Electrolytic cells and electrolytic devices

Abstract

An electrolytic cell according to the present disclosure comprises: a first separator; a second separator; an ion exchange membrane which is disposed between the first separator and the second separator and has a hydroxide ion conductivity; a negative electrode disposed between the first separator and the ion exchange membrane; and a positive electrode disposed between the second separator and the ion exchange membrane. When viewed in a first direction in which the ion exchange membrane, the negative electrode, and the positive electrode overlap, the area of the positive electrode is larger than the area of the negative electrode.

Description

Technical Field

[0001] The present disclosure relates to an electrolytic cell and an electrolysis apparatus. This application claims priority to Japanese Patent Application No. 2022-90936 filed on June 3, 2022, the content of which is incorporated herein by reference.

Background Art

[0002] Patent Document 1 discloses a membrane electrode assembly used in PEM (Polymer Electrolyte Membrane) type water electrolysis. In order to improve the pressure stability and airtightness at a high differential pressure, the first gas diffusion layer disposed on the front side of the ion conductive membrane has a smaller area than the ion conductive membrane, and the second gas diffusion layer disposed on the back side of the ion conductive membrane has the same area as the ion conductive membrane (half coextensive design).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, as deterioration during the use of an electrolytic cell, the deterioration of the anode progresses more significantly than that of the cathode, and as a result, the performance of the electrolytic cell may decrease.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide an electrolytic cell and an electrolysis apparatus capable of improving performance.

Means for Solving the Problems

[0006] To solve the above problems, the electrolytic cell according to this disclosure comprises a first separator, a second separator, an ion exchange membrane which is an anion exchange membrane having hydroxide ion conductivity and disposed between the first separator and the second separator, a cathode disposed between the first separator and the ion exchange membrane, and an anode disposed between the second separator and the ion exchange membrane. When viewed in a first direction in which the ion exchange membrane, the cathode, and the anode overlap, the area of ​​the anode is larger than the area of ​​the cathode. The first separator and the second separator are not in contact with the ion exchange membrane.

[0007] To solve the above problems, the electrolytic apparatus according to this disclosure comprises an electrolytic cell, an electrolyte supply unit for supplying an electrolyte to the electrolytic cell, and a power supply unit for applying a voltage to the electrolytic cell. The electrolytic cell comprises a first separator, a second separator, an ion exchange membrane which is an anion exchange membrane having hydroxide ion conductivity and disposed between the first separator and the second separator, a cathode disposed between the first separator and the ion exchange membrane, and an anode disposed between the second separator and the ion exchange membrane. When viewed in a first direction in which the ion exchange membrane, the cathode, and the anode overlap, the area of ​​the anode is larger than the area of ​​the cathode. The first separator and the second separator are not in contact with the ion exchange membrane. [Effects of the Invention]

[0008] The electrolytic cell and electrolytic apparatus of this disclosure can be used to improve performance. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the overall configuration of the electrolytic apparatus according to the first embodiment of this disclosure. [Figure 2] This is a schematic cross-sectional view showing an electrolytic cell according to the first embodiment of the present disclosure. [Figure 3] This is an exploded perspective view showing an electrolytic cell according to a first embodiment of the present disclosure. [Figure 4] This is a cross-sectional view showing an electrolytic cell according to a first embodiment of the present disclosure. [Figure 5]This is a diagram illustrating the operation of the electrolytic cell of the first embodiment of this disclosure. [Figure 6] This is a diagram illustrating the operation of the electrolytic cell of the first embodiment of this disclosure. [Figure 7] This is a cross-sectional view showing an electrolytic cell according to a second embodiment of the present disclosure. [Figure 8] This table shows the results of examining the state of anode degradation after a predetermined time has elapsed in multiple electrolytic cell test specimens using the electrolytic apparatus of the first embodiment of this disclosure. [Modes for carrying out the invention]

[0010] Hereinafter, electrolytic cells and electrolytic devices of embodiments of the present disclosure will be described with reference to the drawings. In the following description, components having the same or similar function will be denoted by the same reference numerals. In the present disclosure, “opposing” means that two components overlap when viewed in a certain direction, and may include cases where another component (e.g., another layer) exists between the two components.

[0011] First, referring to Figure 4, the Z, X, and Y directions are defined. The Z direction is the direction from the first separator 41 to the second separator 42, which will be described later. The X direction is the direction that intersects (for example, is orthogonal to) the Z direction, and is the direction from the central part C of the ion exchange membrane 51, which will be described later, to one end of the ion exchange membrane 51. The Y direction is the direction that intersects (for example, is orthogonal to) the Z and X directions, and is, for example, the depth direction of the paper in Figure 4. In this disclosure, "area" means the area as viewed in the Z direction (i.e., the area extending in the X and Y directions). Also in this disclosure, "external dimensions" means the external dimensions as viewed in the Z direction. In other words, "external dimensions" and "area" may mean substantially the same thing and may be interpreted as appropriate.

[0012] (First Embodiment) <1. Configuration of the electrolytic device> FIG. 1 is a schematic configuration diagram showing the overall configuration of the electrolysis device 1 of the first embodiment. The electrolysis device 1 is, for example, a device that generates hydrogen by electrolyzing water contained in an electrolytic solution. The electrolysis device 1 is, for example, an anion exchange membrane (AEM) type electrolysis device. However, the electrolysis device 1 is not limited to the above example, and may be a different type of electrolysis device such as a device that electrolytically reduces carbon dioxide.

[0013] The electrolysis device 1 includes, for example, an electrolytic cell stack 10, an electrolytic solution supply unit 20, and a power supply unit 30.

[0014] (Electrolytic Cell Stack) The electrolytic cell stack 10 is an aggregate of a plurality of electrolytic cells 11. For example, the electrolytic cell stack 10 is formed by arranging a plurality of electrolytic cells 11 in one direction. Each electrolytic cell 11 includes a cathode chamber Sa and an anode chamber Sb. The electrolytic cell 11 will be described in detail later.

[0015] (Electrolytic Solution Supply Unit) The electrolytic solution supply unit 20 is a supply unit that supplies an electrolytic solution to each electrolytic cell 11. The electrolytic solution is, for example, pure water or an alkaline aqueous solution. The electrolytic solution supply unit 20 includes a cathode-side supply unit 20a and an anode-side supply unit 20b.

