Gasket for electrolysis, electrolysis tank, and electrolysis method

Abstract

The purpose of the present invention is to provide a gasket capable of suppressing crevice corrosion while maintaining sealing performance, which is a fundamental property of a gasket. A frame-shaped gasket for electrolysis according to the present invention has a hollow portion on the inner periphery thereof, wherein: one surface is provided with at least two types of circumferentially continuous projections having differing heights; another surface has a circumferentially continuous cross-sectional shape having protrusions and recesses; and when L1 is defined as the distance from an inner-peripheral-side end to the projection provided closest to the inner peripheral side, and L2 is defined as the distance from the inner-peripheral-side end to the protrusion provided closest to the inner peripheral side, then L1 / L2 ≤ 3 is satisfied.

Description

Electrolytic gaskets, electrolytic cells, and electrolytic methods

[0001] The present invention relates to an electrolytic gasket, an electrolytic cell, and an electrolytic method.

[0002] As an electrolytic cell, a structure is known in which a cathode chamber frame, to which the cathode is attached, and an anode chamber frame, to which the anode is attached, are tightly sealed together via a diaphragm and a gasket. By tightly sealing the frames and the diaphragm via the gasket, the structure prevents the electrolyte inside the electrolytic cell from leaking to the outside. Various gaskets have been conventionally known to prevent electrolyte leakage (Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 63-216990

[0004] However, conventional gaskets could not adequately prevent the electrolyte from entering the space between the electrolytic frame and the gasket, and there was a risk of corrosion occurring on the flange surface of the electrolytic frame, especially during long-term operation. As the corrosion progressed, there were concerns that the electrolytic frame would become unusable, or that damage to the flange surface could lead to mixing of gases generated at the electrodes or leakage of the internal electrolyte, making safe operation impossible.

[0005] Therefore, the object of the present invention is to provide a gasket that can suppress crevice corrosion while maintaining the basic performance of a gasket, which is sealing performance.

[0006] In other words, the present invention is as follows: [1] An electrolytic gasket in the shape of a frame having a hollow portion on its inner circumference, wherein at least two circumferentially continuing protrusions of different heights are provided on one surface, and the other surface has a shape in which the cross section is uneven and irregular in shape, and when L1 is the distance from the inner circumference side end to the innermost protrusion, and L2 is the distance from the inner circumference side end to the innermost convex portion, the following equation (1) is satisfied: L1 / L2≦3 (1) [2] An electrolytic gasket of [1] in which, in a cross section in the thickness direction, when W is the total area of ​​the space in the region enclosed by the inner circumference side end of the innermost convex portion, the outer circumference side end of the outermost convex portion, a straight line parallel to the other surface passing through the highest point of the unevenness, and a line following the shape of the one surface, the following equation (2) is satisfied: 1 ≤ V / W ≤ 15 (2) [3] An electrolytic gasket of [1] or [2] having a core material inside, and satisfying the following formula (3) when the distance from the inner circumference end of the core material to the inner circumference end of the gasket is L3: L3 / L1 ≤ 5 (3) [4] An electrolytic gasket of any of [1] to [3] in which, in a gasket compression test in which the gasket is compressed with an average surface pressure of 2 MPa, the surface pressure of the other surface is 3 MPa or more. [5] An electrolytic gasket of any of [1] to [4] used on the anode side. [6] An electrolytic cell including an electrolytic gasket of any of [1] to [5]. [7] An electrolytic cell of [6] in which the electrolytic gasket is provided between the flange portion and the diaphragm of the electrolytic frame, and the inner circumference end of the flange portion is located on the inner circumference side of the inner circumference end of the electrolytic gasket. [8] The electrolytic cell according to [6], wherein the electrolytic gasket is provided between the flange portion of the electrolytic frame and the diaphragm, and the distance L4 from the inner circumferential end of the electrolytic gasket to the inner circumferential end of the flange portion is 5 mm or less. [9] A method for producing hydrogen using any of the electrolytic cells from [6] to [8].

[0007] The present invention provides a gasket that can suppress crevice corrosion while maintaining sealing performance.

[0008] This is a schematic diagram showing an example of an electrolytic gasket of this embodiment. This is a cross-sectional view taken along line X-X of an example in Figure 1. This is a cross-sectional view taken along line X-X of another example in Figure 1. This is a schematic diagram illustrating areas V and W. (A) is a thickness cross-section of an example of an electrolytic gasket of this embodiment. (B) is the dashed rectangle portion of (A), and is a diagram showing only the portion used to calculate areas W and V from (A). This is a schematic diagram of a part of the outer periphery of an electrolytic cell consisting of an electrolytic gasket, electrolytic frame, and diaphragm of this embodiment. This is a side view showing the entirety of an example of an alkaline water electrolytic cell. This is a diagram showing a cross-section of the zero-gap structure portion inside the electrolytic cell in the dashed rectangle portion of Figure 6. This is a plan view showing an example of an external header type element (electrolytic cell element). This is a diagram showing an overview of an electrolytic apparatus including an alkaline water electrolytic cell. This is a diagram illustrating the liquid filling test of the embodiment.

[0009] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following description and can be implemented in various modifications within the scope of its essence.

[0010] The electrolytic gasket of this embodiment will be explained using the drawings.

[0011] The electrolytic gasket of this embodiment is a frame-shaped electrolytic gasket 7 having a hollow portion 7b on its inner circumference (Figure 1). The electrolytic gasket of this embodiment has at least two circumferential projections of different heights on one surface, and the other surface has a shape in which the cross section is uneven and continues around the circumference, and when the distance from the inner circumference side end to the projection provided on the innermost side is L1, and the distance from the inner circumference side end to the convex portion provided on the innermost side is L2, the following equation (1) is satisfied: L1 / L2 ≤ 3 (1) In this specification, the side with the hollow portion 7b on the inner circumference may be referred to as the "inner circumference side", and the outside of the gasket may be referred to as the "outer circumference side". Also, the direction perpendicular to the thickness of the gasket, and the direction from the inner circumference side to the outer circumference side of the gasket or the reverse direction may be referred to as the width direction of the gasket. Also, the thickness direction cross section and thickness cross section refer to a cross section (for example, the X-X cross section in Figure 1) cut in the thickness direction along a line from the inner circumference side to the outer circumference side of the gasket. Furthermore, widening refers to the expansion that occurs when surface pressure is applied in the thickness direction, in a direction perpendicular to the thickness (especially in the width direction of the gasket).

[0012] The electrolytic gasket 7 described above is not limited to a rectangular tube with a square cross-section perpendicular to the thickness direction (i.e., a cross-section parallel to one surface) as shown in Figure 1, but may be a rectangular tube with a polygonal cross-section, a cylinder with a circular cross-section, etc. Also, the hollow portion 7b may be a cavity that penetrates the inside of the gasket 7, and the cross-sectional shape of the hollow portion is not limited to a square as shown in Figure 1, but may be a polygonal shape, a circle, etc. Also, the shape of the cross-section perpendicular to the thickness direction of the electrolytic gasket 7 may be the same throughout its entire thickness or may be different. The direction in which the hollow portion 7b penetrates may be considered the thickness direction. The thickness of the electrolytic gasket 7 is preferably 1.5 to 5.5 mm, more preferably 2.2 to 5.0 mm, and even more preferably 2.4 to 4.7 mm. The width of the electrolytic gasket 7 (i.e., the length in the width direction of the gasket) is preferably 18 to 40 mm, more preferably 23 to 35 mm.

[0013] The electrolytic gasket 7 described above has at least two types of protrusions 7c1 and 7c2 of different heights on one surface 7e (Figure 2). Furthermore, the protrusions of different heights continue circumferentially on one surface 7e of the gasket 7. "Continuing circumferentially" means that the protrusions 7c continue continuously or discontinuously on the surface. From the viewpoint of seal uniformity, it is preferable that the protrusions 7c continue continuously circumferentially on one surface of the gasket 7. Figure 2 shows an example in which two types of protrusions 7c1 and 7c2 of different heights are provided on one surface 7e, but the number of types of protrusions of different heights may be three or more. Also, Figure 2 shows an example in which four of the lowest protrusions 7c1 are provided on the inner circumference and two of the highest protrusions 7c2 are provided on the outer circumference, but the number of each type of protrusion of different heights may be the same or different. The number of each type of protrusion of different heights may be one or more. Furthermore, the protrusions of different heights may be arranged in a series of protrusions of the same height in the direction from the inner circumference to the outer circumference of the cross-section in the thickness direction, or protrusions of different heights may be arranged alternately. In particular, from the viewpoint of improving sealing performance and uniformity of the sealing state, it is preferable that the lowest protrusion 7c1 is provided on the inner circumference side of the gasket 7 (Figure 2). On the inner circumference side of the highest protrusion 7c2, it is more preferable that the height of the protrusions increases sequentially from the inner circumference side of the gasket 7 to the highest protrusion 7c2, or on the outer circumference side of the highest protrusion 7c2, it is more preferable that the height of the protrusions decreases sequentially from the highest protrusion 7c2 to the outer circumference side of the gasket 7. On the inner circumference side of the highest protrusion 7c2, it is more preferable that the height of the protrusions increases sequentially from the inner circumference side of the gasket 7 to the highest protrusion 7c2, and on the outer circumference side of the highest protrusion 7c2, it is more preferable that the height of the protrusions decreases sequentially from the highest protrusion 7c2 to the outer circumference side of the gasket 7. The height of each of the above-mentioned protrusions, which differ in height, is preferably 0.2 mm or more, and more preferably 0.4 mm or more, from the viewpoint of applying higher surface pressure at the protruding parts than at the non-protruding parts. Furthermore, from the viewpoint of protecting the diaphragm, it is preferably 3.0 mm or less, and more preferably 2.0 mm or less. The height of the lowest protrusion 7c1 is preferably 0.5 times or less the height of the highest protrusion 7c2.When the electrolytic gasket 7 is provided between the electrolytic frame and the diaphragm, one surface on which the protrusions are provided may be in contact with the diaphragm, and the other surface may be in contact with the electrolytic frame (Figure 5). The difference between the height of the highest protrusion 7c2 and the height of the lowest protrusion 7c1 among the protrusions of different heights is preferably 1.5 mm or less, and more preferably 1.0 mm or less, in order to avoid applying unnecessary stress and tension to the diaphragm between the protrusions of different heights. The height of the protrusions refers to the distance in the thickness direction from one surface 7e to a point on the surface of the protrusion 7c, and may be the longest distance (i.e., the distance to the highest point). The height of the protrusions 7c may be the same or different around the entire circumference.

[0014] In this specification, "projection" refers to a shape in the thickness cross-section that has a highest point, such as a trapezoid, triangular, semicircular, arc-shaped, or a combination thereof. The highest point may be a single point (i.e., a vertex) or a continuous plane of the same height. Among these, from the viewpoint of improving the surface pressure of the contact portion and sealing performance, a structure in which the top of the projection is a single point in the thickness cross-section (i.e., a structure in which the top is not a shape with a continuous plane of the same height) is more preferable.

[0015] The other surface 7f of the electrolytic gasket 7 described above has a shape in which the surface of the thickness-direction cross-section is uneven and continues circumferentially. Here, "uneven shape" refers to a shape in which convex and concave portions are alternately repeated, and the flat portion does not continue continuously for 2 mm or more. In Figure 2, all short flat portions of the other surface 7f are less than 2 mm, and it is more preferable that they are all less than 1 mm. It is preferable that there is no uneven shape including flat portions. If there are no flat portions, stress may concentrate on the convex portions during compression, resulting in good sealing performance, or the rubber may escape sufficiently into the concave portions, making it difficult for the widening to progress. Also, "continuing circumferentially" refers to the uneven shape continuing continuously or discontinuously on the surface. From the viewpoint of sealing uniformity, it is preferable that the uneven shape continues continuously circumferentially on the other surface of the gasket 7. The convex portions and concave portions in the above uneven shape may be rectangular (e.g., trapezoidal), approximately circular, triangular, etc. The convex portions and concave portions may be the same shape or different shapes. In particular, it is preferable that the convex portion and the concave portion have the same shape, and more preferably that they are both trapezoidal (Figures 2 and 3). The trapezoids in the concave portion and the convex portion preferably have an upper side (unit: mm) and a lower side (unit: mm) within the range of 0.1 to 2, more preferably within the range of 0.3 to 1.8, even more preferably within the range of 0.5 to 1.5, and particularly preferably within the range of 0.6 or more and less than 1. Here, the upper side may be the shorter side of the upper and lower sides of the trapezoid, and may also be the side parallel to the other surface 7f in the thickness cross section. When trapezoids of different heights are adjacent (Figures 4(A) and 4(B)), the lower side of the trapezoid in the concave portion (i.e., the trapezoid in the space portion) may be the side that passes through the vertex of the taller convex trapezoid among the adjacent convex trapezoids.

