Electrolyte membrane, electrolyte membrane with catalyst layer, transfer sheet used for producing same, membrane-electrode assembly, water electrolysis device, and method for manufacturing electrolyte membrane with catalyst layer

Abstract

The main objective of the present invention is to provide an electrolyte membrane having good bondability with a catalyst layer, said electrolyte membrane comprising a polymer electrolyte-containing layer (A) and a layer (B) disposed on at least one surface of the layer (A) and being characterized in that a particle concentration (Y1) of the layer (B) in an interface region with the layer (A), as defined below, is higher than a particle concentration (Y2) of the layer (B) in an opposite interface region from the layer (A), as defined below. The particle concentration (Y1) and the particle concentration (Y2) each represent a mass ratio of particles present in the relevant interface region to the total mass of solid content present in the interface region.

Description

Electrolyte membrane, catalyst-coated electrolyte membrane and transfer sheet used in its production, membrane electrode assembly, water electrolysis device, and method for producing catalyst-coated electrolyte membrane

[0001] The present invention relates to an electrolyte membrane, a catalyst-coated electrolyte membrane and a transfer sheet used in the production thereof, a membrane electrode assembly, a water electrolysis device, and a method for producing a catalyst-coated electrolyte membrane.

[0002] In recent years, hydrogen energy has been attracting attention as a next-generation energy storage and transportation method. When used as fuel for fuel cells, hydrogen can theoretically be converted into electricity with higher energy efficiency than power generation using heat engines, and because it emits relatively few harmful substances, it has the potential to be a highly efficient, clean energy source.

[0003] One method of producing hydrogen is water electrolysis. If surplus electricity generated by renewable energy is used to electrolyze water, it is possible to convert electricity into hydrogen energy without emitting carbon dioxide. Furthermore, depending on the storage method, hydrogen can be transported by tank truck or tanker and supplied when and where it is needed, making water electrolysis a highly promising tool for storing electricity.

[0004] Methods for producing hydrogen through water electrolysis include alkaline water electrolysis and polymer electrolyte membrane (PEM) water electrolysis. PEM water electrolysis has the advantage of being able to operate at high current densities and flexibly adapt to fluctuations in renewable energy output.

[0005] A PEM water electrolysis device is typically constructed with a cell unit, in which a membrane electrode assembly (MEA) is sandwiched between separators. The MEA is constructed of a catalyst-coated membrane (CCM) in which catalyst layers are formed on both sides of a polymer electrolyte membrane, one of which is an anode catalyst layer and the other is a cathode catalyst layer. Water is supplied to the anode catalyst layer of a PEM water electrolysis cell to which a current is applied, and protons are generated by an electrochemical reaction. Subsequently, the protons diffuse through the polymer electrolyte membrane from the anode electrode layer side to the cathode electrode layer side, and hydrogen is produced from the protons by an electrochemical reaction in the cathode layer.

[0006] In a PEM-type water electrolysis device, the adhesiveness at the interface between the catalyst layer and the polymer electrolyte membrane may deteriorate during water electrolysis operation. Therefore, it has been proposed to provide an adhesive layer between the polymer electrolyte membrane and the catalyst layer to improve the adhesiveness between the polymer electrolyte membrane and the catalyst layer (see, for example, Patent Documents 1 and 2).

[0007] JP-T-2008-512844A JP-A-2011-187436A

[0008] However, the conventional techniques disclosed in the above-mentioned patent documents have not been able to sufficiently improve the bonding strength between the polymer electrolyte membrane and the catalyst layer. Insufficient bonding strength between the electrolyte membrane and the catalyst layer may result in, for example, peeling between the electrolyte membrane and the catalyst layer or a decrease in adhesion between the electrolyte membrane and the catalyst layer during operation of the water electrolysis device, resulting in a decrease in proton conductivity and a decrease in water electrolysis performance.

[0009] In view of the above background, an object of the present invention is to provide an electrolyte membrane that has good bonding to a catalyst layer.

[0010] In order to achieve the above object, the electrolyte membrane of the present invention has the following configuration. That is, the electrolyte membrane includes an (A) layer containing a polymer electrolyte and a (B) layer on at least one side of the (A) layer, wherein a particle concentration (Y1), defined below, in an interface region of the (B) layer with the (A) layer is higher than a particle concentration (Y2), defined below, in an interface region of the (B) layer opposite the (A) layer. The particle concentrations (Y1) and (Y2) are ratios of the mass of particles present in the interface region to the total mass of solids present in the interface region. That is, the particle concentration (Y1) is the ratio of the mass of particles present in the interface region of the (B) layer with the (A) layer to the total mass of solids present in the interface region, and the particle concentration (Y2) is the ratio of the mass of particles present in the interface region of the (B) layer opposite the (A) layer to the total mass of solids present in the interface region.

[0011] According to the present invention, it is possible to provide an electrolyte membrane that has excellent bonding to a catalyst layer.

[0012] Fig. 1 is a cross-sectional view of an electrolyte membrane according to embodiment 1 of the present invention; Fig. 2 is a cross-sectional view of an electrolyte membrane with a catalyst layer using the electrolyte membrane according to embodiment 1 of the present invention; Fig. 3 is a cross-sectional view of an electrolyte membrane according to embodiment 2 of the present invention; Fig. 4 is a cross-sectional view of an electrolyte membrane with a catalyst layer using the electrolyte membrane according to embodiment 2 of the present invention;

[0013] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following embodiments and can be modified in various ways depending on the purpose and application. Furthermore, the description of the specific embodiments shown in the drawings can also be understood as a description of the present invention as a general concept.

[0014] An electrolyte membrane according to an embodiment of the present invention is an electrolyte membrane comprising an (A) layer containing a polymer electrolyte and a (B) layer on at least one side of the (A) layer, and it is important that the particle concentration (Y1) in the interface region of the (B) layer with the (A) layer is higher than the particle concentration (Y2) in the interface region of the (B) layer opposite the (A) layer, where the particle concentrations (Y1) and (Y2) are the ratios of the particle mass present in the interface region to the total solid mass present in the interface region.

[0015] When the (B) layer contains multiple types of particles, the particle concentrations (Y1) and (Y2) are calculated as the ratio of the mass of all particles present in the interface region to the mass of all solids present in the interface region.

[0016] In the present invention, the interfacial region refers to a region in the (B) layer that is 10% thick from each interface between the (B) layer and another adjacent layer with respect to the overall thickness of the (B) layer. The relative relationship (magnitude relationship) between the particle concentration (Y1) and the particle concentration (Y2) can be determined by observing a cross section of the electrolyte membrane with a scanning transmission electron microscope (STEM) or a scanning electron microscope (SEM), or by combining cross-sectional observation with STEM or SEM with elemental analysis (elemental analysis by energy dispersive X-ray spectroscopy (EDX) or electron beam microanalyzer (EMPA)).

[0017] Specifically, first, the presence or absence of particles in the two interface regions of the (B) layer is observed using a TEM or SEM. If particles are found to be present in both interface regions, the interface regions are subjected to elemental analysis using EDX or EMPA.

[0018] In the above elemental analysis, when the elements constituting the particles overlap with the elements constituting components other than the particles (e.g., polymers) contained in Layer (B), for example, when the particles are carbon black and the polymer is a perfluorocarbon sulfonic acid polymer, "C" is selected as the particle element and an element other than "C," such as "F" or "S," is selected as the polymer element for elemental analysis. Then, by calculating and comparing the ratios of C to F or S (C / F or C / S) in the two interface regions, the relative relationship between Y1 and Y2 and the ratio of Y1 to Y2 (Y2 / Y1) can be determined. Details are described in the Examples.

[0019] First Embodiment FIG. 1 is a schematic cross-sectional view showing an example of an electrolyte membrane according to a first embodiment of the present invention.

[0020] In the first embodiment, the electrolyte membrane 1 has a configuration in which a (B) layer 20 is laminated on one surface of an (A) layer 10. The (B) layer 20 has an interface region 21 on the (A) layer side and an interface region 22 on the opposite side from the (A) layer. The (B) layer 20 contains particles (not shown), and the particle concentration in the interface region 21 is a particle concentration (Y1), and the particle concentration in the interface region 22 is a particle concentration (Y2). FIG. 2 is a cross-sectional schematic diagram showing an example of a catalyst-coated electrolyte membrane in which catalyst layers are laminated on both surfaces of the electrolyte membrane of the first embodiment. Hereinafter, the catalyst-coated electrolyte membrane may be abbreviated as "CCM."

[0021] The CCM 100 has a configuration in which catalyst layers 30 and 40 are laminated on both sides of an electrolyte membrane 1. Here, the catalyst layers 30 and 40 are an anode catalyst layer and a cathode catalyst layer, respectively, in any order.

[0022] The electrolyte membrane according to the first embodiment is characterized in that the particle concentration (Y1) in the interface region 21 of the (B) layer 20 with the (A) layer 10 is higher than the particle concentration (Y2) in the interface region 22 of the (B) layer 20 on the opposite side from the (A) layer 10. This improves the bonding between the electrolyte membrane 1 and the catalyst layer 30. The mechanism behind this is not clear, but is presumed to be as follows.

[0023] The particle concentration on the outermost surface of the layer affects the surface roughness (irregularities), with a high particle concentration resulting in a larger surface roughness (irregularities), and a low particle concentration resulting in a smaller surface roughness (irregularities) (higher smoothness).The irregularities formed on the outermost surface of the layer are thought to function as anchors at the bonding interface with other layers.

[0024] Generally, the (A) layer 10 containing a polymer electrolyte has a relatively smooth surface, while the catalyst layers 30 and 40 contain catalyst particles and therefore have an uneven surface. Therefore, by arranging the interface region 21 (particle concentration (Y1)) of the (B) layer 20, where the particle concentration is relatively high, facing the (A) layer 10 side, which has a smooth surface, and the interface region 22 (particle concentration (Y2)) of the (B) layer 20, where the particle concentration is relatively low, facing the catalyst layer 30 side, which has an uneven surface, an anchor effect is exerted at both interfaces. It is believed that this improves the bonding strength between the (A) layer 10 and the (B) layer 20 and the bonding strength between the (B) layer 20 and the catalyst layer 30.

[0025] The present invention is particularly effective when the polymer electrolyte contained in the (A) layer 10 and the polymer electrolyte contained in the catalyst layer 30 are different from each other. This is because when the (A) layer 10 and the catalyst layer 30 contain different types of polymer electrolytes, interlayer bonding tends to deteriorate.

[0026] Here, examples of the polymer electrolytes being different from each other include a case where one is a hydrocarbon-based polymer electrolyte and the other is a fluorine-based polymer electrolyte. Specific examples include a case where the (A) layer 10 contains a hydrocarbon-based polymer electrolyte and the catalyst layer 30 contains a fluorine-based polymer electrolyte (Configuration 1), and a case where the (A) layer 10 contains a fluorine-based polymer electrolyte and the catalyst layer 30 contains a hydrocarbon-based polymer electrolyte (Configuration 2). Configuration 1 is preferred from the viewpoint of water electrolysis performance.

[0027] When the polymer electrolyte contained in the (A) layer 10 and the polymer electrolyte contained in the catalyst layer 30 are different from each other, as in the above-described embodiments 1 and 2, it is preferable that the (B) layer 20 contain the same type of polymer as the catalyst layer 30 from the viewpoint of bonding properties. Here, "the polymers are the same type" refers to polymers having the same main skeleton, such as fluorine-based polymers or hydrocarbon-based polymers, regardless of whether they are ionic or nonionic. For example, an ionic fluorine-based polymer (fluorine-based polymer electrolyte) and a nonionic fluorine-based polymer are the same type of polymer, and similarly, an ionic hydrocarbon-based polymer (hydrocarbon-based polymer electrolyte) and a nonionic hydrocarbon-based polymer are the same type of polymer. From the viewpoint of proton conductivity, it is more preferable that the (B) layer 20 contain the same type of polymer electrolyte as the polymer electrolyte contained in the catalyst layer 30. Details of the polymer contained in the (B) layer 20 will be described later.

[0028] A particularly preferred combination of materials contained in the (A) layer, catalyst layer, and (B) layer is a configuration in which the (A) layer contains a hydrocarbon-based polymer electrolyte, the catalyst layer contains a fluorine-based polymer electrolyte, and the (B) layer contains a fluorine-based polymer.

[0029] From the viewpoint of improving the bonding strength between the electrolyte membrane 1 and the catalyst layer 30, the ratio (Y2 / Y1) of the particle concentration (Y1) to the particle concentration (Y2) is preferably 0.95 or less, more preferably 0.75 or less, and particularly preferably 0.60 or less. The lower limit of the ratio (Y2 / Y1) is 0.00.

[0030] The particle concentration (Y1) is preferably 45% by mass or more, more preferably 50% by mass or more, and particularly preferably 55% by mass or more, from the viewpoint of improving the bonding strength between the (A) layer 10 and the (B) layer 20. Furthermore, from the viewpoint of the film formability of the coating film, the particle concentration (Y1) is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

[0031] From the viewpoint of improving the bonding strength between the (B) layer 20 and the catalyst layer 30, the particle concentration (Y2) is preferably less than 45 mass%, more preferably less than 40 mass%, and particularly preferably less than 35 mass%, within the range satisfying (Y2) > (Y1). The lower limit is 0%.

[0032] From the viewpoint of the bondability between the (A) layer 10 and the (B) layer 20 and the bondability between the (B) layer 20 and the catalyst layer 30, it is preferable that the particle concentration (Y1) is 45 mass% or more and the particle concentration (Y2) is less than 45 mass%.

[0033] The particle concentration (Y2) is preferably adjusted according to the mass ratio (C / I) of the content (C) of catalyst particles (including catalyst-supported particles) to the content (I) of polymer electrolyte contained in the catalyst layer 30. Generally, the surface roughness (unevenness) of a catalyst layer with a high C / I tends to be large, while the surface roughness (unevenness) of a catalyst layer with a low C / I tends to be small. To improve the anchoring effect at the bonding surface, a low particle concentration (Y2) is preferable for a catalyst layer with a relatively high C / I, while a high particle concentration (Y2) is preferable for a catalyst layer with a relatively low C / I. For example, when the mass ratio (C / I) is 4.0 or greater, the particle concentration (Y2) is more preferably less than 45% by mass, even more preferably less than 38%, and particularly preferably less than 35%. On the other hand, when the mass ratio (C / I) is less than 4.0, the particle concentration (Y2) may be less than 45% by mass.

