Solid polymer electrolyte membrane, membrane-electrode assembly, water electrolysis device, hydrogen production method, and method for manufacturing membrane-electrode assembly

Abstract

The present disclosure provides a solid polymer electrolyte membrane capable of suppressing the generation of curling and the permeation of hydrogen, a membrane electrode assembly, a water electrolysis device, and a method for manufacturing a membrane electrode assembly. The solid polymer electrolyte membrane of the present disclosure is provided with a first layer containing a first fluorine-containing polymer having an ion exchange group and a platinum-containing substance, and a second layer containing a second fluorine-containing polymer having an ion exchange group, the concentration of the platinum-containing substance in the second layer being lower than the concentration of the platinum-containing substance in the first layer, the ion exchange capacity of the first fluorine-containing polymer being greater than the ion exchange capacity of the second fluorine-containing polymer, and the solid polymer electrolyte membrane further having a reinforcement disposed closer to the surface side of the first layer side of the solid polymer electrolyte membrane than the central position in the thickness direction of the solid polymer electrolyte membrane.

Description

Technical Field

[0001] This disclosure relates to solid polymer electrolyte membranes, membrane electrode assemblies, water electrolysis devices, methods for manufacturing hydrogen, and methods for manufacturing membrane electrode assemblies. Background Technology

[0002] Based on the concept of converting electricity into gas, that is, converting surplus electricity into gas for storage and utilization, the use of solid polymer water electrolysis devices (PEM type water electrolysis devices) is being studied.

[0003] In recent years, there has been a demand for further improvements in the performance of water electrolysis devices, specifically a need to reduce hydrogen crossover. Here, hydrogen crossover refers to the movement of hydrogen gas generated at the cathode towards the anode side through the solid polymer electrolyte membrane in a water electrolysis device. If hydrogen crossover occurs, the efficiency of hydrogen recovery decreases.

[0004] Patent Document 1 discloses a water electrolysis device comprising a membrane, a cathode, and an anode. The membrane has first, second, and third regions arranged at equal intervals in the thickness direction. The first region is the region closest to the first main surface, the second region is the region closest to the second main surface, and the third region is located between the first and second regions. The first and third regions are substantially free of metal Pt and Pt oxide, respectively. At least one of metal Pt or Pt oxide is embedded in the second region. The cathode contains a first catalyst on the first main surface of the membrane, and the anode contains a second catalyst on the second main surface of the membrane.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: U.S. Patent No. 11,414,770 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Referring to Patent Document 1, the inventors further studied a water electrolysis device having a solid polymer electrolyte membrane containing platinum. The results showed that although hydrogen permeation could be suppressed, there was room for improvement in the phenomenon of solid polymer electrolyte membrane curling.

[0010] This disclosure was made in view of the above-mentioned problems. One embodiment of the present invention aims to provide a solid polymer electrolyte membrane capable of suppressing curling and hydrogen permeation. Another embodiment of the present invention aims to provide a membrane electrode assembly, a water electrolysis apparatus, a method for producing hydrogen, and a method for manufacturing the membrane electrode assembly.

[0011] Solution for solving the problem

[0012] This disclosure takes the following forms. [1]

[0014] A solid polymer electrolyte membrane, comprising:

[0015] The first layer comprises a first fluoropolymer having ion-exchange groups and a platinum-containing compound; and

[0016] The second layer comprises a second fluoropolymer having ion-exchange groups.

[0017] The concentration of the platinum-containing compound in the second layer is lower than the concentration of the platinum-containing compound in the first layer.

[0018] The ion exchange capacity of the first fluorinated polymer is greater than that of the second fluorinated polymer, and

[0019] The solid polymer electrolyte membrane also has a reinforcement that is arranged closer to the surface side of the first layer of the solid polymer electrolyte membrane than to the central position of the solid polymer electrolyte membrane in the thickness direction. [2]

[0021] According to the solid polymer electrolyte membrane described in [1], the solid polymer electrolyte membrane further comprises cerium oxide. [3]

[0023] According to the solid polymer electrolyte membrane described in [1] or [2], wherein the second layer does not contain the platinum-containing material described above. [4]

[0025] The solid polymer electrolyte membrane according to any one of [1] to [3], wherein the reinforcement is a woven fabric. [5]

[0027] According to the solid polymer electrolyte membrane described in [4], the fabric is composed of a material selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyether ether ketone and polyphenylene sulfide. [6]

[0029] The solid polymer electrolyte membrane according to any one of [1] to [5], wherein the thickness of the first layer is thinner than the thickness of the second layer. [7]

[0031] The solid polymer electrolyte membrane according to any one of [1] to [6], wherein the ratio of the thickness of the first layer to the total thickness of the first layer and the second layer is 0.50 or less. [8]

[0033] The solid polymer electrolyte membrane according to any one of [1] to [7], wherein the total thickness of the first layer and the second layer is 30 to 400 μm. [9]

[0035] The solid polymer electrolyte membrane according to any one of [1] to [8], wherein the absolute value of the difference between the ion exchange capacity of the first fluorinated polymer and the ion exchange capacity of the second fluorinated polymer is 0.10 to 1.40 milliequivalents / gram of dry resin.

[10]

[0037] The solid polymer electrolyte membrane according to any one of [1] to [9], wherein the ion exchange group of the first fluorinated polymer is a sulfonic acid type functional group.

[0038] The ion exchange groups of the second fluorinated polymer are sulfonic acid functional groups.

[11]

[0040] A membrane electrode assembly, characterized in that it comprises:

[0041] The solid polymer electrolyte membrane described in any one of [1] to

[10] ,

[0042] The cathode catalyst layer disposed on the surface side of the second layer of the above-mentioned solid polymer electrolyte membrane, and

[0043] An anode catalyst layer disposed on the surface side of the first layer of the aforementioned solid polymer electrolyte membrane.

[12]

[0045] A water electrolysis device, comprising:

[0046]

[11] The membrane electrode assembly described above;

[0047] The power supply unit is connected to the cathode catalyst layer side and the anode catalyst layer side of the aforementioned membrane electrode assembly; and

[0048] The water supply unit supplies water to the anode catalyst layer.

[13]

[0050] A method for producing hydrogen, wherein hydrogen is produced by electrolyzing water using the water electrolysis device described in

[12] .

[0051]

[14]

[0052] A method for manufacturing a membrane electrode assembly, the membrane electrode assembly comprising: a solid polymer electrolyte membrane, a cathode catalyst layer, and an anode catalyst layer as described in any one of [1] to

[10] ,

[0053] In the manufacturing method, the cathode catalyst layer is formed on the surface side of the second layer of the solid polymer electrolyte membrane, and the anode catalyst layer is formed on the surface side of the first layer of the solid polymer electrolyte membrane.

[0054] The effects of the invention

[0055] According to one embodiment of the present invention, a solid polymer electrolyte membrane capable of suppressing curling and hydrogen permeation can be provided. Furthermore, according to one embodiment of the present invention, a membrane electrode assembly, a method for manufacturing the membrane electrode assembly, a method for producing hydrogen, and a water electrolysis apparatus can be provided. Attached Figure Description

[0056] Figure 1 This is a cross-sectional view schematically illustrating an example of the solid polymer electrolyte membrane of this disclosure.

[0057] Figure 2 This is a cross-sectional view schematically illustrating another example of the solid polymer electrolyte membrane of this disclosure.

[0058] Figure 3 This is a schematic cross-sectional view illustrating an example of the membrane electrode assembly of this disclosure. Detailed Implementation

[0059] Unless otherwise specified, the definitions of the following terms apply to the entire scope of this specification and the claims.

[0060] "Ion exchange group" refers to a group that can exchange at least a portion of the ions contained in the group for other ions. For example, sulfonic acid functional groups and carboxylic acid functional groups can be listed below.

[0061] "Sulfonic acid functional group" refers to a sulfonic acid group (-SO3H) or a sulfonate group. Examples of sulfonate groups include (-SO3H). - Ma + (-SO3-)2Mb 2+ and (-SO3) - 3Mc 3+ (where Ma) + Mb is an alkali metal ion or a quaternary ammonium cation. 2+ Mc is a divalent metal ion. 3+(For trivalent metal ions). It should be noted that when there are 2 ligands, the number of ion exchange groups is 2, and when there are 3 ligands, the number of ion exchange groups is 3.

[0062] "Carboxylic acid type functional group" refers to a carboxylic acid group (-COOH) or a carboxylate group. Here, examples of carboxylate groups include (-COO)... - Ma + 、(-COO - 2Mb 2+ and (-COO) - 3Mc 3+ (where Ma) + Mb is an alkali metal ion or a quaternary ammonium cation. 2+ Mc is a divalent metal ion. 3+ (The metal ion is trivalent). It should be noted that when there are 2 ligands, the number of ion exchange groups is 2, and when there are 3 ligands, the number of ion exchange groups is 3.

[0063] "Precursor membrane" refers to a membrane containing polymers with groups that can be converted into ion exchange groups.

[0064] "A group that can be converted into an ion exchange group" refers to a group that can be converted into an ion exchange group through treatments such as hydrolysis or acidification.

[0065] "A group that can be converted into a sulfonic acid functional group" refers to a group that can be converted into a sulfonic acid functional group through treatments such as hydrolysis or acidification.

[0066] "A group that can be converted into a carboxylic acid functional group" refers to a group that can be converted into a carboxylic acid functional group through known treatments such as hydrolysis or acidification.

[0067] In polymers, a "unit" refers to a group of atoms based on one molecule of that monomer, formed through the polymerization of the monomer. A unit can be a group of atoms formed directly through the polymerization reaction, or it can be a group of atoms whose structure is transformed by processing the polymer obtained through the polymerization reaction.

[0068] The numerical range indicated by "~" refers to the range including the values ​​recorded before and after "~" as both lower and upper limits. Within the numerical ranges described in this specification, the upper or lower limit recorded in a particular numerical range can be replaced by the upper or lower limit of other numerical ranges described in different stages. Furthermore, within the numerical ranges described in this specification, the upper or lower limit recorded in a particular numerical range can also be replaced by the values ​​shown in the embodiments.

[0069] The present disclosure will now be described in detail with reference to the accompanying drawings. The description of the constituent elements described below is sometimes based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.

[0070] In the manner shown in the accompanying drawings, to make visual confirmation and explanation easier, the constituent elements are sometimes depicted at a scale different from the actual scale.

[0071] [Electrolyte membrane]

[0072] Figure 1 This is a cross-sectional view schematically illustrating an example of the composition of the solid polymer electrolyte membrane (hereinafter also simply referred to as "electrolyte membrane") of this disclosure.

[0073] The electrolyte membrane 10 disclosed herein has a first layer 11, a second layer 12, and a reinforcement 13. As shown in the figure, among the surfaces (main surfaces) of the electrolyte membrane 10, the surface of the first layer side 11 is referred to as "surface A", and the surface of the second layer side 12 is referred to as "surface B". In addition, the surface located at the center in the thickness direction of the electrolyte membrane 10 is referred to as "central surface C", and the interface between the first layer 11 and the second layer 12 is referred to as "interface D".

[0074] The first layer 11 comprises a first fluoropolymer having ion-exchange groups (hereinafter also referred to as "fluoropolymer (I-1)") and a platinum-containing compound, and the second layer 12 comprises a second fluoropolymer having ion-exchange groups (hereinafter also referred to as "fluoropolymer (I-2)"). In the electrolyte membrane 10 of this disclosure, the concentration of the platinum-containing compound in the first layer 11 is higher than the concentration of the platinum-containing compound in the second layer 12. Therefore, it can be said that the platinum-containing compound is more concentrated on surface A side of the electrolyte membrane 10. In addition, the ion exchange capacity of the fluoropolymer (I-1) contained in the first layer 11 is greater than the ion exchange capacity of the fluoropolymer (I-2) contained in the second layer 12.

[0075] As shown in the figure, the reinforcement 13 is disposed closer to the surface A side of the first layer 11 than the central surface C located at the center position in the thickness direction of the electrolyte membrane 10 (hereinafter also referred to as "disposed on the surface A side"). This can also be seen from the fact that the thickness T1 of the first layer 11 is thinner than the thickness T2 of the second layer 12, and the reinforcement 13 is disposed at the interface D between the first layer 11 and the second layer 12.

[0076] When applied to a water electrolysis device, the electrolyte membrane disclosed herein can suppress curling and hydrogen permeation. The exact reasons for this are not yet clear, but it is presumed to be due to the following factors.

