Water electrolysis steril

Abstract

To provide a highly durable water electrolysis cell. [Solution] The water electrolysis cell includes a membrane electrode assembly, a resin frame provided along the periphery of the membrane electrode assembly, and a first separator and a second separator facing each other via the membrane electrode assembly and the frame and joined to each other by the frame. The outer peripheral portion of the membrane electrode assembly extends between a first surface of the frame and the first separator. The surface of the first surface contains an antioxidant.

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a water electrolysis cell.

[0002] Patent Document 1 discloses a water electrolysis cell. In this water electrolysis cell, a membrane electrode assembly is disposed in an opening of a resin frame. An anode separator is bonded to one side of the frame, and a cathode separator is bonded to the other side of the frame. This ensures sealing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-62492 Summary of the Invention [Problem to be solved by the invention]

[0004] Oxygen is generated during water electrolysis. If this oxygen causes oxidation and deterioration of the frame around the periphery of the membrane electrode assembly, the sealing performance cannot be maintained, and the durability of the water electrolysis cell decreases. [Means for solving the problem]

[0005] The water electrolysis cell disclosed herein includes a membrane electrode assembly, a resin frame provided along the periphery of the membrane electrode assembly, and a first separator and a second separator facing each other via the membrane electrode assembly and the frame and joined to each other by the frame. The outer peripheral portion of the membrane electrode assembly extends between a first surface of the frame and the first separator. The surface of the first surface contains an antioxidant.

[0006] The first surface of the frame is located near the membrane electrode assembly, and is the surface where the concentration of generated oxygen is high. By incorporating an antioxidant into this first surface, oxidation degradation of the frame can be effectively suppressed, thereby improving the durability of the water electrolysis cell. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is an exploded perspective view of the water electrolysis cell 1. [Figure 2] FIG. 2 is a partial cross-sectional view taken along line II-II in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] The antioxidant may comprise a chelating agent.

[0009] Metal ions eluted from the membrane electrode assembly may accelerate oxidation degradation of the frame. With the above configuration, the eluted metal ions can be inactivated by the chelating agent, making it possible to more effectively suppress oxidation degradation of the frame.

[0010] The frame may have a second surface located opposite the first surface, and the concentration of the antioxidant may be higher on the first surface than on the second surface.

[0011] The first surface is located closer to the membrane electrode assembly than the second surface. Therefore, the oxygen concentration is likely to be higher on the first surface than on the second surface. According to the above configuration, by making the concentration of the antioxidant higher on the first surface than on the second surface, oxidation degradation of the frame can be more effectively suppressed.

[0012] The membrane electrode assembly may include an electrolyte membrane and a first catalyst layer. The peripheral portions of the electrolyte membrane and the first catalyst layer may extend between the first surface of the frame and the first separator. The first catalyst layer may be in contact with the first surface via the electrolyte membrane. The first catalyst layer and the electrolyte membrane may not be in contact with the second surface.

[0013] The first surface is more likely to have a higher concentration of metal ions eluted from the first catalytic layer than the second surface, which accelerates oxidation degradation. Furthermore, elution of the antioxidant can poison the catalyst in the catalytic layer, so it is preferable to limit the total amount of antioxidant added. With the above configuration, by increasing the antioxidant concentration on the first surface compared to the second surface, it is possible to both prevent deterioration of the first surface, which is more susceptible to oxidation, and suppress catalyst poisoning.

[0014] The frame may have a structure in which a first resin layer, a core layer, and a second resin layer are laminated in the thickness direction. The first resin layer may constitute a first surface. The second resin layer may constitute a second surface. The first resin layer may have a higher concentration of antioxidant than the second resin layer. [Example]

[0015] (Schematic configuration of water electrolysis cell 1) FIG. 1 shows an exploded perspective view of a water electrolysis cell 1. The water electrolysis cell 1 mainly comprises a first separator 10, a second separator 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.

[0016] The frame 50 is made of insulating resin. As shown in Fig. 1, a receiving hole 54 penetrating the frame 50 is provided in the center of the frame 50. The membrane electrode assembly 40 is disposed in the receiving hole 54. In other words, the frame 50 surrounds the periphery of the membrane electrode assembly 40.

[0017] The first separator 10 and the second separator 20 are made of a gas-impermeable conductive material. Examples of separator materials include metal materials such as stainless steel and carbon materials. The first separator 10 and the second separator 20 face each other via the membrane electrode assembly 40 and the frame 50.

[0018] The frame 50 has a plurality of through holes 56 formed around the accommodating hole 54. The first separator 10 has a plurality of through holes 16 formed therein. The second separator 20 has a plurality of through holes 26 formed therein. The through holes 16 and 26 are positioned so as to overlap with the through hole 56. The through holes 16, 56, and 26 are connected to each other to form a first supply channel 61, a first discharge channel 62, a second supply channel 63, a second discharge channel 64, a third supply channel 65, and a drain channel 66. These channels penetrate the water electrolysis cell 1 in the thickness direction. Two or more of the first, second, and third channels may be used.

