Solid polymer electrolyte membrane, membrane electrode assembly, water electrolysis device, electrolytic hydrogenation device, and method for producing hydrogen

Abstract

Provided are: a solid polymer electrolyte membrane excellent in airtightness during high-pressure water electrolysis; a membrane electrode assembly; a water electrolysis device; an electrolytic hydrogenation device; and a method for producing hydrogen.　A solid polymer electrolyte membrane according to the present disclosure contains a fluorine-containing polymer having an ion exchange group, and a reinforcing material, wherein: the reinforcing material is composed of polyether ether ketone; the ion exchange capacity of the fluorine-containing polymer is 1.10 milliequivalents per gram of dry resin or more; and the content of the reinforcing material is 6.0 mass % or more with respect to the total mass of the solid polymer electrolyte membrane.

Description

Solid polymer electrolyte membrane, membrane electrode assembly, water electrolysis apparatus, electrolytic hydrogenation apparatus, and hydrogen production method.

[0001] This disclosure relates to a solid polymer electrolyte membrane, a membrane electrode assembly, a water electrolysis apparatus, an electrolytic hydrogenation apparatus, and a method for producing hydrogen.

[0002] Ion exchange membranes are used in various batteries, electrolysis processes, and ion separation processes. Patent Document 1 discloses an ion exchange membrane comprising a fluorinated ionomer (fluorine-containing polymer) having sulfonic acid groups and a woven fabric (reinforcement material) formed from a material having a predetermined tensile modulus, wherein the expansion rate in the Z direction (film thickness direction) after immersion in boiling water for one hour is less than 60%. Here, the ion exchange membrane (solid polymer electrolyte membrane) is installed in the tank of a water electrolysis apparatus in the form of a membrane electrode assembly in which an anode, ion exchange membrane, and cathode are stacked in this order, and a gasket is usually attached to the periphery of the membrane electrode assembly.

[0003] International Publication No. 2024 / 086102

[0004] During operation of a water electrolysis apparatus, a large pressure is applied to the solid polymer electrolyte membrane separating the anode chamber and the cathode chamber. The inventors have found that this can weaken the packing of the solid polymer electrolyte membrane near the gasket, potentially leading to water leakage. Therefore, it is considered that excellent airtightness of the solid polymer electrolyte membrane is required during high-pressure water electrolysis. The inventors have found that when a membrane electrode assembly is manufactured using an ion exchange membrane (solid polymer electrolyte membrane) as described in Patent Document 1, and the assembly is installed in the tank of a water electrolysis apparatus with a gasket attached to its periphery, and high-pressure water electrolysis is performed, the airtightness of the ion exchange membrane is sometimes insufficient, indicating room for improvement.

[0005] This disclosure is made in view of the above problems, and one embodiment of the present invention aims to provide a solid polymer electrolyte membrane, a membrane electrode assembly, a water electrolysis apparatus, an electrolytic hydrogenation apparatus, and a method for producing hydrogen that are excellent in airtightness during high-pressure water electrolysis.

[0006] The disclosure includes the following embodiments: [1] A solid polymer electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups and a reinforcing material, wherein the reinforcing material is composed of a polyetheretherketone, the ion exchange capacity of the fluorine-containing polymer is 1.10 milliequivalents / gram dry resin or more, and the content of the reinforcing material is 6.0% by mass or more with respect to the total mass of the solid polymer electrolyte membrane. [2] The solid polymer electrolyte membrane according to [1], wherein the reinforcing material is a woven fabric. [3] The solid polymer electrolyte membrane according to [2], wherein the woven fabric is composed of warp threads and weft threads, and the density of the warp threads and the density of the weft threads are each independently 110 threads / inch or more. [4] The solid polymer electrolyte membrane according to any one of [1] to [3], wherein the film thickness of the solid polymer electrolyte membrane is 50 to 150 μm. [5] The solid polymer electrolyte membrane according to any one of [1] to [4], wherein the content of the reinforcing material is 8.0% by mass or less with respect to the total mass of the solid polymer electrolyte membrane. [6] The solid polymer electrolyte membrane according to any one of [1] to [5], wherein the ion exchange group is a sulfonic acid type functional group. [7] The solid polymer electrolyte membrane according to any one of [1] to [6], wherein the fluorine-containing polymer comprises a unit based on a fluorine-containing olefin and a unit having a sulfonic acid type functional group and a fluorine atom. [8] The solid polymer electrolyte membrane according to [7], wherein the unit having a sulfonic acid type functional group and a fluorine atom is a unit represented by formula (1). Formula (1) -[CF ２ -CF(-L-(SO ３ M) ｎ)]—L is an n+1-valent perfluorinated hydrocarbon group which may contain an etheric oxygen atom, M is a hydrogen atom, an alkali metal or a quaternary ammonium cation, and n is 1 or 2. [9] A solid polymer electrolyte membrane according to any one of [1] to [8], which is used in a water electrolysis device.

[10] An anode having a catalyst layer, a cathode having a catalyst layer, and a solid polymer electrolyte membrane according to any one of [1] to [9], which is disposed between the anode and the cathode, A membrane electrode assembly comprising:

[11] A water electrolysis device comprising the membrane electrode assembly according to

[10] .

[12] An electrolytic hydrogenation device comprising the membrane electrode assembly according to

[10] .

[13] A method for producing hydrogen, which electrolyzes water using the water electrolysis device according to

[11] to produce hydrogen.

[0007] According to one embodiment of the present invention, there are provided a solid polymer electrolyte membrane, a membrane electrode assembly, a water electrolysis device, an electrolytic hydrogenation device, and a method for producing hydrogen, which are excellent in airtightness during high-pressure water electrolysis.

[0008] It is a cross-sectional view showing an example of the membrane electrode assembly of the present disclosure.

[0009] The following definitions of terms apply throughout this specification and the claims, unless otherwise specified. "Ion exchange group" means a group capable of exchanging at least a part of the ions contained in this group with other ions. Examples thereof include the following sulfonic acid type functional group and carboxylic acid type functional group. "Sulfonic acid type functional group" means a sulfonic acid group (—SO ３ H), or a sulfonate group (—SO ３ M ２ . However, M ２ is an alkali metal or a quaternary ammonium cation.). "Carboxylic acid type functional group" means a carboxylic acid group (—COOH), or a carboxylate group (—COOM １ . However, M １This means an alkali metal or a quaternary ammonium cation. "Precursor film" is a film containing a polymer having a group that can be converted into an ion exchange group. "Group that can be converted into an ion exchange group" means a group that can be converted into an ion exchange group by treatments such as hydrolysis or acidification. "Group that can be converted into a sulfonic acid type functional group" means a group that can be converted into a sulfonic acid type functional group by treatments such as hydrolysis or acidification. "Group that can be converted into a carboxylic acid type functional group" means a group that can be converted into a carboxylic acid type functional group by known treatments such as hydrolysis or acidification.

[0010] In polymers, a "unit" refers to an atomic group derived from one monomer molecule, formed by the polymerization of monomers. A unit may be an atomic group directly formed by a polymerization reaction, or it may be an atomic group in which a portion of the atomic group is converted to a different structure by processing the polymer obtained by the polymerization reaction.

[0011] Numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Also, in numerical ranges described in this specification, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0012] [Solid Polymer Electrolyte Membrane] The solid polymer electrolyte membrane of this disclosure (hereinafter also referred to as "this electrolyte membrane") is a solid polymer electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups (hereinafter also referred to as "fluorine-containing polymer (I)") and a reinforcing material, wherein the reinforcing material is composed of polyetheretherketone, the ion exchange capacity of the fluorine-containing polymer is 1.10 milliequivalents / gram dry resin or more, and the content of the reinforcing material is 6.0% by mass or more of the total mass of the solid polymer electrolyte membrane. When this electrolyte membrane is applied to an electrolytic device and the electrolyte membrane is immersed in water, the expansion of the electrolyte membrane in the in-plane direction is suppressed by the reinforcing material composed of polyetheretherketone, but the electrolyte membrane tends to expand in the film thickness direction. Furthermore, it is considered that the electrolyte membrane tends to expand more in the film thickness direction because the content of the reinforcing material composed of polyetheretherketone is 6.0% by mass or more. Furthermore, because the ion exchange capacity of the fluorine-containing polymer (I) is 1.10 milliequivalents / gram dry resin or higher, the water content of this electrolyte membrane increases when it is immersed in water, which is thought to make the electrolyte membrane more prone to expansion in the direction of film thickness. As a result, the sealing performance near the gasket is improved by the expansion of the electrolyte membrane in the direction of film thickness, and it is presumed that excellent airtightness can be achieved even when high-pressure water electrolysis is performed.

