly preferably 80 mass% or more, relative to the total elemental amount (100 mass%) of all metal catalysts contained in the anode catalyst layer, with the upper limit being preferably 100 mass% or less.

[0128] The anode catalyst layer can contain platinum elemental as the first metal in addition to iridium elemental. In water electrolysis, the back diffusion of hydrogen produced at the cathode causes hydrogen to be mixed with oxygen produced at the anode, which can lead to the risk of explosion. However, platinum elemental functions as a catalyst for producing water from hydrogen and oxygen, thereby avoiding the risk of explosion. Furthermore, some second metals also function as catalysts for producing water from hydrogen and oxygen. Examples include noble metal elements such as ruthenium, rhodium, palladium, gold, silver, and osmium. Among these noble metal elements, palladium is more preferred. Catalysts containing platinum elemental and the above noble metal elements include zero-valent catalysts, oxides, carbides, nitrides, etc., respectively. Among these, zero-valent catalysts are preferred.

[0129] When the anode catalyst layer contains platinum and / or the noble metal element in addition to iridium, the content of platinum and / or the noble metal element is preferably in the range of 1 to 90 parts by mass, more preferably 5 to 80 parts by mass, and particularly preferably 10 to 50 parts by mass, per 100 parts by mass of iridium.

[0130] In the anode catalyst layer, the mass of iridium element per unit area is 0.2 to 2.0 mg / cm ２ The range is preferably 0.4 to 1.5 mg / cm ２ The range of 0.6 to 1.3 mg / cm is more preferable. ２ The range is particularly preferred.

[0131] The anode catalyst layer preferably further contains a polymer electrolyte. The aforementioned hydrocarbon-based polymer electrolyte or fluorine-based polymer electrolyte can be used as the polymer electrolyte. Because the anode is in a high-potential environment in a water electrolysis device, it is preferable to use a fluorine-based polymer electrolyte, which has relatively good resistance to electrochemical oxidation, and a perfluorocarbon sulfonic acid-based polymer is more preferable.

[0132] When the anode catalyst layer contains a polymer electrolyte, the ratio (Ya) of the mass of the polymer electrolyte in the anode catalyst layer to the mass of elemental iridium, i.e., (mass of polymer electrolyte) / (mass of elemental iridium), is preferably 0.05 or more, more preferably 0.07 or more, and particularly preferably 0.1 or more, from the viewpoint of electrolysis performance. Furthermore, from the viewpoint of diffusibility of oxygen gas generated at the anode, this ratio is preferably less than 0.5, more preferably less than 0.4, even more preferably less than 0.3, and particularly preferably less than 0.25.

[0133] The thickness of the anode catalyst layer is preferably 0.5 μm or more, more preferably 1 μm or more, and particularly preferably 3 μm or more from the viewpoint of electrolysis performance, and is preferably 25 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, and particularly preferably 10 μm or less from the viewpoint of diffusibility of oxygen gas generated at the anode and physical stability (such as cracking during operation).

[0134] [Cathode catalyst layer (second catalyst layer)] In water electrolysis, the cathode reduces protons produced at the anode to produce hydrogen, and therefore the cathode catalyst is sometimes called a proton reduction catalyst. The cathode catalyst layer preferably contains platinum element as the first metal. Platinum element is useful as a proton reduction catalyst.

[0135] The cathode catalyst layer preferably further contains ruthenium as a second metal. By containing platinum and ruthenium as catalysts, the cathode catalyst layer can maintain good electrolysis performance for an even longer period of time. From the viewpoint of maintaining good water electrolysis performance for an even longer period of time, the mass ratio of platinum (Pt) to ruthenium (Ru) (Ru / Pt) is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, and particularly preferably 0.4 or more. Furthermore, this mass ratio is preferably 2.0 or less, more preferably 1.7 or less, even more preferably 1.5 or less, and particularly preferably 1.3 or less. Meanwhile, the mass ratio of Pt to the total mass of Pt and Ru, "Pt / (Pt+Ru)," is preferably 0.40 or more, more preferably 0.50 or more, and particularly preferably 0.60 or more, from the viewpoint of water electrolysis performance. The mass ratio "Pt / (Pt+Ru)" is preferably 0.90 or less, more preferably 0.80 or less, and particularly preferably 0.75 or less.

[0136] In the cathode catalyst layer, the platinum-containing catalyst and the ruthenium-containing catalyst may be used alone, or a platinum-ruthenium alloy may be used, or platinum and ruthenium may be supported on carbon particles. Hereinafter, platinum supported on carbon particles will be referred to as "platinum-supported carbon particles," ruthenium supported on carbon particles will be referred to as "ruthenium-supported carbon particles," platinum and ruthenium supported on carbon particles will be referred to as "platinum-ruthenium-supported carbon particles," and platinum-ruthenium alloy supported on carbon particles will be referred to as "platinum-ruthenium alloy-supported carbon particles." These are collectively referred to as "platinum catalyst, etc.-supported carbon particles."

[0137] Examples of the carbon particles include carbon black such as furnace black, acetylene black, and ketjen black, and graphitized carbon blacks. When using the platinum or other catalyst-supporting carbon particles, the platinum or other catalyst-supporting carbon particles should have a BET specific surface area of ​​400 m or less from the viewpoint of the physical strength and durability of the cathode catalyst layer. ２ / g or less is preferable, and 300m ２ / g or less is more preferable, and 200m ２ / g or less is more preferable, and 150m ２ The BET specific surface area is particularly preferably 30 m / g or less. ２ / g or more is preferable, and 50m ２ / g or more is more preferable, and 70m ２ / g or more is particularly preferred.

[0138] From the viewpoint of obtaining better electrolysis performance, the catalyst used in the cathode catalyst layer is preferably a platinum or other catalyst-supported carbon particle, more preferably a platinum-ruthenium-supported carbon particle, and from the viewpoint of maintaining good electrolysis performance for a longer period of time, the catalyst used in the cathode catalyst layer is preferably a platinum-ruthenium alloy-supported carbon particle.

[0139] The catalytic element loading rate in the platinum or other catalyst-supporting carbon particles (ratio of the mass of the catalytic element to the mass of the platinum or other catalyst-supporting carbon particles) is preferably in the range of 20 to 70 mass%, more preferably in the range of 30 to 65 mass%, and particularly preferably in the range of 35 to 60 mass%.

[0140] In the cathode catalyst layer, the mass of platinum element per unit area is 0.05 mg / cm from the viewpoint of electrolysis performance. ２ More than 0.1 mg / cm is preferred. ２ More preferably, 0.2 mg / cm or more ２ From the viewpoint of cost, the mass of the platinum element is preferably 1.0 mg / cm. ２ Preferably less than 0.7 mg / cm ２ More preferably, less than 0.5 mg / cm ２ Less than 1000 is particularly preferred.