[0034] When the (B) layer 20 is disposed on only one side of the (A) layer 10, it may be disposed only on the anode catalyst layer side or only on the cathode catalyst layer side. When the electrolyte membrane according to the first embodiment is applied to a water electrolysis device, disposing the (B) layer 20 on the anode catalyst layer side (catalyst layer 30 as the anode catalyst layer) is expected to not only improve the bonding strength but also suppress electrochemical oxidative degradation of the (A) layer. Disposing the (B) layer 20 on the cathode catalyst layer side (catalyst layer 30 as the cathode catalyst layer) is expected to not only improve the bonding strength but also protect the (A) layer from peroxide radicals by-produced at the cathode.

[0035] In a water electrolysis device, the anode is in a high-potential environment, and the (B) layer on the anode catalyst layer side preferably has a barrier function to suppress electrochemical oxidative degradation of the (A) layer 10. From this perspective, when the catalyst layer 30 is an anode catalyst layer, the particle concentration (Y2) of the (B) layer 20 on the anode catalyst layer side is preferably relatively low. Specifically, the particle concentration (Y2) is preferably less than 45 mass%, more preferably less than 38 mass%, even more preferably less than 35 mass%, and most preferably 0 mass%.

[0036] On the other hand, when the catalyst layer 30 is a cathode catalyst layer, the particle concentration (Y2) of the (B) layer 20 on the cathode catalyst layer side is preferably relatively high from the viewpoint of suppressing interfacial peeling between the catalyst layer and the (B) layer due to hydrogen generated at the cathode (ensuring an escape route for hydrogen). Specifically, the particle concentration (Y2) is more preferably 30 mass% or more, and even more preferably 35 mass% or more. Furthermore, the upper limit of the particle concentration (Y2) is preferably less than 45 mass%.

[0037] Furthermore, in a water electrolysis device, the content ratio of catalyst particles to polymer electrolyte in the anode catalyst layer is set relatively high, making it difficult to achieve good bonding between the anode catalyst layer and the (A) layer. Therefore, it is more beneficial to place the (B) layer on the anode catalyst layer side in terms of improving bonding. Therefore, it is more preferable that the catalyst layer 30 is the anode catalyst layer.

[0038] Furthermore, in water electrolysis devices, the cathode catalyst layer generally has a relatively low catalyst particle content relative to the polymer electrolyte, so the strength level of the bond between the cathode catalyst layer and the (A) layer is not as low as that on the anode side. Therefore, the bond can also be improved by replacing the (B) layer with a single layer having a particle concentration of 30 mass% to 80 mass% on the cathode catalyst layer side. Hereinafter, the single layer used on the cathode catalyst layer side in place of the (B) layer will be referred to as the "(C) layer." In this case, the electrolyte membrane 1 in the first embodiment has a configuration in which the (B) layer, the (A) layer, and the (C) layer (not shown) are stacked in this order. Specifically, in FIG. 2 , the catalyst layer 30 serves as the anode catalyst layer, and the catalyst layer 40 serves as the cathode catalyst layer. The (C) layer (not shown) is disposed between the catalyst layer 40, which is the cathode catalyst layer, and the (A) layer 10.

[0039] The particle concentration of this layer (C) is more preferably 40% by mass or more and 75% by mass or less, and particularly preferably 45% by mass or more and 70% by mass or less. Carbon particles are preferred as the particles contained in layer (C). The carbon particles contained in layer (C) are expected to have the effect of decomposing or capturing peroxide radicals by-produced at the cathode. This is expected to protect layer (A) from peroxide radicals.

[0040] 3 is a cross-sectional schematic diagram showing an example of an electrolyte membrane according to a second embodiment of the present invention. In the second embodiment, the electrolyte membrane 2 has a configuration in which a (B) layer 20a is laminated on one surface of an (A) layer 10, and another (B) layer 20b is laminated on the opposite surface.

[0041] The (B) layer 20a has an interface region 21a on the (A) layer 10 side and an interface region 22a on the opposite side from the (A) layer 10. The (B) layer 20b has an interface region 21b on the (A) layer 10 side and an interface region 22b on the opposite side from the (A) layer 10. The (B) layers 20a and 20b contain particles (not shown), and the particle concentrations in the interface regions 21a and 21b are particle concentrations (Y1), and the particle concentrations in the interface regions 22a and 22b are particle concentrations (Y2). For the sake of distinction, let us denote the particle concentrations in the interface regions 21a and 21b as (Y1-a) and (Y1-b), respectively, and the particle concentrations in the interface regions 22a and 22b as (Y2-a) and (Y2-b), respectively. (Y1-a) and (Y1-b) may be the same as or different from each other, and (Y2-a) and (Y2-b) may be the same as or different from each other. In this case, the particle concentration (Y1) being higher than the particle concentration (Y2) means that (Y1-a)>(Y2-a) and / or (Y1-b)>(Y2-b). Fig. 4 is a cross-sectional schematic diagram showing an example of a catalyst-coated electrolyte membrane (CCM) in which catalyst layers are laminated on both sides of the electrolyte membrane of the second embodiment.

[0042] The CCM 200 has a configuration in which an anode catalyst layer 50 is laminated on the (B) layer 20a side of the electrolyte membrane 2, and a cathode catalyst layer 60 is laminated on the (B) layer 20b side.

[0043] In the second embodiment, the relationship (Y1)>(Y2) is preferably satisfied at least in the (B) layer 20a on the anode catalyst layer 50 side, and more preferably in both the (B) layer 20a on the anode catalyst layer 50 side and the (B) layer 20b on the cathode catalyst layer 60 side. That is, it is preferable that (Y1-a)>(Y2-a), and it is more preferable that (Y1-a)>(Y2-a) and (Y1-b)>(Y2-b).

[0044] The particle concentration (Y2-a) in the (B) layer 20a on the anode catalyst layer 50 side is preferably smaller than the particle concentration (Y2-b) in the (B) layer 20b on the cathode catalyst layer 60 side. It is particularly preferable that the particle concentration (Y2-a) in the (B) layer 20a adjacent to the anode catalyst layer 50 is less than 35%, and that the particle concentration (Y2-b) in the (B) layer 20b adjacent to the cathode catalyst layer 60 is less than 45%.

[0045] Below, matters common to the embodiments included in the present invention will be described in detail.

[0046] [Layer (A)] The layer (A) contains a polymer electrolyte. Examples of the polymer electrolyte include a fluorine-based polymer electrolyte and a hydrocarbon-based polymer electrolyte. From the viewpoint of water electrolysis performance, a hydrocarbon-based polymer electrolyte is preferred.

[0047] Here, the fluoropolymer electrolyte is a fluoropolymer having ionic groups. The fluoropolymer refers to a polymer in which most or all of the hydrogen atoms in the alkyl and / or alkylene groups in the polymer have been substituted with fluorine atoms. Representative examples of the fluoropolymer electrolyte include commercially available products such as Nafion (registered trademark) (manufactured by DuPont), Flemion (registered trademark) (manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark) (manufactured by Asahi Kasei Corporation).

[0048] A hydrocarbon-based polymer electrolyte is a hydrocarbon-based polymer having an ionic group. The hydrocarbon-based polymer is preferably an aromatic hydrocarbon-based polymer having an aromatic ring in the main chain. Here, the aromatic ring may include not only a hydrocarbon-based aromatic ring but also a heterocycle. Furthermore, the polymer may also include some aliphatic units in addition to the aromatic ring units.

[0049] Specific examples of aromatic hydrocarbon polymers include polymers having a structure selected from polysulfone, polyethersulfone, polyphenylene oxide, polyarylene ether polymers, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymers, polyarylene ketone, polyether ketone, polyarylene phosphine oxide, polyether phosphine oxide, polybenzoxazole, polybenzothiazole, polybenzimidazole, polyamide, polyimide, polyetherimide, and polyimide sulfone in the main chain together with an aromatic ring. The terms "polysulfone," "polyethersulfone," and "polyether ketone" are generic terms for structures having sulfone bonds, ether bonds, or ketone bonds in the molecular chain, and include polyether ketone ketone, polyether ether ketone, polyether ether ketone ketone, polyether ketone ether ketone ketone, and polyether ketone sulfone. The hydrocarbon skeleton may have multiple structures selected from these structures. Among these, the aromatic hydrocarbon polymer is most preferably a polymer having a polyether ketone skeleton, that is, a polyether ketone polymer.

[0050] The hydrocarbon-based polymer electrolyte is preferably a block copolymer having at least one segment (A1) containing an ionic group and at least one segment (A2) not containing an ionic group. Here, the segment refers to a partial structure in a copolymer polymer chain consisting of repeating units exhibiting specific properties and having a molecular weight of 2000 or more. The use of a block copolymer makes it possible to develop a bicontinuous-like phase-separated structure with finer domains than polymer blends, thereby achieving better power generation performance and physical durability.

[0051] Hereinafter, a segment (A1) or polymer containing an ionic group may be referred to as an “ionic block,” and a segment (A2) or polymer not containing an ionic group may be referred to as a “nonionic block.” Note that the expression “not containing an ionic group” does not exclude an embodiment in which the segment or polymer contains a small amount of ionic groups to the extent that the effects of the present invention are not impaired.

[0052] The ionic group possessed by the polymer electrolyte may be any ionic group having proton exchange capacity. Such functional groups are preferably selected from sulfonic acid groups, sulfonimide groups, sulfate groups, phosphonic acid groups, phosphate groups, and carboxylic acid groups. Two or more types of ionic groups may be contained in the polymer. From the viewpoint of high proton conductivity, it is more preferable for the polymer to have at least one group selected from sulfonic acid groups, sulfonimide groups, and sulfate groups, and from the viewpoint of raw material costs, it is most preferable for the polymer to have a sulfonic acid group.

[0053] The ion exchange capacity (IEC) of the polymer electrolyte is preferably 0.1 meq / g or more and 5.0 meq / g or less in terms of the balance between proton conductivity and water resistance. The IEC is more preferably 1.4 meq / g or more, and even more preferably 2.0 meq / g or more. The IEC is more preferably 3.5 meq / g or less, and even more preferably 3.0 meq / g or less. If the IEC is less than 0.1 meq / g, the proton conductivity may be insufficient, and if it is more than 5.0 meq / g, the water resistance may be insufficient.

[0054] Here, IEC is the molar amount of ionic groups introduced per unit dry weight of the polymer electrolyte, and the larger this value, the greater the amount of ionic groups introduced. In the present invention, IEC is defined as a value determined by neutralization titration. The calculation of IEC by neutralization titration is performed according to the method described in Example (2).

[0055] In the present invention, it is particularly preferable to use an aromatic hydrocarbon-based block copolymer as the hydrocarbon-based polymer electrolyte, and more preferably a polyetherketone-based block copolymer. In particular, a polyetherketone-based block copolymer containing a segment including a structural unit (S1) containing an ionic group and a segment including a structural unit (S2) not containing an ionic group, as shown below, can be particularly preferably used.

[0056]

[0057] In general formula (S1), Ar １ ~Ar ４ represents any divalent arylene group, Ar １ and / or Ar ２ contains an ionic group, and Ar ３ and Ar ４ may or may not contain an ionic group. １ ~Ar ４ may be optionally substituted, and two or more types of arylene groups may be used independently. * represents a bonding site to general formula (S1) or other structural units.

[0058]

[0059] In general formula (S2), Ar ５ ~Ar ８ represents any divalent arylene group, which may be optionally substituted but does not contain an ionic group. ５ ~Ar ８ may independently use two or more types of arylene groups. * represents a bonding site with general formula (S2) or another structural unit.

[0060] Here, Ar １ ~Ar ８Preferred divalent arylene groups as Ar include hydrocarbon arylene groups such as phenylene, naphthylene, biphenylene, and fluorenediyl groups, and heteroarylene groups such as pyridinediyl, quinoxalinediyl, and thiophenediyl, but are not limited thereto. Here, the term "phenylene group" can be classified into three types, namely, o-phenylene, m-phenylene, and p-phenylene, depending on the bonding site between the benzene ring and other structural units, and unless otherwise specified, the term will be used as a general term for these in the present specification. The same applies to other divalent arylene groups such as "naphthylene" and "biphenylene". Ar １ ~Ar ８ is preferably a phenylene group and a phenylene group containing an ionic group, and most preferably a p-phenylene group and a p-phenylene group containing an ionic group. ５ ~Ar ８ may be substituted with a group other than an ionic group, but is preferably unsubstituted in terms of proton conductivity, chemical stability, and physical durability.

[0061] In order to obtain sufficient dimensional stability, mechanical strength, physical durability, fuel barrier properties, and solvent resistance, the polymer electrolyte is preferably an aromatic hydrocarbon polymer having crystallinity. Here, "having crystallinity" means that the polymer electrolyte has the property of being crystallizable by heating, or that the polymer electrolyte has already crystallized.

[0062] The presence or absence of crystallizable properties that can be crystallized by raising the temperature can be confirmed by checking that the heat of crystallization measured by differential scanning calorimetry (DSC) after film formation is 0.1 J / g or more. The fact that crystallization has already occurred can be confirmed by checking that the crystallinity measured by wide-angle X-ray diffraction is 0.5% or more. That is, in the present invention, it is preferable that the heat of crystallization measured by differential scanning calorimetry (DSC) after film formation is 0.1 J / g or more, or that the crystallinity measured by wide-angle X-ray diffraction is 0.5% or more.

[0063] Crystalline aromatic hydrocarbon-based polymers may have poor processability for forming electrolyte membranes. In such cases, a protecting group may be introduced into the aromatic hydrocarbon-based polymer to temporarily suppress the crystallinity. Specifically, by forming a membrane with the protecting group introduced and then deprotecting the polymer, the crystalline aromatic hydrocarbon-based polymer can be used as a polymer electrolyte in the present invention.

[0064] When the electrolyte membrane according to the embodiment of the present invention is applied to a water electrolysis device, from the viewpoint of improving water electrolysis performance, the (A) layer preferably contains a hydrocarbon-based polymer electrolyte as the polymer electrolyte. From this viewpoint, the content of the hydrocarbon-based polymer electrolyte in the (A) layer is preferably 60 mass % or more, more preferably 80 mass % or more, even more preferably 90 mass % or more, and particularly preferably 100 mass %, relative to the total mass of the polymer electrolyte in the (A) layer.

[0065] The (A) layer may be reinforced with a porous substrate. Examples of the porous substrate include woven fabric, nonwoven fabric, porous film, mesh fabric, etc. The porous substrate may be made of a known material such as a hydrocarbon-based porous substrate or a fluorine-based porous substrate.

[0066] Layer (A) may contain various additives, such as surfactants, radical scavengers, hydrogen peroxide decomposers, non-electrolytic polymers, elastomers, and fillers, as long as they do not impair the effects of the present invention.

