Electrolyte membrane and catalyst-coated electrolyte membrane

Abstract

The present disclosure provides an electrolyte membrane (anion exchange membrane) and a catalyst-coated electrolyte membrane having low voltage, exceptional water electrolysis performance, and exceptional mechanical strength in an anion-exchange-membrane-type water electrolysis test.　The problem is solved by an electrolyte membrane that satisfies relationship (1), where Xdry (MPa) is the breaking stress under dry conditions, and Xwet (MPa) is the breaking stress under wet conditions. [Relationship 1]: −0.15 ≤ (Xwet − Xdry) / Xdry ≤ 0.1 (1)

Description

Electrolyte membranes and catalyst-coated electrolyte membranes

[0001] The present disclosure relates to an electrolyte membrane and a catalyst-coated electrolyte membrane used for water electrolysis, more specifically to an electrolyte membrane used as an anion exchange membrane (AEM) and a catalyst-coated electrolyte membrane obtained by coating the electrolyte membrane with a catalyst layer.

[0002] Electrolyte membranes are used in various fuel cells, such as polymer electrolyte fuel cells and solid alkaline fuel cells, as well as in various electrolysis technologies, including water electrolysis. These electrolyte membranes are required to have excellent ionic conductivity and durability for long-term use.

[0003] Among water electrolysis methods, anion exchange membrane water electrolysis (AEMWE) has been proposed as an alternative technology to cation exchange membrane water electrolysis and alkaline water electrolysis, and has attracted attention in recent years. The AEMWE uses an anion exchange membrane (AEM) as a membrane separating an anode chamber and a cathode chamber (see, for example, Patent Document 1), and pure water or an alkaline aqueous solution is supplied to the anode chamber as an anolyte. Pure water or an alkaline aqueous solution can be supplied to the cathode chamber as an anolyte, but a dry cathode electrolytic cell in which no anolyte is supplied to the cathode chamber is also possible. In this dry cathode electrolytic cell, water permeates from the anode chamber into the cathode chamber through the anion exchange membrane, thereby supplying water to the cathode chamber. In the cathode chamber, hydrogen gas and hydroxide ions are produced from the water by a cathode reaction.

[0004] As described above, the electrolyte membrane used in the AEMWE method is used in pure water or an alkaline aqueous solution, and therefore durability in a wet state is an important property in addition to durability in a dry state.

[0005] For example, Patent Document 1 discloses the configuration of a water electrolyzer used in the AEMWE process. When water electrolysis is performed with this configuration, excessive pressure is applied from the anode chamber to the cathode chamber, causing a load on the catalyst-coated membrane (hereinafter referred to as CCM). Therefore, the CCM is required to have high durability. A CCM generally has a layered structure of an anode catalyst layer, an electrolyte membrane, and a cathode catalyst layer, with an ionomer layer disposed between each catalyst layer and the electrolyte membrane. Furthermore, unlike cation exchange membrane water electrolysis and alkaline water electrolysis, the AEMWE process continuously changes the state of the catalyst layer or ionomer layer and the electrolyte membrane from a liquid to a gas. This increases the mechanical strength required of the CCM.

[0006] Generally, when attempting to achieve excellent ionic conductivity, the electrolyte membrane becomes more susceptible to swelling with water, resulting in reduced strength in the wet state. On the other hand, when attempting to ensure sufficient strength in the wet state, the membrane tends to become brittle in the dry state. For this reason, the electrolyte membrane used in the AEWME method is required to have excellent strength in both the dry and wet states and excellent ionic conductivity.

[0007] International Publication No. 2022 / 244805

[0008] In view of the above circumstances, an object of the present disclosure is to provide an electrolyte membrane and a catalyst-coated electrolyte membrane that function as an anion exchange membrane at a low voltage, have excellent water electrolysis performance, and are excellent in mechanical strength in an anion exchange membrane water electrolysis test.

[0009] As a result of extensive research, the present inventors have focused on the tensile breaking stress of the electrolyte membrane and found that the above-mentioned problems can be solved. That is, the present invention relates to the following [1] to

[11] . [1]: An electrolyte membrane that satisfies the following mathematical formula (1), where Xdry (MPa) is the breaking stress under dry conditions and Xwet (MPa) is the breaking stress under wet conditions. [Math 1]: -0.15≦(Xwet−Xdry) / Xdry≦0.1 (1) [2]: An electrolyte membrane according to [1] that satisfies the following mathematical formula (2), where Ydry (%) is the elongation rate under dry conditions and Ywet (%) is the elongation rate under wet conditions. [Math 2]: -0.30≦(Ywet−Ydry) / Ywet≦0.1 (2) [3]: An electrolyte membrane according to [1] or [2], in which Xdry is 60 MPa or more. [4]: The electrolyte membrane according to [2] or [3], wherein the Ydry is 50% or more. [5]: The electrolyte membrane according to any one of [1] to [4], which has a polymer having an anion exchange group as a constituent element. [6]: The electrolyte membrane according to [5], which further has a polymer having no ion conductivity. [7]: The electrolyte membrane according to any one of [1] to [6], which has an ion exchange capacity of 0.8 to 1.5 mmol / g. [8]: The electrolyte membrane according to any one of [1] to [7], which has a pore-filling structure. [9]: The electrolyte membrane according to any one of [1] to [8], which contains a polymer having a structural unit represented by the following general formula (1): However, Ar １ is an aromatic group having an ion exchange group or a group in which aromatic rings having an ion exchange group are linked via a single bond, and there are a plurality of Ar １ may be the same or different, and Ar ２ is an aromatic group having no ion-exchange group, or a group in which two or more aromatic rings having no ion-exchange group are linked via a single bond or a spiro atom, and a plurality of Ar ２ may be the same or different, Ar １ and an aromatic ring having Ar ２

[10] : The electrolyte membrane according to any one of [1] to [9], which functions as an anion exchange membrane.

[11] : A catalyst-coated electrolyte membrane having the electrolyte membrane according to any one of [1] to

[10] , and a catalyst layer.

[0010] The present invention has the excellent effect of providing an electrolyte membrane and a catalyst-coated electrolyte membrane that function as an anion exchange membrane at a low voltage, have excellent water electrolysis performance, and are excellent in mechanical strength in an anion exchange membrane water electrolysis test.

[0011] 1 is a diagram showing an example of a layer structure of a catalyst coated electrolyte membrane of the present embodiment, and FIG. 2 is a diagram showing another example of a layer structure of a catalyst coated electrolyte membrane of the present embodiment.

[0012] An example of an embodiment to which the present disclosure is applied will be described below. The present disclosure is not limited to this embodiment, and other embodiments are also included as long as they are consistent with the spirit of the present disclosure. In this specification, numerical ranges indicated by "to" include the stated numerical values. Furthermore, the specified numerical values ​​are values ​​obtained by the methods described in the embodiments or examples. Furthermore, various components can be used independently, either alone or in combination of two or more, unless otherwise noted.