[0141] On the other hand, the mass of ruthenium element per unit area is set to 0.03 mg / cm from the viewpoint of maintaining good electrolytic performance for a long period of time. ２ More than 0.05 mg / cm ２ More preferably, 0.1 mg / cm ２ More preferably, the content is 0.8 mg / cm or more. ２ Preferably less than 0.6 mg / cm ２ More preferably, less than 0.4 mg / cm ２ Less than 1000 is particularly preferred.

[0142] The cathode catalyst layer preferably further contains a polymer electrolyte. The aforementioned hydrocarbon-based polymer electrolytes and fluorine-based polymer electrolytes can be used as the polymer electrolyte. Among these, fluorine-based polymer electrolytes are preferred, with perfluorocarbon sulfonic acid polymers being more preferred. It is more preferred that both the anode catalyst layer and the cathode catalyst layer contain a polymer electrolyte.

[0143] When the cathode catalyst layer contains a polymer electrolyte, the ion exchange capacity (IEC) of the polymer electrolyte is preferably less than 1.50 meq / g, more preferably less than 1.40 meq / g, and particularly preferably less than 1.30 meq / g. The lower limit is preferably 0.40 meq / g or more.

[0144] From the viewpoint of electrolysis performance, the ion exchange capacity (hereinafter referred to as "IEC") of the polymer electrolyte contained in the cathode catalyst layer is ＣＡ ") is the ion exchange capacity (hereinafter referred to as "IEC") of the polymer electrolyte contained in the polymer electrolyte membrane. ＰＥ ") is preferably smaller than the IEC ＣＡ and IEC ＰＥ Ratio to (IEC ＣＡ / IEC ＰＥ ) is preferably 0.90 or less, more preferably 0.80 or less, even more preferably 0.70 or less, and particularly preferably 0.65 or less. ＣＡ / IEC ＰＥ ) is preferably 0.20 or more, more preferably 0.30 or more, even more preferably 0.35 or more, and particularly preferably 0.40 or more.

[0145] When the cathode catalyst layer contains a polymer electrolyte, the ratio (Yc) of the mass of the polymer electrolyte in the cathode catalyst layer to the total mass of platinum and ruthenium, i.e., (mass of polymer electrolyte) / (mass of platinum + mass of ruthenium), is preferably 0.25 or more, more preferably 0.40 or more, even more preferably 0.50 or more, and particularly preferably 0.60 or more, from the viewpoint of electrolysis performance. Furthermore, from the viewpoint of diffusibility of hydrogen gas generated at the cathode, this ratio is preferably 1.1 or less, more preferably 1.0 or less, and particularly preferably 0.9 or less.

[0146] It is particularly preferable that the ratio (Ya) is 0.05 or more and less than 0.5, and the ratio (Yc) is 0.425 or more and 1.1 or less. Furthermore, it is more preferable that the ratio (Ya) is smaller than the ratio (Yc).

[0147] The thickness of the cathode catalyst layer is preferably 0.5 μm or more, more preferably 1 μm or more, and particularly preferably 3 μm or more from the viewpoint of electrolysis performance, and is preferably 25 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, and particularly preferably 10 μm or less from the viewpoint of diffusibility of hydrogen gas generated at the cathode and physical stability of the catalyst layer (e.g., cracking during operation).

[0148] [Membrane-catalyst layer structure] A membrane-catalyst layer structure according to an embodiment of the present invention has an anode catalyst layer (first catalyst layer) disposed on one surface of a membrane, and a cathode catalyst layer (second catalyst layer) disposed on the other surface.

[0149] The membrane catalyst layer structure according to the embodiment of the present invention can be obtained, for example, by laminating an anode catalyst layer and a cathode catalyst layer on a diaphragm, but the membrane catalyst layer structure of the present invention can also be completed during the assembly process of a membrane electrode assembly, which will be described later in detail.

[0150] From the viewpoint of adhesion between the membrane and the catalyst layer, it is preferable that both the anode catalyst layer and the cathode catalyst layer are laminated on the membrane. Hereinafter, the anode catalyst layer and the cathode catalyst layer may be collectively referred to as the "catalyst layer."

[0151] The method for laminating a catalyst layer on a membrane may be, for example, a coating method, a transfer method, or a combination of a coating method and a transfer method. These methods are not particularly limited, and any known method may be used.

[0152] The coating method is a method in which a coating liquid for a catalyst layer is applied to a membrane by a known coating method, and the transfer method is a method in which a catalyst layer transfer sheet, in which a catalyst layer is laminated on a transfer substrate, and the membrane are overlapped and hot-pressed.

[0153] In the membrane catalyst layer structure according to an embodiment of the present invention, the thicknesses of the diaphragm, anode catalyst layer, and cathode catalyst layer are as described above, but from the viewpoint of maintaining good electrolysis performance for a longer period of time, it is preferable to adjust the relationship between these thicknesses. For example, it is preferable that the thickness of the anode catalyst layer and / or the cathode catalyst layer is each 25% or less of the 100% thickness of the diaphragm. The thickness of the anode catalyst layer is preferably 25% or less, more preferably 20% or less, and particularly preferably 15% or less of the 100% thickness of the diaphragm. The lower limit is preferably 1% or more. The thickness of the cathode catalyst layer is preferably 25% or less, more preferably 20% or less, and particularly preferably 15% or less of the 100% thickness of the diaphragm. The lower limit is preferably 1% or more.

[0154] From the same viewpoint as above, the thickness of the anode catalyst layer is preferably 25% or less, more preferably 20% or less, and particularly preferably 15% or less, relative to 100% of the thickness of the polymer electrolyte membrane. The lower limit is preferably 1% or more. The thickness of the cathode catalyst layer is preferably 25% or less, more preferably 20% or less, and particularly preferably 15% or less, relative to 100% of the thickness of the polymer electrolyte membrane. The lower limit is preferably 1% or more.

[0155] [Membrane Electrode Assembly (MEA)] The membrane catalyst layer structure according to the embodiment of the present invention becomes a membrane electrode assembly by disposing electrode substrates on both sides of the membrane. That is, the membrane electrode assembly has an anode catalyst layer and an anode electrode substrate on one side of the membrane, and a cathode catalyst layer and a cathode electrode substrate on the other side.

