Water electrolysis cell

Abstract

The invention provides a water electrolysis cell with high durability. The water electrolysis cell is provided with a resin frame. The housing is provided with an opening, and manifold holes for discharging oxygen, the manifold holes being disposed around the opening. The water electrolysis cell is provided with a membrane electrode assembly disposed inside the opening. The water electrolysis cell is provided with a first diaphragm and a second diaphragm. The first separator and the second separator face each other via the frame and the membrane electrode assembly, and are joined to each other via the frame. The inner peripheral surface of the frame defining the opening and the manifold hole has hydrophobicity such that the contact angle of water is 100 DEG or more.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a water electrolysis chamber. Background Technology

[0002] Patent Document 1 discloses a water electrolysis chamber. In this chamber, a membrane electrode assembly is disposed within the opening of a resin frame. An anode diaphragm is bonded to one side of the frame, and a cathode diaphragm is bonded to the other side of the frame. This ensures a tight seal.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2024-62492

[0004] Oxygen is generated during water electrolysis. If the periphery of the membrane electrode assembly is oxidized and deteriorated due to this generated oxygen, the seal cannot be maintained, resulting in reduced durability of the water electrolysis chamber. Summary of the Invention

[0005] The water electrolysis chamber disclosed in this specification comprises a resin frame. The frame has an opening and a manifold for oxygen discharge disposed around the opening. The water electrolysis chamber includes a membrane electrode assembly disposed inside the opening. The water electrolysis chamber includes a first diaphragm and a second diaphragm. The first and second diaphragms are positioned opposite each other via the frame and the membrane electrode assembly, and are joined together via the frame. The inner circumferential surfaces of the frame defining the opening and the manifold have hydrophobicity with a water contact angle of 100° or more.

[0006] The inventors discovered that oxidative degradation of the frame is prone to occur on the inner circumferential surface of the defined opening and manifold orifice. Furthermore, they found that the simultaneous presence of water and oxygen promotes oxidative degradation of the frame. Based on the above structure, compared to a case where the inner circumferential surface is not hydrophobic, the contact time between the inner circumferential surface and water can be reduced. Since the time the inner circumferential surface is exposed to dissolved oxygen in water can be reduced, oxidative degradation of the inner circumferential surface can be suppressed.

[0007] It should be noted that in most resins (e.g., polypropylene), the water contact angle is mostly below 95°. Therefore, the hydrophobic inner circumferential surface with a water contact angle of 100° or more is a feature specific to the technology described in this specification. Attached Figure Description

[0008] Figure 1 This is an exploded three-dimensional view of water electrolysis chamber 1.

[0009] Figure 2 yes Figure 1 A partial sectional view of line II-II.

[0010] Figure 3 This is a magnified view of the end of the opening 54.

[0011] Figure 4 This is a partial cross-sectional view of Embodiment 2.

[0012] Figure 5 This is a table representing the results of the first experiment.

[0013] Figure 6 This is a table representing the results of the second experiment.

[0014] Explanation of reference numerals in the attached figures

[0015] 1: Water electrolysis chamber; 10: First diaphragm; 20: Second diaphragm; 40: Membrane electrode assembly; 50: Frame; 54: Opening; 56: Manifold hole; 54i, 56i1, 56i2: Inner circumferential surface. Detailed Implementation

[0016] The inner circumference of the frame can also be provided with concave and convex shapes to enhance hydrophobicity.

[0017] Based on the above structure, hydrophobicity can be achieved through the shape of the inner circumferential surface. Since there is no need to additionally provide layers or other materials to achieve hydrophobicity, manufacturing costs can be reduced.

[0018] A hydrophobic layer can also be provided on the inner circumferential surface of the frame to provide hydrophobicity.

[0019] Based on the above structure, hydrophobicity can be obtained by utilizing the hydrophobic layer.

[0020] The hydrophobic layer can contain substances with a needle-like crystal structure.

[0021] Examples of substances with a needle-like crystal structure include manganese oxide, magnesium oxide, and zinc oxide. Based on this structure, fine irregularities can be formed on the surface of the hydrophobic layer, thus achieving high hydrophobicity.