[0013] The catalyst coated electrolyte membrane of the present disclosure has an electrolyte membrane that functions as an anion exchange membrane and a catalyst layer. In this specification, the term "electrolyte membrane" simply refers to an electrolyte membrane that functions as an anion exchange membrane, and is distinguished from a "catalyst coated electrolyte membrane" in which a catalyst layer is formed as a coating layer on this electrolyte membrane.

[0014] FIG. 1 shows an example of the layer structure of a catalyst coated electrolyte membrane of this embodiment. As shown in the figure, the catalyst coated electrolyte membrane 100 has an electrolyte membrane 11, a first catalyst layer 12 formed on a first main surface of the electrolyte membrane 11, and a second catalyst layer 13 formed on a second main surface of the electrolyte membrane 11. Note that the catalyst coated electrolyte membrane may have a catalyst layer formed on only one main surface of the electrolyte membrane 11. In other words, the catalyst coated electrolyte membrane of the present disclosure only needs to have a catalyst layer formed on at least one side of the electrolyte membrane. The electrolyte membrane and the catalyst coated electrolyte membrane will be described below.

[0015] <Electrolyte Membrane (Anion Exchange Membrane)> The electrolyte membrane of the present disclosure (hereinafter also referred to as the present electrolyte membrane) satisfies the relationship of the following mathematical formula (1), where Xdry (MPa) is the breaking stress under dry conditions and Xwet (MPa) is the breaking stress under wet conditions. [Mathematical Formula 1] −0.15≦(Xwet−Xdry) / Xdry≦0.1 (1) By satisfying the relationship of mathematical formula (1), an electrolyte membrane with extremely high durability can be obtained, which exhibits low voltage, excellent water electrolysis performance, and excellent mechanical strength in an anion exchange membrane water electrolysis test, and is therefore suitable for use in the AEMWE method without any problems.

[0016] In this disclosure, an electrolyte membrane is a membrane composed of a polymer having at least an ion exchange group. Here, "polymer" includes "copolymer" unless otherwise specified. "Ion exchange group" refers to a functional group that has dissociation properties and is capable of ion exchange. Anion exchange groups are preferred as "ion exchange groups." Suitable examples of anion exchange groups include substituents having cations, such as groups in which heteroatoms are cationized. Specific examples include quaternary ammonium salts, imidazolium salts, pyridinium salts, and phosphonium salts.

[0017] <Regarding Breaking Stress> In the present disclosure, the breaking stress of an electrolyte membrane is a value measured according to the following measurement method. Measurement Method: 1) Preparation of Test Specimen When the electrolyte membrane is composed of a polymer having ion exchange groups, the polymer having ion exchange groups is coated and dried to form a self-supporting membrane, and the resulting film is cut into a 40 mm x 10 mm size (hereinafter the same) to prepare a test specimen. The electrolyte membrane may include a substrate film. In this case, a polymer without ion conductivity is preferably used as the substrate film. When a substrate film is used, a polymer having ion exchange groups is dissolved in a solvent to prepare a solution, the solution is dripped onto the substrate film, and the solvent is removed to prepare a film with a thickness of approximately 10 to 40 μm. The resulting film is cut into a 40 mm x 10 mm size to prepare a test specimen. Note that the substrate film is preferably a polyolefin film such as polyethylene, polypropylene, or polytetrafluoroethylene (PTFE), or an amide film such as polyimide or polyamide, with a polyolefin film being more preferred. The electrolyte membrane of the present disclosure may have a pore-filling structure. In this case, a porous film (also called a porous substrate) is used as the substrate film, and a solution of a polymer having ion exchange groups dissolved in a solvent is penetrated into the substrate by a method such as dipping, spraying, spin coating, or bar coding, and then the substrate is dried and cut to the same size as above to prepare a test piece.

[0018] 2) Breaking Stress Measurement A uniaxial tensile test was performed on a test piece of the electrolyte membrane prepared using an EZ-SX (Shimadzu Corporation) at 25°C and 40% RH at 0.3 m / min, and the breaking stress was calculated from the cross-sectional area of ​​the fractured surface. Note that if the strain of the test piece is large and exceeds the measurement limit, a test piece of 40 mm x 5 mm may be used.

[0019] <Regarding Dry Conditions> Dry conditions, which are measurement conditions for Xdry, are measurement conditions in which the film prepared in the above "1) Preparation of test piece" is measured as is.

[0020] <Wet Conditions> The wet conditions under which Xwet is measured are as follows: the film prepared in "1) Preparation of test piece" above is immersed in pure water at 80°C for 1 hour to swell it, cooled to room temperature, removed from the pure water, and water droplets adhering to the surface are wiped off, followed by measurement.

[0021] As shown in the above formula (1), the electrolyte membrane of the present disclosure has (Xwet-Xdry) / Xdry of -0.15 or more and 0.1 or less. More preferable upper limits of (Xwet-Xdry) / Xdry are 0.08, 0.06, 0.04, and 0.02, respectively, and particularly preferably 0. More preferable lower limits are -0.14, -0.13, -0.12, -0.11, and -0.10, respectively, and particularly preferably -0.09. Therefore, (Xwet-Xdry) / Xdry is particularly preferably -0.09 or more and 0 or less.

[0022] Furthermore, Xdry is preferably 60 MPa or more. The lower limit of the breaking stress is, in order of more preferable values, 80 MPa, 90 MPa, 100 MPa, and 120 MPa, and particularly preferably 125 MPa. The upper limit of the breaking stress is determined in relation to other components and cannot be discussed in detail, but may be, for example, about 180 MPa, and 160 MPa, 150 MPa, and 145 MPa are more preferable. Therefore, a particularly preferable breaking stress is 125 MPa or more and 145 MPa or less.

[0023] The electrolyte membrane of the present disclosure has a specific relationship between Ydry (%) and Ywet (%), where Ydry is the elongation percentage under dry conditions and Ywet is the elongation percentage under wet conditions. [Regarding Ydry and Ywet] <Regarding Elongation Percentage> Based on the distance until the membrane broke in the above-mentioned breaking stress measurement, the elongation percentage was calculated using the following calculation formula (3): Elongation Percentage (%) = Distance until electrolyte membrane breaks / Sample Length × 100 (3) The dry and wet conditions are the same as those used in the above-mentioned breaking stress measurement. Furthermore, the "distance until electrolyte membrane breaks" refers to the length stretched from the start of the test until the membrane breaks, i.e., the amount of deformation, and the elongation percentage refers to the ratio of the amount of deformation to the initial length of the membrane. For this electrolyte membrane, (Ywet - Ydry) / Ydry is greater than or equal to -0.30 and less than or equal to 0.10, as shown in the above-mentioned formula (2). More preferred values ​​for the upper limit of (Ywet-Ydry) / Ydry are 0, -0.02, -0.04, and -0.06, respectively, and particularly preferably -0.08. More preferred values ​​for the lower limit are -0.28, -0.26, -0.24, -0.22, -0.20, -0.18, -0.16, and -0.14, and particularly preferably -0.12. Therefore, particularly preferred values ​​for (Ywet-Ydry) / Ydry are -0.12 or more and -0.08 or less.