[0016] The cathode-side supply unit 20a is a supply unit that supplies an electrolytic solution to the cathode chamber Sa of each electrolytic cell 11. The cathode-side supply unit 20a includes, for example, a hydrogen gas-liquid separation device 21, a first pump 22, a hydrogen recovery unit 23, a first electrolytic solution supply unit 24, and piping lines L1, L2.

[0017] The hydrogen gas-liquid separation device 21 stores the electrolytic solution. The supply port of the hydrogen gas-liquid separation device 21 is connected to the cathode chamber Sa of the electrolytic cell 11 via the piping line L1. The first pump 22 is provided in the middle of the piping line L1 and sends the electrolytic solution stored in the hydrogen gas-liquid separation device 21 toward the cathode chamber Sa of the electrolytic cell 11.

[0018] The return port of the hydrogen vapor-liquid separator 21 is connected to the cathode chamber Sa of the electrolytic cell 11 via piping line L2. Electrolyte containing hydrogen generated in the electrolytic cell 11 flows into the hydrogen vapor-liquid separator 21 from the electrolytic cell 11. The hydrogen vapor-liquid separator 21 has a vapor-liquid separation unit that separates the hydrogen contained in the electrolyte. The hydrogen separated from the electrolyte by the hydrogen vapor-liquid separator 21 is recovered by the hydrogen recovery unit 23. Electrolyte is replenished into the hydrogen vapor-liquid separator 21 from the first electrolyte supply unit 24.

[0019] On the other hand, the anode-side supply unit 20b is a supply unit that supplies electrolyte to the anode chamber Sb of each electrolytic cell 11. The anode-side supply unit 20b includes, for example, an oxygen vapor-liquid separator 26, a second pump 27, an oxygen recovery unit 28, a second electrolyte supply unit 29, and piping lines L3 and L4.

[0020] The oxygen-gas-liquid separator 26 stores the electrolyte. The supply port of the oxygen-gas-liquid separator 26 is connected to the anode chamber Sb of the electrolytic cell 11 via the piping line L3. The second pump 27 is installed in the middle of the piping line L3 and sends the electrolyte stored in the oxygen-gas-liquid separator 26 towards the anode chamber Sb of the electrolytic cell 11.

[0021] The return port of the oxygen-gas-liquid separator 26 is connected to the anode chamber Sb of the electrolytic cell 11 via piping line L4. Electrolyte containing oxygen generated in the electrolytic cell 11 flows into the oxygen-gas-liquid separator 26 from the electrolytic cell 11. The oxygen-gas-liquid separator 26 has a gas-liquid separation unit that separates the oxygen contained in the electrolyte. The oxygen separated from the electrolyte by the oxygen-gas-liquid separator 26 is recovered by the oxygen recovery unit 28. Electrolyte is replenished into the oxygen-gas-liquid separator 26 from the second electrolyte supply unit 29.

[0022] (Power supply part) The power supply unit 30 is a DC power supply device that applies voltage to the electrolytic cell 11. The power supply unit 30 applies the DC voltage necessary for the electrolysis of the electrolyte between the anode and cathode of the electrolytic cell 11.

[0023] <2. Configuration of the electrolytic cell> <2.1 Basic Structure of Electrolytic Cells> Next, we will explain the electrolytic cell 11 in detail. Figure 2 is a schematic cross-sectional view of the electrolytic cell 11. The electrolytic cell 11 includes, for example, a first separator 41, a second separator 42, and a membrane electrode assembly 43.

[0024] (First separator) The first separator 41 is a component that defines one side of the internal space S of the electrolytic cell 11. The internal space S is a space that includes the cathode chamber Sa and the anode chamber Sb, which will be described later. The first separator 41 is, for example, a rectangular plate and is made of a metal material. The first separator 41 is subjected to a negative voltage from the power supply unit 30, for example, via the first current collector 61 (see Figure 3), which will be described later.

[0025] The first separator 41 has a first end 41e1 (e.g., a lower end) and a second end 41e2 (e.g., an upper end) located on the opposite side of the first end 41e1. The piping line L1 described above is connected to the first end 41e1 of the first separator 41. The piping line L2 described above is connected to the second end 41e2 of the first separator 41. The first separator 41 has a first inner surface 41a facing the cathode chamber Sa, which will be described later. A first flow path FP1 is formed in the first inner surface 41a through which the electrolyte supplied from the piping line L1 flows. The first flow path FP1 is, for example, a groove provided in the first inner surface 41a. The electrolyte that has flowed through the first flow path FP1 is discharged to the outside of the electrolytic cell 11 through the piping line L2. Note that the structures shown in Figure 2 (e.g., flow path structures) are merely examples and do not limit the content of this embodiment. For example, various flow path structures can be used depending on the size and purpose of the device and the operating environment. This also applies to each structure shown in the other diagrams.

[0026] (Second separator) The second separator 42 is positioned with an internal space S between it and at least a portion of the first separator 41, and is a member that defines the other surface of the internal space S. The second separator 42 is, for example, a rectangular plate and is made of a metal material. A positive voltage is applied to the second separator 42 from the power supply unit 30 via the second current collector 62 (see Figure 3), which will be described later. The first separator 41 and the second separator 42, which are included in the same electrolytic cell 11, form the electrolytic cell 40 of the electrolytic cell 11 as a pair of separators.

[0027] The second separator 42 has a first end 42e1 (e.g., a lower end) and a second end 42e2 (e.g., an upper end) located on the opposite side of the first end 42e1. The piping line L3 described above is connected to the first end 42e1 of the second separator 42. The piping line L4 described above is connected to the second end 42e2 of the second separator 42. The second separator 42 has a second inner surface 42a facing the anode chamber Sb, which will be described later. A second flow path FP2 is formed in the second inner surface 42a through which the electrolyte supplied from the piping line L3 flows. The second flow path FP2 is, for example, a groove provided in the second inner surface 42a. The electrolyte that has flowed through the second flow path FP2 is discharged to the outside of the electrolytic cell 11 through the piping line L4.