[0022] The hydrophobic layer can be made of fluorinated resin or silicone resin.

[0023] Based on the above structure, the surface tension of the inner circumferential surface can be reduced, thus achieving hydrophobicity.

[0024] Example 1

[0025] (Simplified structure of water electrolysis chamber 1)

[0026] Figure 1 This is an exploded perspective view of the water electrolysis chamber 1. The water electrolysis chamber 1 mainly comprises a first diaphragm 10, a second diaphragm 20, a membrane electrode assembly 40, and a frame 50. The membrane electrode assembly 40 electrolyzes water to produce hydrogen and oxygen. The structure of the membrane electrode assembly 40 will be described later.

[0027] The frame 50 is made of insulating resin. For example... Figure 1As shown, an opening 54 penetrating through the frame 50 is provided in the center of the frame 50. A membrane electrode assembly 40 is disposed within the opening 54. That is, the frame 50 surrounds the membrane electrode assembly 40.

[0028] The first diaphragm 10 and the second diaphragm 20 are made of an airtight conductive material. Examples of materials for the diaphragms include metallic materials such as stainless steel or carbon materials. The first diaphragm 10 and the second diaphragm 20 are positioned opposite each other with respect to the membrane electrode assembly 40 and the frame 50.

[0029] A plurality of manifold holes 56 are provided around the opening 54 of the frame 50. A plurality of manifold holes 16 are provided on the first diaphragm 10. A plurality of manifold holes 26 are provided on the second diaphragm 20. The manifold holes 16 and 26 are respectively located at positions overlapping with the manifold hole 56. By connecting the manifold holes 16, 56, and 26, a first supply path 61, a first discharge path 62, a second supply path 63, a second discharge path 64, a third supply path 65, and a drainage path 66 are formed, respectively. These flow paths penetrate the water electrolysis chamber 1 in the thickness direction. Two or more pairs of manifolds in these flow paths can also be used.

[0030] (Specific structure of water electrolysis chamber 1)

[0031] Figure 2 express Figure 1 A partial sectional view of line II-II. Figure 2 This is a cross-sectional view through manifold orifice 56. Manifold orifice 56 is the orifice that forms the second exhaust path 64 for discharging oxygen.

[0032] The membrane electrode assembly 40 includes a hydrogen electrode 41, an oxygen electrode 42, and an electrolyte membrane 43. The electrolyte membrane 43 is an ion exchange membrane with proton conductivity, formed from a solid polymer material. The hydrogen electrode 41 includes a first catalyst layer 44 and a first gas diffusion layer 45. The oxygen electrode 42 includes a second catalyst layer 46 and a second gas diffusion layer 47. The first catalyst layer 44 and the second catalyst layer 46 are porous layers formed by bonding catalyst-supported carbon particles or metal oxides with resin. The first gas diffusion layer 45 and the second gas diffusion layer 47 are conductive components with water permeability and gas permeability.

[0033] Electrolyte membrane 43, hydrogen electrode 41, and oxygen electrode 42 are rectangular in shape. Hydrogen electrode 41 is the same size as electrolyte membrane 43, and oxygen electrode 42 is smaller than electrolyte membrane 43. A frame-shaped peripheral region PA, without a second catalyst layer 46, is formed on the upper surface 43u of electrolyte membrane 43. An adhesive layer 49 is disposed on the upper surface 43u within the peripheral region PA. Adhesive layer 49 is a layer formed by applying an adhesive. As an example of an adhesive, an adhesive containing an organic solvent and with UV curing properties can be cited.

[0034] The frame 50 has a three-layer structure consisting of a first resin layer 51, a core layer 53, and a second resin layer 52 stacked in the thickness direction. The core layer 53 is a structural component with gas-tight and insulating properties. The first resin layer 51 is a layer bonded to the first diaphragm 10. The second resin layer 52 is a layer bonded to the second diaphragm 20.

[0035] The first resin layer 51 and the second resin layer 52 may have a lower viscosity and melting point than the core layer 53. Specifically, the first resin layer 51 and the second resin layer 52 may be thermoplastic resins such as acid-modified olefins and polyesters.