[0024] Furthermore, Ydry is preferably 50% or more. The lower limit of this elongation is, in order of preference, 55%, 60%, 65%, and 70%, with 75% being particularly preferred. The upper limit cannot be discussed in general because it is determined in relation to other components, but it may be, for example, around 100%, with 95% being particularly preferred. Therefore, a particularly preferred elongation is 75% or more and 95% or less.

[0025] [Polymer] The present electrolyte membrane preferably has a polymer having an anion exchange group as a constituent element. Furthermore, it is more preferable to combine it with a polymer that does not have ion conductivity. The polymer used in the present electrolyte membrane is preferably a polyarylene polymer. By using a polyarylene polymer, an electrolyte membrane with excellent chemical durability can be obtained. Furthermore, in order to impart excellent ion conductivity to the polyarylene polymer, a polymer having a structural unit represented by the following general formula (1) (hereinafter also referred to as polymer (A)) is preferred. Furthermore, from the viewpoint of increasing ion conductivity, a combination of polymer (A) with a substrate film having a pore filling structure is more preferred. However, Ar １ is an aromatic group having an ion exchange group or a group in which aromatic rings having an ion exchange group are linked via a single bond, and there are a plurality of Ar １ may be the same or different. ２ is an aromatic group having no ion-exchange group, or a group in which two or more aromatic rings having no ion-exchange group are linked via a single bond or a spiro atom, and a plurality of Ar ２ may be the same or different. １ and an aromatic ring having Ar ２ is linked to the aromatic ring of the formula (I) via a single bond.

[0026] The polymer (A) is a polymer having two or more structural units of the general formula (1), and the polymer (A) is a polymer having an ion exchange group, Ar １ and Ar having no ion exchange group ２ Ar has a structure in which １ and the aromatic group Ar ２ The aromatic groups contained in the polymer (A) are bonded to each other by single bonds to form the main chain. The polymer (A) has an ether oxygen (—O—), sulfonyl (—S(═O) ２ -), and carbonyl (-C(=O)-) skeletons are not present, and the compound has excellent chemical durability, particularly alkali durability. The aromatic ring here refers to the aromatic ring that constitutes the main chain, and the aromatic ring that constitutes the main chain may further have an aromatic ring as a substituent. The aromatic ring that constitutes the main chain and the aromatic ring that is present as a substituent (side chain) are distinguished.

[0027] When proton conductivity is to be imparted to the polymer (A), the ion exchange group is preferably an acidic group, and the acidic group is, among others, a sulfonic acid group (—SO ３ H group), phosphate group (-H ２ P.O. ４ A sulfonic acid group is more preferred. The H in the acidic group may be dissociated or may be substituted with an alkali metal ion, alkaline earth metal ion, or the like.

[0028] Furthermore, when anion conductivity is imparted to the polymer (A), the ion exchange group is preferably a quaternary ammonium group or an imidazolium group, and more preferably a quaternary ammonium group. Furthermore, from the viewpoint of alkali durability, the quaternary ammonium group is preferably a quaternary alkylammonium group. The quaternary alkylammonium group also includes groups in which alkyl groups bonded to nitrogen atoms are bonded to each other to form a ring structure, and may be, for example, an azaadamantyl group or a quinuclidinium group. Preferred specific examples of the quaternary ammonium group include groups represented by the following formulae (e-1) to (e-8). Preferred specific examples of the imidazolium group include groups represented by the following formulae (f-1) to (f-3), with a group represented by the following formula (f-2) or (f-3) being more preferred.

[0029] In the formula, R ｅ are each independently a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms; R ｆ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an aromatic group which may have a substituent, and A － is a monovalent or divalent or more anion, and R ｅ or R ｆ If there are multiple R ｅ or R ｆ may be the same or different. １ The bond bonded to the aromatic ring that constitutes the main chain is shown.

[0030] The above Rｅ Specific examples of the alkyl group in the above R include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and a cyclohexyl group. ｆ Specific examples of the alkyl group in R include a methyl group, an ethyl group, a propyl group, and a butyl group. ｆ The aromatic group in the formula (I) may be a phenyl group, and the substituent of the phenyl group may be an alkyl group having 1 to 6 carbon atoms.

[0031] Above A － The anion is preferably an inorganic anion, and a chloride ion (Cl － ), bromide ion (Br － ), iodide ion (I － ), bicarbonate ion (HCO ３ － ), carbonate ions (CO ３ ２－ ), hydroxide ions (OH － ), sulfate ions (SO ４ ２－ ), chlorate ion (ClO ３ － ), nitrate ions (NO ３ － ), cyanide ion (CN － ), sulfite ion (HSO ３ － ), bromate ion (BrO ３ ― ), fluorine ion (F － Among these, hydroxide ions (OH － ), bromide ion (Br － ), bromate ion (BrO ３ ― ), chloride ions (Cl － ), bicarbonate ion (HCO ３ － ), carbonate ions (CO ３ ２－ ), and particularly preferably hydroxide ion (OH － ), bromide ion (Br － ), chloride ions (Cl － ), bicarbonate ion (HCO ３－ ), carbonate ions (CO ３ ２－ )

[0032] The ion exchange group is Ar １ The ion-exchange group may be directly bonded to the aromatic ring constituting the main chain, or may further have a linking group and be bonded to the aromatic ring constituting the main chain via the linking group. Here, the linking group represents an organic group that connects the acidic group, quaternary ammonium group, or imidazolium group of the ion-exchange group to the aromatic ring constituting the main chain. As the organic group, a linear or branched alkylene group is preferred, and a linear alkylene group is particularly preferred. The number of carbon atoms of the alkylene group can be appropriately adjusted depending on the physical properties required of the polymer (A). For example, by setting the number of carbon atoms of the alkylene group to 20 or less, preferably 16 or less, and more preferably 12 or less, the ion-exchange group capacity of the polymer (A) is increased. On the other hand, by setting the number of carbon atoms of the alkylene group to 2 or more, preferably 4 or more, and more preferably 6 or more, excellent solubility and swelling resistance are achieved, making it easier to fill the porous substrate with the polymer (A). Ar １ The number of ion exchange groups per aromatic ring constituting the main chain in the polymer may be one or more, and from the viewpoint of ion conductivity and polymer stability, one to two are preferred.

[0033] Ar １ The aromatic ring constituting the main chain in the above may be a benzene ring, a condensed ring such as a naphthalene ring or an anthracene ring, or a heterocycle containing an oxygen atom (O), a nitrogen atom (N), or a sulfur atom (S) (e.g., thiophene). Furthermore, these aromatic rings may be linked by a single bond. Examples of structures in which multiple rings are linked by a single bond include biphenyl, terphenyl, and fluorene.

