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 chemical durability; 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, a reinforcing material, and a platinum-containing material, wherein: the reinforcing material is composed of polyether ether ketone; and the ion exchange capacity of the fluorine-containing polymer is 1.10 milliequivalents per gram of dry resin or more.

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] From the perspective of power-to-gas, that is, converting surplus electricity into gas for storage and utilization, the use of polymer electrolyte water electrolyzers (PEM-type water electrolyzers) is being considered. For example, Patent Document 1 discloses a polymer electrolyte water electrolyzer having a membrane electrode assembly including an anode and a cathode having a catalyst layer, and a polymer electrolyte membrane disposed between the anode and the cathode, and it is shown that the polymer electrolyte membrane includes a fluorine-containing polymer having ion exchange groups and a woven fabric.

[0003] International Publication No. 2022 / 050363

[0004] When a solid polymer electrolyte membrane is applied to a water electrolysis apparatus, the fluorine-containing polymer in the solid polymer electrolyte membrane may decompose due to OH radicals generated from compounds (particularly hydrogen peroxide) that are produced in the system during operation. Therefore, there is a need for a solid polymer electrolyte membrane with excellent chemical durability. The present inventors evaluated a water electrolysis apparatus having a solid polymer electrolyte membrane as described in Patent Document 1 and found that there is room for improvement in the chemical durability of the solid polymer electrolyte membrane.

[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 with excellent chemical durability, a membrane electrode assembly, a water electrolysis device, an electrolytic hydrogenation device, and a method for producing hydrogen.

[0006] The disclosure includes the following embodiments: [1] A solid polymer electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups, a reinforcing material, and a platinum-containing material, wherein the reinforcing material is composed of polyetheretherketone, and the ion exchange capacity of the fluorine-containing polymer is 1.10 milliequivalents / gram dry resin or more. [2] The solid polymer electrolyte membrane 1 cm ２ The mass of the above platinum-containing material per unit is 0.030 mg / cm³.２ The solid polymer electrolyte membrane described in [1] is as follows: [3] The solid polymer electrolyte membrane described in [1] or [2], wherein 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. [4] The solid polymer electrolyte membrane described in any of [1] to [3], wherein the dimensional change rate in the film thickness direction of the solid polymer electrolyte membrane, which can be determined by the following formula (Z), is 60% or more. Formula (Z) Dimensional change rate in the film thickness direction (%) = 100 × (T2 - T1) / T1 T1: Film thickness of the solid polymer electrolyte membrane obtained by standing the solid polymer electrolyte membrane at 23°C for 16 hours T2: Film thickness of the solid polymer electrolyte membrane obtained by immersing the solid polymer electrolyte membrane obtained in T1 in water at 95°C for 1 hour [5] The solid polymer electrolyte membrane described in any of [1] to [4], wherein the reinforcing material is a woven fabric. [6] The solid polymer electrolyte membrane described in any of [1] to [5], wherein the film thickness of the solid polymer electrolyte membrane is 50 to 150 μm. [7] The solid polymer electrolyte membrane according to any one of [1] to [6], wherein the ion exchange group is a sulfonic acid type functional group. [8] The solid polymer electrolyte membrane according to any one of [1] to [7], 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. [9] The solid polymer electrolyte membrane according to [8], 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.

[10] The solid polymer electrolyte membrane according to any one of [1] to [9] used in a water electrolysis device.

[11] An anode having a catalyst layer, a cathode having a catalyst layer, and the solid polymer electrolyte membrane according to any one of [1] to

[10] disposed between the anode and the cathode, including a membrane electrode assembly.

[12] A water electrolysis device including the membrane electrode assembly according to

[11] .

[13] An electrolytic hydrogenation device including the membrane electrode assembly according to

[11] .

[14] A method for producing hydrogen by electrolyzing water using the water electrolysis device according to

[12] .

[0007] According to an 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 chemical durability.

