Internal manifold type bipolar electrolytic element, electrolytic cell, and method for producing hydrogen

Abstract

The present invention provides an internal manifold type bipolar electrolysis element which is composed of a positive electrode, a negative electrode, a partition wall and an outer frame, while having a manifold, and which is characterized in that: at least a part of the surface of the manifold is covered with a manifold covering member; and the manifold covering member is integrated with a gasket.

Description

[Technical Field]

[0001] The present invention relates to an internal manifold type bipolar electrolytic element, an electrolytic cell using the internal manifold type bipolar electrolytic element, and a method for producing hydrogen using the electrolytic cell. [Background technology]

[0002] In recent years, renewable energy technologies such as wind power generation and solar power generation have been attracting attention in order to solve problems such as global warming caused by greenhouse gases such as carbon dioxide and dwindling fossil fuel reserves.

[0003] Renewable energy output is highly variable because it depends on weather conditions. As a result, it is not always possible to transport the electricity generated by renewable energy to the general power grid, raising concerns about the potential for imbalances in power supply and demand and the instability of the power grid.

[0004] Therefore, research is being conducted into using electricity generated from renewable energy sources in a form that can be stored and transported.Specifically, research is being conducted into generating storable and transportable hydrogen through the electrolysis of water using electricity generated from renewable energy sources, and using this hydrogen as an energy source or raw material.

[0005] Hydrogen is widely used industrially in oil refining, chemical synthesis, metal refining, etc., and in recent years, the possibility of its use has expanded in hydrogen stations for fuel cell vehicles (FCVs), smart communities, hydrogen power plants, etc. For this reason, there are particularly high expectations for the development of technology to obtain hydrogen from renewable energy sources.

[0006] Methods for electrolyzing water include solid polymer water electrolysis, high-temperature steam electrolysis, alkaline water electrolysis, etc. Of these methods, alkaline water electrolysis is considered to be one of the most promising, since it has been industrialized for more than several decades, can be implemented on a large scale, and is inexpensive compared to other water electrolysis systems.

[0007] However, in order to adapt alkaline water electrolysis as a means for storing and transporting energy in the future, it is necessary to enable water electrolysis using electric power, which has large output fluctuations as described above, efficiently and stably. Therefore, there is a need to solve various issues with electrolytic cells and devices for alkaline water electrolysis.

[0008] In alkaline water electrolysis, a reduction reaction of water occurs at the cathode during electrolysis, and the OH produced by this reaction - The OH atoms diffuse to the anode through the membrane. Even inside the manifold, which is the supply pipe for the electrolyte, there is ionic conductivity through the electrolyte, so some of the OH atoms diffuse to the anode. - moves to the anode through the manifold. - An ionic current flows in the opposite direction to the flow of ions. This ionic current flowing through the manifold is called leakage current. During electrolysis, the leakage current flows through the manifold, driven by the potential difference between the anodes or cathodes of multiple water electrolysis elements. When leakage current flows, impurity gases are generated, which can deteriorate the gas purity (oxygen concentration in hydrogen, hydrogen concentration in oxygen) and reduce the current efficiency. Furthermore, the deterioration of gas purity due to the generation of impurity gases caused by leakage current is a phenomenon that does not occur only in water electrolysis. For example, in sodium chloride electrolysis, it can lead to a deterioration in gas purity (oxygen concentration in hydrogen, hydrogen concentration in chlorine, oxygen concentration in chlorine). To address these issues, there is a method of lining the gas-liquid box with a highly chemical-resistant electrically insulating material such as fluororesin. For example, Patent Document 1 describes a method of lining the liquid-contacting surface of the gas-liquid box with fluororesin. If this method is used for the manifold, it is possible to prevent the generation of impurity gases due to leakage current, and high electrolysis efficiency can be maintained for a long period of time. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2018-182005 Summary of the Invention [Problem to be solved by the invention]

[0010] However, even with a resin lining such as that described in Patent Document 1, there is a possibility that interfacial peeling may occur due to differences in the linear expansion coefficient with the cell structure or fluid friction at the ends of the lining. If interfacial peeling occurs, the entire cell needs to be replaced, which may result in a higher cost burden. Furthermore, the electrolysis equipment is generally shut down during the cell replacement period, which poses a problem of reduced availability of the electrolytic cell.

[0011] Therefore, an object of the present invention is to suppress the generation of impurity gases due to leakage current, to be able to control output by varying the electrolysis current in response to load fluctuations, to maintain highly efficient and high-purity hydrogen production for a long period of time, to facilitate maintenance of components, and to shorten the period of shutdown of the electrolytic cell. [Means for solving the problem]

[0012] The gist of the present invention is as follows. [1] An internal manifold type bipolar electrode consisting of an anode, a cathode, a partition wall, and an outer frame, and having a manifold. alkaline water an electrolytic element, the anode, the cathode, the partition wall, the outer frame, and the manifold are electrically conductive; At least a portion of the surface of the manifold is covered with a manifold covering member, When the total surface area of ​​all the manifolds is taken as 100%, the proportion of the surface area covered by the manifold covering member (surface coverage rate) is 13 to 100%, The manifold covering member is integrated with a gasket and is detachable. and is made of at least an insulating material , Internal manifold type bipolar type alkaline water Electrolytic element 。 [2 ] At least a part of the surface of the manifold of the cathode terminal element and the anode terminal element is covered with the manifold covering member, [1 ] Internal manifold type bipolar type alkaline water Electrolytic element. [ 3 ] The manifold covering member is made of at least one material selected from the group consisting of rubber materials and polytetrafluoroethylene. [1] or [2] Internal manifold type bipolar type alkaline water Electrolytic element. [ 4 ] The manifold covering member is made of a rubber material, [1] to [ 3

[0033] An internal manifold type bipolar alkaline water Electrolytic element. [ 5 ] A resin spacer is disposed on the outside of the gasket, and the compressive elastic modulus of the resin spacer is greater than the compressive elastic modulus of the gasket, [1] to [ 4

[0033] An internal manifold type bipolar alkaline water Electrolytic element. [ 6 ] [1]~[ 5

[0033] An internal manifold type bipolar alkaline water An internal manifold type bipolar electrolytic cell, characterized in that an electrolytic element and a diaphragm are stacked with the gasket interposed therebetween. alkaline water electrolytic cell. [ 7 ] The manifold is disposed outside the diaphragm, 6 Internal manifold type bipolar type alkaline water electrolytic cell. [ 8 ] An inlet pipe and an outlet pipe are connected to the anode terminal element; 6 ] or [ 7 Internal manifold type bipolar type alkaline water electrolytic cell. [ 9 ] [ 6 ]~[ 8

[0033] An internal manifold type bipolar alkaline water A method for producing hydrogen, characterized by using an electrolytic cell. [ 10 ] The pressure inside the electrolytic cell during electrolysis operation is 3 to 4000 kPa, 9 ] A method for producing hydrogen according to the present invention. [ 11 ] The power source that supplies the electricity is a power source derived from at least one renewable energy output selected from the group consisting of wind power, solar power, hydroelectric power, tidal power, wave power, ocean current power, and geothermal power. 9 ] or [ 10 ] A method for producing hydrogen according to the present invention. [Effects of the Invention]

[0013] According to the present invention, it is possible to suppress the generation of impurity gases due to leakage current, to vary the electrolytic current in response to load fluctuations to control the output, and to maintain highly efficient and high-purity hydrogen production for a long period of time. Furthermore, industrial production is easy, component maintenance is easy, and not only is replacement of the entire electrolytic cell frame unnecessary, but working time can be significantly reduced and electrolysis downtime can be minimized. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing an outline of an example of an electrolysis device according to an embodiment of the present invention; [Figure 2] FIG. 1 is a diagram showing an example of an entire electrolytic cell of an electrolysis device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a plan view showing an example of a bipolar electrolytic element in an electrolytic cell of the internal manifold type electrolytic device of the present embodiment. [Figure 4] (a) is a diagram showing a part of a cross section of an example of a bipolar electrolytic element in an electrolytic cell of the internal manifold type electrolytic device shown in Fig. 3, taken along a plane along line AA. (b) is a diagram showing a state in which a manifold covering member integrated with a gasket and a resin spacer are attached to the bipolar electrolytic element shown in (a). [Figure 5] 10A and 10B are diagrams showing an example of a manifold covering member integrated with a gasket according to the present embodiment. [Figure 6] FIG. 5 is a diagram showing a part of a cross section of the internal manifold type electrolytic cell of the example taken in the same manner as in FIG. 4. [Figure 7] FIG. 5 is a diagram showing a part of a cross section of the internal manifold type electrolytic cells of the examples and comparative examples cut in the same manner as in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the gist of the present invention.

[0016] FIG. 1 shows an outline of an example of the electrolysis device of this embodiment.

[0017] (electrolyzer) 1, the electrolysis device 70 includes a bipolar 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 supply device (not shown) for replenishing water consumed by electrolysis. More specifically, the electrolysis device 70 of this embodiment includes an anode chamber 5a having an anode 2a and a cathode chamber 5c having a cathode 2c, which are separated from each other by a diaphragm 4. The electrolysis device of this embodiment may be a water electrolysis device for electrolyzing water, or in particular, an alkaline water electrolysis device for electrolyzing alkaline water.

[0018] First, among the components of the electrolysis device 70, the bipolar electrolytic cell 50 will be mainly described. The bipolar electrolytic cell of this embodiment may be a bipolar water electrolytic cell for electrolyzing water, or in particular a bipolar alkaline water electrolytic cell for electrolyzing alkaline water.

[0019] (electrolytic cell) There are monopolar and bipolar electrolytic cells, but as the electrolytic cell in the electrolysis device 70 of this embodiment, as shown in FIG. 1 etc., a bipolar electrolytic cell 50, which is industrially preferred, is used. The bipolar system is one method for connecting a large number of cells to a power source, in which multiple bipolar electrolytic elements 60, one side of which is an anode 2a and the other side of which is a cathode 2c, are arranged in the same direction and connected in series, and only both ends are connected to the power source. The bipolar electrolytic cell 50 has the advantage of being able to reduce the current of the power supply, and is capable of producing large amounts of compounds, specified substances, etc. in a short period of time through electrolysis. If the power output is the same, a constant current, high voltage power supply is cheaper and more compact, so from an industrial perspective, a bipolar type is preferable to a monopolar type.