[0013] <Fluorine-containing polymer> This electrolyte membrane contains a fluorine-containing polymer (I). The ion exchange capacity of the fluorine-containing polymer (I) is 1.10 milliequivalents / gram dry resin or more. From the viewpoint of being able to further reduce the electrolysis voltage when applied to an electrolytic device and having superior effects of this disclosure, a capacity of 1.15 milliequivalents / gram dry resin or more is preferred, more preferably 1.20 milliequivalents / gram dry resin or more, and even more preferably 1.25 milliequivalents / gram dry resin or more. From the viewpoint of the mechanical strength of the electrolyte membrane, the ion exchange capacity of the fluorine-containing polymer (I) is preferably 2.00 milliequivalents / gram dry resin or less, more preferably 1.50 milliequivalents / gram dry resin or less, even more preferably 1.43 milliequivalents / gram dry resin or less, and particularly preferably 1.30 milliequivalents / gram dry resin or less. The ion exchange capacity of the fluorine-containing polymer (I) is preferably 1.10 milliequivalents / gram dry resin or more and 2.00 milliequivalents / gram dry resin or less, more preferably 1.15 milliequivalents / gram dry resin or more and 1.50 milliequivalents / gram dry resin or less, even more preferably 1.20 milliequivalents / gram dry resin or more and 1.43 milliequivalents / gram dry resin or less, and particularly preferably 1.25 milliequivalents / gram dry resin or more and 1.30 milliequivalents / gram dry resin or less. The ion exchange capacity of the fluorine-containing polymer (I) can be determined by the method described in the Examples section below.

[0014] The fluorine-containing polymer (I) used in this electrolyte membrane may be one type, or two or more types may be used in a laminated or mixed form. This electrolyte membrane may contain polymers other than fluorine-containing polymer (I), but it is preferable that the polymers in this electrolyte membrane consist substantially of fluorine-containing polymer (I). "Substantially consisting of fluorine-containing polymer (I)" means that the content of fluorine-containing polymer (I) is 95% by mass or more of the total mass of polymers in this electrolyte membrane. An upper limit for the content of fluorine-containing polymer (I) is 100% by mass of the total mass of polymers in this electrolyte membrane. Specific examples of polymers other than fluorine-containing polymer (I) include one or more polyazole compounds selected from the group consisting of polymers of heterocyclic compounds containing one or more nitrogen atoms in the ring, and polymers of heterocyclic compounds containing one or more nitrogen atoms and oxygen and / or sulfur atoms in the ring. Specific examples of polyazole compounds include polyimidazole compounds, polybenzimidazole compounds, polybenzobisimidazole compounds, polybenzoxazole compounds, polyoxazole compounds, polythiazole compounds, and polybenzothiazole compounds. In addition, from the viewpoint of oxidation resistance of this electrolyte membrane, other polymers such as polyphenylene sulfide resins and polyphenylene ether resins can also be mentioned.

[0015] The fluorine-containing polymer (I) has ion exchange groups. Specific examples of ion exchange groups include sulfonic acid-type functional groups and carboxylic acid-type functional groups, with sulfonic acid-type functional groups being preferred because they can further reduce the electrolysis voltage. The fluorine-containing polymer (I) may or may not contain carboxylic acid-type functional groups. Below, we will mainly describe in detail embodiments of fluorine-containing polymers having sulfonic acid-type functional groups (hereinafter also referred to as "fluorine-containing polymer (S)").

[0016] The fluorine-containing polymer (S) preferably contains units based on fluorine-containing olefins and units having sulfonic acid-type functional groups and fluorine atoms. Examples of fluorine-containing olefins include fluoroolefins having 2 to 3 carbon atoms and one or more fluorine atoms in the molecule. Specific examples of fluoroolefins include tetrafluoroethylene (hereinafter also referred to as "TFE"), chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and hexafluoropropylene. Among these, TFE is preferred in terms of monomer production cost, reactivity with other monomers, and the properties of the resulting fluorine-containing polymer (S). One type of fluorine-containing olefin may be used alone, or two or more types may be used in combination. The content of units based on fluorine-containing olefins relative to the total units contained in the fluorine-containing polymer (S) is preferably 65 to 95 mol%.

[0017] As a unit having a sulfonic acid type functional group and a fluorine atom, the unit represented by formula (1) is preferred. Formula (1) -[CF ２ -CF(-L-(SO ３ M) ｎ ) ] -

[0018] L is an n+1 valent perfluorohydrocarbon group which may contain an etheric oxygen atom. The etheric oxygen atom may be located at the terminal end of the perfluorohydrocarbon group or between carbon atoms. The number of carbon atoms in the n+1 valent perfluorohydrocarbon group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.

[0019] L is preferably an n+1 valent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom, and particularly preferably a divalent perfluoroalkylene group which may contain an etheric oxygen atom in the n=1 embodiment, or a trivalent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom in the n=2 embodiment. The above divalent perfluoroalkylene group may be linear or branched.

[0020] M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation. n is 1 or 2. If n is 2, the two M atoms may be the same or different.

[0021] The unit represented by formula (1) is preferably the unit represented by formula (1-1), the unit represented by formula (1-2), the unit represented by formula (1-3), or the unit represented by formula (1-4). Formula (1-1) - [CF ２ -CF(-OR-R) ｆ１ -SO ３ M)] - Formula (1-2) - [CF ２ -CF(-R ｆ１ -SO ３ M) ]-

[0022]

[0023]

[0024] R ｆ１ This is a perfluoroalkylene group which may contain an oxygen atom between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.

[0025] R ｆ２ This is a perfluoroalkylene group which may contain a single bond or an oxygen atom between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.

[0026] R ｆ３ This is a perfluoroalkylene group which may contain a single bond or an oxygen atom between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.

[0027] r is 0 or 1. m is 0 or 1. M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation.

[0028] Of the units represented by formula (1-1) and formula (1-2), the unit represented by formula (1-5) is more preferable. Formula (1-5) - [CF ２ -CF (-(CF ２ ) ｘ - (OCF ２ CFY) ｙ -O-(CF ２ ) ｚ -SO ３ M) - x is 0 or 1, y is an integer from 0 to 2, z is an integer from 1 to 4, and Y is F or CF ３ Therefore, M is as described above.

[0029] The following are specific examples of units represented by equation (1-1). In the equation, w is an integer from 1 to 8, and x is an integer from 1 to 5. The definition of M in the equation is as described above. -[CF ２ -CF(-O-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF(-O-CF) ２ CF (CF ３ )-O-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF(-(O-CF ２ CF (CF ３ )) ｘ -SO ３ M) ]-

[0030] The following are specific examples of units represented by equation (1-2). w in the equation is an integer from 1 to 8. The definition of M in the equation is as described above. -[CF ２ -CF (-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF (-CF ２ -O-(CF ２ ) ｗ -SO ３ M) ]-

[0031] The unit represented by formula (1-3-1) is preferred over the unit represented by formula (1-3-3). The definition of M in the formula is as described above.

[0032]

[0033] R ｆ４ R is a linear perfluoroalkylene group having 1 to 6 carbon atoms. ｆ５ This is a linear perfluoroalkylene group having 1 to 6 carbon atoms, which may contain single bonds or oxygen atoms between carbon atoms. The definitions of r and M are as described above.