[0156] The electrode substrate (which may also serve as a gas diffusion layer) is primarily intended for application of voltage and is made of a conductive material. Examples of the electrode substrate include porous substrates made of metal or carbon. Examples of metal porous substrates include nonwoven metal fabrics, sintered metal fibers, sintered metal powders, and sintered metal foams. Examples of carbon porous substrates include carbon felt, carbon paper, carbon cloth, and sintered graphite particles.

[0157] As the anode electrode substrate, a metal porous substrate is preferably used, which has excellent corrosion resistance in environments of high potential, the presence of oxygen, strong acidity, etc. From the above viewpoints, the metal constituting the metal porous substrate is preferably titanium, aluminum, nickel, stainless steel, or an alloy containing at least one of these metals as a main component, and particularly preferably titanium or an alloy containing titanium as a main component.

[0158] As the cathode electrode substrate, from the viewpoints of material cost and electrical conductivity, a carbon porous substrate is preferred, and carbon paper is particularly preferred.

[0159] In the membrane catalyst layer structure according to an embodiment of the present invention, one or both of the anode catalyst layer and the cathode catalyst layer can be laminated on an electrode substrate. During the assembly process of the membrane electrode assembly, the electrode substrate on which the catalyst layer is laminated and the diaphragm are arranged, resulting in a configuration in which the anode catalyst layer and the cathode catalyst layer are arranged opposite each other with the diaphragm sandwiched between them. In other words, the membrane catalyst layer structure is completed during the assembly process of the membrane electrode assembly, and this embodiment is included in the present invention.

[0160] In the above embodiment, the anode catalyst layer and the cathode catalyst layer may each be laminated on an electrode substrate, but since sufficient adhesion to the catalyst layer may not be obtained depending on the type of electrode substrate, it is preferable to select an appropriate electrode substrate depending on the type of electrode substrate. For example, since a carbon porous substrate has relatively good adhesion to the catalyst layer, the cathode catalyst layer may be laminated on a cathode electrode substrate, for which a carbon porous substrate is suitable, and the anode catalyst layer may be laminated on a membrane. The above-mentioned coating method or transfer method can be used as a method for laminating the catalyst layer on the electrode substrate.

[0161] [Application Examples] The membrane-catalyst layer structure and membrane-electrode assembly according to the embodiments of the present invention can be applied to fuel cells, redox flow batteries, water electrolysis devices, electrochemical hydrogen compression devices, etc. Among these, application to fuel cells and water electrolysis devices is preferred, and application to water electrolysis devices is particularly preferred. Application examples to water electrolysis devices will be described in detail below, but the present invention is not limited thereto.

[0162] [Water Electrolysis Cell and Water Electrolysis Apparatus] The water electrolysis cell of the present invention includes a membrane electrode assembly (MEA), which is internally partitioned by a diaphragm into an anode (composed of an anode catalyst layer and an anode electrode substrate) and a cathode (composed of a cathode catalyst layer and a cathode electrode substrate).

[0163] 1 is a cross-sectional schematic diagram showing an example of a water electrolysis cell of the present invention. The interior of the water electrolysis cell 1 is partitioned by a diaphragm 10 into an anode 20 and a cathode 30. The anode 20 comprises an anode catalyst layer and an anode electrode substrate (not shown), and the cathode 30 comprises a cathode catalyst layer and a cathode electrode substrate (not shown). These are sandwiched from both sides by separators 41 and 42.

[0164] The water electrolysis device has a plurality of water electrolysis cells arranged therein, and a power supply (not shown) is connected to each anode 20 and cathode 30 to apply a voltage. The water electrolysis device basically includes a water supply unit that supplies water to the water electrolysis cells, a power supply unit that supplies power to the water electrolysis cells, an oxygen discharge unit that discharges generated oxygen, a hydrogen discharge unit that discharges generated hydrogen, and a water discharge unit that discharges excess water after electrolysis.

[0165] [Water Electrolysis Method] The water electrolysis method of the present invention is performed using the water electrolysis cell of the present invention and the water electrolysis apparatus of the present invention. That is, in the water electrolysis method according to the embodiment of the present invention, water is supplied to a water electrolysis cell whose interior is partitioned into an anode and a cathode by a diaphragm containing a polymer electrolyte membrane, and electrolyzed to produce oxygen at the anode and hydrogen at the cathode. Preferably, the anode catalyst layer constituting the anode contains elemental iridium as a catalyst, the cathode catalyst layer constituting the cathode contains elemental platinum as a catalyst, and the diaphragm contains compound N having a nitrogen-containing heterocycle. Furthermore, it is preferred that the cathode catalyst layer contains elemental platinum and elemental ruthenium as catalysts. The polymer electrolyte membrane, the diaphragm containing the same, compound N, anode catalyst layer, and cathode catalyst layer in this method can be preferably those described above.

[0166] The method for supplying water to the water electrolysis cell of the present invention is not particularly limited, and any known method can be used. Preferred examples of the water supply method for the water electrolysis cell of the present invention include a method for supplying water to the anode, a method for supplying water to the cathode, and a method for supplying water to both the anode and the cathode. In the above water supply methods, it is preferable to supply water from outside the water electrolysis cell using a means such as a pump. Any of the above water supply methods can be used in the water electrolysis method of the present invention. Among these, it is preferable that water is supplied at least to the anode, since promoting the production of oxygen and protons by the oxidation reaction of water is preferable from the viewpoint of electrolysis efficiency.

[0167] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. The various measurement conditions are as follows.

[0168] (1) Molecular Weight of Polymer The number-average molecular weight and weight-average molecular weight of the polymer were measured by GPC. The gel permeation chromatograph used was an HLC-8022GPC manufactured by Tosoh Corporation. Two TSK gel Super HM-H (inner diameter 6.0 mm, length 15 cm) GPC columns manufactured by Tosoh Corporation were used. Measurements were performed at a flow rate of 0.2 mL / min in N-methyl-2-pyrrolidone solvent (N-methyl-2-pyrrolidone solvent containing 10 mmol / L of lithium bromide), and the number-average molecular weight and weight-average molecular weight were calculated in terms of standard polystyrene.

[0169] (2) Ion Exchange Capacity (IEC) was measured by the neutralization titration method described in 1) to 4) below. Measurements were performed three times, and the average value was calculated. 1) After proton exchange and thorough washing with pure water, the block copolymer was wiped dry and then vacuum-dried at 100°C for at least 12 hours to determine the dry weight. 2) 50 mL of a 5 wt% aqueous solution of sodium sulfate was added to the block copolymer, and the mixture was allowed to stand for 12 hours to perform ion exchange. 3) The resulting sulfuric acid was titrated using a 0.01 mol / L aqueous solution of sodium hydroxide. 0.1 w / v% commercially available phenolphthalein solution for titration was added as an indicator, and the point at which the solution turned a light reddish-purple color was defined as the endpoint. 4) IEC was calculated using the following formula: IEC (meq / g) = [concentration of aqueous sodium hydroxide solution (mmol / ml) x amount added (ml)] / dry weight of sample (g).