[0020] FIG. 2 shows an example of the entire electrolytic cell of the electrolysis device of this embodiment. FIG. 3 is a plan view showing an example of a bipolar electrolytic element in the electrolytic cell of this embodiment. In the example shown in FIGS. 2 and 3 , the bipolar electrolytic cell 50 is a bipolar electrolytic cell in which a plurality of bipolar electrolytic elements 60, each including an anode 2 a, a cathode 2 c, a partition wall 1 separating the anode 2 a and the cathode 2 c, and an outer frame 3 that frames the partition wall 1, are stacked with a diaphragm 4 sandwiched between them. The electrolytic element of this embodiment includes a single element in which an anode chamber and a cathode chamber are formed with a diaphragm interposed between them. Specifically, the element may be one in which a diaphragm is sandwiched between an anode held by a partition wall and an outer frame and a cathode held by a partition wall and an outer frame, and the diaphragm is fastened with bolts to contain the cathode chamber and the anode chamber. A bipolar electrolytic cell can also be made by stacking such single elements.

[0021] In this embodiment, in particular, the portion between the partition walls 1 between two adjacent bipolar electrolytic elements 60 in the bipolar electrolytic cell 50, and the portion between the partition walls 1 between an adjacent bipolar electrolytic element 60 and a terminal element, are referred to as the electrolytic cell 65. The electrolytic cell 65 includes the partition wall 1, anode chamber 5a, anode 2a, and diaphragm 4 of one element, and the cathode 2c, cathode chamber 5c, and partition wall 1 of the other element.

[0022] ((Bipolar electrolytic element)) An example of the bipolar electrolytic element 60 used in the bipolar electrolytic cell 50 of this embodiment includes a partition wall 1 that separates the anode 2a and the cathode 2c, and an outer frame 3 that borders the partition wall 1. More specifically, the partition wall 1 is conductive, and the outer frame 3 is provided so as to surround the partition wall 1 along the outer edge of the partition wall 1. The bipolar electrolysis element of this embodiment is suitable as a bipolar water electrolysis element for electrolyzing water, and is particularly suitable as a bipolar alkaline water electrolysis element for electrolyzing alkaline water.

[0023] Note that the bipolar electrolytic element 60 of this embodiment may be used so that the given direction D1 along the partition wall 1 is the vertical direction; specifically, when the partition wall 1 has a rectangular shape in a plan view, the given direction D1 along the partition wall 1 may be used so that it is the same direction as the direction of one of two pairs of opposing sides (see FIG. 3). In this specification, the vertical direction is also referred to as the electrolyte passage direction.

[0024] As shown in FIG. 2, the bipolar electrolytic cell 50 of this embodiment is constructed by stacking the required number of bipolar electrolytic elements 60. In the example shown in FIG. 2 , the bipolar electrolytic cell 50 has a fast head 51g, an insulating plate 51i, and an anode terminal element 51a arranged in this order from one end, and further has an anode side gasket portion of the gasket 7, a diaphragm 4, a cathode side gasket portion of the gasket 7, and a bipolar electrolytic element 60 arranged in this order. At this time, the bipolar electrolytic element 60 is arranged so that the cathode 2c faces the anode terminal element 51a. The anode side gasket portion through the bipolar electrolytic element 60 are arranged repeatedly the number of times required for the designed production volume. After the anode side gasket portion through the bipolar electrolytic element 60 are arranged repeatedly the required number of times, the anode side gasket portion, diaphragm 4, and cathode side gasket portion are again arranged in a row, and finally the cathode terminal element 51c, the insulating plate 51i, and the loose head 51g are arranged in this order. The bipolar electrolytic cell 50 is integrated by clamping the entire cell together using a clamping mechanism such as a tie rod system 51r (see FIG. 2) or a hydraulic cylinder system, thereby forming the bipolar electrolytic cell 50. The arrangement of the bipolar electrolytic cell 50 can be arbitrarily selected from either the anode 2a side or the cathode 2c side, and is not limited to the above order.

[0025] 2, in a bipolar electrolytic cell 50, a bipolar electrolytic element 60 is disposed between an anode terminal element 51a and a cathode terminal element 51c. Diaphragms 4 are disposed between the anode terminal element 51a and the bipolar electrolytic element 60, between adjacent bipolar electrolytic elements 60, and between the bipolar electrolytic element 60 and the cathode terminal element 51c.

[0026] In the bipolar electrolytic cell 50 of this embodiment, the partition wall 1, the outer frame 3, and the diaphragm 4 define an electrode chamber 5 through which the electrolyte passes. FIG. 4(a) shows a part of a cross section of the example of the bipolar electrolytic element shown in FIG. 3 taken along the line AA.

[0027] Specifically, the electrode chamber 5 has, at the boundary with the outer frame 3, an electrolyte inlet 5i for introducing the electrolyte into the electrode chamber 5 and an electrolyte outlet 5o for discharging the electrolyte from the electrode chamber 5. More specifically, the anode chamber 5a is provided with an anolyte inlet 5ai for introducing the electrolyte into the anode chamber 5a and an anolyte outlet 5ao for discharging the electrolyte from the anode chamber 5a. Similarly, the cathode chamber 5c is provided with a catholyte inlet 5ci for introducing the electrolyte into the cathode chamber 5c and a catholyte outlet 5co for discharging the electrolyte from the cathode chamber 5c.

[0028] In this embodiment, the anode chamber 5a and the cathode chamber 5c may be provided with internal distributors for uniformly distributing the electrolyte solution over the electrode surfaces inside the bipolar electrolytic cell 50. The electrode chambers 5 may also be provided with baffle plates that have the function of restricting the flow of the solution inside the bipolar electrolytic cell 50. Furthermore, the anode chamber 5a and the cathode chamber 5c may be provided with protrusions for creating Karman vortices in order to uniformize the concentration and temperature of the electrolyte solution inside the bipolar electrolytic cell 50 and to promote degassing of gases adhering to the electrode 2 and the diaphragm 4.

[0029] A manifold 20, which is a pipe for distributing or collecting gas and electrolyte, is attached to the bipolar electrolytic cell 50. In detail, the manifold 20 preferably comprises, and consists of, an inlet header 20i for introducing electrolyte into the electrode chamber 5 and an outlet header 20o for discharging gas and electrolyte from the electrode chamber 5.

[0030] Typical manifold arrangements include an internal manifold type in which the collecting pipe (hereinafter referred to as the header) is not independent of the bipolar electrolytic cell but is provided inside the electrolytic cell, and an external manifold type in which the header is independent of the bipolar electrolytic cell (provided outside the electrolytic cell). In the bipolar electrolytic cell 50 of this embodiment, an internal manifold type is used in which both the inlet header section 20i and the outlet header section 20o are provided inside the bipolar electrolytic cell 50. Generally, the anode distribution pipe is called the anode inlet header 20ai, the cathode distribution pipe is called the cathode inlet header 20ci, the anode collection pipe is called the anode outlet header 20ao, and the cathode collection pipe is called the cathode outlet header 20co.

[0031] FIG. 3 shows a plan view of an example of an internal manifold type bipolar electrolytic element according to this embodiment. FIG. 4(a) shows a part of a cross section of an example of the internal manifold type bipolar electrolytic element shown in FIG. 3 taken along the line AA.

[0032] In the example shown in FIGS. 3 and 4(a), the bipolar electrolytic element 60 is used so that a given direction D1 along the partition wall 1 is the vertical direction, and an anode inlet header 20ai for supplying the electrolyte to the anode chamber 5a and a cathode inlet header 20ci for supplying the electrolyte to the cathode chamber 5c are provided below the outer frame 3 at the edge of the partition wall 1, and an anode outlet header 20ao for discharging the electrolyte from the anode chamber 5a and a cathode outlet header 20co for discharging the electrolyte from the cathode chamber 5c are provided above the outer frame 3 at the edge of the partition wall 1.

[0033] In the present embodiment, from the viewpoint of electrolysis efficiency, the inlet header section 20i and the outlet header section 20o are preferably provided at positions separated from each other, and are preferably provided so as to face each other across the center of the electrode chamber 5. When the shape of the partition wall 1 in a plan view is rectangular as shown in FIG. 3, the inlet header section 20i and the outlet header section 20o are preferably provided symmetrically with respect to the center of the rectangle.

[0034] Furthermore, both the inlet header 20i and the outlet header 20o are preferably provided outside the diaphragm 4 (any location around the diaphragm 4). By providing the manifold 20 outside the diaphragm 4 (for example, outside the electrode chamber 5 as shown in FIG. 3 ) rather than providing it inside the diaphragm 4 (for example, by arranging the inlet header 20i and the outlet header 20o inside the diaphragm 4 so that they penetrate the diaphragm 4), there is no risk of damaging the diaphragm 4.

[0035] Typically, as shown in FIG. 3 , one anode inlet header section 20ai, one cathode inlet header section 20ci, one anode outlet header section 20ao, and one cathode outlet header section 20co are provided in each electrode chamber 5, but this is not limited to this in the present embodiment, and multiple sections may be provided in each electrode chamber 5.

[0036] 3 and 4(a), the partition wall 1, which is rectangular in plan view, and the diaphragm 4, which is also rectangular in plan view, are arranged parallel to each other, and the inner surface of the rectangular outer frame provided at the edge of the partition wall 1, facing the partition wall 1, is perpendicular to the partition wall 1, so that the shape of the electrode chamber 5 is rectangular. However, in the present invention, the shape of the electrode chamber 5 is not limited to the rectangular parallelepiped shown in the example and may be modified as appropriate depending on the planar shapes of the partition wall 1 and the diaphragm 4, the angle between the inner surface of the outer frame 3 facing the partition wall 1, and the partition wall 1, etc., and any shape is acceptable as long as the effects of the present invention are obtained.

[0037] In this embodiment, the extension direction of the manifold 20 is not particularly limited, but from the viewpoint of making it easier to obtain the effects of the present invention, it is preferable that there be a header portion extending in a direction perpendicular to the partition wall 1, and it is more preferable that all of the header portions extend in a direction perpendicular to the partition wall 1, as in the example shown in Figures 3 and 4(a). In this specification, extending in a direction perpendicular to the partition walls 1 does not mean extending in a direction perpendicular to the partition walls 1 in the strict sense, but also means extending in a direction inclined, for example, at an angle of 45° or less relative to the direction perpendicular to the partition walls 1 when viewed in a direction along the partition walls 1. The inclination angle is preferably 30° or less, and more preferably 15° or less.