[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 include the following sulfonic acid type functional groups and carboxylic acid type functional groups. "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)"), a reinforcing material, and a platinum-containing material, wherein the reinforcing material is composed of polyetheretherketone, and the ion exchange capacity of the fluorine-containing polymer is 1.10 milliequivalents / gram dry resin or more. When this electrolyte membrane is applied to an electrolytic device and 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, since the ion exchange capacity of the fluorine-containing polymer (I) is 1.10 milliequivalents / gram dry resin or more, the water content when this electrolyte membrane is immersed in water is high, which is thought to make the electrolyte membrane more prone to expansion in the film thickness direction. As a result, when the electrolysis device is used, the electrolyte membrane expands in the direction of film thickness, increasing its thickness. This suppresses the permeation of gases (specifically hydrogen and oxygen) generated at the anode and cathode through the electrolyte membrane. This is thought to suppress the recombination reaction between hydrogen and oxygen on the platinum-containing material in the electrolyte membrane, thereby also suppressing the side reaction that generates OH radicals. Consequently, the decomposition of the fluorine-containing polymer in the electrolyte membrane by OH radicals is suppressed, resulting in superior chemical durability of the electrolyte membrane.

[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, and even more preferably 1.20 milliequivalents / gram dry resin or more and 1.43 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 standpoint 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, more preferably 2 or more, preferably 20 or less, and more preferably 10 or less.

[0019] L is preferably an n+1 valent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom, more 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, more preferably 2 or more, preferably 20 or less, and more 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, more preferably 2 or more, preferably 20 or less, and more 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, more preferably 2 or more, preferably 20 or less, and more 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, particularly preferably 5.0 or higher, and most preferably 10.0 or higher, in terms of superior strength, dimensional stability, and chemical durability 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, and particularly preferably 10.0 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 4.0 to 15.0, particularly preferably 5.0 to 15.0, and most preferably 10.0 to 15.0. 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, for example, 50 μm or less, 45 μm or less, 40 μm or less, and 30 μm or less, independently of each other. The diameters of the warp and weft threads constituting the woven fabric are preferably, for example, 8 μm or more, 15 μm or more, 20 μm or more, 23 μm or more, and 28 μm or more, independently of each other. The above diameters may be measured from the cross-section of the electrolyte membrane or determined by calculation. The diameters of the warp and weft threads constituting the woven fabric are preferably, for example, 8 to 50 μm, 15 to 45 μm, 20 to 40 μm, 23 to 40 μm, 23 to 30 μm, or 28 to 40 μm. 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, for example, 100 threads / inch or more, 105 threads / inch or more, 110 threads / inch or more, and 150 threads / inch or more, as this increases the dimensional change rate in the film thickness direction described later and improves the effects of this disclosure. More preferably, it is 350 threads / inch or less, 300 threads / inch or less, 250 threads / inch or less, and 200 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 105 threads / inch or more and 250 threads / inch or less, and most preferably 105 threads / inch or more and 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. The distance between the two outermost warp threads is measured five times at different locations, and the arithmetic mean of the distances is calculated. The warp density (in units: threads / inch) is then calculated using the obtained arithmetic mean. For the weft threads, 100 adjacent weft threads are selected from the 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 weft density (in units: threads / inch) is then calculated using the obtained arithmetic mean. Note that if the thread is a multifilament, 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, and particularly preferably 70% 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, and even more preferably 60% or more and 70% 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 4.0% by mass or more relative to the total mass of the electrolyte membrane, more preferably 5.0% by mass or more, and even more preferably 6.0% 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, particularly preferably 8.0% by mass or less, and most preferably 7.0% 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 4.0% by mass or more and 15.0% by mass or less, more preferably 5.0% by mass or more and 10.0% by mass or less, even more preferably 6.0% by mass or more and 9.0% by mass or less, particularly preferably 6.0% by mass or more and 8.0% by mass or less, and particularly preferably 6.0% by mass or more and 7.0% by mass or less, relative to the total mass of the electrolyte membrane. The amount of reinforcing material is determined by the method described in the Examples section below.

[0060] <Platinum-containing material> This electrolyte membrane contains platinum-containing material. When this electrolyte membrane is applied to an electrolytic device, it is thought that hydrogen generated on the cathode side reacts with oxygen generated on the anode side on the platinum-containing material contained in this electrolyte membrane to form water, thereby suppressing the movement of hydrogen to the anode side (hydrogen crossover).

[0061] Platinum-containing materials only need to contain platinum atoms. Specific examples of platinum-containing materials include platinum itself, platinum oxides, platinum-containing composite metal oxides, and platinum alloys. Specific examples of platinum-containing composite oxides include M ｘ Pt ３ O ４ (M is at least one metal atom selected from the group consisting of Li, Na, Mg, Ca, Zn, Cd, Co, Ni, Mn, Cu, Ag, Bi, and Ce, and x is greater than 0 and less than or equal to 1.) Specific examples of platinum alloys include alloys containing platinum and at least one metal selected from the group consisting of transition metals and noble metals other than platinum.