[0028] For the sake of explanation, this description describes a configuration in which the first inner surface 41a of the first separator 41 has a channel groove (first channel FP1), and the second inner surface 42a of the second separator 42 has a channel groove (second channel FP2). However, for example, the first separator 41 of the electrolytic cell 11 included in the electrolytic cell stack 10 (see Figure 1) may be a bipolar plate having a similar channel groove (first channel FP1, shown as a dashed line in Figure 2) on the surface 41b opposite to the first inner surface 41a, in addition to the first inner surface 41a. Similarly, the second separator 42 of the electrolytic cell 11 included in the electrolytic cell stack 10 may be a bipolar plate having a similar channel groove (second channel FP2, shown as a dashed line in Figure 2) on the surface 42b opposite to the second inner surface 42a, in addition to the second inner surface 42a. The channel grooves provided on both sides of the first separator 41 may differ in shape and arrangement from one another. Furthermore, the flow channel grooves provided on both sides of the second separator 42 may differ in shape and arrangement from one another.

[0029] The membrane electrode assembly (MEA) 43 is a structure assembled from an ion exchange membrane, a catalyst, and a power supply. The membrane electrode assembly 43 is positioned between a first separator 41 and a second separator 42 and is located in the internal space S. The membrane electrode assembly 43 includes, for example, an ion exchange membrane 51, a cathode catalyst layer 52, a cathode power supply 53, an anode catalyst layer 54, and an anode power supply 55.

[0030] (Ion exchange membrane) The ion exchange membrane 51 is a membrane that selectively permeates ions. The ion exchange membrane 51 is, for example, a solid polymer electrolyte membrane. The ion exchange membrane 51 is, for example, a hydroxide ion conductive anion exchange membrane (AEM). However, the ion exchange membrane 51 is not limited to the above example, and may be a different type of ion exchange membrane. The ion exchange membrane 51 is, for example, a rectangular sheet. The external dimensions of the ion exchange membrane 51 are smaller than the external dimensions of the first separator 41 or the second separator 42. The ion exchange membrane 51 is placed between the first separator 41 and the second separator 42 and is located in the internal space S described above. The ion exchange membrane 51 has a first surface 51a facing the first inner surface 41a of the first separator 41, and a second surface 51b located on the opposite side of the first surface 51a and facing the second inner surface 42a of the second separator 42. In the internal space S, a cathode chamber Sa is defined between the first surface 51a of the ion exchange membrane 51 and the first inner surface 41a of the first separator 41. In the internal space S, an anode chamber Sb is defined between the second surface 51b of the ion exchange membrane 51 and the second inner surface 42a of the second separator 42.

[0031] In the cathode chamber Sa, when a voltage is applied to the electrolytic cell 11, the following chemical reaction occurs, and hydrogen is generated from the electrolyte. In this application, "XX is generated" may also include cases where other substances are generated simultaneously with the generation of XX. The hydroxide ions generated in the cathode chamber Sa move from the cathode chamber Sa to the anode chamber Sb by passing through the membrane electrode assembly 43. 2H2O + 2e - →H2+2OH - …(C1)

[0032] In the anode chamber Sb, when a voltage is applied to the electrolytic cell 11, the following chemical reaction occurs, generating oxygen from the electrolyte. 2OH - → 1 / 2O2 + H2O + 2e - …(Case 2)

[0033] As a result, the following chemical reactions occur when considering the electrolytic cell 11 as a whole. H2O→H2+1 / 2O2…(Chem.3)

[0034] (Cathode catalyst layer) The cathode catalyst layer 52 is a layer that promotes the chemical reaction in the cathode chamber Sa described above. The cathode catalyst layer 52 is, for example, a rectangular sheet. In this embodiment, the external dimensions of the cathode catalyst layer 52 are smaller than the external dimensions of the ion exchange membrane 51. The cathode catalyst layer 52 is placed in the cathode chamber Sa and is adjacent to the ion exchange membrane 51. In this application, "adjacent" is not limited to cases where the two members are adjacent independently, but may also include cases where at least a part of one of the two members penetrates the other. For example, a part of the cathode catalyst layer 52 may penetrate the surface of the ion exchange membrane 51. In this embodiment, the cathode catalyst layer 52 is provided on the first surface 51a of the ion exchange membrane 51. For example, the cathode catalyst layer 52 is formed by coating the material of the cathode catalyst layer 52 onto the first surface 51a of the ion exchange membrane 51. The cathode catalyst layer 52 receives a negative voltage from the power supply unit 30 via the first separator 41 and the cathode power supply unit 53, and functions as part of the cathode 47 of the electrolytic cell 11.

[0035] The material of the cathode catalyst layer 52 can be any material that promotes the chemical reaction in the cathode chamber Sa described above, and various materials are available. For example, the cathode catalyst layer 52 contains one or more of nickel, nickel alloy, cerium oxide, lanthanum oxide, or platinum. In this disclosure, "XX oxide" may include other materials other than XX and oxygen. In addition, the cathode catalyst layer 52 may contain other materials such as carbon in addition to the materials described above. "XX" is any material.

[0036] (Cathode feeder) The cathode power supply 53 is an electrical connection that transmits the voltage applied to the first separator 41 to the cathode catalyst layer 52. The cathode power supply 53 is located in the cathode chamber Sa. The cathode power supply 53 is positioned between the first inner surface 41a of the first separator 41 and the cathode catalyst layer 52, and is in contact with both the first inner surface 41a of the first separator 41 and the cathode catalyst layer 52, respectively. At least a portion of the cathode power supply 53 may overlap with at least a portion of at least one of the first separator 41 or the cathode catalyst layer 52. The cathode power supply 53 has a structure through which electrolyte and gas can pass. The cathode power supply 53 is formed from, for example, a metal mesh structure, a sintered body, or fibers. In this embodiment, the external dimensions of the cathode power supply 53 are the same as those of the cathode catalyst layer 52. In this embodiment, the cathode 47 of the electrolytic cell 11 is formed by the cathode catalyst layer 52 and the cathode power supply 53.