[0034] The following are specific examples of units represented by equation (1-3-1):

[0035]

[0036] The unit represented by formula (1-4) is preferably the unit represented by formula (1-4-1). ｆ１ , R ｆ２ The definition of M is as described above.

[0037]

[0038] The following are specific examples of units represented by equation (1-4-1):

[0039]

[0040] The units having sulfonic acid-type functional groups and fluorine atoms may be used individually or in combination of two or more types. The content of units having sulfonic acid-type functional groups and fluorine atoms relative to the total number of units in the fluorine-containing polymer (S) is preferably 5 to 35 mol%.

[0041] Fluorine-containing polymer (I) may contain units based on fluorine-containing olefins, as well as units based on other monomers other than those having sulfonic acid-type functional groups and fluorine atoms. Specific examples of other monomers include CF ２ = CFR ｆ６ (However, R ｆ６ (These are perfluoroalkyl groups having 2 to 10 carbon atoms.) CF ２ = CF - ORｆ７ (However, R ｆ７ (These are perfluoroalkyl groups having 1 to 10 carbon atoms.) CF ２ = CFO (CF ２ ) ｖ CF = CF ２ (wherein v is an integer between 1 and 3.) Examples include monomers having a cyclic ether structure, such as those described in International Publication No. 2020 / 184681. The content of units based on other monomers is preferably 30% by mass or less, may be 1% by mass or less, or 0.1% by mass or less, relative to the total units in the fluorine-containing polymer (I), in order to maintain ion exchange performance, and may not contain units based on other monomers.

[0042] The electrolyte membrane may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, for example, one embodiment may involve stacking multiple layers containing a fluorine-containing polymer (I) with different ion exchange capacities.

[0043] The fluorine-containing polymer content is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 91% by mass or more, relative to the total mass of the electrolyte membrane, from the viewpoint of superior effects of this disclosure. The fluorine-containing polymer content is preferably 94% by mass or less, more preferably 93% by mass or less, and even more preferably 92% by mass or less, relative to the total mass of the electrolyte membrane, from the viewpoint of improving the proton conductivity of the electrolyte membrane and further reducing the electrolysis voltage when applied to an electrolytic device.

[0044] <Reinforcement Material> This electrolyte membrane includes a reinforcement material. The reinforcement material may be placed inside the electrolyte membrane or on the surface of the electrolyte membrane.

[0045] The reinforcing material is composed of polyetheretherketone (PEEK). The polyetheretherketone content in the reinforcing material is preferably 90% by mass or more, more preferably 95% by mass or more, and may be 100% by mass. Polyetheretherketone is preferred because it has a high modulus of elasticity and is resistant to deformation, and because it makes it easy to reduce the diameter of the warp and weft threads that make up the woven fabric. Aromatic polyetheretherketone is preferred. Aromatic polyetheretherketone refers to a polyetheretherketone that contains an aromatic ring (such as a benzene ring), as well as two ether bonds and a carbonyl bond as a unit. Preferably, the polyetheretherketone consists of a unit in which three benzene rings are linked by an ether bond, an ether bond, and a carbonyl bond, in that order.

[0046] Examples of reinforcing materials include porous materials, fibers, woven fabrics, and nonwoven fabrics, and woven fabrics are preferred because they exhibit superior effects compared to those described herein.

[0047] The woven fabric is composed of warp threads and weft threads. The denier count of the warp threads and the weft threads constituting the woven fabric are preferably 2.0 or higher, more preferably 3.0 or higher, even more preferably 4.0 or higher, and particularly preferably 5.0 or higher, in terms of superior strength and dimensional stability of the electrolyte membrane. The denier count of the warp threads and the weft threads constituting the woven fabric are preferably 60.0 or lower, more preferably 20.0 or lower, even more preferably 15.0 or lower, particularly preferably 10.0 or lower, and most preferably 9.0 or lower, in terms of further reducing the electrolysis voltage when applied to an electrolytic device. The denier count of the warp threads and weft threads constituting the woven fabric is preferably 2.0 to 60.0, more preferably 3.0 to 20.0, even more preferably 3.0 to 15.0, even more preferably 3.0 to 10.0, particularly preferably 4.0 to 10.0, and most preferably 5.0 to 9.0. The denier count is the value obtained by expressing the mass of 9,000 m of yarn in grams (g / 9000 m).

[0048] The diameters of the warp and weft threads constituting the woven fabric are preferably 40 μm or less, more preferably 30 μm or less, even more preferably 28 μm or less, and particularly preferably 25 μm or less. The diameters of the warp and weft threads constituting the woven fabric are preferably 8 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, and particularly preferably 23 μm or more. The diameters of the warp and weft threads constituting the woven fabric are preferably 8 μm or more and 40 μm or less, more preferably 12 μm or more and 30 μm or less, even more preferably 15 μm or more and 28 μm or less, particularly preferably 20 μm or more and 28 μm or less, and most preferably 23 μm or more and 25 μm or less. The above diameters may be measured from the cross-section of the electrolyte membrane or determined by calculation. When measuring the warp thread diameter from a cross-section of this electrolyte membrane, the thread diameter is the arithmetic mean of the diameters of 10 different warp threads, arbitrarily selected based on a magnified image (e.g., 100x magnification) of the cross-section of the electrolyte membrane obtained using a microscope, on a plane perpendicular to the direction in which the warp threads extend. If the cross-sectional shape of the warp thread is not circular, the area of ​​the cross-section is calculated, and the diameter of the circle that gives that area is taken as the diameter of the warp thread. The weft thread diameter can be measured using the same method as for measuring the warp thread diameter.

[0049] When calculating the yarn diameter, the value used is calculated from the denier number and the density of the materials constituting the warp and weft threads, assuming that the cross-sectional shapes of the warp and weft threads are perfect circles. Specifically, the value calculated by the following formula (D1) is used.

[0050]

[0051] In the above formula (D1), d represents the denier number. In formula (D1), D represents the diameter of the yarn, and its unit is μm. In formula (D1), π represents pi. In formula (D1), ρ represents the density of the material constituting the yarn, and its unit is g / cm³. ３ The density of PEEK is 1.30 g / cm³. ３ Use this.

[0052] The warp and weft threads that make up the woven fabric may consist of either monofilaments, which are made up of one filament, or multifilaments, which are made up of two or more filaments, with monofilaments being preferred.

[0053] The density of the warp and weft threads constituting the woven fabric is preferably 100 threads / inch or more, more preferably 105 threads / inch or more, even more preferably 110 threads / inch or more, even more preferably 130 threads / inch or more, particularly preferably 150 threads / inch or more, and most preferably 200 threads / inch or more, in order to independently increase the dimensional change rate in the film thickness direction described later and to further enhance the effects of this disclosure. Furthermore, in order to further reduce the electrolytic voltage when applied to an electrolytic device, a density of 350 threads / inch or less is preferred, more preferably 300 threads / inch or less, and even more preferably 250 threads / inch or less. The density of the warp and weft threads constituting the woven fabric is preferably 100 threads / inch or more and 350 threads / inch or less, more preferably 105 threads / inch or more and 300 threads / inch or less, even more preferably 110 threads / inch or more and 300 threads / inch or less, particularly preferably 150 threads / inch or more and 250 threads / inch or less, and most preferably 200 threads / inch or more and 250 threads / inch or less. The density of the warp and weft threads constituting the woven fabric is determined by the following method. First, for the warp threads, 100 adjacent warp threads are selected from the optical microscope image observed from the normal direction of the surface of the solid polymer electrolyte membrane, and the distance between the two outermost warp threads is measured five times at different locations, and the arithmetic mean of the distances is calculated. Using the obtained arithmetic mean, the density of the warp threads (unit: threads / inch) is calculated. For the weft threads, 100 adjacent weft threads are selected from an optical microscope image observed from the normal direction of the surface of the solid polymer electrolyte membrane. The distance between the two outermost weft threads is measured five times at different locations, and the arithmetic mean of the distances is calculated. The density of the weft threads (in units of threads / inch) is then calculated using the obtained arithmetic mean. In the case of a multifilament thread, the above measurement is performed on each spaced-out thread, not on the number of filaments that make up the thread.