[0077] It is speculated that when the electrolyte membrane of this disclosure is applied to a water electrolysis device, the ion exchange capacity of the fluorinated polymer contained in the first layer is greater than that of the fluorinated polymer contained in the second layer. In addition, the hydrogen generated on the cathode side reacts with the oxygen generated on the anode side at least on the platinum-containing material contained in the first layer to become water, thereby suppressing the movement of hydrogen to the anode side (hydrogen permeation).

[0078] Furthermore, it is believed that the fluorinated polymer (I-1) with a relatively large ion exchange capacity has a relatively high content of ion exchange groups, while the fluorinated polymer (I-2) with a relatively small ion exchange capacity has a relatively low content of ion exchange groups. It is speculated that because the content of ion exchange groups of the fluorinated polymers contained in the two laminated layers differs, the dimensional change rate of each layer differs, leading to curling of the laminate. In the electrolyte membrane of this disclosure, it is believed that by disposing a reinforcing body that improves the strength of the electrolyte membrane on surface A of the first layer with a relatively high content of ion exchange groups, the curling of the first and second layers with different ion exchange capacities can be suppressed.

[0079] By suppressing the formation of curl in the electrolyte membrane, damage to the surface of the catalyst layer caused by contact between the catalyst layer formed on the surface of the electrolyte membrane and the end of the electrolyte membrane can be suppressed.

[0080] Figure 1 In the electrolyte membrane 10 shown, the thickness T1 of the first layer 11 is thinner than the thickness T2 of the second layer 12, and the reinforcement 13 is disposed at the interface D between the first layer 11 and the second layer 12.

[0081] However, the electrolyte membrane of this disclosure is not limited to the following as long as the concentration of the platinum-containing material in the first layer 11 is higher than the concentration of the platinum-containing material in the second layer 12, the ion exchange capacity of the fluoropolymer (I-1) is greater than the ion exchange capacity of the fluoropolymer (I-2), and the reinforcement is disposed on the surface A side. Figure 1 The structure shown.

[0082] For example, in the electrolyte membrane of this disclosure, the thickness of the first layer and the second layer, as well as the position of the reinforcement, can be selected.

[0083] Figure 2 This is a cross-sectional view schematically illustrating another example of the composition of the electrolyte membrane of this disclosure.

[0084] Figure 2 The electrolyte membrane 20 of this disclosure shown has a first layer 11, a second layer 12 and a reinforcement 13. Figure 2 The meaning of each symbol and the function of each component, etc. Figure 1 same.

[0085] Figure 1In the electrolyte membrane 10 shown, the reinforcement 13 is disposed at the interface D between the first layer 11 and the second layer 12, but Figure 2 In the electrolyte membrane 20 shown, the reinforcement 13 is disposed inside the second layer 12 and located between the central surface C and the interface D at the center position in the thickness direction of the electrolyte membrane 20. The desired effect can also be obtained by using an electrolyte membrane 20 with such a reinforcement 13.

[0086] The reinforcement can also be disposed within the first layer. For example, in an electrolyte membrane where the thickness T1 of the first layer is thinner than the thickness T2 of the second layer, the reinforcement can also be disposed between the interface D and the surface A.

[0087] In addition, Figure 1 In the electrolyte membrane 10 shown, the thickness T1 of the first layer is thinner than the thickness T2 of the second layer, but the thickness T1 of the first layer can be the same as the thickness T2 of the second layer, or it can be thicker than the thickness T2 of the second layer. The thickness T1 of the first layer is preferably less than or equal to the thickness T2 of the second layer, and more preferably thinner than the thickness T2 of the second layer.

[0088] The composition and physical properties of the electrolyte membrane disclosed herein will be described in more detail below.

[0089] [First Layer]

[0090] The first layer contains a fluoropolymer (I-1) and a platinum-containing compound.

[0091] The first layer may contain components other than fluoropolymers (I-1) and platinum-containing substances. Cerium oxide is one such component.

[0092] exist Figure 1 and Figure 2 The example shows the case where the first layer is a single layer, but the first layer can also be a multilayer structure composed of multiple layers. In the case where the first layer is a multilayer structure, the composition, ion exchange capacity and content, type and content of platinum-containing substances, and other components in the single layers constituting the multilayer structure can be the same or different.

[0093] In an electrolyte membrane, the first and second layers can be distinguished, for example, by the content of platinum. Specifically, using the average concentration of platinum in the thickness direction of the electrolyte membrane as a reference, the region where the concentration of platinum is above the average value is designated as the first layer, and the region where the concentration of platinum is below the average value is designated as the second layer.

[0094] The method for determining the concentration of platinum-containing substances in the thickness direction of the electrolyte membrane will be described later.

[0095] <Fluoropolymer (I-1)>

[0096] The first layer may contain one type of fluoropolymer (I-1) or two or more types of fluoropolymer (I-1).

[0097] The first layer may contain polymers other than the fluoropolymer (I-1), but is preferably substantially composed of the fluoropolymer (I-1). "Substantially composed of the fluoropolymer (I-1)" means that the content of the fluoropolymer (I-1) is 90% by mass or more relative to the total mass of the polymers in the first layer. The upper limit of the content of the fluoropolymer (I-1) is 100% by mass relative to the total mass of the polymers in the first layer.

[0098] As specific examples of polymers other than fluoropolymers (I-1), one or more polyazole compounds selected from the group consisting of polymers of heterocyclic compounds containing one or more nitrogen atoms in the ring and polymers of heterocyclic compounds containing one or more nitrogen atoms in the ring and containing oxygen atoms and / or sulfur atoms can be listed.

[0099] Specific examples of polyazole compounds include polyimidazolium compounds, polybenzimidazole compounds, polybenzimidazole compounds, polybenzoxazole compounds, polyoxazole compounds, polythiazole compounds, and polybenzothiazole compounds.

[0100] In addition, from the viewpoint of the oxidation resistance of the electrolyte membrane, other polymers that can be listed include polyphenylene sulfide resin and polyphenylene ether resin.

[0101] The fluoropolymer (I-1) has ion-exchange groups. Specific examples of ion-exchange groups include sulfonic acid type functional groups and carboxylic acid type functional groups. From the viewpoint that the electrolysis voltage can be further reduced when the electrolyte membrane is applied to a water electrolysis device, sulfonic acid type functional groups are preferred.

[0102] The following section provides a detailed description of fluoropolymers with sulfonic acid functional groups (hereinafter also referred to as "fluoropolymers (S)").

[0103] The fluoropolymer (S) preferably comprises units based on fluoroolefins and units having sulfonic acid functional groups and fluorine atoms.

[0104] Examples of fluorinated olefins include 2- to 3-carbon fluoroolefins having one or more fluorine atoms in their molecules. Specific examples of fluorinated olefins include tetrafluoroethylene (hereinafter also referred to as "TFE"), trifluorochloroethylene, vinylidene fluoride, vinyl fluoride, and hexafluoropropylene. Among these, TFE is preferred from the viewpoint of monomer manufacturing cost, reactivity with other monomers, and superior properties of the resulting fluoropolymer (S).

[0105] Fluorinated olefins can be used alone or in combination of two or more.

[0106] As a unit having sulfonic acid functional groups and fluorine atoms, the unit shown in formula (1) is preferred.

[0107]

[0108] L is an optional perfluorocarbon group with an n+1 valence containing an ether-type oxygen atom.

[0109] The oxygen atom in an ether can be located at the end of a perfluorocarbon group or between carbon atoms.

[0110] The number of carbons in the n+1 valence perfluorocarbon group is preferably 1 or more, more preferably 2 or more, and further preferably 20 or less, more preferably 10 or less.

[0111] As L, preferably a perfluoroaliphatic hydrocarbon group with an n+1 valence containing an ether oxygen atom is preferred, more preferably a perfluoroalkylene group with a divalent valence containing an ether oxygen atom as n=1, or a perfluoroaliphatic hydrocarbon group with a trivalent valence containing an ether oxygen atom as n=2.

[0112] The aforementioned divalent perfluoroalkylene groups can be either straight-chain or branched.

[0113] M can be a hydrogen atom, an alkali metal, or a quaternary ammonium cation. The n M's can be the same or different.

[0114] n is 1 or 2.

[0115] As the unit shown in formula (1), the unit shown in formula (1-1), the unit shown in formula (1-2), the unit shown in formula (1-3), or the unit shown in formula (1-4) are preferred.

[0116]

[0117]

[0118]

[0119]

[0120] R f1 The perfluoroalkylene group is a perfluoroalkylene group in which oxygen atoms are optionally present between carbon atoms. Preferably, the perfluoroalkylene group has 1 or more carbon atoms, more preferably 2 or more, and further preferably 20 or less, more preferably 10 or less.

[0121] R f2 It is a perfluoroalkylene group that is a single bond or optionally contains an oxygen atom between carbon atoms. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, and further preferably 20 or less, more preferably 10 or less.

[0122] Rf3 It is a perfluoroalkylene group that is a single bond or optionally contains an oxygen atom between carbon atoms. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, and further preferably 20 or less, more preferably 10 or less.

[0123] r is 0 or 1.

[0124] m is 0 or 1.

[0125] M is as described above.

[0126] As for the unit shown in formula (1-1) and the unit shown in formula (1-2), the unit shown in formula (1-5) is more preferred.

[0127]

[0128] x is 0 or 1, y is an integer from 0 to 2, z is an integer from 1 to 4, and Y is F or CF3. M is as described above.

[0129] As specific examples of the unit shown in equation (1-1), the following units can be listed. In the equation, w is an integer from 1 to 8, and v is an integer from 1 to 5. The definition of M in the equation is as described above.

[0130]

[0131] As specific examples of the unit shown in equation (1-2), the following units can be listed. In the equation, w is an integer from 1 to 8. The definition of M in the equation is as described above.

[0132]

[0133] As the unit shown in equation (1-3), the unit shown in equation (1-3-1) is preferred. The definition of M in the equation is as described above.

[0134]

[0135] R f4 It is a straight-chain perfluoroalkylene group with 1 to 6 carbon atoms, R f5 It is a straight-chain perfluoroalkylene group with 1 to 6 carbon atoms, consisting of a single bond or optionally containing an oxygen atom between carbon atoms. The definitions of r and M are as described above.

[0136] The following are specific examples of the unit shown in equation (1-3-1).

[0137]

[0138] As the unit shown in equation (1-4), the unit shown in equation (1-4-1) is preferred. R in the equation... f1 R f2 The definitions of M and M are as described above.

[0139]

[0140] The following are specific examples of the unit shown in equation (1-4-1).

[0141]

[0142] Units with sulfonic acid functional groups and fluorine atoms can be used alone or in combination of two or more.

[0143] Fluoropolymers (I-1) may contain units based on fluorinated olefins, as well as units based on other monomers other than those having sulfonic acid functional groups and fluorine atoms.

[0144] As a specific example of other monomers, CF2=CFR can be cited. f6 (where R) f6 (perfluoroalkyl groups with 2 to 10 carbon atoms), CF2=CF-OR f7 (where R) f7 (where v is a perfluoroalkyl group with 1 to 10 carbon atoms), CF2=CFO(CF2)vCF=CF2 (where v is an integer from 1 to 3).

[0145] From the viewpoint of maintaining ion exchange performance, the content of units based on other monomers is preferably 30% by mass or less relative to all units in the fluoropolymer (I-1).

[0146] Regarding the ion exchange capacity of the fluoropolymer (I-1), from the viewpoint of further reducing the electrolysis voltage when the electrolyte membrane is applied to a water electrolysis device, and also from the viewpoint of suppressing hydrogen permeation, it is preferable to have a capacity of 0.90 mEq / g or more of dry resin, more preferably greater than 1.10 mEq / g of dry resin, even more preferably 1.20 mEq / g of dry resin or more, particularly preferably 1.25 mEq / g of dry resin or more, and even more preferably 1.30 mEq / g of dry resin or more.

[0147] From the viewpoint of the strength of the membrane electrode assembly in the presence of water, the ion exchange capacity of the fluoropolymer (I-1) is preferably 2.00 milliequivalents / g dry resin or less, more preferably 1.50 milliequivalents / g dry resin or less, and even more preferably 1.43 milliequivalents / g dry resin or less.

[0148] The ion exchange capacity of fluoropolymer (I-1) can be adjusted by changing the content of ion exchange groups in fluoropolymer (I-1).

