WO2025169754A1 - Electrolyte membrane and catalyst-coated electrolyte membrane - Google Patents

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

This disclosure relates to electrolyte membranes and catalyst-coated electrolyte membranes used in water electrolysis. More specifically, it relates to electrolyte membranes used as anion exchange membranes (AEMs) and catalyst-coated electrolyte membranes in which the electrolyte membranes are coated with a catalyst layer.

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 must have excellent ionic conductivity and be durable enough to withstand long-term use.

Among the various 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 method uses an anion exchange membrane (AEM) to separate the anode and cathode chambers (see, for example, Patent Document 1), with pure water or an alkaline aqueous solution supplied to the anode chamber as the anolyte. Pure water or an alkaline aqueous solution can be supplied to the cathode chamber as the anolyte, but it is also possible to use a dry cathode electrolytic cell in which no anolyte is supplied to the cathode chamber. In this dry cathode type, water permeates from the anode chamber into the cathode chamber through the anion exchange membrane, supplying water to the cathode chamber. In the cathode chamber, hydrogen gas and hydroxide ions are produced from the water through a cathode reaction.

As mentioned above, the electrolyte membrane used in the AEMWE method is used in pure water or an alkaline aqueous solution, so in addition to durability in a dry state, durability in a wet state is also an important characteristic.

For example, Patent Document 1 discloses the configuration of a water electrolyzer used in the AEMWE method. 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, high durability is required for the CCM. Note that 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 involves a continuous change of state from liquid to gas between the catalyst layer or ionomer layer and the electrolyte membrane, which increases the mechanical strength required of the CCM.

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 is more likely to become brittle in the dry state. For this reason, electrolyte membranes used in the AEWME method are required to have excellent strength in both the dry and wet states, as well as excellent ionic conductivity.

International Publication No. 2022/244805

In light of the above circumstances, the objective of this disclosure is to provide an electrolyte membrane and a catalyst-coated electrolyte membrane that function as an anion exchange membrane in an anion exchange membrane water electrolysis test at low voltage, with excellent water electrolysis performance and mechanical strength.

As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by focusing on the tensile breaking stress of the electrolyte membrane.
That is, the present invention relates to the following [1] to [11].
[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.
[Number 1]: −0.15≦(Xwet−Xdry)/Xdry≦0.1 (1)
[2]: The electrolyte membrane according to [1], which satisfies the following formula (2), where Ydry (%) is the elongation percentage under dry conditions and Ywet (%) is the elongation percentage under wet conditions.
[Equation 2]: −0.30≦(Ywet−Ydry)/Ywet≦0.1 (2)
[3]: The electrolyte membrane according to [1] or [2], wherein the 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], further comprising a polymer that does not have ion conductivity.
[7]: The electrolyte membrane according to any one of [1] to [6], having an ion exchange capacity of 0.8 to 1.5 mmol/g.
[8]: The electrolyte membrane according to any one of [1] to [7], having 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):
wherein 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 a plurality of Ar ^1s may be the same or different; Ar ² is an aromatic group not having an ion exchange group or a group in which two or more aromatic rings not having an ion exchange group are linked via a single bond or a spiro atom, and a plurality of Ar ^2s may be the same or different;
The aromatic ring of Ar ¹ and the aromatic ring of Ar ² are linked via a single bond.
[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.

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 in an anion exchange membrane water electrolysis test, have low voltage, excellent water electrolysis performance, and excellent mechanical strength.

1 is a diagram showing an example of a layer structure of a catalyst coated electrolyte membrane according to an embodiment of the present invention. FIG. 3 is a diagram showing another example of the layer structure of the catalyst coated electrolyte membrane of the present embodiment.

Below, an example of an embodiment to which the present disclosure is applied is described. 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 with "to" include the stated numerical values. Furthermore, specific 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.

The catalyst-coated electrolyte membrane disclosed herein comprises an electrolyte membrane that functions as an anion exchange membrane and a catalyst layer. In this specification, the term "electrolyte membrane" refers simply to an electrolyte membrane that functions as an anion exchange membrane, and is to be distinguished from a "catalyst-coated electrolyte membrane" in which a catalyst layer is formed as a coating layer on this electrolyte membrane.