[0037] (Anode catalyst layer) The anode catalyst layer 54 is a layer that promotes the chemical reaction in the anode chamber Sb described above. The anode catalyst layer 54 is, for example, a rectangular sheet. In this embodiment, the external dimensions of the anode catalyst layer 54 are smaller than the external dimensions of the ion exchange membrane 51. The anode catalyst layer 54 is placed in the anode chamber Sb and is adjacent to the ion exchange membrane 51. For example, a part of the anode catalyst layer 54 may penetrate the surface of the ion exchange membrane 51. In this embodiment, the anode catalyst layer 54 is provided on the second surface 51b of the ion exchange membrane 51. For example, the anode catalyst layer 54 is formed by coating the material of the anode catalyst layer 54 onto the second surface 51b of the ion exchange membrane 51. A positive voltage is applied to the anode catalyst layer 54 from the power supply unit 30 via the second separator 42 and the anode power supply unit 55, and it functions as part of the anode 48 of the electrolytic cell 11.

[0038] The material of the anode catalyst layer 54 can be any material that promotes the chemical reaction in the anode chamber Sb as described above, and various materials are available. For example, the anode catalyst layer 54 contains one or more of the following: nickel, nickel alloy, nickel oxide, copper oxide, iridium oxide, niobium oxide, lead oxide, or bismuth oxide. As described above, in this disclosure, "XX oxide" may include other materials other than XX and oxygen. For example, "nickel oxide" may include other materials such as iron or cobalt in addition to nickel and oxygen. Similarly, "copper oxide" may include other materials such as cobalt in addition to copper and oxygen. "Iridium oxide" may include other materials such as ruthenium in addition to iridium and oxygen. "Lead oxide" may include other materials such as ruthenium in addition to lead and oxygen. "Bismuth oxide" may include other materials such as ruthenium in addition to bismuth and oxygen.

[0039] (Anode power supply) The anode power supply unit 55 is an electrical connection part that transmits the voltage applied to the second separator 42 to the anode catalyst layer 54. The anode power supply unit 55 is located in the anode chamber Sb. The anode power supply unit 55 is located between the second inner surface 42a of the second separator 42 and the anode catalyst layer 54, and is in contact with the second inner surface 42a of the second separator 42 and the anode catalyst layer 54, respectively. At least a portion of the anode power supply unit 55 may overlap with at least a portion of at least one of the second separator 42 or the anode catalyst layer 54. The anode power supply unit 55 has a structure through which electrolyte and gas can pass. The anode power supply unit 55 is formed from, for example, a metal mesh structure, a sintered body, or fibers. In this embodiment, the external dimensions of the anode power supply unit 55 are the same as the external dimensions of the anode catalyst layer 54. In this embodiment, the anode 48 of the electrolytic cell 11 is formed by the anode catalyst layer 54 and the anode power supply 55.

[0040] Figure 3 is an exploded perspective view showing the electrolytic cell 11. In addition to the configuration described above, the electrolytic cell 11 includes, for example, a first current collector 61, a second current collector 62, a first insulator 63, a second insulator 64, a first insulating material 65, a second insulating material 66, a first end plate 67, and a second end plate 68. For the sake of clarity, the support portion 70 and the sealing portion 80, which will be described later, are not shown in Figure 3.

[0041] (First current collector) The first current collector 61 is an electrical connection part that transmits the negative voltage applied from the power supply unit 30 to the first separator 41. The first current collector 61 is a metal plate member (for example, a copper plate). The first current collector 61 contacts the first separator 41 from the side opposite to the internal space S of the electrolytic cell 11 and is electrically connected to the first separator 41. The negative voltage necessary for electrolysis in the electrolytic cell 11 is applied to the first current collector 61 from the power supply unit 30. The first current collector 61 may be shared by two electrolytic cells 11 that are adjacent to each other in the electrolytic cell stack 10.

[0042] (Second current collector) The second current collector 62 is an electrical connection part that transmits the positive voltage applied from the power supply unit 30 to the second separator 42. The second current collector 62 is a metal plate member (for example, a copper plate). The second current collector 62 contacts the second separator 42 from the side opposite to the internal space S of the electrolytic cell 11 and is electrically connected to the second separator 42. The positive voltage necessary for electrolysis in the electrolytic cell 11 is applied to the second current collector 62 from the power supply unit 30. The second current collector 62 may be shared by two electrolytic cells 11 that are adjacent to each other in the electrolytic cell stack 10.

[0043] (First insulator) The first insulator 63 is a member that insulates the outer periphery of the first separator 41 from the outer periphery of the second separator 42. The first insulator 63 is a frame-shaped sheet member that is slightly larger than the outer shape of the cathode catalyst layer 52 and the cathode power supply 53. The first insulator 63 is attached to the first inner surface 41a of the first separator 41 and covers the end of the first inner surface 41a. The material of the first insulator 63 is not particularly limited as long as it is an insulating material, for example, a sheet-like resin such as PTFE (polytetrafluoroethylene).

[0044] (Second insulator) The second insulator 64, like the first insulator 63, is a component that insulates the outer periphery of the first separator 41 from the outer periphery of the second separator 42. The second insulator 64 is a frame-shaped sheet member that is slightly larger than the outer shape of the anode catalyst layer 54 and the anode power supply 55. The second insulator 64 is attached to the second inner surface 42a of the second separator 42 and covers the end of the second inner surface 42a. The material of the second insulator 64 is not particularly limited as long as it is an insulating material, for example, a sheet-like resin such as PTFE. In addition, the first insulator 63 and the second insulator 64 can be used as an integrated insulator.

[0045] (First insulating material) The first insulating material 65 is located between the first current collector 61 and the first end plate 67. The external dimensions of the first insulating material 65 are, for example, the same as or larger than the external dimensions of the first current collector 61.

[0046] (Second insulating material) The second insulating material 66 is located between the second current collector 62 and the second end plate 68. The external dimensions of the second insulating material 66 are, for example, the same as or larger than the external dimensions of the second current collector 62.

[0047] (First end plate) The first end plate 67 is located on the opposite side of the internal space S of the electrolytic cell 11 from the first insulating material 65. The external dimensions of the first end plate 67 are, for example, larger than the external dimensions of the first insulating material 65.

[0048] (Second end plate) The second end plate 68 is located on the opposite side of the internal space S of the electrolytic cell 11 from the second insulating material 66. The external dimensions of the second end plate 68 are, for example, larger than the external dimensions of the second insulating material 66.