[0036] Furthermore, the multi-layered frame 50 can be formed by various methods. For example, it can be formed by co-extrusion molding. In this embodiment, the core layer 53, the first resin layer 51, and the second resin layer 52 are made of polypropylene.

[0037] When viewed from a direction perpendicular to the membrane electrode assembly 40 (z-direction), an overlapping region OA is formed, where the outer periphery of the membrane electrode assembly 40 overlaps with the inner periphery of the frame 50. Within the overlapping region OA, the frame 50 is bonded to the upper surface 43u of the electrolyte membrane 43 via an adhesive layer 49. Thus, the outer peripheral portion 40e of the membrane electrode assembly 40 extends between the lower surface 51b of the frame 50 and the first diaphragm 10.

[0038] A rib 10r is provided on the first diaphragm 10. The space between the rib 10r and the membrane electrode assembly 40 forms a first flow path 14. Additionally, a rib 20r is provided on the second diaphragm 20. The space between the rib 20r and the membrane electrode assembly 40 forms a second flow path 24. Furthermore, although in Figure 2 The second flow path 24 is connected to the manifold orifice 56 via a flow path not shown in the figure.

[0039] The operation of the water electrolysis chamber 1 will be explained. Nitrogen is supplied to the hydrogen electrode 41 via the first supply path 61 and the first flow path 14. Pure water is supplied to the oxygen electrode 42 via the second supply path 63 and the second flow path 24. The supplied pure water is electrolyzed by the membrane electrode assembly 40. Hydrogen generated from the hydrogen electrode 41 is discharged to the outside via the first flow path 14 and the first discharge path 62. In addition, oxygen generated from the oxygen electrode 42 is discharged to the outside via the second flow path 24 and the second discharge path 64.

[0040] (Hydrophobic finish on frame 50)

[0041] The opening 54 of the frame 50 is defined by the inner circumferential surface 54i (see reference). Figure 1 , Figure 2 (The dashed area). Additionally, the manifold 56 forming the second supply path 63 (pure water supply path) is defined by the inner circumferential surface 56i1 (see reference). Figure 1(The dashed area). Additionally, the manifold orifice 56 forming the second discharge path 64 (oxygen discharge path) is defined by the inner circumferential surface 56i2 (see reference). Figure 1 , Figure 2 (The dotted area). The inner peripheral surfaces 54i, 56i1, and 56i2 have a higher oxygen concentration than the other inner peripheral surfaces. Moreover, in the technology of this specification, the inner peripheral surfaces 54i, 56i1, and 56i2 have hydrophobicity with a water contact angle of 100° or more. More preferably, they have hydrophobicity with a water contact angle of 150° or more.

[0042] The reasons for achieving the above hydrophobicity will be explained. Figure 3 Indicates from Figure 2 A magnified view of the end of the opening 54, viewed in the direction of arrow Y1. Additionally, in Figure 3 For ease of observation, the description of the second septum 20 has been omitted. For example... Figure 3 As shown, an uneven shape for hydrophobicity is provided on the inner peripheral surface 54i. Specifically, a plurality of protrusions PR are arranged at a certain spacing P1. The plurality of protrusions PR have a certain height H1. In addition, the plurality of protrusions PR are continuously formed in the thickness direction (z direction) of the frame 50. As a result, a groove TR extending in the z direction is formed between the plurality of protrusions PR. By forming an air layer in the groove TR, hydrophobicity can be achieved. Furthermore, the above-mentioned uneven shape is also provided in the inner peripheral surfaces 56i1 and 56i2.

[0043] In most resins, the contact angle of water is 95° or less. For example, for olefin resins, the contact angle is approximately 90° for polypropylene and approximately 94° for polyethylene. Furthermore, in this embodiment, the frame 50 is made of polypropylene. Therefore, without the aforementioned uneven shape, the contact angle of water on the inner peripheral surfaces 54i, 56i1, and 56i2 is approximately 90°. On the other hand, in the technology of this specification, due to the aforementioned uneven shape, the contact angle of water on the inner peripheral surfaces 54i, 56i1, and 56i2 is 100° or more. Therefore, whether the inner peripheral surfaces have the uneven shape described in this specification can be determined by measuring whether the contact angle of water is 100° or more.