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 comprises 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 catalyst-coated electrolyte membrane will be described below.

<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.
[Equation 1]
-0.15≦(Xwet-Xdry)/Xdry≦0.1 (1)
By satisfying the relationship of the above mathematical formula (1), an electrolyte membrane having extremely high durability can be obtained, which exhibits low voltage in an anion exchange membrane water electrolysis test, excellent water electrolysis performance, and excellent mechanical strength, to the extent that it can be used without problems in the AEMWE method.

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 is dissociable and capable of ion exchange. Anion exchange groups are preferred as "ion exchange groups." Suitable examples of anion exchange groups include substituents having a cation, such as groups in which a heteroatom is cationized. Specific examples include quaternary ammonium salts, imidazolium salts, pyridinium salts, and phosphonium salts.

<About breaking stress>
In the present disclosure, the breaking stress of the electrolyte membrane is a value measured according to the following measurement method.
Measurement method;
1) Preparation of Test Pieces 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 film, and the obtained film is cut into a size of 40 mm x 10 mm (hereinafter the same) to prepare a test piece.
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 form a solution, the solution is dropped onto the substrate film, and the solvent is removed to produce a film with a thickness of about 10 to 40 μm. The obtained film is then cut into 40 mm × 10 mm to prepare a test piece. Note that as the substrate film, polyolefin films such as polyethylene, polypropylene, and polytetrafluoroethylene (PTFE), and amide films such as polyimide and polyamide are preferably used, with polyolefin films being more preferred.
The electrolyte membrane of the present disclosure may have a pore-filling structure. In this case, a porous film (also referred to as a porous substrate) is used as the substrate film, and a solution prepared by dissolving a polymer having ion exchange groups in a solvent is impregnated into the substrate by a method such as dipping, spraying, spin coating, or bar coding, followed by drying and cutting to the same size as above to prepare a test piece.

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.

<About dry conditions>
The dry conditions, which are the measurement conditions for Xdry, are measurement conditions in which the film prepared in the above "1) Preparation of test piece" is measured as is.

<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, and the resultant is measured.

As shown in the above formula (1), the electrolyte membrane of the present disclosure has a ratio (Xwet-Xdry)/Xdry of -0.15 or more and 0.1 or less.
More preferred values for the upper limit of (Xwet-Xdry)/Xdry are 0.08, 0.06, 0.04, and 0.02, respectively, and particularly preferably 0. Furthermore, more preferred values for the lower limit are -0.14, -0.13, -0.12, -0.11, and -0.10, respectively, and particularly preferably -0.09. Therefore, particularly preferred values for (Xwet-Xdry)/Xdry are -0.09 or more and 0 or less.

Furthermore, Xdry is preferably 60 MPa or higher. The lower limit of the breaking stress is, in order of preference, 80 MPa, 90 MPa, 100 MPa, and 120 MPa, with 125 MPa being particularly preferred. The upper limit of the breaking stress cannot be discussed in general because it is determined in relation to other components, but it may be, for example, around 180 MPa, with 160 MPa, 150 MPa, and 145 MPa being more preferred. Therefore, the breaking stress is particularly preferably 125 MPa or higher and 145 MPa or lower.

The electrolyte membrane of the present disclosure has a specific relationship between Ydry (%), where Ydry is the elongation rate under dry conditions, and Ywet (%), where Ywet is the elongation rate under wet conditions.
[About Ydry and Ywet]
<Regarding growth rate>
Based on the distance until the membrane broke in the above breaking stress measurement, the elongation rate was calculated using the following calculation formula (3): Elongation rate (%) = distance until the electrolyte membrane broke / sample length × 100 (3)
The dry and wet conditions were the same as those for the breaking stress measurement. The "distance until the 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 rate refers to the ratio of the amount of deformation to the initial length of the membrane.
As shown in the above formula (2), the present electrolyte membrane has a (Ywet-Ydry)/Ydry ratio of -0.30 to 0.10.
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.