[0054] It is also preferable that the warp and weft threads constituting the woven fabric be composed of polyetheretherketone. Furthermore, it is also preferable that the woven fabric be composed solely of warp and weft threads composed of polyetheretherketone.

[0055] The warp and weft threads that make up the woven fabric are preferably made of slit yarn, as this offers superior durability and strength.

[0056] In the woven fabric, it is preferable that the warp and weft threads are approximately perpendicular. Approximately perpendicular means that the angle between the warp and weft threads is 90 ± 10 degrees. Furthermore, the structure of the woven fabric is not particularly limited, and examples include plain weave, twill weave, and satin weave, with plain weave being preferred.

[0057] The basis weight of the woven fabric is 6.0 g / m², chosen for its excellent balance of strength and handling properties for this electrolyte membrane. ２ The above is preferable, and 7.50 g / m ２ The above is more preferable, 8.0 g / m ２ The above is even more preferable, 10.0 g / m ２ The above is particularly preferable. The basis weight of the woven fabric is 40.0 g / m². ２ The following is preferable: 20.0 g / m ２ The following is more preferable: 15.0 g / m ２ The following is even more preferable. The basis weight of the woven fabric is determined by the method described in the Examples section below.

[0058] Furthermore, the opening ratio of the woven fabric is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more, from the viewpoint that the electrolytic voltage when applied to an electrolytic device can be further reduced. The opening ratio of the woven fabric is preferably 90% or less, more preferably 80% or less, even more preferably 75% or less, particularly preferably 70% or less, and most preferably 68% or less, from the viewpoint that the strength of the electrolyte membrane is superior. The opening ratio of the woven fabric is preferably 50% or more and 90% or less, more preferably 55% or more and 80% or less, even more preferably 55% or more and 75% or less, even more preferably 60% or more and 70% or 55% or more and 68% or less, and particularly preferably 60% or more and 68% or less. The opening ratio of the woven fabric is calculated by the following formula (ε) based on the average diameter R1 of the yarn and the average spacing P1 between adjacent yarns (hereinafter also referred to as "pitch P1"). In particular, when the average diameters and average spacings of the warp and weft threads are different, the opening ratio of the woven fabric is calculated by the following formula (ε1), based on the average diameter R11 of the warp threads, the average spacing P11 between adjacent warp threads (hereinafter also referred to as "pitch P11"), the average diameter R12 of the weft threads, and the average spacing P12 between adjacent weft threads (hereinafter also referred to as "pitch P12"). Here, R1, R11, and R12 are the thread diameters measured by the method described above. Pitch P1, P11, and P12 are calculated using the arithmetic mean of the spacing between 10 points at arbitrarily selected different locations based on a magnified image (e.g., 100x) of the cross-section of the solid polymer electrolyte membrane obtained using a microscope. Opening ratio of woven fabric (%) = [P1 / (P1 + R1)] ２ × 100 (ε) Open area ratio of woven fabric (%) = [P11 / (P11+R11)] [P12 / (P12+R12)] × 100 (ε1)

[0059] The reinforcing material content is preferably 6.0% by mass or more relative to the total mass of the electrolyte membrane, preferably 7.0% by mass or more, and more preferably 7.5% by mass or more, from the viewpoint of superior effects of this disclosure. The reinforcing material content is preferably 15.0% by mass or less, more preferably 10.0% by mass or less, even more preferably 9.0% by mass or less, and particularly preferably 8.0% by mass or less, relative to the total mass of the electrolyte membrane, from the viewpoint of improving the proton conductivity of the electrolyte membrane and further reducing the electrolysis voltage when applied to an electrolytic device. The reinforcing material content is preferably 6.0% by mass or more and 15.0% by mass or less, more preferably 7.0% by mass or more and 10.0% by mass or less, even more preferably 7.5% by mass or more and 9.0% by mass or less, and particularly preferably 7.5% by mass or more and 8.0% by mass or less, relative to the total mass of the electrolyte membrane. The reinforcing material content is determined by the method described in the Examples section below.

[0060] The following combinations of denier count and density of the warp and weft threads constituting the woven fabric are preferable from the viewpoint of dimensional change rate in the film thickness direction and airtightness: - A combination in which the denier count is 2.0 or more and 60.0 or less, and the density is 100 threads / inch or more and 350 threads / inch or less. - A combination in which the denier count is 3.0 or more and 20.0 or less, and the density is 105 threads / inch or more and 300 threads / inch or less. - A combination in which the denier count is 3.0 or more and 10.0 or less, and the density is 110 threads / inch or more and 300 threads / inch or less. - A combination in which the denier count is 4.0 or more and 10.0 or less, and the density is 150 threads / inch or more and 250 threads / inch or less. - A combination in which the denier count is 5.0 or more and 9.0 or less, and the density is 200 threads / inch or more and 250 threads / inch or less.

[0061] From the viewpoint of dimensional change rate in the film thickness direction and airtightness, the following combinations of denier counts for the warp and weft threads constituting the woven fabric and the opening ratio of the woven fabric are preferred: - A combination in which the denier count is 2.0 or more and 60.0 or less, and the opening ratio is 50% or more and 90% or less. - A combination in which the denier count is 3.0 or more and 20.0 or less, and the opening ratio is 55% or more and 80% or less. - A combination in which the denier count is 3.0 or more and 10.0 or less, and the opening ratio is 55% or more and 68% or less. - A combination in which the denier count is 4.0 or more and 10.0 or less, and the opening ratio is 55% or more and 68% or less. - A combination in which the denier count is 5.0 or more and 9.0 or less, and the opening ratio is 55% or more and 68% or less.

[0062] <Physical Properties, etc.> (Film Thickness) The film thickness of this electrolyte membrane is preferably 20 μm or more, more preferably 40 μm or more, even more preferably 50 μm or more, and particularly preferably 60 μm or more, from the viewpoint of the mechanical strength of the electrolyte membrane. The film thickness of this electrolyte membrane is preferably 150 μm or less, more preferably 130 μm or less, and even more preferably 90 μm or less, from the viewpoint of being able to further reduce the electrolysis voltage when applied to an electrolytic device. In particular, the film thickness of this electrolyte membrane is preferably 20 to 150 μm, more preferably 50 to 150 μm or 40 to 130 μm, even more preferably 50 to 90 μm, and particularly preferably 50 to 80 μm, from the viewpoint of a higher rate of dimensional change in the film thickness direction described later, which further enhances the effects of this disclosure. The film thickness of this electrolyte membrane is measured using an image obtained by measuring a cross-section cut in a plane parallel to the film thickness direction with an optical microscope, and is the arithmetic mean of any 20 locations.

[0063] (Dimensional change rate in the film thickness direction) The dimensional change rate in the film thickness direction of the electrolyte membrane, as determined by the following formula (Z), is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and most preferably 90% or more, from the viewpoint of superior effects of this disclosure. The dimensional change rate in the film thickness direction of the electrolyte membrane, as determined by the following formula (Z), is preferably 120% or less, more preferably 100% or less, and even more preferably 95% or less, from the viewpoint of preventing damage (e.g., cracking) to the catalyst layer applied to the surface. The dimensional change rate in the film thickness direction of the electrolyte membrane, as determined by the following formula (Z), is preferably 60 to 120%, more preferably 70 to 120%, even more preferably 80 to 120%, most preferably 80 to 100%, and most preferably 90 to 100%, from the viewpoint of airtightness.

[0064] Formula (Z) Percentage change in the direction of film thickness (%) = 100 × (T2 - T1) / T1 T1: Film thickness of the electrolyte membrane obtained by leaving the dry electrolyte membrane standing at 23°C for 16 hours T2: Film thickness of the electrolyte membrane obtained by immersing the electrolyte membrane obtained in T1 in 95°C water for 1 hour Details of the method in T1 and details of the immersion method in T2 are as described in the Examples section below. The method for measuring the film thickness of the electrolyte membrane in T1 and the method for measuring the film thickness of the electrolyte membrane in T2 are the same as the method for measuring the film thickness of the electrolyte membrane described above.

