Separator for hydrogen production, alkaline water electrolysis member using same, alkaline water electrolysis cell using same, alkaline water electrolysis device using same, method for producing hydrogen using same, and method for producing separator for hydrogen production

Abstract

Provided are: a separator for hydrogen production, the separator containing a woven fabric support and a porous material that contains an organic polymer, wherein the calender ratio of the woven fabric support calculated by the formula below is 73% or less; an alkaline water electrolysis member, an alkaline water electrolysis cell, an alkaline water electrolysis device, and a method for producing hydrogen, each using the same; and a method for producing a separator for hydrogen production.　Calender ratio = (d2 / (2 × d1)) × 100% In the formula, d1 represents the fiber diameter of the woven fabric support, and d2 represents the thickness of the woven fabric support.

Description

Separator for hydrogen production, alkaline water electrolysis component using same, alkaline water electrolysis cell, alkaline water electrolysis device, method for producing hydrogen, and method for producing separator for hydrogen production

[0001] The present invention relates to a separator for hydrogen production, an alkaline water electrolysis member using the separator, an alkaline water electrolysis cell, an alkaline water electrolysis apparatus, a method for producing hydrogen, and a method for producing a separator for hydrogen production.

[0002] Hydrogen is a clean energy source that does not emit carbon dioxide and is used, for example, as a fuel for fuel cell vehicles and household fuel cells. Alkaline water electrolysis, which uses a highly concentrated alkaline aqueous solution as the electrolyte, is a well-known method for producing hydrogen. Alkaline water electrolysis, powered by a renewable energy power generation system, can produce hydrogen without emitting carbon dioxide. Therefore, hydrogen is increasingly attracting attention as a fundamental energy source for a sustainable society.

[0003] In alkaline water electrolysis, hydrogen bubbles (2H ２ O + 2e － →H ２ +2OH － ) to the anode side, and also prevents the bubble-like oxygen (4OH) generated at the anode (positive electrode). － →O ２ +2H ２ O+4e － In order to prevent OH from migrating to the cathode side, a gas barrier separator (membrane) is placed between the cathode and the anode. In addition to the gas barrier properties, this separator also has the function of preventing OH from migrating from the cathode side to the anode side. － The separator used in alkaline water electrolysis is therefore a porous membrane (microporous membrane) made of an organic polymer material.

[0004] Porous separators used in alkaline water electrolysis can be formed by wet phase separation. In wet phase separation, a dope solution is prepared by dissolving an organic polymer, which is a constituent material of the porous membrane, in a solvent (good solvent) that dissolves the organic polymer. A coating of the dope solution is then formed. The coating is then immersed in a solvent (poor solvent, coagulation bath) that does not dissolve the organic polymer but is compatible (miscible) with the good solvent. This immersion reduces the proportion of the good solvent in the coating, causing phase separation between the organic polymer and the solvent, resulting in gelation (coagulation) of the organic polymer, resulting in the formation of a porous membrane. To enhance the mechanical strength of the porous separator, a porous support, such as a nonwoven fabric or woven fabric, is placed in the dope solution. The phase separation is then carried out in the presence of the porous support, resulting in the organic polymer in the impregnated dope solution forming a porous structure. This results in a porous separator in which the porous support and the porous structure of the organic polymer are integrated. Furthermore, by including hydrophilic inorganic particles in the separator, the gas barrier properties can be improved, and at the same time, the alkaline aqueous solution can be efficiently permeated into the separator, thereby further increasing the ionic conductivity.

[0005] For example, Patent Document 1 describes such a porous separator, which includes a porous support and first and second porous layers provided on one and the other sides of the porous support, respectively. In this separator, the porous support has a thickness of 150 μm or less, the separator has a thickness of less than 250 μm, and the porous layers may contain hydrophilic inorganic particles. The technology described in Patent Document 1 is said to provide a separator with sufficient mechanical quality and improved ionic conductivity.

[0006] Special Publication No. 2023-531792

[0007] In recent years, with the aim of improving the efficiency of hydrogen production and making alkaline water electrolysis systems suitable for renewable energy, research and development has been progressing on high-pressure alkaline water electrolysis systems (also referred to as "pressurized alkaline water electrolysis systems" because they are operated under a pressure of 5 bar or more compared to atmospheric pressure (approximately 1 bar)). As described in Patent Literature 1, porous separators used in conventional alkaline water electrolysis systems operated under atmospheric pressure exhibited sufficient mechanical quality and improved ionic conductivity when hollowed out into a square or rectangular shape and applied to alkaline water electrolysis systems. However, in alkaline water electrolysis systems compatible with pressurized operation, separators and electrodes are hollowed out into circular shapes with better pressure resistance to prevent damage to the components. The inventors' studies have revealed that when conventional porous separators, such as the separator described in Patent Literature 1, are incorporated into electrolytic cells, electrolyte leakage, current leakage, etc., interfere with the operation of pressurized alkaline water electrolysis systems. The inventors have conducted extensive research into the above-described problems that arise when circularly hollowed porous separators are incorporated into electrolytic cells of pressurized alkaline water electrolysis systems, and have found that circular porous separators are prone to deformation during the process of incorporating them into electrolytic cells, and that this deformation interferes with the operation of the pressurized alkaline water electrolysis system.

[0008] An object of the present invention is to provide a separator for hydrogen production that has excellent dimensional stability during assembly of an alkaline water electrolysis cell and excellent ionic conductivity, and a method for producing the same. Another object of the present invention is to provide an alkaline water electrolysis member, an alkaline water electrolysis cell, an alkaline water electrolysis apparatus, and a method for producing hydrogen that use the separator for hydrogen production of the present invention.

[0009] The above-mentioned object of the present invention has been achieved by the following means. [1] A separator for hydrogen production comprising a woven fabric support and a porous material containing an organic polymer, wherein the calendaring ratio of the woven fabric support calculated by the following formula is 73% or less: Calendaring ratio = {d2 / (2 x d1)} x 100% In the formula, d1 represents the fiber diameter of the woven fabric support, and d2 represents the thickness of the woven fabric support. [2] The separator for hydrogen production according to [1], wherein the fiber diameter d1 of the woven fabric support is 180 μm or less. [3] The separator for hydrogen production according to [1] or [2], wherein the thickness d2 of the woven fabric support is 250 μm or less. [4] The separator for hydrogen production according to any one of [1] to [3], wherein the material of the woven fabric support includes at least one of polyphenylene sulfide and polyether ether ketone. [5] The separator for hydrogen production according to any one of [1] to [4], wherein the organic polymer comprises at least one of polysulfone, polyethersulfone, and polyphenylsulfone. [6] An alkaline water electrolysis element comprising the separator for hydrogen production according to any one of [1] to [5]. [7] An alkaline water electrolysis cell comprising the separator for hydrogen production according to any one of [1] to [5] or the alkaline water electrolysis element according to [6]. [8] An alkaline water electrolysis device comprising the alkaline water electrolysis cell according to [7]. [9] A method for producing hydrogen, comprising operating the alkaline water electrolysis device according to [8] at a pressure of 5 bar or more.

[10] A method for producing hydrogen, comprising operating the alkaline water electrolysis device according to [8], applying a pressure of 50 mbar or more from the hydrogen generation side to the oxygen generation side.

[11] A method for producing a separator for hydrogen production according to any one of [1] to [5], comprising forming a porous material containing the organic polymer by wet phase separation in a state in which a woven fabric support obtained by calendering, the woven fabric support having a calendering ratio calculated by the following formula being 73% or less, is disposed in a coating film formed from a dope solution in which an organic polymer is dissolved: Calendering ratio = {d2 / (2 × d1)} × 100% In the formula, d1 represents the fiber diameter of the woven fabric support, and d2 represents the thickness of the woven fabric support.