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

[polymer]
The electrolyte membrane preferably contains a polymer having an anion-exchange group as a constituent element, and more preferably contains a polymer that does not have ion conductivity in combination.
The polymer used in the present electrolyte membrane is preferably a polyarylene polymer, which provides an electrolyte membrane with excellent chemical durability.
Furthermore, from the viewpoint of imparting excellent ionic 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 enhancing ionic conductivity, a combination of polymer (A) and 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 multiple Ar ^1s may be the same or different. Ar ² is an aromatic group not having an ion exchange group or a group in which two or more aromatic rings not having an ion exchange group are linked via a single bond or a spiro atom, and multiple Ar ^2s may be the same or different. The aromatic ring in Ar ¹ and the aromatic ring in Ar ² are linked via a single bond.

Polymer (A) is a polymer having two or more structural units of the above general formula (1), and has a structure in which Ar ¹ having an ion exchange group and Ar ² not having an ion exchange group are arranged alternately. The aromatic group in Ar ¹ and the aromatic group in Ar ² are bonded by a single bond to form the main chain. Polymer (A) does not have an etheric oxygen (-O-), sulfonyl (-S(=O) _2- ), or carbonyl (-C(=O)-) skeleton in the main chain skeleton, and is therefore excellent in chemical durability, particularly alkali durability. Note that 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 contained as a substituent (side chain) are to be distinguished.

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 preferably a sulfonic acid group ( _-SO3H group), a phosphoric acid group ( _{-H2PO4 group} ), or a carboxylic acid group (-COOH group), with a sulfonic acid group being more preferred. Note that the H in the acidic group may be dissociated or substituted with an alkali metal ion, alkaline earth metal ion, or the like.

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 those 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 groups represented by the following formulae (f-2) and (f-3) being more preferred:

In the formula, each R ^e is independently a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, each R ^f is 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, A ^- is a monovalent or divalent or higher anion, and when there are multiple R ^e or R ^f , the multiple R ^e or R ^f may be the same or different. Note that the wavy line in the formula represents a bond bonded to the aromatic ring side constituting the main chain in Ar ¹ .

Specific examples of the alkyl group in R ^e include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and a cyclohexyl group. Specific examples of the alkyl group in R ^f include a methyl group, an ethyl group, a propyl group, and a butyl group. An example of the aromatic group in R ^f is a phenyl group, and an example of a substituent on the phenyl group is an alkyl group having 1 to 6 carbon atoms.

The above A ⁻ is preferably an inorganic anion, and examples thereof include chloride ion (Cl ⁻ ), bromide ion (Br ⁻ ), iodide ion (I ⁻ ), hydrogen carbonate ion (HCO ₃ ⁻ ), carbonate ion (CO ₃ ²⁻ ), hydroxide ion (OH ⁻ ), sulfate ion (SO ₄ ²⁻ ), chlorate ion (ClO ₃ ⁻ ), nitrate ion (NO ₃ ⁻ ), cyanide ion (CN ⁻ ), sulfite ion (HSO ₃ ⁻ ), bromate ion (BrO ₃ ⁻ ), and fluoride ion (F ⁻ ). Of these, hydroxide ion (OH ⁻ ), bromide ion (Br ⁻ ), bromate ion (BrO ₃ ⁻ ), chloride ion (Cl ⁻ ), hydrogen carbonate ion (HCO ₃ ⁻ ), and carbonate ion (CO ₃ ²⁻ ) are preferred, and hydroxide ion (OH ⁻ ), bromide ion (Br ⁻ ), chloride ion (Cl ⁻ ), hydrogen carbonate ion (HCO ₃ ⁻ ), and carbonate ion (CO ₃ ²⁻ ) are particularly preferred.

The ion exchange group may be directly bonded to the aromatic ring constituting the main chain in ^Ar1 , 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 links 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).
The number of ion exchange groups per aromatic ring constituting the main chain of Ar ¹ may be one or more, and from the viewpoints of ion conductivity and polymer stability, 1 to 2 is preferred.

The aromatic ring constituting the main chain in ^Ar1 may be a benzene ring, a fused 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.

The aromatic ring constituting the main chain of Ar ¹ may further have a substituent other than the ion-exchange group in addition to the above-mentioned 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 methyl, ethyl, propyl, n-butyl, tert-butyl, pentyl, hexyl, and octyl, 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 alkyl groups having 1 to 6 carbon atoms, halogeno groups, and the like. Furthermore, examples of the halogeno group include a fluoro group, a chloro group, a bromo group, and an iodo group.