[0016] When the height of each protrusion in the above-described uneven shape is the same, the surface pressure applied to each part becomes uniform, reducing the risk of the electrolyte entering the gap between the electrolytic frame and the gasket, which can become a point of corrosion, and leading to crevice corrosion. Therefore, it is preferable that the height of each protrusion is the same. On the other hand, the depth of each recess in the above-described uneven shape may be the same or different from the viewpoint of suppressing widening. From the viewpoint of ensuring sealing performance and surface pressure, the height of the protrusion is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 1.5 mm or less, and more preferably 1.0 mm or less. Also, from the viewpoint of preventing widening, the depth of the recess is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 1.5 mm or less, and more preferably 1.0 mm or less. Note that the height of the protrusion refers to the distance in the thickness direction from the other surface 7f to a point on the surface of the protrusion, and may be the longest distance (i.e., the distance to the highest point). Furthermore, the depth of the recess refers to the distance in the depth direction from the other surface 7f to a point on the surface of the recess, and may be the longest distance (i.e., the distance to the deepest point). If both the highest point and the deepest point are on the side of one surface 7e from the other surface 7f, the point closer to the other surface 7f may be considered the highest point. If the irregularities are continuous and the surface cannot be distinguished, the other surface may be the surface of the line connecting the inner and outer edges of the other surface 7f.

[0017] The electrolytic gasket 7 described above may have non-continuous protrusions or non-continuous irregularities on one surface 7e or the other surface 7f.

[0018] In the cross-sectional view of the electrolytic gasket 7 in the thickness direction (Figures 2 and 3), L1 is defined as the distance from the inner circumference end 7a to the projection that extends circumferentially on one of the innermost surfaces 7e (Figures 2 and 3). From the viewpoint of sealing performance between the diaphragm and the gasket, and between the electrolytic frame and the gasket, particularly the former, L1 is preferably 0.1 to 4 mm, more preferably 0.2 to 3 mm, and even more preferably 0.5 to 2 mm. Here, "to the projection" in L1 may mean to the point where the height of the projection located on the innermost surface is the highest. L1 may also be defined as the distance along a straight line parallel to one of the surfaces 7e. In the electrolytic gasket of this embodiment, it is preferable that L1 / L2, L1, L2, L3 (described later), L4 (described later), the position of the point on the other surface where the surface pressure is 3.0 MPa or more, and V / W (described later) satisfy a suitable range in the cross-sectional view of the entire frame of the electrolytic gasket. Here, if the cross-section perpendicular to the thickness direction of the electrolytic gasket has a shape with corners (for example, a polygon such as a square), it is preferable that the thickness cross-section of the entire frame excluding the corners satisfies the preferred range, and it is more preferable that the thickness cross-section of the entire frame satisfies the preferred range. Also, if the cross-section perpendicular to the thickness direction of the electrolytic gasket has a shape without corners (for example, a circular shape), it is preferable that the thickness cross-section of the entire frame satisfies the preferred range.

[0019] In the cross-sectional view of the electrolytic gasket 7 in the thickness direction (Figures 2 and 3), L2 is defined as the distance from the inner circumference end 7a to the innermost convex portion (Figures 2 and 3). From the viewpoint of sealing performance between the diaphragm and the gasket, and between the electrolytic frame and the gasket, particularly the latter, L2 is preferably 0.1 to 4 mm, more preferably 0.2 to 3 mm, and even more preferably 0.5 to 2 mm. Here, "to the convex portion" in L2 may refer to the point where the height of the innermost convex portion is highest. If the highest points are consecutive, the midpoint may be used (Figures 2 and 3). L2 may also be the distance along a straight line parallel to the other surface 7f.

[0020] The electrolytic gasket 7 described above preferably satisfies the following formula (1), more preferably satisfies formula (1'), and even more preferably satisfies formula (1''), from the viewpoint of suppressing corrosion in the gap between the gasket and the electrolytic frame and suppressing widening. By satisfying the above formulas, the surface pressure on the inner circumference side becomes higher than the recess on the innermost circumference side of the other surface, so that the intrusion of electrolyte into the gap between the gasket and the electrolytic frame can be suppressed and corrosion can be suppressed. In addition, the presence of a recess on the other surface side can suppress widening. L1 / L2≦3 (1) L1 / L2≦1 (1') L1 / L2≦0.5 (1'')

[0021] Areas W and V will now be explained. In the thickness direction cross-section, let R be the region enclosed by the inner end of the innermost convex portion, the outer end of the outermost convex portion, a straight line parallel to the other surface passing through the highest point of the unevenness, and a line following the shape of the one surface (i.e., the region enclosed by the dotted line in Figure 4(B)). Here, the inner end of the convex portion and the outer end of the convex portion may be straight lines parallel to the thickness direction that pass through the point where the height of the convex portion 7d1 begins to change from the other surface 7f (Figures 4(A) and 4(B)). The highest point of the unevenness may be the highest point of the highest convex portion. Area W is the sum of the areas of the spatial portions within region R (for example, the total area of ​​the white portion within the region enclosed by the dotted line in Figure 4(B), and the total area of ​​the spatial portions of the unevenness). Furthermore, the area V is the sum of the areas occupied by the gasket in region R (for example, the total area of ​​the shaded portion within the region enclosed by the dotted line in Figure 4(B)). That is, the sum of area W and area V is the area of ​​region R. From the viewpoint of providing superior sealing performance, further suppressing expansion, and preventing the creation of gaps between the electrolytic frame and the gasket that could become corrosion points, it is preferable that V / W ≤ 15. Furthermore, from the viewpoint of providing superior sealing performance, further suppressing expansion, and preventing the creation of gaps between the electrolytic frame and the gasket that could become corrosion points, it is preferable that the following equation (2') is satisfied, more preferably that equation (2'') is satisfied, and even more preferably that equation (2''') is satisfied. 1 ≤ V / W ≤ 15 (2') 2 ≤ V / W ≤ 14 (2'') 4 ≤ V / W ≤ 12 (2''')

[0022] The electrolytic gasket 7 described above preferably has a core material 7g inside from the viewpoint of suppressing widening. The core material 7g is preferably provided continuously around the circumference of the gasket 7. The core material 7g is preferably provided substantially parallel to one surface 7e and / or the other surface 7f. The core material 7g may be provided from the outer peripheral end to the inner peripheral end in the thickness direction cross section, or it may be provided in a part between the outer peripheral end and the inner peripheral end (Figure 3). The core material 7g may be one or multiple (for example, having multiple core materials in the thickness direction, having multiple core materials intermittently in the direction from the outer peripheral to the inner peripheral, etc.).

[0023] From the viewpoint of achieving even better sealing performance and further suppressing widening, when the distance L3 is from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket, the electrolytic gasket 7 preferably satisfies the following equation (3), more preferably satisfies equation (3'), even more preferably satisfies equation (3''), and particularly preferably satisfies equation (3'''). L3 / L1 ≤ 5 (3) L3 / L1 ≤ 1 (3') L3 / L1 ≤ 0.85 (3'') L3 / L1 ≤ 0.7 (3''')

[0024] The electrolytic gasket 7 described above offers superior sealing performance and, from the viewpoint of preventing gaps between the electrolytic frame and the gasket that could become points of corrosion, in a gasket compression test in which the electrolytic gasket 7 is compressed with an average surface pressure of 2 MPa, it is preferable that the surface pressure on the other surface 7f is 3 MPa or more, more preferably 4 MPa or more, and even more preferably 5 MPa or more. It may also be 15 MPa or less. It is preferable that there is at least one point on the other surface 7f where the surface pressure is within the above range, it is more preferable that the surface pressure is within the above range in the area inward from three times L2, and even more preferable that the surface pressure is within the above range in the area inward from one time L2. Note that the gasket compression test refers to the test according to the method described in the examples below.

[0025] The electrolytic gasket of this embodiment can be used as part of the outer frame of the electrolytic cell, and can be placed between the electrolytic frame and the diaphragm of the electrolytic cell. In particular, it is preferable that the electrolytic gasket of this embodiment be used as the anode-side gasket. Here, the anode side refers to the electrode chamber on the anode side of the electrode chamber 5 defined by the partition wall 1, the outer frame 3 or flange portion 8, the diaphragm 4, and the gasket 7, as described later.

[0026] The electrolytic cell of this embodiment includes the electrolytic gasket of this embodiment described above. The electrolytic cell is preferably an alkaline water electrolytic cell. In the electrolytic cell, the electrolytic gasket 7 is preferably provided between the electrolytic frame having a flange portion 8 whose surface is a flange surface and the diaphragm 4. The electrolytic gasket 7 provided in the electrolytic cell may be the electrolytic gasket of this embodiment alone, or it may be combined with other electrolytic gaskets. The example in Figure 5 shows an example in which the electrolytic gasket of this embodiment is provided in the center of three electrolytic gaskets 7, and other electrolytic gaskets of any shape are provided in the other two. In the electrolytic gasket of this embodiment, it is more preferable that the flange surface 81 of the flange portion 8 of the electrolytic frame and the other surface 7f of the electrolytic gasket 7 are arranged facing each other adjacently, and that the diaphragm 4 and one surface 7e of the electrolytic gasket 7 are arranged facing each other adjacently (Figure 5). Here, the electrolytic frame in Figure 5 consists of a flange portion 8 and a partition wall 1. In this embodiment, if the outer peripheral edge of the electrolytic gasket is located outside the outer peripheral edge of the flange portion of the electrolytic frame (i.e., if there is a portion on the outer peripheral edge side of one surface or the other surface that is not in contact with the flange portion), the surface of the portion not in contact with the flange portion does not need to have an uneven shape.

[0027] In the electrolytic cell described above, it is preferable that the inner circumferential end of the flange portion 8 is located further inward than the inner circumferential end of the electrolytic frame gasket (i.e., the inner circumferential end of the flange portion is located towards the center of the inner circumference of the gasket), and it is preferable that the inner circumferential end of the flange surface 81 of the flange portion 8 is located further inward than the inner circumferential end of the electrolytic frame gasket (i.e., the inner circumferential end of the flange surface is located towards the center of the inner circumference of the gasket) (Figure 5).

[0028] The distance L4 from the inner circumferential end 7a of the electrolytic gasket 7 to the inner circumferential end of the flange portion 8 is preferably 5 mm or less, and more preferably 4 mm or less, from the viewpoint of further suppressing damage to the diaphragm. If the inner circumferential end of the flange portion 8 and the inner circumferential end of the flange surface 81 are in the same position, L4 may be replaced with the inner circumferential end of the flange surface 81. In particular, it is preferable to satisfy L4 in a structure in which the electrolytic frame gasket 7 and the flange surface 81 of the flange portion 8 of the electrolytic frame are in contact (Figure 5). L4 can be adjusted, for example, by changing the dimensions of the gasket, the dimensions of the electrolytic frame, etc.

[0029] The width of the electrolytic gasket 7 described above is preferably 50 to 150%, more preferably 70 to 130%, and even more preferably 80 to 120%, of 100% of the length of the flange surface 81 of the flange portion 8, in order to uniformly press the electrolytic frames together. Here, the length of the flange surface may be the length in the direction from the inner circumference to the outer circumference.

[0030] The electrolytic gasket 7 described above is not particularly limited, and a known insulating rubber material or resin material can be selected, and it is preferable that it contains a rubber material. From the viewpoint of preventing the rubber material of the gasket from being exposed to the electrolyte and altering or deteriorating, it is preferable that the gasket contains a fluororesin, for example, the gasket may be coated with a fluororesin. On the other hand, from the viewpoint of the moldability of the gasket, it is preferable that it does not contain a fluororesin, and whether or not to include a fluororesin can be selected depending on the purpose. In particular, from the viewpoint of suppressing gasket rupture in the electrolytic cell (especially rupture of the gasket on the anode chamber side in an alkaline water electrolytic cell), it is preferable that the fluororesin sheet covers the surface of the gasket but does not have a structure in which it is woven into the inside of the gasket. Furthermore, from the viewpoint of sealing performance between the gasket and the flange surface, it is preferable that the surface of the other surface 7f does not have a structure in which it is covered with a fluororesin sheet.