[0010] In the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0011] The hydrogen production separator of the present invention has excellent dimensional stability and ionic conductivity during assembly of an alkaline water electrolysis cell. Furthermore, the hydrogen production separator of the present invention can be suitably manufactured by the method for manufacturing a hydrogen production separator of the present invention. Furthermore, the alkaline water electrolysis member of the present invention has excellent dimensional stability during assembly of an alkaline water electrolysis cell and excellent ionic conductivity. Furthermore, the alkaline water electrolysis cell and alkaline water electrolysis device of the present invention enable hydrogen production by preventing the hydrogen production separator of the present invention from protruding from the cell during assembly of a pressurized alkaline water electrolysis cell, preventing problems such as electrolyte leakage and gas leaks due to defects, and providing excellent ionic conductivity. Furthermore, the hydrogen production method of the present invention enables efficient hydrogen production using the alkaline water electrolysis device of the present invention.

[0012] Fig. 1 is a schematic cross-sectional view of a woven fabric support for illustrating a thickness d2 of the woven fabric support. Fig. 2 is a diagram schematically illustrating an embodiment of an alkaline water electrolysis system. Fig. 3 is a diagram schematically illustrating another embodiment of an alkaline water electrolysis system. Fig. 4 is a diagram schematically illustrating yet another embodiment of an alkaline water electrolysis system.

[0013] [Separator for Hydrogen Production] The separator for hydrogen production of the present invention is a separator for hydrogen production comprising a woven fabric support and a porous material containing an organic polymer, wherein the calendering ratio of the woven fabric support, calculated by the formula described below, is 73% or less. In the configuration of the separator for hydrogen production of the present invention comprising a woven fabric support and a porous material containing an organic polymer, by setting the calendering ratio of the woven fabric support, calculated by the formula described below, to 73% or less, the separator for hydrogen production can achieve excellent dimensional stability against tension and also has excellent ionic conductivity. Therefore, when the separator for hydrogen production of the present invention is applied to an alkaline water electrolysis cell, hydrogen can be produced without causing problems such as electrolyte leakage and gas leaks due to defects.

[0014] The specific configuration of the hydrogen production separator of the present invention, which is composed of a woven fabric support and a porous material containing an organic polymer, is not particularly limited as long as the calendaring ratio of the woven fabric support, calculated using the formula described below, is 73% or less, and the separator has the desired gas barrier properties and hydroxy ion permeability (ionic conductivity) required for a hydrogen production separator. For example, the hydrogen production separator of the present invention can be configured to be composed of a woven fabric support and a porous material containing an organic polymer disposed on at least one of the outer surface and voids of the woven fabric support. A structure in which a porous material containing an organic polymer is disposed on the outer surface and in the voids of the woven fabric support can be obtained, for example, by the manufacturing method of the hydrogen production separator of the present invention described below. Note that the "outer surface of the woven fabric support" refers to the surface of the membrane when the woven fabric support is viewed as a membrane having a single thickness from a macroscopic perspective, and the "voids of the woven fabric support" refer to the gaps between the fibers that make up the woven fabric support. The structure in which a porous material containing an organic polymer is disposed on at least one of the outer surface and voids of a woven fabric support can be appropriately adjusted within a range in which the hydrogen production separator has the desired gas barrier properties and ionic conductivity. For example, the porous material may be disposed only on the outer surface of the woven fabric support. In this case, the porous material may be disposed on only one side of the woven fabric support, or on both sides. The porous material may also be disposed only in the voids of the woven fabric support. Furthermore, the porous material may be disposed on part of the outer surface of the woven fabric support and part of the voids. In the present invention, such a configuration is also included in the structure in which a porous material containing an organic polymer is disposed on at least one of the outer surface and voids of a woven fabric support. Among these, a structure in which the porous material is disposed on the entire outer surface of the woven fabric support and in all the voids is preferred.

[0015] The constituent materials of the separator for hydrogen production of the present invention will be described in detail below.

[0016] (Woven Fabric Support) The woven fabric support is a woven fabric that functions as a support for reinforcing the hydrogen production separator and increasing its mechanical strength. In the hydrogen production separator of the present invention, the calendering ratio calculated by the following formula is 73% or less: Calendering ratio = {d2 / (2 x d1)} x 100% In the above formula, d1 represents the fiber diameter of the woven fabric support, and d2 represents the thickness of the woven fabric support. In calculating the calendering ratio, d1 and d2 may have the same unit; for example, the calendering ratio is calculated by substituting the units of d1 and d2, both in μm, into the above formula. d1 and d2 are values ​​measured and calculated by the following methods. The fiber diameter d1 of the woven fabric support is calculated as the arithmetic mean value of 20 fiber diameters equidistant from two adjacent intersections (fiber intersections) in an optical microscope image observed with transmitted light in a 1 mm square field of view, with a plane perpendicular to the thickness direction of the woven fabric support (i.e., the front or back surface of the woven fabric support) as the observation surface. The thickness d2 of the woven fabric support is calculated as the arithmetic mean value of 20 thicknesses of the fiber intersections (thickness d2 at the intersection of weft thread F1 and warp thread F2 shown in Figure 1) for a 10 cm square woven fabric support using a digital micrometer (e.g., manufactured by MESSMER-BUCHEL) (see Figure 1). Note that d1 and d2 of the woven fabric support in a hydrogen production separator can be measured and calculated by the above method after removing the woven fabric support from the hydrogen production separator using a solvent that dissolves the organic polymer contained in the porous material.

[0017] The upper limit of the calendering ratio is preferably 70% or less from the viewpoint of further suppressing deformation during assembly of the alkaline water electrolysis cell. The lower limit of the calendering ratio is 50% or more due to the structure of the woven fabric. Therefore, the calendering ratio is usually in the range of 50 to 73%, preferably 55 to 73%, and more preferably 60 to 70% from the viewpoint of further suppressing deformation during assembly of the alkaline water electrolysis cell.

[0018] The fiber diameter d1 of the woven fabric support is preferably 180 μm or less, more preferably 30 to 180 μm, and even more preferably 35 to 150 μm. The thickness d2 of the woven fabric support is preferably 250 μm or less, more preferably 40 to 250 μm, and even more preferably 50 to 210 μm.

[0019] The opening ratio of the woven fabric support is preferably 30 to 80%, more preferably 40 to 70%. The opening ratio is the ratio of the area of ​​voids to a unit area when the woven fabric support is viewed in a plane. The woven fabric support in the hydrogen production separator preferably has a calendering ratio of 50 to 73%, a fiber diameter d1 of 30 to 180 μm, and a thickness d2 of 40 to 250 μm; preferably has a calendering ratio of 50 to 73%, a fiber diameter d1 of 30 to 180 μm, and a thickness d2 of 50 to 210 μm; preferably has a calendering ratio of 50 to 73%, a fiber diameter d1 of 35 to 150 μm, and a thickness d2 of 40 to 250 μm; preferably has a calendering ratio of 50 to 73%, a fiber diameter d1 of 35 to 150 μm, and a thickness d2 of 50 to 210 μm. Furthermore, the woven fabric support in the hydrogen production separator preferably has a calendering ratio of 55 to 73%, a fiber diameter d1 of 30 to 180 μm, and a thickness d2 of 40 to 250 μm; preferably has a calendering ratio of 55 to 73%, a fiber diameter d1 of 30 to 180 μm, and a thickness d2 of 50 to 210 μm; preferably has a calendering ratio of 55 to 73%, a fiber diameter d1 of 35 to 150 μm, and a thickness d2 of 40 to 250 μm; preferably has a calendering ratio of 55 to 73%, a fiber diameter d1 of 35 to 150 μm, and a thickness d2 of 50 to 210 μm. Furthermore, the woven fabric support in the hydrogen production separator preferably has a calendering ratio of 60 to 70%, a fiber diameter d1 of 30 to 180 μm, and a thickness d2 of 40 to 250 μm; preferably has a calendering ratio of 60 to 70%, a fiber diameter d1 of 30 to 180 μm, and a thickness d2 of 50 to 210 μm; preferably has a calendering ratio of 60 to 70%, a fiber diameter d1 of 35 to 150 μm, and a thickness d2 of 40 to 250 μm; preferably has a calendering ratio of 60 to 70%, a fiber diameter d1 of 35 to 150 μm, and a thickness d2 of 50 to 210 μm.