[0034] Ar １In addition to the ion-exchange group, the aromatic ring constituting the main chain in may further have a substituent other than the ion-exchange group. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms which may have a substituent, a phenyl group which may have a substituent, and a halogeno group. Specific examples of the alkyl group include alkyl groups such as a methyl group, an ethyl group, a propyl group, an n-butyl group, a tert-butyl group, a pentyl group, a hexyl group, and an octyl group, which may have a phenyl group, a halogeno group, or the like as a substituent. Furthermore, examples of the substituent that the phenyl group may have include an alkyl group having 1 to 6 carbon atoms and a halogeno group. Furthermore, examples of the halogeno group include a fluoro group, a chloro group, a bromo group, and an iodo group.

[0035] From the viewpoint of excellent mechanical strength, chemical durability, and ionic conductivity, the Ar １ Among them, it is preferable that Ar is a group represented by any one of the following formulas (a-1) to (a-10). １ may be the same as or different from each other.

[0036] However, R ａ are each independently a hydrogen atom, an ion exchange group, or a substituent not having an ion exchange group, and a plurality of R ａ may be the same or different, R ａ At least one of the groups is an ion exchange group. ２ indicates the bond bonded to

[0037] Ar ２ The aromatic ring constituting the main chain of Ar １ and groups linked via a spiro atom. ２ The aromatic ring in may have a substituent other than the anion exchange group. １ The substituents other than the ion exchange group in Ar are the same as those in Ar. ２In the formula (c1), examples of the group in which two or more aromatic rings are linked via a spiro atom include the group represented by the following formula (c1). In addition, examples of the group in which two or more aromatic rings are linked via a single bond include the groups represented by the following formulas (c2) to (c4). The wavy line indicates that Ar １ From the viewpoint of the polymer filling property into the porous substrate, Ar ２ Preferably, does not have a spiro atom.

[0038] However, R Ｃ are each independently a hydrogen atom, a halogen group, or an organic group.

[0039] The weight average molecular weight of the polymer (A) can be appropriately adjusted based on factors such as chemical durability and ease of filling into pores, and can be, for example, in the range of 10,000 to 1,000,000. From the viewpoint of chemical durability, it is preferably 30,000 or more, more preferably 100,000 or more, even more preferably 200,000 or more, and particularly preferably 220,000 or more. In particular, when the porous substrate is a polyolefin-based porous substrate, the polymer (A) is easily filled into the pores even if its weight average molecular weight is 100,000 or more. The upper limit of the weight average molecular weight may be about 2,000,000, but is preferably 300,000, more preferably 250,000, particularly preferably 240,000, and most preferably 230,000. The weight average molecular weight is a polystyrene-equivalent value measured by GPC (gel permeation chromatography).

[0040] The molecular weight distribution of the polymer (A) is preferably 2.0 or more and 10.0 or less. Generally, the molecular weight distribution is expressed as the Mw / Mn value using the weight average molecular weight (Mw) and the number average molecular weight (Mn). The upper limit of the molecular weight distribution (Mw / Mn) of the polymer (A) is more preferably 9.0, 8.0, 7.0, 6.0, 5.0, 4.9, 4.8, 4.7, 4.5, 4.0, 3.9, 3.8, and 3.7, in that order, and particularly preferably 3.6. The lower limit is more preferably 2.5, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, and 3.4, in that order, and particularly preferably 3.5. Therefore, the molecular weight distribution (Mw / Mn) is most preferably 3.5 or more and 3.6 or less.

[0041] The polymer (A) may consist solely of the structural unit represented by general formula (1) (also referred to as structural unit (1)), or may contain other structural units. Examples of other structural units include Ar in the structural unit (1). １ In addition, other structures that may be generated during synthesis may also be included.

[0042] Among these, the following polymers (A1) to (A4) are preferred as the polymer (A). From the viewpoint of the polymer's packing property into the porous substrate, polymer (A2), polymer (A3), or polymer (A4) is preferred, polymer (A2) or polymer (A3) is preferred, and polymer (A3) is more preferred from the viewpoint of the polymer's packing property, mechanical strength, and chemical durability. These polymers are described in detail below.

[0043] Polymer (A1) The polymer (A1) has a repeating unit represented by the following general formula (1-1).

[0044] However, R １ ~R １０ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group, and Ar １ is the same as in the formula (1), and the preferred forms are also the same.

[0045] R １ ~R １０Examples of the alkyl group having 1 to 4 carbon atoms in R include a methyl group, an ethyl group, a propyl group, and a tert-butyl group. １ and R １０ Preferably, at least one of R is an alkyl group. １ and R １０ is more preferably an alkyl group, and further preferably R １ and R １０ More preferably, R is a tert-butyl group. １ and R １０ By having a bulky substituent on at least one of R, aggregation of the polymer due to π-π stacking or the like is suppressed, and the solubility in a solvent is improved. ２ ~R ９ are each independently preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.

[0046] The polymer (A1) is a polymer having an anion exchange group, Ar １ and spirobifluorene skeletons are alternately repeated. In the polymer (A1), each element constituting the main chain skeleton belongs to an aromatic ring or is a spiro atom having no hydrogen atoms, and the main chain skeleton does not have an ether bond, so decomposition in the presence of alkali or radicals is suppressed, resulting in excellent chemical durability. Furthermore, the spirobifluorene skeleton has a structure in which two fluorenes are twisted at approximately right angles via the spiro atom, and the fluorene skeletons constitute the main chain, resulting in the entire main chain having numerous bends. This reduces the planarity of the main chain, inhibiting π-π stacking, resulting in excellent solubility in solvents and excellent handleability when filling a porous substrate.

[0047] The method for synthesizing the polymer (A1) is not particularly limited, but a suitable example is the method shown in Scheme A1 below.

[0048] In Scheme A1, R ａ represents an anion exchange group, R ｂ represents R in general formula (1-1). １ and R１０ represents a substituent corresponding to:

[0049] In the example of Scheme A1 above, the desired substituent R ｂ A compound (C) having a brominated spirobifluorene skeleton is synthesized from a compound (B) having the following formula (Steps (i) to (vii)). Separately, a bromide (D) having a desired aromatic ring (a benzene ring in the example of Scheme A1) is reacted with bis(pinacolato)diborane to form a compound represented by the formula (1-1): １ (Step (viii)) Compound (C) and compound (E) are polymerized, and then a desired anion exchange group is introduced to obtain a polymer represented by general formula (1-1) (Steps (ix) to (xi)). The reaction conditions for each of the above steps may be determined by referring to known reactions.

[0050] Polymer (A2) The polymer (A2) has a repeating unit represented by the following general formula (1-2).

[0051] However, R ａ is a group having an anion exchange group, and Ar ２ is the same as in the general formula (1).

