Diaphragm for alkaline water electrolysis, method for producing same, and alkaline water electrolyzer

Abstract

To prevent local bending of a diaphragm during operation in an alkaline water electrolytic cell equipped with the diaphragm for alkaline water electrolysis comprising a polymer porous membrane.SOLUTION: A diaphragm for alkaline water electrolysis that separates an anode chamber in which an anode is disposed and a cathode chamber in which a cathode is disposed in an alkaline water electrolytic cell includes a polymeric porous membrane integrally including a seal region sandwiched between cell-constituting members in the alkaline water electrolytic cell and a separator region disposed on an inner peripheral side of the seal region, the separator region including an inter-electrode region that is smaller than the separator region and is sandwiched between the anode and the cathode and a non-restraint region between the seal region and the inter-electrode region, and the polymeric porous membrane including a frame-shaped bulk portion having a width that spans the seal region, the non-restraint region, and the inter-electrode region.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a diaphragm for alkaline water electrolysis and an alkaline water electrolytic cell having a zero gap structure including the same. [Background technology]

[0002] In recent years, hydrogen has been attracting attention as an environmentally friendly, clean energy source because it does not produce CO2 during combustion or reaction. Alkaline water electrolysis is a well-known method for producing hydrogen. Alkaline water electrolysis generates hydrogen and oxygen by electrolyzing water using an alkaline aqueous solution as the electrolyte.

[0003] Known electrolytic cells used in alkaline water electrolysis have a structure in which a porous diaphragm is disposed between an anode chamber and a cathode chamber. The diaphragm is sandwiched between an anode chamber frame constituting the anode chamber and a cathode chamber frame constituting the cathode chamber, and the gap between the diaphragm and the frame is sealed with a gasket. An anode is disposed in the anode chamber, and a cathode is disposed in the cathode chamber. In particular, in alkaline water electrolytic cells with a zero-gap structure, the anode, diaphragm, and cathode are in close contact with each other. Alkaline water electrolytic cells with a zero-gap structure have the advantage that the electrical resistance between the diaphragm and the cathode is as small as possible and, in principle, has a low power consumption rate. Patent Document 1 discloses an alkaline water electrolytic cell with this type of zero-gap structure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6596187 Summary of the Invention [Problem to be solved by the invention]

[0005] Fig. 6 is an enlarged cross-sectional view showing the support structure of the diaphragm in a conventional alkaline water electrolytic cell with a zero-gap structure. As shown in Fig. 6, in a conventional alkaline water electrolytic cell 100 with a zero-gap structure, a seal region 141, which is the peripheral portion of the diaphragm 104, is sandwiched between an anode chamber frame 121 that constitutes an anode chamber 148 and a cathode chamber frame 122 that constitutes a cathode chamber 149. The inner peripheral side of the seal region 141 of the diaphragm 104 is a separator region 143 that is exposed to the anode chamber 148 and the cathode chamber 149 and separates the anode chamber 148 from the cathode chamber 149. An anode 131 is disposed in the anode chamber 148 so as to be in contact with the partition wall 104, and a cathode 171 is disposed in the cathode chamber 149 so as to be in contact with the partition wall 104. A gap G exists between the cathode 171 and the cathode chamber frame 122, and the cathode 171 is not in contact with the cathode chamber frame 122.

[0006] In a conventional electrolytic cell 100 during operation, the anode chamber 148 and the cathode chamber 149 are filled with a 25-35% KOH aqueous solution at 80-100°C as the electrolyte, and a voltage is applied between the electrodes 131 and 171. When the electrolytic cell 100 is assembled, the diaphragm 4 is stretched tightly, but the diaphragm 104, which is a porous diaphragm made of a polymer resin, thermally expands during operation. The seal portion 141 and the region of the separator region 143 sandwiched between the anode 131 and the cathode 171 are all constrained. Therefore, deformation due to expansion is concentrated in the unconstrained region of the diaphragm 104 (i.e., the region exposed between the cathode chamber frame 122 and the cathode 171), causing bending. This localized bending of the diaphragm 104 in an operating electrolytic cell 100 may cause the diaphragm 104 to break.