[0170] (3) Measurement of the thickness of the diaphragm and catalyst layer The cross sections of the diaphragm and each catalyst layer were observed using a scanning electron microscope (SEM) under the following conditions, and the thicknesses of the diaphragm, anode catalyst layer, and cathode catalyst layer were measured from the obtained images. Apparatus: Field Emission Scanning Electron Microscope (FE-SEM) S-4800 (Hitachi High-Technologies Corporation) Acceleration voltage: 2.0 kV Pretreatment: A cross-sectional sample prepared using the BIB method was coated with Pt and measured. BIB method: Cross-sectional sample preparation device using an argon ion beam. A shielding plate was placed directly above the sample, and a broad argon ion beam was irradiated from above to perform etching, creating an observation and analysis surface (cross section).

[0171] (4) Measurement of BET specific surface area of ​​platinum or other catalyst-supported carbon particles Platinum or other catalyst-supported carbon particles were placed in a glass container and then vacuum dried at 23°C for 16 hours. Next, the vacuum-dried platinum or other catalyst-supported carbon particles were placed in a dedicated container that had been dried and its mass measured in advance, and pretreatment was carried out according to the following conditions. After pretreatment was completed, the mass of the dedicated container + platinum or other catalyst-supported carbon particles was measured, and the mass of the platinum or other catalyst-supported carbon particles was calculated from the difference with the mass of the dedicated container. Next, the pretreated platinum or other catalyst-supported carbon particles were attached to a measuring device together with the dedicated container, and gas adsorption measurement was carried out according to the following conditions, with the vertical axis p / V (p ０ -p), horizontal axis p / p ０ The adsorption isotherm was created. From the adsorption isotherm, the horizontal axis p / p０ Data with a value of 0.05 to 0.3 was extracted, and the BET specific surface area was calculated from the slope and vertical intercept of an approximation curve created by the least squares method. <Pretreatment conditions> Apparatus: BELPREP VAC II (manufactured by Microtrac BEL Co., Ltd.) Temperature: 100°C Time: 5 hours Treatment atmosphere: degassing under reduced pressure of 10 Pa or less <BET specific surface area measurement> Apparatus: BELSORP-18 PLUS HT (manufactured by Microtrac BEL Co., Ltd.) Temperature: 77 K (liquid nitrogen temperature) Dead volume measurement gas: He Adsorbate: N ２ Equilibrium setting time: 180 seconds (stabilization waiting time at each pressure) Specific surface area analysis method: BET method <Meaning of symbols> V: N on the catalyst surface at each pressure ２ Adsorption amount p: Measured pressure p ０ : Atmospheric pressure ・p / p ０ : Relative pressure (5) Evaluation of electrolytic performance To evaluate the electrolytic performance of the membrane-catalyst layer laminate, a membrane-electrode assembly was produced in the following manner.

[0172] [Membrane-electrode assembly] A commercially available gas diffusion electrode 24BCH manufactured by SGL was laminated as a cathode electrode substrate on the cathode catalyst layer side of the membrane-catalyst layer laminate produced in the Examples and Comparative Examples, and a commercially available porous titanium sintered body plate was laminated as an anode electrode substrate on the anode catalyst layer side, to produce a membrane-electrode assembly.

[0173] [Water Electrolysis Method] The membrane-electrode assembly prepared above was placed in a JARI standard cell "Ex-1" (electrode area 25 cm) manufactured by Eiwa Corporation. ２ ) and the cell temperature was set to 60°C. Deionized water with an electrical conductivity of 1 μS / cm or less was supplied to both the anode and cathode at a flow rate of 0.2 L / min at atmospheric pressure, and the current density was set to 1.5 A / cm ２ A voltage was applied so that water electrolysis was carried out for 2,000 hours.

[0174] The applied voltage was measured at 0 and 2,000 hours after electrolysis, and the voltage increase rate after 2,000 hours was calculated using the following formula 1: Voltage increase rate (%) = (V １ -V ０ ) / V ０ ×100 ...Formula 1 In the formula, V １is the applied voltage after 2,000 hours, V ０ represents the initial (0 hour) applied voltage.

[0175] The lower the voltage at time 0 (initial voltage), the higher the electrolysis performance, and the lower the voltage rise rate, the less the electrolysis performance has deteriorated.

[0176] Synthesis of Polyetherketone-Based Block Copolymer (PEK Block) Synthesis Example 1 Synthesis of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane (K-DHBP) Represented by the Following Chemical Formula (G1) In a 500 mL flask equipped with a stirrer, thermometer, and distillation tube, 49.5 g of 4,4'-dihydroxybenzophenone, 134 g of ethylene glycol, 96.9 g of trimethyl orthoformate, and 0.50 g of p-toluenesulfonic acid monohydrate were charged and dissolved. The mixture was then stirred and kept at 78 to 82°C for 2 hours. The internal temperature was then gradually raised to 120°C, and the mixture was heated until the distillation of methyl formate, methanol, and trimethyl orthoformate completely stopped. After cooling to room temperature, the reaction solution was diluted with ethyl acetate, and the organic layer was washed with 100 mL of a 5% aqueous potassium carbonate solution and separated, followed by distilling off the solvent. 80 mL of dichloromethane was added to the residue to precipitate crystals, which were filtered and dried to obtain 52.0 g of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane represented by the following chemical formula (G1). GC analysis of the crystals revealed that they were 99.9% 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane and 0.1% 4,4'-dihydroxybenzophenone. The purity was 99.9%.

[0177]

[0178] Synthesis Example 2 (Synthesis of disodium-3,3'-disulfonate-4,4'-difluorobenzophenone represented by the following chemical formula (G2)) 109.1 g of 4,4'-difluorobenzophenone (Sigma-Aldrich Japan (same) reagent) was reacted in 150 mL of fuming sulfuric acid (50% SO3) (Fujifilm Wako Pure Chemical Industries, Ltd. reagent) at 100°C for 10 hours. Thereafter, the mixture was poured little by little into a large amount of water, neutralized with sodium hydroxide, and then 200 g of table salt (NaCl) was added to precipitate the synthesized product. The obtained precipitate was filtered and recrystallized from an aqueous ethanol solution to obtain disodium-3,3'-disulfonate-4,4'-difluorobenzophenone represented by the following chemical formula (G2). The purity was 99.3%.