[0149] The "ion exchange capacity" is the value of the ion exchange capacity per dry mass of the fluoropolymer calculated as follows: First, the fluoropolymer is placed in a glove box purged with dry nitrogen for 24 hours, and the dry mass of the fluoropolymer is measured. Then, the fluoropolymer is immersed in a 2 mol / L sodium chloride aqueous solution at 60°C for 1 hour. After rinsing the fluoropolymer with ultrapure water, it is removed, and the liquid containing the fluoropolymer is titrated with a 0.1 mol / L sodium hydroxide aqueous solution. The ion exchange capacity of the fluoropolymer is then determined.

[0150] Furthermore, the ion exchange capacity of the fluoropolymer in the thickness direction of the electrolyte membrane, the first layer, and the second layer can be calculated, for example, by measuring a cross-section of the electrolyte membrane along the thickness direction using micro Raman spectrometry. More specifically, the electrolyte membrane is cut along the thickness direction, and the resulting cross-section is measured using a micro Raman spectrometer. Based on the intensity ratio of the peaks from the TFE units to the peaks from the ion exchange groups (e.g., SO3X) in the resulting Raman spectrum, the ion exchange capacity of the fluoropolymer in the thickness direction can be calculated.

[0151] When the reinforcement is disposed inside the first layer, the content of the fluoropolymer (I-1) is preferably 80 to 99% by mass relative to the total mass of the first layer; when the reinforcement is not disposed inside the first layer, the content of the fluoropolymer (I-1) is preferably 90 to 99.9% by mass relative to the total mass of the first layer.

[0152] Platinum-containing substances

[0153] Platinum-containing compounds are compounds that contain platinum atoms. Specific examples of platinum-containing compounds include platinum itself, platinum oxides, platinum-containing complex metal oxides, and platinum alloys.

[0154] As a specific example of a platinum-containing composite oxide, MxPt3O4 can be listed (M is at least one metal atom selected from the group consisting of Li, Na, Mg, Ca, Zn, Cd, Co, Ni, Mn, Cu, Ag, Bi and Ce, and x is greater than 0 and less than 1).

[0155] As a specific example of a platinum alloy, an alloy comprising at least one metal selected from transition metals and noble metals other than platinum, and platinum.

[0156] The second layer can contain one platinum-containing compound or two or more platinum-containing compounds.

[0157] Specific examples of the shape of platinum-containing substances include granular and flake-like forms. When the platinum-containing substance is granular, it can be a core-shell type. Examples of core-shell type particles include those with a core of carbon or containing a metal other than platinum, and a shell containing platinum atoms.

[0158] When the platinum-containing material is in particulate form, the average particle size (D50) of the platinum-containing material is preferably 1 nm or more, more preferably 5 nm or more, even more preferably 10 nm or more, particularly preferably 100 nm or more, and preferably 50 μm or less, more preferably 30 μm or less, even more preferably 14 μm or less, and particularly preferably 7 μm or less. Alternatively, the average particle size (D50) of the platinum-containing material can be 500 nm or more.

[0159] The method for measuring the average particle size of platinum-containing materials is as follows.

[0160] The average particle size of the platinum-containing material was obtained by dry measuring 40,000 particle sizes using an image-based particle size distribution measuring device (such as the Malvern Panalytical "Morphologi" series, a registered trademark), and calculating the cumulative 50% diameter (D50) of the volumetric particle size distribution curve. It should be noted that in the case of particles smaller than 500 nm, the spherical equivalent diameter of 100 particles was measured using a scanning electron microscope (SEM), and the cumulative 50% diameter (D50) of the volumetric particle size distribution curve was calculated.

[0161] Platinum-containing compounds can be composed of monodisperse primary particles or secondary particles formed by the aggregation of multiple primary particles. When a platinum-containing compound contains secondary particles, the particle size of the secondary particles is measured during the D50 determination described above.

[0162] Regarding the mass of platinum-containing material in the first layer, per 1cm 2 The first surface gauge is preferably 0.005 mg / cm³. 2 The above, more preferably 0.010 mg / cm³ 2 The above is further preferred to be 0.015 mg / cm³. 2 In addition, the preferred concentration is 0.050 mg / cm³. 2 The following is more preferably 0.040 mg / cm³ 2 The following applies. When the mass of the platinum-containing material in the first layer is above the aforementioned lower limit, hydrogen permeation can be further suppressed. If the mass of the platinum-containing material in the first layer is 0.050 mg / cm³... 2 The following methods can further reduce the electrolysis voltage of the electrolyte membrane, enabling the provision of low-cost membrane electrode assemblies and water electrolysis devices.

[0163] The mass ratio of the platinum-containing material to the fluoropolymer (I-1) in the first layer (mass of platinum-containing material / mass of fluoropolymer (I-1)) is preferably 0.0005 or more, more preferably 0.004 or more, and even more preferably 0.007 or more. Furthermore, it is preferably 0.024 or less, and more preferably 0.014 or less. When the mass ratio is 0.005 or more, hydrogen permeation can be further suppressed. When the mass ratio is 0.024 or less, the electrolysis voltage of the electrolyte membrane can be further reduced, providing a low-cost membrane electrode assembly and water electrolysis device.

[0164] Platinum-containing materials can be supported on a substrate. Specific examples of substrates include carbon black powder, graphitized carbon, carbon fibers, and carbon nanotubes.

[0165] When a platinum-containing substance is loaded onto a carrier, the loading amount of the platinum-containing substance relative to the total mass of the platinum-containing substance and the carrier is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and preferably 50% by mass or less.

[0166] The location and content of platinum-containing substances in each layer of the electrolyte membrane can be determined, for example, by using an energy-dispersive X-ray analyzer (product name "QUANTAX FlatQUAD", manufactured by Bruker) through elemental distribution.

[0167] <Cerium oxide>

[0168] The first layer may further contain cerium oxide.

[0169] As will be described later, from the viewpoint of superior chemical durability of the electrolyte membrane, the electrolyte membrane preferably further comprises cerium oxide in at least one of the first layer and the second layer.

[0170] Cerium oxide can be either CeO2 (cerium oxide (IV)) or Ce2O3 (cerium oxide (III)), but from a stability point of view, CeO2 is preferred.

[0171] Cerium oxide can be doped with polyvalent metal ions such as zirconium and praseodymium.

[0172] Cerium oxide is preferably in granular form.

[0173] When cerium oxide is in granular form, the average particle size (D50) of cerium oxide is preferably 10 nm or more, more preferably 100 nm or more, even more preferably 1 μm or more, particularly preferably 3 μm or more, and preferably 30 μm or less, more preferably 14 μm or less, and even more preferably 10 μm or less.

[0174] If the average particle size of cerium oxide is greater than 10 nm, its aggregation is suppressed, and it is easy to form a stable dispersion. If the average particle size of cerium oxide is less than 30 μm, the chemical durability of the electrolyte membrane can be further improved.

[0175] The method for determining the average particle size of cerium oxide is the same as the method for determining the average particle size (D50) of platinum-containing compounds.

[0176] Every 1cm of the first layer 2 The preferred mass of cerium oxide is 0.005 mg / cm³. 2 The above, more preferably 0.010 mg / cm³ 2 The above is further preferred to be 0.015 mg / cm³. 2 In addition, the preferred concentration is 0.050 mg / cm³. 2 The following is more preferably 0.030 mg / cm³. 2 the following.

[0177] If the mass of cerium oxide is above the aforementioned lower limit, the first layer becomes whitish, making it easy to detect foreign matter present in the first layer. Therefore, when applying the electrolyte membrane to a water electrolysis device, it can be used in a way that avoids the portion of the electrolyte membrane containing foreign matter, thus suppressing the formation of pinholes in the electrolyte membrane caused by foreign matter.

[0178] When the mass of cerium oxide is below the aforementioned upper limit, the electrolysis voltage of the electrolyte membrane can be further reduced, enabling the provision of low-cost membrane electrode junctions and water electrolysis devices.

[0179] The location of cerium oxide in the electrolyte membrane can be determined, for example, by using an energy-dispersive X-ray analyzer (product name "QUANTAX FlatQUAD", manufactured by Bruker) through elemental distribution.

[0180] The thickness T1 of the first layer (the sum of the thicknesses of all layers when the first layer is a multilayer structure) is preferably 5-60 μm, more preferably 10-40 μm, and even more preferably 10-30 μm. If the thickness T1 of the first layer is above or above the lower limit mentioned above, the mechanical strength of the electrolyte membrane is improved, and the current efficiency is also better. If the thickness T1 of the first layer is below the upper limit mentioned above, the electrolysis voltage of the electrolyte membrane can be suppressed to a lower level.

[0181] The thicknesses T1 of the first layer and T2 of the second layer can be determined, for example, by observing a cross-section of the electrolyte membrane along the thickness direction using an optical microscope or similar instrument, and measuring the distance between the boundary line representing the difference in platinum concentration and each surface of the electrolyte membrane. Alternatively, if the second layer contains platinum, the concentration of platinum in the thickness direction can be determined by using an energy-dispersive X-ray analyzer (product name "QUANTAX FlatQUAD", manufactured by Bruker) based on the elemental distribution of the cross-section of the electrolyte membrane along the thickness direction.

[0182] [Second Layer]

[0183] The second layer contains a fluoropolymer (I-2) with ion-exchange groups and an ion-exchange capacity smaller than that of the fluoropolymer (I-1).

[0184] The second layer may contain components other than fluoropolymers (I-2). Examples of such components include platinum-containing compounds and cerium oxide.

[0185] The second layer can be a single layer or a multilayer structure composed of multiple layers. In the case of a multilayer structure, the composition, ion exchange capacity and content of the fluoropolymer (I-2), as well as the types and contents of other components, can be the same or different in the single layers constituting the multilayer structure.

[0186] When the second layer is a multilayer structure, it is preferable that the ion exchange capacity of the fluorinated polymer (I-2) contained in each layer constituting the multilayer structure is smaller than that of the fluorinated polymer (I-1) contained in the first layer.

[0187] Fluoropolymer (I-2)

[0188] The second layer may contain one type of fluoropolymer (I-2) or two or more types of fluoropolymer (I-2).

[0189] The second layer may contain polymers other than fluoropolymer (I-2), but is preferably substantially composed of fluoropolymer (I-2). Substantially composed of fluoropolymer (I-2) means that the content of fluoropolymer (I-2) is 90% by mass or more relative to the total mass of the polymers in the second layer. The upper limit of the content of fluoropolymer (I-2) is 100% by mass relative to the total mass of the polymers in the second layer.

[0190] Specific examples of polymers other than fluoropolymers (I-2) are the same as those of polymers other than fluoropolymers (I-1) mentioned above.

[0191] Besides the difference in ion exchange capacity, the fluoropolymer (I-2) also has the preferred method of using the same polymer as the fluoropolymer (I-1).

[0192] Regarding the ion exchange capacity of the fluoropolymer (I-2), from the viewpoint of further reducing the electrolysis voltage when the electrolyte membrane is applied to a water electrolysis device, it is preferable to have a capacity of 0.90 mE / g dry resin or more, more preferably greater than 1.10 mE / g dry resin, further preferably 1.15 mE / g dry resin or more, particularly preferably 1.20 mE / g dry resin or more, and most preferably 1.25 mE / g dry resin or more.

[0193] From the viewpoint of the strength of the membrane electrode assembly in the presence of water, the ion exchange capacity of the fluoropolymer (I-2) is preferably 2.00 mEq / g dry resin or less, more preferably 1.50 mEq / g dry resin or less, and even more preferably 1.43 mEq / g dry resin or less.

[0194] In the electrolyte membrane of this disclosure, the ion exchange capacity of the fluoropolymer (I-1) contained in the first layer is greater than that of the fluoropolymer (I-2) contained in the second layer. Therefore, even in the first layer with a high concentration of platinum, the electrolysis voltage can be reduced. Furthermore, hydrogen permeation can be suppressed.

[0195] Regarding the absolute value of the difference between the ion exchange capacity of the fluoropolymer (I-1) and the ion exchange capacity of the fluoropolymer (I-2), from the viewpoint of lowering the electrolysis voltage and suppressing hydrogen permeation, 0.10 to 1.40 milliequivalents / g of dry resin is preferred, 0.10 to 0.70 milliequivalents / g of dry resin is more preferred, 0.01 to 0.50 milliequivalents / g of dry resin is even more preferred, and 0.10 to 0.30 milliequivalents / g of dry resin is particularly preferred.

[0196] The ion exchange capacity of fluoropolymer (I-2) can be adjusted by changing the content of ion exchange groups in fluoropolymer (I-2).

[0197] Platinum-containing substances

[0198] The concentration of platinum in the second layer is lower than that in the first layer.