[0044] Furthermore, various values ​​can be used for height H1 and spacing P1. Additionally, height H1 and spacing P1 are not limited to being constant and can also vary randomly.

[0045] The methods for forming the aforementioned concave and convex shapes can be varied. For example, when the frame 50 is manufactured by punching a resin sheet, it is sufficient to set the mold used to form the inner peripheral surfaces 54i, 56i1, and 56i2 to a concave and convex shape. Alternatively, when the frame 50 is manufactured by laser processing, when processing the inner peripheral surfaces 54i, 56i1, and 56i2, it is sufficient to scan the laser to make them into a concave and convex shape.

[0046] (Effect)

[0047] Oxygen is generated during water electrolysis. If the frame 50 oxidizes and deteriorates due to this generated oxygen, the seal cannot be maintained, leading to a decrease in the durability of the water electrolysis chamber 1. Furthermore, the inventors have discovered that oxidation and deterioration of the frame 50 easily occur on the inner circumferential surface of the opening 54 and the inner circumferential surface of the manifold hole 56. In addition, the inventors have discovered that if water and oxygen are present simultaneously, the dissolved oxygen in the water promotes the oxidation and deterioration of the frame 50. Therefore, in the technology of this embodiment, by forming an uneven shape on the inner circumferential surfaces 54i, 56i1, and 56i2 where the oxygen concentration is high, hydrophobicity with a water contact angle of 100° or more is achieved. As a result, compared to the case where there is no hydrophobicity, the contact time between the inner circumferential surfaces 54i, 56i1, and 56i2 and water can be reduced. Since the time that the inner circumferential surfaces 54i, 56i1, and 56i2 are exposed to dissolved oxygen in water can be reduced, the oxidation and deterioration of the inner circumferential surfaces can be suppressed. The durability of the water electrolysis chamber 1 can be improved.

[0048] In the technology of this embodiment, hydrophobicity can be achieved through the uneven shape of the inner circumferential surface. Since there is no need to provide additional layers or the like for obtaining hydrophobicity, manufacturing costs can be reduced.

[0049] Example 2

[0050] The difference between Example 2 and Example 1 is that a hydrophobic layer is provided on the inner peripheral surfaces 54i, 56i1, and 56i2. Hereinafter, only the features specific to Example 2 will be described. Furthermore, common parts will be labeled with the same reference numerals, and descriptions will be omitted.

[0051] Figure 4 This is a partial cross-sectional view of Example 2. Figure 4 Is with Figure 2 A cross-sectional view at the same location. A hydrophobic layer 70 is disposed on the inner peripheral surfaces 54i, 56i1, and 56i2. The hydrophobic layer 70 makes the inner peripheral surfaces 54i, 56i1, and 56i2 hydrophobic with a water contact angle of 100° or more. The water contact angle is preferably 110° or more, and more preferably 150° or more.

[0052] (The first example of hydrophobic layer 70)

[0053] The hydrophobic layer 70 can be made of various materials. As a first example, the hydrophobic layer 70 may also contain a substance with a needle-like crystal structure. Examples of substances with a needle-like crystal structure include manganese oxide, magnesium oxide, zinc oxide, silicon dioxide, and potassium titanate. In this embodiment, the hydrophobic layer 70 contains manganese oxide or magnesium oxide. On the surface of the hydrophobic layer 70, micron- to nanon-sized micro-uneven structures are formed through the needle-like crystal structure. By allowing air to enter between these uneven structures, superhydrophobicity with a water contact angle of 150° or more can be achieved.

[0054] The method for forming the hydrophobic layer 70 in the first example can be varied. For example, a resin containing a needle-like crystal structure can be coated onto the inner peripheral surfaces 54i, 56i1, and 56i2. Alternatively, for example, microparticles containing a needle-like crystal structure can be sprayed onto the inner peripheral surfaces 54i, 56i1, and 56i2.

[0055] (The second example of hydrophobic layer 70)

[0056] As a second example, the hydrophobic layer 70 can also be made of fluorine-based resin or silicone-based resin. This reduces the surface tension of the inner circumferential surfaces 54i, 56i1, and 56i2, thus achieving hydrophobicity.