[0067] When the electrolyte membrane of the present invention is applied to a water electrolysis device, the thickness of Layer (A) is preferably relatively large, specifically, preferably 30 μm or more, more preferably 50 μm or more, particularly preferably 70 μm or more, and is preferably 250 μm or less, more preferably 200 μm or less, particularly preferably 175 μm or less.

[0068] [Layer (B)] The layer (B) functions to enhance the bonding between the layer (A) and the catalyst layer, i.e., functions as a bonding layer. The layer (B) has an interface region with the layer (A) and an interface region on the opposite side of the layer (A), and the particle concentrations in these two interface regions are different. Such a layer (B) may be composed of a single layer or may be a laminated structure of two or more layers.

[0069] The electrolyte membrane according to the embodiment of the present invention has layer (B), which can improve the bonding strength between the polymer electrolyte membrane and the catalyst layer. This improved bonding strength can prevent peeling or a decrease in adhesion between the electrolyte membrane and the catalyst layer during operation of a water electrolysis device when the electrolyte membrane is applied to the device. As a result, a decrease in the proton conductivity of the water electrolysis device can be prevented. Therefore, the durability of the water electrolysis device can be improved, for example, the operating voltage of the water electrolysis device can be maintained for a long period of time without increasing.

[0070] Layer (B) preferably further contains a polymer, which can improve film-forming properties and film strength.

[0071] When the (B) layer is a single layer, for example, in the process of applying a coating liquid containing particles and a polymer to the (A) layer, which is placed horizontally or transported horizontally, and then drying it, an operation to increase the particle density on the (A) layer side can be performed, thereby making the particle concentration (Y1) higher than the particle concentration (Y2). Examples of such an operation include using particles with a specific gravity significantly greater than that of the polymer, relatively lowering the viscosity of the coating liquid, and slowing down the drying rate to facilitate particle sedimentation, or a method of causing phase separation between the particles and the polymer. Examples of the phase separation method include using particles and a polymer that has a surface tension significantly lower than that of the particles and is incompatible with the particles, and using a solvent that is relatively compatible with the particles, thereby facilitating uneven distribution of the polymer at the air interface during phase separation during drying.

[0072] The (B) layer preferably has a laminated structure. By forming the (B) layer in a laminated structure, the particle concentrations (Y1) and (Y2) can be easily controlled. For example, by applying a plurality of coating liquids having different particle concentrations to the (A) layer, a (B) layer having a laminated structure in which the particle density varies depending on the layer is formed. The manufacturing method will be described in detail later. When the (B) layer has a laminated structure consisting of n layers, they are referred to as the (B-1) layer, (B-2) layer, ... (B-n) layer in order from the (A) layer side. When the (B) layer has a laminated structure, it is preferable that the particle concentration of the (B-1) layer adjacent to the (A) layer is the highest.

[0073] When the (B) layer has a laminated structure, a two-layer structure or a three-layer structure is preferred, and a two-layer structure is more preferred. In the case of a two-layer structure, the layer adjacent to the (A) layer is the (B-1) layer, and the layer on the opposite side of the (A) layer is the (B-2) layer. Hereinafter, the two-layer structure will be described, but the present invention is not limited to these.

[0074] In the two-layer structure, the (B-1) layer is a layer including an interface region with the (A) layer. That is, the (B-1) layer is a layer that provides a particle concentration (Y1) in the interface region with the (A) layer. The (B-2) layer is a layer that includes an interface region on the opposite side from the (A) layer. That is, the (B-2) layer is a layer that provides a particle concentration (Y2) in the interface region on the opposite side from the (A) layer.

[0075] The particle concentration (Y2) may be 0%, in which case the (B-2) layer does not contain particles. Therefore, when the (B) layer has a two-layer structure, the (B-2) layer may contain no particles, but even in such a case, the (B-1) layer contains particles, so this falls under the category of "the (B) layer contains particles."

[0076] The particle concentration of the (B-1) layer is preferably 45% by mass or more, more preferably 50% by mass or more, and particularly preferably 55% by mass or more. The particle concentration of the (B-2) layer is more preferably less than 45% by mass, even more preferably less than 38%, and particularly preferably less than 35%.

[0077] The (B-1) layer and the (B-2) layer can be formed, for example, by uniformly applying coating liquids prepared to have the particle concentrations described above under typical conditions. In this case, the particle concentrations (ratio of particle mass to total solid mass) in the coating liquids forming the (B-1) layer and the (B-2) layer are the particle concentrations of the (B-1) layer and the (B-2) layer, respectively. In other words, by controlling the particle concentrations in the coating liquids, the (B-1) layer and the (B-2) layer can be given desired particle concentrations. This allows the particle concentration (Y1) in the interface region with the (A) layer to be higher than the particle concentration (Y2) in the interface region of the (B) layer opposite the (A) layer.

[0078] Examples of particles contained in Layer (B) include inorganic particles, organic particles, and organic-inorganic composite particles.

[0079] Examples of inorganic particles include carbon particles, silica, titanium oxide, aluminum oxide, zirconium oxide, cerium oxide, calcium carbonate, zeolite, mica, sericite, sericite, kaolin clay, kaolin, mica, talc, and montmorillonite.

[0080] Among the inorganic particles described above, carbon particles are preferred because they are relatively stable against acids and alkalis. Examples of carbon particles include carbon black, graphite, activated carbon, carbon nanotubes, carbon nanofibers, and fullerene particles.

[0081] Examples of the organic particles include various resin particles. Examples of the resin constituting the resin particles include thermoplastic resins and thermosetting resins such as polyethylene resin, polypropylene resin, polyvinyl acetate resin, poly(meth)acrylic resin, polyvinyl chloride resin, polystyrene resin, polycarbonate resin, polyester resin, polyphenylene sulfide resin, polyamide resin, polyimide resin, polyurethane resin, ethylene-(meth)acrylic acid ester copolymer, ABS resin, fluorine resin, epoxy resin, phenol resin, melamine resin, guanamine resin, polyazole resin, polyethersulfone resin, and polyetherketone resin.

[0082] Examples of organic-inorganic composite particles include acrylic-silica composite particles, melamine-silica composite particles, benzoguanamine-silica composite particles, benzoguanamine-melamine-silica composite particles, polystyrene-silica composite particles, silsesquioxane-based organic-inorganic hybrid particles, and organic-coated inorganic nanoparticles.

[0083] Among the above particles, inorganic particles are preferred, carbon particles are more preferred, and carbon black is particularly preferred.

[0084] From the viewpoints of void formation, dispersibility, and film-forming properties that are effective for bonding, the average particle size of the particles is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 20 nm or more, and is preferably 1,000 nm or less, more preferably 500 nm or less, and particularly preferably 200 nm or less.

[0085] When a polymer is contained in Layer (B), a nonionic polymer or an ionic polymer can be used as the polymer. These polymers can be used alone or in combination.

[0086] Examples of nonionic polymers include fluorine-based polymers and hydrocarbon polymers. Examples of nonionic fluorine-based polymers include polytetrafluoroethylene, poly(vinylidene fluoride), copolymers of vinylidene fluoride and hexafluoropropylene, copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylidene fluoride and tetrafluoroethylene, and poly(vinylidene fluoride).

[0087] Examples of nonionic hydrocarbon polymers include polysulfone, polyethersulfone, polyphenylene oxide, polyarylene ether, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymers, polyarylene ketone, polyether ketone, polyarylene phosphine oxide, polyether phosphine oxide, polybenzoxazole, polybenzothiazole, polybenzimidazole, polyamide, polyimide, polyetherimide, polyimide sulfone, and polyvinyl alcohol.

[0088] Examples of the ionic polymer include ionic fluorine-based polymers and ionic hydrocarbon-based polymers, and examples of these polymers include the polymers given above as examples of the fluorine-based polymer electrolyte and hydrocarbon-based polymer electrolyte.

[0089] Among these, nonionic or ionic fluoropolymers are preferred from the viewpoint of imparting a barrier function to the (B) layer in a high-potential environment, and ionic hydrocarbon polymers and ionic fluoropolymers are preferred from the viewpoint of increasing proton conductivity. That is, when a polymer is contained in the (B) layer, ionic fluoropolymers are most preferred from the above viewpoints. Here, as the ionic fluoropolymer, it is preferable to use the polymers listed above as examples of the fluoropolymer electrolyte.

[0090] When Layer (B) has a laminated structure, the particles and polymers contained in each layer may be the same or different, but from the viewpoint of bonding within Layer (B), it is preferable that they are the same.

[0091] For example, when the (B) layer is composed of two layers, a (B-1) layer that provides a particle concentration (Y1) and a (B-2) layer that provides a particle concentration (Y2), and both the (B-1) layer and the (B-2) layer contain particles, that is, when the ratio (Y2 / Y1) of the particle concentration (Y1) to the particle concentration (Y2) is greater than 0.00, it is preferable that both the (B-1) layer and the (B-2) layer contain the same type of particles. Such particles are preferably carbon particles.

[0092] Layer (B) may contain various additives, such as surfactants, radical scavengers, hydrogen peroxide decomposers, non-electrolytic polymers, elastomers, etc., within the range that does not impair the effects of the present invention.

[0093] The thickness of Layer (B) is preferably 0.5 μm or more, more preferably 0.8 μm or more, and particularly preferably 1 μm or more from the viewpoint of enhancing the bonding function, and is preferably 20 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less from the viewpoint of ensuring good proton conductivity.

[0094] It is particularly preferred that the thickness of layer (A) is 30 μm or more and 250 μm or less, and the thickness of layer (B) is 0.5 μm or more and 20 μm or less.

[0095] When the (B) layer has a laminated structure, the thicknesses of the layers constituting the (B) layer may be the same or different. For example, when the (B) layer has a two-layer structure, the thickness of the (B-1) layer is preferably in the range of 0.25 μm to 10 μm, more preferably in the range of 0.4 μm to 7.5 μm, and particularly preferably in the range of 0.5 μm to 5 μm. The thickness of the (B-2) layer is preferably in the range of 0.25 μm to 10 μm, more preferably in the range of 0.4 μm to 7.5 μm, and particularly preferably in the range of 0.5 μm to 5 μm. When the (B) layer has a two-layer structure, the thicknesses of the (B-1) layer and the (B-2) layer are each preferably 10% or more of the total thickness of the (B) layer. The layer thicknesses can be measured by a contact film thickness measurement method or by SEM observation as described in the examples.

[0096] [Methods for Producing Electrolyte Membrane] Hereinafter, methods for producing an electrolyte membrane will be described, but the present invention is not limited to these methods.

[0097] First, a method for producing the layer (A) will be described. The layer (A) can be formed by, for example, a coating method or a melt extrusion method. Among these, the coating method is preferred. Hereinafter, the coating method will be described as an example, but the present invention is not limited thereto.

[0098] The (A) layer can be produced, for example, by applying a polymer electrolyte solution to a film-forming substrate such as a polyethylene terephthalate (PET) film, followed by drying.

[0099] The (A) layer may be a so-called "composite membrane" reinforced with a porous substrate. This composite membrane preferably has a polymer electrolyte layer on one or both sides of a porous substrate impregnated with a polymer electrolyte. Examples of a method for producing the composite membrane include a method in which a porous substrate is attached to a polymer electrolyte solution applied to a membrane-forming substrate, and the porous substrate is impregnated with the polymer electrolyte solution, and the polymer electrolyte solution is then applied to the porous substrate and dried.

[0100] The polymer electrolyte may also be one in which the ionic groups form salts with alkali metal or alkaline earth metal cations. In this case, after forming the electrolyte membrane on the membrane-forming substrate, it is preferable to perform an acid treatment to exchange the alkali metal or alkaline earth metal cations for protons. Here, the acid treatment may be performed by a known method.

[0101] The electrolyte membrane according to the embodiment of the present invention is produced by laminating the layer (B) on the layer (A) produced as described above. The lamination method is not particularly limited, but a coating method, a transfer method, or a combination thereof can be used.

[0102] The coating method is a method in which a coating liquid for the layer (B) is applied to the layer (A) formed on the film-forming substrate, followed by drying and laminating. The transfer method is a method in which a transfer sheet in which the layer (B) is laminated on a transfer substrate and the layer (A) formed on the film-forming substrate are hot-pressed to transfer the layer (B) to the layer (A).

[0103] When the (B) layer has a laminated structure, a method can be employed in which multiple coating liquids with different particle concentrations are sequentially applied onto the (A) layer formed on the film-forming substrate. Specifically, a method can be employed in which a (B-1) layer coating liquid with a high particle concentration is applied, and a (B-2) layer coating liquid with a low particle concentration is applied undried or after drying, and then dried. Alternatively, a method can be employed in which two coating liquids with different particle concentrations are prepared, and the two coating liquids are simultaneously applied onto the (A) layer using a multilayer die or multilayer slide coater, and then dried.

[0104] As a transfer method, a method can be adopted in which a (B) layer transfer sheet in which a (B-2) layer and a (B-1) layer are sequentially laminated on a transfer substrate and an (A) layer formed on a film-forming substrate are hot-pressed to transfer the (B-1) layer and the (B-2) layer onto the (A) layer.

[0105] Among the above methods, the coating method is more preferred because it has high adhesion to Layer A and can suppress interfacial resistance. The coating method is not particularly limited as long as it can apply coating to the desired shape, and for example, die coating, screen printing, spraying, gravure coating, slide coating, etc. can be used.

[0106] The above-described coating method, transfer method, and a combination of the coating method and the transfer method can also be used in the manufacturing method of an electrolyte membrane in which a (B) layer is laminated on both sides of a (A) layer. In the manufacturing method described below, the (B) layer laminated on one side of the (A) layer is referred to as the first (B) layer, and the (B) layer laminated on the other side of the (A) layer is referred to as the second (B) layer.

[0107] Examples of production methods using a coating method include a production method including a step (1-1) of applying a coating liquid for the first (B) layer onto the (A) layer formed on a film-forming substrate, drying the coating liquid, and laminating the layer; a step (1-2) of peeling off the film-forming substrate to expose the surface of the (A) layer opposite the first (B) layer; and a step (1-3) of applying a coating liquid for the second (B) layer onto the exposed (A) layer, drying the coating liquid, and laminating the layer. Between the above steps (1-1) and (1-3), a step of laminating a protective substrate on the first (B) layer can be provided. The protective substrate can be the same as the film-forming substrate or the transfer substrate, or a resin film with a slightly adhesive layer laminated thereon.