[0062] Specific examples of the shape of the platinum-containing substance include particulate and sheet-like forms. When the platinum-containing substance is particulate, the platinum-containing substance may be a core-shell type particle. As an example of the core-shell type particle, there is an aspect in which the core is carbon or a particle containing a metal other than platinum, and the shell contains platinum atoms. When the platinum-containing substance is particulate, the average particle diameter (D50) of the platinum-containing substance is preferably 1 nm or more, more preferably 5 nm or more, still more preferably 10 nm or more, and particularly preferably 100 nm or more. Also, the above D50 is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 14 μm or less, and particularly preferably 7 μm or less. The method for measuring the average particle diameter of the platinum-containing substance is as follows. The average particle diameter of the platinum-containing substance is measured using an image-based particle size distribution measuring device (for example, the "Morphologi (registered trademark)" series manufactured by Malvern Panalytical), and 40,000 particle diameters are measured dry, and the cumulative 50% diameter (D50) of the volume-based particle size distribution cumulative curve is obtained.

[0063] The mass of the platinum-containing substance per 1 cm of this electrolyte membrane ２ is preferably 0.005 mg / cm ２ or more, more preferably 0.010 mg / cm ２ or more, still more preferably 0.015 mg / cm ２ or more. The mass of the platinum-containing substance per 1 cm of this electrolyte membrane ２ is preferably 0.050 mg / cm ２ or less, more preferably 0.040 mg / cm ２ or less, still more preferably 0.030 mg / cm ２ or less, particularly preferably 0.025 mg / cm ２ or less. If the mass of the platinum-containing substance is 0.005 mg / cm ２ or more, the generation of hydrogen crossover can be more suppressed. If the mass of the platinum-containing substance is 0.050 mg / cm ２ or less, the electrolysis voltage can be made lower, and a low-cost membrane electrode assembly and electrolysis device can be provided. Also, if the mass of the platinum-containing substance is 0.040 mg / cm ２ or less, more preferably 0.0025 mg / cm２ If the following conditions are met, the color of this electrolyte membrane becomes lighter, making it easier to find foreign substances present in this electrolyte membrane. As a result, when applying this electrolyte membrane to an electrolysis device, it is possible to avoid using the portion where foreign substances are present in the electrolyte membrane, thereby suppressing the generation of pinholes in the electrolyte membrane caused by foreign substances.

[0064] The platinum-containing substance may be supported on a carrier. Specific examples of the carrier include carbon carriers such as carbon black powder, graphitized carbon, carbon fiber, and carbon nanotubes. When the platinum-containing substance is supported on a carrier, the supported amount of the platinum-containing substance is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and preferably 50% by mass or less with respect to the total mass of the platinum-containing substance and the carrier.

[0065] <Cerium oxide> This electrolyte membrane may contain cerium oxide. As a result, the decomposition of the fluorine-containing polymer in the electrolyte membrane is suppressed, and thus the chemical durability of the electrolyte membrane can be further improved.

[0066] Cerium oxide may be CeO ２ (cerium (IV) oxide), or Ce ２ O ３ (cerium (III) oxide), but from the perspective of stability, CeO ２ is preferred. Cerium oxide may be doped with polyvalent metal ions such as zirconium and praseodymium.

[0067] Cerium oxide is preferably in particulate form. When cerium oxide is in particulate form, the average particle size (D50) of cerium oxide is preferably 10 nm or more, more preferably 100 nm or more, even more preferably 1 μm or more, and particularly preferably 3 μm or more. Furthermore, the above D50 is preferably 30 μm or less, more preferably 14 μm or less, and even more preferably 10 μm or less. If the average particle size of cerium oxide is 10 nm or more, aggregation of cerium oxide is suppressed, and a stable dispersion state can be easily achieved. If the average particle size of cerium oxide is 30 μm or less, the chemical durability of this electrolyte membrane can be further improved. The method for measuring the average particle size of cerium oxide is as described below. The average particle size of cerium oxide is obtained by measuring the size of 40,000 particles in a dry manner using an image-based particle size distribution analyzer (for example, the "Morphologi" series manufactured by Malvern Panalytical), and then determining the 50% cumulative diameter of the volume-based cumulative particle size distribution curve.