[0179]

[0180] Synthesis Example 3 (Synthesis of nonionic oligomer a1 represented by the following general formula (G3)) 16.59 g of potassium carbonate (Aldrich reagent, 120 mmol), 25.83 g (100 mmol) of K-DHBP obtained in Synthesis Example 1, and 20.3 g of 4,4'-difluorobenzophenone (Aldrich reagent, 93 mmol) were placed in a 2,000 mL SUS polymerization reactor equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap. After nitrogen substitution, 300 mL of N-methylpyrrolidone (NMP) and 100 mL of toluene were added, and the mixture was dehydrated at 150°C. The temperature was then raised to remove the toluene, and polymerization was carried out at 170°C for 3 hours. Purification by reprecipitation with a large amount of methanol yielded a terminal hydroxyl form of nonionic oligomer a1. The number average molecular weight of the terminal hydroxyl form of this nonionic oligomer a1 was 10,000.

[0181] A 500 mL three-neck flask equipped with a stirrer, nitrogen inlet tube, and Dean-Stark trap was charged with 1.1 g of potassium carbonate (Sigma-Aldrich Japan (same) reagent, 8 mmol) and 20.0 g (2 mmol) of the terminal hydroxy compound of the above nonionic oligomer a1. After replacing the atmosphere inside the flask with nitrogen, 100 mL of NMP and 30 mL of toluene were added, and the mixture was dehydrated at 100°C and then heated to remove the toluene. Furthermore, 2.2 g of hexafluorobenzene (Sigma-Aldrich Japan (same) reagent, 12 mmol) was added, and the reaction was carried out at 105°C for 12 hours. Purification was carried out by reprecipitation with a large amount of isopropyl alcohol, yielding nonionic oligomer a1 (terminal: fluoro group) represented by the following general formula (G3). The number average molecular weight was 11,000.

[0182]

[0183] Synthesis Example 4 (Synthesis of ionic oligomer a2 represented by the following general formula (G4)) 27.6 g of potassium carbonate (Sigma-Aldrich Japan (same manufacturer), reagent, 200 mmol), 12.9 g (50 mmol) of K-DHBP obtained in Synthesis Example 1, 9.3 g of 4,4'-biphenol (Sigma-Aldrich Japan (same manufacturer), reagent, 50 mmol), 39.3 g (93 mmol) of disodium-3,3'-disulfonate-4,4'-difluorobenzophenone obtained in Synthesis Example 2, and 17.9 g of 18-crown-6 (Fujifilm Wako Pure Chemical Industries, Ltd., 82 mmol) were placed in a 2,000 mL SUS polymerization reactor equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap. After nitrogen substitution, 300 mL of NMP and 100 mL of toluene were added, and the mixture was dehydrated at 150°C, heated to remove toluene, and then polymerized at 170°C for 6 hours. The resulting product was purified by reprecipitation with a large amount of isopropyl alcohol to obtain an ionic oligomer a2 (terminal: hydroxy group) represented by the following general formula (G4). The number average molecular weight was 16,000. In general formula (G4), M represents a hydrogen atom, Na, or K.

[0184]

[0185] (Synthesis of Polyetherketone Block Copolymer) 16 g of ionic oligomer a2 and 11 g of nonionic oligomer a1 were placed in a 2,000 mL SUS polymerization reactor equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap, and NMP was added so that the total amount of the oligomers charged was 7 wt %, followed by reaction at 105° C. for 24 hours.

[0186] The resulting precipitate was recovered by filtration and washed with a large amount of isopropyl alcohol to obtain a block copolymer b1. The polyetherketone-based block copolymer had a weight-average molecular weight of 340,000 and an ion-exchange capacity (IEC) of 2.1 meq / g.

[0187] [Synthesis of Compound N] Compounds (E1), (E4), (E8), (E10), (E23), (E34), (E36), (F23), (P3), and (H3) were synthesized. These compounds can be synthesized with reference to International Publication Nos. WO 2014 / 08413, WO 2015 / 152058, and WO 2015 / 156228. Commercially available products were used for (F17), (F19), (P1), (H1), (H2), and porphyrin.

[0188]

[0189]

[0190]

[0191] (H1) 1,10-phenanthroline (H2) 5-amino-1,10-phenanthroline.

[0192] [Example 1] [Preparation of Polymer Electrolyte Membrane] A PET film "Lumirror" (registered trademark) 125T60 manufactured by Toray Industries, Inc. was laminated and fixed to a SUS plate using "Kapton" (registered trademark) tape. 20 g of the polyetherketone-based block copolymer synthesized above was dissolved in NMP. 100 mg of E1 as compound N was added to this solution, and the mixture was stirred with a stirrer for 3 minutes to obtain a transparent solution with a polymer concentration of 13% by mass. The resulting solution was pressure-filtered using a 1 μm polypropylene filter, then cast onto the PET film and dried to obtain a film-like membrane. This membrane was then immersed in a 10% by mass aqueous sulfuric acid solution at 80°C for 24 hours to undergo proton substitution and deprotection reactions, and then thoroughly washed by immersion in a large excess of pure water for 24 hours to obtain a polymer electrolyte membrane (thickness 90 μm). This polymer electrolyte membrane was used as a diaphragm. The content of compound N in the diaphragm was 0.5 parts by mass per 100 parts by mass of polymer electrolyte.

[0193] [Preparation of membrane / catalyst layer assembly] A membrane / catalyst layer assembly was prepared by laminating the following anode catalyst layer on one side of the polymer electrolyte membrane (diaphragm) prepared above, and the following cathode catalyst layer on the other side. The mass of iridium element in the anode catalyst layer was 0.8 mg / cm ２ , the mass of platinum element in the cathode catalyst layer is 0.25 mg / cm ２ The thickness of each was adjusted so that

[0194] <Anode catalyst layer> The total solid content was catalyst particles (IrO ２ The anode catalyst layer contained 10 parts by mass of Elyst Ir75 0480 catalyst (Ir content 75%) and 1.3 parts by mass of a fluorine-based polymer electrolyte (Nafion®, product number D2020, manufactured by Chemours Corporation, IEC=0.91 meq / g). The ratio (Ya) of the mass of the polymer electrolyte to the mass of elemental iridium was 0.17. The thickness of this anode catalyst layer was 8 μm.

[0195] <Cathode catalyst layer> The total solid content was catalyst particles (Tanaka Kikinzoku Kogyo K.K., platinum-ruthenium alloy-supported carbon particles TEC61E54 (catalyst loading rate 54 mass%, Pt / Ru mass ratio = 1 / 0.78, BET specific surface area 303 m)２ A catalyst layer comprising 10 parts by mass of platinum (Pt) and 4 parts by mass of a fluorine-based polymer electrolyte (Nafion®, product number D2020, IEC = 0.91 meq / g, manufactured by Chemours Corporation). The ratio (Yc) of the mass of the polymer electrolyte to the total mass of platinum and ruthenium was 0.74. The thickness of this cathode catalyst layer was 12 μm.