[0007] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a technology for preventing local bending of a diaphragm for alkaline water electrolysis made of a porous polymer membrane during operation of an alkaline water electrolytic cell including the diaphragm. [Means for solving the problem]

[0008] In order to solve the above problems, a diaphragm for alkaline water electrolysis according to one aspect of the present disclosure is a diaphragm for alkaline water electrolysis separating an anode chamber in which an anode is placed and a cathode chamber in which a cathode is placed of an alkaline water electrolytic cell, the diaphragm comprising: a porous polymer membrane integrally having a seal region that is sandwiched between tank-constituting members in the alkaline water electrolytic tank and a separator region that is disposed on the inner circumferential side of the seal region, the separator region includes an interelectrode region that is smaller than the separator region and is sandwiched between the anode and the cathode, and an unconstrained region between the seal region and the interelectrode region, The porous polymer membrane has a frame-shaped bulk portion having a width spanning the sealed region, the unconstrained region, and the inter-electrode region.

[0009] An alkaline water electrolytic cell according to one embodiment of the present disclosure comprises: an anode chamber frame defining the anode chamber; a cathode chamber frame defining the cathode chamber; an anode housed in the anode chamber; a cathode accommodated in the cathode chamber; the alkaline water electrolysis diaphragm disposed between the anode chamber frame and the cathode chamber frame to separate the anode chamber from the cathode chamber.

[0010] A method for producing a diaphragm for alkaline water electrolysis according to one aspect of the present disclosure includes producing a diaphragm for alkaline water electrolysis separating an anode chamber in which an anode is placed and a cathode chamber in which a cathode is placed of an alkaline water electrolytic cell, the method comprising: preparing a porous polymer membrane integrally having a seal region to be sandwiched between cell-constituting members in the alkaline water electrolytic cell and a separator region disposed on the inner circumferential side of the seal region; The separator region has an inter-electrode region that is smaller than the separator region and is sandwiched between the anode and the cathode, and an unconstrained region between the seal region and the inter-electrode region, and the method includes a step of forming, in the polymer porous membrane, an inner peripheral edge portion of the seal region, the unconstrained region, and a frame-shaped bulk portion having a width spanning the inter-electrode region by applying pressure or heat. [Effects of the Invention]

[0011] The present disclosure provides a technique for preventing local bending of a diaphragm for alkaline water electrolysis, which is made of a porous polymer membrane, during operation of an alkaline water electrolytic cell. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing the overall configuration of an alkaline water electrolytic cell according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view of the alkaline water electrolytic cell for providing a detailed explanation of the support structure for the alkaline water electrolysis diaphragm on the cell body. [Figure 3] FIG. 3 is a development view of a diaphragm for alkaline water electrolysis. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of the diaphragm for alkaline water electrolysis shown in FIG. 3 . [Figure 5] FIG. 5 is a cross-sectional view taken along line IV-IV of the diaphragm for alkaline water electrolysis shown in FIG. 3 , which is a modification of the embodiment. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing the support structure for the diaphragm of a conventional alkaline water electrolytic cell with a zero-gap structure. DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, embodiments of the present disclosure will be described with reference to the drawings. First, a schematic configuration of an alkaline water electrolytic cell (hereinafter simply referred to as "electrolytic cell 1") to which a diaphragm for alkaline water electrolysis according to the present disclosure (hereinafter simply referred to as "diaphragm 4") is applied will be described.

[0014] [Schematic configuration of electrolytic cell 1] FIG. 1 is a cross-sectional view showing a schematic configuration of an electrolytic cell 1 according to an embodiment of the present disclosure. The electrolytic cell 1 shown in FIG. 1 includes a cell body 2. The interior of the cell body 2 is separated by a diaphragm 4 into an anode chamber 48 and a cathode chamber 49. The anode chamber 48 and the cathode chamber 49 each have an electrolyte supply port and an outlet port for the alkaline solution and gas (hydrogen or oxygen) after electrolysis. An anode assembly 3 is disposed on the anode chamber 48 side of the diaphragm 4 in the electrolytic cell 1. The anode assembly 3 includes a mesh anode 31 facing the diaphragm 4, an anode conductor plate 32 provided integrally with the anode 31 around the anode 31, and a connection terminal 33 disposed on the anode conductor plate 32. A cathode assembly 7 is disposed on the cathode chamber 49 side of the diaphragm 4 in the electrolytic cell 1. The cathode assembly 7 includes a mesh-like cathode 71 facing the diaphragm 4, a cathode conductor plate 72 arranged away from the cathode 71 on the side opposite the diaphragm 4, a connection terminal 73 provided on the cathode conductor plate 72, and a conductive elastic body 74 provided between the cathode 71 and the cathode conductor plate 72. The elastic body 74 presses the cathode 71 against the diaphragm 4, forming a zero-gap structure in which the anode 31 and the diaphragm 4, and the diaphragm 4 and the cathode 71 are in close contact with each other.