[0068] Main electrolyte membrane 1cm ２ The mass of cerium oxide per unit is 0.010 mg / cm³. ２ The above is preferable, and 0.029 mg / cm³ is preferred. ２ The above is more preferable, 0.043 mg / cm³ ２ The above is even more preferable: 0.088 mg / cm³ ２ The above is particularly preferred, with 0.132 mg / cm³. ２ The above is most preferable. Furthermore, the above mass is 1,000 mg / cm³. ２ The following is preferred: 0.500 mg / cm³ ２ The following is more preferable: 0.300 mg / cm³ ２ The following is even more preferable.

[0069] <Physical Properties, etc.> (Film Thickness) The film thickness of this electrolyte membrane is preferably 20 μm or more, more preferably 40 μm or more, particularly 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. Among these, the film thickness of this electrolyte membrane is preferably 20 to 150 μm, more preferably 50 to 150 μm or 40 to 130 μm, and even more preferably 50 to 90 μm, from the viewpoint of a higher rate of dimensional change in the film thickness direction described later, and thus the effects of this disclosure are better. 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.

[0070] (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, and even more preferably 80% or more, from the viewpoint of achieving superior effects in 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%, and even more preferably 70 to 100%.

[0071] Formula (Z) Percentage change in the direction of film thickness (%) = 100 × (T2 - T1) / T1 T1: Film thickness of the electrolyte membrane obtained by standing the electrolyte membrane at 23°C for 16 hours T2: Film thickness of the electrolyte membrane obtained by immersing the electrolyte membrane obtained in T1 in water at 95°C 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.

[0072] (In-plane dimensional change rate) The in-plane dimensional change rate of this electrolyte membrane is preferably -5% or more, and more preferably 0% or more, from the viewpoint of maintaining the electrolytic area when incorporated into an electrolytic cell. The in-plane dimensional change rate of this electrolyte membrane is preferably 10% or less, more preferably 5% or less, even more preferably 3% or less, particularly preferably 1% or less, even more preferably 0.5% or less, and more preferably 0.3% or less, from the viewpoint of achieving superior effects of this disclosure. The in-plane dimensional change rate of this electrolyte membrane is preferably -5 to 10%, more preferably 0 to 5%, even more preferably 0 to 3%, and particularly preferably 0 to 1%.

[0073] The in-plane dimensional change rate of this electrolyte membrane refers to the arithmetic mean of the dimensional change rate along line A, which passes through the center point of a square sample and is parallel to one side of the square, and the dimensional change rate along line B, which passes through the center point of the square sample and is perpendicular to line A, using a sample of this electrolyte membrane cut into a square. The dimensional change rates of line A and line B are determined by the following formula (X). Formula (X) Dimensional change rate of line A (or line B) (%) = 100 × (L2 - L1) / L1 L1: Length of line A (or line B) in the electrolyte membrane obtained by standing the electrolyte membrane at 23°C for 16 hours L2: Length of line A (or line B) in the electrolyte membrane obtained by immersing the electrolyte membrane obtained in L1 in water at 95°C for 1 hour Details of the method in L1 and details of the immersion method in L2 are described in the Examples section below.

[0074] <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).

[0075] <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 having a group that can be converted into an ion exchange group (hereinafter also called a "fluorine-containing monomer (I')") (hereinafter also called a "fluorine-containing polymer (I')"), a platinum-containing material, 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.

[0076] A preferred embodiment of the method for producing the precursor film is as follows: First, a fluorine-containing polymer (I') and a platinum-containing material are kneaded together to obtain a mixture containing the fluorine-containing polymer (I') and the platinum-containing material. Next, a film containing the fluorine-containing polymer (I') and the platinum-containing material is obtained using the mixture. The film-forming method is not particularly limited and can be, for example, a melt extrusion method. Next, the film is placed on both sides of a reinforcing material (preferably a woven fabric) to obtain a laminate in which the film, reinforcing material, and film are stacked in this order, and then both sides of the laminate are heated and pressed. In this way, a precursor film is obtained. Here, a transfer substrate may be placed on both sides of the laminate. Specific examples of the transfer substrate include polyethylene film, polypropylene film, polystyrene film, and polyethylene terephthalate film.