[0052] The polymer (A2) is a polymer having two or more of the structural units (1-2) and is a compound whose main chain is wholly aromatic. Because of this structure, the polymer (A2) has excellent resistance to alkalis, radicals, and the like.

[0053] Ar in polymer (A2) ２ Among these, a phenylene group, a biphenylene group, or a terphenylene group is preferable, and a p-phenylene group (formula (Ar-1) below), a 4,4′-biphenylene group (formula (Ar-2) below), or a 4,4″-terphenylene group (formula (Ar-3) below) is more preferable.

[0054] where R is Ar ２ is a substituent that may be present, and r is an integer of 0 to 4, and a plurality of R's and r's may be the same or different.

[0055] Ar ２ When Ar is a p-phenylene group, a 4,4'-biphenylene group, or a 4,4''-terphenylene group, the polymer (A2) tends to have a zigzag main chain structure as shown in the following formula. ２ is a p-phenylene group, the same applies to a 4,4'-biphenylene group or a 4,4''-terphenylene group. As shown in the following formula, the polymer (A2) tends to have a zigzag main chain structure, and furthermore, each R ａ is likely to be located outside the folded back of the backbone. Therefore, intramolecular aggregation due to the folded back of the main chain is suppressed. As a result, the polymer can be used to form an electrolyte membrane with excellent ion conductivity.

[0056]

[0057] Group R having an anion exchange group in polymer (A2) ａ is, among others, the following formula (R ａ -1) is preferred.

[0058] However, R ｂ２ is an anion exchange group, and p2 is an integer of 1 or more and 20 or less. The wavy line indicates a bond to the benzene ring.

[0059] The above formula (R ａ In the group represented by {(R ｂ２ The number of carbon atoms from the aryl group to the quaternary carbon) minus 1 may be appropriately adjusted within the range of 1 to 20. Among these, 1 to 15 is preferred, 1 to 12 is more preferred, and 1 to 6 is even more preferred.

[0060] The method for synthesizing the polymer (A2) is not particularly limited, but a suitable example is the method shown in Scheme A2 below.

[0061] However, X, X １represents a halogen atom, Ar ２ , and p2 are as described above. １ The halogen atom is preferably Br.

[0062] In the example of Scheme A2, first, compound (H) and the desired Ar ２ Compound (I) having the formula (I) is prepared, and compound (H) and compound (I) are polymerized to obtain a polymer having a structural unit represented by (J). Next, a desired anion exchange group is introduced into polymer (J) to obtain polymer (A2). In the above scheme A2, a quaternary ammonium group is introduced, but other ionic functional groups can also be introduced in a similar manner. The reaction conditions for each of the above steps may be determined with reference to known reactions.

[0063] Polymer (A3) The polymer (A3) is a repeating unit represented by the general formula (1) in which Ar ２ has a partial structure represented by the following formula (2) at both ends. ２ is a divalent group containing an aromatic ring having a fluoro group (-F) at the α-position of the terminal carbon atom. ２ The end of Ar １ The wavy line indicates the carbon atom bonded to Ar. １ The dotted lines indicate that part of the aromatic ring is omitted.

[0064]

[0065] The polymer (A3) is a polymer having an anion exchange group, Ar １ and Ar having a partial structure (2) containing a fluoro group (—F). ２ The main chain has a structure in which Ar is alternately arranged. １ and Ar ２ Each of these has an aromatic group, and is excellent in chemical durability against alkalis, radicals, etc. The polymer (A3) also has an Ar group having an ion exchange group linked to the side chain terminal via an alkyl chain. １ and Ar having no ion exchange group ２are arranged alternately. Because of this structure, the compound has excellent solubility in solvents and ionic conductivity. In addition, the compound having the partial structure (2) is highly reactive with the compound represented by formula (4) described below, making it possible to produce a polymer with a higher molecular weight. By using this high-molecular-weight polymer, it is also possible to form a film with better durability.

[0066] Ar ２ For example, as in formula (b-1) described later, one ring structure (e.g., a benzene ring) may have two partial structures (2), or as in formula (b-2) described later, one C—F bond may constitute two partial structures (2). Furthermore, in the case of the chain polycyclic hydrocarbon, each of the two ring structures of the chain polycyclic hydrocarbon may have one partial structure (2), and these rings may be linked directly or via the linking group, or one of the multiple ring structures may have two partial structures (2). ２ Preferably, does not have a spiro atom.

[0067] The polymer (A3) is preferably selected from the group consisting of Ar and Ar-based polymers, because it is possible to form an electrolyte membrane having excellent ionic conductivity, membrane formability, chemical durability, and membrane strength. ２ is preferably one or more selected from the following formulas (d1) to (d9). １ This shows the bond between .

[0068] However, R ｄ are each independently a hydrogen atom, a halogen group, or an organic group.

[0069] The above R ｄ Examples of the halogeno group in R include a fluoro group, a chloro group, a bromo group, and an iodo group, and among these, a fluoro group is preferred. ｄ The organic group in the formula (I) may be, for example, a linear or branched alkyl group having 1 to 20 carbon atoms (not including the carbon number of the substituent) which may have a substituent (for example, a halogeno group).

[0070] From the viewpoint of ease of production, the above Ar ２The following formulas (d10) to (d14) are preferred. １ This shows the bond between .

[0071]

[0072] The method for synthesizing the polymer (A3) is not particularly limited, but a suitable example is the method shown in Scheme A3 below.

[0073] However, X １ are each independently Br or I, and Ar ３ is an aromatic group having a functional group selected from a halogeno group, a sulfonate group, a phosphate group, a carboxylate group, an imidazole group, and an amino group; Ar ２ is the same as that in polymer (A3).

[0074] X in compound (4) １ and Ar of compound (5). ２ Since the hydrogen atoms of the following partial structure (5a) have excellent reactivity, it is possible to relatively easily synthesize an ion-conductive polymer having a high molecular weight (for example, a weight-average molecular weight of 30,000 or more, preferably 100,000 or more).

[0075]

[0076] In the above scheme A3, first, the desired Ar ３ and a compound (4) having the desired Ar ２ Then, these compounds are reacted with a Pd complex, a ligand, a carboxylic acid (RCO ２ A polymer having the structural unit (3) is obtained by reacting the compound (II) in the presence of methyl group (H) and a base at 80 to 140° C. for 1 to 48 hours.

[0077] Next, the desired ion exchange group is introduced into the polymer having the structural unit (3), thereby obtaining the polymer (A3). In this way, the polymer (A3) can be easily produced with an extremely small number of synthesis steps by using the compound (4) and the compound (5) as raw materials.

[0078] Polymer (A4) The polymer (A4) has a repeating unit represented by the following general formula (1-4).

[0079] However, the ring Ar １１ and ring Ar １２ is a ring fused to a benzene ring, and is a fused ring of three or more rings having aromatic properties as a whole, and Ar １ is the same as in the general formula (1).