In terms of excellent mechanical strength, chemical durability, and ionic conductivity, Ar ¹ of the polymer (A) is preferably a group represented by any one of the following formulae (a-1) to (a-10):
A plurality of Ar ^1s in the polymer may be the same or different.

Here, each R ^a is 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, and at least one of the R ^a is an ion exchange group.
The wavy line indicates a bond to ^Ar2 .

The aromatic ring constituting the main chain of ^Ar2 may be the same as that of ^Ar1 , or a group linked via a spiro atom. The aromatic ring in ^Ar2 may have a substituent other than the anion exchange group. Examples of the other substituent include the same as the substituent other than the ion exchange group in ^Ar1 .
Examples of groups in ^Ar2 in which two or more aromatic rings are linked via a spiro atom include groups represented by the following formula (c1). Examples of groups in which two or more aromatic rings are linked via a single bond include groups represented by the following formulas (c2) to (c4). The wavy line indicates a bond to ^Ar1 . From the viewpoint of the packing property of the polymer into the porous substrate, it is preferable that ^Ar2 does not have a spiro atom.

Here, each R 1 ^C independently represents a hydrogen atom, a halogen group, or an organic group.

The weight-average molecular weight of polymer (A) can be adjusted appropriately 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 standpoint of chemical durability, it is preferably 30,000 or higher, more preferably 100,000 or higher, even more preferably 200,000 or higher, and particularly preferably 220,000 or higher. In particular, when the porous substrate is a polyolefin-based porous substrate, polymer (A) can be easily filled into pores even if its weight-average molecular weight is 100,000 or higher. The upper limit of the weight-average molecular weight may be approximately 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).

Furthermore, the molecular weight distribution of polymer (A) is preferably 2.0 or more and 10.0 or less. Generally, molecular weight distribution is expressed as the value of Mw/Mn, using the weight average molecular weight (Mw) and the number average molecular weight (Mn). More preferred upper limits of the molecular weight distribution (Mw/Mn) of polymer (A) are 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, respectively, and particularly preferably 3.6. More preferred lower limits are 2.5, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, and 3.4, respectively, and particularly preferably 3.5. Therefore, the molecular weight distribution (Mw/Mn) is most preferably 3.5 or more and 3.6 or less.

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 a structure in which an anion exchange group is not introduced into Ar ¹ of the structural unit (1). The polymer (A) may also contain other structures that may arise during synthesis.

Among the polymers (A), the following polymers (A1) to (A4) are preferred. From the standpoint of the polymer's ability to fill a porous substrate, polymer (A2), polymer (A3), or polymer (A4) are preferred, with polymer (A2) or polymer (A3) being more preferred. Furthermore, from the standpoint of the polymer's ability to fill, mechanical strength, and chemical durability, polymer (A3) is more preferred. These polymers are described in detail below.

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

Here, R ¹ to 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 embodiments are also the same.

Examples of the alkyl group having 1 to 4 carbon atoms in R ¹ to R ¹⁰ include a methyl group, an ethyl group, a propyl group, and a tert-butyl group. In the polymer (A1), from the viewpoint of improving solubility, it is preferable that at least one of R ¹ and R ¹⁰ is an alkyl group, more preferably that R ¹ and R ¹⁰ are alkyl groups, and further more preferably that R ¹ and R ¹⁰ are tert-butyl groups. By having a bulky substituent on at least one of ^{R 1} and R ¹⁰ , aggregation of the polymer due to π-π stacking or the like is suppressed, and solubility in solvents is improved. On the other hand, it is preferable that R ² to R ⁹ each independently represent a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

The polymer (A1) has a structure in which Ar ¹ having an anion exchange group and a spirobifluorene skeleton are alternately repeated. Each element constituting the main chain skeleton of the polymer (A1) 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 skeleton forms 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.

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

In Scheme A1, R ^a represents an anion-exchange group, and R ^b represents a substituent corresponding to R ¹ and R ¹⁰ in general formula (1-1).

In the example of Scheme A1, a compound (C) having a brominated spirobifluorene skeleton is synthesized from a compound (B) having a desired substituent ^Rb (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 synthesize a compound (E) that serves as a precursor to ^Ar1 in general formula (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 with reference to known reactions.