[0108] Examples of production methods using the transfer method include a production method having the steps of (2-1) obtaining a first (B layer) transfer sheet in which a first (B) layer is laminated on a transfer substrate and a second (B) layer transfer sheet in which a second (B) layer is laminated on a transfer substrate, (2-2) peeling the film-forming substrate from the (A) layer formed on the film-forming substrate, and (2-3) sandwiching the (A) layer between the first (B) layer transfer sheet and the second (B) layer transfer sheet and hot-pressing them.

[0109] Examples of a production method using a combination of coating and transfer include a step (3-1) of applying a coating liquid for the first (B) layer onto the (A) layer formed on a film-forming substrate, drying, and laminating the coating liquid, a step (3-2) of obtaining a second (B) layer transfer sheet in which the second (B) layer is laminated on the transfer substrate, a step (3-3) of peeling the film-forming substrate from the (A) layer formed on the film-forming substrate to expose the surface of the (A) layer opposite the first (B) layer, and a step (3-4) of contacting the second (B) layer transfer sheet with the exposed (A) layer and hot-pressing the resulting layer. Between the steps (3-1) and (3-4), a step of laminating a protective substrate on the first (B) layer can be provided.

[0110] A modified example of the manufacturing method using the combined method is a manufacturing method in which the first (B) layer is laminated by a transfer method and the second (B) layer is laminated by a coating method.

[0111] In the above-described manufacturing method, either the first (B) layer or the second (B) layer may have a laminated structure of a (B-1) layer and a (B-2) layer, or both layers may have a laminated structure.

[0112] In the manufacturing process of the CCM, a method of laminating the (B) layer and a catalyst layer together on the (A) layer can also be adopted. Details will be described later.

[0113] The method for preparing the coating liquid for the (B) layer is not particularly limited as long as it is a method that can obtain the desired coating liquid. For example, stirring with a stirrer tip, crushing with a homogenizer, homogenization with a planetary mixer, dispersion with a bead mill or a ball mill, etc. can be used.

[0114] The solvent contained in the coating liquid for the layer (B) is not particularly limited as long as it is a solvent that disperses the particles and polymer, but a solvent that can be easily evaporated and removed by heating is preferred. For example, a solvent with a boiling point of 140° C. or less is preferred. Specific examples of the solvent for the coating liquid for layer (B) include water, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, and pentanol; ketones such as acetone, methyl ethyl ketone, pentanone, hexanone, heptanone, cyclohexanone, methylcyclohexanone, acetonylacetone, and diisobutyl ketone; ethers such as tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, and dibutyl ether; esters such as methyl acetate, ethyl acetate, normal propyl acetate, isopropyl acetate, butyl acetate, methyl lactate, ethyl lactate, and butyl lactate; and dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, propylene glycol, diethylene glycol, diacetone alcohol, and 1-methoxy-2-propanol, which may be used alone or in combination.

[0115] After applying the coating liquid for the layer (B) to the layer (A), a drying step can be performed as needed to form the layer (B). In the drying step, the coating film is heated to evaporate the solvent. The heating means is not particularly limited as long as it can heat the fixed polymer electrolyte membrane, and for example, a heating device such as an oven or heater, or a device that controls the temperature near the polymer electrolyte membrane using infrared rays, hot air, etc. can be used. Heat may also be conducted to the polymer electrolyte membrane via the fixing means. The heating temperature range is preferably close to the boiling point of the solvent and equal to or lower than the glass transition temperature of the polymer electrolyte membrane. Alternatively, the solvent can be removed by simply reducing the pressure or introducing an airflow without heating, and the drying step can also be omitted.

[0116] The (B) layer transfer sheet can be prepared by applying a (B) layer coating liquid onto a transfer substrate, followed by a drying step as needed. The drying step can be performed using the method described above. Subsequently, the (A) layer and the (B) layer-coated surface of the (B) layer transfer sheet are superimposed and hot-pressed to laminate the (B) layer onto the (A) layer. The temperature and pressure of the hot press can be appropriately selected depending on the thickness and moisture content of the (A) layer, the thickness of the (B) layer, and the type of transfer substrate. However, from the viewpoints of industrial productivity and suppression of thermal decomposition of the polymer electrolyte, hot pressing is preferably performed in the range of 120°C to 250°C. Specifically, hot pressing is more preferably performed at a temperature higher than the glass transition temperature of the polymer contained in the (B) layer and 200°C or lower. The pressure applied during hot pressing is preferably as low as possible from the viewpoint of protecting the electrolyte membrane; for example, in the case of flat-plate pressing, a pressure of 2 to 10 MPa is preferred.

[0117] The transfer substrate may be a resin film or substrate similar to the substrate used in forming Layer (A), or a fluororesin film made of a fluororesin such as polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, ethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, polyvinylidene fluoride, polyimide, or polyphenylene sulfide. The transfer substrate may also be a substrate such as a resin film on which a release layer containing a known release agent such as a fluorine-based release agent is laminated to enhance releasability. As the transfer substrate used in the present invention, polyimide, polyphenylene sulfide, and fluororesin films are preferred from the viewpoints of heat resistance, solvent resistance, and chemical stability, and fluororesin films are even more preferred from the viewpoint of releasability.

[0118] [Catalyst-Coated Electrolyte Membrane (CCM)] The electrolyte membrane according to the embodiment of the present invention can be made into a CCM by disposing a catalyst layer on one or both sides of the electrolyte membrane. That is, the catalyst-coated electrolyte membrane has a catalyst layer on one or both sides of the electrolyte membrane.

[0119] [Catalyst Layer] The catalyst layer is generally a layer containing catalyst particles and a polymer electrolyte. The catalyst layer can be formed by laminating a catalyst layer coating liquid, which is a polymer electrolyte solution containing catalyst particles, on an electrolyte membrane by a coating method or a transfer method. The polymer electrolyte can be a hydrocarbon-based polymer electrolyte or a fluorine-based polymer electrolyte, as described above. From the viewpoints of gas diffusion properties and chemical durability, a fluorine-based polymer electrolyte is preferred, and a perfluorocarbon sulfonic acid-based polymer is more preferred. It is also preferred that the polymer electrolyte contained in the (A) layer and the polymer electrolyte contained in the catalyst layer are different from each other. It is also preferred that the (B) layer contains the same type of polymer as the catalyst layer. It is also more preferred that the (A) layer contains a hydrocarbon-based polymer electrolyte, the catalyst layer contains a fluorine-based polymer electrolyte, and the (B) layer contains a nonionic or ionic fluorine-based polymer, and it is particularly preferred that the (B) layer contains an ionic fluorine-based polymer.

[0120] As catalyst particles, generally used are metals such as platinum group elements (platinum, ruthenium, rhodium, palladium, osmium, iridium), iron, lead, gold, silver, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, or alloys, oxides, double oxides, etc. Carbon particles carrying the above metals (catalyst-supported carbon particles) are also commonly used. The carbon particles are not particularly limited as long as they are fine particles, electrically conductive, and do not corrode or deteriorate due to reaction with the catalyst, but carbon black, graphite, activated carbon, carbon fiber, carbon nanotubes, and fullerene particles are preferably used.

[0121] In the catalyst layer, the mass ratio (C / I) of the content (C) of catalyst particles (including catalyst-supporting particles) to the content (I) of polymer electrolyte is generally in the range of 1.0 to 15.0, and preferably in the range of 1.5 to 13.0.

[0122] When applied to a water electrolysis device, the mass ratio (C / I) in the anode catalyst layer is preferably 4.0 or more, more preferably 5.0 or more, and particularly preferably 7.0 or more. It is also preferably 15.0 or less, more preferably 14.0 or less, and particularly preferably 13.0 or less. Meanwhile, the mass ratio (C / I) in the cathode catalyst layer is preferably less than 4.0, more preferably less than 3.5, and particularly preferably less than 3.0. It is also preferably 1.0 or more, more preferably 1.5 or more, and particularly preferably 1.7 or more.

[0123] From the viewpoints of gas diffusibility and durability, the thickness of the catalyst layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and particularly preferably 1 μm or more, and is preferably 500 μm or less, more preferably 100 μm or less, and particularly preferably 30 μm or less.

[0124] The anode catalyst layer and the cathode catalyst layer may be made of the same material or different materials. When a CCM is applied to a water electrolysis device, the anode catalyst layer may be a catalyst that generates oxygen using water or hydroxide as catalyst particles. From this perspective, it is preferable that the anode catalyst layer uses a noble metal such as iridium, ruthenium, rhodium, or palladium, or an oxide thereof.

[0125] These catalysts are preferably used in the form of particles. In this case, the catalyst particles may be used in the form of single particles or may be used as catalyst-supported particles supported on titanium oxide or the like.

[0126] The cathode catalyst layer may be any catalyst that generates hydrogen using protons or water as a raw material as catalyst particles. From this perspective, the cathode catalyst layer preferably uses platinum-supported carbon particles in which platinum is supported on carbon particles.

[0127] In water electrolysis devices, "crossover" can occur, in which hydrogen generated at the cathode permeates the electrolyte membrane and reaches the anode. When crossover occurs, hydrogen becomes mixed with oxygen generated at the anode, increasing the risk of explosion. As one form of avoiding such a risk, the anode catalyst layer preferably contains iridium and at least one precious metal element selected from the group consisting of platinum, ruthenium, rhodium, palladium, gold, silver, and osmium. Hereinafter, "precious metals other than iridium" may be referred to as "other precious metals." As other precious metals, platinum and palladium are preferred, with platinum being particularly preferred.

[0128] The form in which iridium element and other precious metal element are contained in the anode catalyst layer is not particularly limited, and known forms can be used, such as (I) a form in which particles containing iridium element (hereinafter referred to as "iridium-based particles") and particles containing other precious metal element (hereinafter referred to as "other precious metal-based particles") are contained, (II) a form in which alloy particles of iridium and other precious metal are used, and (III) a form in which iridium and other precious metal are laminated by sputtering or vapor deposition.

[0129] The iridium element is preferably contained in the anode catalyst layer in the form of iridium-based particles. The other precious metal element is preferably contained in the anode catalyst layer in the form of particles containing the other precious metal element. From this viewpoint, among the above-mentioned embodiments, embodiment (I) is more preferred. That is, the anode catalyst layer preferably contains particles containing iridium element and particles containing the other precious metal element.

[0130] More specifically, examples of the above-mentioned form (I) include (I-1) a form in which iridium-based particles and other precious metal-based particles are contained singly, (I-2) a form in which catalyst-supported particles are used in which iridium-based particles and other precious metal-based particles are supported together or separately on a carrier made of a metal oxide such as titanium oxide or tin oxide, and (I-3) a form in which so-called core-shell particles or composite particles are used in which part or all of the surface of iridium-based particles is covered with other precious metal-based particles.

[0131] In the case of the above-mentioned embodiment (I-1), examples include an embodiment in which the first layer has a single layer configuration in which iridium-based particles and other precious metal-based particles are mixed together, and an embodiment in which the first layer has a multilayer configuration in which an iridium-based particle-containing layer and a other precious metal-based particle-containing layer are both included, with the former being preferred.

[0132] Examples of iridium-based particles include iridium particles and iridium oxide particles.

[0133] From the viewpoint of stability at high potential, the iridium element is preferably contained in the anode catalyst layer in the form of iridium oxide, that is, the anode catalyst layer preferably contains iridium oxide.

[0134] As the other precious metal particles, platinum particles and palladium particles are preferred, with platinum particles being particularly preferred. As particles containing other precious metal elements, particles that are not supported on a carrier, so-called "black" particles, can be used. Examples include platinum black (black) and palladium black (black). Furthermore, as particles containing other precious metal elements, as described above, catalyst-supported particles in which particles containing other precious metal elements are supported on a carrier made of a metal oxide such as titanium oxide or tin oxide can be used.

[0135] Carbon particles such as carbon black are generally known as supports for catalyst-supported particles. However, since the anode in a water electrolysis device is in a high-potential environment and there are concerns about the resistance of carbon particles to electrochemical oxidation, it is preferable not to use carbon particles in the anode catalyst layer.

[0136] The iridium-based particles and other noble metal-based particles can be synthesized or produced by known methods. Alternatively, commercially available products can be used. For example, commercially available iridium oxide particles include "IrO ２Available catalysts include "Elyst" and "iridium oxide powder manufactured by Tokuriki Honten," platinum blacks include "HISPEC1000 manufactured by Johnson Matthey," "TEC90300 and TEC90400 manufactured by Tanaka Kikinzoku Kogyo," "PtBlack manufactured by BASF," "Platinum Black manufactured by Tokuriki Honten," and "Platinum Black manufactured by Ishifuku Kinzoku Kogyo," and palladium blacks include "Palladium Black manufactured by Soekawa Rikagaku," "Pd-black manufactured by Alfa Aesar," and "PdBlack manufactured by Wako Pure Chemical Industries." These particles can be crushed to a desired particle size, for example, about 1 to 100 nm, before use.

[0137] With respect to the mass of iridium element (Ir mass) and the mass of other precious metal element (NM mass) in the anode catalyst layer, a larger Ir mass is preferable from the viewpoint of ensuring good water electrolysis performance, while a larger NM mass is preferable from the viewpoint of reducing the hydrogen concentration in oxygen gas. From the viewpoint of appropriately balancing these effects, the ratio of Ir mass to NM mass (Ir mass:NM mass) is preferably in the range of 51:49 to 99:1, more preferably in the range of 55:45 to 95:5, even more preferably in the range of 60:40 to 92:8, and particularly preferably in the range of 65:35 to 90:10.

[0138] Here, the content ratio of Ir mass and NM mass can be calculated by analyzing a cross-sectional image of the catalyst layer with an electron probe microanalyzer (EPMA) to measure the mass ratio of each element.

[0139] In the anode catalyst layer, the mass of iridium element per unit area is 0.2 to 2.0 mg / cm ２ The range is preferably 0.4 to 1.5 mg / cm ２ The range of 0.6 to 1.3 mg / cm is more preferable. ２ The range is particularly preferred.

[0140] In the anode catalyst layer, the mass per unit area of ​​the other precious metal element is preferably set appropriately within the above-mentioned ratio (Ir mass:NM mass) based on the above-mentioned mass of iridium element per unit area.

[0141] In a configuration in which the anode catalyst layer contains iridium and another precious metal as catalysts, the (B) layer of the electrolyte membrane disposed on the anode catalyst layer side preferably contains a fluorine-based polymer electrolyte. This combination can significantly reduce the hydrogen gas concentration in the oxygen gas generated at the anode.