[0038] In this embodiment, at least a portion of the surface of the manifold 20 is covered with a manifold covering member 30 integrated with the gasket 7 in order to prevent the generation of impurity gases due to leakage current. Here, the integration of the manifold covering member 30 and the gasket 7 means that the sealing function of the gasket 7 and the function of the manifold covering member 30 to cover the surface of the manifold 20 are provided in one member. Furthermore, covering with manifold covering member 30 refers to covering at least a portion of the surface (liquid-contacting surface) of manifold 20 with the member. By covering at least a portion of the surface of manifold 20 with manifold covering member 30, it is possible to prevent the generation of impurity gases due to leakage current on the surface of manifold 20. Manifold covering member 30 is preferably made of at least an insulating material. In order to further improve the sealing performance between the elements, a resin spacer 40 may be disposed on the outside of the gasket 7 so as to surround the outer periphery of the gasket 7 . 4(b) shows a state in which a manifold covering member 30 integrated with a gasket 7 is attached to the example of the bipolar electrolytic element 60 shown in FIG. 4(a). Although not shown, in reality, there are thin tubes that lead from the anode outlet header portion 20ao to the anode chamber 5a, and the openings of the thin tubes on the surface of the anode outlet header portion 20ao are not covered with the manifold covering member 30.

[0039] The bipolar electrolytic cell 50 of the electrolysis device 70 of this embodiment may be provided with a plurality of rectifying plates 6 (anode rectifying plate 6a, cathode rectifying plate 6c) arranged parallel to a given direction D1 along the partition wall 1 in order to reduce convection that occurs in the electrolytic chamber 5 due to turbulence in the gas-liquid flow therein and suppress a local increase in the temperature of the electrolytic solution (see FIGS. 3 and 4). The number, length, angle between the rectifying plates 6 and the partition wall 1, and the constant interval (pitch) in the direction perpendicular to the given direction D1 along the partition wall 1 may be determined as appropriate and do not have to be constant, as long as the effects of the present invention are obtained. Furthermore, the rectifying plates 6 may have through holes, and the number of through holes and the constant interval (pitch) in the given direction D1 along the partition wall 1 may be determined as appropriate and do not have to be constant, as long as the effects of the present invention are obtained. Furthermore, protrusions and / or depressions may be provided instead of the straightening plate 6. The three-dimensional shape of the protrusions and / or depressions is not particularly limited, and may be any geometric shape, such as a wave shape, hemisphere, sphere, oval sphere, cylinder, cone, or frustum. The protrusions and / or depressions may be arranged at a certain interval. The protrusions and / or depressions may be arranged in any arrangement, such as a 60° staggered arrangement, a 45° staggered arrangement, or a parallel arrangement.

[0040] The bipolar electrolytic cell 50 of the electrolysis device 70 of this embodiment is not particularly limited, and preferably has 50 to 500 bipolar electrolytic elements 60, more preferably has 70 to 300 bipolar electrolytic elements 60, and particularly preferably has 100 to 200 bipolar electrolytic elements 60. As the number of bipolar electrolytic elements 60 (number of pairs) increases, the effect of leakage current on gas purity is mitigated, but it becomes difficult to uniformly distribute the electrolyte to each electrolytic cell 65. If the number is below the lower limit or above the upper limit, it becomes difficult to simultaneously achieve the effects of reducing self-discharge that occurs when power supply is stopped, thereby enabling stabilization of the electrical control system, and highly efficient power storage, specifically, the effects of reducing pump power and leakage current. Furthermore, if the number of pairs is too large, it may become difficult to manufacture the bipolar electrolytic cell 50, and if a large number of bipolar electrolytic elements 60 with poor manufacturing accuracy are stacked, the seal surface pressure is likely to become uneven, making it more likely that electrolyte leakage or gas leakage will occur.

[0041] The components of the bipolar electrolytic cell 50 of the electrolysis device 70 of this embodiment will be described in detail below. In addition, preferred embodiments for enhancing the effects of the present invention will be described in detail below.

[0042] -Bulkhead- The shape of the partition wall 1 may be a plate shape having a predetermined thickness, but is not particularly limited. The shape of the partition wall 1 in plan view is not particularly limited, and may be rectangular (square, oblong, etc.) or circular (circle, ellipse, etc.), and the rectangle may have rounded corners.

[0043] In an embodiment, the partition wall 1 and the outer frame 3 may be joined by welding or another method. For example, the partition wall 1 may be provided with a flange portion protruding in a direction perpendicular to the plane of the partition wall 1 (an anode flange portion protruding toward the anode 2a side, and a cathode flange portion protruding toward the cathode 2c side), and the flange portions may be formed as part of the outer frame 3.

[0044] In addition, the partition wall 1 may usually be used so that a given direction D1 along the partition wall 1 is the vertical direction. Specifically, when the partition wall 1 has a rectangular shape in a plan view as shown in Figure 3, the partition wall 1 may be used so that the given direction D1 along the partition wall 1 is the same direction as the direction of one of two pairs of opposing sides.

[0045] The material of the partition wall 1 is preferably an electrically conductive material from the viewpoint of realizing a uniform supply of power, and is preferably nickel, a nickel alloy, mild steel, or a nickel alloy plated with nickel from the viewpoint of alkali resistance and heat resistance.

[0046] -electrode- In hydrogen production by electrolysis, reducing energy consumption, specifically the electrolysis voltage, is a major challenge. Because this electrolysis voltage is highly dependent on the electrodes 2, the performance of both electrodes 2 is important.

[0047] The electrolysis voltage can be divided into the theoretically required voltage for water electrolysis, the overvoltage for the anode reaction (oxygen generation), the overvoltage for the cathode reaction (hydrogen generation), and the voltage due to the distance between the anode 2a and cathode 2c. Here, overvoltage refers to the voltage that must be applied in excess of the theoretical decomposition potential when a certain current is passed, and its value depends on the current value. When passing the same current, power consumption can be reduced by using an electrode 2 with a lower overvoltage.

[0048] In order to achieve a low overvoltage, the electrode 2 must have high electrical conductivity, high oxygen generating capacity (or hydrogen generating capacity), and high wettability of the surface of the electrode 2 with the electrolyte.

[0049] In addition to having a low overvoltage, the electrode 2 for electrolysis is less susceptible to corrosion of the substrate and catalytic layer of the electrode 2, detachment of the catalytic layer, dissolution in the electrolyte, and adhesion of inclusions to the diaphragm 4, even when an unstable current such as that from renewable energy is used.

[0050] The electrode 2 is preferably porous in order to increase the surface area available for electrolysis and to efficiently remove gas generated by electrolysis from the surface of the electrode 2. In particular, in the case of an electrolytic cell with a zero gap structure Z in which the diaphragm 4 is in contact with the anode 2a and the cathode 2c, it is necessary to degas the gas generated from the back side of the surface of the electrode 2 that is in contact with the diaphragm 4, and therefore it is preferable that the surface of the electrode 2 opposite to the surface that is in contact with the diaphragm 4 is perforated. Examples of the porous body include plain woven mesh, punched metal, expanded metal, and metal foam.

[0051] The electrode 2 may be the substrate itself, or may have a highly reactive catalyst layer on the surface of the substrate, but is preferably one having a highly reactive catalyst layer on the surface of the substrate.

[0052] The material of the substrate is not particularly limited, but mild steel, stainless steel, nickel, and nickel-based alloys are preferred in terms of resistance to the usage environment.

[0053] The catalytic layer of the anode 2a preferably has high oxygen generating capacity, and nickel, cobalt, iron, platinum group elements, or the like can be used. To achieve the desired activity and durability, the catalytic layer can be formed as a single metal, a compound such as an oxide, a composite oxide or alloy made of multiple metal elements, or a mixture thereof. An organic substance such as a polymer may be included to improve durability and adhesion to the substrate.

[0054] The catalytic layer of the cathode 2c preferably has high hydrogen generation capacity, and nickel, cobalt, iron, platinum group elements, or the like can be used. To achieve the desired activity and durability, the catalytic layer can be formed as a single metal, a compound such as an oxide, a composite oxide or alloy made of multiple metal elements, or a mixture thereof. An organic substance such as a polymer material may be included to improve durability and adhesion to the substrate.

[0055] Examples of methods for forming a catalyst layer on a substrate include plating methods, thermal spraying methods such as plasma spraying, thermal decomposition methods in which a precursor layer solution is applied to a substrate and then heat is applied, methods in which a catalyst substance is mixed with a binder component and then fixed to the substrate, and vacuum film formation methods such as sputtering.

[0056] -Outer frame- The shape of the outer frame 3 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 over the entire extent of the partition wall 1. The shape of the outer frame 3 is not particularly limited and may be determined appropriately in accordance with the shape of the partition wall 1 in a plan view.

[0057] The material of the outer frame 3 is preferably a conductive material, and from the viewpoint of alkali resistance and heat resistance, nickel, nickel alloy, mild steel, or nickel alloy plated with nickel is preferred.

[0058] -diaphragm- The diaphragm used in the bipolar electrolytic cell 50 of the electrolysis device 70 is an ion-permeable diaphragm 4 that separates the generated hydrogen gas and oxygen gas while conducting ions. Examples of this ion-permeable diaphragm 4 include an ion exchange membrane having ion exchange capacity and a porous membrane that is permeable to the electrolytic solution. The ion-permeable diaphragm 4 preferably has low gas permeability, high ionic conductivity, low electronic conductivity, and high strength.

[0059] --Porous membrane-- The porous membrane has a structure with multiple fine through-holes that allow the electrolyte to pass through the diaphragm 4. Ion conduction occurs when the electrolyte permeates the porous membrane, so control of the porous structure, such as pore size, porosity, and hydrophilicity, is extremely important. On the other hand, it is also required that not only the electrolyte but also the generated gas does not pass through, i.e., the membrane has gas barrier properties. Control of the porous structure is also important from this perspective.

[0060] The porous membrane has a plurality of fine through-holes, and examples thereof include polymer porous membranes, inorganic porous membranes, woven fabrics, nonwoven fabrics, etc. These can be produced by known techniques. Examples of methods for producing porous polymer membranes include a phase inversion method (microphase separation method), an extraction method, a stretching method, and a wet gel stretching method.

[0061] The porous membrane preferably contains a polymeric material and hydrophilic inorganic particles, which can impart hydrophilic properties to the porous membrane.

[0062] The thickness of the porous membrane is not particularly limited, but is preferably 200 μm or more and 700 μm or less. If the thickness of the porous membrane is 200 μm or more, better gas barrier properties can be obtained, and the strength of the porous membrane against impacts can be further improved. From this viewpoint, the lower limit of the thickness of the porous membrane 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, ion permeability is less likely to be hindered by the resistance of the electrolyte contained in the pores during operation, and better ion permeability can be maintained. From this viewpoint, the upper limit of the thickness of the porous membrane is more preferably 600 μm or less, even more preferably 550 μm or less, and even more preferably 500 μm or less. In particular, when the polymer material contains at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone, this effect is further improved.