[0020] The material of the woven fabric support is not particularly limited, and examples thereof include polypropylene (PP), polyethylene, polysulfone, polyphenylene sulfide (PPS), polyamide, polyethersulfone, polyphenylsulfone, polyethylene terephthalate, polyetheretherketone (PEEK), sulfonated polyetheretherketone, monochlorotrifluoroethylene, a copolymer of ethylene with tetrafluoroethylene or chlorotrifluoroethylene, polyimide, polyetherimide, m-aramid, etc. Among the above, the material of the woven fabric support preferably includes at least one of polypropylene (PP), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK), and more preferably includes at least one of polyphenylene sulfide (PPS) and polyetheretherketone (PEEK) from the viewpoint of further suppressing deformation during assembly of the alkaline water electrolysis cell.

[0021] <Method for preparing a woven fabric support having the above-mentioned calendering ratio> A woven fabric support having the above-mentioned calendering ratio can be prepared by subjecting a commercially available woven fabric to a calendering treatment so as to achieve the above-mentioned calendering ratio.

[0022] The open area ratio of the commercially available woven fabric to be subjected to the calendering treatment is preferably 30 to 80%, more preferably 40 to 70%. The open area ratio is the ratio of the area of ​​voids to a unit area when the woven fabric support is viewed in a plane.

[0023] The calendering is preferably carried out using a calendering device. Examples of calendering devices that can be used include a super calender, a gross calender, a machine calender, and a soft calender. The calendering is preferably carried out using two rolls. By passing the material through the nip (gap) between the two rolls, the thickness d2 of the woven fabric support can be reduced by pressure, shear force, heat, etc., and the calendering ratio of the woven fabric support can be adjusted. There are no particular limitations on the material constituting the rolls, and for example, metal rolls are preferred, and rolls made of steel or the like with a protective layer formed by thermally spraying nickel, chromium, ceramic, etc. on the surface are more preferred, and the surface is preferably polished to have a mirror gloss.

[0024] Although the calendering may be performed without heating the roll, heating is preferred because it can further reduce the thickness d2 of the woven fabric support. The surface temperature of the roll is preferably 90 to 300°C, more preferably 140 to 250°C, and even more preferably 160 to 210°C.

[0025] The linear pressure of the nip between the two rolls (nip pressure) is preferably 10 to 400 kgf / cm, more preferably 20 to 200 kgf / cm, and even more preferably 40 to 120 kgf / cm.

[0026] The processing speed (conveying speed) of the calendering treatment is preferably 5 to 60 m / min, more preferably 10 to 60 m / min, and even more preferably 15 to 40 m / min.

[0027] The number of nipping times may be one or more, preferably one to five times, and more preferably two to five times.

[0028] The surface roughness of the metal roll is preferably 3 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less. The practical lower limit is 0.1 μm or more.

[0029] (Porous Material Containing Organic Polymer) A porous material containing an organic polymer (hereinafter also simply referred to as "porous material") has the function of blocking the permeation of hydrogen gas and oxygen gas, and allowing the permeation of hydroxy ions.

[0030] - Organic Polymer - As the organic polymer contained in the porous material, various organic polymers applicable to wet phase separation can be used.

[0031] The organic polymer can be selected from, for example, fluororesins, olefin resins, polyester resins, aromatic hydrocarbon resins, etc. The fluororesins are preferably resins selected from polyvinylidene fluoride (PVDF) and polytetrafluoroethylene. The olefin resins are preferably polypropylene resins. The polyester resins are preferably resins selected from polyethylene terephthalate, polybutylene terephthalate, and polybutylene naphthalate. The aromatic hydrocarbon resins are preferably polystyrene resins.

[0032] Other preferred organic polymers include polysulfone (PSf), polyethersulfone (PES), polyphenylene sulfide, polyphenylsulfone (PPSf), polyacrylate, polyetherimide, polyimide, and polyamideimide.

[0033] The organic polymers may be used alone or in combination of two or more.

[0034] The organic polymer more preferably includes at least one of polyvinylidene fluoride (PVDF), polysulfone (PSf), polyethersulfone (PES), and polyphenylsulfone (PPSf), and further preferably includes at least one of polysulfone (PSf), polyethersulfone (PES), and polyphenylsulfone (PPSf).

[0035] The weight average molecular weight (Mw) of the organic polymer is not particularly limited. Taking into consideration the handleability of the dope solution described below and the mechanical strength of the resulting hydrogen production separator, the weight average molecular weight (Mw) can be, for example, 10,000 to 500,000, and preferably 20,000 to 300,000. The Mw can be determined under the following conditions. Apparatus: HLC-8220GPC (manufactured by Tosoh Corporation) Detector: Differential refractometer (RI (Refractive Index) detector) Precolumn: TSKGUARDCOLUMN HXL-L 6 mm x 40 mm (manufactured by Tosoh Corporation) Sample side columns: The following three columns were directly connected in order (all manufactured by Tosoh Corporation): TSK-GEL GMHXL 7.8 mm x 300 mm TSK-GEL G4000HXL 7.8 mm x 300 mm TSK-GEL G2000HXL 7.8 mm x 300 mm Reference side column: TSK-GEL G1000HXL 7.8 mm x 300 mm Thermostatic bath temperature: 40°C Mobile phase: THF (tetrahydrofuran) Sample side mobile phase flow rate: 1.0 mL / min Reference side mobile layer flow rate: 1.0 mL / min Sample concentration: 0.1 mass% Sample injection amount: 100 μL Data collection time: 5 to 45 minutes after sample injection Sampling pitch: 300 milliseconds

[0036] The content of the organic polymer in the porous material is preferably from 5 to 50% by mass, more preferably from 5 to 40% by mass, further preferably from 7 to 30% by mass, and particularly preferably from 9 to 25% by mass.

[0037] Hydrophilic Inorganic Particles The porous material containing an organic polymer may contain hydrophilic inorganic particles, preferably particles selected from metal oxides and metal hydroxides.

[0038] The metal oxide is preferably selected from the group consisting of zirconium oxide, titanium oxide, bismuth oxide, cerium oxide and magnesium oxide.

[0039] The metal hydroxide is preferably selected from the group consisting of zirconium hydroxide, titanium hydroxide, bismuth hydroxide, cerium hydroxide and magnesium hydroxide.

[0040] As the hydrophilic inorganic particles, in addition to particles selected from metal oxides and metal hydroxides, barium sulfate particles can also be used.

[0041] The hydrophilic inorganic particles may be used alone or in combination of two or more kinds.

[0042] The particle size of the hydrophilic inorganic particles is preferably 0.05 to 2.00 μm, more preferably 0.1 to 1.50 μm, even more preferably 0.15 to 1.00 μm, and still more preferably 0.20 to 1.00 μm. This particle size is the median diameter (D50), which means the particle size at 50% cumulative when the total volume of the particles is taken as 100% in the cumulative distribution measured by a laser diffraction / scattering method.

[0043] When the porous material contains hydrophilic inorganic particles, the content of the hydrophilic inorganic particles in the porous material is preferably 50 to 95 mass%, more preferably 60 to 95 mass%, still more preferably 70 to 93 mass%, and particularly preferably 75 to 91 mass%.

[0044] When the porous material contains hydrophilic inorganic particles, the ratio of the content of the hydrophilic inorganic particles to the content of the organic polymer in the porous material (hydrophilic inorganic particles / organic polymer) is preferably 10 / 1 to 1 / 1, more preferably 9 / 1 to 2 / 1, even more preferably 8 / 1 to 3 / 1, still more preferably 7 / 1 to 4 / 1, and still more preferably 6.5 / 1 to 5 / 1, in mass ratio.