[0057] Furthermore, the hydrophobic layer 70 preferably exhibits excellent gas barrier properties. Therefore, fluorinated resins are superior to silicone resins. Additionally, the method for forming the hydrophobic layer 70 in the second example can be varied. For example, a liquid hydrophobic agent can be coated or sprayed onto the inner peripheral surfaces 54i, 56i1, and 56i2.

[0058] Example 3

[0059] The inner circumferential surface was formed using various hydrophobic processes described in Examples 1 and 2. The experimental material was polypropylene. The water contact angle and durability were then investigated. Durability was evaluated based on the lifespan of the water electrolysis chamber 1. It should be noted that durability decreases in the order of ◎>○>△>×, where ◎ represents the highest and × represents the lowest.

[0060] Figure 5 The results of the first experiment are shown. In Comparative Example 1, an inner circumferential surface without hydrophobic processing was prepared. In Experiment 1, a concave-convex shape based on punching was formed on the inner circumferential surface. In Experiment 2, a concave-convex shape based on laser processing was formed on the inner circumferential surface. In Experiment 3, a hydrophobic layer containing a needle-like crystal structure was formed on the inner circumferential surface. Specifically, a hydrophobic layer containing manganese oxide was used.

[0061] As shown in Experiments 1 and 2, when using an uneven shape, the contact angle of the inner circumferential surface processed by punching is larger than that of the inner circumferential surface processed by laser, and the durability is higher. In addition, as shown in Experiment 3, when using a hydrophobic layer containing a needle-like crystal structure, superhydrophobicity with a contact angle of more than 150° can be achieved, and the durability can be maximized.

[0062] Figure 6 The results of the second experiment are shown. In Comparative Example 2, an inner circumferential surface without a hydrophobic layer was prepared. In Experiment 4, a hydrophobic layer of fluoropolymer resin was formed on the inner circumferential surface. In Experiment 5, a hydrophobic layer of silicone resin was formed on the inner circumferential surface. Based on Experiments 4 and 5, it can be seen that, compared with silicone resin, fluoropolymer resin has a larger contact angle, higher gas barrier properties, and higher durability.

[0063] The embodiments have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations to the specific examples illustrated above. The technical elements described in this specification or drawings exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Furthermore, the technology illustrated in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives is itself technically useful.

[0064] <Variation Example>

[0065] Both an uneven shape and a hydrophobic layer can be formed on the inner circumferential surface. For example, a hydrophobic agent can be coated or sprayed onto the inner circumferential surface, which has been formed with an uneven shape by punching or laser processing. This results in higher hydrophobicity.

[0066] The hydrophobicity can also selectively be achieved by having an inner circumferential surface with a higher oxygen concentration, resulting in a water contact angle of 100° or more. That is, it is sufficient to have at least the aforementioned hydrophobicity on the inner circumferential surfaces 54i and 56i2. Alternatively, all manifold holes 56 formed in the frame 50 can also have the aforementioned hydrophobicity.

[0067] The frame 50 is not limited to a 3-layer structure. The technology in this specification can also be applied to frames with single-layer, 2-layer, or 4-layer or higher structures.

Claims

1. A water electrolysis chamber, wherein, have: A frame, which is made of resin, has an opening and a manifold for oxygen discharge disposed around the opening; A membrane electrode assembly disposed inside the opening; and A first diaphragm and a second diaphragm are positioned opposite each other, separated by the frame and the membrane electrode assembly, and are joined together through the frame. The inner circumferential surface of the frame defining the opening and the manifold hole has hydrophobicity with a water contact angle of 100° or more.

2. The water electrolysis chamber according to claim 1, wherein, The inner circumferential surface of the frame is provided with a concave-convex shape to enhance the hydrophobicity.

3. The water electrolysis chamber according to claim 1 or 2, wherein, A hydrophobic layer is provided on the inner circumferential surface of the frame to provide the hydrophobicity.

4. The water electrolysis chamber according to claim 3, wherein, The hydrophobic layer contains a substance with a needle-like crystal structure.

5. The water electrolysis chamber according to claim 3, wherein, The hydrophobic layer is composed of fluorinated resin or silicone resin.

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