[0063] --Ion exchange membrane-- 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 are preferably used. Fluorine-containing ion exchange membranes are particularly preferred because of their excellent heat resistance and chemical resistance.

[0064] Examples of fluorine-containing ion exchange membranes include those that have the function of selectively permeating ions generated during electrolysis and contain a fluorine-containing polymer having an ion exchange group. The fluorine-containing polymer having an ion exchange group as used herein refers to a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor that can be converted to an ion exchange group by hydrolysis. Examples include polymers that have a fluorinated hydrocarbon main chain, have functional groups that can be converted to ion exchange groups by hydrolysis or the like as pendant side chains, and are melt-processable.

[0065] Examples of the ion exchange group of the ion exchange membrane include cation exchange groups such as sulfonic acid groups, carboxylic acid groups and phosphate groups, and anion exchange groups such as quaternary ammonium groups.

[0066] By adjusting the equivalent mass (EW) of the ion exchange groups, ion exchange membranes can be endowed with excellent ion exchange capacity and hydrophilicity. Furthermore, by controlling the membrane to have many smaller clusters (microscopic areas where ion exchange groups coordinate and / or adsorb water molecules), alkali resistance and ion selective permeability tend to improve. The equivalent weight EW can be measured by salt-substituting the ion-exchange membrane and back-titrating the resulting solution with an alkaline or acid solution. The equivalent weight EW can be adjusted by the copolymerization ratio of the raw material monomers, the selection of the monomer species, etc. The equivalent mass EW of the ion exchange membrane is preferably 300 or more from the viewpoint of hydrophilicity and water resistance of the membrane, and is preferably 1300 or less from the viewpoint of hydrophilicity and ion exchange capacity.

[0067] The thickness of the ion exchange membrane is not particularly limited, but is preferably in the range of 5 to 500 μm from the viewpoint of ion permeability and strength.

[0068] The ion exchange membrane may be subjected to a surface treatment for the purpose of improving the hydrophilicity of the surface, such as by coating with hydrophilic inorganic particles such as zirconium oxide or by providing the surface with fine irregularities.

[0069] 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 examples thereof include general nonwoven fabrics, woven fabrics, and porous membranes made of various materials. In this case, the porous membrane is not particularly limited, but is preferably a polytetrafluoroethylene (PTFE)-based membrane that has been stretched to make it porous.

[0070] ((Zero gap structure)) In a bipolar electrolytic element 60 in a zero-gap cell in which the diaphragm 4 is in contact with the anode 2a and the cathode 2c, a spring, which is an elastic body, is disposed between the electrode 2 and the partition wall 1 as a means for reducing the interelectrode distance, and the electrode 2 is preferably supported by this spring. For example, in a 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 a second example, a spring may be attached to an electrode rib attached to the partition wall 1, and the electrode 2 may be attached to this spring. Note that when such a configuration using an elastic body is adopted, the strength, number, shape, and the like of the spring must be appropriately adjusted as necessary to prevent uneven contact pressure between the electrode 2 and the diaphragm 4.

[0071] Furthermore, by increasing the rigidity of the other electrode 2 that is paired with the electrode 2 supported via the elastic body, the structure is such that deformation is minimal even when pressed. On the other hand, the electrode 2 supported via the elastic body has a flexible structure that deforms when the diaphragm 4 is pressed against it, so that unevenness due to manufacturing tolerances of the electrolytic cell 65 and deformation of the electrode 2 can be absorbed, thereby maintaining the zero gap.

[0072] In the bipolar electrolytic cell 50 of the electrolysis system 70 of the present embodiment, a conductive elastic body 2e and a current collector 2r are provided between the cathode 2c or the anode 2a and the partition wall 1 such that the conductive elastic body 2e is sandwiched between the cathode 2c or the anode 2a and the current collector 2r.

[0073] -Current collector- The current collector 2r transmits electricity to the conductive elastic body 2e and the electrode 2 stacked thereon, supports the loads received from them, and allows gas generated from the electrode 2 to pass through to the partition wall 1 side without hindrance. Therefore, the shape of the current collector 2r is preferably an expanded metal, a punched perforated plate, or the like. In this case, the aperture ratio of the current collector 2r is preferably within a range that allows hydrogen gas generated from the electrode 2 to be released to the partition wall 1 side without hindrance. However, if the aperture ratio is too large, problems such as a decrease in strength or a decrease in conductivity to the conductive elastic body 2e may occur, and if the aperture ratio is too small, gas escape may be poor.

[0074] The material of the current collector 2r can be nickel, nickel alloy, stainless steel, mild steel, etc., from the viewpoint of conductivity and alkali resistance, but nickel, mild steel, or stainless steel-nickel alloy plated with nickel is preferred from the viewpoint of corrosion resistance.

[0075] -Conductive elastic body- The conductive elastic body 2e is located between the current collector 2r and the electrode 2 and is in contact with the current collector 2r and the electrode 2. It is essential that the conductive elastic body 2e transmits electricity to the electrode 2 and does not inhibit the diffusion of gas generated from the electrode 2. This is because inhibiting gas diffusion increases electrical resistance and reduces the area of ​​the electrode 2 used for electrolysis, thereby reducing the efficiency of electrolysis. The most important role of the conductive elastic body 2e is to evenly apply an appropriate amount of pressure to the electrode 2 without damaging the diaphragm 4, thereby tightly adhering the diaphragm 4 to the electrode 2.

[0076] As the conductive elastic body 2e, a commonly known material can be used, and for example, a cushion mat made by corrugating woven nickel wire with a wire diameter of about 0.05 to 0.5 mm is preferred because it is easy to maintain a zero-gap structure.

[0077] -Electrode chamber- In the bipolar electrolytic cell 50, the partition wall 1, the outer frame 3, and the diaphragm 4 define an electrode chamber 5 through which the electrolyte passes.

[0078] In the bipolar electrolytic cell 50 of this embodiment, the manifold is arranged as an internal manifold, and the space occupied by the anode 2 a and the cathode 2 c themselves may also be the space inside the electrode chamber 5 .

[0079] -Rectifier plate- In the bipolar electrolytic cell 50 of the electrolysis device 70, it is preferable that the rectifying plates 6 (anode rectifying plate 6a, cathode rectifying plate 6c) are attached to the partition wall 1, and the rectifying plates 6 are physically connected to the electrodes 2. According to this configuration, the rectifying plates 6 serve as supports for the electrodes 2, making it easy to maintain the zero-gap structure Z. Here, the electrode 2 may be provided on the rectifying plate 6, or the current collector 2r, the conductive elastic body 2e, and the electrode 2 may be provided on the rectifying plate 6 in this order. 4(a), a structure is adopted in the cathode chamber 5c in which a current rectifying plate 6c, a current collector 2r, a conductive elastic body 2e, and an electrode 2c are stacked in this order, and a structure is adopted in the anode chamber 5a in which a current rectifying plate 6a and an electrode 2a are stacked in this order. The present invention is not limited to the above structures, and a "current rectifying plate 6a, a current collector 2r, a conductive elastic body 2e, and an electrode 2a" structure may also be adopted in the anode chamber 5a.

[0080] The current rectifying plates 6 (anode current rectifying plates 6a, cathode current rectifying plates 6c) preferably have a role not only to support the anode 2a or cathode 2c but also to transmit current from the partition wall 1 to the anode 2a or cathode 2c.

[0081] Furthermore, it is preferable that at least a part of the rectifying plate 6 is conductive, and it is more preferable that the entire rectifying plate 6 is conductive. With this configuration, it is possible to suppress an increase in cell voltage due to electrode deflection.

[0082] Conductive metals are generally used as the material for the rectifying plate 6. For example, nickel-plated mild steel, stainless steel, nickel, etc. can be used.

[0083] The distance between adjacent anode rectifying plates 6a or the distance between adjacent cathode rectifying plates 6c is determined taking into consideration the electrolysis pressure and the pressure difference between the anode chamber 5a and the cathode chamber 5c.

[0084] -Manifold- The bipolar electrolytic cell 50 has a cathode chamber 5c and an anode chamber 5a for each electrolytic cell 65. In order to continuously perform the electrolytic reaction in the bipolar electrolytic cell 50, it is necessary to continuously supply an electrolyte containing a sufficient amount of raw materials to be consumed by electrolysis to the cathode chamber 5c and the anode chamber 5a of each electrolytic cell 65.

[0085] The electrolytic cells 65 are connected to an electrolytic solution supply / discharge pipe called a manifold 20 that is common to the multiple electrolytic cells 65. The manifold 20 has an inlet header 20i and an outlet header 20o, and preferably comprises an anode inlet header 20ai, a cathode inlet header 20ci, an anode outlet header 20ao, and a cathode outlet header 20co.

[0086] The material of the manifold 20 is not particularly limited, but it is necessary to adopt a material that can sufficiently withstand the corrosiveness of the electrolyte used and the operating conditions such as pressure and temperature. Examples of materials for the manifold 20 include metals such as iron, nickel, and cobalt.

[0087] The manifold 20 of the bipolar electrolytic cell 50 is typically arranged in an internal manifold type or an external manifold type, but in this embodiment, the internal manifold type is used.

[0088] --Internal manifold type-- The internal manifold type refers to a type in which the electrolytic cell and the manifold are not independent, but the manifold is provided inside the bipolar electrolytic cell. The internal manifold type does not require the use of nozzles as in the external manifold type, and therefore does not have the problem of nozzle interference, and the electrolytic cell does not need to be enlarged to solve this problem, allowing the electrolytic cell to be made thinner. Furthermore, since the internal manifold type has higher pressure resistance than the external manifold type, it can also be used for pressurized operation.

[0089] In the internal manifold type bipolar electrolytic cell 50 of the present embodiment, specifically, the anode inlet header section 20ai and the cathode inlet header section 20ci are provided inside and / or outside the electrode chamber 5 (partition wall 1), and the anode outlet header section 20ao and the cathode outlet header section 20co are provided inside and / or outside the electrode chamber 5 (partition wall 1). Among these arrangements, it is preferable to arrange all of the header sections outside the diaphragm 4 (for example, outside the electrode chamber 5 as shown in FIG. 3 ) rather than providing them inside the diaphragm 4 (for example, arranging the inlet header section 20i and the outlet header section 20o inside the diaphragm 4 so as to penetrate the diaphragm 4).