[0045] When the hydrogen production separator of the present invention is produced by the method for producing a hydrogen production separator of the present invention described below, a certain amount of good solvent, which will be described later in the dope solution, inevitably remains in the porous material. As a result, the total content of the good solvent in the porous material is usually 0.01 to 5.00 mass%.

[0046] The thickness of the hydrogen production separator of the present invention is preferably 60 to 300 μm, more preferably 70 to 270 μm, and even more preferably 80 to 250 μm. This thickness is determined by taking a cross-sectional SEM (scanning electron microscope) image of a cross-section cut out of the hydrogen production separator with a razor at a magnification (e.g., 400x) that fits the separator cross-section in one field of view. Assuming that no pores are present in the obtained cross-sectional SEM image (assuming that the pores are filled with an organic polymer), the thickness is measured at 20-point intervals, and the arithmetic mean value of the 20 measured values ​​is determined.

[0047] The pore size of the pores in the separator for hydrogen production of the present invention should be small enough to prevent recombination of hydrogen and oxygen by avoiding gas crossover, and large enough to ensure efficient transport of hydroxy ions from the cathode to the anode. From the above viewpoints, the pore size of the pores in the separator for hydrogen production of the present invention is preferably 50 to 1,000 nm, more preferably 100 to 800 nm, and even more preferably 150 to 600 nm. The pore size is determined by the following method. A separator punched to a diameter of 1 cm is immersed in pure water for 24 hours at room temperature (25°C). Subsequently, the mean flow pore calculated by perm-porometry manufactured by Porometer Corporation is taken as the average pore size.

[0048] The porosity of the separator for hydrogen production of the present invention is preferably 30 to 70%, more preferably 40 to 60%, from the viewpoint of exhibiting excellent ion permeability and excellent gas barrier properties. This porosity can be calculated by the following method. First, a separator is cut to a predetermined area (S) and immersed in pure water at room temperature (25°C) for 24 hours. Thereafter, excess water droplets adhering to the surface are wiped off, and the weight (w1) and thickness (d) are measured. The separator is dried in an oven at 90°C for 24 hours, and the weight (w2) is measured again. The porosity is calculated using the following formula: Calculation formula: 1 - (w1 - w2) / (S x d)

[0049] The separator for hydrogen production of the present invention has an ionic resistance of 0.01 to 0.10 Ω cm from the viewpoint of the permeability of hydroxy ions required for a separator for alkaline water electrolysis. ２is preferably 0.01 to 0.08 Ω cm ２ More preferably, 0.01 to 0.07 Ω cm ２ The ionic resistance is a value measured by setting a circular punched separator for hydrogen production of the present invention in a cell and measuring it by an AC impedance method at 90° C. Details are as described in the Examples below.

[0050] The separator for hydrogen production of the present invention has a water permeability of 100 to 2000 mL / (h·m) from the viewpoint of the mass balance between the cathode side and the anode side of the electrolyte required for a separator for alkaline water electrolysis. ２ From the viewpoint that it is not necessary to devise an operation of the alkaline water electrolysis cell such as changing the amount of electrolyte permeated on the anode side and the cathode side, it is preferable that the electrolysis capacity is 100 to 1000 mL / (h·m ２ The water permeability is a value calculated by measuring the amount of liquid (mL) when a circular punched-out separator for hydrogen production of the present invention is set in a filter holder and a 30 mass % aqueous potassium hydroxide solution is passed through the circular separator for 30 seconds under conditions of 90°C and a gauge pressure of 1 bar, and converting the unit.

[0051] The separator for hydrogen production of the present invention can be used without any particular limitation as long as it is a separator for hydrogen production, and can be preferably used as a separator in an alkaline water electrolysis system (separator for alkaline water electrolysis), and more preferably as a separator in a pressurized alkaline water electrolysis system (separator for pressurized alkaline water electrolysis). The separator for hydrogen production of the present invention may be in the form of a long sheet wound into a roll, or may be pre-cut into a predetermined shape depending on the intended use, device, etc. Furthermore, the separator for hydrogen production of the present invention may be preserved and stored in a state immersed in a storage liquid such as pure water. Furthermore, the separator for hydrogen production of the present invention may be preserved and stored as a dried membrane without being immersed in a storage liquid.

[0052] [Method for Manufacturing a Separator for Hydrogen Production] The method for manufacturing a separator for hydrogen production of the present invention (hereinafter also referred to as the "manufacturing method of the present invention") includes forming a porous material containing the organic polymer by wet phase separation in a state in which a woven fabric support formed by calendering, the woven fabric support having a calendering ratio calculated by the following formula being 73% or less, is disposed in a coating formed from a dope solution containing an organic polymer dissolved therein: Calendering ratio = {d2 / (2 × d1)} × 100% In the above formula, d1 represents the fiber diameter of the woven fabric support, and d2 represents the thickness of the woven fabric support. d1 and d2 are the same as d1 and d2 in the separator for hydrogen production described above. This step results in a separator for hydrogen production of the present invention, which is composed of the woven fabric support and a porous material containing the organic polymer disposed on at least one of the outer surface and voids of the woven fabric support. In addition, with regard to a woven fabric support that has been calendered and has a calendering ratio calculated by the above formula of 73% or less (hereinafter also simply referred to as a "woven fabric support"), it is sufficient that the woven fabric support has been calendered by the method described in <Method for preparing a woven fabric support having the above calendering ratio> for the hydrogen production separator described above so that the calendering ratio calculated by the above formula is 73% or less, and the description of the calendering treatment described in <Method for preparing a woven fabric support having the above calendering ratio> can be applied to the calendering treatment.

[0053] (Dope Solution) The dope solution may be a solution of an organic polymer that is a constituent material of the porous material, and may contain an organic polymer and a solvent, and may further contain hydrophilic inorganic particles. The organic polymer contained in the dope solution can be described in the same manner as described above for the organic polymer in the separator for hydrogen production. Furthermore, the hydrophilic inorganic particles that may be contained in the dope solution can be described in the same manner as described above for the hydrophilic inorganic particles in the separator for hydrogen production.

[0054] In the production method of the present invention, the dope solution used in the wet phase separation may be any solvent (good solvent) capable of dissolving the organic polymer, and is preferably miscible with water. The solvent is preferably selected from the group consisting of N-methyl-pyrrolidone (NMP), N-ethyl-pyrrolidone (NEP), N-butyl-pyrrolidone (NBP), N,N-dimethylformamide (DMF), formamide, dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAC), acetonitrile, and mixtures thereof, with at least one of NMP and NBP being more preferred.

[0055] The content of the solvent in the dope solution is preferably 20 to 95% by mass, more preferably 25 to 90% by mass, even more preferably 30 to 80% by mass, still more preferably 30 to 70% by mass, still more preferably 32 to 60% by mass, and still more preferably 35 to 50% by mass.

[0056] - Organic Polymer - The content of the organic polymer in the dope solution is preferably 2 to 30% by mass, more preferably 4 to 20% by mass, even more preferably 5 to 15% by mass, and even more preferably 6 to 12% by mass.

[0057] - Hydrophilic inorganic particles - Hydrophilic inorganic particles are particles that are dispersed in the dope solution without dissolving, and such a dispersion state is also referred to as the dope solution in the present invention. In other words, the "solution" in the dope solution means that the organic polymer is dissolved in the solvent. When the dope solution contains hydrophilic inorganic particles, the content of the hydrophilic inorganic particles in the dope solution is preferably 20 to 95% by mass, more preferably 25 to 92% by mass, even more preferably 30 to 90% by mass, and particularly preferably 35 to 88% by mass.