[0077] As explained above, the reinforcing materials and platinum-containing substances will not be described further.

[0078] 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.

[0079] Methods for copolymerizing fluorine-containing polymers (S') can include known methods such as solution polymerization, suspension polymerization, and emulsion polymerization.

[0080] 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%.

[0081] 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.

[0082] 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

[0083]

[0084] R in the formula ｆ１ , R ｆ２ The definitions of r and A are as described above.

[0085]

[0086] R in the formula ｆ１ , R ｆ２ , R ｆ３ The definitions of r, m, and A are as described above.

[0087] Of the compounds represented by formula (2-1) and formula (2-2), the compound represented by formula (2-5) is preferred. Formula (2-5) CF２ = CF - (CF ２ ) ｘ - (OCF ２ CFY) ｙ -O-(CF ２ ) ｚ -SO ２ The definitions of x, y, z, and Y in equation F are as described above.

[0088] Specific examples of compounds 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

[0089] Specific examples of compounds 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

[0090] Of the compounds represented by formula (2-3), the compound represented by formula (2-3-1) is preferred.

[0091]

[0092] R in the formula ｆ４ , R ｆ５ The definitions of r and A are as described above.

[0093] Specific examples of compounds represented by formula (2-3-1) include the following:

[0094]

[0095] Of the compounds represented by formula (2-4), the compound represented by formula (2-4-1) is preferred.

[0096]

[0097] R in the formula ｆ１ , R ｆ２ The definition of A is as stated above.

[0098] Specific examples of compounds represented by formula (2-4-1) include the following:

[0099]

[0100] 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 35 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.

[0101] 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').

[0102] 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.

[0103] 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 more preferably 40 to 100°C. The contact time between the precursor film and the alkaline aqueous solution is preferably 3 to 150 minutes, and more preferably 5 to 50 minutes.

[0104] 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 more 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 more preferably contains an aprotic organic solvent. The water-soluble organic solvent may be used alone or in combination of two or more.

[0105] 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.

[0106] The concentration of alkali metal hydroxide is preferably 1 to 60% by mass, and more 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 more 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.

[0107] 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.

[0108] 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.

[0109] [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.

[0110] 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.

[0111] <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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] <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.

[0116] <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).

[0117] [Water Electrolyzer] The water electrolyzer of the present disclosure includes the membrane electrode assembly described above. Specifically, the water electrolyzer 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 electrolyzer 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 electrolyzer of the present disclosure may have the same configuration as known water electrolyzers, 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).

[0118] [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.

[0119] [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.

[0120] The present disclosure will be described in detail below with reference to examples. Examples 1 to 8 are embodiments, and Examples 9 to 12 are comparative examples. However, the present disclosure is not limited to these examples.

[0121] [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.

[0122] <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.

[0123] <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)

[0124] <Film Thickness> The film thickness of the solid polymer electrolyte membrane was determined using the method described above.

[0125] <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

[0126] <In-plane dimensional change rate> First, samples were obtained by cutting each example of the solid polymer electrolyte membrane into a 20 cm x 20 cm square. A line A (length 16 cm) was drawn parallel to one side of the square sample, passing through the center point of the square sample. A line B (length 16 cm) was also drawn perpendicular to line A, passing through the center point of the square sample. Next, the samples were left to stand at 23°C for 16 hours, and the lengths L1 of lines A and B were measured. Next, the samples were immersed in 95°C water for 1 hour, and then cooled until the water temperature reached 25°C. The samples were removed, and the water adhering to the surface of the samples was wiped off with filter paper. The lengths L2 of lines A and B of the obtained samples were measured. Using lengths L1 and L2, the dimensional change rates of line A and line B were calculated using the following formula (X). The arithmetic mean of the dimensional change rates of line A and line B was defined as the in-plane dimensional change rate (%). The results are shown in Table 1. Formula (X) Percentage change in dimensions of line A (or line B) (%) = 100 × (L2 - L1) / L1