[0090] Furthermore, the extension direction of each header portion is not particularly limited. However, from the viewpoint of making the effects of the present invention easier to obtain, it is preferable that some of the anode inlet header portion 20ai, cathode inlet header portion 20ci, anode outlet header portion 20ao, and cathode outlet header portion 20co extend in a direction perpendicular to the partition wall 1, and more preferably all of them extend in a direction perpendicular to the partition wall 1 as in the examples shown in FIG. 3 and FIG. 4(a).

[0091] The shape of the cross section of the flow path of the header section is not particularly limited, and examples thereof include a round, rectangular, elliptical, and the like. The cross-sectional area of ​​the flow path in the header section can be freely designed taking into consideration pressure loss and flow path blockage.

[0092] When stacking the elements, a gasket 7 is placed around each header to improve the sealing between the elements. Furthermore, in the internal manifold type bipolar electrolytic cell 50, each element is structurally significantly affected by leakage current. In this embodiment, in order to prevent the generation of impurity gases due to leakage current, at least a portion of the surface (liquid-contacting surface) of the manifold 20 is protected by a manifold covering member 30 integrated with a gasket 7. The surface protection of the manifold 20 can be more effective by providing protection to both the inlet header section 20i and the outlet header section 20o.

[0093] The internal manifold type bipolar electrolytic cell 50 may have a gas-liquid separation box therein that separates the gas generated by electrolysis from the electrolytic solution. The installation position of the gas-liquid separation box is not particularly limited, and it may be between the anode chamber 5a and the anode outlet header portion 20ao, or between the cathode chamber 5c and the cathode outlet header portion 20co.

[0094] The surface of the gas-liquid separation box may be covered with a coating material that is sufficiently resistant to the corrosiveness of the electrolyte and to operating conditions such as pressure and temperature. The coating material may be insulating in order to increase the electrical resistance of the leakage current circuit inside the electrolytic cell. Examples of coating materials include ethylene-propylene-diene rubber (EPDM), PTFE, ETFE, PFA, polyvinyl chloride, and polyethylene.

[0095] -gasket- In the bipolar electrolytic cell 50, a gasket 7 having a diaphragm 4 is sandwiched between outer frames 3 that frame the partition walls 1. The gaskets 7 are used to seal between each element and the diaphragm 4 and between each element against the electrolytic solution and the generated gas, and can prevent leakage of the electrolytic solution or the generated gas to the outside of the bipolar electrolytic cell 50 and mixing of gases between the two electrode chambers.

[0096] The gasket 7 generally has a rectangular or annular structure with the electrode surface hollowed out to match the surface that contacts the element frame. The diaphragm 4 can be stacked between elements by sandwiching it between two such gaskets. Furthermore, the gasket 7 preferably has a slit that can accommodate the diaphragm 4 so that it can hold the diaphragm 4, and also has openings that allow the accommodated diaphragm 4 to be exposed on both surfaces of the gasket 7. This allows the gasket 7 to accommodate the edge of the diaphragm 4 within the slit, thereby covering the end faces of the edge of the diaphragm 4. This more reliably prevents electrolyte and gas from leaking from the end faces of the diaphragm 4.

[0097] The material of the gasket 7 is not particularly limited, and known insulating rubber materials, resin materials, etc. can be selected. Examples of rubber and resin materials that can be used include natural rubber (NR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), silicone rubber (SR), ethylene-propylene rubber (EPT), ethylene-propylene-diene rubber (EPDM), fluororubber (FR), isobutylene-isoprene rubber (IIR), urethane rubber (UR), and chlorosulfonated polyethylene rubber (CSM). Fluororesin materials include PTFE, PFA, ETFE, and chlorotrifluoroethylene-ethylene copolymer (ECTFE). Resin materials include polyphenylene sulfide (PPS), polyethylene, polyimide, and polyacetal. Among these, EPDM and FR are particularly suitable in terms of elastic modulus and alkali resistance. These materials may be used alone or in combination.

[0098] A reinforcing material may be embedded in the gasket 7. This makes it possible to prevent the gasket 7 from being crushed when it is sandwiched and pressed between frames during stacking, and makes it easier to prevent damage. Such reinforcing materials can be made of known metal materials and their oxides, resin materials, carbon materials, etc., and specific examples include metals such as nickel and stainless steel, metal oxides such as alumina and zirconium oxide, resins such as nylon, polypropylene, PVDF, PTFE, and PPS, and carbon materials such as carbon particles and carbon fibers.

[0099] The size of the gasket 7 is not particularly limited and may be designed to match the dimensions of the electrode chamber 5 and the diaphragm 4, but the width is preferably 10 to 40 mm. Furthermore, when the gasket 7 has a slit portion, the size of the slit portion is preferably set so that the inner dimensions of the slit are 0.5 to 5 mm larger in length and width than the size of the membrane.

[0100] The thickness of the gasket 7 is not particularly limited and is designed depending on the material, elastic modulus and cell area of ​​the gasket 7, but is preferably 1.0 to 10 mm, more preferably 3.0 to 10 mm. Furthermore, when the gasket 7 has a slit portion, the opening width of the slit portion may be 0.5 to 1.0 times the thickness of the diaphragm 4.

[0101] The elastic modulus of the gasket 7 is not particularly limited and is designed depending on the material and cell area of ​​the electrode 2. A preferred range of the elastic modulus is a tensile stress at 100% deformation of 0.20 to 20 MPa, and from the viewpoint of sealing properties and cell strength when stacked, a range of 1.0 to 10 MPa is more preferred. The tensile stress can be measured in accordance with JIS K6251. For example, an Autograph AG manufactured by Shimadzu Corporation may be used.

[0102] In particular, it is preferable that the gasket 7 has a thickness of 3.0 to 10 mm and a tensile stress of 1.0 to 10 MPa at 100% deformation from the viewpoint of suppressing an increase in cell voltage due to electrode deflection, and from the viewpoint of sealing properties and cell strength when stacked.

[0103] In the electrolysis device 70, it is preferable to cover the surface of the gasket 7 with an insulating resin sheet (for example, a fluororesin such as polytetrafluoroethylene). This provides mutual insulation between the elements, thereby preventing the charge accumulated in each element during the energization step (the step in which electrolysis of the electrolyte solution is performed) from affecting other elements during the stop step (the step in which electrolysis of the electrolyte solution is stopped).

[0104] Each element may have multiple gaskets depending on the object to be sealed. For example, the gasket 7 may be an electrode chamber gasket that seals the electrode chamber 5 and a manifold gasket that seals the manifold 20. The manifold covering member may be integrated with any of the gaskets. All of the manifold covering members may be integrated with the same gasket, or each manifold covering member may be integrated with a different gasket. From the viewpoint of ease of maintenance, it is preferable to use as few gaskets as possible.

[0105] Furthermore, a resin spacer 40 may be disposed on the outside of the gasket 7 so as to surround the outer periphery of the gasket 7. By using the resin spacer 40, damage to the diaphragm due to creep or extrusion of the gasket 7 can be prevented.

[0106] FIG. 4( b ) shows an example of a state in which the gasket 7 and the resin spacer 40 are attached to the bipolar electrolytic element 60 .

[0107] The materials of the electrode chamber gasket, manifold gasket, and resin spacer 40 can be selected appropriately depending on the object to be sealed.

[0108] The resin spacer 40 preferably has a greater compressive elastic modulus than the gasket 7. If the resin spacer 40 has a greater compressive elastic modulus than the gasket 7, the distance between the elements is likely to be kept constant even if creep occurs in the gasket 7 during long-term electrolysis, and the balance of the sealing surface pressure between the gasket 7 and the resin spacer 40 is likely to be maintained. The compressive modulus can be measured in accordance with JIS K 6254. For example, an autograph manufactured by Shimadzu Corporation may be used.

[0109] -Manifold covering material- In the bipolar electrolytic cell 50 of this embodiment, in order to prevent the generation of impurity gases due to leakage current, at least a portion of the surface (liquid-contacting surface) of the manifold 20 is covered and protected by a manifold covering member 30 integrated with a gasket 7. In this specification, "at least a part of the surface of the manifold is covered" means that at least a part of the surface of the manifold is covered except for the opening of the capillary leading to the electrode chamber.

[0110] Because the manifold covering member 30 is integrated with the gasket 7, gaps are less likely to form between the manifold covering member 30 and the gasket 7 or between the manifold 20 and the manifold 20, and deterioration of gas purity (generation of impurity gas due to leakage current) is less likely to occur, compared to when the manifold covering member 30 is independent. Furthermore, since the number of parts is reduced when the manifold covering member 30 is integrated with the gasket 7, assembly and maintenance are easier, and the working time (period during which electrolysis is stopped) can be shortened. Furthermore, the manifold covering member 30 is preferably detachable from the manifold 20. That is, when the gasket 7 is detached from the bipolar electrolytic cell 50, the manifold covering member 30 is preferably detachable together with the gasket 7 while remaining integrated. Being detachable makes it possible to easily replace only the manifold covering member 30 during maintenance. In contrast, for example, if a non-detachable resin lining is applied to the manifold 20, when a defect such as interfacial peeling occurs, the entire cell must be replaced, which can result in a significant maintenance burden. Generally, the electrolysis equipment is shut down during cell replacement, and improving maintainability can solve the problem of reduced availability of the electrolytic cell.

[0111] In the manifold 20 of the present embodiment, it is sufficient that at least a portion of the surface of any one of the header portions, anode inlet header portion 20ai, cathode inlet header portion 20ci, anode outlet header portion 20ao, and cathode outlet header portion 20co, is covered with manifold covering member 30; from the viewpoint of more efficiently preventing the generation of impurity gas due to leakage current, it is preferable that at least a portion of the surface of anode inlet header portion 20ai and anode outlet header portion 20ao be covered with manifold covering member 30, and it is further preferable that at least a portion of the surface of all of these header portions be covered with manifold covering member 30.

[0112] Fig. 5 shows an example of manifold covering member 30 integrated with gasket 7 of the present embodiment. Fig. 5 shows an example in which gasket 7 is integrated with each of an anode inlet manifold covering member 30ai that covers anode inlet header portion 20ai of the manifold, an anode outlet manifold covering member 30ao that covers anode outlet header portion 20ao, a cathode inlet manifold covering member 30ci that covers cathode inlet header portion 20ci of the manifold, and a cathode outlet manifold covering member 30co that covers cathode outlet header portion 20co. Note that manifold covering member 30 similarly has openings in portions that correspond to the openings of the capillaries on the surface of manifold 20 that lead to the electrode chambers, but these are not shown in Fig. 5.