[0142] [Method for manufacturing a CCM] A CCM according to an embodiment of the present invention is manufactured by laminating a catalyst layer on an electrolyte membrane. The method for laminating the catalyst layer is not particularly limited, and a coating method, a transfer method, or a combination of these methods can be used. The coating method is a method in which a catalyst layer coating liquid is applied to the electrolyte membrane and dried to laminate. The transfer method is a method in which a catalyst layer transfer sheet, in which a catalyst layer is laminated on a transfer substrate, and the electrolyte membrane are heated and pressed to laminate them. Among these, the transfer method is preferred. The transfer substrate used for the catalyst layer transfer sheet can be the same resin film or substrate as described above.

[0143] Hereinafter, several methods for manufacturing a CCM using a transfer method will be described as examples, but the present invention is not limited to these manufacturing methods.

[0144] One CCM manufacturing method (I) that can be adopted is a manufacturing method including the steps of obtaining an electrolyte membrane in which a (B) layer is laminated on an (A) layer, obtaining a catalyst layer transfer sheet in which a catalyst layer is laminated on a transfer substrate, and bringing the (B) layer of the electrolyte membrane and the catalyst layer of the transfer sheet into face-to-face contact and hot-pressing them.

[0145] Another CCM production method that can be used is a production method in which the (B) layer and catalyst layer are transferred together onto the (A) layer. As such a CCM production method (II), a production method can be used that includes the steps of forming the (A) layer, obtaining a catalyst layer / (B) layer transfer sheet in which the catalyst layer and the (B) layer are sequentially laminated on a transfer substrate, and bringing the (A) layer into contact with the (B) layer of the transfer sheet and hot-pressing them.

[0146] The catalyst layer / (B) layer transfer sheet used in the above-mentioned CCM production method (II) is useful as one component for obtaining a CCM according to an embodiment of the present invention. That is, one component for obtaining a CCM according to an embodiment of the present invention comprises, for example, a catalyst layer / (B) layer transfer sheet in which a catalyst layer and a (B) layer are sequentially laminated on a transfer substrate.

[0147] Furthermore, in the above-described CCM production method (II), when the (B) layer has a two-layer structure consisting of a (B-1) layer that provides particle concentration (Y1) and a (B-2) layer that provides particle concentration (Y2), a catalyst layer / (B) layer transfer sheet can be used, in which the catalyst layer, the (B-2) layer, and the (B-1) layer are sequentially laminated on a transfer substrate. This transfer sheet is useful as one component for obtaining a CCM according to an embodiment of the present invention. That is, one component for obtaining a CCM according to an embodiment of the present invention comprises, for example, a catalyst layer / (B-2) layer / (B-1) layer transfer sheet, in which the catalyst layer, the (B-2) layer, and the (B-1) layer are sequentially laminated on a transfer substrate.

[0148] Furthermore, as another CCM production method (III) when the (B) layer has a two-layer structure, a production method can be adopted which includes the steps of obtaining a laminate in which the (B-1) layer is laminated on the (A) layer, obtaining a catalyst layer / (B-2) layer transfer sheet in which the catalyst layer and the (B-2) layer are laminated in that order on a transfer substrate, and bringing the (B-1) layer of the laminate and the (B-2) layer of the transfer sheet into face-to-face contact and hot-pressing them.

[0149] The catalyst layer / (B-2) layer transfer sheet used in the above-mentioned CCM production method (III) is useful as one component for obtaining a CCM according to an embodiment of the present invention. That is, one component for obtaining a CCM according to an embodiment of the present invention comprises, for example, a catalyst layer / (B-2) layer transfer sheet in which a catalyst layer and a (B-2) layer are sequentially laminated on a transfer substrate.

[0150] The transfer sheet used in the above-mentioned CCM production methods (II) and (III), i.e., the member for obtaining a CCM, can be produced, for example, by applying a catalyst layer coating liquid to a transfer substrate, and then applying and drying a (B) layer coating liquid while the substrate is still wet or after drying. Alternatively, a method can be employed in which the catalyst layer coating liquid and the (B) layer coating liquid are simultaneously applied to the transfer substrate using a multilayer die or multilayer slide coater and then dried. The coating method is not particularly limited as long as it can be applied to the desired shape, and examples of methods that can be used include die coating, screen printing, spraying, gravure coating, and slide coating.

[0151] In the above-mentioned CCM production method, the temperature and pressure of the hot press may be appropriately selected depending on the thickness and moisture content of the (A) layer, the thicknesses of the (B) layer and catalyst layer, and the type of transfer substrate, but from the viewpoints of industrial productivity and suppression of thermal decomposition of the polymer electrolyte, it is preferable to perform the hot press at a temperature in the range of 120°C to 250°C. Specifically, it is more preferable to perform the hot press at a temperature higher than the glass transition temperature of the polymer contained in the (B) layer and not higher than 200°C. From the viewpoint of protecting the electrolyte membrane, it is preferable that the pressure in the hot press be as weak as possible; for example, in the case of plate pressing, a pressure in the range of 2 to 10 MPa is preferable.

[0152] [Membrane Electrode Assembly] The membrane electrode assembly includes the above-mentioned CCM and gas diffusion layers (gas diffusion electrodes) disposed on both sides of the CCM. Specifically, the anode gas diffusion layer is disposed and bonded to the anode catalyst layer side of the CCM, and the cathode gas diffusion layer is disposed and bonded to the cathode catalyst layer side of the CCM.

[0153] Gas diffusion layers are generally made of materials that are gas permeable and electronically conductive, such as porous carbon and porous metal. Examples of porous carbon materials include carbon paper, carbon cloth, carbon mesh, and carbon nonwoven fabric. Examples of porous metal materials include metal mesh, foam metal, woven metal fabric, sintered metal, and nonwoven metal fabric. Examples of metals include titanium, aluminum, copper, nickel, nickel-chromium alloys, copper and its alloys, silver, aluminum alloys, zinc alloys, lead alloys, titanium, niobium, tantalum, iron, stainless steel, gold, and platinum.

[0154] The gas diffusion layer can be subjected to a water-repellent treatment to prevent a decrease in gas diffusion and permeability due to water retention, a partial water-repellent treatment or a partial hydrophilic treatment to form a water drainage path, or the addition of carbon powder to reduce resistance. The gas diffusion layer can also be provided with a conductive intermediate layer containing at least an inorganic conductive material and a hydrophobic polymer on the CCM side. In particular, when the gas diffusion layer is made of a carbon fiber woven fabric or nonwoven fabric with a high porosity, providing a conductive intermediate layer can prevent performance degradation due to the catalyst solution seeping into the gas diffusion layer.

[0155] The thickness of the gas diffusion layer is preferably 50 μm or more, more preferably 100 μm or more, and particularly preferably 150 μm or more, and is preferably 1,000 μm or less, more preferably 700 μm or less, and particularly preferably 500 μm or less.

[0156] The anode gas diffusion layer and the cathode gas diffusion layer may be made of the same material or different materials. When the membrane electrode assembly is applied to a water electrolysis hydrogen generation device, the anode gas diffusion layer and the cathode gas diffusion layer are preferably made of different materials. For example, the anode gas diffusion layer is preferably made of a porous metal material, and the cathode gas diffusion layer is preferably made of a porous carbon material.

[0157] [Application Examples] The electrolyte membrane according to the embodiment of the present invention, and the CCM and membrane electrode assembly using the electrolyte membrane can be applied to, for example, electrochemical applications. Examples of electrochemical applications include fuel cells, redox flow batteries, water electrolysis devices, and electrochemical hydrogen compression devices. Among these, application to water electrolysis devices is preferred, and application to water electrolysis hydrogen generation devices is particularly preferred.

[0158] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. The various measurement conditions are as follows.

[0159] (1) Molecular Weight of Polymer The number average molecular weight and weight average molecular weight of the polymer solution were measured by gel permeation chromatography (GPC). The instrument used was an HLC-8022 GPC manufactured by Tosoh Corporation. An ultraviolet detector and a differential refractometer were used as detectors. Two TSK gel Super HM-H (inner diameter 6.0 mm, length 15 cm) GPC columns manufactured by Tosoh Corporation were used. Measurements were performed at a flow rate of 0.2 mL / min using N-methyl-2-pyrrolidone solvent (N-methyl-2-pyrrolidone solvent containing 10 mmol / L of lithium bromide) as the developing solvent, and the number average molecular weight and weight average molecular weight were calculated in terms of standard polystyrene.

[0160] (2) Ion Exchange Capacity (IEC) of Polymer: A solution of a polymer dissolved in NMP was applied to a PET film and dried to prepare an electrolyte membrane. The ion exchange capacity of this electrolyte membrane was measured by neutralization titration. The measurement was performed three times, and the average value was taken.

[0161] After the proton substitution and thorough washing with pure water, the moisture on the surface of the electrolyte membrane was wiped off, and the membrane was then vacuum dried at 100° C. for 12 hours or more, and the dry weight was determined.

[0162] 50 mL of a 5% by mass aqueous solution of sodium sulfate was added to the electrolyte membrane, and the membrane was allowed to stand for 12 hours to carry out ion exchange.

[0163] The sodium sulfate aqueous solution after ion exchange was titrated with 0.01 mol / L sodium hydroxide aqueous solution. 0.1 w / v % commercially available phenolphthalein solution for titration was added as an indicator, and the point at which the solution turned a light reddish purple color was defined as the endpoint.

[0164] The ion exchange capacity (IEC) was calculated by the following formula.

[0165] IEC (meq / g) = [concentration of aqueous sodium hydroxide solution (mmol / mL) x amount dropped (mL)] / dry weight of sample (g).

[0166] (3) Evaluation of particle concentrations (Y1) and (Y2) in the (B) layer A sample was prepared by cutting a cross section of the electrolyte membrane using cryo-ultrathin sectioning. Images of this sample were obtained using a scanning transmission electron microscope (STEM) at a magnification that allowed the thickness of the (B) layer to be determined, and the thickness of the (B) layer was measured. From the obtained thickness of the (B) layer, regions (interface regions) 10% thick from both interfaces of the (B) layer were determined, and the presence or absence of particles in both interface regions was confirmed. If the above observation confirmed the presence of particles in both interface regions, elemental analysis of both interface regions was performed using a scanning transmission electron microscope-energy dispersive X-ray analyzer (STEM-EDX). Taking Example 1 as an example, the (B) layer contains particles (carbon black) and a polymer (fluorine-based polymer electrolyte). The mass ratio of the particles to the polymer was calculated from the ratio "C / F" of the element "C" to the element "F" obtained by elemental analysis in the interface region with the (A) layer, the structural formula of the particles, and the structural formula of the polymer, to determine the particle concentration (Y1). Similarly, the particle concentration (Y2) was determined from the ratio "C / F" in the interface region on the opposite side from the (A) layer.

[0167] <Cross-section observation by scanning transmission electron microscope (STEM)> Apparatus: field emission scanning transmission electron microscope JEM-2100F (manufactured by JEOL Ltd.) Acceleration voltage: 200 kV Magnification: 50,000 to 150,000 times <Elemental analysis by scanning transmission electron microscope-energy dispersive X-ray analyzer (STEM-EDX)> Apparatus: field emission scanning transmission electron microscope JEM-2100F (manufactured by JEOL Ltd.) EDX detector: JED-2300T (manufactured by JEOL Ltd.) EDX detection system: Analysis Station Acceleration voltage: 200 kV Beam diameter: 1 nmΦ Measurement time: 30 seconds Measured elements: C and F, or Ce and F.

[0168] (4) Measurement of the film thickness of each layer by SEM observation The cross sections of the electrolyte membrane and CCM were observed using a scanning electron microscope (SEM) under the following conditions, and the thickness of each layer was measured from the obtained images. Apparatus: Cold cathode field emission scanning electron microscope (FE-SEM) SU-8020 (Hitachi High-Technologies Corporation) Acceleration voltage: 5.0 kV Detection signal: Backscattered electrons Pretreatment: Measurements were performed on a cross-sectional sample prepared using the BIB method, which was then coated with platinum. The BIB method is a cross-sectional sample preparation device that uses an argon ion beam. A shielding plate is placed directly above the sample, and a broad argon ion beam is irradiated from above to etch the sample, creating an observation and analysis surface (cross section).

[0169] (5) Evaluation of Interlayer Bonding (Peeling Properties) The CCMs prepared in Examples and Comparative Examples, each having a catalyst layer laminated on an electrolyte membrane, were cut into 2 cm x 2 cm pieces to prepare test specimens. The test specimens were immersed in 20 g of ion-exchanged water at 80°C for 6, 12, 18, and 24 hours, and the bonding state between the electrolyte membrane and the catalyst layer was observed and evaluated according to the following criteria: A: No peeling occurred even after 24 hours of immersion; B: No peeling occurred after 18 hours of immersion, but peeling occurred after 24 hours of immersion; C: No peeling occurred after 12 hours of immersion, but peeling occurred after 18 hours of immersion; D: No peeling occurred after 6 hours of immersion, but peeling occurred after 12 hours of immersion; and E: Peeling occurred after 6 hours of immersion.

[0170] (6) Evaluation of durability A membrane electrode assembly was produced by laminating a commercially available gas diffusion electrode 24BCH manufactured by SGL as a cathode gas diffusion layer on the cathode catalyst layer side of a CCM in which a catalyst layer was laminated on both sides of the electrolyte membrane produced in the Examples and Comparative Examples, and laminating a commercially available porous titanium sintered plate as an anode gas diffusion layer on the anode catalyst layer side of the CCM.

[0171] The membrane electrode assembly prepared above was placed in a JARI standard cell "Ex-1" (electrode area 25 cm) manufactured by Eiwa Co., Ltd. ２ The cell was set to a pressure of 4 MPa, and the cell temperature was set to 80°C. Deionized water with an electrical conductivity of 1 μS / cm or less was supplied to both the cathode and anode electrodes at atmospheric pressure and a flow rate of 0.2 L / min.２ A current of 1000 kJ / s was applied to the electrode to produce hydrogen gas and oxygen gas through a water electrolysis reaction.

[0172] Durability: 2.0 A / cm ２ The voltage (V １ ) initial applied voltage (V ０ The smaller the voltage rise rate, the better the durability. The voltage rise rate was calculated using the following formula: Voltage rise rate (%) = (V １ -V ０ ) × 100 / (V ０ In the durability test, a decrease in the bonding strength between the electrolyte membrane and the catalyst layer during operation causes an increase in the applied voltage.