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

Here, R ^a is a group having an anion exchange group, and Ar ² is the same as in the general formula (1).

Polymer (A2) is a polymer having two or more of the above structural units (1-2) and is a compound whose main chain is entirely aromatic. Because of this structure, polymer (A2) has excellent resistance to alkalis, radicals, etc.

Among these, Ar ² in the polymer (A2) is preferably a phenylene group, a biphenylene group, or a terphenylene group, and more preferably 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).

Here, R is a substituent that ^Ar2 may have, r is an integer of 0 to 4, and a plurality of Rs and rs may be the same or different.

When Ar ² 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. The following formula shows a representative case where Ar ² is a p-phenylene group, but 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 tends to be located outside the folded portion of the structure. Therefore, intramolecular aggregation due to the folded portion of the main chain is suppressed. As a result, the polymer is capable of forming an electrolyte membrane with excellent ion conductivity.

The group R ^a having an anion-exchange group in the polymer (A2) is preferably a group represented by the following formula (R ^a -1).

Here, R ^b2 is an anion exchange group, and p2 is an integer of 1 to 20. The wavy line indicates a bond to the benzene ring.

In the group represented by formula (R ^a -1), the carbon atom adjacent to the benzene ring constituting the main chain is a quaternary carbon. Therefore, π-π stacking between polymers (A2) is suppressed. As a result, aggregation of the polymer (A2) is suppressed, making it more soluble in a solvent and providing excellent handleability during film formation, etc.
p2 represents {(the number of carbon atoms from R ^b2 to the quaternary carbon)-1} and 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.

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

In the formula, X and ^X1 each represent a halogen atom, and ^Ar2 and p2 are as defined above. The halogen atom represented by ^X1 is preferably Br.

In the example of Scheme A2 above, first, compound (H) and compound (I) having the desired ^Ar2 are 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 Scheme A2 above, a quaternary ammonium group is introduced, but other ionic functional groups can also be introduced similarly. The reaction conditions for each of the above steps may be determined with reference to known reactions.

Polymer (A3)
Polymer (A3) is a repeating unit represented by general formula (1) in which ^Ar2 has a partial structure represented by formula (2) below at both ends. In other words, ^Ar2 is a divalent group containing an aromatic ring having a fluoro group (-F) at the α-position of the terminal carbon atom. Here, the term "terminal end of ^Ar2" refers to the carbon atom bonded to ^Ar1 . Note that the wavy line represents a bond to ^Ar1 , and the dotted line indicates that part of the aromatic ring is omitted.

Polymer (A3) has a structure in which Ar ¹ having an anion exchange group and Ar ² having a partial structure (2) containing a fluoro group (-F) are arranged alternately. Ar ¹ and Ar ² constituting the main chain each have an aromatic group, providing excellent chemical durability against alkalis, radicals, and the like. Furthermore, polymer (A3) has Ar ¹ having an ion exchange group linked to the side chain terminal via an alkyl chain and Ar ² having no ion exchange group arranged alternately. Due to this structure, polymer (A3) has excellent solubility in solvents and ionic conductivity. Furthermore, the reactivity of the compound having partial structure (2) with the compound represented by formula (4) described below is high, allowing for the production of a polymer with a higher molecular weight. Using this high-molecular-weight polymer also makes it possible to form a film with superior durability.

Ar ² may have two partial structures (2) in one ring structure (e.g., a benzene ring), as in formula (b-1) described below, or one C—F bond may constitute two partial structures (2), as in formula (b-2) described below. Furthermore, in the case of the chain polycyclic hydrocarbon, each of the two ring structures contained in 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). It is preferable that Ar ² in the polymer (A3) does not have a spiro atom.

In the polymer (A3), from the viewpoint of being able to form an electrolyte membrane excellent in ionic conductivity, membrane formability, chemical durability, and membrane strength, it is preferable that Ar ² be one or more selected from the following formulae (d1) to (d9), where the wavy line indicates a bond to Ar ¹ :

Here, each ^Rd independently represents a hydrogen atom, a halogeno group, or an organic group.

