Electrolysis cell and electrolysis device

Abstract

This electrolysis cell comprises: an ion exchange membrane; a power feeder which is provided on the surface of the ion exchange membrane and composed of a plurality of fibers formed in a sheet shape; a binder layer that covers the surface of each of the fibers; and an electrode catalyst layer that contains catalyst particles at least partially protruding from the surface of the binder layer. At least a part of the catalyst particles protrudes from the surface of the binder layer. Consequently, the surface area of the exposed portion of the catalyst particles is increased, and thus the contact area with an electrolyte can be increased.

Description

Electrolytic cell and electrolytic device

[0001] This application claims priority to Japanese Patent Application No. 2024-004512, filed on January 16, 2024, the contents of which are incorporated herein by reference.

[0002] Water electrolysis devices (electrolysis devices) are known as devices for generating hydrogen. In this type of device, an electrolytic cell separated into a cathode chamber and an anode chamber by an ion exchange membrane is filled with water, and water is electrolyzed by supplying electricity to the cathode and anode. In the cathode chamber, hydrogen is generated by a reaction between water and electrons. The hydroxide ions produced by this reaction permeate the ion exchange membrane and reach the anode chamber. In the anode chamber, oxygen and water are generated from these hydroxide ions. By continuing this reaction, large amounts of hydrogen can be obtained.

[0003] On both sides of the ion exchange membrane in the thickness direction, a current supply is disposed between the anode and the cathode. A specific example of a current supply is known from Patent Document 1. In the device disclosed in Patent Document 1, a barrier layer is provided on the surface of the current supply to protect the catalytic material, such as platinum. The barrier layer is formed of a polymer binder and a conductive ceramic material. This is believed to prevent early corrosion of the current supply during the electrolysis reaction.

[0004] Patent No. 6430969

[0005] However, if corrosion resistance is given priority as described above, the contact area between the catalytic material and the electrolyte is reduced by the amount of the barrier layer provided, which poses a problem that the desired electrolysis performance cannot be obtained.

[0006] The present disclosure provides electrolysis cells and electrolysis devices with better electrolysis performance.

[0007] The electrolytic cell according to the present disclosure comprises an ion exchange membrane, a current collector body formed of a plurality of fibers formed into a sheet and disposed on the surface of the ion exchange membrane, a binder layer covering the surface of each of the fibers, and an electrode catalyst layer including catalyst particles at least partially protruding from the surface of the binder layer.

[0008] The electrolysis device according to the present disclosure includes the electrolysis cell described above, an electrolyte solution supply unit that supplies an electrolyte solution to the electrolysis cell, and a power supply unit that applies a voltage to the electrolysis cell.

[0009] According to the present disclosure, it is possible to provide an electrolysis cell and an electrolysis device having better electrolysis performance.

[0010] Fig. 1 is a schematic diagram showing the configuration of an electrolysis device according to an embodiment of the present disclosure; Fig. 2 is a schematic cross-sectional view showing the configuration of an electrolysis cell according to an embodiment of the present disclosure; Fig. 3 is an exploded perspective view showing the configuration of an electrolysis cell according to an embodiment of the present disclosure; Fig. 4 is an enlarged view of fibers in a cathode catalyst layer according to an embodiment of the present disclosure; Fig. 5 is an enlarged view of fibers in an anode catalyst layer according to an embodiment of the present disclosure; Fig. 6 is a schematic diagram showing the state of catalyst particles in an electrode catalyst layer according to an embodiment of the present disclosure; Fig. 7 is a graph showing the relationship between particle size and exposed area of ​​catalyst particles in an electrode catalyst layer according to an embodiment of the present disclosure.

[0011] Electrolytic cells and electrolytic devices according to embodiments of the present disclosure will be described below with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. In the present disclosure, "facing" means that two components overlap when viewed in a certain direction, and may also include the case where another component (e.g., another layer) exists between the two components.

[0012] First, the Z direction, X direction, and Y direction are defined. The Z direction is the direction from a first separator 41 to a second separator 42 (described later). The X direction is a direction intersecting (e.g., perpendicular to) the Z direction and is a direction from a center C of a membrane electrode assembly 43 (described later) toward one end of the membrane electrode assembly 43. The Y direction is a direction intersecting (e.g., perpendicular to) the Z direction and the X direction and is, for example, the depth direction of the paper in FIG. 2 . In this disclosure, "area" means the area when viewed in the Z direction (i.e., the area extending in the X and Y directions). Furthermore, in this disclosure, "external size" means the external size when viewed in the Z direction. In other words, "external size" and "area" may mean substantially the same thing and may be interpreted interchangeably as appropriate.