[0049] Note that the electrolytic cell 11 is not limited to the configuration described above. For example, when multiple electrolytic cells 11 are arranged side by side in an electrolytic cell stack 10, two adjacent electrolytic cells 11 may share a bipolar plate, either a first separator 41 or a second separator 42. In this case, a current collector (first current collector 61 or second current collector 62), an insulator (first insulator 63 or second insulator 64), an insulating material (first insulating material 65 or second insulating material 66), or an end plate (first end plate 67 or second end plate 68) may not be present between the two adjacent electrolytic cells 11.

[0050] <2.2 Structure of the outer periphery of the electrolytic cell> Figure 4 is a cross-sectional view showing the electrolytic cell 11. In this embodiment, the external dimensions of the ion exchange membrane 51 are larger than the external dimensions of the cathode catalyst layer 52 and the cathode power supply 53, respectively. In other words, the area of ​​the ion exchange membrane 51 is larger than the area of ​​the cathode catalyst layer 52 and the cathode power supply 53, respectively. The ion exchange membrane 51 protrudes outward (towards the outer periphery) from the cathode catalyst layer 52 and the cathode power supply 53 in a direction perpendicular to the thickness direction (Z direction) of the membrane electrode assembly 43 (e.g., the X or Y direction). In this disclosure, "outward" or "outer periphery" means the side of the ion exchange membrane 51 away from the central part C in a direction perpendicular to the thickness direction (Z direction) of the membrane electrode assembly 43 (e.g., the X or Y direction).

[0051] Similarly, the external dimensions of the ion exchange membrane 51 are larger than those of the anode catalyst layer 54 and the anode power supply 55. In other words, when viewed in the thickness direction (Z direction) of the membrane electrode assembly 43, the area of ​​the ion exchange membrane 51 is larger than that of the anode catalyst layer 54 and the anode power supply 55. The ion exchange membrane 51 protrudes outward from the anode catalyst layer 54 and the anode power supply 55 in a direction perpendicular to the thickness direction (Z direction) of the membrane electrode assembly 43 (for example, the X or Y direction).

[0052] As shown in Figure 4, the electrolytic cell 11 includes, for example, a support portion 70 and a sealing portion 80. The support portion 70 is a member that supports the membrane electrode assembly 43 inside the electrolytic cell 11. The sealing portion 80 is a member that closes the internal space S between the first separator 41 and the second separator 42. These will be described below.

[0053] (Support part) The support portion 70 is positioned between the first separator 41 and the second separator 42. The support portion 70 is located inside (on the inner circumference side) of the outer edge portion 51e of the ion exchange membrane 51 and supports the ion exchange membrane 51. In this disclosure, "outer edge portion" means the edge portion of the ion exchange membrane 51 that is away from the central portion C in a direction perpendicular to the thickness direction (Z direction) of the membrane electrode assembly 43 (for example, the X direction or Y direction). Also in this disclosure, "inside" or "inner circumference side" means the side that is inside (closer to the central portion C) when viewed from the central portion C of the ion exchange membrane 51. In this embodiment, the support portion 70 includes, for example, a first support portion 71 and a second support portion 72.

[0054] (1st support part) The first support portion 71 is a support portion on the cathode side. The first support portion 71 is positioned between the first inner surface 41a of the first separator 41 and the first surface 51a of the ion exchange membrane 51. The first support portion 71 is located inside (on the inner circumference side) of the outer edge 51e of the ion exchange membrane 51. The first support portion 71 is sandwiched between the first inner surface 41a (or first insulator 63) of the first separator 41 and the first surface 51a of the ion exchange membrane 51 at a position outside (on the outer circumference side) of the cathode catalyst layer 52 and the cathode power supply 53, and supports the ion exchange membrane 51 with respect to the first inner surface 41a of the first separator 41. The first support portion 71 is annular (e.g., frame-shaped) along the outer edge 51e of the ion exchange membrane 51, and is formed as an annular shape that is slightly smaller than the outer edge 51e of the ion exchange membrane 51.

[0055] (Second support part) The second support portion 72 is the anode-side support portion. The second support portion 72 is positioned between the second inner surface 42a of the second separator 42 and the second surface 51b of the ion exchange membrane 51. The second support portion 72 is located inside (on the inner circumference side) of the outer edge 51e of the ion exchange membrane 51. The second support portion 72 is sandwiched between the second inner surface 42a of the second separator 42 and the second surface 51b of the ion exchange membrane 51 at a position outside (on the outer circumference side) of the anode catalyst layer 54 and the anode power supply 55, and supports the ion exchange membrane 51 with respect to the second inner surface 42a of the second separator 42. The second support portion 72 is annular (for example, frame-shaped) along the outer edge 51e of the ion exchange membrane 51, and is formed as an annular shape that is slightly smaller than the outer edge 52e of the ion exchange membrane 51.

[0056] (Sealing part) The sealing portion 80 is positioned between the first separator 41 and the second separator 42. The sealing portion 80 is located outside (on the outer periphery side) of the outer edge 51e of the ion exchange membrane 51 and seals the internal space S of the electrolytic cell 11. In this embodiment, the sealing portion 80 includes a first sealing portion 81 and a second sealing portion 82. However, the first sealing portion 81 and the second sealing portion 82 may be formed integrally. That is, the first sealing portion 81 and the second sealing portion 82 may be a single component. Furthermore, the sealing portion 80 may be formed integrally with at least one of the first insulator 63 and the second insulator 64 described above.

[0057] (First sealing section) The first sealing portion 81 is the sealing portion on the cathode side. The first sealing portion 81 is located outside (on the outer periphery side) of the outer edge 51e of the ion exchange membrane 51. The first sealing portion 81 is sandwiched between the first inner surface 41a of the first separator 41 and the second sealing portion 82, sealing a part of the outer periphery side of the internal space S. The first sealing portion 81 is annular (for example, frame-shaped) along the outer edge 51e of the ion exchange membrane 51, and is formed as an annular shape that is slightly larger than the outer edge 51e of the ion exchange membrane 51.

[0058] (Second sealing section) The second sealing portion 82 is the sealing portion on the anode side. The second sealing portion 82 is located outside the outer edge 51e of the ion exchange membrane 51. The second sealing portion 82 is sandwiched between the second inner surface 42a of the second separator 42 and the first sealing portion 81, sealing a part of the outer periphery of the internal space S. The second sealing portion 82 is annular (for example, frame-shaped) along the outer edge 51e of the ion exchange membrane 51, and is formed as an annular shape that is slightly larger than the outer edge 51e of the ion exchange membrane 51.