[0015] The anode 31 is a known electrode that has been used as an anode for alkaline water electrolysis. Known examples of such anodes 31 include those that include a conductive substrate and a catalytic layer coating the surface of the substrate. Examples of the substrate for the anode 31 include nickel, nickel-based alloys, stainless steel, iron, and nickel-coated iron. Examples of the catalytic layer for the anode 31 include nickel-containing materials such as nickel oxide, metallic nickel, nickel hydroxide, and nickel-cobalt oxide. The cathode 71 is a known electrode that has been used as a cathode for alkaline water electrolysis. Known examples of such cathodes 71 include those that include a conductive substrate and a catalytic layer coating the surface of the substrate. Examples of the conductive substrate for the cathode 71 include nickel, nickel-based alloys, stainless steel, iron, and nickel-coated iron. Examples of the catalytic layer for the cathode 71 include precious metal oxides, nickel, cobalt, molybdenum, manganese, and oxides thereof.

[0016] When alkaline water is electrolyzed in the electrolytic cell 1 configured as described above, the anode chamber 48 and the cathode chamber 49 are filled with an electrolyte, and a voltage is applied between the anode 31 and the cathode 71. An alkaline solution such as potassium hydroxide or sodium hydroxide is used as the electrolyte. The concentration of the alkaline solution is not particularly limited, but is preferably about 25-35% by mass. The temperature of the electrolyte is also not particularly limited, but is preferably about 80-100°C. In the cathode chamber 49, electrons are supplied, causing electrolysis of the water in the electrolyte, generating hydrogen gas and hydroxide ions. The hydroxide ions in the cathode chamber 49 permeate the diaphragm 4 and move to the anode chamber 48. In the anode chamber 48, oxygen gas and water are generated from the hydroxide ions.

[0017] [Diaphragm 4] Here, a detailed description will be given of the diaphragm 4 and the support structure for the diaphragm 4. Figure 2 is an enlarged partial cross-sectional view of the electrolytic cell 1 for a detailed description of the support structure for the diaphragm 4 on the cell body 2.

[0018] 1 and 2, the cell body 2 of the electrolytic cell 1 is formed by combining an anode chamber frame 21 that defines the anode chamber 48 and a cathode chamber frame 22 that defines the cathode chamber 49. The anode chamber frame 21 and the cathode chamber frame 22 have frame surfaces 21a and 22a that face each other with a diaphragm 4 or the like disposed therebetween. The frame surface 21a of the anode chamber frame 21 and the frame surface 22a of the cathode chamber frame 22 have substantially the same shape; for example, the frame surfaces 21a and 22a are rectangular or circular strips.

[0019] The anode assembly 3, diaphragm 4, and cathode assembly 7 are sandwiched between the frame surface 21a of the anode chamber frame 21 and the frame surface 22a of the cathode chamber frame 22. More specifically, a gasket 24, an anode conductor plate 32 of the anode assembly 3, the diaphragm 4, a spacer 23, a gasket 25, a cathode conductor plate 72 of the cathode assembly 7, and a gasket 26 are arranged in this order between the frame surface 21a of the anode chamber frame 21 and the frame surface 22a of the cathode chamber frame 22. The spacer 23 can be considered an extension of the cathode chamber frame 22.

[0020] The gasket 24 is a sealing material that provides a liquid-tight seal between the anode chamber frame 21 and the anode conductor plate 32. The gasket 25 is a sealing material that provides a liquid-tight seal between the spacer 23 and the cathode conductor plate 72. The gasket 26 is a sealing material that provides a liquid-tight seal between the cathode conductor plate 72 and the cathode chamber frame 22. The gaskets 24, 25, and 26 can be made of materials such as ethylene-propylene-diene rubber (EPDM) and vulcanized or peroxide-crosslinked ethylene-propylene rubber (EPM).

[0021] The spacer 23 separates the diaphragm 4 from the cathode 71. The spacer 23 also sandwiches the diaphragm 4 in the film thickness direction in cooperation with the anode conductor plate 32. The diaphragm 4 is pressed in the film thickness direction from both sides by the anode conductor plate 32 and the spacer 23.