[0196] Comparative Example 1 A membrane / catalyst layer assembly was prepared in the same manner as in Example 1, except that Compound N was not contained in the polymer electrolyte membrane.

[0197] Examples 2 to 18 Membrane catalyst layer assemblies were prepared in the same manner as in Example 1, except that the type and amount of compound N added were changed as shown in Table 1.

[0198] Example 19 A membrane / catalyst layer assembly was prepared in the same manner as in Example 1, except that the polyether ketone block copolymer was changed to the following fluorine-based polymer electrolyte.

[0199] <Fluorine-Based Polymer Electrolyte> A solution of "Nafion" (registered trademark) product number D2020 (IEC=0.91 meq / g) manufactured by Chemours Inc., in which the solvent (water and 1-propanol) was replaced with NMP, was used.

[0200] Example 20 A membrane catalyst layer assembly was produced in the same manner as in Example 1, except that the cathode catalyst layer in Example 1 was changed to the following.

[0201] <Cathode catalyst layer> The total solid content was catalyst particles (platinum-ruthenium alloy-supported carbon particles TEC66E50 manufactured by Tanaka Kikinzoku Kogyo K.K. (catalyst loading rate: 50 mass%, Pt / Ru mass ratio = 1 / 0.52, BET specific surface area: 312 m) ２ A catalyst layer containing 10 parts by mass of platinum (Pt / g) and 4 parts by mass of a fluorine-based polymer electrolyte (Nafion (registered trademark), product number D2020, manufactured by Chemours Corporation). The ratio (Yc) of the mass of the polymer electrolyte to the total mass of platinum and ruthenium was 0.8. The thickness of this cathode catalyst layer was 11 μm.

[0202] Example 21 A membrane catalyst layer assembly was produced in the same manner as in Example 1, except that the cathode catalyst layer in Example 1 was changed to the following.

[0203] <Cathode catalyst layer> The total solid content was catalyst particles (Tanaka Kikinzoku Kogyo K.K., platinum-ruthenium alloy-supported carbon particles TEC62E58-HT (catalyst loading rate 58 mass%, Pt / Ru mass ratio = 1 / 1.04, BET specific surface area 285 m) ２ A catalyst layer comprising 10 parts by mass of platinum (Pt / g) and 4 parts by mass of a fluorine-based polymer electrolyte (Nafion (registered trademark), product number D2020, manufactured by Chemours Corporation). The ratio (Yc) of the mass of the polymer electrolyte to the total mass of platinum and ruthenium was 0.69. The thickness of this cathode catalyst layer was 13 μm.

[0204] Example 22 A membrane catalyst layer assembly was produced in the same manner as in Example 1, except that the cathode catalyst layer in Example 1 was changed to the following.

[0205] <Cathode catalyst layer> The total solid content was catalyst particles (Tanaka Kikinzoku Kogyo K.K., platinum-ruthenium alloy-supported carbon particles TEC61E54-HT2 (catalyst loading rate 54 mass%, Pt / Ru mass ratio = 1 / 0.78, BET specific surface area 295 m) ２ A catalyst layer comprising 10 parts by mass of platinum (Pt) and 4 parts by mass of a fluorine-based polymer electrolyte (Nafion®, product number D2020, IEC = 0.91 meq / g, manufactured by Chemours Corporation). The ratio (Yc) of the mass of the polymer electrolyte to the total mass of platinum and ruthenium was 0.74. The thickness of this cathode catalyst layer was 12 μm.

[0206] Example 23 A membrane catalyst layer assembly was produced in the same manner as in Example 1, except that the cathode catalyst layer in Example 1 was changed to the following.

[0207] <Cathode catalyst layer> The total solid content was catalyst particles (platinum-ruthenium alloy-supported carbon particles TEC61V54-HT2 manufactured by Tanaka Kikinzoku Kogyo K.K. (catalyst loading rate: 54 mass%, Pt / Ru mass ratio = 1 / 0.78, BET specific surface area: 90 m) ２A catalyst layer comprising 10 parts by mass of platinum (Pt) and 4 parts by mass of a fluorine-based polymer electrolyte (Nafion®, product number D2020, IEC = 0.91 meq / g, manufactured by Chemours Corporation). The ratio (Yc) of the mass of the polymer electrolyte to the total mass of platinum and ruthenium was 0.74. The thickness of this cathode catalyst layer was 10 μm.

[0208] Example 24 A membrane catalyst layer assembly was produced in the same manner as in Example 1, except that the cathode catalyst layer in Example 1 was changed to the following.

[0209] <Cathode catalyst layer> The total solid content was catalyst particles (Tanaka Kikinzoku Kogyo K.K., platinum-ruthenium alloy-supported carbon particles TEC66V50-HT2 (catalyst loading rate 50 mass%, Pt / Ru mass ratio = 1 / 0.52, BET specific surface area 94 m) ２ A catalyst layer including 10 parts by mass of platinum (Pt / g) and 4 parts by mass of a fluorine-based polymer electrolyte (Nafion (registered trademark), product number D2020, manufactured by Chemours Corporation). The ratio (Yc) of the mass of the polymer electrolyte to the total mass of platinum and ruthenium was 0.8. The thickness of this cathode catalyst layer was 9 μm.

[0210] Comparative Example 2 A membrane catalyst layer assembly was produced in the same manner as in Example 1, except that the cathode catalyst layer in Example 1 was changed to the following.

[0211] <Cathode catalyst layer> The total solid content was catalyst particles (platinum-supported carbon particles TEC10E50E (platinum support rate 50 mass %, BET specific surface area 375 m) manufactured by Tanaka Kikinzoku Kogyo K.K.) ２ A catalyst layer containing 10 parts by mass of platinum (Pt / g) and 4 parts by mass of a fluorine-based polymer electrolyte (Nafion (registered trademark), product number D2020, manufactured by Chemours Corporation). The ratio (Yc) of the mass of the polymer electrolyte to the mass of platinum element was 0.8. The thickness of this cathode catalyst layer was 6 μm.