[0065] (Water Content) The water content of the electrolyte membrane, as determined by the following formula (W), is preferably 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more, from the viewpoint of superior effects of this disclosure. The water content of the electrolyte membrane, as determined by the following formula (W), is preferably 150% or less, more preferably 120% or less, and even more preferably 100% or less, from the viewpoint of mechanical strength of the electrolyte membrane.

[0066] Formula (W) Moisture content (%) = 100 × (W1 - W2) / W2 W1: Mass of the wet electrolyte membrane obtained by immersing the electrolyte membrane in water at 95°C for 1 hour W2: Mass of the dry electrolyte membrane obtained by drying the wet electrolyte membrane obtained in W1 at 90°C under vacuum for 16 hours Details of the immersion method in W1 and details of the drying method in W2 are described in the Examples section below.

[0067] <Applications> This electrolyte membrane is suitably used in water electrolysis devices (specifically, solid polymer water electrolysis devices). Furthermore, this electrolyte membrane can be used in electrolytic hydrogenation devices for aromatic compounds (e.g., toluene).

[0068] <Method for manufacturing solid polymer electrolyte membranes> As a method for manufacturing this electrolyte membrane, for example, one can produce a membrane (hereinafter also called a "precursor membrane") containing a polymer of a fluorine-containing monomer (hereinafter also called a "fluorine-containing monomer (I')") having a group that can be converted into an ion exchange group (hereinafter also called a "fluorine-containing polymer (I')") and a reinforcing material, and then produce the membrane by converting the groups in the precursor membrane that can be converted into ion exchange groups into ion exchange groups.

[0069] A preferred embodiment of the method for producing a precursor film is a method in which a laminate, in which a fluorine-containing polymer (I') is arranged on both sides of a reinforcing material (preferably a woven fabric), is sandwiched between transfer substrates such as a film with a melting point of 70 to 180°C, and then heated and pressed. Specific examples of transfer substrates include polyethylene film, polypropylene film, polystyrene film, and polyethylene terephthalate film. The transfer substrate may be a single-layer transfer substrate or a multi-layer transfer substrate having two or more layers. When the transfer substrate is a multi-layer structure, each layer may be made of the same material or of different materials. Specific examples of materials constituting each layer are as described above.

[0070] As mentioned above, the reinforcing material is used, so its explanation will be omitted. The reinforcing material is used so that its content relative to the total mass of the electrolyte membrane is 6.0% by mass or more.

[0071] As the fluorine-containing polymer (I'), a polymer of a fluorine-containing monomer having a group that can be converted to a sulfonic acid-type functional group (hereinafter also referred to as "fluorine-containing polymer (S')") is preferred, and a copolymer polymer of a fluorine-containing olefin and a monomer having a group that can be converted to a sulfonic acid-type functional group and a fluorine atom is more preferred. The fluorine-containing polymer (S') will be described in detail below.

[0072] Methods for copolymerizing fluorine-containing polymers (S') can include known methods such as solution polymerization, suspension polymerization, and emulsion polymerization.

[0073] Examples of fluorine-containing olefins include those exemplified above, and TFE is preferred due to its superior monomer production cost, reactivity with other monomers, and the characteristics of the resulting fluorine-containing polymer (S). Fluorine-containing olefins may be used individually or in combination of two or more. The content of units based on fluorine-containing olefins relative to the total units in the fluorine-containing polymer (S') is preferably 65 to 95 mol%.

[0074] Examples of fluorine-containing monomers (S') include compounds having one or more fluorine atoms in the molecule, possessing an ethylenically active double bond, and having a group that can be converted to a sulfonic acid-type functional group. As a fluorine-containing monomer (S'), the compound represented by formula (2) is preferred due to its superior manufacturing cost, reactivity with other monomers, and the characteristics of the resulting fluorine-containing polymer (S). Formula (2) CF ２ =CF - L - (A) ｎ The definitions of L and n in formula (2) are as described above. When n is 2, the two A groups may be the same or different. A is a group that can be converted to a sulfonic acid type functional group. The group that can be converted to a sulfonic acid type functional group is preferably a functional group that can be converted to a sulfonic acid type functional group by hydrolysis. A specific example of a group that can be converted to a sulfonic acid type functional group is -SO ２ F, -SO ２ Cl, -SO ２ Br is one example.

[0075] The compounds represented by formula (2) are preferably those represented by formula (2-1), formula (2-2), formula (2-3), and formula (2-4). Formula (2-1) CF ２ =CF-O-R ｆ１ -A Formula (2-2) CF ２ =CF-R ｆ１ -A

[0076]

[0077] R in the formula ｆ１ , R ｆ２ , r and A are defined as described above.

[0078]

[0079] R in the formula ｆ１ , R ｆ２ , R ｆ３ , r, m and A are defined as described above.

[0080] As the compound represented by formula (2-1) and the compound represented by formula (2-2), the compound represented by formula (2-5) is preferred. Formula (2-5) CF ２ =CF-(CF ２ ) ｘ -(OCF ２ CFY) ｙ -O-(CF ２ ) ｚ -SO ２ F The definitions of x, y, z and Y in the formula are as described above.

[0081] Specific examples of the compound represented by formula (2-1) include the following compounds. In the formula, w is an integer from 1 to 8, and x is an integer from 1 to 5. CF ２ =CF-O-(CF ２ ) ｗ -SO ２ F CF ２ =CF-O-CF ２ CF(CF ３ )-O-(CF ２ ) ｗ -SO ２ F CF ２ =CF-[O-CF ２ CF(CF ３ )] ｘ -SO ２ F

[0082] Specific examples of the compound represented by formula (2-2) include the following compounds. In the formula, w is an integer from 1 to 8. CF ２ =CF-(CF ２ ) ｗ -SO ２ F CF ２ =CF-CF ２-O-(CF ２ ) ｗ -SO ２ F

[0083] Of the compounds represented by formula (2-3), the compound represented by formula (2-3-1) is preferred.

[0084]

[0085] R in the formula ｆ４ , R ｆ５ The definitions of r and A are as described above.

[0086] Specific examples of compounds represented by formula (2-3-1) include the following:

[0087]

[0088] Of the compounds represented by formula (2-4), the compound represented by formula (2-4-1) is preferred.

[0089]

[0090] R in the formula ｆ１ , R ｆ２ The definition of A is as stated above.

[0091] Specific examples of compounds represented by formula (2-4-1) include the following:

[0092]

[0093] The fluorine-containing monomer (S') may be used alone or in combination of two or more types. The content of units based on the fluorine-containing monomer (S') relative to the total units of the fluorine-containing polymer (S') is preferably 5 to 355 mol%. In addition to the fluorine-containing olefin and fluorine-containing monomer (S'), other monomers may also be used in the production of the fluorine-containing polymer (S'). Examples of other monomers include those exemplified above.

[0094] The ion exchange capacity of the fluorine-containing polymer (I') can be adjusted by changing the content of groups that can be converted into ion exchange groups in the fluorine-containing polymer (I').

[0095] Specific examples of methods for converting groups in a precursor film that can be converted into ion exchange groups include methods of subjecting the precursor film to hydrolysis or acidification. Among these, a method of contacting the precursor film with an alkaline aqueous solution is preferred.

[0096] Specific examples of methods for bringing the precursor film into contact with an alkaline aqueous solution include immersing the precursor film in the alkaline aqueous solution and spraying the alkaline aqueous solution onto the surface of the precursor film. The temperature of the alkaline aqueous solution is preferably 30 to 100°C, and particularly preferably 40 to 100°C. The contact time between the precursor film and the alkaline aqueous solution is preferably 3 to 150 minutes, and particularly preferably 5 to 50 minutes.