[0127] [Evaluation Method] <Chemical Durability> A film electrode assembly is sandwiched between platinum-plated titanium fiber sintered bodies (manufactured by Bekart Co., Ltd.) with a thickness of 0.25 mm and a porosity of 60%, and a platinum-plated titanium plate with a straight channel is used as a separator. Electrode area: 16 cm² ２A membrane electrode assembly was incorporated into a single cell for evaluation. When the membrane electrode assembly was clamped, a pressure of 1.5 MPa was applied to the electrode portion. Next, to ensure sufficient water absorption of the electrolyte membrane and both electrode ionomers, pure water with a conductivity of 1.0 μS / cm or less, at a temperature of 60°C and atmospheric pressure was supplied to both the anode catalyst layer and the cathode catalyst layer at a flow rate of 50 mL / min for 8 hours. Subsequently, pure water with a conductivity of 1.0 μS / cm or less and at a temperature of 60°C was supplied to the anode catalyst layer at a flow rate of 50 mL / min, while maintaining atmospheric pressure in both the anode and cathode catalyst layers. A high-current potentio / galvanostat HCP-803 (manufactured by Biologic) was used to apply 16 A (current density 1 A / cm²). ２ While maintaining the current, water electrolysis was performed for 4 hours as a break-in operation. After that, the water supply rate to the anode catalyst layer was changed to 150 mL / min, and the back pressure was changed to 50 kPa for both the anode and cathode, resulting in a current density of 1 A / cm². ２ The system was operated for 1,000 hours. After the break-in period, wastewater discharged from the cathode catalyst layer was sampled between 500 and 1,000 hours after the start of operation. The amount of fluoride ions contained in this wastewater was quantified by ion chromatography and averaged to calculate the average amount of fluoride ions per unit electrode area and unit time, and evaluated as the fluorine release rate according to the following criteria. A smaller fluorine release rate indicates that the decomposition of the fluorine-containing polymer is suppressed and the chemical durability of the electrolyte membrane is excellent. A: 1.0 × 10 －６ mg / (h·cm) ２ ) Less than B: 1.0 × 10 －６ mg / (h·cm) ２ ) Above, 3.0 x 10 －６ mg / (h·cm) ２ ) Less than C: 3.0 x 10 －６ mg / (h·cm) ２ ) Above, 5.0 x 10 －６ mg / (h·cm) ２ ) Less than D: 5.0 x 10 －６ mg / (h·cm) ２ ) That's all.

[0128] <Pinhole> After heat treatment of the membrane electrode assembly at 150°C for 15 minutes, it was set in a water electrolysis evaluation jig EH50-25 (manufactured by Greenlight Innovation). Next, 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, and the generated gas pressure on the cathode side was kept at atmospheric pressure. A current density of 2 A / cm² was supplied using a Kikusui Electronics PWR1600L DC power supply. ２ The system was operated for 300 hours. After operation, the number of pinholes (holes) in the electrolyte membrane of the membrane electrode assembly was measured using a pinhole inspection device (product name "TRS-70", manufactured by Sanko Electronics Laboratory Co., Ltd.) and evaluated according to the following criteria: A: No pinholes. B: 1 to 2 pinholes. C: 3 or more pinholes.

[0129] [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 in parentheses represents the ion exchange capacity of the fluorine-containing polymer obtained when the fluorine-containing polymer (S'-1) is 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)

[0130] [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).

[0131] [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).

[0132] [Manufacturing of Film α1] A fluorine-containing polymer (S'-1) and platinum black (TEC90300 manufactured by Tanaka Kikinzoku Co., Ltd., hereinafter referred to as "platinum-containing material") were molded by melt extrusion to obtain Film α1 (film thickness: 45 μm) made of the fluorine-containing polymer (S'-1).

[0133] [Production of Film α2] A fluorine-containing polymer (S'-2) and a platinum-containing material were melt-kneaded and molded by a melt-extrusion method to obtain Film α2 (film thickness: 45 μm) consisting of the fluorine-containing polymer (S'-2) and the platinum-containing material.

[0134] [Production of Film α3] A fluorine-containing polymer (S'-1) and a platinum-containing material were melt-kneaded and molded by a melt-extrusion method to obtain Film α3 (film thickness: 30 μm) consisting of the fluorine-containing polymer (S'-1) and the platinum-containing material.

[0135] [Production of Film α4] A fluorine-containing polymer (S'-2) and a platinum-containing material were melt-kneaded and molded by a melt-extrusion method to obtain Film α4 (film thickness: 30 μm) consisting of the fluorine-containing polymer (S'-2) and the platinum-containing material.