[0199] The second layer may contain platinum-containing substances at a lower concentration than the first layer, or it may not contain platinum-containing substances at all. From the viewpoint that the electrolysis voltage can be reduced by decreasing the amount of platinum in the electrolyte membrane, which does not contribute to ion conduction, the second layer is preferably free of platinum-containing substances.

[0200] Here, "free of platinum" means that every 1 cm of the second membrane... 2The mass of the platinum-containing substance is 0.001 mg / cm³. 2 the following.

[0201] When the second layer contains platinum, the mass of the platinum in the second layer is calculated per 1 cm. 2 The second surface gauge is preferably 0.050 mg / cm³. 2 The following is more preferably 0.040 mg / cm³ 2 Below, a concentration of less than 0.015 mg / cm³ is further preferred. 2 Additionally, 0.005 mg / cm³ is preferred. 2 That's all. If the mass of the platinum-containing material in the second layer is below the above-mentioned upper limit, hydrogen permeation can be further suppressed.

[0202] From the viewpoint of achieving superior effects of the present invention, the absolute value of the difference between the mass of the platinum-containing material contained in the first layer and the mass of the platinum-containing material contained in the second layer is expressed as per 1 cm of the electrolyte membrane. 2 The preferred concentration is 0.010 mg / cm³. 2 The above, more preferably 0.015 mg / cm³ 2 The above is further preferred to be 0.030 mg / cm³. 2 The above, especially preferred, is 0.040 mg / cm³. 2 The concentration is above, and preferably 0.050 mg / cm³. 2 the following.

[0203] The second layer may further contain cerium oxide.

[0204] The cerium oxide contained in the second layer also includes, in its preferred manner, the same as that contained in the first layer.

[0205] When the second film contains cerium oxide, the second layer per 1 cm 2 The preferred mass of cerium oxide is 0.005 mg / cm³. 2 The above, more preferably 0.010 mg / cm³ 2 The above is further preferred to be 0.015 mg / cm³. 2 In addition, the preferred concentration is 0.100 mg / cm³. 2 The following is more preferably 0.050 mg / cm³. 2 Hereinafter, 0.030 mg / cm³ is further preferred. 2 the following.

[0206] The reasons for the preferred range of cerium oxide quality mentioned above are as explained for the cerium oxide contained in the first layer.

[0207] Every 1cm of the second layer 2The mass of cerium oxide can be lower than that of the first layer per 1 cm. 2 The mass of cerium oxide. In this case, the absolute value of the difference between the mass of cerium oxide contained in the second layer and the mass of cerium oxide contained in the first layer is expressed as per 1 cm of the electrolyte membrane. 2 The optimal concentration is 0.005 mg / cm³. 2 The above is preferred, and 0.015 mg / cm³ is also preferred. 2 the following.

[0208] Alternatively, the second layer may not contain cerium oxide. Here, "not containing cerium oxide" means that per 1 cm... 2 The mass of cerium oxide is 0.001 mg / cm³. 2 the following.

[0209] As another method, every 1cm of the first layer 2 The mass of cerium oxide can be lower than that of the second layer per 1 cm. 2 The mass of cerium oxide. In this case, the absolute value of the difference between the mass of cerium oxide contained in the first layer and the mass of cerium oxide contained in the second layer is expressed as per 1 cm of the electrolyte membrane. 2 The optimal concentration is 0.005 mg / cm³. 2 The concentration is above, and preferably 0.015 mg / cm³. 2 the following.

[0210] Alternatively, the first layer may not contain cerium oxide.

[0211] The thickness T2 of the second layer (or the total thickness when the second layer is a multilayer structure) is preferably 40-120 μm, more preferably 40-110 μm, and even more preferably 40-90 μm. If the thickness T2 of the second layer is above or above the lower limit mentioned above, the mechanical strength of the electrolyte membrane is improved, and the current efficiency is also better. If the thickness T2 of the second layer is below the upper limit mentioned above, the electrolysis voltage of the electrolyte membrane can be suppressed to a lower level.

[0212] The thickness T1 of the first layer is preferably less than or equal to the thickness T2 of the second layer, and more preferably thinner than the thickness T2 of the second layer. By reducing the thickness T1 of the first layer while maintaining the total thickness of the first layer T1 and the second layer T2 above a predetermined value, the density of the platinum-containing material in the first layer is increased, thereby further suppressing hydrogen permeation.

[0213] From the viewpoint of superior formability during the manufacture of the electrolyte membrane, the ratio of the thickness T1 of the first layer to the total thickness of the first layer and the second layer (i.e., T1 / (T1+T2)) is preferably 0.50 or less, more preferably 0.42 or less, even more preferably 0.33 or less, particularly preferably 0.17 or less, and preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.08 or more.

[0214] From the viewpoint of being able to suppress hydrogen permeation, the combined thickness of the first layer thickness T1 and the second layer thickness T2 is preferably 30 μm or more, more preferably 400 μm or less, more preferably 300 μm or less, further preferably 200 μm or less, especially preferably 90 μm or less, and most preferably 60 μm or less.

[0215] [Enhanced]

[0216] The reinforcement plays a role in improving the dimensional stability, strength, and operability of the electrolyte membrane.

[0217] Specific examples of reinforcements include porous materials, fibers, woven fabrics and nonwoven fabrics, with woven fabrics being preferred.

[0218] The reinforcement is preferably composed of mutually orthogonal warp and weft yarns.

[0219] From the viewpoint of further reducing the electrolysis voltage, the opening ratio of the reinforcement is preferably 50% or more, more preferably 55% or more, even more preferably 60% or more, and particularly preferably 70% or more.

[0220] From the viewpoint of achieving superior strength of the electrolyte membrane, the upper limit of the opening ratio of the reinforcement is preferably 90% or less, and more preferably 80% or less.

[0221] The opening ratio of the reinforcement is calculated using the following formula (ε) based on the average diameter R1 of the yarn constituting the reinforcement and the average spacing P1 between adjacent yarns in the yarn constituting the reinforcement (hereinafter also referred to as "spacing P1").

[0222] Here, the average yarn diameter R1 refers to the arithmetic mean of the diameters of 10 randomly selected yarns from a magnified image (e.g., 100x) of the surface of the reinforcing body obtained using a microscope. Additionally, the spacing P1 refers to the arithmetic mean of 10 randomly selected points at intervals from different locations within the magnified image (e.g., 100x) of the surface of the reinforcing body obtained using a microscope.

[0223] The aperture ratio (%) of the reinforcement is calculated as follows: [P1 / (P1+R1)] 2 ×100(ε)

[0224] The denier number of the yarn constituting the reinforcement is preferably 2 or more, and from the viewpoint of having better strength and dimensional stability of the electrolyte membrane, it is more preferably 10 or more, and particularly preferably 15 or more.

[0225] From the viewpoint of being able to further reduce the electrolysis voltage, the upper limit of the denier number of the yarn constituting the reinforcement is preferably 60 or less, more preferably 50 or less, and particularly preferably 20 or less.

[0226] It should be noted that denier number is a value in grams (g / 9000m) representing the mass of 9000m yarn.

[0227] From the viewpoint of excellent strength and dimensional stability of the electrolyte membrane, the density of the yarn constituting the reinforcement is preferably 50 threads / inch or more, more preferably 70 threads / inch or more, particularly preferably 90 threads / inch or more, and from the viewpoint of being able to further reduce the electrolysis voltage, it is preferably 200 threads / inch or less, more preferably 150 threads / inch or less, and even more preferably 100 threads / inch or less.

[0228] The yarn constituting the reinforcement can be composed of either a monofilament containing one filament or a multifilament containing two or more filaments, with monofilament being preferred.

[0229] From the viewpoint of superior yarn durability, the reinforcement (more preferably the fabric) is preferably composed of a material selected from the group consisting of polytetrafluoroethylene (hereinafter also referred to as "PTFE"), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter also referred to as "PFA"), polyether ether ketone (hereinafter also referred to as "PEEK"), and polyphenylene sulfide (hereinafter also referred to as "PPS").

[0230] From the viewpoint of superior yarn durability and strength, the yarn constituting the reinforcement is preferably composed of cut film filaments.

[0231] When the reinforcing material is PTFE, from the viewpoint of achieving an excellent balance between the strength and operability of the electrolyte membrane, the weight per unit area of ​​the reinforcing material is preferably 20 g / m². 2 The above, more preferably 30g / m 2 In addition, the preferred value is 40g / m 2 the following.

[0232] When the reinforcing material is PFA, from the viewpoint of achieving an excellent balance between the strength and operability of the electrolyte membrane, the weight per unit area of ​​the reinforcing material is preferably 10 g / m². 2 In addition, the preferred value is 30g / m³. 2 The following is more preferably 20g / m 2 the following.

[0233] When the reinforcing material is PEEK, from the viewpoint of achieving an excellent balance between the strength and operability of the electrolyte membrane, the weight per unit area of ​​the reinforcing material is preferably 5 g / m². 2 In addition, the preferred value is 40g / m 2 The following is more preferably 30g / m 2 the following.

[0234] When the reinforcing material is PPS, from the viewpoint of achieving an excellent balance between the strength and operability of the electrolyte membrane, the weight per unit area of ​​the reinforcing material is preferably 5 g / m². 2 In addition, the preferred value is 40g / m 2 The following is more preferably 30g / m 2 the following.

[0235] The content of the reinforcing agent relative to the total mass of the electrolyte membrane is preferably 3% by mass or more, more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0236] The reinforcing agent can be disposed inside the first layer, inside the second layer, or at the interface between the first and second layers. However, from the viewpoint of suppressing the formation of curl in the electrolyte membrane, it is preferred to dispose of it at the interface between the first and second layers.

[0237] The electrolyte membrane may also have other components besides the first layer, the second layer and the reinforcement, but it is preferred to have an electrolyte membrane consisting of the first layer, the second layer and the reinforcement without having other components.

[0238] Every 1 cm of electrolyte membrane 2 The preferred mass of the platinum-containing compound is 0.005 mg / cm³. 2 More preferably 0.010 mg / cm³ 2 The above is further preferred to be 0.015 mg / cm³. 2 In addition, the preferred concentration is 0.050 mg / cm³. 2 Below, 0.040 mg / cm³ is more preferred. 2 The following applies if the mass of the platinum-containing substance is 0.015 mg / cm³. 2 The above can further inhibit hydrogen permeation. If the mass of the platinum-containing substance is 0.050 mg / cm³, 2 The following methods can further reduce the electrolysis voltage, enabling the provision of low-cost membrane electrode assemblies and water electrolysis devices.

[0239] From the viewpoint of suppressing hydrogen permeation, the second layer in the electrolyte membrane preferably does not contain platinum. When the second layer does not contain platinum, the thickness T1 of the first layer is preferably 50% or less of the thickness of the electrolyte membrane (the total thickness of the first layer T1 and the second layer T2), more preferably 42% or less of the thickness of the electrolyte membrane, even more preferably 33% or less of the thickness of the electrolyte membrane, and particularly preferably 17% or less of the thickness of the electrolyte membrane.

[0240] The electrolyte membrane preferably also contains cerium oxide.

[0241] It can be assumed that the chemical durability of the electrolyte membrane is improved when cerium oxide is also present. This is presumably because, when the electrolyte membrane is applied to a water electrolysis device, the OH radicals generated by hydrogen peroxide produced in the system during operation are quenched by cerium ions dissociated from the cerium oxide contained in the electrolyte membrane. As a result, the decomposition of fluoropolymers is inhibited.

[0242] Regarding the cerium oxide contained in the electrolyte, including its preferred manner, as already described.

[0243] The cerium oxide contained in the electrolyte membrane can be dispersed throughout the entire electrolyte membrane or concentrated on one surface side of the electrolyte membrane. For example, the concentration of cerium oxide in the first layer can be higher, lower, or the same as the concentration of cerium oxide in the second layer. Preferably, the concentration of cerium oxide in the first layer is higher than the concentration of cerium oxide in the second layer, and more preferably, the first layer contains cerium oxide and the second layer does not contain cerium oxide.

[0244] Because the electrolyte membrane has a high membrane resistance, it is preferable that it is substantially free of thickener. Substantially free of thickener means that the thickener content relative to the total mass of the electrolyte membrane is 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0% by mass.

[0245] Examples of thickeners include those contained in the catalyst layers of both the anode and cathode. Thickeners contained in the catalyst layers will be discussed later.