Examples of the halogeno group in ^Rd include a fluoro group, a chloro group, a bromo group, and an iodo group, and among these, a fluoro group is preferred. Examples of the organic group in ^Rd include a linear or branched alkyl group having 1 to 20 carbon atoms (not including the carbon atoms of the substituent) that may have a substituent (e.g., a halogeno group).

From the viewpoint of ease of production, Ar ² is preferably represented by the following formulae (d10) to (d14): The wavy line indicates a bond to Ar ¹ .

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

wherein each ^X1 is independently Br or I, ^Ar3 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, and ^Ar2 is the same as in polymer (A3).

Since ^X1 in compound (4) and the hydrogen atom in the following partial structure (5a) in ^Ar2 in compound (5) have excellent reactivity, 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) can be synthesized relatively easily.

In the above scheme A3, first, compound (4) having the desired Ar ³ and compound (5) having the desired Ar ² are prepared. These compounds are then reacted, for example, in a solvent in the presence of a Pd complex, a ligand, a carboxylic acid (RCO ₂ H), and a base at 80 to 140°C for 1 to 48 hours to obtain a polymer having structural unit (3).

Next, the desired ion exchange group is introduced into a polymer having structural unit (3), thereby obtaining polymer (A3). In this way, polymer (A3) can be easily produced with very few synthesis steps by using compound (4) and compound (5) as raw materials.

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

Here, ring Ar ¹¹ and ring Ar ¹² are rings fused to a benzene ring, and are 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).

The polymer (A4) has a structure in which Ar ¹ having an anion exchange group and Ar ² consisting of three or more fused rings are repeated alternately. Generally, polymers containing many ion exchange groups tend to swell easily, but the polymer (A4) has excellent swelling resistance due to the alternating repeat of Ar ¹ and Ar ² and the π-π stacking of the three or more fused rings.

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

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, and then eliminating the substituent (TL).

In the formula (1-4), LT represents a group represented by any one of the general formulae (LT1) to (LT3), R ¹¹ represents an alkyl group having 1 to 6 carbon atoms, R ¹² represents an alkyl group having 1 to 6 carbon atoms or a phenyl group, and Ar ¹ , Ar ¹¹ , and Ar ¹² are the same as those in the general formula (1-4).
The alkyl group having 1 to 6 carbon atoms in R ¹¹ and R ¹² may be either a linear or branched alkyl group, and specific examples thereof 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.

As mentioned above, polymer (A4) has excellent swelling resistance. Therefore, it is difficult to dissolve in various organic solvents, which poses a problem of poor handling during processing. The precursor has a bulky substituent (TL) represented by one of the general formulas (LT1) to (LT3) introduced at the site corresponding to the fused ring of polymer (A4). This 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.

The synthesis method for the precursor is not particularly limited, but a suitable specific example is the method shown in Scheme A4 below.

An example of each step in the above scheme A4 will be described.
Step (i): A toluene solution of the compound (1) is prepared, diethyl azodicarboxylate (DEAD) is added, and the mixture is heated under reflux to obtain the compound (2).
Step (ii): Separately, an N,N-dimethylformamide (DMF) solution of the compound (3) is prepared, and bis(pinacolato)diborane, potassium acetate (KOAc), and [1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloride (Pd(dppf)Cl ₂ ) are added thereto, followed by heating to 90° C. to obtain the compound (4).
Step (iii): To a toluene solution of the obtained compound (2) and compound (4), tripotassium phosphate (K ₃ PO ₄ ) and tetrakis(triphenylphosphine)palladium (Pd(PPH ₃ ) ₄ ) are added and the mixture is heated to 100° C. to polymerize the compound, thereby obtaining 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 mixed solvent of DMF/THF (tetrahydrofuran) to obtain a precursor represented by the above chemical formula (7).