[0080] The polymer (A4) is a polymer having an anion exchange group, Ar １ and Ar consisting of three or more fused rings. ２ In general, polymers containing many ion exchange groups tend to swell easily, but polymer (A4) has a structure in which Ar １ and Ar ２ and are alternately repeated, and condensed rings of three or more rings are π-π stacked, thereby providing excellent swelling resistance.

[0081] Ring Ar １１ and ring Ar １２ is an aromatic ring which may have a heteroatom. Examples of the heteroatom include N (nitrogen atom), O (oxygen atom), and S (sulfur atom). １１ and ring Ar １２ From the viewpoint of swelling resistance, the fused ring containing Ar is preferably a fused ring of 3 or more rings. On the other hand, from the viewpoint of increasing the ion exchange capacity of the polymer (A4), a fused ring of 5 or less rings is preferred, and a fused ring of 4 or less rings is more preferred. Preferred specific examples of the fused ring include the following. The wavy line indicates that Ar １ The hydrogen atom may be substituted with a group that does not have an anion exchange group.

[0082]

[0083] The polymer (A4) is preferably synthesized by preparing a precursor (1-5) having a repeating unit represented by the following general formula (1-5), filling the porous substrate with the precursor, and then eliminating the substituent (TL).

[0084] where LT is a group represented by general formula (LT1) to (LT3), and R １１ are each independently an alkyl group having 1 to 6 carbon atoms, and R １２ is an alkyl group having 1 to 6 carbon atoms or a phenyl group, and Ar １ , Ar １１ , Ar １２ is the same as in the general formula (1-4). １１ and R １２ The alkyl group having 1 to 6 carbon atoms in the formula (I) may be either a linear or branched alkyl group. Specific examples include a methyl group, an ethyl group, a propyl group, an n-butyl group, a tert-butyl group, a pentyl group, and a hexyl group.

[0085] As mentioned above, polymer (A4) has excellent swelling resistance. Therefore, it is difficult to dissolve in various organic solvents, which causes problems with poor handling during processing. The precursor has a bulky substituent (TL) represented by one of the general formulas (LT1) to (LT3) introduced into the site corresponding to the fused ring of polymer (A4). The substituent inhibits π-π stacking of the hydrophobic portion of precursor (1-5), improving its solubility in various organic solvents. Therefore, the precursor has excellent handleability and can be easily filled into a porous substrate. The substituent (TL) can be removed by heating or light irradiation.

[0086] The method for synthesizing the precursor is not particularly limited, but a preferred specific example is the method shown in Scheme A4 below.

[0087]

[0088] An example of each step of the above scheme A4 will be described. Step (i): A toluene solution of the above compound (1) is prepared, and diethyl azodicarboxylate (DEAD) is added and heated to reflux to obtain the above compound (2). Step (ii): Separately, an N,N-dimethylformamide (DMF) solution of the above compound (3) is prepared, and bis(pinacolato)diborane, potassium acetate (KOAc), and [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloride (Pd(dppf)Cl ２ Step (iii): To the toluene solution of the obtained compound (2) and the compound (4), tripotassium phosphate (K ３ P.O. ４ ) and tetrakis(triphenylphosphine)palladium (Pd(PPH ３ ) ４ ) and heated to 100°C to polymerize, thereby obtaining the compound (5). Step (iv): The obtained compound (5), N-bromosuccinimide (NBS), and azobisisobutyronitrile (AIBN) are added to chlorobenzene, mixed, and heated to 110°C to obtain the compound (6). Step (v): The obtained compound (6) is heated to 50°C in a DMF / THF (tetrahydrofuran) mixed solvent to obtain the precursor represented by the chemical formula (7).

[0089] [Pore-filling membrane] The electrolyte membrane used in the present invention is preferably used as a pore-filling membrane in which a porous substrate is used as a substrate film and the polymer is filled. This configuration can impart mechanical strength to a polyarylene polymer with excellent chemical durability. The porous substrate is a substrate having pores capable of retaining a polymer. In order to improve ionic conductivity, it is preferable that at least some of the pores of the porous substrate form through-holes. In terms of imparting mechanical strength, the substrate is preferably in the form of a nonwoven fabric or a porous film (porous substrate), and more preferably in the form of a porous film. The porosity (= void volume / bulk volume × 100 (%)) of the porous substrate is preferably 30 to 95%, more preferably 40 to 80%, and even more preferably 45 to 70%, in order to achieve both mechanical strength and ionic conductivity. The film thickness of the porous substrate is preferably 5 to 200 μm, more preferably 7 to 100 μm, and even more preferably 10 to 50 μm, from the viewpoint of achieving both mechanical strength and ionic conductivity. Furthermore, the pore size of the porous substrate is preferably 10 to 10,000 nm, more preferably 10 to 1,000 nm, in terms of average diameter, from the viewpoint of filling and retaining the polyarylene polymer and mechanical strength. The material of the porous substrate is preferably a polyolefin-based porous substrate from the viewpoint of chemical durability, particularly stability in alkali. The use of a polyolefin-based porous substrate also has the advantage of being easily filled with polyarylene polymers, particularly high-molecular-weight polyarylene polymers having a weight-average molecular weight of 100,000 or more. Among the polyolefin-based porous substrates, polyethylene porous substrates, polypropylene porous substrates, and polytetrafluoroethylene porous substrates are preferred from the viewpoint of mechanical strength and chemical resistance. Among the polyethylene porous substrates, ultra-high molecular weight polyethylene (e.g., weight-average molecular weight of 1,000,000 or more) porous substrates are preferred.

[0090] An example of a method for producing a pore-filling film is a method of applying a polyarylene polymer to a porous substrate and drying it. Examples of methods for applying a polyarylene polymer to a porous substrate include preparing a solution of the polyarylene polymer and using methods such as dipping, spraying, spin coating, and bar coding. A pore-filling film can be obtained by permeating the polyarylene polymer solution into the porous substrate and then drying it. It should be noted that the filling of the porous substrate with the polyarylene polymer can be confirmed, for example, by Raman analysis.

[0091] <Catalyst-Coated Electrolyte Membrane> As described above, the catalyst-coated electrolyte membrane of the present disclosure has a catalyst layer coated on at least one side of the electrolyte membrane. For example, a catalyst-coated electrolyte membrane used for water electrolysis has an anode catalyst disposed on one side of the electrolyte membrane as an anode and a cathode catalyst disposed on the other side as a cathode. The anode catalyst is preferably a metal or a metal alloy. The metal or metal alloy can be appropriately selected from known metals and metal alloys, and examples thereof include platinum, cobalt, nickel, palladium, iron, silver, gold, copper, iridium, molybdenum, rhodium, chromium, tungsten, manganese, ruthenium, metal compounds thereof, metal oxides, and alloys containing two or more of these metals. The cathode catalyst is preferably a metal or a metal alloy. The metal or metal alloy can be appropriately selected from known metals and includes, for example, platinum, cobalt, nickel, palladium, iron, silver, gold, copper, iridium, molybdenum, rhodium, chromium, tungsten, manganese, ruthenium, compounds of these metals, metal oxides, and alloys containing two or more of these metals.