[0113] The manifold covering member 30 integrated with the gasket 7 may be attached to each element so as to cover at least a portion of the surface of the manifold 20 (header portion) of that element. That is, the bipolar electrolytic cell 50 of this embodiment is composed of at least one type of element selected from the group consisting of elements in which the entire surface of the manifold 20 is covered with the manifold covering member 30, elements in which a portion of the surface of the manifold 20 is covered with the manifold covering member 30 and the surface (metal surface, etc.) of the manifold 20 is exposed in the remaining portion, and elements in which the surface of the manifold 20 is not covered at all with the manifold covering member 30 and the entire surface (metal surface, etc.) of the manifold 20 is exposed. The more manifold covering members 30 used, the more effective it is at suppressing the generation of impurity gases due to leakage current.

[0114] In the bipolar electrolytic cell 50 of this embodiment, from the viewpoint of efficiently preventing the generation of impurity gases due to leak current, when the total surface area of ​​all manifolds 20 provided in the bipolar electrolytic cell 50 is taken as 100%, the proportion of the surface area covered by the manifold covering member 30 (surface coverage) is preferably 13 to 100%, more preferably 25 to 100%, and even more preferably 50 to 100%.

[0115] In particular, the proportion of the surface area covered by the manifold covering member 30 (surface coverage rate) to the surface area of ​​the manifold 20 provided in each terminal element (cathode terminal element 51c or anode terminal element 51a) is preferably 13 to 100%, more preferably 25 to 100%, and even more preferably 50 to 100%, from the viewpoints of the effect of suppressing the generation of impurity gases due to leakage current and maintainability.

[0116] Furthermore, the proportion (surface coverage) of the surface area covered by the manifold covering member 30 to the total surface area of ​​the manifolds 20 provided on all inner frame elements (elements other than the cathode terminal element 51c and the anode terminal element 51a) is preferably 13 to 100%, more preferably 25 to 100%, and even more preferably 50 to 100%, from the viewpoints of the effect of suppressing the generation of impurity gas due to leakage current and maintainability. In particular, the proportion of the surface area covered by the manifold covering member 30 (surface coverage rate) to the surface area of ​​the manifolds 20 provided on each inner frame element is preferably 13 to 100%, more preferably 25 to 100%, and even more preferably 50 to 100%, from the viewpoints of the effect of suppressing the generation of impurity gases due to leakage current and maintainability.

[0117] The surface coverage is calculated for the surface of the manifold 20 excluding the openings of the capillaries leading to the electrode chambers. The inlet and outlet pipes connected to the terminal elements are not included in the manifold 20.

[0118] 4(b) shows an example of a state in which the manifold covering member 30 integrated with the gasket 7 and the above-mentioned resin spacer 40 are attached to the bipolar electrolytic element 60. In FIG. 4(b), the manifold covering member 30 (30ao) covers 100% of the surface of the anode outlet header portion 20ao.

[0119] From the viewpoint of preventing the generation of impurity gases due to leakage current, the manifold covering member 30 integrated with the gasket 7 is preferably attached to at least one element, more preferably attached to at least the cathode terminal element 51c, even more preferably attached to at least the cathode terminal element 51c and the anode terminal element 51a, even more preferably attached to the cathode terminal element 51c, the anode terminal element 51a, and part of the inner frame element, and particularly preferably attached to all elements.

[0120] The material of the manifold covering member 30 is not particularly limited, but similar to the gasket 7, it preferably contains at least an insulating material such as a known rubber material or resin material having insulating properties. Specific examples of materials for the manifold covering member 30 include rubber materials such as natural rubber (NR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), silicone rubber (SR), ethylene-propylene rubber (EPT), ethylene-propylene-diene rubber (EPDM), fluororubber (FR), isobutylene-isoprene rubber (IIR), urethane rubber (UR), and chlorosulfonated polyethylene rubber (CSM); fluororesin materials such as PTFE, PFA, ETFE, and chlorotrifluoroethylene-ethylene copolymer (ECTFE); and resin materials such as polyphenylene sulfide (PPS), polyethylene, polyimide, and polyacetal. These materials may be used alone or in combination. From the standpoints of ease of fabrication and alkali resistance, it is preferable for the manifold covering member 30 to be made of at least one material selected from the group consisting of rubber materials and polytetrafluoroethylene (PTFE). Rubber materials are more preferable because they are less prone to cracking than resin materials, have good creep characteristics, and are therefore more durable, and are softer than polytetrafluoroethylene (PTFE) and have better conformability when covering the surface of the manifold, with EPDM and FR being particularly suitable.

[0121] The elastic modulus of manifold covering member 30 is not particularly limited, and is designed depending on the shape of manifold 20 and the material of gasket 7. A preferred range of elastic modulus is a tensile stress at 100% deformation of 0.20 to 20 MPa, and from the viewpoint of conformability when covering the surface of manifold 20 and member strength, a range of 1.0 to 10 MPa is more preferred, and a range of 1.0 to 5.0 MPa is even more preferred. The tensile stress can be measured in accordance with JIS K6251. For example, an Autograph AG manufactured by Shimadzu Corporation may be used. The test temperature is in accordance with JIS K6250, 6.1 (standard temperature in the test room: 23±2°C).

[0122] The thickness of the manifold covering member 30 is not particularly limited and may be determined depending on the size of the manifold 20, the thickness of the gasket 7, etc., but from the viewpoint of ease of manufacturing the member and ease of handling, it is preferably 0.5 to 10 mm, more preferably 1.0 to 8.0 mm, and even more preferably 2.0 to 6.0 mm.

[0123] The method for manufacturing the manifold covering member 30 integrated with the gasket 7 is not particularly limited, and any existing method can be used. Examples include a method of integrally molding them using a mold, or a method of manufacturing the gasket 7 and the manifold covering member 30 and then joining them together.

[0124] Next, the components of the electrolysis device 70 other than the bipolar electrolytic cell 50 will be mainly described.

[0125] - Liquid delivery pump - The liquid feed pump 71 is not particularly limited and may be determined as appropriate. The liquid feed pump 71 that can be used in the electrolysis device 70 of this embodiment can include a cathode-side liquid feed pump for feeding liquid to the cathode chamber 5c and an anode-side liquid feed pump for feeding liquid to the anode chamber 5a, and these can be operated separately.

[0126] -Gas-liquid separation tank- The gas-liquid separation tank 72 includes a hydrogen separation tank 72h that separates the electrolytic solution from hydrogen gas, and an oxygen separation tank 72o that separates the electrolytic solution from oxygen gas. The hydrogen separation tank 72h is connected to the cathode chamber 5c, and the oxygen separation tank 72o is connected to the anode chamber 5a.

[0127] -Water supply device- The water supply device used in the electrolysis device 70 is not particularly limited and may be determined as appropriate. As the water, ordinary tap water may be used, but when considering operation over a long period of time, it is preferable to use ion-exchanged water, RO water, ultrapure water, etc.

[0128] -Electrolytic power source- The electrolysis device 70 is equipped with an electrolysis power supply (rectifier) ​​74. Furthermore, an electric circuit may be formed that includes the bipolar electrolytic cell 50 and the electrolysis power supply 74. Furthermore, the electrolysis device 70 may be equipped with an external load that is connected to the bipolar electrolytic cell 50. In particular, in this embodiment, it is preferable that the electrolysis device 70 is equipped with an electric circuit and an external load. 1 , the anode 2a of the electrolytic cell 65 at the end of the bipolar electrolytic cell 50 is connected to the positive electrode of the electrolytic power supply 74 by a cable, and the cathode 2c of the electrolytic cell 65 at the end of the bipolar electrolytic cell 50 is connected to the negative electrode of the electrolytic power supply 74 by a cable, but these cables may also be connected by an external load and a switch. As a result, for example, in the shutdown step, by closing the switch while the electrolytic power supply 74 is stopped, a circuit can be formed between the bipolar electrolytic cell 50 (all of the electrolytic cells 65) and the external load. Furthermore, the external load may be connected to all of the electrolytic cells 65 of the bipolar electrolytic cell 50, or may be connected to only some of the electrolytic cells 65. As a result, for example, in the shutdown step, a circuit can be formed between some of the electrolytic cells 65 of the bipolar electrolytic cell 50 and the external load.

[0129] -Storage tank- The electrolysis device 70 may have a storage tank for storing the electrolyte. Preferably, the storage tank is located vertically above the bipolar electrolytic cell 50. By connecting the storage tank and the bipolar electrolytic cell 50 with piping or the like, the electrolyte in the storage tank can be injected into the electrolytic cell by utilizing gravity. The flow rate can also be appropriately adjusted by providing a valve or the like on the piping or the like.

[0130] -Inlet / outlet piping- The electrolysis device 70 has an inlet pipe for supplying the electrolytic solution to the bipolar electrolytic cell 50 and an outlet pipe for discharging the electrolytic solution from the bipolar electrolytic cell 50, each of which is connected to a storage tank or the like. The inlet pipe and the outlet pipe may have a valve or the like for appropriately adjusting the flow rate of the electrolytic solution. From the viewpoint of preventing deterioration of gas purity due to leakage current, it is preferable that both the inlet pipe and the outlet pipe are connected to the anode terminal element 51a of the bipolar electrolytic cell 50.

[0131] -others- The electrolysis device 70 may include an oxygen concentration meter 75, a hydrogen concentration meter 76, a flow meter 77, a pressure meter 78, a heat exchanger 79, a pressure control valve 80, and the like, in addition to the bipolar electrolytic cell 50, a liquid feed pump 71, a gas-liquid separation tank 72, a water supply unit, an electrolysis power supply 74, a storage tank, and inlet / outlet piping (see FIG. 1 ).

[0132] Moreover, the electrolysis device 70 preferably further includes a detector that detects a power supply interruption and a controller that automatically stops the liquid feed pump 71. By including the detector and the controller, it becomes possible to efficiently reduce the effects of self-discharge without manual operation, even under a power source that fluctuates greatly, such as renewable energy.

[0133] (Hydrogen production method) The method for producing hydrogen according to this embodiment can be carried out by electrolyzing water using the electrolysis device 70 according to this embodiment.

[0134] In this embodiment, the electrolysis device 70 of this embodiment is operated at a current density of 0 to 20 kA / m 2 Therefore, it can be used without any problems under a power source where the current density fluctuates over time and at an electrolysis temperature of 0 to 120°C.

[0135] On the other hand, in the hydrogen production method of this embodiment, the temperature of the electrolytic solution in the electrolytic cell 65 is preferably 40°C or higher, more preferably 70°C or higher, and is preferably 110°C or lower, more preferably 95°C or lower. Within the above temperature range, it is possible to effectively prevent the components of the electrolysis device 70 from being deteriorated by heat while maintaining high electrolysis efficiency.