[0058] Other Components The dope solution may contain components (other components) other than the components described above (solvent, organic polymer, and hydrophilic inorganic particles). For example, in order to control pore formation during wet phase separation, other components may include polyethylene glycol, polyethylene oxide, polypropylene glycol, ethylene glycol, tripropylene glycol, glycerol, polyhydric alcohol, dibutyl phthalate, diethyl phthalate, diundecyl phthalate, isononanoic acid or neodecanoic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl acetate, polyethyleneimine, polyacrylic acid, methylcellulose, dextran, calcium chloride, magnesium chloride, and lithium chloride. When the dope solution contains other components and hydrophilic inorganic particles, the total content of the other components in the dope solution is preferably 0.1 to 15% by mass, more preferably 0.2 to 10% by mass, and even more preferably 0.5 to 5% by mass. When the dope solution contains other components but does not contain hydrophilic inorganic particles, the total content of the other components in the dope solution is preferably 1 to 25 mass%, more preferably 5 to 25 mass%, and even more preferably 7 to 20 mass%.

[0059] <Formation of Porous Material by Wet Phase Separation> In the manufacturing method of the present invention, a hydrogen production separator is manufactured by wet phase separation of a woven fabric support placed in a coating film formed with a dope solution containing an organic polymer. In wet phase separation, the dope solution is cast onto a substrate to form a coating film, and the woven fabric support is then placed on top of the coating film. The woven fabric support is then immersed in the coating film to impregnate, preferably completely impregnate, the woven fabric support with the dope solution. The dope solution-impregnated woven fabric support is then immersed in a solvent (poor solvent, coagulation bath) that does not dissolve the organic polymer and is compatible (miscible) with the good solvent. This immersion reduces the proportion of the good solvent in the dope solution coating, resulting in phase separation between the organic polymer and the solvent (liquid-induced phase separation), gelling (coagulation) of the organic polymer, and forming a porous material containing the organic polymer. This results in a configuration in which a porous material containing the organic polymer is disposed on at least one of the outer surface and pores of the woven fabric support. The woven fabric support impregnated with the dope solution may be immersed in the poor solvent while still attached to the substrate. In this case, the separator for hydrogen production of the present invention can be obtained by peeling it off from the substrate after liquid-induced phase separation. Examples of the poor solvent include water, or a mixture of water and a hydrophilic organic solvent (a water-miscible organic solvent) or a water-soluble polymer. Examples of hydrophilic organic solvents include aprotic solvents such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylacetamide (DMAC), and alcoholic solvents such as ethanol, propanol, and isopropanol. Examples of water-soluble polymers include water-soluble polymers such as polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA). Among these, water is preferred as the poor solvent. Before immersing the membrane in the poor solvent, the membrane may be exposed to the vapor of the poor solvent to induce vapor-induced phase separation (vapor-induced phase separation). Vapor-induced phase separation allows for more precise adjustment of the pore size of the surface layer. Therefore, the wet phase separation can be carried out by combining vapor-induced phase separation and liquid-induced phase separation.

[0060] In the separator for hydrogen production obtained by the production method of the present invention, a certain amount of good solvent in the dope solution used in the production inevitably remains. As a result, a separator for hydrogen production is provided in which the total content of good solvent in the porous material is 0.01 to 5.00 mass %. The amount of residual solvent is measured by measuring the amount of residual solvent by gas chromatography or the like after the separator is dried in advance by blowing air at 40°C for 12 hours. １ Using H-NMR, the amount can be quantified as mass % based on 100 mass % of the porous separator for alkaline water electrolysis after drying.

[0061] The separator for hydrogen production of the present invention can be used as a separator in a method for producing hydrogen by electrolyzing an alkaline aqueous solution using an electrolytic cell. In particular, the separator can be suitably used as a separator for alkaline water electrolysis in the alkaline water electrolysis system described below.

[0062] [Alkaline water electrolysis] The separator for hydrogen production of the present invention (hereinafter also simply referred to as "the separator of the present invention") is disposed between the cathode and the anode in alkaline water electrolysis. Preferred embodiments of an alkaline water electrolysis system to which the separator of the present invention is applied (also referred to as "the alkaline water electrolysis system of the present invention") will be described, but the alkaline water electrolysis of the present invention is not limited to these embodiments.

[0063] Fig. 2 schematically illustrates a preferred embodiment of the alkaline water electrolysis system of the present invention. The alkaline water electrolysis system (10) illustrated in Fig. 2 includes a separator (11) of the present invention, a cathode electrode (12) on one side thereof, and an anode electrode (13) on the other side thereof, and the separator (11) and the electrodes (12, 13) are immersed in a highly concentrated alkaline aqueous solution (14, preferably a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution). When a current flows between the electrodes, electrons are supplied to the cathode side, and hydrogen bubbles (H ２ ) occurs (2H ２ O + 2e － →H ２ +2OH － Hydroxy ions (OH －) passes through the separator (11) and moves to the anode side, where electrons are taken away and oxygen (O ２ ) is generated (4OH － →O ２ +2H ２ O+4e － The cathode electrode (12) and the anode electrode (13) preferably include an electrode substrate (conductive material) and a catalyst layer on the electrode substrate. When a catalyst layer is included, the catalyst species may be the same or different between the cathode electrode (12) and the anode electrode (13). In the alkaline water electrolysis system (10) shown in FIG. 2 , the separator (11) and the electrodes (12, 13) are separated from each other, resulting in a long migration distance of hydroxy ions, which limits improvement in ion conduction efficiency.

[0064] FIG. 3 schematically illustrates another preferred embodiment of the alkaline water electrolysis system of the present invention. The alkaline water electrolysis system (20) illustrated in FIG. 3 is the same as the alkaline water electrolysis system (10) illustrated in FIG. 2 , except that the separator (11) and the electrodes (12, 13) are arranged in contact with each other (zero-gap system). The alkaline water electrolysis system (20) illustrated in FIG. 3 has a short migration distance of hydroxy ions due to the separator (11) and the electrodes (12, 13) being in contact with each other, which is advantageous in terms of ion conduction efficiency. Examples of pressurized alkaline water electrolysis systems include the alkaline water electrolysis system illustrated in FIG. 3 , where the configuration, components, and the like of the alkaline water electrolysis system are appropriately adjusted to accommodate pressurized operation (e.g., operation under a pressurized condition of 5 bar or more). For example, the separator (11) may be circular so as to withstand pressurized operation. Furthermore, typical components used in pressurized alkaline water electrolysis systems can also be appropriately applied to other components.

[0065] FIG. 4 is a schematic diagram illustrating yet another preferred embodiment of the alkaline water electrolysis system of the present invention. The alkaline water electrolysis system (30) illustrated in FIG. 4 includes a membrane electrode assembly. That is, a cathode catalyst layer (32) is disposed on one side of a separator (31) of the present invention, and an anode catalyst layer (33) is disposed on the other side. These catalyst layers are composed of a catalyst and a binder. Furthermore, a gas diffusion layer (34) is formed on the outer surface of each catalyst layer (the surface opposite to the side on which the separator (33) is disposed) to form a membrane electrode assembly. In FIG. 4 , a bipolar plate (35) is formed on the outer side of the membrane electrode assembly. An alkaline aqueous solution is supplied to the cathode catalyst layer (32) and the anode catalyst layer (33) of this membrane electrode assembly, and the cathode catalyst layer (32) and the anode catalyst layer (33) are electrically connected and energized, whereby hydrogen bubbles are generated from the cathode catalyst layer (32) and oxygen bubbles are generated from the anode catalyst layer (33).

[0066] In the alkaline water electrolysis system, the configurations of the cathode electrode, cathode catalyst layer, anode electrode, anode catalyst layer, etc., other than the separator are not particularly limited, and typical components used in alkaline water electrolysis systems can be applied as appropriate.