[0097] The alkaline aqueous solution preferably contains an alkali metal hydroxide, a water-soluble organic solvent, and water. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide. In this specification, a water-soluble organic solvent is an organic solvent that dissolves readily in water, and specifically, an organic solvent with a solubility of 0.1 g or more in 1,000 ml of water (20°C) is preferred, and an organic solvent with a solubility of 0.5 g or more is particularly preferred. The water-soluble organic solvent preferably contains at least one selected from the group consisting of aprotic organic solvents, alcohols, and amino alcohols, and is particularly preferred to contain an aprotic organic solvent. The water-soluble organic solvent may be used alone or in combination of two or more.

[0098] Specific examples of aprotic organic solvents include dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone, with dimethyl sulfoxide being preferred. Specific examples of alcohols include methanol, ethanol, isopropanol, butanol, methoxyethoxyethanol, butoxyethanol, butylcarbitol, hexyloxyethanol, octanol, 1-methoxy-2-propanol, and ethylene glycol. Specific examples of amino alcohols include ethanolamine, N-methylethanolamine, N-ethylethanolamine, 1-amino-2-propanol, 1-amino-3-propanol, 2-aminoethoxyethanol, 2-aminothioethoxyethanol, and 2-amino-2-methyl-1-propanol.

[0099] The concentration of alkali metal hydroxide is preferably 1 to 60% by mass, and particularly preferably 3 to 55% by mass, in the alkaline aqueous solution. The content of water-soluble organic solvent is preferably 1 to 60% by mass, and particularly preferably 3 to 55% by mass, in the alkaline aqueous solution. The concentration of water is preferably 39 to 80% by mass, in the alkaline aqueous solution.

[0100] After contact between the precursor film and the alkaline aqueous solution, a treatment to remove the alkaline aqueous solution may be performed. One method for removing the alkaline aqueous solution is to wash the precursor film that has been in contact with the alkaline aqueous solution with water.

[0101] After contacting the precursor film with an alkaline aqueous solution, the resulting film may be contacted with an acidic aqueous solution to convert the ion exchange groups to the acidic form. Specific examples of methods for contacting the precursor film with an acidic aqueous solution include immersing the precursor film in the acidic aqueous solution and spraying the acidic aqueous solution onto the surface of the precursor film. The acidic aqueous solution preferably contains an acid component and water. Specific examples of the acid component include hydrochloric acid and sulfuric acid.

[0102] [Membrane Electrode Assembly] The membrane electrode assembly of the present disclosure includes an anode having a catalyst layer, a cathode having a catalyst layer, and the electrolyte membrane described above disposed between the anode and the cathode. The electrolyte membrane is as described above, so no further explanation is given.

[0103] Figure 1 is a cross-sectional view showing an example of a membrane electrode assembly of the present disclosure. The membrane electrode assembly 20 includes an anode 22 having a catalyst layer 26 and a gas diffusion layer 28, a cathode 24 having a catalyst layer 26 and a gas diffusion layer 28, and a solid polymer electrolyte membrane 10 disposed between the anode 22 and the cathode 24 in contact with the catalyst layer 26.

[0104] <Anode and Cathode> The anode and cathode each have a catalyst layer. In the example in Figure 1, the anode 22 and cathode 24 each have a catalyst layer 26 and a gas diffusion layer 28. In at least one of the anode 22 and cathode 24, there may be a region where a portion of the gas diffusion layer 28 and the catalyst layer 26 overlap in the thickness direction. Also, in at least one of the anode 22 and cathode 24, the catalyst layer 26 may be omitted, and the gas diffusion layer 28 may perform the role of the catalyst layer 26.

[0105] Specific examples of catalyst layers include layers containing a catalyst and a polymer having ion exchange groups. Specific examples of catalysts include supported catalysts in which a catalyst containing platinum, a platinum alloy, or platinum having a core-shell structure is supported on a carbon support, ruthenium oxide catalysts, iridium oxide catalysts, ruthenium-containing composite oxides, iridium-containing composite oxides, ruthenium oxide-containing catalysts having a core-shell structure, and iridium oxide-containing catalysts having a core-shell structure. Carbon black powder is used as the carbon support. Fluorine-containing polymers having ion exchange groups are used as the polymers having ion exchange groups. The catalyst included in the anode-side catalyst layer is preferably one or more catalysts selected from the group consisting of ruthenium oxide catalysts, iridium oxide catalysts, ruthenium-containing composite oxides, iridium-containing composite oxides, ruthenium oxide-containing catalysts having a core-shell structure, and iridium oxide-containing catalysts having a core-shell structure. The supported catalyst is preferred as the catalyst included in the cathode-side catalyst layer.

[0106] The gas diffusion layer has the function of uniformly diffusing gas into the catalyst layer and also functions as a current collector. Specific examples of the gas diffusion layer include carbon paper, carbon cloth, carbon felt, and metal mesh. For the gas diffusion layer on the anode side, a metal mesh is preferably used. The metal material constituting the metal mesh is preferably a metal with high corrosion resistance, such as titanium, zirconium, niobium, and tantalum, with titanium being preferred. The gas diffusion layer may be treated to be water-repellent with PTFE or the like. If the gas diffusion layer is a metal mesh, its surface may be coated with a precious metal such as platinum. In the film electrode assembly shown in Figure 1, the gas diffusion layer 28 is included, but the gas diffusion layer is an arbitrary component and does not have to be included in the film electrode assembly. Furthermore, as described above, the gas diffusion layer may contain the catalyst mentioned above.

[0107] The film thickness of the anode and cathode is preferably 5 to 100 μm, more preferably 5 to 50 μm, even more preferably 5 to 30 μm, and particularly preferably 5 to 15 μm, independently of each other. The film thickness of the anode and cathode is measured using an image obtained by measuring a cross-section of the film electrode assembly cut in a plane parallel to the film thickness direction with an optical microscope, and is the arithmetic mean value at any 20 locations.

[0108] <Method for Manufacturing a Membrane Electrode Assembly> Examples of methods for manufacturing a membrane electrode assembly include forming a catalyst layer on the electrolyte membrane and then sandwiching the resulting assembly between gas diffusion layers, and forming a catalyst layer on a gas diffusion layer to form electrodes (anode, cathode) and sandwiching the electrolyte membrane between these electrodes. Methods for manufacturing the catalyst layer include applying a catalyst layer forming coating solution to a predetermined position on the electrolyte membrane and drying it as needed. Alternatively, a catalyst layer forming coating solution may be applied to a substrate and dried to form the catalyst layer on the substrate, after which the formed catalyst layer is transferred to the electrolyte membrane. The catalyst layer forming coating solution may be a liquid in which a polymer having ion exchange groups and a catalyst are dispersed in a dispersion medium.

[0109] <Applications> The solid polymer electrolyte membrane of this disclosure can be used for water electrolysis. The membrane electrode assembly of this disclosure is suitably used in water electrolysis apparatuses (specifically, solid polymer type water electrolysis apparatuses). Furthermore, the membrane electrode assembly of this disclosure can be used in electrolytic hydrogenation apparatuses for aromatic compounds (e.g., toluene).

[0110] The water electrolysis apparatus of the present disclosure includes the membrane electrode assembly described above. Specifically, the water electrolysis apparatus of the present disclosure preferably includes the membrane electrode assembly described above, a water supply unit that supplies water to the anode side, and a power supply unit that is electrically connected to the anode and cathode. In the water electrolysis apparatus of the present disclosure, when a DC voltage is applied by the power supply unit while water is supplied to the anode side by the water supply unit, water decomposes on the anode side, generating oxygen and protons. On the cathode side, protons that have moved to the catalyst layer side of the cathode via the electrolyte membrane gain electrons, generating hydrogen. The water electrolysis apparatus of the present disclosure may have the same configuration as known water electrolysis apparatuses, except for having the above-described components (for example, an oxygen recovery member for recovering generated oxygen, a hydrogen recovery member for recovering generated hydrogen).