[0212] Comparative Example 3 A membrane-catalyst layer assembly was produced in the same manner as in Comparative Example 2, except that the anode catalyst layer was changed to the following: The mass of platinum element in this anode catalyst layer was 0.3 mg / cm ２ The thickness was adjusted so that

[0213] <Anode catalyst layer> A catalyst layer containing, as total solid content, 10 parts by mass of catalyst particles (platinum-supported carbon particles TEC10E50E (platinum support rate 50 mass%) manufactured by Tanaka Kikinzoku Kogyo K.K.) and 4 parts by mass of a fluorine-based polymer electrolyte (Nafion (registered trademark) product number D2020 manufactured by Chemours Corporation). The ratio of the mass of the polymer electrolyte to the total mass of platinum and ruthenium was 0.8. The thickness of this anode catalyst layer was 7 μm.

[0214] Example 25 A membrane catalyst layer assembly was produced in the same manner as in Example 1, except that the anode catalyst layer in Example 1 was changed to the following.

[0215] <Anode catalyst layer> Iridium oxide (IrO manufactured by Umicore) was used as the total solid content. ２ The anode catalyst layer contained 10 parts by mass of Elyst Ir75 0480 catalyst (Ir content 75%), 1.5 parts by mass of commercially available platinum particles in terms of elemental platinum, and 1.3 parts by mass of a fluorine-based polymer electrolyte (Nafion®, product number D2020, manufactured by Chemours Corporation). The ratio (Ya) of the mass of the polymer electrolyte to the mass of elemental iridium was 0.17. The thickness of this anode catalyst layer was 9 μm.

[0216] Example 26 A membrane catalyst layer assembly was produced in the same manner as in Example 14, except that the anode catalyst layer in Example 14 was changed to the following.

[0217] <Anode catalyst layer> The total solid content was catalyst particles (IrO ２ The anode catalyst layer contained 10 parts by mass of Elyst Ir75 0480 catalyst (Ir content 75%) and 4.5 parts by mass of a fluorine-based polymer electrolyte (Nafion®, product number D2020, manufactured by Chemours Corporation). The ratio (Ya) of the mass of the polymer electrolyte to the mass of elemental iridium was 0.60. The thickness of this anode catalyst layer was 11 μm.

[0218] [Example 27] In Example 1, the mass of platinum element in the cathode catalyst layer was 0.15 mg / cm ２A membrane catalyst layer assembly was produced in the same manner as in Example 1, except for the above change. The thickness of this cathode catalyst layer was 7 μm.

[0219] [Example 28] In Example 14, the mass of platinum element in the cathode catalyst layer was 0.55 mg / cm ２ A membrane catalyst layer assembly was produced in the same manner as in Example 14, except for changing the cathode catalyst layer to the following: The thickness of this cathode catalyst layer was 26 μm.

[0220] [Evaluation] The electrolytic performance of the membrane catalyst layer assemblies prepared in the above Examples and Comparative Examples was evaluated by the method described in (4) above. The results are shown in Table 1.

[0221]

[0222] Example 29 A diaphragm was prepared by laminating the following protective layer (thickness: 10 μm) on one side of the polymer electrolyte membrane of Example 1. A membrane-catalyst layer assembly was prepared in the same manner as in Example 1, except that a cathode catalyst layer was laminated on the protective layer side of this diaphragm, and an anode catalyst layer was laminated on the polymer electrolyte membrane side. The content of compound N was 0.46 parts by mass per 100 parts by mass of the polymer electrolyte contained in the diaphragm (the total amount of the PEK block of the polymer electrolyte membrane and the fluoropolymer electrolyte of the protective layer).

[0223] <Protective Layer> The protective layer contains, as a total solid content, 10 parts by mass of carbon black ("VULCAN" (registered trademark) XC72 manufactured by Cabot Corporation) and 8 parts by mass of a fluorine-based polymer electrolyte ("Nafion" (registered trademark) product number D2020 manufactured by Chemours Inc.).

[0224] Example 30 A membrane-catalyst layer structure was produced in the same manner as in Example 26, except that in Example 29, compound N (E1) was added to the protective layer rather than to the polymer electrolyte membrane. To add compound N (E1) to the protective layer, a solution of fluoropolymer electrolyte (Nafion (registered trademark) product number D2020 manufactured by Chemours Inc.) in which the solvent (water and 1-propanol) had been replaced with NMP was used. The amount of compound N added was adjusted to 0.1 parts by mass per 100 parts by mass of the polymer electrolyte contained in the membrane (the total amount of the PEK block of the polymer electrolyte membrane and the fluoropolymer electrolyte of the protective layer).

[0225] [Example 31] <Preparation of Polymer Electrolyte Membrane> A PET film "Lumirror" (registered trademark) 125T60 manufactured by Toray Industries, Inc. was bonded to a SUS plate using "Kapton" (registered trademark) tape. A solution (polymer concentration 13% by mass) obtained by dissolving the polyetherketone-based block copolymer synthesized above in NMP was cast onto the PET film, and the following porous substrate (mesh fabric) was bonded thereon and impregnated. Furthermore, a solution obtained by dissolving 20 g of the polyetherketone-based block copolymer synthesized above and 300 mg of compound N (E4) in NMP was applied to the porous substrate and dried to obtain a film-like membrane. Furthermore, this membrane was immersed in a 10% by mass aqueous sulfuric acid solution at 80 ° C. for 24 hours to undergo proton substitution and deprotection reactions, and then immersed in a large excess of pure water for 24 hours and thoroughly washed to obtain a polymer electrolyte membrane (thickness 70 μm).

[0226] This polymer electrolyte membrane has a three-layer structure, with a non-composite layer containing a polymer electrolyte but not a porous substrate on each side of a composite layer containing a porous substrate and a polymer electrolyte. The thickness of each layer, from the PET film side, was "non-composite layer 1 (thickness 15 μm) / composite layer (thickness 35 μm) / non-composite layer 2 (thickness 20 μm)." In this polymer electrolyte membrane, compound N is contained only in non-composite layer 2. The content of compound N in this polymer electrolyte membrane is 0.1 parts by mass per 100 parts by mass of polymer electrolyte.

[0227] [Porous substrate] A mesh fabric made of liquid crystal polyester fiber produced in Production Example 1 of WO 2019 / 188960 was used.

[0228] [Preparation of membrane-catalyst layer structure] A membrane-catalyst layer laminate was prepared by laminating the anode catalyst layer of Example 1 on the non-composite layer 1 side of the polymer electrolyte membrane (diaphragm) prepared above, and the cathode catalyst layer of Example 1 on the non-composite layer 2 side.

[0229] [Evaluation] The electrolytic performance of the membrane catalyst layer assemblies prepared in the above Examples and Comparative Examples was evaluated. The results are shown in Table 2.