[0059] <3. Area ratio of cathode and anode> Next, the area ratios of the cathode and anode will be described. In this embodiment, the area of ​​the anode 48 is larger than the area of ​​the cathode 47. For example, the area of ​​the anode catalyst layer 54 is larger than the area of ​​the cathode catalyst layer 52. The area of ​​the anode power supply 55 is larger than the area of ​​the cathode power supply 53.

[0060] In this embodiment, the area ratio of the anode 48 to the cathode 47 is greater than 1.0 and 2.0 or less. From another perspective, in this embodiment, the area ratio of the anode 48 to the cathode 47 is set such that the rate of increase in the overvoltage of the anode 48 due to the progression of degradation is less than twice (more preferably less than 1.5 times) the rate of increase in the overvoltage of the cathode 47. These details will be explained below.

[0061] Figure 5 is a diagram illustrating the operation of the electrolytic cell 11. Figure 5 shows the test results of the current-voltage characteristics in an electrolytic cell of a comparative example in which the anode area and cathode area are the same. In Figure 5, "cycle" refers to a predetermined period of time. As shown in Figure 5, it can be seen that in the electrolytic cell of the comparative example, the overvoltage increases as the number of cycles increases (i.e., as the usage time increases).

[0062] Figure 6 is another diagram illustrating the operation of the electrolytic cell 11. Figure 6 shows the test results of the relationship between the number of cycles and the reaction resistance at the electrodes in the comparative example described above. As shown in Figure 6, the reaction resistance at the anode 48 is larger in absolute value than the reaction resistance at the cathode 47. Furthermore, the rate of increase in the reaction resistance at the anode 48 with increasing degradation is greater than the rate of increase in the reaction resistance at the cathode 47 with increasing degradation. For example, the rate of increase in the reaction resistance at the anode 48 is more than twice that of the reaction resistance at the cathode 47. This is because oxidation reactions occur at the anode 48, so the degradation of the anode 48 is greater than that of the cathode 47.

[0063] Therefore, in this embodiment, the area of ​​the anode 48 is formed to be larger than the area of ​​the cathode 47. With this configuration, the oxidation reaction at the anode 48 can be dispersed over a large area of ​​the anode 48. As a result, it is possible to suppress the deterioration of the anode 48 compared to the cathode 47 compared to the comparative example above. By suppressing the deterioration of the anode 48 compared to the cathode 47, it is possible to suppress the increase in overvoltage, thereby improving the performance and lifespan of the electrolytic cell 11A.

[0064] From another perspective, in the cathode catalyst layer 52 and the anode catalyst layer 54, current leakage occurs at the edges of each catalyst layer, and the current density tends to be high at the edges of the catalyst layers. Therefore, when the areas of the cathode catalyst layer and the anode catalyst layer are the same, as in the comparative example, the edges of each catalyst layer with high current density face each other, and localized degradation tends to be greater at the edges of each catalyst layer.

[0065] On the other hand, in this embodiment, since the anode catalyst layer 54 is larger than the cathode catalyst layer 52, the ends of each catalyst layer, where the current density is high, are offset from each other. As a result, degradation is less likely to occur at the ends of each catalyst layer. From this viewpoint as well, it is possible to suppress the increase in overvoltage, thereby improving the performance and lifespan of the electrolytic cell 11.

[0066] As shown in Figure 6, in the comparative example, the test results of the relationship between the number of cycles and the reaction resistance at the electrodes show that the rate of increase in the reaction resistance at anode 48 is more than twice that at cathode 47. In this embodiment, the area ratio of anode 48 to cathode 47 is set based on the rate of increase in the reaction resistance at anode 48 and the rate of increase in the reaction resistance at cathode 47. That is, the area ratio of anode 48 to cathode 47 is determined by adjusting the difference between the rate of increase in the reaction resistance at anode 48 and the rate of increase in the reaction resistance at cathode 47 to be less than or equal to a predetermined standard (for example, less than 2 times, more preferably less than 1.5 times).

[0067] In this embodiment, the catalyst load on the anode catalyst layer 54 is at least 1 times that of the cathode catalyst layer 52. In this disclosure, "catalyst load" refers to the weight of catalyst per unit area [mg / cm³]. 2 It means ].

[0068] (Second Embodiment) Next, a second embodiment will be described. The second embodiment differs from the first embodiment in that the thickness of the anode catalyst layer 54 is greater than the thickness of the cathode catalyst layer 52. Other than what is described below, the configuration is the same as that of the first embodiment.

[0069] Figure 7 is a cross-sectional view showing the electrolytic cell 11A of the second embodiment. In this embodiment, the area of ​​the anode catalyst layer 54 is larger than the area of ​​the cathode catalyst layer 52, and the thickness of the anode catalyst layer 54 is greater than the thickness of the cathode catalyst layer 52. The amount of catalyst supported in the anode catalyst layer 54 is at least 1 times that of the amount of catalyst supported in the cathode catalyst layer 52.

[0070] In this embodiment, the volume ratio (or catalyst load ratio) of the anode catalyst layer 54 to the cathode catalyst layer 52 is set such that the rate of increase in the overpotential of the anode 48 as degradation progresses is less than twice (more preferably less than 1.5 times) the rate of increase in the overpotential of the cathode 47. In other words, the volume ratio of the anode 48 to the cathode 47 is determined by adjusting the difference between the rate of increase in the reaction resistance at the anode 48 and the rate of increase in the reaction resistance at the cathode 47 to be less than or equal to a predetermined standard (for example, less than twice, more preferably less than 1.5 times).

[0071] This configuration makes it possible to suppress the degradation of the anode 48 compared to the cathode 47. Therefore, it is possible to suppress the increase in overvoltage, thereby improving the performance and lifespan of the electrolytic cell 11B.

[0072] Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure.

[0073] <Note> The electrolytic cells 11, 11A and the electrolytic device 1 described in each embodiment can be understood, for example, as follows.