[0067] Thus, one embodiment of the present invention provides an alkaline water electrolysis system incorporating the separator of the present invention as a separator for the alkaline water electrolysis system. Also, one embodiment of the present invention provides a method for producing an alkaline water electrolysis system, comprising incorporating the separator of the present invention as a separator for the alkaline water electrolysis system.

[0068] [Alkaline Water Electrolysis Member] The alkaline water electrolysis member of the present invention includes the separator of the present invention. Specifically, the alkaline water electrolysis member of the present invention includes the separator of the present invention and at least one of a catalyst, an anode electrode, and a cathode electrode. Note that an embodiment including the separator of the present invention and an anode electrode and a cathode electrode is classified as the alkaline water electrolysis cell of the present invention, which will be described later. Examples of an alkaline water electrolysis member of the present invention that does not include an electrode and includes a catalyst include a structure in which the catalyst is located only on one side of the separator of the present invention, and a structure in which the catalyst is located on both sides of the separator of the present invention. Examples of an alkaline water electrolysis member of the present invention that does not include a cathode electrode and includes an anode electrode include a structure in which the anode electrode is located on one side of the separator of the present invention. In this structure, the catalyst may or may not be located. When a catalyst is located, the catalyst may be located only on one side of the separator of the present invention, or may be located on both sides of the separator of the present invention. An example of a configuration in which the alkaline water electrolysis device of the present invention does not include an anode electrode but includes a cathode electrode is a configuration in which the cathode electrode is located on one side of the separator of the present invention. In this configuration, a catalyst may or may not be included. When a catalyst is included, the catalyst may be located on only one side of the separator of the present invention, or may be located on both sides of the separator of the present invention.

[0069] [Alkaline Water Electrolysis Cell] The alkaline water electrolysis cell of the present invention comprises the separator of the present invention or the alkaline water electrolysis member of the present invention. The "alkaline water electrolysis cell" comprises a separator and two electrodes (an anode electrode and a cathode electrode) separated by the separator. In this configuration, an alkaline aqueous solution may be present as an electrolyte between both electrodes (including the separator of the present invention), and the anode electrode and the cathode electrode may each further comprise a catalyst. For example, when the alkaline water electrolysis cell of the present invention comprises the separator of the present invention, the alkaline water electrolysis cell of the present invention can be obtained by combining the separator of the present invention with the anode electrode and the cathode electrode. In this case, the anode electrode and the cathode electrode may each independently contain a catalyst. Alternatively, when the alkaline water electrolysis cell of the present invention does not comprise electrodes but comprises the separator of the present invention and a catalyst, the alkaline water electrolysis cell of the present invention can be obtained by combining the separator with the anode electrode and the cathode electrode. In this case, the catalyst may be contained in the alkaline water electrolysis element of the present invention, or may be separately contained in the alkaline water electrolysis element of the present invention and combined with it, similar to the anode electrode or cathode electrode. In the alkaline water electrolysis cell of the present invention, the catalyst may be contained on at least one side of the separator of the present invention, or may be contained on both sides. When the alkaline water electrolysis cell of the present invention does not include a cathode electrode but includes the separator of the present invention and an anode electrode, the alkaline water electrolysis cell of the present invention can be produced by combining the separator with the cathode electrode. In this case, the anode electrode and the cathode electrode may each independently contain a catalyst. The catalyst may be contained in the alkaline water electrolysis element of the present invention, or may be separately contained in the alkaline water electrolysis element of the present invention and combined with it, similar to the cathode electrode. When the alkaline water electrolysis cell of the present invention does not include an anode electrode but includes the separator and cathode electrode of the present invention, the alkaline water electrolysis cell of the present invention can be produced by combining the separator with the anode electrode. In this case, the anode electrode and the cathode electrode may each independently contain a catalyst.The catalyst may be contained in the alkaline water electrolysis device of the present invention, or may be separately contained in the alkaline water electrolysis device of the present invention in combination with it, similar to the anode electrode.

[0070] [Alkaline water electrolysis device] The alkaline water electrolysis device of the present invention includes the alkaline water electrolysis cell of the present invention. The alkaline water electrolysis device of the present invention can produce hydrogen as described in the alkaline water electrolysis system described above by supplementing necessary components, configuration, etc. depending on the configuration of the alkaline water electrolysis cell of the present invention.

[0071] [Hydrogen production method] A preferred example of the hydrogen production method of the present invention is a method comprising operating the alkaline water electrolysis apparatus of the present invention described above at a pressure of 5 bar or more. In the present invention, "operating at a pressure of 5 bar or more" means operating while controlling the pressure of the gas flow generated from each electrode chamber using a pressure control valve so that a pressure of 5 bar or more is applied to at least one of the cathode electrode chamber and the anode electrode chamber (or both). In an alkaline water electrolysis system, of the electrolytic cells separated by a separator, the electrolytic cell containing the cathode electrode is referred to as the cathode electrode chamber, and the electrolytic cell containing the anode electrode is referred to as the anode electrode chamber. The pressure applied to at least one of the cathode electrode chamber and the anode electrode chamber is preferably 5 to 500 bar, more preferably 10 to 300 bar, and even more preferably 20 to 100 bar. It is also preferable that the above pressure is applied to both the cathode electrode chamber and the anode electrode chamber. The separator of the present invention included in the alkaline water electrolysis device of the present invention can be suitably applied to a pressurized alkaline water electrolysis system and can therefore be used in a hydrogen production method in which the alkaline water electrolysis device is operated at a pressure of 5 bar or more, enabling efficient hydrogen production.

[0072] Another preferred example of the hydrogen production method of the present invention includes adjusting the pressure control valve of the alkaline water electrolysis device of the present invention to operate the device under conditions in which the hydrogen generation side is at a pressure 50 mbar or more higher than the oxygen generation side (operating under conditions in which the pressure difference obtained by subtracting the pressure on the oxygen generation side from the pressure on the hydrogen generation side is 50 mbar or more). Operating the device under this condition, applying a pressure of 50 mbar or more from the hydrogen generation side to the oxygen generation side, can increase the purity of the produced hydrogen. The pressure difference obtained by subtracting the pressure on the hydrogen generation side from the pressure on the oxygen generation side is preferably 50 to 10,000 mbar, more preferably 50 to 8,000 mbar, and even more preferably 50 to 5,000 mbar. The separator of the present invention included in the alkaline water electrolysis device of the present invention is suitable for use in pressurized alkaline water electrolysis systems and can therefore be used in a hydrogen production method in which a pressure of 5 bar or more is applied from the hydrogen generation side to the oxygen generation side of the alkaline water electrolysis device, enabling efficient production of higher purity hydrogen. In this case, the pressure difference obtained by subtracting the pressure on the oxygen generation side from the pressure on the hydrogen generation side is preferably 50 to 10,000 mbar, and more preferably 50 to 8,000 mbar.

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The water used was deionized water.

[0074] [Preparation of Separator for Hydrogen Production] Example 1 (1) Preparation of Support A PPS (polyphenylene sulfide) woven fabric (manufactured by NBC Meshtec, fiber diameter 56 μm, opening ratio 60%) was calendered using a calendering device (Supercalender, manufactured by Mitsui Electric Seiki Co., Ltd.; hereinafter the same shall apply) under conditions of a nip pressure of 90 kgf / cm, a roll temperature of 200°C, and a conveying speed of 20 m / min, to obtain a woven fabric support having a thickness of 70 μm and a calendering ratio of 63%. (2) Preparation of Separator for Hydrogen Production 8.5 g of polysulfone (trade name: Udel P-3500 LCD MB7, manufactured by Solvay, Mw: 80000) was added to 41.3 g of N-methylpyrrolidone (manufactured by Merck), and the mixture was stirred at 60°C for 5 hours to completely dissolve. Next, 2.4 g of PVP K30 (trade name, manufactured by Merck, polyvinylpyrrolidone) was added, and the mixture was stirred at 60°C for 1 hour. ２ 47.9 g of particles (trade name: High Purity Monoclinic Zirconias E101, manufactured by Luxfer MEL Technologies, median diameter (D50) approximately 0.8 μm) were added and stirred for 3 hours to obtain a dope solution. The obtained dope solution was cast onto a glass plate using a 250 μm thick applicator. The woven fabric support was placed on top of it and completely impregnated with the dope solution. Subsequently, the support was gently immersed in a condensation bath (pure water) cooled to 10°C for 5 minutes to form a porous structure. The separator was further washed with water at 50°C for 10 minutes and then peeled off from the glass plate. Subsequently, the separator was washed with water at 90°C for 1 hour to obtain the separator for hydrogen production of Example 1.