[0022] FIG. 3 is a developed view of the diaphragm 4, and FIGS. 4 and 5 are cross-sectional views of the diaphragm 4 shown in FIG. 3 taken along line IV-IV. The diaphragm 4 shown in FIGS. 4 and 5 is shown in a state before being clamped by the anode chamber frame 21 and the cathode chamber frame 22. As shown in FIGS. 3 and 4, the diaphragm 4 includes a porous polymer membrane 40 made of an organic polymer resin and having numerous pores throughout the entire membrane (excluding a bulk portion 42, which will be described later). Alternatively, as shown in FIGS. 3 and 5, the diaphragm 4 includes a porous polymer membrane 40 made of an organic polymer resin and having numerous pores throughout the entire membrane (excluding a bulk portion 42, which will be described later), and a sheet-like porous support 50 that supports the porous polymer membrane 40. The support 50 may be disposed inside the porous polymer membrane 40 or on one surface of the porous polymer membrane 40. The support 50 is impregnated in part or in whole with the organic polymer resin.

[0023] The organic polymer resin constituting the porous polymer membrane 40 is at least one selected from the group consisting of polysulfone, polyethersulfone, polyphenylsulfone, polyvinylidene fluoride, polycarbonate, polytetrafluoroethylene, polypropylene, polyphenylene sulfide, polyketone, polyetheretherketone, polyimide, and polyetherimide. Inorganic particles may be added to the porous polymer membrane 40. The inclusion of inorganic molecules in the membrane 4 makes the membrane 4 hydrophilic, thereby suppressing adhesion of oxygen gas and hydrogen gas bubbles to the membrane surface. Examples of inorganic particles include metal hydroxides or oxides of magnesium, zirconium, titanium, zinc, aluminum, tantalum, etc.; sulfates of calcium, barium, lead, strontium, etc.; nitrides of titanium, zirconium, hafnium, etc.; and carbides of titanium, zirconium, hafnium, etc. The support 50 is a nonwoven fabric, a woven fabric, or a composite fabric of a nonwoven fabric and a woven fabric. The support 50 is formed of at least one type of fiber selected from the group consisting of polyphenylene sulfide, polypropylene, polysulfone, polyethersulfone, polyphenylsulfone, fluorine-based resin, polyketone, polyimide, and polyetherimide.

[0024] As shown in FIGS. 3 to 5 , the diaphragm 4 includes a porous polymer membrane 40 integrally having a sealing region 41 sandwiched between cell constituent members of the electrolytic cell 1 (specifically, the anode conductive plate 32 and the spacer 23), a border region 44 disposed on the outer periphery of the sealing region 41, and a separator region 43 disposed on the inner periphery of the sealing region 41.

[0025] The edge region 44 is a band-shaped region along the outer edge of the diaphragm 4 and is the portion of the diaphragm 4 exposed to the outside of the vessel. The inner peripheral edge of the edge region 44 corresponds to the outer peripheral edge of the sealing region 41. The sealing region 41 has substantially the same shape as the frame surface 21a of the anode chamber frame 21 and the frame surface 22a of the cathode chamber frame 22. The inner peripheral edge of the sealing region 41 corresponds to the outer peripheral edge of the separator region 43. The separator region 43 is the portion of the diaphragm 4 exposed to the inside of the vessel and functions as a partition wall separating the anode chamber 48 and the cathode chamber 49. Note that although the diaphragm 4 shown in FIG. 3 is rectangular, the diaphragm 4 is not limited to a rectangular shape and may have any shape corresponding to the shapes of the anode chamber frame 21 and the cathode chamber frame 22. For example, if the anode chamber frame 21 and the cathode chamber frame 22 are annular, the diaphragm 4 may be circular.

[0026] In the electrolytic cell 1, the seal region 41 of the diaphragm 4 is pressed from both sides by frame-constituting members of the electrolytic cell 1 and is constrained by the frame-constituting members. Furthermore, of the separator region 43 of the diaphragm 4, a portion sandwiched between the anode 31 and the cathode 71 (hereinafter referred to as the "inter-electrode region 43a") is constrained by the anode 31 and the cathode 71. A gap is provided between the cathode 71 and the spacer 23 (or the cathode chamber frame 22), and the cathode 71 and the spacer 23 (or the cathode chamber frame 22) are not in direct contact. Therefore, the cathode 71 is slightly smaller than the separator region 43 of the diaphragm 4, and an unconstrained region (hereinafter referred to as the "unconstrained region 43b") of the diaphragm 4 exists between the seal region 41 and the inter-electrode region 43a.