[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 in. By using such a configuration, mechanical strength can be imparted to the polyarylene polymer, which has excellent chemical durability.
The porous substrate is a substrate having pores capable of holding a polymer, and it is preferable that at least some of the pores of the porous substrate form through-holes in order to improve ion conductivity.
The substrate is preferably in the form of a nonwoven fabric or a porous film (porous substrate) from the viewpoint of imparting mechanical strength, and more preferably in the form of a porous film.
The porosity of the porous substrate (=void volume/bulk volume×100(%)) 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 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.
The pore size of the porous substrate is preferably 10 to 10,000 nm, more preferably 10 to 1,000 nm, in terms of the average pore size, from the viewpoint of filling and holding the polyarylene polymer and mechanical strength.
The material of the porous substrate is preferably a polyolefin-based porous substrate in terms of chemical durability, particularly stability in alkali.Furthermore, the use of a polyolefin-based porous substrate has the advantage that it is easy to fill with polyarylene polymers, especially high-molecular-weight polyarylene polymers having a weight-average molecular weight of 100,000 or more.As the polyolefin-based porous substrate, from the viewpoint of mechanical strength and chemical resistance, polyethylene porous substrates, polypropylene porous substrates, or polytetrafluoroethylene porous substrates are particularly preferred.Furthermore, among the polyethylene porous substrates, ultra-high molecular weight polyethylene (for example, weight-average molecular weight of 1,000,000 or more) porous substrates are particularly preferred.

One example of a method for producing a pore-filling membrane is a method in which a polyarylene polymer is applied to a porous substrate and then dried.
Methods for applying a polyarylene polymer to a porous substrate include, for example, preparing a solution of the polyarylene polymer and using dipping, spraying, spin coating, bar coding, etc. The polyarylene polymer solution is then permeated into the porous substrate, and then dried to obtain a pore-filling film. The filling of the porous substrate with the polyarylene polymer can be confirmed, for example, by Raman analysis.

<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, which can be appropriately selected from known metals or metal alloys, such as 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.
The cathode catalyst is preferably a metal or a metal alloy, which can be appropriately selected from known metals and metal alloys, such as platinum, cobalt, nickel, palladium, iron, silver, gold, copper, iridium, molybdenum, rhodium, chromium, tungsten, manganese, ruthenium, metal compounds thereof, metal oxides thereof, and alloys containing two or more of these metals.

The catalyst layer is preferably configured such that the metal is dispersed in an ionomer, from the viewpoint of enhancing adhesion to the electrolyte polymer and increasing 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, and PFSAs selected from Nafion ^™ (Chemours Company), Aquivion (registered trademark) (Solvay Specialty Polymers), Flemion ^™ (Asahi Glass Group), and Aciplex _™ (Asahi Kasei Chemicals Corporation) are commercially available.

<Preparation 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, preferably both sides, of the 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. 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. 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. When an alkaline solution is passed through this electrochemical cell, and a current is passed from a power source to the electrochemical cell containing an electrolyte membrane and an ionomer that have been ion-exchanged with ^OH- ions by the alkaline solution, water electrolysis performance refers to the ability to perform water electrolysis without a significant increase in voltage. Specifically, platinum-supported carbon or platinum-ruthenium alloy-supported carbon is typically used as the hydrogen generation catalyst, while iridium oxide is typically used as the oxygen generation catalyst. When 1 mol/L potassium hydroxide is used as the alkaline solution and the electrochemical cell is at 80°C, the electrolytic performance should be 2.0 V or less at ¹ A/cm², preferably 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.

The present invention will be explained in more detail below using examples. Note that these examples do not limit the scope of the present invention, and modifications can be made as appropriate without departing from the spirit of the invention.

[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 containing sodium hydroxide (200 g) in aqueous solution (600 mL). The two-neck flask was then added via 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 x 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).

[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 nitrogen (20 mL/min) for 30 minutes. Next, cesium carbonate (173 mmol), pivalic acid (57.7 mmol), tris(2-methoxyphenyl)phosphine (407 mg), 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.
To the resulting reaction product (solids), 1M hydrochloric acid (100 mL) and toluene (600 mL) were added, and the mixture was stirred at 60°C for 30 minutes. The insoluble matter was then 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 then 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 under vacuum to obtain compound (1-2) with a molecular weight distribution of 4.88. GPC results for this compound (1-2) confirmed that the peak end was 14.025 min, indicating a reduction in low molecular weight components.

[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. Thereafter, 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.

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

<Measurement of rupture stress and elongation rate 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.

[Comparative Examples 1 to 4: Electrolyte membranes 2 to 5]
The breaking stress and elongation percentage were measured in the same manner as above for 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) as electrolyte membranes 2 to 5. The results are shown in Table 1.