[0019] (Specific configuration of water electrolysis cell 1) FIG. 2 shows a partial cross-sectional view taken along line II-II in FIG. 1. The membrane electrode assembly 40 includes a hydrogen electrode 41, an oxygen electrode 42, and an electrolyte membrane 43. The electrolyte membrane 43 is a proton-conductive ion-exchange membrane made of 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 connecting catalyst-supporting carbon particles or metal oxides with a resin. Examples of catalysts that can be used include iridium (Ir), ruthenium (Ru), platinum (Pt), and alloys of Pt with other metals (e.g., Pt alloys mixed with cobalt and nickel). The first gas diffusion layer 45 and the second gas diffusion layer 47 are electrically conductive members that are permeable to water and gas.

[0020] The electrolyte membrane 43, the hydrogen electrode 41, and the oxygen electrode 42 have a rectangular shape. The hydrogen electrode 41 is the same size as the electrolyte membrane 43, and the oxygen electrode 42 is smaller than the electrolyte membrane 43. A frame-shaped outer peripheral area PA, where the second catalyst layer 46 is not present, is formed on the upper surface 43u of the electrolyte membrane 43. An adhesive layer 49 is disposed on the upper surface 43u within the outer peripheral area PA. The adhesive layer 49 is a layer formed by applying an adhesive. One example of the adhesive is an ultraviolet-curable adhesive containing an organic solvent.

[0021] The frame body 50 has a three-layer structure in which a first resin layer 51, a core layer 53, and a second resin layer 52 are laminated in the thickness direction. The core layer 53 is a structural member having gas sealing properties and insulating properties. The first resin layer 51 is a layer that adheres to the first separator 10. The second resin layer 52 is a layer that adheres to the second separator 20. The surface of the first resin layer 51 forms a lower surface 51b of the frame body 50. The surface of the second resin layer 52 forms an upper surface 52u of the frame body 50.

[0022] 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 made of a thermoplastic resin such as an acid-modified olefin or polyester. The multilayered frame 50 can be formed by various methods. For example, it may be formed by co-extrusion molding.

[0023] The first resin layer 51 and the second resin layer 52 contain an antioxidant. Various types of antioxidants may be used. For example, the antioxidant may be a chelating agent, or may be a phenol-based, aromatic amine-based, sulfur-based, or phosphorus-based antioxidant. Alternatively, the antioxidant may be a mixture of these components. In this example, an antioxidant containing a chelating agent was used.

[0024] The concentration of the antioxidant is higher in the first resin layer 51 than in the second resin layer 52. That is, the concentration of the antioxidant is higher in the surface of the lower surface 51b than in the surface of the upper surface 52u. In this embodiment, the concentration of the chelating agent is higher in the first resin layer 51 than in the second resin layer 52.

[0025] When viewed from a direction perpendicular to the membrane electrode assembly 40 (z direction), an overlapping area OA is formed where the outer periphery of the membrane electrode assembly 40 overlaps with the inner periphery of the frame 50. In the overlapping area OA, the frame 50 is bonded to the upper surface 43u of the electrolyte membrane 43 via an adhesive layer 49. This results in a structure in which the outer periphery 40e of the membrane electrode assembly 40 extends between the lower surface 51b of the frame 50 and the first separator 10.

[0026] The first catalyst layer 44 is in contact with the lower surface 51b of the frame 50 via the electrolyte membrane 43 and the adhesive layer 49. On the other hand, the first catalyst layer 44 and the electrolyte membrane 43 are not in contact with the upper surface 52u of the frame 50. This results in a structure in which the lower surface 51b is located closer to the membrane electrode assembly 40 than the upper surface 52u.

[0027] (Operation of water electrolysis cell 1) The first separator 10 is provided with a rib 10r. A first flow path 14 is formed by a space between the rib 10r and the membrane electrode assembly 40. The second separator 20 is provided with a rib 20r. A second flow path 24 is formed by a space between the rib 20r and the membrane electrode assembly 40.

[0028] Nitrogen is supplied to the hydrogen electrode 41 via the first supply channel 61 and the first flow path 14. Pure water is supplied to the oxygen electrode 42 via the second supply channel 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 channel 62. Oxygen generated from the oxygen electrode 42 is discharged to the outside via the second flow path 24 and the second discharge channel 64.

[0029] (assignment) Oxygen is generated during water electrolysis. If this oxygen causes oxidative degradation of the frame 50, the sealing performance cannot be maintained, and the durability of the water electrolysis cell 1 will be reduced. Oxidative degradation is particularly noticeable in the first resin layer 51 in the overlapping area OA (see area A1).