[0027] The diaphragm 4 has a frame-shaped bulk portion 42 provided along the boundary between the seal region 41 and the separator region 43. The shape of the bulk portion 42 corresponds to the outer shape of the separator region 43 (i.e., the shapes of the anode chamber frame 21 and the cathode chamber frame 22). For example, if the outer shape of the separator region 43 is rectangular, the bulk portion 42 has a rectangular frame shape, and if the outer shape of the separator region 43 is circular, the bulk portion 42 has a circular frame shape.

[0028] The bulk portion 42 has a width spanning the inner peripheral edge of the seal region 41, the unconstrained region 43b of the separator region 43, and the outer peripheral edge of the inter-electrode region 43a of the separator region 43. The bulk portion 42 on the inner peripheral edge of the seal region 41 is sandwiched on both sides by the frame-constituting members of the electrolytic cell 1. The bulk portion 42 on the outer peripheral edge of the inter-electrode region 43a is sandwiched on both sides by the electrodes 31, 71.

[0029] The bulk portion 42 of the diaphragm 4 has a bulk structure, and the portion excluding the bulk portion 42 has a porous structure. Here, a porous structure is a structure with a high porosity and a large number of pores, whereas a "bulk structure" is a structure with a low porosity and no or almost no voids such as pores. The bulk structure of the present disclosure may include a non-porous structure with no voids such as pores, and a porous structure with pores but an extremely low porosity compared to the portion excluding the bulk portion 42 of the diaphragm 4.

[0030] In the diaphragm 4 according to this embodiment, the bulk portion 42 of the polymer porous membrane 40 (or the polymer porous membrane 40 supported by the support 50) is processed into a bulk structure by crushing or melting the numerous pores that existed in the region corresponding to the bulk portion 42, thereby being crushed or reduced in size. As such, the bulk portion 42 has a lower porosity, a higher density, and a more compact structure than other portions of the sealing region 41, and is more rigid and less likely to deform than the portion of the diaphragm 4 having a porous structure. When the diaphragm 4 includes the polymer porous membrane 40 supported by the support 50, the support 50 and the polymer porous membrane 40 are welded together by resin in the bulk portion 42, and the bulk portion 42 of the diaphragm 4 is expected to have a further improved rigidity.

[0031] The porosity of the bulk portion 42 is desirably 0 or close to 0, and is preferably 1 / 10 or less of the porosity of the portion of the diaphragm 4 excluding the bulk portion 42. The bulk portion 42 having such a porosity can have sufficient rigidity to suppress deformation of the bulk portion 42. The porosity is calculated by dividing the total volume by V [m 3 ], the volume of the gap is v [m 3When voids exist in the bulk portion 42, the voids in the bulk portion 42 are preferably closed pores (also called isolated pores).

[0032] Because ion exchange does not occur in the bulk portions 42, an excessive area of ​​the bulk portions 42 reduces the electrolysis performance of the electrolytic cell 1. Therefore, the total area of ​​the bulk portions 42 in the separator region 43 is preferably 10% or less of the area of ​​the separator region 43, and more preferably 5% or less.

[0033] When the electrolytic cell 1 is stopped, the diaphragm 4 is in a taut state, but during operation, the diaphragm 4 expands due to a rise in temperature. In a conventional electrolytic cell 100 (see FIG. 6 ), deformation due to the expansion of the diaphragm 104 is concentrated in the unconstrained region of the diaphragm 104, causing deformation such that this region bends, whereas in the diaphragm 4 according to the present disclosure, the unconstrained region 43b has high rigidity and is therefore less likely to deform, so the degree of deformation is reduced and the unconstrained region 43b does not bend.

[0034] [Method for manufacturing diaphragm 4] The method for manufacturing the membrane 4 having the above configuration includes a step of producing the polymer porous membrane 40 (or the polymer porous membrane 40 supported on the support 50) and a step of forming the bulk portion 42 in the polymer porous membrane 40.