[0074] (1) The electrolytic cells 11,11A of the first embodiment include a first separator 41, a second separator 42, an ion exchange membrane 51 which is an anion exchange membrane having hydroxide ion conductivity and is disposed between the first separator 41 and the second separator 42, a cathode 47 disposed between the first separator 41 and the ion exchange membrane 51, and an anode 48 disposed between the second separator 42 and the ion exchange membrane 51. When viewed in a first direction (Z direction) where the ion exchange membrane 51, cathode 47, and anode 48 overlap, the area of ​​the anode 48 is larger than the area of ​​the cathode 47. With this configuration, it is possible to suppress the deterioration of the anode 48 being greater than that of the cathode 47 compared to the case where the areas of the cathode 47 and the anode 48 are the same. As a result, it is possible to suppress a large increase in overvoltage at the anode 48, thereby improving the performance and lifespan of the electrolytic cells 11,11A.

[0075] (2) The electrolytic cells 11,11A of the second embodiment are the electrolytic cells 11,11A of the first embodiment, wherein, when viewed in the first direction (Z direction), the area of ​​the ion exchange membrane 51 is larger than the area of ​​the anode 48. With this configuration, a support structure (for example, a support portion 70) for supporting the ion exchange membrane 51 can be provided by utilizing the outer periphery of the ion exchange membrane 51, which is formed to be larger than the anode 48. This makes it possible to provide electrolytic cells 11,11A that can support the ion exchange membrane 51 more stably.

[0076] (3) The electrolytic cells 11,11A of the third embodiment are the electrolytic cells 11,11A of the first or second embodiment, wherein the area ratio of the anode 48 to the cathode 47 when viewed in the first direction (Z direction) is greater than 1.0 and 2.0 or less. With this configuration, it is possible to improve the performance and lifespan of the electrolytic cells 11,11A without making them excessively large. In other words, it is possible to improve the performance and lifespan of the electrolytic cells 11,11A while miniaturizing them.

[0077] (4) The electrolytic cell 11 of the fourth embodiment is one of the electrolytic cells 11 of the first to third embodiments, wherein the area ratio of the anode 48 to the cathode 47 when viewed in the first direction (Z direction) is set such that the rate of increase of the overvoltage of the anode 48 due to the progression of degradation is less than twice the rate of increase of the overvoltage of the cathode 47. With such a configuration, the sizes of the cathode 47 and anode 48 can be set within a suitable range based on the area ratio.

[0078] (5) The electrolytic cell 11A of the fifth embodiment is any one of the electrolytic cells 11, 11A of the first to fourth embodiments, wherein the cathode 47 includes a cathode catalyst layer 52 overlapping with the ion exchange membrane 51 and a cathode power supply 53 disposed between the cathode catalyst layer 52 and the first separator 41, and the anode 48 includes an anode catalyst layer 54 overlapping with the ion exchange membrane 51 and an anode power supply 55 disposed between the anode catalyst layer 54 and the second separator 42, and the catalyst load of the anode catalyst layer 54 is 1 or more than the catalyst load of the cathode catalyst layer 52. With this configuration, it is easier to secure the catalyst load of the anode catalyst layer 54. This makes it possible to suppress the degradation of the anode 48, which is greater than that of the cathode 47, to an even higher level. As a result, further performance improvements and lifespan improvements of the electrolytic cells 11, 11A can be achieved.

[0079] (6) The electrolytic cell 11A of the sixth embodiment is the electrolytic cell 11A of the fifth embodiment, wherein the volume ratio of the anode catalyst layer 54 to the cathode catalyst layer 52 is set such that the rate of increase of the overvoltage of the anode 48 due to the progression of degradation is less than twice the rate of increase of the overvoltage of the cathode 47. With such a configuration, the sizes of the cathode 47 and anode 48 can be set within a suitable range based on the volume ratio.

[0080] (7) The electrolytic cells 11,11A of the seventh embodiment include a first separator 41, a second separator 42, an ion exchange membrane 51 disposed between the first separator 41 and the second separator 42, a cathode 47 disposed between the first separator 41 and the ion exchange membrane 51, and an anode 48 disposed between the second separator 42 and the ion exchange membrane 51. The cathode 47 includes a cathode catalyst layer 52 overlapping the ion exchange membrane 51 and a cathode power supply 53 disposed between the cathode catalyst layer 52 and the first separator 41. The anode 48 includes an anode catalyst layer 54 overlapping the ion exchange membrane 51 and an anode power supply 55 disposed between the anode catalyst layer 54 and the second separator 42. The volume ratio of the anode catalyst layer 54 to the cathode catalyst layer 52 is set such that the rate of increase in the overpotential of the anode 48 as degradation progresses is less than twice that of the overpotential of the cathode 47. With this configuration, the size (catalyst load) of the cathode 47 and anode 48 can be set within a range that is appropriate in terms of volume ratio, based on the degree of degradation. With this configuration, it is possible to suppress the degradation of the anode 48 from being greater than that of the cathode 47, compared to the case where the area of ​​the cathode 47 and the area of ​​the anode 48 are the same. As a result, it is possible to suppress a large increase in overpotential at the anode 48, thereby improving the performance and lifespan of the electrolytic cells 11 and 11A.

[0081] (8) The electrolytic apparatus 1 of the eighth embodiment comprises electrolytic cells 11, 11A as described in any one of the first to seventh embodiments, an electrolyte supply unit 20 that supplies electrolyte to the electrolytic cells 11, 11A, and a power supply unit 30 that applies voltage to the electrolytic cells 11, 11A. With this configuration, the performance and lifespan of the electrolytic apparatus 1 can be improved.

[0082] (9) The electrolytic apparatus 1 of the ninth embodiment is the electrolytic apparatus 1 of the eighth embodiment, comprising an electrolytic cell stack 10 having a plurality of electrolytic cells including electrolytic cells 11, 11A, wherein two adjacent electrolytic cells among the plurality of electrolytic cells share a first separator 41 or a second separator 42 which is a bipolar plate. With this configuration, the performance and lifespan structure of the electrolytic apparatus 1 having the electrolytic cell stack 10 can be improved. [Examples]

[0083] In this disclosure, the electrolytic cell deteriorates in proportion to the time a DC voltage is applied, but the anode deteriorates faster than the cathode. This deterioration leads to an increase in resistance, which manifests as a voltage increase when the current density is kept constant. Below, we manufactured multiple test specimens of electrolytic cells with different anode-to-cathode area ratios and conducted evaluation experiments to investigate the voltage increase at the anode in the electrolytic cell after a predetermined time has elapsed.