[0030] The first reason will be explained. The first resin layer 51 is located closer to the membrane electrode assembly 40 than the second resin layer 52. Therefore, the concentration of generated oxygen is more likely to be higher on the lower surface 51b of the first resin layer 51 than on the upper surface 52u of the second resin layer 52.

[0031] The second reason will be explained. The first catalyst layer 44 is in contact with the lower surface 51b of the first resin layer 51 via the electrolyte membrane 43 and the adhesive layer 49. On the other hand, the first catalyst layer 44 and the electrolyte membrane 43 are not in contact with the upper surface 52u of the second resin layer 52. Therefore, the concentration of metal ions eluted from the first catalyst layer 44 is more likely to be higher on the lower surface 51b than on the upper surface 52u. The eluted metal ions then accelerate oxidative degradation of the first resin layer 51.

[0032] (effect) In the technology of this embodiment, an antioxidant is contained in the first resin layer 51. This makes it possible to suppress oxidative deterioration of the first resin layer 51. This makes it possible to increase the durability of the water electrolysis cell.

[0033] In the technology of this example, a chelating agent is contained in the antioxidant. This allows the eluted metal ions to be inactivated by the chelating agent, making it possible to suppress the effect of metal ions in promoting oxidative degradation.

[0034] The oxygen concentration is likely to be higher on the lower surface 51b of the first resin layer 51 than on the upper surface 52u of the second resin layer 52. In the technology of this embodiment, the concentration of the antioxidant is made higher on the lower surface 51b than on the upper surface 52u. This makes it possible to more effectively suppress oxidative degradation of the first resin layer 51.

[0035] The concentration of metal ions eluted from the first catalytic layer 44 is more likely to be higher on the lower surface 51b than on the upper surface 52u, which accelerates oxidative degradation. Furthermore, elution of the chelating agent may poison the catalysts in the first catalytic layer 44 and the second catalytic layer 46, so it is preferable to limit the total amount of chelating agent added. In the technology of this embodiment, the concentration of the chelating agent is higher on the lower surface 51b than on the upper surface 52u. This effectively suppresses oxidative degradation on the lower surface 51b, which is more susceptible to oxidation, while also limiting the total amount of chelating agent added. This makes it possible to achieve both prevention of oxidative degradation and suppression of catalyst poisoning.

[0036] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility.

[0037] <Modification> The antioxidant may be contained in various forms in the frame body 50. For example, the antioxidant may be contained in the core layer 53. In this case, the antioxidant can be diffused from the core layer 53 to the first resin layer 51 and the second resin layer 52.

[0038] The technology of the present specification can be applied to various structures, for example, a structure in which the membrane electrode assembly 40 and the frame 50 do not overlap each other and no overlapping area OA is formed.

[0039] The frame 50 is not limited to a three-layer structure, and the technology of this specification can also be applied to a frame having a single-layer structure, a two-layer structure, or a structure of four or more layers.

[0040] The concentration of the antioxidant contained in the first resin layer 51 may be the same as that in the second resin layer 52.

[0041] The lower surface 51b is an example of a first surface, and the upper surface 52u is an example of a second surface. [Explanation of symbols]

[0042] 1: Water electrolysis cell 10: First separator 20: Second separator 40: Membrane electrode assembly 40e: Outer periphery 50: Frame 51b: Lower surface

Claims

1. a membrane electrode assembly; a resin frame provided along the periphery of the membrane electrode assembly; a first separator and a second separator that face each other via the membrane electrode assembly and the frame and are joined to each other by the frame; Equipped with an outer peripheral portion of the membrane electrode assembly extends between the first surface of the frame and the first separator; The surface of the first side contains an antioxidant. water electrolysis cell.

2. 2. The water electrolysis cell of claim 1, wherein the antioxidant comprises a chelating agent.

3. The frame body has a second surface located opposite to the first surface, The water electrolysis cell according to claim 1 , wherein a concentration of the antioxidant is higher on the surface of the first side than on the surface of the second side.

4. the membrane electrode assembly includes an electrolyte membrane and a first catalyst layer; an outer peripheral portion of the electrolyte membrane and the first catalyst layer extends between the first surface of the frame and the first separator; the first catalyst layer is in contact with the first surface via the electrolyte membrane, The water electrolysis cell according to claim 3 , wherein the second surface is not in contact with the first catalyst layer or the electrolyte membrane.

5. the frame has a structure in which a first resin layer, a core layer, and a second resin layer are laminated in a thickness direction, the first resin layer constitutes the first surface, the second resin layer constitutes the second surface, The water electrolysis cell according to claim 3 , wherein the first resin layer contains the antioxidant at a higher concentration than the second resin layer.

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