[0246] [Physical properties of electrolyte membranes]

[0247] The thickness of the electrolyte membrane is preferably 30 μm or more, further preferably 400 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, particularly preferably 90 μm or less, and most preferably 60 μm or less. The thickness of the electrolyte membrane can be the combined thickness of the first layer thickness T1 and the second layer thickness T2 described above.

[0248] Regarding the thickness of the electrolyte membrane, a magnified image (e.g., 100x) of a cross-section of the electrolyte membrane along its thickness direction, taken with an optical microscope (product name "BX-51", manufactured by Olympus Corporation), is used to measure the thickness at any 20 points. The arithmetic mean of the obtained thicknesses is taken as the thickness of the electrolyte membrane. It should be noted that if the surface of the electrolyte membrane is uneven, the thicknesses of the concave portions at 10 points and the thicknesses of the convex portions at 10 points are measured, and the arithmetic mean of the total thicknesses of these 20 points is taken as the thickness of the electrolyte membrane. Where the convex portion includes a portion constituting a reinforcement, the thickness of the convex portion is the value obtained by subtracting the thickness of the portion present in the convex portion.

[0249] <Methods for manufacturing electrolyte membranes>

[0250] As an example of a method for manufacturing an electrolyte membrane, the following methods can be listed.

[0251] First, prepare the following polymer (hereinafter also referred to as "fluoropolymer (I'-1)"): a polymer of a fluorinated monomer having groups capable of being converted into ion exchange groups, and adjust the content of groups capable of being converted into ion exchange groups in a manner similar to obtaining fluoropolymer (I-1). Next, prepare the following polymer (hereinafter also referred to as "fluoropolymer (I'-2)"): a polymer of a fluorinated monomer having groups capable of being converted into ion exchange groups, and adjust the content of groups capable of being converted into ion exchange groups in a manner similar to obtaining fluoropolymer (I-2).

[0252] Next, by melt extrusion, compound A' containing fluoropolymer (I'-1) and platinum is extruded into a film to obtain precursor film A. Similarly, by melt extrusion, compound B' containing at least fluoropolymer (I'-2) is extruded into a film to obtain precursor film B. Here, by using compound B' which does not contain platinum, precursor film B which does not contain platinum can be obtained. When using compound B' which further contains platinum, the platinum content in compound B' is adjusted so that the concentration of platinum in precursor film B is lower than the concentration of platinum in precursor film A.

[0253] It should be noted that when fabricating precursor membranes A and B, the thickness T of precursor membrane A is... A The thickness T of the precursor membrane B B Adjustments were made using a thinner method.

[0254] Next, precursor membrane A, reinforcement, and precursor membrane B are sequentially prepared and stacked using a laminating roller, vacuum laminating device, or hot pressing device to obtain a laminate. Then, by converting the groups in precursor membranes A and B that can be converted into ion exchange groups into ion exchange groups, the desired result is obtained as follows: Figure 1The electrolyte membrane shown has a first layer, a reinforcement, and a second layer. In the electrolyte membrane thus obtained, the concentration of platinum in the second layer is lower than the concentration of platinum in the first layer, the ion exchange capacity of the fluoropolymer (I-1) contained in the first layer is greater than the ion exchange capacity of the fluoropolymer (I-2) contained in the second layer, and the reinforcement is arranged closer to surface A than the center position in the thickness direction of the electrolyte membrane.

[0255] Other examples of methods for manufacturing electrolyte membranes include the following methods.

[0256] First, the groups in the fluoropolymer (I'-1) that can be converted into ion exchange groups are converted into ion exchange groups to obtain the fluoropolymer (I-1). Next, using a dispersion A containing the fluoropolymer (I-1) and a platinum-containing compound, an electrolyte membrane A (equivalent to the first layer) is obtained by casting.

[0257] Furthermore, the groups in the fluoropolymer (I'-2) that can be converted into ion exchange groups are converted into ion exchange groups to obtain the fluoropolymer (I-2). Next, using a dispersion B containing the fluoropolymer (I-2), an electrolyte membrane B (equivalent to the second layer) is obtained by casting. Here, by using a dispersion B that does not contain platinum, an electrolyte membrane B that does not contain platinum is obtained. Alternatively, when using a dispersion B that also contains platinum, the platinum content in the dispersion B is adjusted so that the concentration of platinum in the electrolyte membrane B is lower than the concentration of platinum in the electrolyte membrane A.

[0258] It should be noted that when fabricating electrolyte membranes A and B, the thickness T of electrolyte membrane A is... A Adjusted to a thickness T greater than that of electrolyte membrane B B Thin.

[0259] Next, electrolyte membrane A, reinforcement, and electrolyte membrane B are sequentially prepared and stacked using laminating rollers, a vacuum laminating device, or a hot press to obtain... Figure 1 An electrolyte membrane having a first layer, a reinforcement, and a second layer, as shown.

[0260] Other examples of methods for manufacturing electrolyte membranes include the following methods.

[0261] First, electrolyte membrane A and electrolyte membrane B are obtained according to the above method.

[0262] Next, after impregnating the reinforcement in a dispersion B containing the fluoropolymer (I-2), it is dried to obtain an electrolyte membrane C containing the fluoropolymer (I-2) and the reinforcement (equivalent to a second layer containing the reinforcement inside).

[0263] Furthermore, when fabricating electrolyte membranes A, B, and C, the thickness T of electrolyte membrane A is used as the reference. A and the thickness T of the electrolyte membrane C C The total ratio of the thickness T of electrolyte membrane B B Adjustments were made using a thinner method.

[0264] Next, electrolyte membrane A, electrolyte membrane C, and electrolyte membrane B are sequentially prepared and stacked using a stacking roller, vacuum stacking device, or hot press device to obtain... Figure 2 An electrolyte membrane having a first layer, a reinforcement, and a second layer, as shown.

[0265] Other examples of methods for manufacturing electrolyte membranes include the following methods.

[0266] First, the groups in the fluoropolymer (I'-1) that can be converted into ion exchange groups are converted into ion exchange groups to obtain the fluoropolymer (I-1). Next, the reinforcing agent is impregnated in a dispersion A containing the fluoropolymer (I-1) and a platinum-containing compound, and then dried to obtain an electrolyte membrane A containing the fluoropolymer (I-1) and the reinforcing agent (equivalent to a first layer containing the reinforcing agent internally).

[0267] In addition, electrolyte membrane B was obtained according to the above method.

[0268] It should be noted that when fabricating electrolyte membranes A and B, the thickness T of electrolyte membrane A is... A Adjusted to a thickness T greater than that of electrolyte membrane B B Thin.

[0269] Next, electrolyte membrane A and electrolyte membrane B, which contain reinforcements, are laminated using a laminating roller, a vacuum laminating device, or a hot pressing device to obtain an electrolyte membrane having a first layer, a reinforcement, and a second layer.

[0270] In the above manufacturing method, an electrolyte membrane containing cerium oxide can be obtained by adding cerium oxide to at least one of compound A' and compound B', or to at least one of dispersion A and dispersion B.

[0271] <Fluoropolymers (I'-1) and (I'-2)>

[0272] The fluoropolymers (I'-1) and (I'-2) differ in the content of groups capable of being converted into ion exchange groups. Regarding fluoropolymers (I'-1) and (I'-2), their structures, except for the content of groups capable of being converted into ion exchange groups, can be the same or different. Specifically, the types of groups capable of being converted into ion exchange groups, as well as the types and contents of each unit, can be the same or different in fluoropolymers (I'-1) and (I'-2).

[0273] Hereinafter, both fluoropolymers (I'-1) and fluoropolymers (I'-2) will be collectively referred to as "fluoropolymers (I')".

[0274] Examples of fluoropolymers (I') include polymers of fluorinated monomers (hereinafter also referred to as "fluorinated monomers (S')") having groups that can be converted to sulfonic acid functional groups (hereinafter also referred to as "fluorinated polymers (S')"), and polymers of fluorinated monomers having groups that can be converted to carboxylic acid functional groups. Fluorinated polymers (S') are preferred, and copolymers of fluorinated olefins and monomers having groups and fluorine atoms that can be converted to sulfonic acid functional groups are more preferred.

[0275] The following is a detailed description of fluoropolymers (S').

[0276] Copolymerization of fluoropolymers (S') can be achieved using known methods such as solution polymerization, suspension polymerization, and emulsion polymerization.

[0277] As a fluorinated olefin, the substances previously exemplified can be listed. From the viewpoint of the manufacturing cost of the monomer, its reactivity with other monomers, and the superior properties of the resulting fluorinated polymer (S), TFE is preferred.

[0278] Fluorinated olefins can be used alone or in combination of two or more.

[0279] As fluorine-containing monomers (S'), compounds that have one or more fluorine atoms in their molecules, have alkene double bonds, and have groups that can be converted into sulfonic acid functional groups can be listed.

[0280] From the viewpoints of monomer manufacturing cost, reactivity with other monomers, and superior properties of the resulting fluorinated polymer (S), the compound shown in formula (2) is preferred as a fluorinated monomer (S').

[0281]

[0282] The definitions of L and n in equation (2) are the same as those in equation (1) above.

[0283] A is a functional group capable of being converted into a sulfonic acid type functional group. Preferably, the functional group capable of being converted into a sulfonic acid type functional group through hydrolysis. Specific examples of functional groups capable of being converted into sulfonic acid type functional groups include -SO2F, -SO2Cl, and -SO2Br. The n A's can be the same or different.

[0284] As the compound represented by formula (2), the compounds represented by formula (2-1), formula (2-2), formula (2-3), and formula (2-4) are preferred.

[0285]

[0286]

[0287]

[0288] R in the formula f1 R f2 R f3 The definitions of r and m are the same as those of R in equations (1-1), (1-2), (1-3), or (1-4) above. f1 R f2 R f3 r and m are the same. In addition, A in the formula is the same as A in the above formula (2).

[0289] As for the compounds shown in formula (2-1) and formula (2-2), the compound shown in formula (2-5) is preferred.

[0290]

[0291] The definitions of x, y, z and Y in the formula are the same as those in the above formula (1-5).

[0292] As specific examples of the compounds shown in formula (2-1), the following compounds can be listed. In the formula, w is an integer from 1 to 8, and v is an integer from 1 to 5.

[0293]

[0294] As specific examples of the compounds shown in formula (2-2), the following compounds can be listed. In the formula, w is an integer from 1 to 8.

[0295]

[0296] As the compound represented by formula (2-3), the compound represented by formula (2-3-1) is preferred.

[0297]

[0298] R in the formula f4 R f5 The definitions of r and A are as described above.

[0299] The following are specific examples of compounds represented by formula (2-3-1).

[0300]

[0301] As the compound shown in formula (2-4), the compound shown in formula (2-4-1) is preferred.

[0302]

[0303] R in the formula f1 R f2 The definitions of A and A are as described above.

[0304] Specific examples of the compounds represented by formula (2-4-1) are listed below.

[0305]

[0306] Fluorinated monomers (S') can be used alone or in combination of two or more.

[0307] In the manufacture of fluoropolymers (S'), other monomers besides fluorinated olefins and fluorinated monomers (S') can also be used. Examples of other monomers previously exemplified can be listed.

[0308] The ion exchange capacity of fluoropolymers (I-1) and (I-2) can be adjusted by changing the content of groups that can be converted into ion exchange groups in fluoropolymers (I'-1) and (I'-2), respectively.

[0309] In the above-described method for manufacturing electrolyte membranes, as a specific example of converting a group in the precursor membrane that can be converted into an ion exchange group into an ion exchange group, a method of performing hydrolysis treatment or acidification treatment on the precursor membrane or a laminate having a precursor membrane can be cited.

[0310] The preferred method is to contact the precursor membrane or a laminate containing the precursor membrane with an alkaline aqueous solution.

[0311] The treatment of precursor membranes described below also includes the treatment of laminates having precursors.

[0312] Specific examples of methods for contacting a precursor membrane with an alkaline aqueous solution include immersing the precursor membrane in an alkaline aqueous solution and spraying an alkaline aqueous solution onto the surface of the precursor membrane.

[0313] The temperature of the alkaline aqueous solution is preferably 30°C or higher, more preferably 40°C or higher, and further preferably 100°C or lower. The contact time between the precursor membrane and the alkaline aqueous solution is preferably 3 minutes or more, more preferably 5 minutes or more, and further preferably 150 minutes or less, and more preferably 50 minutes or less.

[0314] The alkaline aqueous solution preferably contains an alkali metal hydroxide, a water-soluble organic solvent, and water.