[0013] 1. Configuration of Electrolysis Device Fig. 1 is a schematic diagram showing the overall configuration of an electrolysis device 1 according to this 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.

[0014] The electrolysis device 1 includes, for example, an electrolysis cell stack 10 , an electrolyte supply unit 20 , and a power supply unit 30 .

[0015] (Electrolytic Cell Stack) The electrolytic cell stack 10 is an assembly of multiple electrolytic cells 11. For example, the electrolytic cell stack 10 is formed by arranging multiple electrolytic cells 11 in one direction. Each electrolytic cell 11 includes a cathode chamber Sa and an anode chamber Sb. The electrolytic cells 11 will be described in detail later.

[0016] (Electrolyte Solution Supply Unit) The electrolyte solution supply unit 20 is a supply unit that supplies an electrolyte solution to each electrolytic cell 11. The electrolyte solution is, for example, pure water or an alkaline aqueous solution. The electrolyte solution supply unit 20 includes a cathode side supply unit 20a and an anode side supply unit 20b.

[0017] The cathode side supply unit 20a is a supply unit that supplies the 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 separator 21, a first pump 22, a hydrogen recovery unit 23, a first electrolytic solution supply unit 24, and piping lines L1 and L2.

[0018] The hydrogen-gas-liquid separator 21 stores the electrolytic solution. A supply port of the hydrogen-gas-liquid separator 21 is connected to the cathode chamber Sa of the electrolytic cell 11 via a piping line L1. A first pump 22 is provided in the piping line L1 and sends the electrolytic solution stored in the hydrogen-gas-liquid separator 21 toward the cathode chamber Sa of the electrolytic cell 11.

[0019] A return port of the hydrogen-gas-liquid separator 21 is connected to the cathode chamber Sa of the electrolytic cell 11 via a piping line L2. An electrolytic solution containing hydrogen produced in the electrolytic cell 11 flows into the hydrogen-gas-liquid separator 21 from the electrolytic cell 11. The hydrogen-gas-liquid separator 21 has a gas-liquid separation unit that separates the hydrogen contained in the electrolytic solution. The hydrogen separated from the electrolytic solution by the hydrogen-gas-liquid separator 21 is recovered by a hydrogen recovery unit 23. The hydrogen-gas-liquid separator 21 is replenished with electrolytic solution from a first electrolytic solution supply unit 24.

[0020] On the other hand, the anode side supply unit 20b is a supply unit that supplies the electrolytic solution to the anode chamber Sb of each electrolytic cell 11. The anode side supply unit 20b includes, for example, an oxygen gas-liquid separator 26, a second pump 27, an oxygen recovery unit 28, a second electrolytic solution supply unit 29, and piping lines L3 and L4.

[0021] The oxygen-gas-liquid separator 26 stores the electrolytic solution. A supply port of the oxygen-gas-liquid separator 26 is connected to the anode chamber Sb of the electrolytic cell 11 via a piping line L3. A second pump 27 is provided in the piping line L3 and sends the electrolytic solution stored in the oxygen-gas-liquid separator 26 toward the anode chamber Sb of the electrolytic cell 11.

[0022] A return port of the oxygen-gas-liquid separator 26 is connected to the anode chamber Sb of the electrolytic cell 11 via a piping line L4. The oxygen-containing electrolytic solution produced 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 electrolytic solution. The oxygen separated from the electrolytic solution by the oxygen-gas-liquid separator 26 is recovered by an oxygen recovery unit 28. The oxygen-gas-liquid separator 26 is replenished with electrolytic solution from a second electrolytic solution supply unit 29.

[0023] (Power Supply Unit) The power supply unit 30 is a DC power supply device that applies a voltage to the electrolytic cell 11. The power supply unit 30 applies a DC voltage required for electrolysis of the electrolyte between the anode and cathode of the electrolytic cell 11.

[0024] 2. Configuration of Electrolytic Cell 2.1 Basic Structure of Electrolytic Cell Next, the electrolytic cell 11 will be described in detail. Fig. 2 is a cross-sectional view schematically showing 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.

[0025] (First Separator) The first separator 41 is a member that defines one side of the internal space S of the electrolysis cell 11. The internal space S is a space that includes a cathode chamber Sa and an anode chamber Sb, which will be described later. The first separator 41 has, for example, a rectangular plate shape and is made of a metal member. A negative voltage is applied to the first separator 41 from the power supply unit 30, for example, via a first current collector 61 (see FIG. 3), which will be described later.