<Ion exchange capacity test>
Using 1 to 5, 50 mg of electrolyte membranes, they were immersed in a 1 mol/L aqueous sodium nitrate solution and left at 25°C for 24 hours. After sufficient ion exchange of chloride ions and nitrate ions in the electrolyte membranes had occurred, potentiometric titration was performed with a 0.02 mol/L aqueous silver nitrate solution. The ion exchange capacity was calculated from the titration amount up to the inflection point and the mass of the electrolyte membrane.
For the purpose of anion exchange, electrolyte membranes 2 to 5 were immersed in an aqueous sodium chloride solution for 48 hours, and then subjected to potentiometric titration using the method described above. The titration was performed using a COM-A19 made by HIRANUMA Corporation.
Further tests were conducted on the electrolyte membrane 1 by changing the membrane thickness to 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 (mL) required to reach the first endpoint
BL1: Titration volume required for blank test (mL)
TF: titrant factor (1.0003)
C1: Concentration conversion factor (0.0001 mol/mL)
K1: Unit conversion factor (1000)
S... Sample collection amount (g)

[Reference Example 1: Catalyst coated electrolyte membrane 1]
A compound represented by Chemical Formula 1-3 was dissolved in a solvent (a mixed solution 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 in which the metal was dispersed.
Ionomer solution 2 was also obtained in the same manner, except that iridium oxide (Premion: manufactured by THERMO SCIENTIFIC CHEMICALS) was used in place of the carbon carrying platinum-ruthenium.
The electrolyte membrane 1 was coated with the ionomer solution 1 by spray coating and dried at 80° C. Subsequently, the opposite surface was coated with the ionomer solution 2 by spray coating and dried at 80° C., thereby obtaining a catalyst coated electrolyte membrane 1 (catalyst area 1 cm × 1 cm) of the present invention.

[Reference Comparative Example 1: Catalyst coated electrolyte membrane 2]
A comparative example for reference 1 (catalyst coated electrolyte membrane 2) was obtained in the same manner as in the example for reference 1, except that the electrolyte membrane 1 was replaced with the electrolyte membrane 2.

<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 as a porous transport layer PTL on the cathode side. 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. The measurement results at 1 A/ ^cm² are shown in Table 3.

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

The electrolyte membrane and catalyst-coated electrolyte membrane disclosed herein are used as electrolyte membranes in various fuel cells, such as polymer electrolyte fuel cells and solid alkaline fuel cells, and in various electrolysis technologies, including water electrolysis. In particular, the electrolyte membrane and catalyst-coated electrolyte membrane disclosed herein are suitable for use as electrolyte membranes in anion exchange membrane water electrolysis (AEMWE).

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.

1: Polymer with ion exchange groups (electrolyte polymer), 2: Base 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 (11)

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.
[Equation 1]
-0.15≦(Xwet-Xdry)/Xdry≦0.1 (1) 2. The electrolyte membrane according to claim 1, wherein the following formula (2) is satisfied, where Ydry (%) is the elongation percentage under dry conditions and Ywet (%) is the elongation percentage under wet conditions.
[Equation 2]
-0.30≦(Ywet-Ydry)/Ywet≦0.1 (2) The electrolyte membrane according to claim 1, wherein Xdry is 60 MPa or more. The electrolyte membrane described in claim 2, wherein the Ydry is 50% or more. The electrolyte membrane according to claim 1, which has a polymer having an anion exchange group as a constituent element. The electrolyte membrane of claim 5, further comprising a polymer that does not have ion conductivity. The electrolyte membrane according to claim 1, having an ion exchange capacity of 0.8 to 1.5 mmol/g. The electrolyte membrane of claim 1 having a pore-filling structure. 2. The electrolyte membrane according to claim 1, comprising 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 a plurality of Ar ^1s may be the same or different;
^Ar2 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 ^Ar2s may be the same or different;
The aromatic ring of Ar ¹ and the aromatic ring of Ar ² are linked via a single bond. The electrolyte membrane of claim 1, used as an anion exchange membrane. A catalyst-coated electrolyte membrane having the electrolyte membrane described in any one of claims 1 to 10 and a catalyst layer.