[0315] Sodium hydroxide and potassium hydroxide are examples of alkali metal hydroxides.

[0316] In this specification, water-soluble organic solvent refers to an organic solvent that is readily soluble in water. Specifically, it is preferably an organic solvent with a solubility of 0.1 g or more in 1000 mL of water (20°C), and particularly preferably an organic solvent with a solubility of 0.5 g or more. The water-soluble organic solvent preferably includes at least one selected from the group consisting of aprotic organic solvents, alcohols, and amino alcohols, and more preferably includes aprotic organic solvents.

[0317] Non-water-soluble organic solvents can be used alone or in combination of two or more.

[0318] Specific examples of aprotic organic solvents include dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone, with dimethyl sulfoxide being preferred.

[0319] Specific examples of alcohols include methanol, ethanol, isopropanol, butanol, methoxyethoxyethanol, butoxyethanol, butylcarbitol, hexoxyethanol, octanol, 1-methoxy-2-propanol, and ethylene glycol.

[0320] Specific examples of amino alcohols include ethanolamine, N-methylethanolamine, N-ethylethanolamine, 1-amino-2-propanol, 1-amino-3-propanol, 2-aminoethoxyethanol, 2-aminothioethoxyethanol, and 2-amino-2-methyl-1-propanol.

[0321] The concentration of the alkali metal hydroxide in the alkaline aqueous solution is preferably 1% by mass or more, more preferably 3% by mass or more, and preferably 60% by mass or less, more preferably 55% by mass or less.

[0322] The content of water-soluble organic solvent in the alkaline aqueous solution is preferably 1% by mass or more, more preferably 3% by mass or more, and preferably 60% by mass or less, more preferably 55% by mass or less.

[0323] The concentration of water in the alkaline aqueous solution is preferably 39-80% by mass.

[0324] Alternatively, the alkaline aqueous solution can be removed after the precursor membrane has been in contact with it. One method for removing the alkaline aqueous solution is, for example, washing the precursor membrane with water after it has been in contact with the alkaline aqueous solution.

[0325] After the precursor membrane is in contact with an alkaline aqueous solution, the resulting membrane can be in contact with an acidic aqueous solution, thereby converting the ion exchange groups to the acidic form.

[0326] Specific examples of methods for contacting the precursor membrane with an acidic aqueous solution include immersing the precursor membrane in an acidic aqueous solution and spraying an acidic aqueous solution onto the surface of the precursor membrane.

[0327] The acidic aqueous solution preferably contains an acidic component and water.

[0328] Specific examples of acidic components include hydrochloric acid and sulfuric acid.

[0329] [Membrane electrode assembly]

[0330] The membrane electrode assembly disclosed herein includes: the electrolyte membrane, a cathode catalyst layer disposed on one side of the electrolyte membrane, and an anode catalyst layer disposed on the other side of the electrolyte membrane.

[0331] When applying an electrolyte membrane to a water electrolysis device, from the viewpoint of further suppressing hydrogen permeation, it is preferable to position surface A of the first layer of the electrolyte membrane on the anode side. In this case, from the viewpoint of achieving even better results, the catalyst contained in the catalyst layer of the anode preferably contains iridium oxide.

[0332] Figure 3 This is a cross-sectional view schematically illustrating an example of a membrane electrode assembly of the present disclosure. Figure 3 The membrane electrode assembly 30 shown includes: an anode 32 having a catalyst layer 36 and a gas diffusion layer 38; a cathode 34 having a catalyst layer 36 and a gas diffusion layer 38; and an electrolyte membrane 10 disposed between the anode 32 and the cathode 34 in contact with the catalyst layer 36. In the electrolyte membrane 10, a first layer 11 and a second layer 12 are sequentially disposed from the anode 32 side to the cathode 34 side, and a reinforcement 13 is disposed on surface A side.

[0333] exist Figure 3 The example shows a case where the electrolyte membrane 10 has a two-layer structure, but the electrolyte membrane of the membrane electrode assembly can also have a structure with three or more layers.

[0334] <Anode and Cathode>

[0335] Both the anode and cathode have catalyst layers. Figure 3 In the example, the anode 32 and the cathode 34 have a catalyst layer 36 and a gas diffusion layer 38, respectively.

[0336] As a specific example of a catalyst layer, a layer comprising a catalyst and a polymer having ion-exchange groups can be cited.

[0337] Specific examples of catalysts include supported catalysts on a carbon support containing platinum, platinum alloys, or platinum with a core-shell structure; iridium oxide catalysts; composite oxide catalysts containing iridium and other metal elements; alloys containing iridium oxide; and catalysts containing iridium oxide with a core-shell structure. Carbon black powder can be cited as a carbon support.

[0338] As a polymer having ion exchange groups, fluoropolymers having ion exchange groups can be listed, and fluoropolymers (I-1) or (I-2) described above can be used, for example.

[0339] per 1cm 2 The preferred mass of the catalyst metal in the catalyst layer is 0.05 mg / cm³. 2 More preferably, greater than 0.05 mg / cm³ 2 More preferably 0.2 mg / cm 2 In addition, 4 mg / cm³ is preferred. 2 The following is more preferably 2 mg / cm³ 2 The following is further preferred: 1 mg / cm³ 2 the following.

[0340] The mass ratio of the catalyst to the polymer with ion exchange groups in the catalyst layer (mass of catalyst / mass of polymer with ion exchange groups) is preferably 2 to 6.

[0341] From the perspective of improving the dispersibility of the catalyst and inhibiting aggregation, the catalyst layer preferably contains a thickener.

[0342] Specific examples of thickeners include urethane-based thickeners, polyacrylic acid-based thickeners, polyamide-based thickeners, cellulose-based thickeners, and clay mineral thickeners such as bentonite. Additionally, ZEORORA (registered trademark) H (manufactured by ZEON Japan) and others can also be used as thickeners.

[0343] When the catalyst layer contains a thickener, the content of the thickener relative to the total mass of the coating liquid for forming the catalyst layer (described later) is preferably 2% by mass or more, more preferably 3% by mass or more, and preferably 7% by mass or less, more preferably 6% by mass or less.

[0344] The gas diffusion layer functions to rapidly diffuse the gas generated by the catalyst layer outwards and also acts as a current collector. Specific examples of gas diffusion layers include carbon paper, carbon cloth, carbon felt, sintered titanium dioxide fibers, and sintered titanium dioxide particles. Since the anode side is at a high potential and carbon materials are oxidized when used, sintered titanium dioxide fibers or sintered titanium dioxide particles are preferred. The titanium dioxide sintered body can be coated with platinum or similar materials as needed.

[0345] The gas diffusion layer of the cathode can also be treated with PTFE or similar materials to make it water-repellent.

[0346] Figure 3 The membrane electrode assembly has a gas diffusion layer 38, but the gas diffusion layer is an arbitrary component and may not be included in the membrane electrode assembly.

[0347] The film thickness of the anode and cathode is preferably 5 μm or more, and more preferably 100 μm or less, even more preferably 50 μm or less, further preferably 30 μm or less, and particularly preferably 15 μm or less.

[0348] Regarding the film thickness of the anode and cathode, the measurement is obtained by measuring the cross-section cut towards the film thickness direction of the membrane electrode assembly using a laser microscope, and is the arithmetic mean of any 20 points.

[0349] <Manufacturing Method of Membrane Electrode Assembly>

[0350] Methods for manufacturing membrane electrode assemblies include forming a cathode catalyst layer on the surface B side of the electrolyte membrane and forming an anode catalyst layer on the surface A side of the electrolyte membrane.

[0351] As an example of a method for manufacturing a membrane electrode assembly, the following method can be cited: using a laminate having an anode catalyst layer and a release substrate (e.g., an ETFE sheet) and a laminate having a cathode catalyst layer and a release substrate (e.g., an ETFE sheet), after bonding the catalyst layer to both sides of the electrolyte membrane, the release substrate is peeled off.

[0352] The aforementioned laminate may have a gas diffusion layer between the catalyst layer and the release substrate. In this case, a gas diffusion layer can be formed on the side of the catalyst layer opposite to the electrolyte membrane.

[0353] It should be noted that methods for manufacturing the catalyst layer include: applying a catalyst layer forming coating liquid to a specified location (e.g., the surface of a release substrate) and drying it as needed. The catalyst layer forming coating liquid is a liquid in which a polymer having ion exchange groups and a catalyst are dispersed in a dispersion medium.

[0354] <Application>

[0355] The membrane electrode assembly disclosed herein is suitable for use in solid polymer water electrolysis devices.

[0356] [Water Electrolysis Device]

[0357] The water electrolysis apparatus disclosed herein includes: the membrane electrode assembly described above, a water supply unit for supplying water to the anode catalyst layer side, and a power supply unit electrically connected to the anode catalyst layer side and the cathode catalyst layer side.

[0358] In the water electrolysis apparatus of this disclosure, when a DC voltage is applied by the power supply unit while water is supplied to the anode catalyst layer side by the water supply unit, water decomposes to produce oxygen and protons on the anode catalyst layer side. Additionally, on the cathode catalyst layer side, protons that have moved to the cathode catalyst layer side via the electrolyte membrane gain electrons to produce hydrogen.

[0359] In addition to the components described above, the water electrolysis apparatus disclosed herein may have the same configuration as known water electrolysis apparatuses (e.g., an oxygen recovery component for recovering generated oxygen, and a hydrogen recovery component for recovering generated hydrogen).

[0360] Methods for producing hydrogen

[0361] The hydrogen production method disclosed herein is a method of producing hydrogen by electrolyzing water (electrolyte) using the aforementioned water electrolysis apparatus. It can be considered that, since the water electrolysis apparatus of this disclosure is used, hydrogen can be produced efficiently.

[0362] Example

[0363] The present invention will now be described in detail with examples. Examples 1 to 7 are exemplary embodiments, and Examples 8 to 10 are comparative examples. However, the present invention is not limited to these examples.

[0364] [Measurement]

[0365] The physical properties related to the electrolyte membrane in each example were determined using the following methods. The results of each determination are shown in the table below.

[0366] <Ion exchange capacity of various fluoropolymers>

[0367] The fluoropolymer was placed in a glove box purged with dry nitrogen for 24 hours, and its dry mass was determined. Subsequently, the fluoropolymer was immersed in a 2 mol / L sodium chloride aqueous solution at 60°C for 1 hour. After rinsing with ultrapure water, the fluoropolymer was removed, and the liquid containing the fluoropolymer was titrated with a 0.1 mol / L sodium hydroxide aqueous solution. The ion exchange capacity (mcq / g) of the fluoropolymer used in the manufacture of the electrolyte membrane in each example was then determined.

[0368] <Thickness of electrolyte membrane, first layer and second layer>

[0369] The thicknesses T1 of the first layer, T2 of the second layer, and the total thickness T1+T2 of the first and second layers were determined by observing a magnified image of the cross-section of the electrolyte membrane along the thickness direction under the above method at a temperature of 23°C and a relative humidity of 50%RH.

[0370] <Mass containing platinum and cerium oxide>

[0371] The mass of platinum-containing material and cerium oxide contained in the first layer, and the mass of platinum-containing material and cerium oxide contained in the second layer, were measured by observing magnified images of the cross-section of the electrolyte membrane along the thickness direction using an energy-dispersive X-ray analyzer (product name "QUANTAX FlatQUAD", manufactured by Bruker) according to the above method.

[0372] The units for the mass of platinum-containing materials and cerium oxide mentioned above are per 1 cm of the first or second layer. 3 mg (mg / cm) 2 ).

[0373] [evaluate]

[0374] For the electrolyte membranes or membrane electrode assemblies manufactured in each example, the following items were evaluated. The evaluation results are shown in the table below.

[0375] <Damage Generation in Catalyst Layer>

[0376] The catalyst layer is formed by coating a catalyst layer forming composition with the following composition onto a surface of the electrolyte membrane obtained in each example using a molding method and then drying it.

[0377] At this point, the electrolyte membrane is cut to 210×297mm, and the coating area is set to 160×247mm with the ends and each side of the electrolyte membrane equally spaced.

[0378] In addition, during the coating and drying of the film, the four corners of the electrolyte membrane are held with a polyimide heat-resistant tape (manufactured by Teraoka Manufacturing Co., Ltd., Kapton (registered trademark) adhesive tape).

[0379] In addition, a catalyst layer is also formed on the surface opposite to the aforementioned surface.

[0380] Observe the surface of the catalyst layer after coating and drying, and visually confirm whether the surface of the catalyst layer has been damaged.