[0173] (7) Measurement of Hydrogen Gas Concentration in Oxygen Gas In the durability evaluation, the produced oxygen gas discharged from the anode was sampled every 25 hours from the start of operation, and after removing water from this oxygen gas, it was introduced into a gas chromatography analyzer, and the hydrogen gas concentration (ppm, volume ratio) in the oxygen gas was measured and averaged under the following conditions: Apparatus: 490 Micro GC, manufactured by Agilent Technologies, Inc. Column: Agilent Technologies, Inc., Part Number 493001360, Type BF CHA 10 m MS5A Unl, Facl Carrier gas: Ar Column temperature: 100°C.

[0174] Synthesis Example 1 (Synthesis of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane (K-DHBP) represented by the following chemical formula (G1)) A 500 mL flask equipped with a stirrer, thermometer, and distillation tube was charged with 49.5 g of 4,4'-dihydroxybenzophenone, 134 g of ethylene glycol, 96.9 g of trimethyl orthoformate, and 0.50 g of p-toluenesulfonic acid monohydrate, and dissolved therein. The mixture was then stirred and kept at 78 to 82°C for 2 hours. The internal temperature was then gradually raised to 120°C, and the mixture was heated until the distillation of methyl formate, methanol, and trimethyl orthoformate completely stopped. After cooling this reaction solution to room temperature, the reaction solution was diluted with ethyl acetate, and the organic layer was washed with 100 mL of a 5% aqueous potassium carbonate solution and separated, followed by distilling off the solvent. 80 mL of dichloromethane was added to the residue to precipitate crystals, which were filtered and dried to obtain 52.0 g of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane represented by the following chemical formula (G1). Gas chromatography (GC) analysis of the crystals revealed that they were 99.9% 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane and 0.1% 4,4'-dihydroxybenzophenone. The purity was 99.9%.

[0175]

[0176] Synthesis Example 2 (Synthesis of disodium-3,3'-disulfonate-4,4'-difluorobenzophenone represented by the following chemical formula (G2)) 109.1 g of 4,4'-difluorobenzophenone (Sigma-Aldrich Japan (same) reagent) was dissolved in fuming sulfuric acid (50% SO ３ The resulting mixture was reacted at 100°C for 10 hours in 150 mL of ethanol (Fujifilm Wako Pure Chemical Industries, Ltd., reagent). The mixture was then poured little by little into a large amount of water, neutralized with NaOH, and 200 g of table salt (NaCl) was added to precipitate the synthesized product. The resulting precipitate was filtered and recrystallized with an aqueous ethanol solution to obtain disodium-3,3'-disulfonate-4,4'-difluorobenzophenone represented by the following chemical formula (G2). The purity was 99.3%.

[0177]

[0178] Synthesis Example 3 (Synthesis of nonionic oligomer a1 represented by the following general formula (G3)) 16.59 g of potassium carbonate (Aldrich reagent, 120 mmol), 25.83 g (100 mmol) of K-DHBP obtained in Synthesis Example 1, and 20.3 g of 4,4'-difluorobenzophenone (Aldrich reagent, 93 mmol) were placed in a 2,000 mL SUS polymerization reactor equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap. After replacing the atmosphere inside the reactor with nitrogen, 300 mL of N-methylpyrrolidone (NMP) and 100 mL of toluene were added, and the mixture was dehydrated at 150°C. After the temperature was raised to remove the toluene, polymerization was carried out at 170°C for 3 hours. Purification by reprecipitation with a large amount of methanol was carried out to obtain a terminal hydroxyl form of nonionic oligomer a1. The number average molecular weight of the terminal hydroxyl form of this nonionic oligomer a1 was 10,000. A 500 mL three-neck flask equipped with a stirrer, nitrogen inlet tube, and Dean-Stark trap was charged with 1.1 g of potassium carbonate (Sigma-Aldrich Japan (same) reagent, 8 mmol) and 20.0 g (2 mmol) of the terminal hydroxy compound of the above nonionic oligomer a1. After replacing the atmosphere inside the flask with nitrogen, 100 mL of NMP and 30 mL of toluene were added, and the mixture was dehydrated at 100°C and then heated to remove the toluene. Furthermore, 2.2 g of hexafluorobenzene (Sigma-Aldrich Japan (same) reagent, 12 mmol) was added, and the reaction was carried out at 105°C for 12 hours. Purification was carried out by reprecipitation with a large amount of isopropyl alcohol, yielding nonionic oligomer a1 (terminal: fluoro group) represented by the following general formula (G3). The number average molecular weight was 11,000.

[0179]

[0180] Synthesis Example 4 Synthesis of Ionic Oligomer a2 Represented by General Formula (G4) Below Into a 2,000 mL SUS polymerization reactor equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap, 27.6 g of potassium carbonate (Sigma-Aldrich Japan (same manufacturer) reagent, 200 mmol), 12.9 g (50 mmol) of K-DHBP obtained in Synthesis Example 1, 9.3 g of 4,4′-biphenol (Sigma-Aldrich Japan (same manufacturer) reagent, 50 mmol), 39.3 g (93 mmol) of disodium-3,3′-disulfonate-4,4′-difluorobenzophenone obtained in Synthesis Example 2, and 17.9 g of 18-crown-6 (Fujifilm Wako Pure Chemical Industries, Ltd., 82 mmol) were placed. After replacing the atmosphere in the reactor with nitrogen, 300 mL of NMP and 100 mL of toluene were added, and the mixture was dehydrated at 150°C. The temperature was then raised to remove the toluene, and polymerization was carried out at 170°C for 6 hours. Purification by reprecipitation with a large amount of isopropyl alcohol yielded an ionic oligomer a2 (terminal: hydroxy group) represented by the following general formula (G4). The number average molecular weight was 16,000. In general formula (G4), M represents H, Na, or K.

[0181]

[0182] Synthesis Example 5 (Synthesis of neopentyl 3-(2,5-dichlorobenzoyl)benzenesulfonate represented by the following chemical formula (G5)) 245 g (2.1 mol) of chlorosulfonic acid was placed in a 3 L three-neck flask equipped with a stirrer and a condenser, followed by the addition of 105 g (420 mmol) of 2,5-dichlorobenzophenone, and the mixture was reacted for 8 hours in an oil bath at 100°C. After the predetermined time, the reaction solution was slowly poured into 1,000 g of crushed ice and extracted with ethyl acetate. The organic layer was washed with brine and dried over magnesium sulfate, and the ethyl acetate was then distilled off to obtain pale yellow crude crystals of 3-(2,5-dichlorobenzoyl)benzenesulfonyl chloride. The crude crystals were used directly in the next step without purification.

[0183] 41.1 g (462 mmol) of 2,2-dimethyl-1-propanol (neopentyl alcohol) was added to 300 mL of pyridine and cooled to approximately 10°C. The crude crystals obtained above were gradually added over approximately 30 minutes. After the entire amount was added, the mixture was stirred for an additional 30 minutes to allow the reaction to proceed. After the reaction, the reaction solution was poured into 1,000 mL of aqueous hydrochloric acid, and the precipitated solid was collected. The resulting solid was dissolved in ethyl acetate, washed with aqueous sodium bicarbonate and brine, dried over magnesium sulfate, and the ethyl acetate was distilled off to obtain crude crystals. These were recrystallized from methanol to obtain white crystals of neopentyl 3-(2,5-dichlorobenzoyl)benzenesulfonate, represented by the following chemical formula (G5).

[0184]

[0185] Synthesis Example 6 (Synthesis of an oligomer not containing an ionic group represented by the following general formula (G6)) 49.4 g (0.29 mol) of 2,6-dichlorobenzonitrile, 88.4 g (0.26 mol) of 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane, and 47.3 g (0.34 mol) of potassium carbonate were weighed into a 1 L three-necked flask equipped with a stirrer, thermometer, condenser, Dean-Stark tube, and a three-way stopcock for nitrogen introduction. After the atmosphere in the flask was replaced with nitrogen, 346 mL of sulfolane and 173 mL of toluene were added and stirred. The flask was placed in an oil bath and heated to reflux at 150°C. The water produced by the reaction was azeotroped with toluene and the reaction was continued while being removed from the system using a Dean-Stark tube. After approximately 3 hours, almost no water was produced. After removing most of the toluene while gradually increasing the reaction temperature, the reaction was continued for 3 hours at 200° C. Next, 12.3 g (0.072 mol) of 2,6-dichlorobenzonitrile was added, and the reaction was continued for another 5 hours.

[0186] The resulting reaction solution was allowed to cool and then diluted with 100 mL of toluene. The precipitated inorganic compound by-product was removed by filtration, and the filtrate was poured into 2 L of methanol. The precipitated product was filtered, collected, dried, and then dissolved in 250 mL of tetrahydrofuran. This was reprecipitated in 2 L of methanol to obtain 107 g of the target oligomer represented by the following general formula (G6). The number average molecular weight was 11,000.

[0187]

[0188] Synthesis Example 7 (Synthesis of polyethersulfone (PES)-based block copolymer precursor b1 composed of a segment represented by the following chemical formula (G8) and a segment represented by the following general formula (G9)) 1.62 g of anhydrous nickel chloride and 15 mL of dimethyl sulfoxide were mixed and adjusted to 70° C. 2.15 g of 2,2′-bipyridyl was added thereto and stirred at the same temperature for 10 minutes to prepare a nickel-containing solution.

[0189] To this solution, 1.49 g of 2,5-dichlorobenzenesulfonic acid (2,2-dimethylpropyl) and 0.50 g of Sumikaexcel PES5200P (manufactured by Sumitomo Chemical Co., Ltd., Mn = 40,000, Mw = 94,000), represented by the following general formula (G7), were dissolved in 5 mL of dimethyl sulfoxide. 1.23 g of zinc powder was added and the temperature was adjusted to 70°C. The nickel-containing solution was poured into this solution, and a polymerization reaction was carried out at 70°C for 4 hours. The reaction mixture was added to 60 mL of methanol, and then 60 mL of 6 mol / L hydrochloric acid was added and stirred for 1 hour. The precipitated solid was separated by filtration and dried to obtain 1.62 g of a grayish-white block copolymer precursor b1 containing segments represented by the following general formula (G8) and the following general formula (G9), in a yield of 99%. The weight-average molecular weight was 230,000.

[0190]

[0191]

[0192]

[0193] [Preparation of Coating Liquid for Layer (A)] Coating liquids p1 to p4 containing various polymer electrolytes were prepared in the following manner.

[0194] [Coating liquid p1]: Coating liquid containing polyether ketone block copolymer P1 16 g of ionic oligomer a2 and 11 g of nonionic oligomer a1 were placed in a 2,000 mL SUS polymerization reactor equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap, and NMP was added so that the total amount of the oligomers charged was 7 wt %, followed by reaction at 105°C for 24 hours.

[0195] Reprecipitation was carried out in a large amount of an isopropyl alcohol / NMP mixed solution (weight ratio 2 / 1), and the resulting precipitate was collected by filtration and washed with a large amount of isopropyl alcohol to obtain block copolymer P1. The weight average molecular weight was 340,000. The ion exchange capacity (IEC) of this block copolymer P1 was 2.1 meq / g. Next, block copolymer P1 was dissolved in NMP and pressure filtered using a 1 μm polypropylene filter to obtain coating liquid p1 (polymer electrolyte concentration 13% by mass). The viscosity of coating liquid p1 was 1,300 mPa s.

[0196] [Coating liquid p2]: Coating liquid containing polyether ketone random copolymer P2. 129 g of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane synthesized in Synthesis Example 1, 93 g of 4,4'-biphenol (Sigma-Aldrich Japan (same) reagent), and 422 g (1.0 mol) of disodium-3,3'-disulfonate-4,4'-difluorobenzophenone synthesized in Synthesis Example 2 were placed in a 5 L reaction vessel equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap. The atmosphere in the vessel was replaced with nitrogen, and then 3,000 g of NMP, 450 g of toluene, and 232 g of 18-crown-6 (Fujifilm Wako Pure Chemical Industries, Ltd. reagent) were added. After confirming that all of the monomers had dissolved, 304 g of potassium carbonate (Sigma-Aldrich Japan (same) reagent) was added, and the mixture was dehydrated at 160°C under reflux. Thereafter, the temperature was raised to remove toluene, and desalting polycondensation was carried out for 1 hour at 200° C. The resulting random copolymer P2 had a weight average molecular weight of 320,000 and an ion exchange capacity (IEC) of 2.1.

[0197] Next, NMP was added to dilute the polymerization stock solution so that the viscosity became 500 mPa·s. An angle rotor RA-800 was installed in a Kubota Manufacturing Co., Ltd. inverter compact high-speed refrigerated centrifuge (model number 6930), and the polymerization stock solution was directly centrifuged at 25°C for 30 minutes at a centrifugal force of 20,000 G. The precipitated solids (cake) and the supernatant liquid (coating liquid) were clearly separated, and the supernatant liquid was recovered. Next, the mixture was distilled under reduced pressure at 80°C while stirring, and NMP was removed until the polymer concentration became 14% by mass. This was then filtered under pressure using a 5 μm polyethylene filter to obtain coating liquid p2. The viscosity of this coating liquid p2 was 1,000 mPa·s.

[0198] [Coating liquid p3]: Coating liquid containing polyarylene block copolymer P3 represented by the following general formula (G10) 540 mL of dried N,N-dimethylacetamide (DMAc) was added under nitrogen to a mixture of 135.0 g (0.336 mol) of neopentyl 3-(2,5-dichlorobenzoyl)benzenesulfonate, 40.7 g (5.6 mmol) of the nonionic oligomer represented by general formula (G6) synthesized in Synthesis Example 6, 6.71 g (16.8 mmol) of 2,5-dichloro-4′-(1-imidazolyl)benzophenone, 6.71 g (10.3 mmol) of bis(triphenylphosphine)nickel dichloride, 35.9 g (0.137 mol) of triphenylphosphine, 1.54 g (10.3 mmol) of sodium iodide, and 53.7 g (0.821 mol) of zinc.

[0199] The reaction system was heated with stirring (finally heated to 79°C) and reacted for 3 hours. An increase in viscosity in the system was observed during the reaction. The polymerization reaction solution was diluted with 730 mL of DMAc, stirred for 30 minutes, and filtered using Celite as a filter aid.

[0200] The filtrate was concentrated using an evaporator, and 43.8 g (0.505 mol) of lithium bromide was added to the filtrate. The mixture was allowed to react at an internal temperature of 110°C for 7 hours under a nitrogen atmosphere. After the reaction, the mixture was cooled to room temperature and poured into 4 L of acetone to coagulate. The coagulated product was collected by filtration, air-dried, pulverized in a mixer, and washed with 1,500 mL of 1N hydrochloric acid while stirring. After filtration, the product was washed with ion-exchanged water until the pH of the washings reached 5 or higher. The mixture was then dried overnight at 80°C to obtain 23.0 g of polyarylene-based block copolymer P3. This polyarylene-based block copolymer P3 had a weight-average molecular weight of 190,000 and an ion exchange capacity (IEC) of 2.0. The obtained polyarylene-based block copolymer P3 was dissolved in a mixed organic solvent of N-methyl-2-pyrrolidone / methanol = 30 / 70 (mass%) to a concentration of 0.1 g / g, to obtain coating solution p3. The viscosity of the coating liquid p3 was 1,200 mPa·s.