[0031] Examples of the above-mentioned rubber materials include natural rubber, isoprene rubber, styrene-butadiene rubber, butyl rubber, butadiene rubber, ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), tetrafluoroethylene-propylene rubber (FEPM), chloroprene rubber, silicone rubber, fluororubber (FKM), porous PTFE (polytetrafluoroethylene), perfluoroelastomer (FFKM), acrylic rubber, acrylonitrile / butadiene rubber, chlorosulfonated polyethylene rubber, urethane rubber, polysulfurized rubber, epichlorohydrin rubber, ethylene / acrylic rubber, isobutylene-isoprene rubber, chlorosulfonated polyethylene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, chlorotrifluoroethylene-ethylene copolymer, polyphenylene sulfide, polyethylene, polyimide, polyacetal, and crosslinked products thereof. Among these, ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), or crosslinked versions thereof are preferred from the viewpoint of chemical resistance and hardness. Furthermore, ethylene-propylene-diene rubber (EPDM) and fluororubber (FKM) are preferred from the viewpoint of elastic modulus and alkali resistance. Depending on the type of material, known crosslinking methods such as sulfur vulcanization and peroxide crosslinking can be used, and peroxide crosslinking is preferred. The above rubber material can be used individually or in combination of multiple types. The electrolytic gasket 7 is preferably made of a uniform material. For example, it is preferable that the entire electrolytic gasket 7, excluding the core material and coating layer, is made of a uniform single material. The above uniform material may be a rubber material only, or a mixture of rubber material and other materials. The rubber material included in the above uniform material may be one type or multiple types.

[0032] The electrolysis gasket 7 may have a part of its surface covered with a coating layer. The coating layer may contain a fluororesin or may consist only of a fluororesin. It may also not contain a fluororesin. Examples of the fluororesin include any one selected from the group consisting of polytetrafluoroethylene (PTFE), ethylene tetrafluoride / perfluoroalkyl vinyl ether copolymer (PFA), ethylene tetrafluoride / hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF), polytetrafluoroethylene, and polyvinyl fluoride. Among them, from the viewpoint of corrosion resistance, PTFE and PFA are preferred. The fluororesin can be used alone or in combination of two or more kinds.

[0033] The coating layer is preferably provided on at least a part of the surface including the surface where the gasket 7 and the flange portion 8 of the electrolysis frame contact and the location where the gasket 7 and the diaphragm 4 contact (Fig. 5), and more preferably provided on at least a part of only the surface including the location where the gasket 7 and the diaphragm 4 contact.

[0034] From the viewpoint of maintaining excellent sealing performance and obtaining corrosion resistance, the thickness of the coating layer is preferably 300 μm or less.

[0035] As the core material, materials including known materials such as polyvinylidene fluoride (PVDF) and polyethylene terephthalate (PET) can be used. Among them, the core material preferably contains PET. The mass ratio of PET to 100% by mass of the core material is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more. By containing PET, the sealing performance can be improved, the width expansion can be suppressed, and the elongation and contraction degree can be increased, so that it is easy to mount on the electrolytic cell.

[0036] Hereinafter, the electrolytic cell of the present embodiment will be described by taking an alkaline water electrolytic cell as an example.

[0037] (Alkaline Water Electrolyzer) Figure 6 shows an overall side view of an example of an alkaline water electrolyzer. Figure 7 shows a diagram of the zero-gap structure of an example of an alkaline water electrolyzer (a cross-sectional view of the area enclosed by the dashed rectangle in Figure 6). In the following, the alkaline water electrolyzer may be simply referred to as the electrolyzer. The electrolyzer 50 is preferably a bipolar electrolyzer, as shown in Figures 6 and 7, in which a plurality of elements 60, each having an anode 2a, a cathode 2c, a partition wall 1 separating the anode 2a and the cathode 2c, and an outer frame 3 bordering the partition wall 1, are superimposed with a diaphragm 4 and a gasket 7 in between. The elements 60 are the electrolyzer elements described above.

[0038] Furthermore, the electrolytic cell 50 may have a zero-gap structure Z formed by the diaphragm 4 being in contact with the anode 2a and cathode 2c (see Figure 7).

[0039] The electrolytic cell described above may be unipolar or bipolar. A unipolar electrolytic cell is a method of directly connecting one or more elements to a power source. It is a parallel circuit in which a cathode terminal element is provided with a diaphragm between the anode and cathode of each element arranged in parallel, and an anode terminal element is provided with a diaphragm between the cathode and each terminal element, and the power source is connected to each terminal element. A bipolar electrolytic cell is one method of connecting a large number of bipolar elements to a power source. It is a method of connecting multiple bipolar elements, each with one side as an anode and the other as a cathode, in series in the same direction, and connecting only both ends to the power source. Bipolar electrolytic cells have the advantage of being able to reduce the power supply current, and can produce large quantities of compounds or specified substances in a short time by electrolysis. Industrially, bipolar electrolytic cells are preferable to unipolar electrolytic cells because, if the output is the same, constant current and high voltage power supply equipment is cheaper and more compact.

[0040] (Element) Examples of the above-mentioned elements include elements used in unipolar electrolytic cells and bipolar elements used in bipolar electrolytic cells. A bipolar element 60 used in an example of a bipolar electrolytic cell 50 for alkaline water electrolysis includes a partition wall 1 that separates the anode 2a and the cathode 2c, and an outer frame 3 that surrounds the partition wall 1, as shown in Figure 7. More specifically, the partition wall 1 is conductive, and the outer frame 3 is provided to surround the partition wall 1 along its outer edge. The upper part including the outer frame 3 may be a flange portion 8. The above-mentioned element includes an anode 2a, a cathode current collector 2r, a conductive elastic body 2e, and a cathode 2c in this order, and may also include a partition wall 1, ribs 6, outer frame 3, flange portion 8, reverse current absorber, anode current collector, etc.

[0041] As shown in Figure 6, the electrolytic cell 50 is constructed by stacking the required number of elements 60. In the example shown in Figure 6, the electrolytic cell 50 is arranged with a fast head 51g, an insulating plate 51i, and an anode terminal element 51a in that order from one end, and then the anode-side gasket portion, diaphragm 4, cathode-side gasket portion, and element 60 are arranged in that order. At this time, the element 60 is positioned so that the cathode 2c faces the anode terminal element 51a. The anode gasket to element 60 is repeated as many times as required for the design production volume. After the required number of times the anode gasket to element 60 has been repeated, the anode-side gasket portion, diaphragm 4, and cathode-side gasket portion are arranged again, and finally the cathode terminal element 51c, insulating plate 51i, and loose head 51g are arranged in that order. The electrolytic cell 50 is assembled into a single unit by tightening the entire assembly with a tie rod 51r. The arrangement of components in the electrolytic cell 50 can be arbitrarily selected from either the anode side or the cathode side, and is not limited to the order described above.

[0042] As shown in Figure 6, in the electrolytic cell 50, element 60 is positioned between the anode terminal element 51a and the cathode terminal element 51c, and the diaphragm 4 is positioned between the anode terminal element 51a and element 60, between adjacent elements 60, and between element 60 and the cathode terminal element 51c.

[0043] In the electrolytic cell 50, as shown in Figure 7, the diaphragm 4 is in contact with the anode 2a and cathode 2c to form a zero-gap structure Z. In particular, the portion between the partition walls 1 between two adjacent elements 60 in the electrolytic cell 50, and the portion between the partition walls 1 between an adjacent element 60 and a terminal element are referred to as the electrolytic cell 65. The electrolytic cell 65 includes the diaphragm 4, the partition wall 1 of one element, the anode chamber 5a, and the anode 2a, and the cathode 2c, cathode chamber 5c, and partition wall 1 of the other element.

[0044] In alkaline water electrolysis, if there is a gap between the diaphragm 4 and the anode 2a or cathode 2c, a large amount of bubbles generated during electrolysis, in addition to the electrolyte, accumulate in this area, resulting in very high electrical resistance. To significantly reduce the electrolysis voltage in the electrolytic cell 65, it is effective to minimize the distance between the anode 2a and cathode 2c (hereinafter also referred to as the "inter-electrode distance") to eliminate the influence of the electrolyte and bubbles present between the anode 2a and cathode 2c.

[0045] Therefore, a zero-gap structure is employed that allows the anode 2a and the diaphragm 4 to be in contact with each other across the entire electrode surface, and the cathode 2c and the diaphragm 4 to be in contact with each other, or a state in which there is almost no gap between the anode 2a and the diaphragm 4 and between the cathode 2c and the diaphragm 4, with the inter-electrode distance being approximately the same as the thickness of the diaphragm 4 across the entire electrode surface.

[0046] Furthermore, in the electrolytic cell 50, as shown in Figures 7 to 8, the electrode chamber 5 through which the electrolyte passes is defined by the partition wall 1, the outer frame 3 or flange portion 8, the gasket 7, and the diaphragm 4. Here, the outer frame 3 may be the flange portion 8.

[0047] More specifically, the electrode chamber 5 has an electrolyte inlet 5i for introducing electrolyte into the electrode chamber 5 and an electrolyte outlet 5o for discharging electrolyte from the electrode chamber 5 at the boundary with the outer frame 3. More specifically, the anode chamber 5a is provided with an anode electrolyte inlet for introducing electrolyte into the anode chamber and an anode electrolyte outlet for discharging electrolyte discharged from the anode chamber 5a, and the cathode chamber 5c is provided with a cathode electrolyte inlet for introducing electrolyte into the cathode chamber 5c and a cathode electrolyte outlet for discharging electrolyte discharged from the cathode chamber 5c.

[0048] In the examples shown in Figures 6 to 8, the rectangular partition wall 1 and the rectangular membrane 4 are arranged in parallel, and the inner surface of the rectangular parallelepiped outer frame 3 provided at the edge of the partition wall 1 is perpendicular to the partition wall 1, so the shape of the electrode chamber 5 is a rectangular parallelepiped.

[0049] The electrolytic cell 50 is typically fitted with header pipes, which are tubes for distributing or collecting electrolyte. The lower part of the outer frame 3 at the edge of the partition wall 1 is equipped with an anode inlet header 10ai for supplying electrolyte to the anode chamber 5a and a cathode inlet header 10ci for supplying electrolyte to the cathode chamber 5c. Similarly, the upper part of the outer frame 3 at the edge of the partition wall 1 is equipped with an anode outlet header 10ao for discharging electrode solution from the anode chamber 5a and a cathode outlet header 10co for discharging electrolyte from the cathode chamber 5c. As shown in Figures 6 and 7, there are typically two types of header pipe arrangements for the electrolytic cell 50: an internal header type and an external header type, and either type may be used.

[0050] In the electrolytic cell 50, it is preferable that the electrolyte distributed by the anode inlet header 10ai is introduced into the anode chamber 5a through the anode electrolyte inlet, passes through the anode chamber 5a, is discharged from the anode chamber 5a through the anode electrolyte outlet, and is collected by the anode outlet header 10ao.

[0051] The components of the electrolytic cell and electrolytic cell for alkaline water electrolysis will be described in detail below.

[0052] - Partition Wall - The partition wall 1 is located between the cathode 2c and the anode 2a, and is preferably provided between the anode 2a and the cathode current collector 2r and / or between the cathode 2c and the anode current collector 2r. The shape of the partition wall may be a plate-like shape with a predetermined thickness, but is not particularly limited. The planar shape of the partition wall is not particularly limited and may be rectangular (square, rectangle, etc.) or circular (circle, ellipse, etc.), where the rectangle may have rounded corners. In one embodiment, the partition wall and the outer frame may be integrated by welding or other methods. For example, the partition wall may be provided with flange portions (anode flange portion protruding towards the anode side, cathode flange portion protruding towards the cathode side) that extend in a direction perpendicular to the plane of the partition wall, and the flange portions may be part of the outer frame.