[0381] Based on the observations, the difficulty of causing damage to the catalyst layer surface was evaluated according to the following criteria. Furthermore, in practical applications, evaluation A, B, or C is preferred. The evaluation results regarding the difficulty of causing damage are recorded in the table below. It can be said that the less likely damage is to occur on the catalyst layer surface, the better the performance in suppressing curling in the electrolyte membrane.

[0382] A: In the case where the surface of the catalyst layer in the above-mentioned coating area was not damaged.

[0383] B: Cases where fewer than 3 instances of damage occurred on the surface of the catalyst layer in the aforementioned coating area.

[0384] C: Cases where 3 or more but fewer than 5 damages occur on the surface of the catalyst layer in the above-mentioned coating area.

[0385] D: Cases where more than 5 damages occur on the surface of the catalyst layer in the above-mentioned coating area.

[0386] <Hydrogen concentration in oxygen>

[0387] The membrane electrode assembly obtained in each example was clamped in a sintered body of platinum-plated titanium fiber (manufactured by Bekaert) with a thickness of 0.25 mm and a porosity of 60%, on an electrode with an area of ​​16 cm², using a platinum-plated titanium plate with a straight flow path as a separator. 2 The membrane electrode assembly is assembled in a single cell. The membrane electrode assembly is clamped and secured by applying a pressure of 1.5 MPa to the electrode portion.

[0388] Next, to ensure the electrolyte membrane and the two electrode ionomers are sufficiently hydrated, pure water with a conductivity of less than 1.0 μS / cm, a temperature of 60°C, and atmospheric pressure was supplied to both the anode and cathode sides at a flow rate of 50 mL / min for 8 hours. Then, pure water with a conductivity of less than 1.0 μS / cm and a temperature of 60°C was supplied to the anode side at a flow rate of 50 mL / min, maintaining atmospheric pressure at both the anode and cathode back pressures while simultaneously using a high-current potentiostat / galvanometer HCP-803 (manufactured by BioLogic) to maintain a current current density of 16 A (1 A / cm²). 2 During the 4-hour break-in period, water electrolysis was performed. Then, for this test, the current was measured at 0~32A (current density 0~2A / cm²). 2 Within the range of ), the current is increased in stages with a step size of 2A.

[0389] Then, pure water with a conductivity of less than 1.0 μS / cm, a temperature of 60°C, and atmospheric pressure was supplied to the battery at a rate of 50 mL / min. For back pressure, while maintaining atmospheric pressure at both the anode and cathode, a high-current potentiostat / galvanometer HCP-803 (manufactured by BioLogic) was used at 3.2 A (current density 0.2 A / cm²). 2 The mixture was kept in the atmosphere for 12 hours. After 12 hours, water was separated from the gas discharged from the anode side, and the hydrogen concentration in the gas was measured using a micro GC (Agilent 490). The hydrogen concentration in oxygen (H2 concentration in O2) was evaluated according to the following criteria. The lower the value of the H2 concentration in O2, the better the performance of the electrolyte membrane in inhibiting hydrogen permeation.

[0390] A: Less than 0.03% of the volume.

[0391] B: 0.03% by volume or more and less than 0.05% by volume.

[0392] C: 0.05% by volume or more and less than 0.10% by volume.

[0393] D: 0.10% or more by volume.

[0394] [Example 1]

[0395] <Preparation of precursor membrane A1>

[0396] First, CF2=CF2 is copolymerized with monomer (X) as shown in formula (X) below to obtain fluoropolymer (I'-1) (ion exchange capacity: 1.40 mEq / g dry resin). It should be noted that the ion exchange capacity in parentheses indicates the ion exchange capacity of the fluoropolymer obtained by hydrolyzing fluoropolymer (I'-1) according to the steps described later.

[0397]

[0398] Prepare a compound A1 containing a fluoropolymer (I'-1), platinum black ("TEC90300", manufactured by Tanaka Precious Metals Industry Co., Ltd., a platinum-containing compound) and cerium oxide (manufactured by Fujifilm and Kohden Chemical Co., Ltd., primary particle size: 10~50nm, CeO2).

[0399] On a substrate made of linear low-density polyethylene (LLDPE) film (melting point: 110~120℃), a compound A1 is attached by melt extrusion to obtain a substrate X1 with a precursor film containing a fluoropolymer (I'-1), platinum black and cerium oxide A1 (film thickness: 10μm).

[0400] It should be noted that when preparing compound A1, the amounts of platinum black and cerium oxide added to compound A1 are adjusted so that the mass of platinum-containing substances and cerium oxide contained in the first layer obtained by hydrolyzing the precursor film A1 according to the steps described later is the value shown in the table below.

[0401] <Precursor Membrane B1 Manufacturing>

[0402] First, CF2=CF2 is copolymerized with monomer (X) as shown in the above formula (X) to obtain fluoropolymer (I'-2) (ion exchange capacity: 1.25 mEq / g dry resin). It should be noted that the ion exchange capacity in parentheses indicates the ion exchange capacity of the fluoropolymer obtained by hydrolyzing fluoropolymer (I'-2) according to the steps described later.

[0403] Prepare compound B1 containing the obtained fluoropolymer (I'-2) but free of either platinum black or cerium oxide.

[0404] On a substrate composed of linear low-density polyethylene (LLDPE) film (melting point: 110~120℃), a compound B1 is attached by melt extrusion to obtain a substrate Y1 with a precursor film containing a fluoropolymer (I'-2) B1 (film thickness: 50μm).

[0405] <The Making of Fabric>

[0406] Fabric A1 is produced by plain weaving using 18.6 denier PFA yarn as both warp and weft, at a PFA yarn density of 100 yarns / inch. Fabric A1 has a basis weight of 16.3 g / m². 2 .

[0407] <Manufacturing of Electrolyte Membrane 1>

[0408] The components are fed to the roller press in a manner in which substrate X1 with a precursor film, fabric A1, and substrate Y1 with a precursor film are stacked in sequence. It should be noted that substrate X1 with a precursor film is arranged in such a way that precursor film A1 contacts fabric A1, and substrate Y1 with a precursor film is arranged in such a way that precursor film B1 contacts fabric A1.

[0409] Using a roller press, a precursor laminate 1 is obtained by hot pressing at 150°C and 1.5MPa for 2 minutes, consisting of a precursor film A1, a fabric A1, and a precursor film B1 arranged sequentially and sandwiched between two substrates. After hot pressing, the substrate is peeled off from the precursor laminate 1.

[0410] In a solution of dimethyl sulfoxide / potassium hydroxide / water = 30 / 5.5 / 64.5 (mass ratio), precursor laminate 1 was immersed at 95°C for 30 minutes to hydrolyze the functional groups in each precursor membrane that could be converted to sulfonic acid type functional groups, converting them to K-type sulfonic acid type functional groups, and then washing with water. Then, the resulting membrane was immersed in 1M sulfuric acid to convert the terminal groups from K-type to H-type, and then dried to obtain electrolyte membrane 1 of Example 1 having a first layer, a fabric layer, and a second layer.

[0411] In the obtained electrolyte membrane 1, the second layer does not contain platinum-containing materials, therefore the concentration of platinum-containing materials in the second layer is lower than that in the first layer. Furthermore, the ion exchange capacity of the fluoropolymer (I-1) contained in the first layer is greater than the ion exchange capacity of the fluoropolymer (I-2) contained in the second layer. Moreover, the reinforcement (fabric A1) of the electrolyte membrane 1 is disposed at the interface between the first and second layers, and closer to the surface A side of the first layer than the central position in the thickness direction of the electrolyte membrane 1.

[0412] <Fabrication of Membrane Electrode Connectors>

[0413] CF2=CF2 is copolymerized with the above monomer (X), and the acid-type polymer (ion exchange capacity: 1.10 mEq / g dry resin) prepared by hydrolysis and acid treatment is dispersed in a solvent of water / ethanol = 40 / 60 (mass%) at a solid content concentration of 26.0% to obtain a dispersion (hereinafter also referred to as "dispersion Y").

[0414] Ethanol (18.06 g) and ZEORORA-H (manufactured by ZEON, Japan) (10.58 g) were added to the obtained dispersion Y (33.0 g), and the mixture was stirred at 2200 rpm for 5 minutes using a THINKY Awatori Rentaro rotary mixer. Ethanol (46.44 g) and water (75.75 g) were added to the mixed composition (54.06 g), and then a solution containing 74.8% iridium with a specific surface area of ​​100 m² was further added. 2 / g of iridium oxide catalyst (manufactured by Tanaka Precious Metals Industry Co., Ltd.) (40.0g). The resulting mixture was treated with a planetary bead mill (300 rpm) for 90 minutes to obtain an anode catalyst ink with a solid content concentration of 22% by mass.

[0415] An anode catalyst ink was coated onto an ETFE sheet using a coater, resulting in an iridium concentration of 1.0 mg / cm². 2 The anode catalyst layer was dried at 80°C for 10 minutes and then further heat-treated at 150°C for 15 minutes to obtain the anode catalyst layer transfer body (decal).

[0416] Water (59.4 g) and ethanol (39.6 g) were added to 11 g of a supported catalyst (Tanaka Precious Metals Industry Co., Ltd. "TEC10E50E") with 46% platinum on carbon powder, and the mixture was mixed and pulverized using an ultrasonic homogenizer to obtain a catalyst dispersion.

[0417] A mixture (29.2 g) prepared by pre-mixing and kneading dispersion Y (20.1 g), ethanol (11 g), and ZEORORA-H (manufactured by ZEON, Japan) (6.3 g) was added to the catalyst dispersion. Then, water (3.66 g) and ethanol (7.63 g) were added to the resulting dispersion, and the mixture was stirred for 60 minutes using a coating adjuster to achieve a solid content of 10.0% by mass, thus obtaining the cathode catalyst ink.

[0418] Cathode catalyst ink was coated onto an ETFE sheet using a die-coating machine, dried at 80°C, and then heat-treated at 150°C for 15 minutes to obtain a platinum content of 0.4 mg / cm³. 2 The cathode catalyst layer transfer body.

[0419] The first layer of the electrolyte membrane 1 obtained above is positioned opposite the surface of the anode catalyst transfer body containing the catalyst layer, and the second layer of the electrolyte membrane 1 is positioned opposite the surface of the cathode catalyst transfer body containing the catalyst layer. The membrane is heated and pressed for 10 minutes at a pressing temperature of 150°C and a pressure of 3 MPa to bond the anode catalyst layer, electrolyte membrane 1, and cathode catalyst layer. The temperature is then reduced to 70°C, the pressure is released, and the membrane is removed. The ETFE sheets of the anode catalyst transfer body and the cathode catalyst transfer body are peeled off to obtain an electrode with an area of ​​16 cm². 2 1. Membrane electrode assembly.

[0420] [Example 2]

[0421] Instead of the compound A1 used in the manufacture of the precursor membrane A1, a compound A2 was prepared by adjusting the amount of platinum black added in such a way that the mass of the platinum-containing material contained in the first layer is the value shown in the table below. Otherwise, the electrolyte membrane 2 and the membrane electrode assembly 2 of Example 2 were obtained in the same manner as in Example 1.

[0422] [Example 3]

[0423] <Manufacturing of precursor membranes B31 and B32>

[0424] The same method as that used to manufacture the precursor film B1 in Example 1 was employed to obtain a substrate Y31 having a precursor film B31 containing a fluoropolymer (I'-2) and having a film thickness of 10 μm formed on a substrate, and a substrate Y32 having a precursor film B32 containing a fluoropolymer (I'-2) and having a film thickness of 40 μm formed on a substrate.

[0425] <Manufacturing of Electrolyte Membrane 3>

[0426] The components are fed to a roller press in a sequentially stacked manner, consisting of precursor film Y31, fabric A1, and substrate Y32 with precursor film. It should be noted that substrate Y1 with precursor film is positioned such that precursor film B31 contacts fabric A1, and substrate Y32 with precursor film B32 contacts fabric A1. Next, the roller press is used to hot-press the substrate at 150°C and 1.5 MPa for 2 minutes, resulting in a precursor laminate 3A with precursor film B31, fabric A1, and precursor film B32 sequentially arranged and sandwiched between substrates on both surfaces.