[0075] Example 2 A separator for hydrogen production of Example 2 was produced in the same manner as in Example 1, except that a woven fabric support having a thickness of 50 μm and a calendering ratio of 71% was used as the woven fabric support in Example 1. Example 3 A separator for hydrogen production of Example 3 was produced in the same manner as in Example 1, except that a woven fabric support having a thickness of 80 μm and a calendering ratio of 67% was used as the woven fabric support in Example 1. The woven fabric support was a woven fabric support having a thickness of 80 μm and a calendering ratio of 67% was used as the woven fabric support in Example 1. The woven fabric support was a PPS woven fabric (manufactured by NBC Meshtec, fiber diameter 35 μm, open area ratio 60%) was calendered in a calendering device under conditions of a nip pressure of 80 kgf / cm, a roll temperature of 200° C., and a conveying speed of 20 m / min. Example 4 A separator for hydrogen production of Example 4 was produced in the same manner as in Example 1, except that a woven fabric support having a thickness of 210 μm and a calendering ratio of 70% was used as the woven fabric support in Example 1. The woven fabric support was obtained by calendering a PPS woven fabric (manufactured by NBC Meshtec, fiber diameter 150 μm, open area ratio 60%) in a calendering device under conditions of a nip pressure of 110 kgf / cm, a roll temperature of 200°C, and a conveying speed of 15 m / min. Example 5 A separator for hydrogen production of Example 5 was produced in the same manner as in Example 1, except that a woven fabric support having a thickness of 100 μm and a calendering ratio of 67% was used as the woven fabric support in Example 1. The woven fabric support was obtained by calendering a PEEK (polyether ether ketone) woven fabric (manufactured by SAFER, fiber diameter 75 μm, open area ratio 60%) in a calendering device under conditions of a nip pressure of 100 kgf / cm, a roll temperature of 200°C, and a conveying speed of 10 m / min. Example 6 A separator for hydrogen production of Example 6 was produced in the same manner as in Example 1, except that the organic polymer in the dope solution in Example 1 was changed from polysulfone to polyphenylsulfone (product name: Ultrason P, manufactured by BASF, Mw 16000).Example 7 A separator for hydrogen production of Example 7 was produced in the same manner as in Example 1, except that a woven fabric support having a thickness of 120 μm and a calendering ratio of 67% was used as the woven fabric support in Example 1. The woven fabric support was obtained by calendering a PP (polypropylene) woven fabric (manufactured by NBC Meshtec, fiber diameter 90 μm, opening ratio 60%) in a calendering device under conditions of a nip pressure of 50 kgf / cm, a roll temperature of 140° C., and a conveying speed of 20 m / min. Example 8 A separator for hydrogen production of Example 8 was produced in the same manner as in Example 1, except that the organic polymer in the dope solution in Example 1 was changed from polysulfone to polyethersulfone (trade name: Sumikaexcel 5900P, manufactured by Sumitomo Chemical Co., Ltd.). Example 9 A separator for hydrogen production of Example 9 was produced in the same manner as in Example 1, except that the organic polymer in the dope solution in Example 1 was changed from polysulfone to polyvinylidene fluoride (product name: Solef 6010, manufactured by Solvay).

[0076] Comparative Example 1 A separator for hydrogen production in Comparative Example 1 was produced in the same manner as in Example 1, except that a woven fabric support having a thickness of 90 μm and a calendering ratio of 75% was used as the woven fabric support in Example 1. The woven fabric support was obtained by calendering a PPS woven fabric (manufactured by NBC Meshtec, fiber diameter 60 μm, open area ratio 60%) in a calendering device under conditions of a nip pressure of 70 kgf / cm, a roll temperature of 170°C, and a conveying speed of 20 m / min. Comparative Example 2 A separator for hydrogen production in Comparative Example 2 was produced in the same manner as in Example 1, except that a woven fabric support having a thickness of 260 μm and a calendering ratio of 87% was used as the woven fabric support in Example 1. The woven fabric support was obtained by calendering a PPS woven fabric (manufactured by NBC Meshtec, fiber diameter 150 μm, open area ratio 60%) in a calendering device under conditions of a nip pressure of 90 kgf / cm, a roll temperature of 180°C, and a conveying speed of 20 m / min. Comparative Example 3 A separator for hydrogen production of Comparative Example 3 was produced in the same manner as in Example 1, except that a PPS woven fabric (manufactured by NBC Meshtec, fiber diameter 60 μm, thickness 110 μm, opening ratio 60%, calendaring ratio 92%) was used as the woven fabric support without being subjected to calendaring.

[0077] The following measurements and evaluations were carried out on each hydrogen production separator. The configurations of each hydrogen production separator and the results are shown in Table 1.

[0078] [Dimensional Stability During Assembly of Electrolytic Cell] The obtained hydrogen production separator was immersed in pure water for 1 hour. This was cut into a circle with a diameter of 10 cm. A tension of 150 N was applied to the obtained circular hydrogen production separator for 5 minutes in the fiber axis direction of one of the orthogonal fibers and in a direction oblique at 45 degrees to the fiber axis direction, respectively, to prepare an observation sample. The circularity was measured according to the following method. The obtained observation sample was placed on a flat table and photographed so that the entire sample was included. The photographed image was analyzed using image processing software ImageJ (developed by the National Institutes of Health), and the obtained circularity was applied to the following criteria to evaluate the dimensional stability during assembly of the electrolytic cell. Note that the circularity is defined as 4πS / L, where S is the area of ​​the observation sample and L is the perimeter of the observation sample. ２ and is an index for evaluating the degree of conformity to a perfect circle (circularity of 1). - Evaluation criteria - A: Circularity is 0.90 or more. B: Circularity is 0.87 or more and less than 0.90. C: Circularity is less than 0.87.

[0079] (Ionic Resistance) The obtained separator for hydrogen production was immersed in a 30% by mass aqueous solution of potassium hydroxide (manufactured by Kanto Chemical Co., Inc.) at room temperature (25°C) overnight (20 hours), and then punched out into a circular shape with a diameter of 10 mm to prepare a measurement sample. A 30% by mass aqueous solution of potassium hydroxide was added as an electrolyte to a two-compartment cell having a nickel electrode at the current control terminal and a Luggin capillary filled with a 3M aqueous solution of KCl at the voltage control terminal, and the cell was maintained at 90°C. The current density was measured in galvanostat mode at 10 mA / cm. ２ The ionic resistance was measured under the conditions of 0.015 MPa and 0.015 MPa, and a blank value for the measurement was obtained. Next, the measurement sample prepared above was sandwiched between two separators, and a 30 mass% potassium hydroxide aqueous solution was similarly filled, and the ionic resistance was measured under the same conditions. The difference between the resistance value of the measurement sample and the blank value was taken as the ionic resistance value of the separator for hydrogen production.