[0026] 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 opposite the first end 41e1. The above-mentioned piping line L1 is connected to the first end 41e1 of the first separator 41. The above-mentioned piping line L2 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 described below. The first inner surface 41a is formed with a first flow path FP1 through which the electrolytic solution 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 electrolytic solution 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 (e.g., flow path structure) shown in FIG. 2 are merely examples and do not limit the content of this embodiment. For example, various flow channel structures can be used depending on the size, purpose, and usage environment of the device, and this also applies to the structures shown in the other figures.

[0027] (Second Separator) The second separator 42 is disposed with an internal space S between it and at least a part of the first separator 41, and is a member that defines the other side of the internal space S. The second separator 42 is, for example, a rectangular plate and is made of a metal member. A positive voltage is applied to the second separator 42 from the power supply unit 30 via a second current collector 62 (see FIG. 3 ), which will be described later. The first separator 41 and the second separator 42 included in the same electrolytic cell 11 form, as a pair of separators, the electrolytic cell 40 of the electrolytic cell 11.

[0028] 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 opposite the first end 42e1. The above-mentioned piping line L3 is connected to the first end 42e1 of the second separator 42. The above-mentioned piping line L4 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 described below. A second flow path FP2 is formed on the second inner surface 42a, through which the electrolytic solution 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 electrolytic solution that has flowed through the second flow path FP2 is discharged to the outside of the electrolytic cell 11 via the piping line L4.

[0029] For ease of explanation, the configuration described herein is one in which the first inner surface 41a of the first separator 41 has a flow path groove (first flow path FP1), and the second inner surface 42a of the second separator 42 has a flow path groove (second flow path FP2). However, for example, the first separator 41 of the electrolysis cell 11 included in the electrolysis cell stack 10 (see FIG. 1 ) may be a bipolar plate having a similar flow path groove (first flow path FP1, shown by a two-dot chain line in FIG. 2 ) on the surface 41b opposite the first inner surface 41a in addition to the first inner surface 41a. Furthermore, the second separator 42 of the electrolysis cell 11 included in the electrolysis cell stack 10 may be a bipolar plate having a similar flow path groove (second flow path FP2, shown by a two-dot chain line in FIG. 2 ) on the surface 42b opposite the second inner surface 42a in addition to the second inner surface 42a. The flow path grooves provided on both surfaces of the first separator 41 may have different shapes and arrangements. Furthermore, the flow path grooves provided on both sides of the second separator 42 may have different shapes and arrangements.

[0030] The membrane electrode assembly (MEA) 43 is a structure in which an ion exchange membrane, a catalyst, and a power supply are assembled. The membrane electrode assembly 43 is disposed between the first separator 41 and the second separator 42, and is located in the internal space S. The membrane electrode assembly 43 includes, for example, a first ion exchange membrane 51, a second ion exchange membrane 52, an ionomer layer 53, a cathode catalyst layer 54, and an anode catalyst layer 56.

[0031] (First Ion Exchange Membrane) The first ion exchange membrane 51 is a membrane that selectively transmits ions. The first ion exchange membrane 51 is, for example, a solid polymer electrolyte membrane. The first ion exchange membrane 51 is, for example, an anion exchange membrane (AEM) that is hydroxide ion conductive. However, the first ion exchange membrane 51 is not limited to the above example and may be an ion exchange membrane of a different type from the above example. The first ion exchange membrane 51 is, for example, a rectangular sheet. The outer size of the first ion exchange membrane 51 is smaller than the outer size of the first separator 41 or the second separator 42. The first ion exchange membrane 51 is disposed between the first separator 41 and the second separator 42 and is located in the internal space S described above. The first 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 from the first surface 51a. In the internal space S, a cathode chamber Sa is defined between the first surface 51 a of the first ion exchange membrane 51 and the first inner surface 41 a of the first separator 41 .

[0032] In the cathode chamber Sa, when a voltage is applied to the electrolytic cell 11, the following chemical reaction occurs, producing hydrogen from the electrolytic solution. Note that in this application, "XX is produced" may also include cases where other substances are produced simultaneously with the production of XX. The hydroxide ions produced in the cathode chamber Sa pass through the membrane electrode assembly 43 and move from the cathode chamber Sa to the anode chamber Sb. 2H2O + 2e- → H2 + 2OH- ... (Chemical Formula 1)