[0111] [Electrolytic Hydrogenation Apparatus] The electrolytic hydrogenation apparatus of this disclosure includes the above-described membrane electrode assembly. The electrolytic hydrogenation apparatus of this disclosure may have the same configuration as known electrolytic hydrogenation apparatuses, except for including the above-described membrane electrode assembly (for example, an oxygen recovery member for recovering generated oxygen, a hydrogen recovery member for recovering generated hydrogen). The electrolytic hydrogenation apparatus of this disclosure can suitably electrolytically hydrogenate aromatic compounds such as benzene, toluene, and naphthalene.

[0112] [Method for producing hydrogen] The method for producing hydrogen according to this disclosure involves electrolyzing water (electrolyte) using the water electrolysis apparatus described above to produce hydrogen. With the method for producing hydrogen according to this disclosure, hydrogen can be produced efficiently because the water electrolysis apparatus of this disclosure is used.

[0113] The present disclosure will be explained in detail below with reference to examples. Examples 1 to 5 are embodiments, and Examples 6 to 9 are comparative examples. However, the present disclosure is not limited to these examples.

[0114] [Measurement Method] <Ion Exchange Capacity of Fluorine-Containing Polymer> A fluorine-containing polymer was left to stand for 24 hours in a glove box flowing dry nitrogen, and its dry mass was measured. Then, the fluorine-containing polymer was immersed in a 2 mol / L sodium chloride aqueous solution at 60°C for 1 hour. After washing the fluorine-containing polymer with ultrapure water, it was removed, and the ion exchange capacity X (milliequivalents / gram dry resin) of the fluorine-containing polymer was determined by titrating the solution in which the fluorine-containing polymer had been immersed with a 0.1 mol / L sodium hydroxide aqueous solution. Note that "meq / g" means "milliequivalents / g dry resin," which is the unit of ion exchange capacity.

[0115] <Fabric weight, yarn diameter, opening ratio, and density> The raw fabric roll used was cut into 20 x 20 cm pieces and its mass was measured. The above measurement was performed five times, and the arithmetic mean was used to determine the fabric weight (g / m²). ２ The following was determined: the yarn diameter, opening ratio, and density were calculated using the method described above.

[0116] <Woven Fabric Content> The content (mass %) of woven fabric (reinforcement material) relative to the total mass of the solid polymer electrolyte membrane was calculated using the following formula (C), where C1 is the basis weight of the woven fabric and C2 is the basis weight of the fluorine-containing polymer. The basis weight of the fluorine-containing polymer is CF ２ =CF ２ The density of the fluorine-containing polymer obtained by copolymerizing the monomer (Y) represented by formula (X) described later is uniformly 2.00 g / cm³. ３ The formula was calculated from the total film thickness of the films used in each example. The results are shown in Table 1. In Table 1, "Woven fabric content (mass%)" is used as an abbreviation. Formula (C) Woven fabric content (mass%) = 100 × C1 / (C1 + C2)

[0117] <Moisture Content> The solid polymer electrolyte membranes for each example were immersed in 95°C water for 1 hour, and then cooled to 25°C. The membranes were removed, and the water adhering to the surface of the membranes was wiped off with filter paper to obtain wet electrolyte membranes. The mass W1 of the obtained wet electrolyte membranes was measured. Next, the obtained wet electrolyte membranes were placed in a glove box through which dry nitrogen (dew point below -70°C) was circulated, and dried at 90°C for 16 hours to obtain dry electrolyte membranes. The mass W2 of the obtained dry electrolyte membranes was measured inside the glove box. Using masses W1 and W2, the moisture content (%) was calculated using the following formula (W). The results are shown in Table 1. Formula (W) Moisture content (%) = 100 × (W1 - W2) / W2

[0118] <Film Thickness> The film thickness of the solid polymer electrolyte membrane was determined using the method described above.

[0119] <Dimensional change rate in the film thickness direction> After allowing each example of the solid polymer electrolyte membrane to stand at 23°C for 16 hours, the film thickness T1 was measured using the method described above. Next, the membrane was immersed in 95°C water for 1 hour, and then cooled until the water temperature reached 25°C. The membrane was removed, and the water adhering to the surface of the membrane was wiped off with filter paper. The film thickness T2 of the obtained membrane was measured using the method described above. Using film thickness T1 and film thickness T2, the dimensional change rate (%) in the film thickness direction was calculated using the following formula (Z). The results are shown in Table 1. Formula (Z) Dimensional change rate (%) in the film thickness direction = 100 × (T2 - T1) / T1

[0120] [Evaluation Method] <Airtightness> First, to ensure sufficient water absorption of the solid polymer electrolyte membrane and both electrode ionomers, pure water with a conductivity of 1.0 μS / cm or less, at a temperature of 80°C and atmospheric pressure, was supplied to the anode and cathode sides at a flow rate of 50 mL / min for 12 hours. After that, the cathode side was purged with nitrogen. After nitrogen purging, pure water with a conductivity of 1.0 μS / cm or less, at a temperature of 80°C and atmospheric pressure, was supplied to the anode side at a flow rate of 50 mL / min, while maintaining a generated gas pressure of 3 MPa on the cathode side. A current density of 2 A / cm² was then supplied using a Kikusui Electronics PWR1600L DC power supply. ２Electrolysis was started. The time from the start of electrolysis until leakage occurred was evaluated according to the following criteria. The longer the time until leakage occurs, the better the airtightness of the solid polymer electrolyte membrane during water electrolysis. In practical terms, a rating of B or higher is preferable. S: 500 hours or more A: 300 hours or more but less than 500 hours B: 200 hours or more but less than 300 hours C: 100 hours or more but less than 200 hours D: Less than 100 hours

[0121] [Production of fluorine-containing polymer (S'-1)] CF ２ =CF ２ The monomer (X) represented by the following formula (X) was copolymerized to obtain a fluorine-containing polymer (S'-1) (ion exchange capacity: 1.25 milliequivalents / gram dry resin). The ion exchange capacity represents the ion exchange capacity of the fluorine-containing polymer obtained when hydrolyzed by the procedure described later, and the same applies to each of the following examples. CF ２ = CF - O - CF ２ CF (CF ３ )-O-CF ２ CF ２ -SO ２ F ... (X)

[0122] [Production of fluorine-containing polymer (S'-2)] CF ２ =CF ２ The above monomer (X) was copolymerized to obtain a fluorine-containing polymer (S'-2) (ion exchange capacity: 1.40 milliequivalents / gram dry resin).

[0123] [Production of fluorine-containing polymer (S'-3)] CF ２ =CF ２ The above monomer (X) was copolymerized to obtain a fluorine-containing polymer (S'-3) (ion exchange capacity: 1.09 milliequivalents / gram dry resin).

[0124] [Production of film α1] A fluorine-containing polymer (S'-1) was molded by melt extrusion to obtain film α1 (film thickness: 45 μm) made of the fluorine-containing polymer (S'-1).

[0125] [Production of Film α2] A fluorine-containing polymer (S'-2) was molded by melt extrusion to obtain Film α2 (film thickness: 45 μm) made of the fluorine-containing polymer (S'-2).

[0126] [Manufacturing of Film α3] A fluorine-containing polymer (S'-1) was molded by melt extrusion to obtain Film α3 (film thickness: 30 μm) made of the fluorine-containing polymer (S'-1).

[0127] [Manufacturing of Film α4] A fluorine-containing polymer (S'-2) was molded by melt extrusion to obtain Film α4 (film thickness: 30 μm) made of the fluorine-containing polymer (S'-2).

[0128] [Manufacturing of Film α5] A fluorine-containing polymer (S'-1) was molded by melt extrusion to obtain Film α5 (film thickness: 25 μm) made of the fluorine-containing polymer (S'-1).

[0129] [Manufacturing of Film α6] A fluorine-containing polymer (S'-3) was molded by melt extrusion to obtain Film α6 (film thickness: 40 μm) made of a fluorine-containing polymer (S'-1).

[0130] [Manufacturing of Woven Fabric A1] Woven fabric A1 was obtained by plain weaving 13.3 denier yarn made of polyetheretherketone (PEEK) for both the warp and weft threads, with a yarn density of 10⁹ threads / inch. The basis weight of woven fabric A1 was 12.7 g / m ２ The warp and weft threads were composed of slit yarn. The above PEEK had the following structure.