[0136] [Manufacturing of Film α5] A fluorine-containing polymer (S'-1) and a platinum-containing material were melt-kneaded and molded by a melt-extrusion method to obtain Film α5 (film thickness: 25 μm) consisting of the fluorine-containing polymer (S'-1) and the platinum-containing material.

[0137] [Production of Film α6] A fluorine-containing polymer (S'-3) and a platinum-containing material were melt-kneaded and molded by a melt-extrusion method to obtain Film α6 (film thickness: 40 μm) consisting of the fluorine-containing polymer (S'-3) and the platinum-containing material.

[0138] [Manufacturing of Woven Fabric A1] Woven fabric A1 was obtained by plain weaving polyetheretherketone (PEEK) yarn, with a diameter of 38 μm and 13.3 denier, for both the warp and weft, so that the yarn density was 10⁹ threads / inch. The basis weight of woven fabric A1 was 12.7 g / m². ２ The warp and weft threads were composed of slit yarn. The above PEEK had the following structure.

[0139]

[0140] [Manufacturing of Woven Fabrics A2 to A7] Woven fabrics A2 to A7 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.

[0141] [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.

[0142] [Examples 2-12] Solid polymer electrolyte membranes of Examples 2-12 were obtained in the same manner as in Example 1, except that the film, woven fabric, and platinum-containing content were changed as shown in Table 1.

[0143] [Manufacturing of membrane electrode assemblies] CF ２ =CF ２A polymer (ion exchange capacity: 1.10 milliequivalents / gram dry resin) was copolymerized with the above monomer (X), hydrolyzed, and subjected to acid treatment to obtain an acid-type polymer. This polymer was dispersed in a water / ethanol = 40 / 60 (mass%) solvent at a solid content concentration of 26.0% to obtain a dispersion (hereinafter also referred to as "dispersion Y"). To the obtained dispersion Y (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.

[0144] 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 Y (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 using 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.

[0145] 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 membrane electrode assembly was obtained. The obtained membrane electrode assembly was subjected to the various evaluations described above. The results are shown in Table 1.

[0146]

[0147] As shown in Table 1, the electrolyte membrane of this disclosure was confirmed to have excellent chemical durability (Examples 1-8). Furthermore, from the comparison of Examples 1-8, the electrolyte membrane 1 cm ２ The mass of platinum content per unit is 0.030 mg / cm³. ２ It was confirmed that pinhole formation can be suppressed in the following cases (Examples 1-6). Furthermore, from a comparison of Example 7 and Example 8, it was confirmed that chemical durability is superior when the reinforcing material content is 6.0% by mass or more relative to the total mass of the electrolyte membrane (Example 7).

[0148] 10 Solid polymer electrolyte membrane 20 Membrane electrode assembly 22 Anode 24 Cathode 26 Catalyst layer 28 Gas diffusion layer

[0149] Furthermore, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-197613, 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, a reinforcing material, and a platinum-containing material, wherein the reinforcing material is composed of polyetheretherketone, and the ion exchange capacity of the fluorine-containing polymer is 1.10 milliequivalents / gram dry resin or more.

2. The solid polymer electrolyte membrane 1 cm ２ The mass of the platinum-containing substance per unit is 0.030 mg / cm³. ２ The solid polymer electrolyte membrane according to claim 1, which is as follows:

3. The solid polymer electrolyte membrane according to claim 1, wherein 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.

4. The solid polymer electrolyte membrane according to claim 1, wherein the dimensional change rate in the film thickness direction of the solid polymer electrolyte membrane, as determined by the following formula (Z), is 60% or more. Formula (Z) Dimensional change rate in the film thickness direction (%) = 100 × (T2 - T1) / T1 T1: Film thickness of the solid polymer electrolyte membrane obtained by standing the solid polymer electrolyte membrane at 23°C for 16 hours T2: Film thickness of the solid polymer electrolyte membrane obtained by immersing the solid polymer electrolyte membrane obtained in T1 in water at 95°C for 1 hour 5. The solid polymer electrolyte membrane according to claim 1, wherein the reinforcing material is a woven fabric.

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

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

8. 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.

9. The solid polymer electrolyte membrane according to claim 8, 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.

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

11. 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 10, disposed between the anode and the cathode.

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

13. An electrolytic hydrogenation apparatus comprising the membrane electrode assembly described in claim 11.

14. A method for producing hydrogen, comprising producing hydrogen by electrolyzing water using the water electrolysis apparatus described in claim 12.

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