[0092] The catalyst layer is preferably configured such that the metal is dispersed in an ionomer from the viewpoint of adhesion to the electrolyte polymer and an increase in the reaction specific surface area. The ionomer may be a sulfonated fluoropolymer, such as a perfluorinated sulfonic acid (PFSA) ionomer or a partially fluorinated polymer. ＴＭ(Chemours Company), Aquivion® (Solvay Specialty Polymers), Flemion ＴＭ (Asahi Glass Group) and Aciplex ＴＭ PFSA selected from Asahi Kasei Chemicals Corporation is commercially available.

[0093] <Fabrication of Catalyst-Coated Electrolyte Membrane> The catalyst-coated electrolyte membrane of the present disclosure is obtained by forming a catalyst layer on at least one side, more preferably both sides, of the present electrolyte membrane. Examples of methods for forming the catalyst layer include pulse spray coating, ultrasonic spray coating, die coater coating, bar coater coating, and electrode transfer coating. Note that, depending on the coating method, a drying step may be included. The catalyst-coated electrolyte membrane of the present disclosure has anion exchange water electrolysis performance. The anion exchange membrane water electrolysis performance is evaluated in an electrochemical cell in which a catalyst layer formed by dispersing a metal powder having hydrogen generating ability in an ionomer is provided on the cathode side of an electrolyte membrane having anion exchange groups, and a catalyst layer formed by dispersing a metal powder having oxygen generating ability in an ionomer is provided on the anode side. An alkaline solution is passed through this electrochemical cell, and OH is generated by the alkaline solution. － This refers to the ability to electrolyze water without a large increase in voltage when a current is passed from a power source through an electrochemical cell containing an ion-exchanged electrolyte membrane and an ionomer. Specifically, platinum-supported carbon or platinum-ruthenium alloy-supported carbon is generally used as the hydrogen generating catalyst, while iridium oxide is generally used as the oxygen generating catalyst. When 1 mol / L potassium hydroxide is used as the alkaline solution and the electrochemical cell is heated to 80°C, the electrolysis performance is 1 A / cm. ２The voltage should be 2.0 V or less when the ion exchange capacity is 1.7 V to 1.8 V, and particularly preferably 1.78 V or less. The ion exchange capacity is an index representing the amount of ions that can be adsorbed by an ion exchange resin. The higher this value, the better the ionic conductivity, but the higher the water content, which tends to cause the electrolyte membrane to swell and reduce the gas barrier properties. Therefore, the ion exchange capacity is preferably 0.8 mmol / g to 2.0 mmol / g, and the lower limit of the ion exchange capacity is more preferably 1.0 mmol / g, even more preferably 1.2 mmol / g, and even more preferably 1.3 mmol / g. The upper limit of the ion exchange capacity is more preferably 1.9 mmol / g, even more preferably 1.7 mmol / g, and even more preferably 1.5 mmol / g.

[0094] The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited to these examples and can be modified as appropriate without departing from the spirit of the invention.

[0095] [Synthesis of Compound (1-1)] In a four-neck flask, n-tetrabutylammonium chloride (3.04 g), 1,10-dichlorodecane (1097 mmol), and 2,7-dibromofluorene (109.7 mmol) were added to a four-neck flask with a syringe and stirred under nitrogen. The mixture was then allowed to react at 90°C under nitrogen for 90 minutes, after which the resulting reaction mixture was cooled to room temperature (25°C). The organic phase in the cooled reaction mixture was extracted with toluene (200 mL) in a separatory funnel and washed with 1 M hydrochloric acid (50 mL) and saturated brine (200 mL × 2). The toluene in the resulting organic phase was removed using an evaporator, and unreacted 1,10-dichlorodecane was removed under reduced pressure at 180°C. The resulting residue was applied to a silica gel column (developing solvent: hexane) to obtain the following compound (1-1) (68.7 mmol).

[0096]

[0097] [Synthesis of Compound (1-2)] Compound (1-1) (57.7 mmol) and 1,3,5-trimethylbenzene (159 mL) were added to a separable flask and stirred while bubbling with nitrogen (20 mL / min) for 30 min. Next, cesium carbonate (173 mmol), pivalic acid (57.7 mmol), tris(2-methoxyphenyl)phosphine (407 mg), and Pd ２ (dba) ３ (291 mg) and 1,2,4,5-tetrafluorobenzene (57.7 mmol) were added and stirred. This mixture was reacted under nitrogen at room temperature (25°C) for 15 minutes, then at 98°C for 8 hours, and then at 75°C for 75 minutes. 1M hydrochloric acid (100 mL) and toluene (600 mL) were added to the resulting reaction product (solids), and the mixture was stirred at 60°C for 30 minutes. After that, insoluble matter was removed by vacuum filtration, and the organic phase was extracted using a separatory funnel. The extracted organic phase was washed with 1M hydrochloric acid and saturated saline, and the liquid in the resulting organic phase was removed using an evaporator and dried. The resulting residue was dissolved in toluene and reprecipitated in hexane / methanol = 3 / 1. The resulting precipitate was filtered to remove the liquid. The resulting solids were dried in vacuo to obtain compound (1-2) with a molecular weight distribution of 4.88. The results of GPC showed that the peak end of this compound (1-2) was 14.025 min, confirming that the amount of low molecular weight compounds was reduced.

[0098]

[0099] [Synthesis of Compound (1-3)] Compound (1-2) (2.07 g) was dissolved in 3-methoxy-N,N-dimethylpropanamide (25 mL). To the resulting solution, 25% by mass trimethylamine methanol solution (10 mL) was added, and the mixture was stirred at 100°C for 9 hours. After that, the mixture was cooled to room temperature (25°C), and the solution was reprecipitated in toluene. The resulting precipitate was filtered to remove the liquid. The resulting solid was dried in vacuum to obtain compound (1-3) (2.29 g). As described above, compound (1-2) was synthesized so as to minimize the content of low molecular weight compounds, and therefore, compound (1-3) is presumed to similarly contain few low molecular weight compounds.

[0100]

[0101] [Example 1: Production of electrolyte membrane 1] A porous substrate was prepared by heating polyethylene (Hipore NH815, manufactured by Asahi Kasei Corporation) having submicron-sized pores, and a solution of the compound represented by Chemical Formula 1-3 dissolved in a solvent was added dropwise thereto. The solvent was dried at 80°C to fill the pores with the compound, thereby obtaining an electrolyte membrane 1 having a thickness of 18 μm.