[0035] The diaphragm 4 is a porous membrane for alkaline water electrolysis to which a bulk portion 42 has been added. Therefore, the polymer porous membrane 40 of the diaphragm 4 (or the polymer porous membrane 40 supported on the support 50) can be a polymer porous membrane manufactured by a known method for manufacturing a diaphragm for alkaline water electrolysis. The method for producing the polymer porous membrane 40 is not particularly limited, and for example, a known phase separation method may be employed. In this case, a membrane-forming stock solution is prepared by dissolving the organic polymer resin and additives in an organic solvent, and the membrane-forming stock solution is applied to a substrate to a predetermined thickness to produce a coated film sheet. The coated film sheet is immersed in a non-solvent to induce phase separation of the membrane-forming stock solution to form pores, and excess water is then removed to obtain the polymer porous membrane 40. When preparing a polymer porous membrane 40 supported on a support 50, the support 50 may be used instead of the substrate in the above-described process for producing the polymer porous membrane 40.

[0036] The bulk portion 42 can be formed in the polymer porous membrane 40 by applying pressure or heat. Pressing or the like can be used as a pressure application method. In this case, by applying pressure to the polymer porous membrane 40 using a mold for the bulk portion 42, the pressurized portions of the polymer porous membrane 40 are compressed in the thickness direction, causing the structure to become bulky, thereby forming the bulk portion 42. In addition, impulse welding, ultrasonic welding, high-frequency welding, laser welding, hot plate welding, heat pressing, or the like can be used as a heating method. In this case, by heating the polymer porous membrane 40 in accordance with the shape of the reinforcing portion 45, the resin in the heated portions melts and welds, causing the structure to become bulky, thereby forming the bulk portion 42.

[0037] [Summary] The diaphragm 4 for alkaline water electrolysis according to a first aspect of the present disclosure is a diaphragm 4 for alkaline water electrolysis that separates an anode chamber 48 in which an anode 31 is placed and a cathode chamber 49 in which a cathode 71 is placed in an alkaline water electrolytic cell 1, The alkaline water electrolytic cell (1) includes a porous polymer membrane (40) integrally having a seal region (41) sandwiched between cell-constituting members and a separator region (43) disposed on the inner circumferential side of the seal region (41), The separator region 43 has an inter-electrode region 43a that is smaller than the separator region 43 and is sandwiched between the anode 31 and the cathode 71, and a non-constrained region 43b between the seal region 41 and the inter-electrode region 43a, The porous polymer membrane 40 has a sealed region 41, a non-constrained region 43b, and a frame-shaped bulk portion 42 having a width spanning the inter-electrode region 43a.

[0038] In a diaphragm 4 having the above configuration, the unconstrained region 43b has a bulk structure and is therefore more rigid and less likely to deform than when the unconstrained region 43b has a porous structure. Therefore, even if the diaphragm 4 thermally expands during operation of the electrolytic cell 1, the degree of deformation of the unconstrained region 43b of the diaphragm 4 is limited, and the unconstrained region 43b does not bend. In this way, the present disclosure can provide a technique for preventing local bending of the diaphragm 4 during operation of the electrolytic cell 1.

[0039] A diaphragm 4 for alkaline water electrolysis according to a second aspect of the present disclosure is the diaphragm 4 for alkaline water electrolysis according to the first aspect, wherein the porosity of the bulk portion 42 is not more than 1 / 10 of the porosity of the portion of the porous polymer membrane 40 excluding the bulk portion 42.

[0040] According to the diaphragm 4 having the above-described configuration, the bulk portion 42 of the diaphragm 4 can have sufficient rigidity to suppress deformation of the diaphragm 4 due to thermal expansion.

[0041] A diaphragm 4 for alkaline water electrolysis according to a third aspect of the present disclosure is the diaphragm 4 for alkaline water electrolysis according to the first or second aspect, wherein the area of ​​the bulk portion 42 in the separator region 43 is 10% or less of the area of ​​the separator region 43.

[0042] The diaphragm 4 having the above configuration can achieve a balance between the rigidity required to prevent local bending of the diaphragm 4 during operation of the electrolytic cell 1 and the maintenance of electrolytic performance.

[0043] An alkaline water electrolytic cell 1 according to a fourth item of the present disclosure comprises an anode chamber frame 21 that defines an anode chamber 48, a cathode chamber frame 22 that defines a cathode chamber 49, an anode 31 housed in the anode chamber 48, a cathode 71 housed in the cathode chamber 49, and the diaphragm 4 for alkaline water electrolysis according to any of the first to third items that is disposed between the anode chamber frame 21 and the cathode chamber frame 22 to separate the anode chamber 48 from the cathode chamber 49.