[0053] The size of the partition wall is not particularly limited and may be designed appropriately according to the size of the electrode chamber. The thickness of the partition wall does not need to be increased if the anode rib and cathode rib are joined to the partition wall by welding or other means to form a single integrated structure, as the anode rib and cathode rib provide reinforcement. A thickness of 0.5 to 2 mm is usually sufficient.

[0054] As for the partition wall material, a material with high conductivity is preferred from the viewpoint of achieving a uniform power supply, and from the viewpoint of alkali resistance and heat resistance, nickel, nickel alloys, mild steel, and nickel alloys with nickel plating are preferred.

[0055] Here, the flange portion 8 is a portion having a flange surface that is in direct contact with an adjacent electrolytic cell element, or in contact with an adjacent electrolytic cell element via a gasket 7. For example, when the outer wall of the liquid collection tube is in contact with the outer wall of the liquid collection tube of an adjacent electrolytic cell element via a gasket 7, the liquid collection tube is also a flange portion, and the surface of the outer wall of the liquid collection tube facing the outer wall of the liquid collection tube of the adjacent electrolytic cell element is also a flange surface 81. Also, when the flange portion 8 provided at the top of the liquid collection tube is in contact with the flange portion 8 of an adjacent electrolytic cell element via a gasket 7, the surface of the outer wall of the flange portion facing the adjacent electrolytic cell element is a flange surface 81. Furthermore, when the outer wall of the liquid collection tube and the flange portion 8 provided on the upper part of the liquid collection tube are in contact with the outer wall of the liquid collection tube and the flange portion 8 provided on the upper part of the liquid collection tube of an adjacent electrolytic cell element via a gasket 7, the liquid collection tube and the flange portion are the flange portion, and the surface of the outer wall of the liquid collection tube facing the outer wall of the liquid collection tube of the adjacent electrolytic cell element and the surface of the outer wall of the flange portion facing the adjacent electrolytic cell element are the flange surface 81. The flange surface 81 may be the surface of a structure whose surface is located at the longest position in the direction perpendicular to the partition wall 1, starting from the partition wall 1 that separates the anode chamber 5a and the cathode chamber 5b. For example, if the flange portion 8 is located at the furthest position in the direction perpendicular to the partition wall 1, then the surface of the flange portion 8 may be the flange surface 81. If the anode liquid collection tube 20ao, the cathode liquid collection tube 20co, and the flange portion 8 have the surfaces furthest away in a direction perpendicular to the partition wall 1, then the surfaces of the anode liquid collection tube 20ao, the cathode liquid collection tube 20co, and the flange portion 8 may be designated as the flange surface 81.

[0056] -Electrodes- The size of electrode 2 is not particularly limited and may be determined according to the size of the electrode chamber.

[0057] In order to increase the surface area used for the electrolysis of water and to efficiently remove gases generated by the electrolysis of water from the electrode surface, it is preferable that at least one of the anode and cathode be a porous material, and more preferably that both the anode and cathode be porous materials. In particular, in the case of a zero-gap electrolytic cell, it is necessary to degas the gas generated from the back side of the contact surface with the diaphragm, so it is preferable that the surface of the electrode opposite to the surface in contact with the membrane is a through-hole.

[0058] Examples of porous materials include plain weave mesh, perforated metal, expanded metal, and metal foam.

[0059] When using perforated metal, there are no particular restrictions on dimensions, but in order to achieve both an increase in gas generation due to an increase in electrolytic surface area and efficient removal of gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, it is preferable that the hole diameter be 2 mm or more and 8 mm or less, the pitch be 2 mm or more and 10 mm or less, the opening ratio be 20% or more and 80% or less, and the thickness be 0.5 mm or more and 2 mm or less.

[0060] When using expanded metal, there are no particular restrictions on dimensions, but in order to achieve both an increase in gas generation due to an increase in electrolytic surface area and efficient removal of gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, it is preferable that the distance between centers in the short direction of the mesh (SW) is 2 mm or more and 5 mm or less, the distance between centers in the long direction of the mesh (LW) is 3 mm or more and 10 mm or less, the thickness is 0.5 mm or more and 2 mm or less, and the opening ratio is 20% or more and 80% or less.

[0061] When using metal foam, there are no particular restrictions on dimensions, but in order to achieve both an increase in gas generation due to an increase in electrolytic surface area and efficient removal of gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, a porosity of 80% to 95% and a thickness of 0.5 mm to 2.0 mm are preferable.

[0062] The base material is not particularly limited, but mild steel, stainless steel, nickel, nickel-based alloys, etc. are preferred due to their resistance to the operating environment.

[0063] The electrode may be the substrate itself, but it is preferable that the substrate has a catalyst layer with high reaction activity on its surface.

[0064] The catalyst layer of the anode 2a is preferably formed from a material with high oxygen-evolving ability and good durability. Examples of such materials include nickel or cobalt, iron or platinum group elements. These can form the catalyst layer as elemental metals, compounds such as oxides, composite oxides or alloys composed of multiple metal elements, or mixtures thereof. The form of the catalyst layer is not particularly limited; for example, it may have pores containing metal crystals. Examples of materials that can achieve the desired catalytic activity and durability include elemental metals such as palladium, iridium, platinum, gold, ruthenium, rhodium, cerium, nickel, cobalt, tungsten, iron, molybdenum, silver, copper, zirconium, titanium, hafnium, and lanthanides, as well as nickel plating, alloy plating of nickel and cobalt, nickel and iron, and LaNiO2. ３ LaCoO ３ NiCo ２ O ４ Examples include composite oxides containing nickel and cobalt, composite oxides or alloys composed of multiple metal elements, or mixtures thereof, compounds of platinum group elements such as iridium oxide, and carbon materials such as graphene. To achieve high catalytic activity and durability, multiple catalyst layers formed from the above materials may be stacked, or multiple materials may be mixed within the catalyst layer. Furthermore, organic materials such as polymer materials may be included in the material to improve durability and adhesion to the substrate.

[0065] The catalyst layer of the cathode 2c is preferably formed from a material with high hydrogen generation capacity. Examples of such materials include nickel or cobalt, iron, or platinum group elements. These can form the catalyst layer as elemental metals, compounds such as oxides, composite oxides or alloys composed of multiple metal elements, or mixtures thereof. The form of the catalyst layer is not particularly limited; for example, it may have pores containing metal crystals. Materials that can achieve the desired catalytic activity and durability include, for example, Raney alloys consisting of a combination of multiple materials such as Raney nickel, nickel and aluminum, or nickel and tin; porous coatings made by plasma spraying using nickel compounds or cobalt compounds as raw materials; alloys or composite compounds of nickel and elements selected from cobalt, iron, molybdenum, silver, copper, etc.; platinum group metals or oxides of platinum or ruthenium, which have high hydrogen generation capacity; mixtures of these platinum group metals or oxides with compounds of other platinum group elements such as iridium and palladium, or compounds of rare earth metals such as lanthanum or cerium; and carbon materials such as graphene. To achieve high catalytic activity and durability, multiple catalyst layers formed from the above materials may be laminated, or multiple materials may be mixed within the catalyst layer. Furthermore, organic materials such as polymer materials may be included in the material to improve durability and adhesion to the substrate.

[0066] The electrolysis voltage largely depends on the performance of electrode 2. By reducing the electrolysis voltage, energy consumption can be reduced in an alkaline water electrolysis system. The electrolysis voltage includes not only the voltage theoretically required for the electrolysis of water, but also the overpotential of the anodic reaction (oxygen generation), the overpotential of the cathode reaction (hydrogen generation), and the voltage due to the distance between electrodes 2a and 2c. Here, overpotential refers to the voltage that needs to be applied in excess, exceeding the theoretical decomposition potential, when a certain current is flowing. By lowering the overpotential, the electrolysis voltage can be reduced.

[0067] Preferably, electrode 2 has properties such as high conductivity, high oxygen generation capacity or hydrogen generation capacity, and high wettability of the electrolyte on the electrode 2 surface. By having such properties, the above-mentioned overvoltage can be reduced. Furthermore, it is preferable that electrode 2 has properties that make it resistant to corrosion of the substrate and catalyst layer, detachment of the catalyst layer, dissolution into the electrolyte, and adhesion of contents to the diaphragm 4, even when unstable power such as renewable energy is supplied.

[0068] -Outer Frame- The shape of the outer frame 3 in the electrolytic cell for alkaline water electrolysis is not particularly limited as long as it can frame the partition wall 1, but it may be a shape that has an inner surface along a direction perpendicular to the plane of the partition wall 1 extending over the outer edge of the partition wall 1. The shape of the outer frame is not particularly limited and may be appropriately determined according to the plan view shape of the partition wall. The dimensions of the outer frame are not particularly limited and may be designed according to the outer dimensions of the electrode chamber. In one embodiment, the partition wall and the outer frame may be integrated by welding or other methods, for example, the partition wall may be provided with flange portions that protrude in a direction perpendicular to the plane of the partition wall (anode flange portion protruding towards the anode side, cathode flange portion protruding towards the cathode side), and the flange portions may be part of the outer frame.

[0069] For the outer frame material, conductive materials are preferred, and from the standpoint of alkali resistance and heat resistance, nickel, nickel alloys, mild steel, and nickel alloys with nickel plating are preferred.

[0070] - Diaphragm - The diaphragm 4 used in the electrolytic cell 65 for alkaline water electrolysis is not particularly limited as long as it is a membrane that can conduct ions while separating the generated hydrogen gas and oxygen gas. Examples include ion exchange membranes with ion exchange capacity and porous membranes that can permeate the electrolyte. The diaphragm 4 preferably has low gas permeability, high ionic conductivity, low electron conductivity, and high strength.

[0071] --Porous Membrane-- A porous membrane has multiple fine through-pores, allowing the electrolyte to permeate through the membrane. Since ion conduction occurs when the electrolyte penetrates the porous membrane, controlling the porous structure, such as pore size, porosity, and hydrophilicity, is extremely important. On the other hand, it is also required that the membrane not allow generated gases to pass through, i.e., that it has gas barrier properties. From this perspective as well, controlling the porous structure is important.

[0072] Porous membranes have multiple fine through-pores and include polymer porous membranes, inorganic porous membranes, woven fabrics, and nonwoven fabrics. These can be manufactured using known techniques. Examples of methods for manufacturing polymer porous membranes include phase conversion (microphase separation), extraction, stretching, and wet gel stretching.

[0073] ---Polymer Materials--- Examples of polymer materials include polysulfone, polyethersulfone, polyphenylsulfone, polyvinylidene fluoride, polycarbonate, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene / ethylene copolymer, polyvinylidene fluoride, polytetrafluoroethylene, perfluorosulfonic acid, perfluorocarboxylic acid, polyethylene, polypropylene, polyphenylene sulfide, polyparaphenylenebenzobisoxazole, polyketone, polyimide, and polyetherimide. Among these, polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, and polytetrafluoroethylene are preferred, and polysulfone is more preferred. These may be used individually or in combination of two or more.

[0074] Since porous membranes exhibit ionic conductivity through the permeation of electrolytes, it is preferable that the porous structure, including pore size, porosity, and hydrophilicity, is appropriately controlled. By appropriately controlling the porous structure in a porous membrane, it is possible not only to allow the electrolyte to permeate but also to enhance the barrier against generated gases.

[0075] In order to obtain appropriate membrane properties such as separation ability and strength, it is preferable to control the pore size of the porous membrane. Furthermore, when used in alkaline water electrolysis, it is preferable to control the pore size of the porous membrane from the viewpoint of preventing the mixing of oxygen gas generated from the anode and hydrogen gas generated from the cathode, and from reducing voltage loss during electrolysis. The larger the average pore size of the porous membrane, the greater the amount of permeability per unit area, and in particular, in electrolysis, the ion permeability of the porous membrane tends to be good, making it easier to reduce voltage loss. Also, the larger the average pore size of the porous membrane, the smaller the contact surface area with alkaline water, so the degradation of the polymer tends to be suppressed. On the other hand, the smaller the average pore size of the porous membrane, the higher the separation accuracy of the porous membrane, and in electrolysis, the gas barrier properties of the porous membrane tend to be good. Furthermore, when hydrophilic inorganic particles with small particle sizes, as described later, are supported on the porous membrane, they can be firmly held without falling out. This allows the high retention capacity of the hydrophilic inorganic particles to be imparted, and this effect can be maintained over a long period of time.