[0084] First, as a conventional electrolytic cell for comparison, test specimen A was fabricated in which the area of ​​the anode and the area of ​​the cathode were equal. Furthermore, as electrolytic cells of this disclosure, test specimens B, C, and D were fabricated in which the area of ​​the anode 48 was larger than the area of ​​the cathode 47. The dimensions of the anode and cathode in test specimens A, B, C, and D, and the area ratio of the anode to the cathode are as follows.

[0085] In test specimen A, both the anode and cathode dimensions are 45 mm in height and 45 mm in width; therefore, the area ratio of the anode to the cathode in test specimen A is 1. On the other hand, test specimens B, C, and D are all the same size, with anode dimensions of 50 mm in height and 50 mm in width, and cathode dimensions of 41 mm in height and 41 mm in width; therefore, the area ratio of the anode to the cathode in test specimens B, C, and D is 1.5. The catalyst load ratio is also 1.5.

[0086] In the electrolytic apparatus 1 of the first embodiment, test specimens A, B, C, and D were individually placed at the positions of the electrolytic cell 11 and four energization tests were performed. In each energization test, the power supply unit 30 was driven and a constant current density (2 amperes / cm²) was applied between the anode 48 and cathode 47 of the electrolytic cell 11. 2 A DC voltage was applied to achieve the condition shown above, and the voltage rise of the anode 48 was examined from 100 hours after the start of voltage application to 400 hours after the start of voltage application.

[0087] Figure 8 shows the evaluated values ​​of the voltage rise of anode 48 in test specimens B, C, and D after the above test period. When the voltage rise (difference in voltage value) of test specimen A, which should be used as a comparison target, is set to 100, the voltage rise of test specimen B relative to the voltage rise of test specimen A was 63, the voltage rise of test specimen C relative to the voltage rise of test specimen A was 88, and the voltage rise of test specimen D relative to the voltage rise of test specimen A was 25.

[0088] Compared to test specimen A, in which the dimensions of the anode and cathode are the same and the area ratio of the anode to the cathode is 1, test specimens B, C, and D, in which the dimensions of the anode are larger than the dimensions of the cathode and the area of ​​the anode is larger than the area of ​​the cathode, all show smaller voltage rise values ​​than test specimen A. This indicates that the degradation of test specimens B, C, and D of the electrolytic cell disclosed in this disclosure, in which the area of ​​the anode is larger than the area of ​​the cathode, is less likely to progress than that of test specimen A of a conventional electrolytic cell in which the areas of the anode and cathode are the same. In other words, by adopting the electrolytic cell disclosed in this disclosure, anode degradation is suppressed, and an improvement in the performance of the electrolytic device and a longer lifespan for the device including the electrolytic cell can be expected. [Industrial applicability]

[0089] This disclosure relates to an electrolytic cell and electrolytic device that exhibit slow degradation and are less prone to performance deterioration. [Explanation of Symbols]

[0090] 1...Electrolyzer 10…Electrolytic cell stack 11,11A…Electrolytic cell 20...Electrolyte supply section 30...Power supply section 40...Electrolytic cell 41...First separator 42...Second separator 43...Membrane electrode assembly 47...Cathode 48...Anode 51…Ion exchange membrane 52…Cathode catalyst layer 53...Cathode power supply 54...Anode catalyst layer 55... Anode power supply

Claims

1. First separator and, The second separator and An ion exchange membrane, which is an anion exchange membrane having hydroxide ion conductivity, is disposed between the first separator and the second separator. A cathode is disposed between the first separator and the ion exchange membrane, an anode disposed between the second separator and the ion exchange membrane, Equipped with, When viewed in a first direction in which the ion exchange membrane, the cathode, and the anode overlap, the area of ​​the anode is larger than the area of ​​the cathode. The first separator and the second separator are not in contact with the ion exchange membrane. Electrolytic cell.

2. When viewed in the first direction, the area of ​​the ion exchange membrane is larger than the area of ​​the anode. The electrolytic cell according to claim 1.

3. The area ratio of the anode to the cathode when viewed in the first direction is greater than 1.0 and less than or equal to 2.

0. The electrolytic cell according to claim 1.

4. In electrolysis conditions in which pure water or an alkaline aqueous solution is used as the electrolyte and the current density is 2 amperes / cm² or less, The area ratio of the anode to the cathode when viewed in the first direction is set such that the rate of increase in the overvoltage of the anode due to the progression of degradation is less than twice the rate of increase in the overvoltage of the cathode. The electrolytic cell according to claim 1.

5. The cathode includes a cathode catalyst layer overlapping the ion exchange membrane and a cathode power supply disposed between the cathode catalyst layer and the first separator. The anode includes an anode catalyst layer overlapping the ion exchange membrane and an anode power supply disposed between the anode catalyst layer and the second separator. The amount of catalyst supported in the anode catalyst layer is at least one times the amount of catalyst supported in the cathode catalyst layer. The electrolytic cell according to claim 1.

6. In electrolysis conditions in which pure water or an alkaline aqueous solution is used as the electrolyte and the current density is 2 amperes / cm² or less, The volume ratio of the anode catalyst layer to the cathode catalyst layer is set such that the rate of increase in the anode overvoltage due to the progression of degradation is less than twice the rate of increase in the cathode overvoltage. The electrolytic cell according to claim 5.

7. The cathode includes a cathode catalyst layer overlapping the ion exchange membrane and a cathode power supply disposed between the cathode catalyst layer and the first separator, The anode includes an anode catalyst layer overlapping the ion exchange membrane and an anode power supply disposed between the anode catalyst layer and the second separator. When viewed in the first direction, the area of ​​the anode catalyst layer is larger than the area of ​​the cathode catalyst layer. The thickness of the anode catalyst layer is greater than the thickness of the cathode catalyst layer. The electrolytic cell according to claim 1.

8. An electrolytic cell according to any one of claims 1 to 7, An electrolyte supply unit that supplies electrolyte to the electrolytic cell, A power supply unit that applies voltage to the electrolytic cell, An electrolytic device equipped with this device.

9. The electrolytic cell stack comprises a plurality of electrolytic cells, including the aforementioned electrolytic cell, Among the plurality of electrolytic cells, two adjacent electrolytic cells share the first separator or the second separator, which is a bipolar plate. The electrolytic apparatus according to claim 8.

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