[0033] (Second Ion Exchange Membrane) The second ion exchange membrane 52 is a membrane that selectively transmits ions. The second ion exchange membrane 52 is, for example, a solid polymer electrolyte membrane. The second ion exchange membrane 52 is, for example, an anion exchange membrane with hydroxide ion conductivity. However, the second ion exchange membrane 52 is not limited to the above example and may be an ion exchange membrane of a type different from the above example. The second ion exchange membrane 52 is, for example, in the form of a rectangular sheet. The outer size of the second ion exchange membrane 52 is smaller than the outer size of the first separator 41 or the second separator 42. For example, the outer size of the second ion exchange membrane 52 is the same as the outer size of the first ion exchange membrane 51. The second ion exchange membrane 52 is disposed between the first separator 41 and the second separator 42 and is located in the internal space S described above. The second ion exchange membrane 52 has a third surface 52a facing the second inner surface 42a of the second separator 42 and a fourth surface 52b located on the opposite side to the third surface 52a. In the internal space S, an anode chamber Sb is defined between the third surface 52a of the second ion exchange membrane 52 and the second inner surface 42a of the second separator 42.

[0034] In the anode chamber Sb, when a voltage is applied to the electrolytic cell 11, the following chemical reaction occurs, producing oxygen from the electrolyte: 2OH- → 1 / 2O2 + H2O + 2e- (Chemical Formula 2)

[0035] As a result, the following chemical reaction occurs in the electrolytic cell 11 as a whole: H2O → H2 + 1 / 2O2 (Chemical Formula 3)

[0036] In this disclosure, ordinal numbers such as "first" and "second" are used in the names of components for the sake of convenience. For example, the names "third" and "fourth" do not imply that the same component is also designated by the names "first" and "second." In this embodiment, the names "third surface 52a" and "fourth surface 52b" of the second ion exchange membrane 52 do not imply that the second ion exchange membrane 52 has a first surface and a second surface. Therefore, the names "third surface 52a" and "fourth surface 52b" may be read as the "first surface 52a" and "second surface 52b" of the second ion exchange membrane 52.

[0037] In this embodiment, the first ion exchange membrane 51 and the second ion exchange membrane 52 are integrated with each other such that the second surface 51b of the first ion exchange membrane 51 faces the fourth surface 52b of the second ion exchange membrane 52. In the present disclosure, the phrase "the first ion exchange membrane 51 and the second ion exchange membrane 52 are integrated" is not limited to the case where the first ion exchange membrane 51 and the second ion exchange membrane 52 are directly bonded to each other, but may also include the case where another layer (for example, an ionomer layer 53 described later) is present between the first ion exchange membrane 51 and the second ion exchange membrane 52.

[0038] The materials of the first ion exchange membrane 51 and the second ion exchange membrane 52 may be the same or different. For example, the materials of the first ion exchange membrane 51 and the second ion exchange membrane 52 are selected as follows. That is, because no oxidation reaction occurs in the cathode chamber Sa, the first ion exchange membrane 51 does not need to have high oxidation resistance. Therefore, for example, a membrane made of a material with higher ionic conductivity than the second ion exchange membrane 52 is used as the first ion exchange membrane 51. On the other hand, because an oxidation reaction occurs in the anode chamber Sb, it is preferable that the second ion exchange membrane 52 have high oxidation resistance. Therefore, for example, a membrane made of a material with higher oxidation resistance than the first ion exchange membrane 51 is used as the second ion exchange membrane 52.

[0039] An example of a "membrane with high ionic conductivity" is a membrane containing a polystyrene-based or tetraphenyl-based composition in the main chain and an imidazolium group or a quaternary ammonium group in the side chain. An example of a "membrane with high oxidation resistance" is a membrane containing a polysulfone-based or bromobutylstyrene-based composition.

[0040] (Ionomer Layer) The ionomer layer 53 is a layer for bonding the first ion exchange membrane 51 and the second ion exchange membrane 52. The ionomer layer 53 is a layer through which hydroxide ions can pass. The ionomer layer 53 is provided between the second surface 51b of the first ion exchange membrane 51 and the fourth surface 52b of the second ion exchange membrane 52. For example, the ionomer layer 53 is provided over the entire second surface 51b of the first ion exchange membrane 51 and the entire fourth surface 52b of the second ion exchange membrane 52. The thickness of the ionomer layer 53 is, for example, 10 nm or more and 10 μm or less. In this embodiment, the first ion exchange membrane 51 and the second ion exchange membrane 52 are integrated via the ionomer layer 53.