[0076] From this viewpoint, in the porous membrane described above, the average pore size is preferably in the range of 0.1 to 1.0 μm. If the pore size is within this range, the porous membrane can achieve both excellent gas barrier properties and high ion permeability. Furthermore, it is preferable that the pore size of the porous membrane be controlled in the temperature range in which it is actually used. Therefore, for example, when used as a diaphragm 4 in an environment of 90°C, it is preferable that the above range of pore size is satisfied at 90°C. Moreover, as a diaphragm for alkaline water electrolysis, it is even more preferable that the average pore size of the porous membrane is in the range of 0.1 to 0.5 μm, which allows for even better gas barrier properties and high ion permeability.

[0077] The average pore size of a porous membrane can be measured by the following method. The average pore size of a porous membrane refers to the average water permeability pore size measured using an integrity tester (Sartorius Stedim Japan, "Sartocheck Junior BP-Plus") by the following method. First, the porous membrane, including the core material, is cut to a predetermined size to serve as a sample. This sample is placed in a pressure vessel of any size, and the vessel is filled with pure water. Next, the pressure vessel is kept in a constant temperature bath set to a predetermined temperature, and measurement is started after the inside of the pressure vessel reaches the predetermined temperature. When measurement begins, the upper surface of the sample is pressurized with nitrogen, and the pressure and permeation flow rate values ​​are recorded as pure water permeates through from the lower surface of the sample. The average water permeability pore size can be calculated using the pressure-permeation flow rate gradient between 10 kPa and 30 kPa, using the following Hagen-Poiseuille formula. Average permeable pore diameter (m) = {32ηLμ0 / (εP)} ０．５ Here, η is the viscosity of water (Pa·s), L is the thickness of the porous membrane (m), and μ0 is the apparent flow velocity, where μ0 (m / s) = flow rate (m ３ / s) / flow channel area (m ２ ) is the same. Also, ε is the porosity and P is the pressure (Pa).

[0078] For alkaline water electrolysis membranes, it is preferable to control the porosity of the porous membrane from the viewpoint of maintaining gas barrier properties and hydrophilicity, preventing a decrease in ion permeability due to bubble adhesion, and obtaining stable electrolysis performance (low voltage loss, etc.) over a long period of time. From the viewpoint of achieving a high level of both gas barrier properties and low voltage loss, the lower limit of the porosity of the porous membrane is preferably 30% or more, more preferably 35% or more, and even more preferably 40% or more. Furthermore, the upper limit of the porosity is preferably 70% or less, more preferably 65% ​​or less, and even more preferably 55% or less. If the porosity of the porous membrane is below the above upper limit, ions can easily permeate through the membrane, and voltage loss in the membrane can be suppressed.

[0079] The porosity of a porous membrane refers to the open porosity determined by the Archimedes method, and can be calculated using the following formula: Porosity P (%) = ρ / (1 + ρ) × 100, where ρ = (W3 - W1) / (W3 - W2), where W1 is the dry mass of the porous membrane (g), W2 is the water mass of the porous membrane (g), and W3 is the saturated mass of the porous membrane (g).

[0080] To measure porosity, a porous membrane washed with pure water is cut into three 3cm x 3cm pieces to be used as measurement samples. First, W2 and W3 of each sample are measured. Then, the porous membrane is dried in a dryer set to 50°C for 12 hours or more, and W1 is measured. Finally, the porosity is calculated from the values ​​of W1, W2, and W3. The porosity of the three samples is calculated, and the arithmetic mean of these values ​​is defined as the porosity P.

[0081] The thickness of the porous membrane is not particularly limited, but is preferably 100 to 700 μm, more preferably 100 to 600 μm, and even more preferably 200 to 600 μm. If the thickness of the porous membrane is above the lower limit, it is less likely to be torn by punctures, etc., and short circuits between electrodes are less likely. Also, gas barrier properties are improved. If the thickness is below the upper limit, voltage loss is less likely to increase. Also, the influence of variations in the thickness of the porous membrane is reduced. If the thickness of the diaphragm is 100 μm or more, it is less likely to be torn by punctures, etc., and short circuits between electrodes are less likely. Also, gas barrier properties are improved. If the thickness is 600 μm or less, voltage loss is less likely to increase. Also, the influence of variations in the thickness of the porous membrane is reduced. If the thickness of the porous membrane is 250 μm or more, even better gas barrier properties are obtained, and the strength of the porous membrane against impact is further improved. From this viewpoint, the lower limit of the porous membrane thickness is more preferably 300 μm or more, even more preferably 350 μm or more, and even more preferably 400 μm or more. On the other hand, if the thickness of the porous membrane is 700 μm or less, the resistance of the electrolyte contained in the pores during operation will not easily hinder ion permeability, and even better ion permeability can be maintained. From this viewpoint, the upper limit of the porous membrane thickness is more preferably 600 μm or less, even more preferably 550 μm or less, and even more preferably 500 μm or less.

[0082] ---Hydrophilic Inorganic Particles--- It is preferable that the porous membrane contains hydrophilic inorganic particles in order to exhibit high ion permeability and high gas barrier properties. The hydrophilic inorganic particles may be attached to the surface of the porous membrane, or some of them may be embedded in the polymer material constituting the porous membrane. Furthermore, when the hydrophilic inorganic particles are embedded in the voids of the porous membrane, they become less likely to detach from the porous membrane, and the performance of the porous membrane can be maintained for a long time.

[0083] Examples of hydrophilic inorganic particles include at least one inorganic substance selected from the group consisting of oxides or hydroxides of zirconium, bismuth, and cerium; oxides of Group IV elements of the periodic table; nitrides of Group IV elements of the periodic table; and carbides of Group IV elements of the periodic table. Among these, from the viewpoint of chemical stability, oxides of zirconium, bismuth, and cerium, and oxides of Group IV elements of the periodic table are more preferred, oxides of zirconium, bismuth, and cerium are even more preferred, and zirconium oxide is even more preferred.

[0084] The hydrophilic inorganic particles are preferably in the form of fine particles.

[0085] --Porous Support-- When a porous membrane is used as a diaphragm, the porous membrane may be used together with a porous support. Preferably, the porous membrane has a structure in which the porous support is embedded, and more preferably, the porous membrane is laminated on both sides of the porous support. Alternatively, the porous membrane may be laminated symmetrically on both sides of the porous support.

[0086] Examples of porous supports include mesh, porous membranes, nonwoven fabrics, woven fabrics, and composite fabrics containing nonwoven fabrics and woven fabrics embedded within them. These may be used individually or in combination of two or more types. More preferred embodiments of the porous support include, for example, a mesh substrate composed of polyphenylene sulfide monofilaments, or a composite fabric containing nonwoven fabrics and woven fabrics embedded within them.

[0087] --Ion Exchange Membranes-- Ion exchange membranes include cation exchange membranes that selectively allow cations to pass through and anion exchange membranes that selectively allow anions to pass through, and either type of exchange membrane can be used. The material of the ion exchange membrane is not particularly limited, and known materials can be used. For example, fluorine-containing resins and modified resins of polystyrene-divinylbenzene copolymers can be suitably used. Fluorine-containing ion exchange membranes are particularly preferred due to their excellent heat resistance and chemical resistance.

[0088] Examples of fluorine-containing ion exchange membranes include those that have the function of selectively permeating ions generated during electrolysis and contain fluorine-containing polymers having ion exchange groups. Here, a fluorine-containing polymer having ion exchange groups refers to a fluorine-containing polymer having ion exchange groups, or ion exchange group precursors that can become ion exchange groups through hydrolysis. Examples include polymers having a fluorinated hydrocarbon main chain, functional groups that can be converted into ion exchange groups through hydrolysis, etc., as pendant side chains, and that are melt-processable.

[0089] The molecular weight of the fluorine-containing copolymer having ion exchange groups is not particularly limited, but is preferably 0.05 to 50 (g / 10 min) and more preferably 0.1 to 30 (g / 10 min) based on the melt flow index (MFI) value measured in accordance with ASTM:D1238 (measurement conditions: temperature 270°C, load 2160 g).

[0090] Examples of ion exchange groups found in ion exchange membranes include cation exchange groups such as sulfonic acid groups, carboxylic acid groups, and phosphate groups, and anion exchange groups such as quaternary ammonium groups.

[0091] Ion exchange membranes can be given excellent ion exchange capacity and hydrophilicity by adjusting the equivalent mass EW of the ion exchange groups. Furthermore, it is possible to control the number of smaller clusters (tiny parts in which ion exchange groups coordinate and / or adsorb water molecules), which tends to improve alkali resistance and ion selective permeability. This equivalent mass EW can be measured by salt-substituted the ion exchange membrane and back-titrating the solution with an alkaline or acidic solution. The equivalent mass EW can be adjusted by the copolymerization ratio of the raw material monomers, selection of monomer species, etc. From the viewpoint of hydrophilicity and membrane water resistance, the equivalent mass EW of the ion exchange membrane is preferably 300 or more, and from the viewpoint of hydrophilicity and ion exchange capacity, it is preferably 1300 or less.

[0092] The thickness of the ion exchange membrane is not particularly limited, but from the viewpoint of ion permeability and strength, a range of 5 to 300 μm is preferred.

[0093] Surface treatment may be applied to improve the hydrophilicity of the ion exchange membrane surface. Specifically, this may involve coating the membrane with hydrophilic inorganic particles such as zirconium oxide, or creating fine irregularities on the surface.

[0094] From the viewpoint of membrane strength, it is preferable to use the ion exchange membrane together with a reinforcing material. The reinforcing material is not particularly limited and can be a general nonwoven fabric, a woven fabric, or a porous membrane made of various materials. In this case, the porous membrane is not particularly limited, but a stretched and porous PTFE-based membrane is preferred. In the electrolytic cell of this embodiment, any of these membranes can be used without limitation.

[0095] ((Zero-gap structure)) In a zero-gap electrolytic cell 65, as a means of reducing the distance between electrodes, it is preferable to place a spring, which is an elastic body 2e, between the electrode 2 and the partition wall 1, and to support the electrode with this spring. For example, in the first example, a spring made of a conductive material may be attached to the partition wall 1, and the electrode 2 may be attached to this spring. In the second example, a spring may be attached to an electrode rib 6 attached to the partition wall 1, and the electrode 2 may be attached to that spring. When adopting such a configuration using an elastic body, it is necessary to adjust the strength of the spring, the number of springs, the shape, etc. as needed so that the pressure in contact between the electrode and the diaphragm does not become uneven.

[0096] Furthermore, by increasing the rigidity of the other electrode that is paired with the electrode supported via an elastic body (for example, by making the rigidity of the anode greater than that of the cathode), a structure that deforms less even when pressed is achieved. On the other hand, for the electrodes supported via the elastic body, by making the diaphragm a flexible structure that deforms when pressed, it is possible to absorb irregularities caused by tolerances in the manufacturing precision of the electrolytic cell and deformation of the electrodes, thereby maintaining a zero-gap structure.

[0097] More specifically, this involves attaching a current collector to the tip of a rib (rectifier plate) that is electrically in contact with the bulkhead, attaching a conductive elastic body to the upper side of the current collector, that is, the side opposite to the bulkhead, and further stacking electrodes on the upper side of the current collector, that is, the part adjacent to the conductive elastic body and facing the bulkhead, thereby forming at least a three-layer structure. The elastic body is formed by the current collector and the conductive elastic body.

[0098] The zero-gap structure Z described above includes gap structures formed between the anode terminal element 51a and the element, between elements, and between the element and the cathode terminal element 51c. In the alkaline water electrolysis cell 65, as shown in Figure 7, it is preferable that a conductive elastic body 2e and a cathode current collector 2r are provided between the cathode 2c and the partition wall 1, such that the conductive elastic body 2e is sandwiched between the cathode 2c and the cathode current collector 2r. It is also preferable that the cathode current collector 2r is in contact with the rib 6 of the cathode.

[0099] The zero-gap structure Z of the electrolytic cell 65 for alkaline water electrolysis is preferably such that, as shown in Figure 7, an element 60 is superimposed on the anode 2a side of the partition wall 1, with an anode rib 6 and anode 2a stacked in that order, and on the cathode 2c side of the partition wall 1, with a cathode rib 6, cathode current collector 2r, conductive elastic body 2e and cathode 2c stacked in that order, with a diaphragm 4 in between, so that the diaphragm 4 is in contact with the anode 2a and cathode 2c.