[0131]

[0132] [Manufacturing of Woven Fabrics A2 to A6] Woven fabrics A2 to A6 were manufactured in the same manner as woven fabric A1, except that the materials, diameter, and denier of the warp and weft threads were changed, and the yarn density and basis weight were adjusted to the values ​​shown in Table 1. In Table 1, PFA is tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (density 2.14 g / cm³). ３ ) means.

[0133] [Example 1] PET film / film α1 / woven fabric A1 / film α1 / PET film were layered in this order. Each layered component was subjected to a temperature of 200°C and a surface pressure of 30 MPa / m. ２ After heating and pressing the substrates in a flatbed press for 10 minutes, the transfer substrates on both sides were peeled off at a temperature of 50°C to obtain a precursor film. The precursor film was immersed in a solution of dimethyl sulfoxide / potassium hydroxide / water = 30 / 5.5 / 64.5 (mass ratio) at 95°C for 30 minutes to hydrolyze the groups in the precursor film that can be converted to sulfonic acid type functional groups, converting them to K-type sulfonic acid type functional groups, and then washed with water. Subsequently, the obtained film was immersed in 1M sulfuric acid to convert the terminal groups from K-type to H-type, and then dried to obtain the solid polymer electrolyte film of Example 1.

[0134] [Examples 2-9] Solid polymer electrolyte membranes of Examples 2-9 were obtained in the same manner as in Example 1, except that the film and woven fabric were changed as shown in Table 1.

[0135] [Manufacturing of Membrane Electrode Assembly] TFE and the above monomer (X) were copolymerized, and a polymer (ion exchange capacity: 1.10 milliequivalents / gram dry resin) was obtained by hydrolysis and acid treatment to obtain an acid-type polymer. This polymer was dispersed in a solvent of water / ethanol = 40 / 60 (mass%) at a solid content concentration of 25.8% to obtain a dispersion (hereinafter also referred to as "dispersion X"). To the obtained dispersion X (19.0 g), ethanol (0.52 g) and water (3.34 g) were added, and further, a specific surface area of ​​100 m² containing 76% by mass of iridium in the dispersion was obtained. ２ 13.0 g of iridium oxide catalyst (manufactured by Tanaka Kikinzoku Co., Ltd.) was added. The resulting mixture was treated with a planetary bead mill (rotation speed 300 rpm) for 30 minutes, then water (4.49 g) and ethanol (4.53 g) were added, and the mixture was further treated with a planetary bead mill (rotation speed 200 rpm) for 60 minutes to obtain an anode catalyst ink with a solid content concentration of 40% by mass. The anode catalyst ink was then applied to an ETFE sheet at an iridium concentration of 1.0 mg / cm³. ２ The material was coated using an applicator, dried at 80°C for 10 minutes, and then heat-treated at 150°C for 15 minutes to obtain an anode catalyst layer decal.

[0136] A supported catalyst (TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) (11 g), in which 46% by mass of platinum was supported on carbon powder, was mixed with water (59.4 g) and ethanol (39.6 g) and mixed and pulverized using an ultrasonic homogenizer to obtain a catalyst dispersion. To the catalyst dispersion, a mixture (29.2 g) was added, which consisted of dispersion X (20.1 g), ethanol (11 g), and Zeolora-H (manufactured by Nippon Zeon Co., Ltd.) (6.3 g) that had been pre-mixed and kneaded. Furthermore, water (3.66 g) and ethanol (7.63 g) were added to the obtained dispersion and mixed with paint conditioner for 60 minutes to obtain a cathode catalyst ink with a solid content concentration of 10.0% by mass. The cathode catalyst ink was applied to an ETFE sheet with a die coater, dried at 80°C, and then heat-treated at 150°C for 15 minutes to obtain a platinum content of 0.4 mg / cm². ２ A cathode catalyst layer decal was obtained.

[0137] In each example, the anode catalyst layer of the anode catalyst layer decal is placed on one side of the solid polymer electrolyte membrane, and the catalyst layer of the cathode catalyst layer decal is placed on the other side of the electrolyte membrane. The membrane is then heated and pressed at a press temperature of 150°C for 10 minutes at a pressure of 3 MPa to bond the anode catalyst layer, solid polymer electrolyte membrane, and cathode catalyst layer. After lowering the temperature to 70°C, the pressure is released and the membrane is removed. The ETFE sheets of the anode catalyst layer decal and cathode catalyst layer decal are then peeled off, resulting in an electrode area of ​​16 cm². ２ A film electrode assembly was obtained.

[0138] [Manufacturing of Water Electrolyzer] After heat-treating the obtained membrane electrode assembly at 150°C for 15 minutes, multiple sub-gaskets made of PPS (polyphenylene sulfide) and PEN (polyethylene naphthalate) were sandwiched around the periphery of the membrane electrode assembly, and the assembly was set in a water electrolysis evaluation jig EH50-25 (manufactured by Greenlight Innovation) to obtain a water electrolyzer. The above-mentioned liquid leakage evaluation was performed using the obtained water electrolyzer to evaluate its airtightness. The evaluation results are shown in Table 1.

[0139]

[0140] As shown in Table 1, it was confirmed that when using the electrolyte membrane of this disclosure, superior airtightness due to the solid polymer electrolyte membrane is achieved during high-pressure water electrolysis.

[0141] 10 Solid polymer electrolyte membrane 20 Membrane electrode assembly 22 Anode 24 Cathode 26 Catalyst layer 28 Gas diffusion layer

[0142] Furthermore, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-197650, filed on November 12, 2024, are incorporated herein by reference as disclosure of the present invention.

Claims

1. A solid polymer electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups and a reinforcing material, wherein the reinforcing material is composed of polyetheretherketone, the ion exchange capacity of the fluorine-containing polymer is 1.10 milliequivalents / gram dry resin or more, and the content of the reinforcing material is 6.0% by mass or more with respect to the total mass of the solid polymer electrolyte membrane.

2. The solid polymer electrolyte membrane according to claim 1, wherein the reinforcing material is a woven fabric.

3. The solid polymer electrolyte membrane according to claim 2, wherein the woven fabric is composed of warp threads and weft threads, and the density of the warp threads and the density of the weft threads are independently 110 threads / inch or more.

4. The solid polymer electrolyte membrane according to claim 1, wherein the thickness of the solid polymer electrolyte membrane is 50 to 150 μm.

5. The solid polymer electrolyte membrane according to claim 1, wherein the content of the reinforcing material is 8.0% by mass or less with respect to the total mass of the solid polymer electrolyte membrane.

6. The solid polymer electrolyte membrane according to claim 1, wherein the ion exchange group is a sulfonic acid type functional group.

7. The solid polymer electrolyte membrane according to claim 1, wherein the fluorine-containing polymer comprises units based on fluorine-containing olefins and units having sulfonic acid-type functional groups and fluorine atoms.

8. The solid polymer electrolyte membrane according to claim 7, wherein the unit having the sulfonic acid type functional group and the fluorine atom is a unit represented by formula (1). Formula (1) - [CF ２ -CF(-L-(SO ３ M) ｎ )]- L is an n+1 valent perfluorohydrocarbon group which may contain an etheric oxygen atom, M is a hydrogen atom, an alkali metal or a quaternary ammonium cation, and n is 1 or 2.

9. A solid polymer electrolyte membrane used in a water electrolysis apparatus, as described in claim 1.

10. A membrane electrode assembly comprising: an anode having a catalyst layer; a cathode having a catalyst layer; and a solid polymer electrolyte membrane according to any one of claims 1 to 9, disposed between the anode and the cathode.

11. A water electrolysis apparatus comprising the membrane electrode assembly described in claim 10.

12. An electrolytic hydrogenation apparatus comprising the membrane electrode assembly described in claim 10.

13. A method for producing hydrogen, comprising producing hydrogen by electrolyzing water using the water electrolysis apparatus described in claim 11.

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