[0201]

[0202] [Coating Liquid p4]: Coating Liquid Containing Polyethersulfone-Based Block Copolymer P4 0.23 g of the block copolymer precursor b1 obtained in Synthesis Example 7 was weighed out and added to a mixed solution of 0.16 g of lithium bromide monohydrate and 8 mL of NMP, followed by a reaction at 120°C for 24 hours. The reaction mixture was poured into 80 mL of 6 mol / L hydrochloric acid and stirred for 1 hour. The precipitated solid was separated by filtration. The separated solid was dried to obtain a gray-white block copolymer P4 composed of a segment represented by the general formula (G9) and a segment represented by the following chemical formula (G11). The resulting polyethersulfone-based block copolymer P4 had a weight-average molecular weight of 190,000 and an ion exchange capacity (IEC) of 2.0. The resulting polyethersulfone-based block copolymer P4 was dissolved in an organic solvent of N-methyl-2-pyrrolidone / methanol = 30 / 70 (mass %) to a concentration of 0.1 g / g, to obtain coating liquid p4. The viscosity of the coating liquid p4 was 1,300 mPa·s.

[0203]

[0204] [Preparation of Coating Liquid for Layer (B)] Coating liquids b1 to b12 were prepared in the following manner.

[0205] [Coating liquid b1] Particles: 10 parts by mass of carbon black ("VULCAN" (registered trademark) XC72 manufactured by Cabot Corporation: average particle size 30 nm) Polymer: 8 parts by mass, in terms of solids, of ""Nafion" (registered trademark) product number D2020" manufactured by Chemours Corporation, a fluorinated polymer electrolyte Solvent: a mixed solvent of water and 1-propyl alcohol in a mass ratio of 4:6 The above particles and polymer were dispersed in the solvent using a bead mill to prepare coating liquid b1 having a solids concentration of 10% by mass. The particle concentration in coating liquid b1 is 56% by mass.

[0206] [Preparation of Coating Liquids b2 to b12] Coating Liquids b2 to b9 were prepared in the same manner as Coating Liquid b1, except that the particle concentration was changed as shown in Table 1. Coating Liquid b10 was prepared in the same manner as Coating Liquid b1, except that no particles were used. Coating Liquid b11 was prepared in the same manner as Coating Liquid b1, except that the particles were changed from carbon black to cerium (IV) oxide (average particle diameter 50 nm) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Coating Liquid b12 was prepared in the same manner as Coating Liquid b9, except that the polymer was changed to PVDF (polyvinylidene fluoride) manufactured by Solvey.

[0207]

[0208] [Preparation of Anode Catalyst Layer Transfer Sheet 1] The following anode catalyst layer coating solution was applied to a commercially available polytetrafluoroethylene film so that the iridium content was 1.0 mg / cm ２ The resulting mixture was cast and dried at 100° C. for 4 hours to prepare an anode catalyst layer transfer sheet 1.

[0209] <Coating liquid for anode catalyst layer> Particles (IrO ２ The coating liquid contained 10 parts by mass of catalyst Elyst Ir75 0480 (Ir content 75%), 1.2 parts by mass, calculated as solid content, of a fluorine-based polymer electrolyte ("Nafion" (registered trademark) product number D2020, manufactured by Chemours Inc.), and a solvent (a mixed solvent of water and 1-propyl alcohol in a mass ratio of 4:6), and had a solid content concentration of 30% by mass.

[0210] [Preparation of Cathode Catalyst Layer Transfer Sheet 1] The following cathode catalyst layer coating liquid was applied to a commercially available polytetrafluoroethylene film so that the platinum amount was 0.3 mg / cm ２ The mixture was cast and dried at 100° C. for 4 hours to prepare a cathode catalyst layer transfer sheet 1.

[0211] <Coating Liquid for Cathode Catalyst Layer> This coating liquid contains 10 parts by mass of catalyst particles (10 parts by mass of platinum catalyst-supported carbon particles TEC10E50E (platinum support rate 50% by mass) manufactured by Tanaka Kikinzoku Kogyo K.K.), 5 parts by mass, converted into solid content, of a fluorine-based polymer electrolyte ("Nafion" (registered trademark) product number D2020 manufactured by Chemours Inc.), and a solvent (a mixed solvent of water and 1-propyl alcohol in a mass ratio of 1:1), and has a solid content concentration of 10% by mass.

[0212] Example 1 An electrolyte membrane was prepared as follows.

[0213] [Preparation of Layer (A)] A PET film "Lumirror" (registered trademark) 125T60 manufactured by Toray Industries, Inc. was adhered to a SUS plate and fixed using "Kapton" (registered trademark) tape. Coating liquid p1 was cast onto the PET film and then dried at 100°C for 4 hours to obtain a film-like membrane. This film-like membrane was immersed in a 10% by mass aqueous sulfuric acid solution at 80°C for 24 hours to undergo proton substitution and deprotection reactions, and then thoroughly washed by immersion in a large excess of pure water for 24 hours to obtain Layer (A) (film thickness 100 μm).

[0214] [Lamination of Layer (B)] Coating Liquid b1 was cast onto Layer (A) and dried at 100° C. for 4 hours, thereby laminating Layer (B-1) (film thickness: 3 μm) on Layer (A). Subsequently, Coating Liquid b10 was cast onto Layer (B-1) and dried at 100° C. for 4 hours, thereby laminating Layer (B-2) (film thickness: 3 μm).

[0215] Examples 2 to 13 Electrolyte membranes were prepared in the same manner as in Example 1, except that the coating liquid for the (B-1) layer and the coating liquid for the (B-2) layer were changed as shown in Table 2.

[0216] Examples 14 to 16 Electrolyte membranes were prepared in the same manner as in Example 1, except that the coating liquid p1 for the (A) layer was changed as shown in Table 2.

[0217] Comparative Example 1 An electrolyte membrane was obtained in the same manner as in Example 1, except that the (B) layer was not laminated.

[0218] Comparative Example 2 An (A) layer was prepared in the same manner as in Example 1, and Coating Liquid b10 was cast onto the (A) layer, followed by drying at 100°C for 4 hours to laminate a single (B) layer (thickness: 6 µm) consisting of only a polymer on the (A) layer, thereby preparing an electrolyte membrane. In Table 2, the composition of the single (B) layer is entered in the column for (B-1) layer.

[0219] Comparative Example 3 An (A) layer was prepared in the same manner as in Example 1, and Coating Liquid b7 was cast onto the (A) layer, followed by drying at 100°C for 4 hours to laminate a single (B) layer (thickness: 6 µm) containing particles and a polymer on the (A) layer, thereby preparing an electrolyte membrane. In Table 2, the composition of the single (B) layer is entered in the column for (B-1) layer.

[0220] Example 17 A CCM was produced in the following manner: [Production of Layer (A)] Layer (A) was produced in the same manner as in Example 1.

[0221] [Preparation of Transfer Sheet Having Laminated (B) Layer and Anode Catalyst Layer] Coating Liquid b10 was cast onto the catalyst layer of the aforementioned anode catalyst layer transfer sheet 1, and the resulting mixture was dried at 100°C for 4 hours, thereby laminating a (B-2) layer (film thickness 3 μm). Subsequently, Coating Liquid b1 was cast onto the (B-2) layer, and the resulting mixture was dried at 100°C for 4 hours, thereby laminating a (B-1) layer (film thickness 3 μm). This catalyst layer / (B) layer transfer sheet was a catalyst layer / (B-2) layer / (B-1) layer transfer sheet in which the catalyst layer and the (B) layer ((B-2) layer / (B-1) layer) were sequentially laminated on a transfer substrate, and was used to prepare a CCM.

[0222] [Preparation of CCM] The (B-1) layer and the (A) layer of the transfer sheet prepared above were overlapped so that they faced each other and were in contact with each other, and then hot-pressed at 150°C and 5 MPa for 3 minutes. After the temperature was lowered to 40°C or less while still under pressure, the pressure was released, and a CCM was obtained.

[0223] [Example 18] A CCM was produced in the following manner: [Production of a laminate of an (A) layer and a (B-1) layer] Coating liquid b1 was cast onto an (A) layer produced in the same manner as in Example 1, and the resultant was dried at 100°C for 4 hours, thereby obtaining a laminate in which a (B-1) layer (thickness: 3 µm) was laminated on the (A) layer.

[0224] [Preparation of catalyst layer / (B-2) layer transfer sheet] Coating Liquid b10 was cast onto the catalyst layer of the aforementioned anode catalyst layer transfer sheet, followed by drying for 4 hours at 100° C. This catalyst layer / (B-2) layer transfer sheet had the catalyst layer and the (B-2) layer sequentially laminated on the transfer substrate, and was used to prepare a CCM.

[0225] [Preparation of CCM] The (B-1) layer of the laminate prepared above and the (B-2) layer of the transfer sheet were overlapped so that they faced each other and were in contact with each other, and then hot-pressed at 150°C and 5 MPa for 3 minutes. After the temperature was lowered to 40°C or less while still under pressure, the pressure was released, and a CCM was obtained.

[0226] [Evaluation] The anode catalyst layer transfer sheet 1 was placed on the (B) layer side of the electrolyte membranes produced in Examples 1 to 16 and Comparative Examples 1 to 3 above, and hot-pressed at 150°C and 5 MPa for 3 minutes. The temperature was lowered to 40°C or below while still under pressure, and the pressure was then released to obtain CCMs. These CCMs and the CCMs produced in Examples 17 and 18 were evaluated for adhesion between the electrolyte membrane and the catalyst layer in accordance with the above-mentioned "(4) Evaluation of interlayer adhesion (peelability)." The results are shown in Table 2. In Table 2, the particles "CB" represent carbon black, and "Ce" represents cerium oxide.

[0227]

[0228] Example 21 An electrolyte membrane was prepared as follows.

[0229] [Preparation of Layer (A)] Layer (A) was prepared in the same manner as in Example 1.

[0230] [Lamination of Layer (B)] Coating Liquid b1 was cast onto Layer (A) and dried at 100° C. for 4 hours to form Layer (B-1) (film thickness: 5 μm) on Layer (A). Subsequently, Coating Liquid b4 was cast onto Layer (B-1) and dried at 100° C. for 4 hours to form Layer (B-2) (film thickness: 5 μm).

[0231] Example 22 An electrolyte membrane was produced in the same manner as in Example 21, except that the coating liquid for the (B-2) layer was changed to coating liquid b5.

[0232] Comparative Example 21 An electrolyte membrane was obtained in the same manner as in Example 21, except that the (B) layer was not laminated.

[0233] [Evaluation] The cathode catalyst layer transfer sheet 1 was placed on the (B) layer side of the electrolyte membranes prepared in Examples 21 and 22 and Comparative Example 21, and hot-pressed at 150°C and 5 MPa for 3 minutes. The temperature was lowered to 40°C or below while still under pressure, and the pressure was then released to obtain CCMs. The adhesion between the electrolyte membrane and the catalyst layer of these CCMs was evaluated in accordance with the above-mentioned "(4) Evaluation of interlayer adhesion (peelability)." The results are shown in Table 3. In Table 3, the particle "CB" represents carbon black.

[0234]

[0235] Example 31 An electrolyte membrane was prepared as follows.

[0236] [Preparation of Layer (A)] Layer (A) was prepared in the same manner as in Example 1.

[0237] [Preparation of (B) Layer Transfer Sheet D1] Coating Liquid b10 was cast onto a commercially available polytetrafluoroethylene film, followed by drying for 4 hours at 100° C. to form a (B-2) layer (3 μm thick). Further, Coating Liquid b1 was cast onto the (B-2) layer, followed by drying for 4 hours at 100° C. to form a (B-1) layer (3 μm thick), thereby obtaining a (B) Layer Transfer Sheet D1.

[0238] [Preparation of (B) Layer Transfer Sheet D2] Coating Liquid b4 was cast onto a commercially available polytetrafluoroethylene film, followed by drying for 4 hours at 100° C. to form a (B-2) layer (5 μm thick). Coating Liquid b1 was then cast onto the (B-2) layer, followed by drying for 4 hours at 100° C. to form a (B-1) layer (5 μm thick), thereby obtaining a (B) Layer Transfer Sheet D2.

[0239] [Lamination of (B) Layer] The (A) layer was peeled from the PET film, and the (B-1) layer side of the (B) layer transfer sheet D1 was superimposed on one surface (anode side) of the (A) layer, and the (B-1) layer side of the (B) layer transfer sheet D2 was superimposed on the other surface (cathode side) of the (A) layer. The resulting mixture was then hot-pressed at 150°C and 5 MPa for 3 minutes, and the temperature was lowered to 40°C or lower while still pressurized, and the pressure was then released to produce an electrolyte membrane.

[0240] Example 32 Preparation of (B) layer transfer sheet D3 A (B) layer transfer sheet D3 was prepared in the same manner as in the preparation of the (B) layer transfer sheet D1, except that the (B-1) layer coating liquid b1 was changed to coating liquid b11.

[0241] [Lamination of (B) Layer] The (A) layer was peeled from the PET film, and the (B-1) layer side of the (B) layer transfer sheet D3 was superimposed on one surface (anode side) of the (A) layer, and the (B-1) layer side of the (B) layer transfer sheet D2 was superimposed on the other surface (cathode side) of the (A) layer. The resulting mixture was then hot-pressed at 150°C and 5 MPa for 3 minutes, and the temperature was lowered to 40°C or lower while still pressurized, and the pressure was then released to produce an electrolyte membrane.

[0242] Example 33 Preparation of (B) layer transfer sheet D4 A (B) layer transfer sheet D4 was prepared in the same manner as in the preparation of the (B) layer transfer sheet D1, except that the (B-2) layer coating liquid b10 was changed to coating liquid b12.

[0243] [Lamination of (B) Layer] The (A) layer was peeled from the PET film, and the (B-1) layer side of the (B) layer transfer sheet D4 was superimposed on one surface (anode side) of the (A) layer, and the (B-1) layer side of the (B) layer transfer sheet D2 was superimposed on the other surface (cathode side) of the (A) layer. The resulting mixture was then hot-pressed at 150°C and 5 MPa for 3 minutes, and the temperature was lowered to 40°C or lower while still pressurized, and the pressure was then released to produce an electrolyte membrane.