[0100] -Current Collector- Examples of current collectors include cathode current collectors and anode current collectors. The current collector transmits electricity to the conductive elastic material or electrodes laminated on top of it, supports the load received from them, and allows gas generated from the electrodes to pass through to the partition wall without obstruction. Therefore, the shape of the current collector is preferably expanded metal or a punched perforated plate.

[0101] The material of the current collector can be nickel, nickel alloy, stainless steel, or mild steel, depending on its conductivity and alkali resistance. However, nickel or nickel-plated mild steel or stainless steel nickel alloy is preferred for its corrosion resistance. Such current collectors are fixed to the ribs by means of spot welding, laser welding, or other methods.

[0102] -Conductive Elastic Body- The conductive elastic body is located between the current collector and the electrode and is in contact with both the current collector and the electrode. It is preferable that it transmits electricity to the electrode and does not hinder the diffusion of gas generated from the electrode. This is because if gas diffusion is hindered, the electrical resistance increases and the electrode area used for electrolysis decreases, thus reducing the electrolysis efficiency. Its most important role is to ensure tight contact between the diaphragm and the electrode by applying an appropriate and even pressure to the electrode, without damaging the diaphragm.

[0103] As the conductive elastic body, commonly known materials such as elastic bodies composed of wires can be used. The material is not limited, but nickel, nickel alloys, stainless steel, or mild steel with nickel plating are preferred in terms of conductivity and alkali resistance. For electrode substrates that can be used in zero-gap applications, electrodes with a thin wire diameter and small mesh are preferred due to their high flexibility. Commonly known substrate materials can be used for such applications.

[0104] For achieving a zero-gap structure, preferred methods of fixing electrodes include spot welding to a conductive elastic material, fixing with metal or plastic pins, or applying pressure using the elasticity of the conductive elastic material.

[0105] Furthermore, the shape of the other electrode, which is paired with the electrode supported via an elastic material, is also important. In the zero-gap configuration described above, the diaphragm is pressed more strongly against the electrode than in conventional electrolytic cells.

[0106] - Electrode Chambers - In the electrolytic cell 50, as shown in Figure 7, the electrode chambers 5 through which the electrolyte passes are defined by the partition wall 1, the outer frame 3, and the diaphragm 4. Here, the electrode chamber 5 on the anode side of the partition wall 1 is the anode chamber 5a, and the electrode chamber 5 on the cathode side is the cathode chamber 5c.

[0107] Regarding the arrangement of the header pipes in the electrolytic cell, internal header type and external header type can be adopted.

[0108] -Ribs- In the electrolytic cell 65 for alkaline water electrolysis, it is preferable that the ribs 6 are physically connected to the electrodes 2. With this configuration, the ribs 6 act as a support for the electrodes 2, making it easier to maintain the zero-gap structure Z. It is also preferable that the ribs 6 are electrically connected to the partition wall 1. Furthermore, by providing the ribs 6, it is possible to reduce the convection generated in the electrode chamber 5 due to turbulence in the flow of gas and liquid within the electrode chamber 5, thereby suppressing a local rise in the temperature of the electrolyte. Here, electrodes may be provided on the ribs, or a current collector, a conductive elastic body, and an electrode may be provided on the ribs in this order. In the example electrolytic cell for alkaline water electrolysis described above, a structure is adopted in which the cathode ribs - cathode current collector - conductive elastic body - cathode are stacked in the order of cathode ribs - cathode - cathode in the cathode chamber, and a structure is adopted in which the anode ribs - anode are stacked in the order of anode ribs - anode.

[0109] It is preferable that the ribs (anode ribs, cathode ribs) not only serve to support the anode or cathode, but also to transmit the current from the partition wall to the anode or cathode.

[0110] In an electrolytic cell for alkaline water electrolysis, it is preferable that at least a portion of the ribs be conductive, and it is even more preferable that the entire rib be conductive. With such a configuration, it is possible to suppress the rise in cell voltage due to electrode deflection.

[0111] Generally, conductive metals are used as the material for the ribs. For example, nickel-plated mild steel, stainless steel, and nickel can be used. It is especially preferable that the rib material be the same as the partition wall material, and nickel is the most preferable.

[0112] The electrodes and current collectors are usually attached to the ribs by spot welding, but other methods such as laser welding may also be used, or they may be tied together using wire or string-like materials. The ribs are fixed to the bulkhead by means of spot welding, laser welding, etc., similar to the anode or cathode.

[0113] -Gasket- In the electrolytic cell 65 for alkaline water electrolysis, as shown in Figure 7, it is preferable that a gasket 7 is sandwiched together with the diaphragm 4 between the flange portions 8 that frame the partition wall 1. The gasket 7 is used to seal the space between the element 60 and the diaphragm 4, and between the elements 60, to the electrolyte and generated gas, thereby preventing leakage of the electrolyte and generated gas to the outside of the electrolytic cell and gas mixing between the two electrode chambers.

[0114] A typical gasket structure is a rectangular or annular shape with the electrode surface cut out to match the surface in contact with the frame of the element (such as a bipolar element, anode terminal element, or cathode terminal element). Two such gaskets can be used to sandwich the diaphragm, allowing it to be stacked between elements. Furthermore, it is preferable for the gasket to have a slit portion capable of accommodating the diaphragm so that it can hold the diaphragm, and an opening that allows the accommodated diaphragm to be exposed on both surfaces of the gasket. This allows the gasket to accommodate the edge of the diaphragm within the slit portion and cover the end face of the diaphragm's edge. Therefore, leakage of electrolyte or gas from the end face of the diaphragm can be prevented more reliably.

[0115] Furthermore, it is preferable to provide a protrusion that extends from one side of the gasket. By providing such a protrusion, the protrusion is locally pressed when the device is stacked, and the diaphragm housed in the slit is pressed by the gasket at the position corresponding to the protrusion. Therefore, the gasket can hold the diaphragm more firmly, making it easier to prevent leakage of electrolyte or gas.

[0116] The gasket may have a reinforcing material (core material) embedded in it. This helps to prevent the gasket from being crushed when it is sandwiched and pressed between the frame during stacking, thus making it easier to prevent damage. Such reinforcing materials (core materials) can be made from known metal materials, resin materials, and carbon materials, specifically metals such as nickel and stainless steel, resins such as nylon, polypropylene, PVDF, PTFE, and PPS, and carbon materials such as carbon particles and carbon fibers. The shape of the reinforcing material (core material) is preferably in the form of woven fabric, nonwoven fabric, short fibers, or porous membrane. Furthermore, a protective layer may be provided on the surface of the gasket. This can improve the adhesion between the gasket and the element, and also improve the alkali resistance of the gasket. The material of such a protective layer can also be selected from the gasket material.

[0117] The thickness of a gasket is not particularly limited and is designed according to the gasket material, modulus of elasticity, and cell area.

[0118] Adhesive may be used when attaching the gasket to the element. Adhesive can be applied to one side of the gasket and attached to one side of the outer frame of the element. It is preferable to moisten the electrode surface of the element by spraying water on it after the adhesive has dried. In the case of a gasket that has a slit portion to accommodate the edge of the diaphragm in order to hold the diaphragm, the gasket may be attached while the diaphragm is being held, or the diaphragm may be held after the gasket has been attached.

[0119] -Header- An electrolytic cell for alkaline water electrolysis preferably has a cathode chamber and an anode chamber for each electrolytic cell. In order to carry out the electrolysis reaction continuously in the electrolytic cell, it is necessary to continuously supply the cathode chamber and anode chamber of each electrolytic cell with an electrolyte solution that contains a sufficient amount of the raw materials consumed by electrolysis.

[0120] Electrolytic cells are connected to electrolyte supply and discharge piping called headers, which are common to multiple electrolytic cells. Generally, the anode distribution pipe is called the anode inlet header, the cathode distribution pipe is called the cathode inlet header, the anode collection pipe is called the anode outlet header, and the cathode collection pipe is called the cathode outlet header. Elements are connected to each electrolyte distribution pipe and each electrolyte collection pipe via hoses or similar.

[0121] The material of the header is not particularly limited, but it must be able to withstand the corrosiveness of the electrolyte used and the operating conditions such as pressure and temperature. Materials such as iron, nickel, cobalt, PTFE, ETFE, PFA, polyvinyl chloride, and polyethylene may be used for the header.

[0122] Typical configurations for the headers of electrolytic cells include internal header type and external header type.

[0123] -Internal Header- An internal header type refers to a system in which the electrolytic cell and the header (a tube for distributing or collecting the electrolyte) are integrated into a single unit.

[0124] In an internal header type electrolytic cell, more specifically, the anode inlet header and cathode inlet header are provided in the lower part of the partition wall 1 and / or the outer frame 3, and are provided to extend in a direction perpendicular to the partition wall 1, and the anode outlet header and cathode outlet header are provided in the upper part of the partition wall 1 and / or the outer frame 3, and are provided to extend in a direction perpendicular to the partition wall 1.

[0125] The anode inlet header, cathode inlet header, anode outlet header, and cathode outlet header inherently present in an internal header type electrolytic cell are collectively referred to as the internal header.

[0126] As an example of an internal header type, an anode inlet header and a cathode inlet header are provided on a portion of the lower part of the outer frame at the edge of the partition wall, and similarly, an anode outlet header and a cathode outlet header are provided on a portion of the upper part of the outer frame at the edge of the partition wall. The outer frame and the anode chamber or cathode chamber are connected by an electrolyte inlet or electrolyte outlet through which the electrolyte passes.

[0127] -External Header- An external header type refers to a configuration in which the electrolytic cell and the header (a tube for dispensing or collecting the electrolyte) are separate.

[0128] In an external header type electrolytic cell, the anode inlet header and the cathode inlet header are independently provided, running parallel to the electrolytic cell and perpendicular to the energized surface of the electrolytic cell. These anode inlet headers and cathode inlet headers are connected to each element by hoses.

[0129] The anode inlet header, cathode inlet header, anode outlet header, and cathode outlet header, which are externally connected to an external header type electrolytic cell, are collectively referred to as external headers. In the example of an external header type shown in Figure 8, a tubular member is installed in a header through-hole provided in the lower part of the outer frame 3 at the edge of the partition wall 1, and the tubular member is connected to the anode inlet header 10ai and the cathode inlet header 10ci. Similarly, a tubular member (e.g., a hose or tube) is installed in a header through-hole provided in the upper part of the outer frame 3 at the edge of the partition wall 1, and this tubular member is connected to the anode outlet header 10ao and the cathode outlet header 10co.

[0130] Furthermore, internal header type and external header type electrolytic cells may have a gas-liquid separation box inside to separate the gas generated by electrolysis from the electrolyte. The mounting position of the gas-liquid separation box is not particularly limited, but it may be installed between the anode chamber and the anode outlet header, or between the cathode chamber and the cathode outlet header.

[0131] -Electrolyte- Inside the electrolytic cell, a cathode chamber frame with the cathode attached and an anode chamber frame with the anode attached are arranged with a partition wall in between. In other words, the anode chamber and the cathode chamber are separated by a partition wall. The electrolyte is supplied to these anode chamber and cathode chamber. As the electrolyte, one that is commonly used in water electrolysis can be used. For example, potassium hydroxide aqueous solution or sodium hydroxide aqueous solution can be used. Furthermore, the electrolyte concentration is preferably 5 wt% to 35 wt%, more preferably 10 wt% to 30 wt%, and even more preferably 15 wt% to 25 wt%.

[0132] ((Method for producing hydrogen)) The method for producing hydrogen using the electrolytic cell described above will now be explained. Hydrogen is produced at the cathode by applying an electric current to an electrolytic cell equipped with the anode and cathode described above, in which the electrolyte is circulated, thereby performing water electrolysis. At this time, a fluctuating power source can be used as the power source. A fluctuating power source is a power source that, unlike a power source that outputs stably, such as grid power, is a power source that originates from a renewable energy power plant and whose output fluctuates in increments of a few seconds to a few minutes. The method of renewable energy generation is not particularly limited, but examples include solar power generation and wind power generation. For example, in the case of electrolysis using an electrolytic cell, the cationic electrolyte in the electrolyte moves from the anode chamber of one element through the diaphragm to the cathode chamber of an adjacent element, and the anionic electrolyte moves from the cathode chamber of one element through the diaphragm to the anode chamber of an adjacent element. Therefore, the current during electrolysis flows along the direction in which the elements are connected in series. In other words, the current flows from the anode chamber of one element to the cathode chamber of an adjacent element through the diaphragm. During electrolysis, oxygen gas is generated in the anode chamber and hydrogen gas is generated in the cathode chamber.