[0136] Furthermore, in the hydrogen production method of this embodiment, the current density applied to the electrolytic cell 65 is not particularly limited, but is preferably 0.1 kA / m 2 ~20kA / m 2 is preferably 0.5 kA / m 2 ~15kA / m 2 It is more preferable that: In particular, when a variable power supply is used, it is preferable to set the upper limit of the current density within the above range.

[0137] Preferred conditions for the hydrogen production method of this embodiment are described below.

[0138] The electrolyte used in this embodiment may be an alkaline aqueous solution in which an alkaline salt is dissolved, such as an aqueous NaOH solution or an aqueous KOH solution. The concentration of the alkali salt is preferably 10 to 50 mass %, more preferably 15 to 40 mass %. In this embodiment, from the viewpoints of ionic conductivity, kinematic viscosity, and freezing at low temperatures, a 25 to 40 mass % KOH aqueous solution is particularly preferred.

[0139] In the hydrogen production method of this embodiment, the pressure inside the electrolytic cell 65 is preferably 3 kPa or more, more preferably 70 kPa or more, and even more preferably 200 kPa or more, from the viewpoint of the compressor load. From the viewpoint of gas purity, the pressure is preferably 4000 kPa or less, more preferably 1000 kPa or less, and even more preferably 800 kPa or less.

[0140] In this embodiment, the components of the electrolysis device 70 described above can be used to fabricate an electrolysis device 70 having a configuration such as that shown in FIG. 1, but the present invention is not limited to this.

[0141] The method for producing hydrogen according to this embodiment may use electricity with a fluctuating load, and vary the electrolysis current in response to the load fluctuation. The hydrogen production method of this embodiment exhibits the above-mentioned effects more prominently by using a power source (variable power source) derived from at least one renewable energy output selected from the group consisting of wind power, solar power, hydroelectric power, tidal power, wave power, ocean current power, and geothermal power. When a variable power supply as described above is used, specifically, current densities ranging from low to high are randomly applied to the electrolysis device 70, and the hydrogen concentration in oxygen deteriorates, particularly at low current densities. However, by employing the hydrogen production method of this embodiment, it is possible to suppress the deterioration of the hydrogen concentration in oxygen. [Example]

[0142] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0143] The measurement and evaluation methods used in the examples and comparative examples are explained below.

[0144] (1) Cell voltage Current density 10kA / m 2 After 2 hours, the average value of the voltage across the electrolytic cell was calculated and evaluated as the cell voltage (V).

[0145] (2) Gas purity Current density 1kA / m 2 Alkaline water electrolysis was performed by passing current continuously for 6 hours. After 6 hours, the hydrogen concentration (%) in oxygen obtained by alkaline water electrolysis was measured by gas chromatography. Note that a lower hydrogen concentration in oxygen is preferable because it falls outside the explosive range (the range of compositional concentrations of mixed gases in which an explosion occurs when hydrogen is mixed with oxygen and a fire source is brought close). The evaluation was carried out according to the following criteria. [Evaluation criteria] ◎ (Excellent): Hydrogen concentration in oxygen is 0.5% or less ○ (Good): Hydrogen concentration in oxygen is over 0.5% and 1% or less × (bad): Hydrogen concentration in oxygen exceeds 1%

[0146] (3) Long-term maintenance of gas purity Current density 10kA / m 2 Alkaline water electrolysis was carried out at a current density of 1 kA / m for 1000 hours. 2 After 6 hours, the hydrogen concentration (%) in oxygen obtained by alkaline water electrolysis was measured by gas chromatography. The evaluation was carried out according to the following criteria. [Evaluation criteria] ◎ (Excellent): Hydrogen concentration in oxygen is 0.5% or less ○ (Good): Hydrogen concentration in oxygen is over 0.5% and 1% or less × (bad): Hydrogen concentration in oxygen exceeds 1%

[0147] (4) Maintainability The maintainability of the electrolytic cell was evaluated according to the following evaluation criteria. [Evaluation criteria] ◎ (Excellent): Maintenance can be performed by replacing only the gasket integrated with the manifold covering material, and the number of gaskets integrated with the manifold covering material is two or less. ○ (Good): Maintenance is possible by replacing only the gasket integrated with the manifold covering material, and there are more than two gaskets integrated with the manifold covering material. × (bad): The entire electrolytic cell needs to be replaced due to peeling of the resin coating interface, etc.

[0148] [Example 1] A bipolar alkaline water electrolysis element and an alkaline water electrolysis device using the same were fabricated as follows. -Partition walls, outer frames- A bipolar alkaline water electrolysis element was used that included a partition wall that separated the anode and cathode and an outer frame that surrounded the partition wall. All of the materials that came into contact with the electrolytic solution, such as the partition wall and the outer frame, were made of nickel. -anode- The anode was made by using a nickel expand substrate that had been subjected to a blasting treatment in advance, and spraying nickel oxide granules onto both sides of the conductive substrate by plasma spraying. -cathode- The conductive substrate used was a plain-woven mesh substrate made of nickel thin wires with a diameter of 0.15 mm woven at 40 meshes, on which platinum was supported. -diaphragm- The diaphragm used was Zirfon perl UTP500 manufactured by Agfa. -Zero gap structure- The elements were stacked with a gasket interposed between them to assemble a bipolar alkaline water electrolyzer, whereby the cathode and anode were pressed against each other from both sides of the diaphragm to form a zero-gap structure. The gasket used was integrated with the manifold covering member and sandwiched the diaphragm. The anode side used only an anode, and the cathode side used a cathode structure consisting of a combination of a cathode, a conductive elastic body, and a current collector. The current collector was a nickel expand substrate that had been pre-blasted. The substrate had a thickness of 1 mm and an aperture ratio of 54%. The conductive elastic body used was a woven nickel wire with a wire diameter of 0.15 mm that was corrugated to a wave height of 5 mm. The conductive elastic body was fixed onto the current collector by spot welding. The anode and cathode used were the same as those described above.

[0149] -Bipolar alkaline water electrolysis cell, bipolar alkaline water electrolysis element An anode terminal element, a cathode terminal element, and ten bipolar alkaline water electrolysis elements were used. As shown in Figure 2, a fast head, an insulating plate, and an anode terminal element were arranged at one end, followed by ten sets of an anode gasket, a diaphragm, a cathode gasket, and a bipolar alkaline water electrolysis element, arranged in that order. An anode gasket, a diaphragm, and a cathode gasket were also arranged, followed by a cathode terminal element, an insulating plate, and a loose head at the other end. These were then stacked by tightening the gaskets from both sides of the fast head and loose head with a gasket sealing surface pressure of 2.5 MPa to assemble a bipolar alkaline water electrolysis cell. This bipolar alkaline water electrolysis cell had ten pairs of series-connected cathode and anode chambers, each with ten chambers.

[0150] -Manifold- An internal manifold-type bipolar alkaline water electrolysis element was prepared using a nickel manifold. As shown in Fig. 3 and Fig. 4 , the manifold was arranged so that all headers (anode inlet header, cathode inlet header, anode outlet header, and cathode outlet header) extended in a direction perpendicular to the partition wall (so as to extend in the direction along the stack direction).

[0151] -gasket- The gasket used was made of EPDM, had an elastic modulus of 4.0 MPa at 100% deformation, and was 4.0 mm thick. The dimensions of the opening in plan view of this gasket were the same as the dimensions of the electrode chamber in the cell frame, and the gasket had a 0.4 mm thick slit structure in the center of the thickness direction of the inner wall of the opening, for inserting and holding a diaphragm. The inner frame gasket had, on one surface, an anode inlet manifold covering member that covers the anode inlet header portion of the manifold and an anode outlet manifold covering member that covers the anode outlet header portion, and the other surface had a cathode inlet manifold covering member that covers the cathode inlet header portion of the manifold and a cathode outlet manifold covering member that covers the cathode outlet header portion. The anode terminal gasket had, on a surface in contact with the anode terminal element, an anode inlet manifold covering member that covers the anode inlet header portion of the manifold, an anode outlet manifold covering member that covers the anode outlet header portion, a cathode inlet manifold covering member that covers the cathode inlet header portion, and a cathode outlet manifold covering member that covers the cathode outlet header portion, and had, on the other surface, an anode inlet manifold covering member that covers the anode inlet header portion of the manifold and an anode outlet manifold covering member that covers the anode outlet header portion. The cathode terminal gasket has, on both surfaces, a cathode inlet manifold covering member that covers the cathode inlet header portion of the manifold, and a cathode outlet manifold covering member that covers the cathode outlet header portion. The gasket portion that comes into contact with the anode manifold (anode inlet header portion and anode outlet header portion) of the element adjacent to the cathode terminal element is plugged and has no holes, preventing the cathode terminal element from coming into contact with the electrolyte at that portion. The thickness of each manifold covering member was 3.0 mm, and EPDM (modulus of elasticity at 100% deformation: 4.0 MPa) was used as the material for each manifold covering member. The anode terminal gasket was placed between the anode terminal element and its adjacent element, the cathode terminal gasket was placed between the cathode terminal element and its adjacent element, and the inner frame gasket was placed between the inner frame elements. At this time, the manifold covering members corresponding to each header section were inserted, and each header section was covered with each manifold covering member (Figure 6(a) shows the attached inner frame gasket). An adhesive was used to secure the manifold covering members. The coverage of the manifold surface with the manifold covering member was 100% in all cases. In this way, an internal manifold type bipolar alkaline water electrolytic cell was fabricated.

[0152] An alkaline water electrolysis apparatus as shown in Fig. 1 was fabricated using a liquid feeding pump, a water supply device, and the like that are commonly used in the relevant technical field. The inlet pipe and outlet pipe connected to the storage tank were both connected to an anode terminal element.

[0153] The electrolyte was allowed to flow from the cathode inlet header to the cathode chamber and from the cathode chamber to the cathode outlet header, and also from the anode inlet header to the anode chamber and from the anode chamber to the anode outlet header. The cathode inlet header was connected to one end of the lower side of the rectangular outer frame in plan view, and the cathode outlet header was connected to the upper side of the side that connects to the other end of the lower side of the rectangular outer frame in plan view (see Figure 3). Here, the cathode inlet header and cathode outlet header were arranged facing each other across the center of the electrode chamber in the rectangular electrolysis chamber in plan view. The electrolyte flowed from bottom to top at an angle relative to the vertical and rose along the electrode surface. The bipolar electrolytic cell of this example was configured so that the electrolyte flowed into the anode chamber and the cathode chamber through the electrolyte inlets of the anode chamber and the cathode chamber, and the electrolyte and generated gas flowed out of the bipolar electrolytic cell through the electrolyte outlets of the anode chamber and the cathode chamber. In the cathode chamber, hydrogen gas was generated by electrolysis, and in the anode chamber, oxygen gas was generated by electrolysis. As a result, a multiphase flow of the electrolytic solution and hydrogen gas was formed in the cathode outlet header, and a multiphase flow of the electrolytic solution and oxygen gas was formed in the anode outlet header.