[0044] In the diaphragm 4 of the electrolytic cell 1 configured as described above, the unconstrained region 43b has a bulk structure that provides high rigidity and is less likely to deform than when the unconstrained region 43b has a porous structure. Therefore, even if the diaphragm 4 thermally expands during operation of the electrolytic cell 1, the degree of deformation of the unconstrained region 43b of the diaphragm 4 is limited, and the unconstrained region 43b does not bend. In this way, the present disclosure provides a technique for preventing local bending of the diaphragm 4 during operation of the electrolytic cell 1.

[0045] A fifth aspect of the present disclosure relates to a method for producing a diaphragm 4 for alkaline water electrolysis that separates an anode chamber 48 containing an anode 31 and a cathode chamber 49 containing a cathode 71 in an alkaline water electrolytic cell 1, the method comprising: a step of preparing a porous polymer membrane (40) integrally having a seal region (41) to be sandwiched between cell-constituting members in an alkaline water electrolytic cell (1) and a separator region (43) disposed on the inner circumferential side of the seal region (41); The separator region 43 has an inter-electrode region 43a that is smaller than the separator region 43 and is sandwiched between the anode 31 and the cathode 71, and an unconstrained region 43b between the seal region 41 and the inter-electrode region 43a, and the method includes a step of forming, by pressure or heat, a frame-shaped bulk portion 42 in the polymer porous membrane 40, the inner peripheral edge of the seal region 41, the unconstrained region 43b, and a width spanning the inter-electrode region 43a.

[0046] According to the above-described method for manufacturing the diaphragm 4, it is possible to easily manufacture the diaphragm 4 having the bulk portion 42 that prevents the diaphragm 4 from being locally bent during operation of the high temperature electrolytic cell 1.

[0047] The present disclosure has been presented for purposes of illustration and description and is not intended to be limited to the form disclosed herein. For example, in the foregoing Detailed Description, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure, but some of the features may also be combined. Also, the features included in the present disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above. [Explanation of symbols]

[0048] 1: Alkaline water electrolysis tank 4: Diaphragm for alkaline water electrolysis 21: Anode chamber frame 22: Cathode chamber frame 31: Anode 40: Polymer porous membrane 41: Sealing area 42: Bulk section 43: Separator area 44: Edge region 48:Anode chamber 49: Cathode chamber 71 :Cathode

Claims

1. A diaphragm for alkaline water electrolysis separating an anode chamber in which an anode is placed and a cathode chamber in which a cathode is placed of an alkaline water electrolytic cell, a porous polymer membrane integrally having a seal region that is sandwiched between tank-constituting members in the alkaline water electrolytic tank and a separator region that is disposed on the inner circumferential side of the seal region, the separator region includes an interelectrode region that is smaller than the separator region and is sandwiched between the anode and the cathode, and an unconstrained region between the seal region and the interelectrode region, the porous polymer membrane has a frame-shaped bulk portion having a width spanning the sealed region, the unconstrained region, and the inter-electrode region; Diaphragm for alkaline water electrolysis.

2. the porosity of the bulk portion is 1 / 10 or less of the porosity of the portion of the polymer porous membrane excluding the bulk portion; The diaphragm for alkaline water electrolysis according to claim 1.

3. an area of ​​the bulk portion in the separator region relative to an area of ​​the separator region is 10% or less; The diaphragm for alkaline water electrolysis according to claim 1 or 2.

4. an anode chamber frame defining the anode chamber; a cathode chamber frame defining the cathode chamber; an anode housed in the anode chamber; a cathode accommodated in the cathode chamber; the diaphragm for alkaline water electrolysis according to claim 1 or 2, which is disposed between the anode chamber frame and the cathode chamber frame to separate the anode chamber from the cathode chamber. Alkaline water electrolyzer.

5. A method for manufacturing a diaphragm for alkaline water electrolysis that separates an anode chamber in which an anode is placed and a cathode chamber in which a cathode is placed of an alkaline water electrolytic cell, comprising: preparing a porous polymer membrane integrally having a seal region to be sandwiched between cell-constituting members in the alkaline water electrolytic cell and a separator region disposed on the inner circumferential side of the seal region; the separator region has an inter-electrode region that is smaller than the separator region and is sandwiched between the anode and the cathode, and an unconstrained region between the seal region and the inter-electrode region, and the method includes a step of forming, in the polymer porous membrane, by pressure or heat, a frame-shaped bulk portion having a width spanning an inner peripheral edge portion of the seal region, the unconstrained region, and the inter-electrode region; Method for manufacturing diaphragms for alkaline water electrolysis.

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