[0133] The electrolytic cell 65 for alkaline water electrolysis can be used in an electrolytic cell 50, an electrolytic device 70 for alkaline water electrolysis, etc. (Fig. 9). As the above-mentioned electrolytic device 70 for alkaline water electrolysis, for example, there are devices having an electrolytic cell 50, a liquid feed pump 71 for circulating the electrolytic solution, a gas-liquid separation tank 72 for separating the electrolytic solution from hydrogen and / or oxygen, and a water replenisher for replenishing the water consumed by electrolysis. The above-mentioned electrolytic device for alkaline water electrolysis may further include a rectifier 74, an oxygen concentration meter 75, a hydrogen concentration meter 76, a flow meter 77, a pressure gauge 78, a heat exchanger 79, a pressure control valve 80, etc.

[0134] In the alkaline water electrolysis method using the above-mentioned electrolytic device for alkaline water electrolysis, the current density applied to the electrolytic cell is preferably 4 kA / m ２ to 20 kA / m ２ and more preferably 6 kA / m ２ to 15 kA / m ２ In particular, when using a variable power supply, it is preferable to set the upper limit of the current density within the above range.

[0135] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0136] (Examples 1, 3, and 4) Gaskets were manufactured using the following procedure. Three types of gaskets were manufactured or computer-modeled: an EPDM gasket with an inner circumference of 50 mm square and a width of 25 mm; an EPDM gasket with an inner circumference of 58 mm square and a width of 20 mm; and an EPDM gasket with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions, irregularities, and core material of the three types of gaskets were provided as described below. Computer modeling refers to computer simulation in the CAE analysis described later. On one surface of the gasket, three protrusions were provided that were circumferentially continuous with a height of 0.4 mm, four protrusions that were circumferentially continuous with a height of 1.3 mm, and three protrusions that were circumferentially continuous with a height of 0.4 mm, starting from the inner circumference side. The distance L1 from the inner circumference side edge 7a to the innermost protrusion was 0.85 mm. Furthermore, the other surface had a trapezoidal shape with a cross-section in the thickness direction of 0.6 mm at the top, 1.4 mm at the bottom, and a height of 0.9 mm, meaning the recess had a depth of 0.9 mm. This shape continued circumferentially at a pitch of 2 mm (distance between the midpoints of the top or bottom sides). The distance L2 from the inner circumference edge 7a to the innermost convex portion was 0.85 mm. The area V in the cross-section in the thickness direction was 41.7 mm². ２ Therefore, the area W is 8.55 mm². ２ The V / W ratio was 4.9. In addition, a core material made of PET, which is continuous around the circumference of the gasket, was embedded inside the gasket parallel to one surface. The distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was 3.5 mm. A coating layer made of PTFE (i.e., a fluororesin sheet) was provided on one surface of the gasket from the inner circumference end to the point where the height of a 1.3 mm high protrusion begins to change. Examples 1, 3, and 4 are examples in which the positions of the flange surface of the electrolytic frame and the gasket were shifted so that L4 becomes the desired dimension in the current-conducting evaluation described later.

[0137] (Example 2) Two types of gaskets were manufactured in the same manner as in Example 1, except that a core material made of PET was embedded inside the gasket parallel to one surface, and the distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was set to 0 mm.

[0138] (Example 5) An EPDM gasket with an inner circumference of 58 mm square and a width of 20 mm was manufactured in the same manner as in Example 1, except that the depths of the recesses between the protrusions on the other surface were set to 0.1 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.5 mm, 0.5 mm, 0.4 mm, 0.3 mm, and 0.2 mm from the inner circumference side. The area V in the thickness direction cross section was 42.0 mm². ２ Therefore, the area W is 3.65 mm². ２ The V / W ratio was 11.5.

[0139] (Example 6) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured or computer-modeled: one made of EPDM with an inner circumference of 58 mm square and a width of 20 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions, irregularities, and core material of the two types of gaskets were provided as described below. Computer modeling refers to the computer simulation in the CAE analysis described later. One surface of the gasket was provided with a continuous circumferential protrusion of 0.4 mm in height and another continuous circumferential protrusion of 1.3 mm in height. The distance L1 from the inner circumference end 7a to the innermost protrusion was 0.85 mm. The other surface had a trapezoidal cross-section in the thickness direction, and this shape continued continuously around the circumference. The distance L2 from the inner circumference end 7a to the innermost convex part was 0.85 mm. Furthermore, the area V in the thickness direction cross-section is 41.7 mm². ２ Therefore, the area W is 8.55 mm². ２ The V / W ratio was 4.9. A core material made of PET was embedded inside the gasket, parallel to one of its surfaces. The distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was 4.5 mm. A coating layer made of PTFE was applied to the entire surface of one of the gasket surfaces.

[0140] (Example 7) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured or computer-modeled: one made of EPDM with an inner circumference of 58 mm square and a width of 20 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions, irregularities, and core material of the two types of gaskets were provided as described below. Computer modeling refers to computer simulation in the CAE analysis described later. On one surface of the gasket, four protrusions were provided that were circumferentially continuous with a height of 0.4 mm, four protrusions that were circumferentially continuous with a height of 1.3 mm, and two protrusions that were circumferentially continuous with a height of 0.4 mm, starting from the inner circumference. The distance L1 from the inner circumference end 7a to the innermost protrusion was 0.85 mm. The other surface had a trapezoidal cross-section in the thickness direction, and this shape was maintained continuously around the circumference. The distance L2 from the inner circumference end 7a to the innermost convex portion was 0.85 mm. The area V in the thickness direction cross-section was 45.3 mm². ２ The area W is 9.45 mm². ２ The V / W ratio was 4.8. A core material made of PET was embedded inside the gasket, parallel to one of its surfaces. The distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was 3.5 mm. A coating layer made of PTFE was applied to the entire surface of one of the gasket surfaces.

[0141] (Example 8) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured or computer-modeled: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions, irregularities, and core material of the two types of gaskets were provided as described below. Computer modeling refers to computer simulation in the CAE analysis described later. On one surface of the gasket, three protrusions with a height of 0.4 mm and continuous circumferential extensions were provided from the inner circumference side, and four protrusions with a height of 1.3 mm and continuous circumferential extensions were provided. The distance L1 from the inner circumference side edge 7a to the innermost protrusion was 0.85 mm. The other surface had a trapezoidal cross-section in the thickness direction, and this shape was continuously maintained around the circumference. The distance L2 from the inner circumference end 7a to the innermost convex portion was 0.85 mm. The area V in the thickness direction cross-section was 41.7 mm². ２ Therefore, the area W is 8.55 mm². ２ The V / W ratio was 4.9. A core material made of PET was embedded inside the gasket, parallel to one of its surfaces. The distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was 3.5 mm. No coating layer was provided on the surface of the gasket.

[0142] (Comparative Example 1) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured or computer-modeled: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions, irregularities, and core material of the two types of gaskets were provided as described below. Computer modeling refers to computer simulation in the CAE analysis described later. On one surface of the gasket, four protrusions were provided that were circumferentially continuous with a height of 0.4 mm from the inner circumference, and four protrusions that were circumferentially continuous with a height of 1.3 mm. The distance L1 from the inner circumference edge 7a to the innermost protrusion was 3.5 mm. On the other surface, there was a flat surface 3.5 mm from the inner circumference edge, followed by a groove that was circumferentially continuous with a depth of 0.9 mm. In other words, it did not have an "uneven shape" in which the flat portion does not continue for more than 2 mm, and there was no distance corresponding to the distance L2 from the inner circumference end 7a to the innermost convex part. In addition, a core material made of PET was embedded inside the gasket parallel to one surface. The distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was 3.5 mm. A coating layer made of PTFE (i.e., a fluororesin sheet) was provided on one surface of the gasket in the following range, and EPDM rubber was attached to the other surface so that the fluororesin sheet was not exposed, and the fluororesin sheet was folded inside the gasket. Range of the coating layer: In the thickness direction cross section, a roughly U-shaped range connecting the following points A, B, C, and D. Note that the distance between points A and B follows the shape of three 0.4 mm high protrusions on one surface. The coating layer is provided continuously around the circumferential direction. Point A: The point on one surface where the height of the fourth 0.4 mm high protrusion from the inner circumferential end begins to change. Point B: The point on one surface at the inner circumferential end. Point C: A point on the inner circumferential end 7a of the gasket, which is the intersection of a straight line parallel to the other surface passing through a point in the thickness direction line segment from the other surface side of the core material 7g to the deepest point of the groove, and the inner circumferential end 7a of the gasket. Point D: The intersection of a straight line extending from point A towards the other surface in the thickness direction and a straight line parallel to the other surface passing through point C, which is a point located within the gasket.

[0143] (Comparative Example 2) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured or computer-modeled: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions and irregularities of both types of gaskets were provided as described below. Computer modeling refers to computer simulation in the CAE analysis described later. On one surface of the gasket, three protrusions with a height of 0.4 mm and continuous circumferential extensions were provided from the inner circumference side, and four protrusions with a height of 1.3 mm and continuous circumferential extensions were provided. The distance L1 from the inner circumference side end 7a to the innermost protrusion was 2.85 mm. On the other surface, the cross-section in the thickness direction was trapezoidal, and this shape continued continuously around the circumference. The distance L2 from the inner circumference side end 7a to the innermost convex part was 0.85 mm. Furthermore, the area V in the cross-section in the thickness direction is 41.5 mm². ２ Therefore, the area W is 8.55 mm². ２ The V / W ratio was 4.9. Furthermore, no core material was provided. No coating layer was applied to the surface of the gasket.

[0144] (Comparative Example 3) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured or computer-modeled: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions and irregularities of both types of gaskets were provided as described below. Computer modeling refers to computer simulation in the CAE analysis described later. On one surface of the gasket, seven protrusions were provided that were 0.4 mm high and continuous around the circumference. The distance L1 from the inner circumference end 7a to the innermost protrusion was 1.0 mm. On the other surface, seven protrusions were provided that were 0.8 mm high and continuous around the circumference. The distance L2 from the inner circumference end 7a to the innermost convex part was 1.0 mm. One surface was coated with fluororesin, and the coating was woven into the rubber.

[0145] (Evaluation) (Dimensions) The following dimensions were measured as follows: L1, L2: The gasket was measured with calipers or a ruler. L3: The gasket was cut, and the cross-section was measured with calipers or a ruler. V, W: The gasket was cut, the cross-section was photographed with a microscope, and V and W were calculated from the measured dimensions. For each of L1, L2, L3, V, and W, 10 points were measured excluding the corners, and the average value was calculated. Note that V and W can also be calculated by importing the measured photographs into ImageJ and processing the image. If there is a design drawing with dimensions, they may also be calculated from the design values ​​in the drawing.

[0146] (Gasket Compression Test) Under conditions of 23±3°C and 50±5% humidity, a tensile and compression testing machine (Shimadzu Autograph AG-Xplus) was used to sandwich a gasket and pressure-sensitive paper (Fujifilm pressure measurement film Prescale two-sheet type LW or LLW) between rectangular fixtures with an inner circumference of 50 mm square, an outer circumference of 96 mm square, and a flange surface of 23 mm. The gasket was compressed at an average surface pressure of 2 MPa and held for 5 minutes or more. After release, the pressure-sensitive paper was removed and analyzed using a pressure image analysis system (Fujifilm pressure image analysis system FPD-8010J) to quantify the pressure. The minimum surface pressure in the area inside the inner circumference from the inner circumference edge of the other surface, i.e., inside the position at a distance of 1x L2, is listed in Table 1.

[0147] The following crevice corrosion tests, liquid filling tests, electrical conductivity evaluations, widening evaluations, and CAE analyses were performed, and crevice corrosion, liquid filling properties, widening, and diaphragm deformation were evaluated according to the following criteria.