[0154] A method for producing hydrogen using an alkaline water electrolysis device was carried out under the following conditions. A 30% KOH aqueous solution was used as the electrolyte. Electricity was applied from an electrolysis power source (rectifier) ​​to the bipolar alkaline water electrolytic cell so as to achieve the desired current density relative to the cathode and anode areas of the bipolar alkaline water electrolytic cell. The temperature was adjusted by a heat exchanger so that the temperature at the outlet of the electrolytic cell was 90°C. The liquid transfer pump was used to circulate between the anode chamber, oxygen separation tank (gas-liquid separation tank for the anode), and anode chamber, and between the cathode chamber, hydrogen separation tank (gas-liquid separation tank for the cathode), and cathode chamber. The pressure inside the vessel after the start of energization was measured with a pressure gauge and adjusted so that the pressure on the cathode (hydrogen gas) side was 50 kPa and the pressure on the anode (oxygen gas) side was 49 kPa. The pressure adjustment was performed using a control valve installed downstream of the pressure gauge.

[0155] [Example 2] An alkaline water electrolysis device was produced in the same manner as in Example 1 except that terminal gaskets integrated with the same manifold covering member as in Example 1 were used only between a cathode terminal element and its adjacent element, and between an anode terminal element and its adjacent element, and gaskets without a manifold covering member ( Fig. 7( a) shows an attached state of an inner frame gasket without a manifold covering member) were used between the other elements (inner frame elements) (i.e., the manifolds were not covered with manifold covering members).

[0156] [Example 3] An alkaline water electrolysis device was produced in the same manner as in Example 1, except that terminal gaskets having manifold covering members with a manifold surface coverage of 50% were used between the cathode terminal element and its adjacent element, and between the anode terminal element and its adjacent element, and inner frame gaskets having manifold covering members with a manifold surface coverage of 50% were used between the other elements (inner frame elements) (the attached state of the inner frame gasket is shown in Fig. 6(b) ).

[0157] [Example 4] An alkaline water electrolysis apparatus was produced in the same manner as in Example 1, except that a resin spacer was disposed on the outer side of the gasket integrated with the manifold covering member ( Fig. 6( c ) shows the attached state of the inner frame gasket and resin spacer). By using the resin spacer, the pressure inside the electrolytic cell during electrolysis operation could be increased to 800 kPa, which was higher than that in Example 1.

[0158] [Example 5] An alkaline water electrolysis apparatus was produced in the same manner as in Example 1, except that PTFE (having an elastic modulus of 9.0 MPa at 100% deformation) was used as the material for each manifold covering member.

[0159] In Examples 1-5, the low cell voltages indicated that hydrogen could be produced efficiently. In Example 1, the entire surface of the manifold was protected by the manifold covering member, which prevented the generation of impurity gases due to leakage current. Therefore, the hydrogen concentration in oxygen was low at low current densities, resulting in high gas purity. Furthermore, high gas purity could be maintained even after long-term use. Furthermore, replacement of the entire electrolytic cell was not required, resulting in high maintainability. In Example 2, when a gasket integrated with the manifold covering member was used only between the terminal element and its adjacent element, the effect of suppressing the generation of impurity gas due to leakage current was observed, although not as effective as in Example 1, and the gas purity was high. Furthermore, high gas purity could be maintained even after long-term use. Furthermore, because replacement of each electrolytic cell was not required and the number of gaskets integrated with the manifold covering member was small, assembly of the electrolytic cell was easier and maintenance was high. In Example 3, a gasket having a manifold covering member with a manifold surface coverage of 50% was used, and although not as effective as in Example 1, the effect of suppressing the generation of impurity gas due to leakage current was observed, and the gas purity was high. Furthermore, high gas purity could be maintained even after long-term use. In addition, replacement of the entire electrolytic cell was not required, and maintainability was high. In Example 4, when a resin spacer was used, the pressure inside the electrolytic cell during electrolysis operation could be increased, and even in this case, the generation of impurity gas due to leakage current was suppressed, resulting in high gas purity. Furthermore, high gas purity could be maintained even after long-term use. In addition, replacement of the entire electrolytic cell was not required, resulting in high maintainability. In Example 5, PTFE was used as the material for the manifold covering member. Although not as effective as in Example 1, in which EPDM was used as the material for the manifold covering member, the effect of suppressing the generation of impurity gas due to leakage current was still observed, and the gas purity was high. Furthermore, although a slight deterioration in gas purity was observed after long-term use, a gas purity that was sufficient for practical use could be maintained. In addition, replacement of the entire electrolytic cell was not required, and maintainability was high.

[0160] [Comparative Example 1] An alkaline water electrolysis device was produced in the same manner as in Example 1, except that gaskets without manifold covering members ( Fig. 7( a) shows an attached state of an inner frame gasket without a manifold covering member) were used between all elements (i.e., the manifolds were not covered with manifold covering members). Since the metal surface that was not protected by the manifold covering member was exposed over the entire surface of the manifold, the hydrogen concentration in oxygen was high and the gas purity was poor compared to the Examples, both at the start of electrolysis and over the long term.

[0161] Comparative Example 2 An alkaline water electrolysis apparatus was produced in the same manner as in Example 1, except that the surfaces of all manifolds (header portions) were coated with PTFE by the method described in Examples of Japanese Patent No. 6404685, and gaskets without a manifold covering member were used ( Fig. 7( b) shows the attached state of an inner frame gasket without a manifold covering member and the PTFE coating). Because the surface of the manifold was protected by a coating material, the generation of impurity gases due to leakage current was suppressed at the beginning of electrolysis, the hydrogen concentration in oxygen was low, and the gas purity was high. However, the coating material peeled off during long-term use, making it impossible to maintain high gas purity. Furthermore, repairing peeled coating material required replacing the entire electrolytic cell, making maintenance difficult.

[0162] [Table 1] [Industrial Applicability]

[0163] An electrolytic cell using the internal manifold type bipolar electrolytic element of the present invention can suppress the generation of impurity gases due to leakage current, can vary the electrolytic current in response to load fluctuations to control output, and can maintain the production of highly efficient and highly pure hydrogen over a long period of time. Furthermore, industrial production is easy, component maintenance is simple, and replacement of the entire electrolytic cell frame is not necessary. Furthermore, operation time can be significantly reduced, and electrolysis downtime can be minimized. Therefore, the electrolytic cell can be suitably used for hydrogen production by electrolysis (water electrolysis, particularly alkaline water electrolysis). [Explanation of symbols]

[0164] 1 Bulkhead 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 5ai anolyte inlet 5ao anolyte outlet 5ci catholyte inlet 5co catholyte outlet 6 Rectifier plate 6a Anode rectifier plate (anode rib) 6c Cathode rectifier plate (cathode rib) 7 Gasket 20 Manifold 20i Inlet header 20ai Anode inlet header 20ci cathode inlet header 20o Exit header 20ao Anode outlet header 20co cathode outlet header 30 Manifold covering member 30ai Anode inlet manifold covering member 30ci cathode inlet manifold covering 30ao Anode outlet manifold covering material 30co cathode outlet manifold covering material 40 Resin spacer 50 bipolar electrolyzer 51g fast head, loose head 51a Anode terminal element 51c Cathode Terminal Element 51r tie rod 51i Insulating plate 60 Bipolar electrolytic element 65 Electrolysis Cell 70 Electrolyzer 71 Liquid transfer pump 72 Gas-liquid separation tank 72h Hydrogen Separation Tank 72o Oxygen Separation Tank 74 Electrolytic power supply 75 Oxygen concentration meter 76 Hydrogen concentration meter 77 Flow meter 78 Pressure Gauge 79 Heat exchanger 80 Pressure control valve D1 given direction along the bulkhead (vertical direction) Z Zero gap structure C Resin coating

Claims

1. an internal manifold-type bipolar alkaline water electrolysis element comprising an anode, a cathode, a partition wall, and an outer frame, and having a manifold; the anode, the cathode, the partition wall, the outer frame, and the manifold are electrically conductive; At least a portion of the surface of the manifold is covered with a manifold covering member, When the total surface area of ​​all the manifolds is taken as 100%, the proportion of the surface area covered by the manifold covering member (surface coverage rate) is 13 to 100%; The manifold covering member is integrated with a gasket, is detachable, and is made of at least an insulating material. An internal manifold type bipolar alkaline water electrolysis element characterized by:

2. The internal manifold type bipolar alkaline water electrolysis element according to claim 1 , wherein at least a portion of the surface of the manifolds of the cathode terminal element and the anode terminal element is covered with the manifold covering member.

3. The internal manifold type bipolar alkaline water electrolysis element according to claim 1 or 2, wherein the manifold covering member is made of at least one material selected from the group consisting of a rubber material and polytetrafluoroethylene.

4. The internal manifold type bipolar alkaline water electrolysis element according to claim 1 or 2, wherein the manifold covering member is made of a rubber material.

5. 3. The internal manifold type bipolar alkaline water electrolysis element according to claim 1 or 2, wherein a resin spacer is disposed on the outside of the gasket, and the compressive elastic modulus of the resin spacer is greater than the compressive elastic modulus of the gasket.

6. 3. An internal manifold type bipolar alkaline water electrolytic cell, comprising the internal manifold type bipolar alkaline water electrolysis element according to claim 1 or 2 and a diaphragm stacked with the gasket interposed therebetween to form an electrolytic cell.

7. 7. The internal manifold type bipolar alkaline water electrolyzer according to claim 6, wherein the manifold is disposed outside the diaphragm.

8. 7. The internal manifold type bipolar alkaline water electrolytic cell according to claim 6, wherein an inlet pipe and an outlet pipe are connected to the anode terminal element.

9. A method for producing hydrogen, comprising using the internal manifold type bipolar alkaline water electrolytic cell according to claim 6.

10. The method for producing hydrogen according to claim 9, wherein the pressure inside the electrolytic cell during electrolysis operation is 3 to 4000 kPa.

11. The method for producing hydrogen according to claim 9, wherein the power source that supplies the electricity is a power source derived from at least one renewable energy output selected from the group consisting of wind power, solar power, hydroelectric power, tidal power, wave power, ocean current power, and geothermal power.

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