[0427] Next, the substrate in contact with the precursor film B31 is peeled off from the precursor laminate 3A, and the substrate X1 with the precursor film and the precursor laminate 3A are overlapped and fed into a roller press. It should be noted that the substrate X1 with the precursor film and the precursor laminate 3A are arranged in such a way that the precursor film A1 contacts the precursor film B31. Using a roller press, hot pressing is performed at 150°C and 1.5 MPa for 2 minutes to obtain a precursor laminate 3 with the precursor film A1, precursor film B31, fabric A1, and precursor film B32 sequentially arranged, and both surfaces sandwiched by the substrate. After hot pressing, the substrate is peeled off from the precursor laminate 3.

[0428] The electrolyte membrane 3 and membrane electrode assembly 3 of Example 3 are obtained in the same manner as in Example 1, except that the precursor laminate 3 is used instead of the precursor laminate 1.

[0429] [Example 4]

[0430] Using the values ​​shown in the table below for the thickness T1 of the first layer and the mass of platinum-containing material and cerium oxide contained in the first layer, the amounts of platinum black and cerium oxide added to the compound A1 and the amount of compound A1 attached to the substrate were adjusted respectively. Otherwise, the same method as the manufacturing method of the precursor film A1 in Example 1 was used to obtain a substrate X4 with a precursor film containing a fluoropolymer (I'-1) formed on the substrate.

[0431] In addition, the same method as that used to manufacture the precursor film B1 in Example 1 was followed to obtain a substrate Y4 having a precursor film B4 containing a fluoropolymer (I'-2) and having a film thickness of 40 μm formed on the substrate.

[0432] Instead of substrate X1 with a precursor membrane and substrate Y1 with a precursor membrane, substrate X4 with a precursor membrane and substrate Y4 with a precursor membrane are used respectively. Otherwise, the electrolyte membrane 4 and membrane electrode assembly 4 of Example 4 are obtained in the same manner as in Example 1.

[0433] [Example 5]

[0434] CF2=CF2 is copolymerized with monomer (X) as shown in formula (X) below to obtain fluoropolymer (I'-3) (ion exchange capacity: 1.95 mEq / g dry resin). It should be noted that the ion exchange capacity in parentheses indicates the ion exchange capacity of the fluoropolymer obtained by hydrolyzing fluoropolymer (I'-3) according to the steps described later.

[0435] The electrolyte membrane 5 and membrane electrode assembly 5 of Example 5 were obtained in the same manner as in Example 1, except that a fluoropolymer (I'-3) was used instead of a fluoropolymer (I'-1).

[0436] [Example 6]

[0437] Instead of the compound A1 used in the manufacture of the precursor film A1, a compound A2 was prepared by adjusting the amount of platinum black added in such a way that the mass of the platinum-containing material contained in the first layer is the value shown in the table below. Otherwise, the same procedure as in Example 1 was followed to obtain a substrate X6 with a precursor film A6 (film thickness: 10 μm) formed on the substrate.

[0438] Instead of the compound B1 used in the manufacture of the precursor film B1, a compound B6 containing a fluoropolymer (I'-2), platinum black ("TEC90300" manufactured by Tanaka Precious Metals Industry Co., Ltd., platinum-containing compound) and cerium oxide (manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd., primary particle size: less than 10 nm, CeO2) was used. Otherwise, the operation was the same as in Example 1 to obtain a substrate Y6 with a precursor film containing a precursor film B6 (film thickness: 50 μm) containing a fluoropolymer (I'-2), platinum black and cerium oxide.

[0439] It should be noted that when preparing compound B6, the amounts of platinum black and cerium oxide added to compound B6 are adjusted so that the mass of platinum-containing substances and cerium oxide contained in the first layer obtained by hydrolyzing the precursor membrane B6 is the value shown in the table below.

[0440] Instead of substrate X1 with a precursor membrane and substrate Y1 with a precursor membrane, substrate X6 with a precursor membrane and substrate Y6 with a precursor membrane are used respectively. Otherwise, the electrolyte membrane 6 and membrane electrode assembly 6 of Example 6 are obtained in the same manner as in Example 1.

[0441] [Example 7]

[0442] The same method as that used to manufacture the precursor film B1 in Example 1 was followed to obtain a substrate Y7 having a precursor film B7 containing a fluoropolymer (I'-2) and having a film thickness of 80 μm formed on the substrate.

[0443] The electrolyte membrane 7 and the membrane electrode assembly 7 of Example 7 are obtained in the same manner as in Example 1, except that a substrate Y7 with a precursor membrane is used instead of a substrate Y1 with a precursor membrane.

[0444] [Example 8]

[0445] Using a fluoropolymer (I'-2) instead of a fluoropolymer (I'-1), otherwise, a substrate X8 with a precursor film containing a fluoropolymer (I'-2), platinum black and cerium oxide precursor film A8 (film thickness: 10 μm) is obtained on the substrate in the same manner as in Example 1.

[0446] The same method as that used to manufacture the precursor film B1 in Example 1 was employed to obtain a substrate Y81 having a precursor film B81 containing a fluoropolymer (I'-2) and having a film thickness of 20 μm formed on a substrate, and a substrate Y82 having a precursor film B82 containing a fluoropolymer (I'-2) and having a film thickness of 30 μm formed on a substrate.

[0447] Instead of substrate X1 with precursor membrane, substrate Y31 with precursor membrane, and substrate Y32 with precursor membrane, substrate X8 with precursor membrane, substrate Y81 with precursor membrane, and substrate Y82 with precursor membrane are used respectively. Otherwise, the electrolyte membrane 8 and membrane electrode assembly 8 of Example 8 are obtained in the same manner as in Example 3.

[0448] In the obtained electrolyte membrane 8, the ion exchange capacity of the fluoropolymer (I-1) contained in the first layer is equal to the ion exchange capacity of the fluoropolymer (I-2) contained in the second layer. Furthermore, in the electrolyte membrane 8, the reinforcement (woven fabric A1) is disposed at the central position in the thickness direction of the electrolyte membrane 8.

[0449] [Example 9]

[0450] Instead of the substrate X1 with the precursor film, a substrate X8 with a precursor film A8 (film thickness: 10 μm) formed on the substrate was manufactured in Example 8. Otherwise, the same procedure as in Example 1 was followed to obtain the electrolyte membrane 9 and the membrane electrode assembly 9 of Example 9.

[0451] In the obtained electrolyte membrane 9, the ion exchange capacity of the fluorinated polymer (I-1) contained in the first layer is equal to the ion exchange capacity of the fluorinated polymer (I-2) contained in the second layer.

[0452] [Example 10]

[0453] Instead of substrate Y31 and substrate Y32 with precursor membrane, substrate Y81 and substrate Y82 with precursor membrane manufactured in Example 8 are used respectively. Otherwise, the electrolyte membrane 10 and membrane electrode assembly 10 of Example 10 are obtained in the same manner as in Example 3.

[0454] In the obtained electrolyte membrane 10, the reinforcement (fabric A1) is disposed at the central position in the thickness direction of the electrolyte membrane 10.

[0455] [result]

[0456] Table 1 shows the composition of the electrolyte membranes manufactured in each example, as well as the difficulty of generating damage during catalyst layer formation and the evaluation results of hydrogen concentration in oxygen.

[0457] The thickness (in μm) of the electrolyte membrane shown in the "Thickness (μm)" column of the "Electrolyte Membrane" is equal to the sum of the thickness T1 of the first layer and the thickness T2 of the second layer.

[0458] The value shown in the "Distance of Reinforcement from Surface A (μm)" column represents the distance between the reinforcement disposed inside each electrolyte membrane and surface A on the first layer side. When the distance of the reinforcement from surface A is 1 / 2 of the thickness of the electrolyte membrane, it means that the reinforcement is disposed at the center position in the thickness direction of the electrolyte membrane. When the distance of the reinforcement from surface A is less than 1 / 2 of the thickness of the electrolyte membrane, it means that the reinforcement is disposed closer to surface A on the first layer side than the center position in the thickness direction of the electrolyte membrane.

[0459] [Table 1]

[0460]

[0461] As shown in Table 1, it was confirmed that for an electrolyte membrane having a first layer, a second layer, and a reinforcing body, wherein the first layer contains a fluoropolymer (I-1) with ion-exchange groups and a platinum-containing compound, the second layer contains a fluoropolymer (I-2) with ion-exchange groups, and the concentration of the platinum-containing compound in the second layer is lower than that in the first layer, the ion-exchange capacity of the fluoropolymer (I-1) is greater than that of the fluoropolymer (I-2), and the reinforcing body is disposed on surface A, the performance in suppressing curling is excellent, and the performance in suppressing hydrogen permeation is excellent (Examples 1 to 7). In Examples 8 and 9, it can be considered that since the ion-exchange capacities of the fluoropolymer contained in the first layer and the fluoropolymer contained in the second layer are equal, hydrogen permeation cannot be sufficiently reduced. In addition, in Examples 8 and 10, it can be considered that since the reinforcing body is disposed at the central position in the thickness direction of the solid polymer electrolyte membrane rather than at the interface between the first and second layers, the electrolyte membrane is prone to curling.

[0462] It should be noted that the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2023-222220, filed on December 28, 2023, are incorporated herein as a disclosure of the specification of this invention.

[0463] Explanation of reference numerals in the attached figures

[0464] 10, 20 Electrolyte membrane (solid polymer electrolyte membrane)

[0465] 11 First Floor

[0466] 12 Second layer

[0467] 13 Enhancers

[0468] 30 Membrane electrode assembly

[0469] 32 Anode

[0470] 34 Cathode

[0471] 36 Catalyst Layer

[0472] 38 Gas diffusion layer

[0473] Surfaces A and B

[0474] C Central surface

[0475] D interface

[0476] Thicknesses T1 and T2

Claims

1. A solid polymer electrolyte membrane, comprising: The first layer comprises a first fluoropolymer having ion-exchange groups and a platinum-containing compound; and The second layer comprises a second fluoropolymer having ion-exchange groups. The concentration of platinum in the second layer is lower than the concentration of platinum in the first layer. The ion exchange capacity of the first fluoropolymer is greater than that of the second fluoropolymer, and The solid polymer electrolyte membrane also has a reinforcement disposed closer to the surface side of the first layer side of the solid polymer electrolyte membrane than the central position of the solid polymer electrolyte membrane in the thickness direction.

2. The solid polymer electrolyte membrane according to claim 1, wherein, The solid polymer electrolyte membrane also contains cerium oxide.

3. The solid polymer electrolyte membrane according to claim 1, wherein, The second layer does not contain the platinum-containing material.

4. The solid polymer electrolyte membrane according to claim 1, wherein, The reinforcement is fabric.

5. The solid polymer electrolyte membrane according to claim 4, wherein, The fabric is made of a material selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyether ether ketone and polyphenylene sulfide.

6. The solid polymer electrolyte membrane according to claim 1, wherein, The thickness of the first layer is thinner than the thickness of the second layer.

7. The solid polymer electrolyte membrane according to claim 1, wherein, The ratio of the thickness of the first layer to the total thickness of the first layer and the second layer is less than 0.

50.

8. The solid polymer electrolyte membrane according to claim 1, wherein, The combined thickness of the first layer and the second layer is 30~400μm.

9. The solid polymer electrolyte membrane according to claim 1, wherein, The absolute value of the difference between the ion exchange capacity of the first fluoropolymer and the ion exchange capacity of the second fluoropolymer is 0.10~1.40 milliequivalents / gram of dry resin.

10. The solid polymer electrolyte membrane according to claim 1, wherein, The ion exchange groups of the first fluoropolymer are sulfonic acid type functional groups. The ion exchange group of the second fluoropolymer is a sulfonic acid type functional group.

11. A membrane electrode assembly comprising: The solid polymer electrolyte membrane according to any one of claims 1 to 10 The cathode catalyst layer disposed on the surface side of the second layer of the solid polymer electrolyte membrane, and An anode catalyst layer disposed on the surface side of the first layer of the solid polymer electrolyte membrane.

12. A water electrolysis apparatus, comprising: The membrane electrode assembly as described in claim 11; The power supply unit is connected to the cathode catalyst layer side and the anode catalyst layer side of the membrane electrode assembly; and The water supply unit supplies water to the anode catalyst layer side.

13. A method for producing hydrogen, wherein hydrogen is produced by electrolyzing water using the water electrolysis apparatus of claim 12.

14. A method for manufacturing a membrane electrode assembly, the membrane electrode assembly comprising: a solid polymer electrolyte membrane according to any one of claims 1 to 10, a cathode catalyst layer, and an anode catalyst layer. In the manufacturing method, the cathode catalyst layer is formed on the surface side of the second layer of the solid polymer electrolyte membrane, and the anode catalyst layer is formed on the surface side of the first layer of the solid polymer electrolyte membrane.

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