[0148] (Crevice Corrosion Test) A 20 x 100 mm nickel plate was prepared as a test specimen, with a 20 mm square hole drilled in the center of one end. A 20 mm wide gasket with a hole in the center was sandwiched between the 20 mm square nickel plate with a hole in the center and the test specimen, and secured with screws through the hole and tightened to 2 MPa. A potentiometer galvanostat was connected to the nickel plate to form the working electrode. A nickel mesh was used as the counter electrode, an Ag / AgCl reference electrode as the reference electrode, and 20% NaOH as the electrolyte. The specimen was maintained at a potential of +0.8 V vs. Ag / AgCl at 90°C for 50 hours. After that, the surface of the test specimen was observed visually and under a microscope to confirm the presence and degree of corrosion.

[0149] (Liquid-filled test) A 150 mm square stainless steel plate was used to sandwich a gasket with an inner circumference of 50 mm square and a width of 25 mm, or an inner circumference of 58 mm square and a width of 20 mm, with thin strips of litmus paper inserted into the grooves. Eight points on the edges were tightened using spring springs (TH type, manufactured by Tokyo Hatsujo Seisakusho) to achieve an average surface pressure of 2 MPa (Figure 10). An alkaline liquid (KOH or NaOH, concentration not specified) was then placed inside, and the device was left to stand for one week at 90°C. After that, the liquid was drained and the pressure was released. The presence or absence of discoloration of the litmus paper was checked, and it was determined that the liquid had penetrated to the groove where discoloration was observed. From the perspective of suppressing crevice corrosion by preventing the electrolyte from entering the gap between the electrolytic frame and the gasket, which can be a point of corrosion, the liquid-filled test can be considered a test to measure the effect of the gasket in suppressing crevice corrosion.

[0150] (Energy Test) Energy test refers to a current density of 6 kA / m². ２ The above procedure refers to electrolysis for 1000 hours. NaOH with a concentration of 10-30 wt% was used as the electrolyte, and an ion exchange membrane was used as the diaphragm. The size of the electrodes and electrolytic cell was not specified. After 1000 hours of electrolysis, the flange surface of the electrolytic frame was visually inspected using a magnifying glass, etc., and the presence or absence of corrosion was determined by whether or not pit-like corrosion marks that were not initially observed were found. After 1000 hours of electrolysis, the diaphragm was visually inspected and palpated, and the protectiveness of the diaphragm was determined by whether or not irreversible bending, kinking, or curvature was found in the diaphragm.

[0151] (Width widening evaluation) Using a tensile and compression testing machine in warm water at a temperature of 90±3℃, a 40mm long strip-shaped gasket was placed on a U-shaped jig consisting of a strip-shaped gasket measuring 23mm wide x 60mm long with 10mm high blocks at both ends. A rectangular jig measuring 23mm wide x 40mm long x 10mm high was placed on top, and the gasket was compressed at an average surface pressure of 8 MPa for 100 hours. The amount of change in the width direction of the gasket after the pressure was released was measured.

[0152] (CAE Analysis) Computer-aided engineering (CAE) analysis, which utilizes computer simulations, was performed under the following conditions: A 23 mm wide block was placed to sandwich the width portion of a gasket with an inner circumference of 50 mm square and a width of 25 mm, and then pressed into place. The pressing pressure was set to 2 MPa based on the projected area of ​​the block, and the deformation behavior and surface pressure distribution of the gasket were evaluated. The 23 mm direction was defined as the width direction, and the displacement in the width direction was defined as the difference between the initial gasket length in the width direction (initial length) and the gasket length in the width direction after pressing (post-press length). The amount of deformation in the width direction was then calculated using the following formula: Amount of deformation in the width direction (%) = {(post-press length - initial length) / initial length} × 100

[0153] (Crevice Corrosion) ○ (Excellent): No crevice corrosion is observed in the crevice corrosion model test or electrical evaluation. × (Poor): Crevice corrosion occurs in the crevice corrosion model test or electrical evaluation.

[0154] (Liquid sealing ability) ○ (Excellent): No liquid ingress in the liquid sealing test △ (Good): Some liquid ingress in the liquid sealing test, but only minor × (Poor): A lot of liquid ingress in the liquid sealing test

[0155] (Sealing performance) ○ (Good): No electrolyte leakage during electrical conduction evaluation. × (Poor): Electrolyte leakage observed during electrical conduction evaluation.

[0156] (Widening) ◎ (Excellent): The amount of widthwise deformation in the widening evaluation or CAE analysis is sufficiently small (5% or less) ○ (Good): The amount of widthwise deformation in the widening evaluation or CAE analysis is small and acceptable (10% or less) △ (Average): The amount of widthwise deformation in the widening evaluation or CAE analysis is unacceptably large (greater than 10%)

[0157] (Consistency in an alkaline environment (water electrolysis environment)) ◎ (Excellent): No change or deterioration from the initial state is observed in the gasket after electrical evaluation or liquid filling test. 〇 (Good): Although the gasket does not rupture after electrical evaluation or liquid filling test, change or deterioration from the initial state is observed due to contact with the liquid. × (Poor): The gasket ruptures after electrical evaluation or liquid filling test, and further significant change or deterioration from the initial state is observed.

[0158] (Diaphragm protection) ◎ (Excellent): No plastic deformation in the diaphragm at the position corresponding to distance L4 after electrical evaluation. ○ (Good): Slight plastic deformation in the diaphragm at the position corresponding to distance L4 after electrical evaluation. △ (Average): Significant plastic deformation in the diaphragm at the position corresponding to distance L4 after electrical evaluation.

[0159]

[0160] The gasket of Example 1 was a frame-shaped electrolytic gasket with a hollow portion on its inner circumference. One surface had at least two circumferential projections of different heights, and the other surface had a circumferential shape with an uneven cross-section. When L1 is the distance from the inner circumference end to the innermost projection and L2 is the distance from the inner circumference end to the innermost convex portion, the relationship L1 / L2 ≤ 3 is satisfied, resulting in excellent crevice corrosion resistance, good liquid sealing properties, good widening, excellent soundness in alkaline environments, and excellent diaphragm protection. The gasket of Example 2 had L3 = 0 mm and L3 / L1 = 0, resulting in a wider widening than Example 1. The gasket of Example 3 had a distance L4 of 4 mm from the inner circumference end of the electrolytic gasket to the inner circumference end of the flange portion, resulting in slightly inferior diaphragm protection compared to Example 1, but it was still well-rated. The gasket in Example 4 had a distance L4 of 8 mm from the inner circumference end of the electrolytic gasket to the inner circumference end of the flange, resulting in inferior diaphragm protection compared to Example 1, and was rated as poor. The gasket in Example 5 had a V / W of 11.5, but the widening evaluation result was the same as Example 3, resulting in a good result. The gasket in Example 6 had an L3 of 4.5 mm and an L3 / L1 of 5.3, resulting in slightly inferior widening and diaphragm protection compared to Example 1, with a normal degree of widening and good diaphragm protection. In the gasket compression test, the minimum surface pressure on the other surface of the gasket in Example 7 was 2.6 MPa, resulting in slightly inferior liquid-filling ability and diaphragm protection compared to Example 1, with good liquid-filling ability and good diaphragm protection. The gasket in Example 8 did not have a coating layer, so its integrity in an alkaline environment was slightly inferior to Example 1, but it was rated as good. In Comparative Example 1, the gasket's other surface did not have a circumferentially irregular cross-sectional shape. As a result, electrolyte penetrated the groove between the electrolytic frame and the gasket, causing crevice corrosion at that location. Furthermore, because the fluororesin sheet was folded into the gasket, the fluororesin sheet and the gasket separated, causing the gasket to rupture. Consequently, it failed in the crevice corrosion and liquid penetration categories, as well as in the integrity category in an alkaline environment.The gasket in Comparative Example 2 did not satisfy the relationship L1 / L2 ≤ 3, allowing electrolyte to penetrate the groove between the electrolytic frame and the gasket, resulting in crevice corrosion. In other words, it failed in the categories of crevice corrosion and liquid penetration. The gasket in Comparative Example 3 satisfied the relationship L1 / L2 ≤ 3, but lacked at least two circumferential projections of different heights on one surface. As a result, electrolyte penetrated the groove between the electrolytic frame and the gasket, causing crevice corrosion. Furthermore, because the fluororesin sheet was folded into the gasket, the fluororesin sheet and the gasket separated, causing the gasket to rupture. Therefore, it failed in the categories of crevice corrosion and liquid penetration, as well as in the category of integrity in an alkaline environment.

[0161] 1 Partition wall 2 Electrodes 2a Anode 2c Cathode 2e Conductive elastic body 2r Current collector 3 Outer frame 4 Diaphragm 5 Electrode chamber 5a Anode chamber 5c Cathode chamber 5i Electrolyte inlet 5o Electrolyte outlet 6 Rib 7 Gasket (Electrolytic gasket) 7a Inner circumference end of gasket 7b Hollow part 7c Protrusion 7c1 Lowest protrusion 7c2 Highest protrusion 7d1 Convex part 7d2 Concave part 7e One surface 7f Other surface 7g Core material 8 Flange part 81 Flange surface 10 Header 10ai Anode inlet header 10ao Anode outlet header 10ci Cathode inlet header 10co Cathode outlet header 20ao Anode collection tube 20co Cathode collection tube 50 Electrolytic cell 51g Fast head, loose head 51i Insulating plate 51a Anode terminal element 51c Cathode terminal element 51r Tie rod 60 Electrolytic cell element (bipolar element) 65 Electrolytic cell 70 Electrolytic device 71 Liquid transfer pump 72 Gas-liquid separation tank 74 Rectifier 75 Oxygen concentration meter 76 Hydrogen concentration meter 77 Flow meter 78 Pressure gauge 79 Heat exchanger 80 Pressure control valve D1 Direction of electrolyte passage Z Zero gap structure L1 Distance from inner circumference end 7a to projection extending circumferentially on one of the innermost surfaces 7e L2 Distance from inner circumference end 7a to the innermost convex part L3 Distance from inner circumference end of core material 7g to inner circumference end 7a of gasket L4 Distance from inner circumference end of electrolytic gasket to inner circumference end of flange R The sum of the area occupied by the gasket in region V, which is enclosed by the inner end of the innermost convex part, the outer end of the outermost convex part, a straight line parallel to the other surface passing through the highest point of the unevenness, and a line following the shape of one of the surfaces.W is the sum of the areas of the spatial parts in region R.

Claims

1. An electrolytic gasket in the shape of a frame having a hollow portion on its inner circumference, wherein at least two circumferential projections of different heights are provided on one surface, and the other surface has a circumferential shape with an uneven cross-section, and when L1 is the distance from the inner circumference end to the innermost projection and L2 is the distance from the inner circumference end to the innermost protrusion, the following equation (1) is satisfied: L1 / L2 ≤ 3 (1) 2. In a cross-section in the thickness direction, when W is the total area of ​​the space in the region enclosed by the inner end of the innermost convex portion, the outer end of the outermost convex portion, a straight line parallel to the other surface passing through the highest point of the irregularities, and a line following the shape of the one surface, and V is the total area occupied by the gasket, the electrolytic gasket according to claim 1 satisfies the following equation (2): 1 ≤ V / W ≤ 15 (2) 3. An electrolytic gasket according to claim 1 or 2, having a core material inside, wherein when the distance L3 is from the inner circumference end of the core material to the inner circumference end of the gasket, the following equation (3) is satisfied: L3 / L1 ≤ 5 (3) 4. In a gasket compression test in which the gasket is compressed with an average surface pressure of 2 MPa, the surface pressure of the other surface is 3 MPa or more, as described in claim 1 or 2.

5. An electrolytic gasket according to claim 1 or 2, used on the anode side.

6. An electrolytic cell comprising the electrolytic gasket according to claim 1 or 2.

7. The electrolytic cell according to claim 6, wherein the electrolytic gasket is provided between the flange portion of the electrolytic frame and the diaphragm, and the inner circumferential end of the flange portion is located on the inner circumferential side of the inner circumferential end of the electrolytic gasket.

8. The electrolytic cell according to claim 6, wherein the electrolytic gasket is provided between the flange portion of the electrolytic frame and the diaphragm, and the distance L4 from the inner circumferential end of the electrolytic gasket to the inner circumferential end of the flange portion is 5 mm or less.

9. A method for producing hydrogen using the electrolytic cell described in claim 6.

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