[0230]

[0231] REFERENCE SIGNS LIST 1 water electrolysis cell 10 diaphragm 20 first catalyst layer 30 second catalyst layer 41, 42 separator

Claims

1. A membrane / catalyst layer construct comprising a first catalyst layer and a second catalyst layer disposed opposite each other with a membrane including at least a polymer electrolyte membrane therebetween, the first catalyst layer and the second catalyst layer containing platinum element and / or iridium element as a first metal, the first catalyst layer and / or the second catalyst layer further containing at least one element selected from the group consisting of gold, silver, copper, nickel, palladium, cobalt, rhodium, iron, ruthenium and osmium as a second metal, and the membrane containing a compound N having a nitrogen-containing heterocycle.

2. The membrane / catalyst layer construct according to claim 1, wherein the compound N having a nitrogen-containing heterocycle contains a nitrogen-containing five-membered aromatic ring or a nitrogen-containing six-membered aromatic ring.

3. The membrane / catalyst layer construct according to claim 1 or 2, wherein the compound N having a nitrogen-containing heterocycle contains a nitrogen-containing six-membered aromatic ring.

4. The membrane / catalyst layer construct according to any one of claims 1 to 3, wherein the compound N having a nitrogen-containing heterocycle contains a plurality of nitrogen-containing aromatic six-membered rings.

5. The membrane / catalyst layer construct according to any one of claims 1 to 4, wherein the compound N having a nitrogen-containing heterocycle is a compound selected from the group consisting of general formulas (D1), (D2) and (D3). In the formula, R １ represents at least one group selected from the group consisting of divalent or higher hydrocarbon groups, amino groups, sulfide groups, ketone groups, sulfonyl groups, sulfone groups, and ether groups; n １ Q １ each independently represents a 5- or 6-membered nitrogen-containing aromatic heterocycle, a condensed ring between these nitrogen-containing aromatic heterocycles, or a condensed ring between these nitrogen-containing aromatic heterocycles and a hydrocarbon aromatic ring, and these nitrogen-containing aromatic heterocycles and hydrocarbon aromatic rings may each be substituted with any substituent. １ represents an integer from 2 to 10. In the formula, R ２ represents at least one group selected from the group consisting of a hydrocarbon group, an amino group, a sulfide group, a ketone group, a sulfonyl group, a sulfone group, and an ether group, or a direct bond; Q ２ represents a group in which 1 to 5 five- or six-membered nitrogen-containing aromatic heterocycles, condensed rings between these nitrogen-containing aromatic heterocycles, or condensed rings between these nitrogen-containing aromatic heterocycles and hydrocarbon aromatic rings are linked together, and these nitrogen-containing aromatic heterocycles and hydrocarbon aromatic rings may each be substituted with any substituent. ２ represents an integer from 1 to 20. １ and X ２ each independently represents at least one group selected from the group consisting of a hydrogen atom, a halogen, a hydrocarbon group, an alkoxy group, an aryloxy group, a carboxyl group, a carboxylate group, a phosphino group, a phosphine oxide group, a phosphonic acid group, a phosphate group, a sulfonic acid group, a sulfate ester group, a hydroxyl group, an amino group, a cyano group, and a nitro group. In the formula, R ３ represents C(R) or a nitrogen atom, R represents a hydrogen atom or an alkyl group, and Q ３ represents a 5- or 6-membered nitrogen-containing aromatic heterocycle, a condensed ring between these nitrogen-containing aromatic heterocycles, or a condensed ring between these nitrogen-containing aromatic heterocycles and a hydrocarbon aromatic ring, and these nitrogen-containing aromatic heterocycles and hydrocarbon aromatic rings may each be substituted with any substituent. g represents an integer of 5 to 500.

6. A membrane / catalyst layer structure according to any one of claims 1 to 5, wherein the first catalyst layer is an oxygen generating catalyst layer and contains an iridium element as a first metal, and the second catalyst layer is a proton reducing catalyst layer and contains a platinum element as a first metal.

7. A membrane / catalyst layer structure according to any one of claims 1 to 5, wherein the first catalyst layer is an oxygen reduction catalyst layer and contains platinum element as a first metal, and the second catalyst layer is a hydrogen oxidation catalyst layer and contains platinum element as a first metal.

8. The membrane-catalyst layer structure according to claim 6, wherein the second catalyst layer contains ruthenium element as the second metal.

9. The membrane-catalyst layer structure according to claim 6 or 8, wherein the second catalyst layer comprises carbon particles carrying platinum or carbon particles carrying platinum and ruthenium.

10. The membrane-catalyst layer structure according to claim 8 or 9, wherein the second catalyst layer comprises carbon particles carrying a platinum-ruthenium alloy.

11. The membrane-catalyst layer structure according to any one of claims 1, 6, and 8 to 10, wherein the first catalyst layer contains iridium element as a first metal, and contains iridium oxide as the iridium element.

12. The membrane-catalyst layer structure according to any one of claims 1 to 11, wherein the first catalyst layer and the second catalyst layer further contain a polymer electrolyte.

13. A membrane / catalyst layer structure according to any one of claims 1, 6, and 8 to 12, wherein the first catalyst layer comprises iridium element as a first metal and a polymer electrolyte, and the ratio (Ya) of the mass of the polymer electrolyte to the mass of the iridium element is 0.05 or more and less than 0.5, and the second catalyst layer comprises platinum element as a first metal, ruthenium element as a second metal, and a polymer electrolyte, and the ratio (Yc) of the mass of the polymer electrolyte to the total mass of the platinum element and the ruthenium element is 0.25 or more and 1.1 or less.

14. The membrane / catalyst layer structure according to claim 13, wherein the proportion (Ya) is smaller than the proportion (Yc).

15. A membrane / catalyst layer structure according to any one of claims 1 to 14, wherein the thickness of the first catalyst layer and / or the second catalyst layer is 25% or less relative to 100% of the thickness of the membrane.

16. The membrane-catalyst layer structure according to any one of claims 1 to 15, wherein the polymer electrolyte membrane contains a hydrocarbon-based polymer electrolyte.

17. The membrane-catalyst layer structure according to claim 1 or 7, wherein the first catalyst layer is an anode catalyst layer and the second catalyst layer is a cathode catalyst layer.

18. A fuel cell comprising the membrane / catalyst layer assembly according to any one of claims 1 to 17.

19. A water electrolysis device comprising the membrane / catalyst layer assembly according to any one of claims 1 to 17.

20. A membrane-electrode assembly comprising an electrode substrate disposed on each side of the membrane-catalyst layer structure according to any one of claims 1 to 17.

21. A fuel cell comprising the membrane-electrode assembly according to claim 20.

22. A water electrolysis cell comprising the membrane-electrode assembly according to claim 20.

23. A water electrolysis device comprising the water electrolysis cell according to claim 22.

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