[0244] [Examples 34 to 36] Electrolyte membranes were produced in the same manner as in Example 31, except that the coating liquid p1 for the (A) layer was changed as shown in Table 4. [Comparative Example 31] An electrolyte membrane was produced in the same manner as in Example 31, except that the (B) layer was not laminated.

[0245] [Evaluation] An anode catalyst layer transfer sheet 1 was superimposed on the anode side (B) layer of the electrolyte membrane produced in Examples 31 to 36 and Comparative Example 31, and a cathode catalyst layer transfer sheet 1 was superimposed on the cathode side (B) layer of the electrolyte membrane. The sheets were then hot-pressed at 150°C and 5 MPa for 3 minutes, and the temperature was lowered to 40°C or less while still under pressure, after which the pressure was released to obtain a CCM. The durability of this CCM was evaluated in accordance with the above-mentioned "(5) Evaluation of durability." The results are shown in Table 4.

[0246]

[0247] Example 41 A CCM was prepared as follows.

[0248] [Preparation of Laminate 1] Layer (A) was prepared in the same manner as in Example 1, and layer (B-1) was further formed on layer (A) in the same manner as in Example 1 to obtain laminate 1.

[0249] [Preparation of Transfer Sheet 2 Having (B-2) Layer and Anode Catalyst Layer Laminated] Coating Liquid b10 was cast onto the catalyst layer of the above-described anode catalyst layer transfer sheet 1, and dried at 100°C for 4 hours, thereby laminating a (B-2) layer (film thickness: 3 µm).

[0250] [Preparation of Transfer Sheet 3 Having Layer (C) and Cathode Catalyst Layer Laminated] The following Coating Liquid c1 was cast onto the catalyst layer of the above-described cathode catalyst layer transfer sheet 1, and dried at 100°C for 4 hours to laminate Layer (C) (film thickness: 8 µm).

[0251] <Coating Liquid c1> Particles: 10 parts by mass of carbon black ("VULCAN" (registered trademark) XC72 manufactured by Cabot Corporation: average particle size 30 nm) Polymer: 9 parts by mass, in terms of solids, of ""Nafion" (registered trademark) product number D2020" manufactured by Chemours Corporation, a fluorinated polymer electrolyte Solvent: a mixed solvent of water and 1-propyl alcohol in a mass ratio of 4:6 The above particles and polymer were dispersed in the solvent using a bead mill to prepare coating liquid c1 having a solids concentration of 10% by mass. The particle concentration in coating liquid c1 is 53% by mass.

[0252] [Preparation of CCM] The PET film was peeled off from the laminate 1 to obtain a laminate film of (A) layer / (B-1) layer. The above-mentioned transfer sheet 2 was superimposed on the (B-1) layer side of this laminate film, and the above-mentioned transfer sheet 3 was superimposed on the (A layer) side, and the laminate was subjected to a heat press at 150°C and 5 MPa for 3 minutes. After the temperature was lowered to 40°C or less while still under pressure, the pressure was released to obtain a CCM. The layer structure of this CCM was "anode catalyst layer / (B) layer / (A) layer / (C) layer / cathode catalyst layer."

[0253] [Evaluation Results] The CCM obtained above was evaluated for adhesion and durability in accordance with the above "(3) Evaluation of interlayer adhesion (peelability)" and "(4) Evaluation of durability." As a result, the adhesion between the electrolyte membrane and the anode catalyst layer was rated "A," the adhesion between the electrolyte membrane and the cathode catalyst layer was rated "B," and the voltage rise rate was 2%.

[0254] [Example 51] [Preparation of anode catalyst layer transfer sheet 2] The following coating liquid for an anode catalyst layer was applied to a commercially available polytetrafluoroethylene film so that the amount of iridium was 1.0 mg / cm ２ The resulting mixture was cast and dried at 100° C. for 4 hours to prepare an anode catalyst layer transfer sheet 2.

[0255] <Coating Liquid for Anode Catalyst Layer> This coating liquid contains 10 parts by mass, in terms of elemental iridium, of commercially available iridium oxide, 2 parts by mass, in terms of elemental platinum, of commercially available platinum black, 2.5 parts by mass, in terms of solids, of a fluorine-based polymer electrolyte (Nafion (registered trademark) manufactured by Chemours Inc., product number D2020), and a solvent (a mixed solvent of water and 1-propyl alcohol in a mass ratio of 4:6), and has a solids concentration of 30% by mass.

[0256] [Preparation of CCM] A catalyst layer-equipped electrolyte membrane was prepared in the same manner as in the catalyst layer-equipped electrolyte membrane CCM used in the evaluation of Example 31, except that the anode catalyst layer transfer sheet 1 was replaced with the above-prepared anode catalyst layer transfer sheet 2. The layer structure of this CCM was "anode catalyst layer / (B) layer / (A) layer / (B) layer / cathode catalyst layer".

[0257] Example 52 A CCM was produced in the same manner as in Example 41, except that anode catalyst layer transfer sheet 1 was replaced with the above-prepared anode catalyst layer transfer sheet 2. The layer structure of this CCM was "anode catalyst layer / (B) layer / (A) layer / (C) layer / cathode catalyst layer."

[0258] [Comparative Example 51] A CCM was prepared in the same manner as in the CCM used in the evaluation of Comparative Example 31, except that the anode catalyst layer transfer sheet 1 was replaced with the above-prepared anode catalyst layer transfer sheet 2. The layer structure of this CCM was "anode catalyst layer / layer (A) / cathode catalyst layer".

[0259] Example 53 A CCM was produced in the same manner as in Example 51, except that the anode catalyst layer transfer sheet 3 was changed to the following.

[0260] [Preparation of Anode Catalyst Layer Transfer Sheet 3] The following coating liquid for an anode catalyst layer was applied to a commercially available polytetrafluoroethylene film so that the amount of iridium was 1.0 mg / cm ２ The resulting mixture was cast and dried at 100° C. for 4 hours to prepare an anode catalyst layer transfer sheet 3.

[0261] <Coating Liquid for Anode Catalyst Layer> This coating liquid contains 10 parts by mass, in terms of elemental iridium, of commercially available iridium oxide, 2 parts by mass, in terms of elemental palladium, of commercially available palladium black, 2.5 parts by mass, in terms of solids, of a fluorine-based polymer electrolyte ("Nafion" (registered trademark), product number D2020, manufactured by Chemours Inc.), and a solvent (a mixed solvent of water and 1-propyl alcohol in a mass ratio of 4:6), and has a solids concentration of 30% by mass.

[0262] [Example 61] The following evaluation was carried out using the CCM used in the evaluation of Example 31. This was designated Example 61. The layer structure of this CCM was "anode catalyst layer / (B) layer / (A) layer / (B) layer / cathode catalyst layer."

[0263] [Evaluation] The CCMs obtained in Examples 51 to 53 and 61 and Comparative Example 51 were evaluated in accordance with the above-mentioned "(4) Evaluation of interlayer bondability (peeling property)," "(5) Evaluation of durability," and "(6) Measurement of hydrogen gas concentration in oxygen gas." The results are shown in Table 5. In the table, "CCM" represents a catalyst-layered electrolyte membrane, "An" represents an anode catalyst layer, "Ca" represents a cathode catalyst layer, "A" represents the (A) layer, "B" represents the (B) layer, "C" represents the (C) layer, "Ir" represents iridium, "Pt" represents platinum, and "Pd" represents palladium.

[0264]

[0265] It can be seen that the hydrogen gas concentration in the oxygen gas generated at the anode is reduced by the anode catalyst layer containing iridium and precious metals other than iridium (platinum, palladium) as catalysts. It can also be seen that the hydrogen gas concentration is significantly reduced by the combination of the anode catalyst layer containing iridium and precious metals other than iridium (platinum, palladium) as catalysts and the fluoropolymer electrolyte (B) layer being disposed on the anode catalyst layer side.

[0266] 1, 2 Electrolyte membrane 10 (A) layer 20, 20a, 20b (B) layer 21, 21a, 21b Interface region of the (B) layer on the (A) layer side 22, 22a, 22b Interface region of the (B) layer on the opposite side to the (A) layer 30, 40 Catalyst layer 50 Anode catalyst layer 60 Cathode catalyst layer 100, 200 Electrolyte membrane with catalyst layer

Claims

1. An electrolyte membrane comprising a layer (A) containing a polymer electrolyte and a layer (B) on at least one surface of layer (A), wherein the particle concentration (Y1) defined below in the interface region of layer (B) with layer (A) is higher than the particle concentration (Y2) defined below in the interface region of layer (B) opposite to layer (A), An electrolyte membrane having a thickness of 30 μm or more and 250 μm or less for layer (A), and a thickness of 0.5 μm or more and 20 μm or less for layer (B); The particle concentration (Y1) and the particle concentration (Y2) are the ratio of the mass of particles present in the interface region to the total mass of solids present in the interface region.

2. The electrolyte membrane according to claim 1, wherein the ratio (Y2 / Y1) of the particle concentration (Y1) to the particle concentration (Y2) is 0.95 or less.

3. The electrolyte membrane according to claim 1, wherein the particle concentration (Y1) is 45% by mass or more, and the particle concentration (Y2) is less than 45% by mass.

4. The electrolyte membrane according to claim 1, wherein the (B) layer further comprises a polymer.

5. The electrolyte membrane according to claim 1, wherein the particles include carbon particles.

6. The electrolyte membrane according to claim 4, wherein the polymer is a non-electrolyte or electrolyte fluorine-based polymer.

7. The electrolyte membrane according to claim 1, wherein the (B) layer is composed of at least two layers, and the particle concentration of the layer adjacent to the (A) layer is the highest.

8. The electrolyte membrane according to claim 1, wherein the (B) layer consists of two layers, a (B-1) layer and a (B-2) layer, the layer adjacent to the (A) layer being designated as the (B-1) layer and the layer on the opposite side of the (A) layer being designated as the (B-2) layer.

9. The electrolyte membrane according to claim 8, wherein, when both the (B-1) layer and the (B-2) layer contain particles, both the (B-1) layer and the (B-2) layer contain particles of the same type.

10. The electrolyte membrane according to claim 1, wherein the (B) layer is provided on both sides of the (A) layer.

11. A catalyst-layered electrolyte membrane comprising a catalyst layer on one or both sides of the electrolyte membrane according to any one of claims 1 to 10.

12. The electrolyte membrane with a catalyst layer according to claim 11, wherein the polymer electrolyte contained in the (A) layer of the electrolyte membrane and the polymer electrolyte contained in the catalyst layer are of different types.

13. The electrolyte membrane with a catalyst layer according to claim 11, wherein the (B) layer of the electrolyte membrane contains the same polymer as the catalyst layer.

14. The electrolyte membrane with a catalyst layer according to claim 11, wherein the (A) layer contains a hydrocarbon polymer electrolyte, the catalyst layer contains a fluorine polymer electrolyte, and the (B) layer contains a nonionic or ionic fluorine polymer.

15. A membrane electrode assembly comprising an electrolyte membrane with a catalyst layer as described in claim 11.

16. A water electrolysis apparatus comprising the membrane electrode assembly described in claim 15.

17. A transfer sheet used in the production of an electrolyte membrane with a catalyst layer according to claim 11, A catalyst layer / (B) layer transfer sheet is provided, wherein a catalyst layer and a (B) layer are sequentially laminated on a transfer substrate, and the particle concentration (Y1) in the interface region of the (B) layer opposite the catalyst layer is higher than the particle concentration (Y2) in the interface region of the (B) layer with the catalyst layer.

18. The catalyst layer / (B) layer transfer sheet according to claim 17, wherein the (B) layer is composed of two layers, a (B-1) layer and a (B-2) layer, and the catalyst layer, the (B-2) layer and the (B-1) layer are sequentially laminated on the transfer substrate.

19. The catalyst layer / (B) layer transfer sheet according to claim 17, wherein the (B) layer is composed of two layers, a (B-1) layer and a (B-2) layer, and the catalyst layer and the (B-2) layer are sequentially laminated on the transfer substrate.

20. A method for producing an electrolyte membrane comprising an (A) layer containing a polymer electrolyte and a (B) layer on at least one side of the (A) layer, and an electrolyte membrane with a catalyst layer comprising a catalyst layer provided on one or both sides of the electrolyte membrane, A step of stacking the (B) layer on the (A) layer to obtain the electrolyte membrane according to any one of claims 1 to 10, A step of preparing a catalyst layer transfer sheet by laminating the catalyst layer onto a transfer substrate, A step of bringing the surface on which the (B) layer of the electrolyte membrane is laminated and the surface on which the catalyst layer of the catalyst layer transfer sheet is laminated into opposing contact and heating and pressing them together, A method for producing an electrolyte membrane with a catalyst layer having the following characteristics.

21. A method for producing an electrolyte membrane comprising an (A) layer containing a polymer electrolyte and a (B) layer on at least one side of the (A) layer, and an electrolyte membrane with a catalyst layer comprising a catalyst layer provided on one or both sides of the electrolyte membrane, (A) A process to obtain the layer, A step of sequentially laminating a catalyst layer and a (B) layer onto a transfer substrate to obtain a catalyst layer / (B) layer transfer sheet according to claim 17, A step of heating and pressing the surface on which the (B) layer of the catalyst layer / (B) layer transfer sheet is laminated against at least one surface of the (A) layer, A method for producing an electrolyte membrane with a catalyst layer having the following characteristics.

22. A method for producing an electrolyte membrane comprising an (A) layer containing a polymer electrolyte and a (B) layer on at least one side of the (A) layer, and an electrolyte membrane with a catalyst layer comprising a catalyst layer provided on one or both sides of the electrolyte membrane, The aforementioned layer (B) consists of two layers, of which the layer adjacent to layer (A) is designated as layer (B-1), and the layer on the opposite side of layer (A) is designated as layer (B-2). The process of obtaining a laminate by stacking layer (B-1) on layer (A), A step of sequentially laminating a catalyst layer and a (B-2) layer onto a transfer substrate to obtain a catalyst layer / (B-2) layer transfer sheet according to claim 19, A step of bringing the surface on which the (B-1) layer of the laminate is laminated and the surface on which the (B-2) layer of the transfer sheet is laminated into opposing contact and heating and pressing them, It has, The particle concentration (Y1) in the interface region of layer (B) with layer (A) is higher than the particle concentration (Y2) in the interface region of layer (B) on the opposite side of layer (A). A method for manufacturing an electrolyte membrane with a catalyst layer.