[0080] [Operation of alkaline water electrolysis cell] The obtained hydrogen production separators were immersed in pure water for 1 hour. They were cut into circular shapes with a diameter of 10 cm, and the obtained circular hydrogen production separators were used in pressurized alkaline water electrolysis cells. It was confirmed that none of the hydrogen production separators prepared in Examples 1 to 9 protruded from the cell during assembly of the pressurized alkaline water electrolysis cell, and hydrogen could be produced without causing problems such as electrolyte leakage and gas leaks due to defects. On the other hand, all of the hydrogen production separators prepared in Comparative Examples 1 to 3 sometimes protruded from the cell, causing problems such as electrolyte leakage and gas leaks due to defects. The pressurized alkaline water electrolysis cells were prepared, operated, and evaluated as follows. Both sides of the separator were sandwiched with Ni foam (thickness 160 μm, porosity 110 PPI (pore per inch)) manufactured by Goodfellow Corp. as electrodes, and the separator was sandwiched between two Ni bipolar plates with flow channels and restrained with bolts. A 7.0 M potassium hydroxide (KOH) aqueous solution heated to 90°C was supplied to the cathode and anode sides of each of the water electrolysis cells obtained above at a flow rate of 10 mL / min, while a current of 0.1 A / cm was applied. ２ The resulting water electrolysis cell after initial energization was used to conduct a current of 0.8 A / cm while maintained at 90°C. ２ The electrolytic cell was evaluated by applying a current at 100 V and adjusting the pressure in the anode electrode chamber and the cathode electrode chamber to 30 bar using the pressure regulating valves. Adjusting the pressure to 30 bar means applying a pressure of 30 bar to both the cathode electrode chamber and the anode electrode chamber.

[0081]

[0082] Table Notes: PPS: Polyphenylene sulfide, PEEK: Polyether ether ketone, PP: Polypropylene, PSf: Polysulfone, PPSf: Polyphenylsulfone, PES: Polyethersulfone, PVDF: Polyvinylidene fluoride, NMP: N-methylpyrrolidone. The fiber diameter d1 of the woven fabric support was calculated as the arithmetic mean value of 20 fiber diameters equidistant from the intersection of the warp and weft yarns in an optical microscope image observed with transmitted light in a 1 mm square field of view, with the plane perpendicular to the thickness direction of the woven fabric support (i.e., the front or back surface of the woven fabric support) as the observation surface. The thickness d2 of the woven fabric support was calculated as the arithmetic mean value of 20 thicknesses equidistant from the intersection of the warp and weft yarns for a 10 cm square woven fabric support using a digital micrometer (MESSMER-BUCHEL). The thickness of the hydrogen production separator is determined by taking a cross-sectional SEM (scanning electron microscope) image of a cross-section cut out of the hydrogen production separator with a razor at a magnification (e.g., 400x) that fits the separator cross-section in one field of view, measuring the thickness at 20-point intervals, assuming that no pores are present in the obtained cross-sectional SEM image (assuming that the pores are filled with an organic polymer), and calculating the arithmetic mean value of the 20 measured values.

[0083] The hydrogen production separators of Comparative Examples 1 and 2 had calendering ratios of 75% and 87%, respectively, which did not satisfy the requirements of the present invention. Furthermore, the hydrogen production separator of Comparative Example 3 was not calendered, and therefore had a calendering ratio of 92%, which did not satisfy the requirements of the present invention. The hydrogen production separators of Comparative Examples 1 to 3 were deformed by application of tension after cutting into a circle, and all had a circularity of less than 0.87. When these hydrogen production separators of Comparative Examples 1 to 3 were used in pressurized alkaline water electrolysis cells, electrolyte leakage, current leakage, and the like occurred during operation. In contrast, the hydrogen production separators of Examples 1 to 9 all had calendering ratios of 73% or less, and were only slightly deformed by application of tension after cutting into a circle. All maintained a circularity of 0.87 or greater, demonstrating excellent dimensional stability during assembly of the electrolysis cell. Furthermore, when the hydrogen production separators of Examples 1 to 9 were used in a pressurized alkaline water electrolysis cell, leakage of the electrolyte, current leakage, etc. were suppressed during operation, and hydrogen could be produced. Moreover, the hydrogen production separators of Examples 1 to 9 had an ionic resistance of 0.03 to 0.08 Ω cm. ２ The ionic resistance of the separators for hydrogen production of Comparative Examples 1 to 3 was 0.08 or 0.13 Ω cm ２The ionic conductivity was the same or smaller than that of the woven fabric support, and the ionic conductivity was increased to a comparable level or higher. It is believed that when a woven fabric support having a calendering ratio of 73% or less is used, the fiber intersections are fused by the calendering treatment, resulting in a decrease in the aperture ratio and a decrease in ionic conductivity. However, the hydrogen production separator of the present invention exhibited excellent dimensional stability and ionic conductivity at a comparable level or higher than that of a woven fabric support having a calendering ratio of more than 73%. In particular, when the woven fabric support material was at least one of polyphenylene sulfide (PPS) and polyether ether ketone (PEEK), the dimensional stability and ionic conductivity during assembly of the electrolysis cell were superior (Examples 3 and 5 compared to Example 7). Furthermore, when the organic polymer was at least one of polysulfone (PSf), polyphenylsulfone (PPSf), and polyethersulfone (PES), the dimensional stability during assembly of the electrolysis cell was superior (Examples 1, 6, and 8 compared to Example 9).

[0084] This application claims priority based on Japanese Patent Application No. 2024-055617, filed on March 29, 2024, the contents of which are incorporated herein by reference as part of the present specification.

[0085] REFERENCE SIGNS LIST 10 alkaline water electrolysis system 11 hydrogen production separator 12 cathode electrode 13 anode electrode 14 high-concentration alkaline aqueous solution 20 alkaline water electrolysis system 30 alkaline water electrolysis system 31 hydrogen production separator 32 cathode catalyst layer 33 anode catalyst layer 34 gas diffusion layer 35 bipolar plate O ２ Bubble oxygen H ２ Bubble hydrogen OH － Hydroxy ion e － Electron d2 Thickness of intersection F1 Weft F2 Warp

Claims

1. A separator for hydrogen production comprising a woven fabric support and a porous material containing an organic polymer, wherein the calendering ratio of the woven fabric support calculated by the following formula is 73% or less: Calendering ratio = {d2 / (2 x d1)} x 100% In the formula, d1 represents the fiber diameter of the woven fabric support, and d2 represents the thickness of the woven fabric support.

2. The separator for producing hydrogen according to claim 1, wherein the fiber diameter d1 of the woven fabric support is 180 μm or less.

3. The separator for producing hydrogen according to claim 1, wherein the thickness d2 of the woven fabric support is 250 μm or less.

4. The separator for producing hydrogen according to claim 1, wherein the material of the woven fabric support includes at least one of polyphenylene sulfide and polyether ether ketone.

5. The separator for producing hydrogen according to claim 1, wherein the organic polymer comprises at least one of polysulfone, polyethersulfone, and polyphenylsulfone.

6. An alkaline water electrolysis component comprising the separator for hydrogen production according to claim 1.

7. An alkaline water electrolysis cell comprising the separator for hydrogen production according to any one of claims 1 to 5 or the alkaline water electrolysis member according to claim 6.

8. An alkaline water electrolysis device comprising the alkaline water electrolysis cell according to claim 7.

9. A method for producing hydrogen, comprising operating the alkaline water electrolysis apparatus according to claim 8 at a pressure of 5 bar or more.

10. A method for producing hydrogen, comprising operating the alkaline water electrolysis apparatus according to claim 8 while applying a pressure of 50 mbar or more from the hydrogen generation side to the oxygen generation side.

11. A method for producing a separator for hydrogen production according to any one of claims 1 to 5, comprising forming a porous material containing an organic polymer by wet phase separation in a state in which a woven fabric support obtained by calendering, the woven fabric support having a calendering ratio calculated by the following formula being 73% or less, is disposed in a coating formed from a dope solution in which an organic polymer is dissolved: Calendering ratio = {d2 / (2 × d1)} × 100% In the above formula, d1 represents the fiber diameter of the woven fabric support, and d2 represents the thickness of the woven fabric support.

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