[0102] <Measurement of Breaking Stress and Elongation of Electrolyte Membrane> The electrolyte membrane 1 was cut into a 40 mm x 10 mm piece and subjected to a uniaxial tensile test at 0.3 m / min using an EZ-SX (Shimadzu Corporation) in an environment of 25°C and 40% RH. The breaking stress was calculated for the membrane in both the dry and wet states. The elongation was also calculated from the distance to the breaking point. Measurements were performed with n = 3, and the average values ​​are shown in Table 1.

[0103] Comparative Examples 1 to 4: Electrolyte Membranes 2 to 5 For electrolyte membranes 2 to 5, Fumasep FAAM-20 (manufactured by Fumatech), Fumasep FAA-3-50 (manufactured by Fumatech), CMX-40-10 (manufactured by ORION Polymers), and PiperION-A20-HCO3 (manufactured by Versogen) were measured for breaking stress and elongation in the same manner as above. The results are shown in Table 1.

[0104]

[0105] <Ion Exchange Capacity Test> 50 mg of electrolyte membranes 1 to 5 were immersed in a 1 mol / L aqueous sodium nitrate solution and left at 25°C for 24 hours. Once the chloride ions and nitrate ions in the electrolyte membranes were fully ion-exchanged, potentiometric titration was performed with a 0.02 mol / L aqueous silver nitrate solution. The ion exchange capacity was calculated from the titration volume up to the inflection point and the mass of the electrolyte membrane. For electrolyte membranes 2 to 5, potentiometric titration was performed using the method described above after immersion in a sodium chloride aqueous solution for 48 hours for the purpose of anion exchange. The titration was performed using a HIRANUMA COM-A19. Further tests were performed on electrolyte membrane 1 with membrane thicknesses of 15 μm, 9 μm, and 25 μm. The calculation method is shown in Calculation Method 1. The results are shown in Table 3. [Calculation method 1] Exchange capacity (mmol / g) = (EP1 - BL1) x TF x C1 x K1 / S EP1: Titration volume required to reach the first endpoint (mL) BL1: Titration volume required for the blank test (mL) TF: Factor of the titrant (1.0003) C1: Concentration conversion coefficient (0.0001 mol / mL) K1: Unit conversion coefficient (1000) S: Sample volume (g)

[0106]

[0107] Reference Example 1 Catalyst Coated Electrolyte Membrane 1 A compound represented by Chemical Formula 1-3 was dissolved in a solvent (a mixture of isopropanol and water), and platinum-ruthenium-supported carbon (TEC66E50, manufactured by Tanaka Kikinzoku) was dispersed in the solution to obtain an ionomer solution 1 having the metal dispersed therein. Ionomer solution 2 was obtained in the same manner, except that iridium oxide (Premion, manufactured by THERMO SCIENTIFIC CHEMICALS) was used instead of the platinum-ruthenium-supported carbon. The ionomer solution 1 was applied to the electrolyte membrane 1 by spray coating, and the membrane was dried at 80°C. The opposite surface of the membrane was then coated with the ionomer solution 2 by spray coating, and the membrane was dried at 80°C to obtain a catalyst-coated electrolyte membrane 1 (catalyst area 1 cm × 1 cm) of the present invention.

[0108] [Reference Comparative Example 1: Catalyst Coated Electrolyte Membrane 2] Reference Comparative Example 1 (catalyst coated electrolyte membrane 2) was obtained in the same manner as Reference Example 1, except that the electrolyte membrane 1 was replaced with the electrolyte membrane 2.

[0109] <Anion exchange membrane water electrolysis test> A nickel porous body was installed on the anode side of the catalyst coated electrolyte membranes of Reference Example 1 and Reference Comparative Example 1, and carbon paper was installed on the cathode side as a porous transport layer PTL. An anion exchange membrane water electrolysis test was performed using a JARI standard cell at 80°C with a liquid flow rate of 1 cc / min on the anode side and 0 cc / min on the cathode side. 1 A / cm ２ The measurement results are shown in Table 3.

[0110] The test results of Reference Example 1 confirmed that the catalyst coated electrolyte membrane using the electrolyte membrane of the present invention exhibited low voltage in the anion exchange membrane water electrolysis test and was excellent in water electrolysis performance.

[0111] The electrolyte membrane and catalyst-coated electrolyte membrane of the present disclosure are used as electrolyte membranes for various fuel cells such as polymer electrolyte fuel cells and solid alkaline fuel cells, and for various electrolysis techniques including water electrolysis. In particular, the electrolyte membrane and catalyst-coated electrolyte membrane of the present disclosure are suitably used as electrolyte membranes for anion exchange membrane water electrolysis (AEMWE).

[0112] This application claims priority based on Japanese Patent Application No. 2024-015321, filed February 5, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0113] 1: Polymer having ion exchange groups (electrolyte polymer), 2: Substrate film, 3: Ionomer, 4: Hydrogen generation catalyst, 5: Oxygen generation catalyst, 11: Electrolyte membrane, 12: First catalyst layer, 13: Second catalyst layer, 100: Catalyst-coated electrolyte membrane

Claims

1. An electrolyte membrane that satisfies the following formula (1), where Xdry (MPa) is the breaking stress under dry conditions and Xwet (MPa) is the breaking stress under wet conditions: −0.15≦(Xwet−Xdry) / Xdry≦0.1 (1) 2. The electrolyte membrane according to claim 1, wherein the elongation percentage under dry conditions is Ydry (%) and the elongation percentage under wet conditions is Ywet (%), and the following formula (2) is satisfied: −0.30≦(Ywet−Ydry) / Ywet≦0.1 (2) [Formula 2] 3. The electrolyte membrane according to claim 1, wherein the Xdry is 60 MPa or more.

4. The electrolyte membrane according to claim 2, wherein the Ydry is 50% or more.

5. The electrolyte membrane according to claim 1, which comprises a polymer having an anion exchange group as a constituent element.

6. The electrolyte membrane according to claim 5, further comprising a polymer that does not have ion conductivity.

7. The electrolyte membrane according to claim 1, which has an ion exchange capacity of 0.8 to 1.5 mmol / g.

8. The electrolyte membrane according to claim 1, which has a pore-filling structure.

9. The electrolyte membrane according to claim 1, which contains a polymer having a structural unit represented by the following general formula (1): However, Ar １ is an aromatic group having an ion exchange group or a group in which aromatic rings having an ion exchange group are linked via a single bond, and there are a plurality of Ar １ may be the same or different, Ar ２ is an aromatic group having no ion-exchange group, or a group in which two or more aromatic rings having no ion-exchange group are linked via a single bond or a spiro atom, and a plurality of Ar ２ may be the same or different, Ar １ and an aromatic ring having Ar ２ is linked to the aromatic ring of the formula (I) via a single bond.

10. The electrolyte membrane according to claim 1, which is used as an anion exchange membrane.

11. A catalyst-coated electrolyte membrane having the electrolyte membrane according to any one of claims 1 to 10 and a catalyst layer.

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