[0041] (Cathode Catalyst Layer) The cathode catalyst layer 54 is a layer that promotes the chemical reaction in the cathode chamber Sa. The cathode catalyst layer 54 has, for example, a rectangular sheet shape. In this embodiment, the outer size of the cathode catalyst layer 54 is smaller than the outer size of the first ion exchange membrane 51. The cathode catalyst layer 54 is disposed in the cathode chamber Sa and adjacent to the first ion exchange membrane 51. Note that in this application, the term "adjacent" is not limited to two components being adjacent to each other independently, but may also include a case where at least a portion of one of the two components is embedded in the other. In this embodiment, the cathode catalyst layer 54 is provided on the first surface 51 a of the first ion exchange membrane 51. A negative voltage is applied to the cathode catalyst layer 54 from the power supply unit 30 via the first separator 41, and the cathode catalyst layer 54 functions as part of the cathode 47 of the electrolysis cell 11.

[0042] 4 , the cathode catalyst layer 54 includes a cathode current collector 71, a binder layer 72, and cathode catalyst particles 73. The cathode current collector 71 is an electrical connection part that transmits the voltage applied to the first separator 41 to the cathode catalyst layer 54 itself. The cathode current collector 71 is in the form of a mesh made of, for example, carbon fibers. That is, the sheet-like cathode current collector 71 is formed by entangling a plurality of carbon fibers.

[0043] The surface of each of these carbon fibers is covered with a binder layer 72. The binder layer 72 is a substance for adhering the cathode catalyst particles 73 to the surface of the carbon fiber. Specifically, a fluorine-based resin material is preferably used as the binder layer 72. In particular, polytetrafluoroethylene (PTFE (registered trademark)), fluoroethylene vinyl ether (FEVE), and polyvinylidene fluoride (PVdF) are preferably used. These resin materials are capable of maintaining high levels of adhesion between materials, i.e., bonding strength, over a long period of time. In particular, polyvinylidene fluoride exhibits particularly good bonding strength in an alkaline environment, making it effective when the electrolyte is an alkaline aqueous solution (e.g., a potassium hydroxide aqueous solution).

[0044] The cathode catalyst particles 73 are fixed to the fiber surface of the cathode current collector 71 by the binder layer 72. Specifically, as shown in FIG. 6 , the cathode catalyst particles 73 exist as individual particles or as aggregates of these individual particles. Most of the cathode catalyst particles 73 protrude from the surface of the binder layer 72. In other words, at least a portion of the surface of the granular cathode catalyst particles 73 protrudes further outward than the outer surface of the binder layer 72. As shown in FIG. 6 , when the particle diameter of the cathode catalyst particle 73 is D (radius r), the surface area A of the particle exposed from the binder layer 72 having a thickness t is calculated as A = 2πr(2r - t).

[0045] However, because the actual particle diameter D of the cathode catalyst particles 73 varies with the average particle diameter σ by approximately 1σ / D = 0.1 to 0.4, the total exposed area must be determined by statistical simulation. In other words, because the surface area of ​​the catalyst exposed from the binder layer varies depending on the particle diameter variation, it is necessary to statistically calculate what percentage of the total surface area of ​​the cathode catalyst particles 73 is exposed from the binder film. In the case of a catalyst, 1σ / D varies with the average particle diameter D by approximately 0.1 to 0.4, so an example of the calculation result for the ratio of the surface area of ​​the exposed portion of the cathode catalyst particles 73 to the total surface area (total surface area of ​​the binder layer 72) is shown in FIG. 7 . Specifically, considering the electrolysis performance and lifespan of the cathode catalyst particles 73, it is desirable that the surface area of ​​the cathode catalyst particles 73 exposed from the binder layer 72 be at least 20% to 80% of the total surface area. More desirably, this surface area ratio is 40% to 60%. Most preferably, this surface area percentage is 50%.

[0046] The "average particle size" referred to here is a value obtained by, for example, a laser diffraction particle size distribution measurement method. Specific examples of measuring instruments that employ this type of method include the "SALD series manufactured by Shimadzu Corporation."

[0047] The thickness of the binder layer 72 is preferably 20 to 100% of the average particle size. Furthermore, considering the balance between electrode performance and lifespan, it is desirable to have 40 to 60% of the total surface area in contact with the electrolyte, so the thickness of the binder layer 72 in this case is preferably 40 to 65% of the average particle size.

[0048] When the cathode catalyst particles 73 are aggregates, the index for controlling the exposed area is the same as that for the single particles described above. That is, when the aggregate particle size = D (radius r), the surface area A of the aggregate exposed from the binder layer 72 with thickness t is calculated as A = 2kπr (2r - t), where k is a proportionality constant that is set appropriately depending on the primary particle diameter and aggregate size of the particles.

[0049] The material of the cathode catalyst particles 73 includes one or more of nickel, nickel alloy, cerium oxide, lanthanum oxide, and platinum. Platinum-supported carbon is particularly preferably used as the cathode catalyst particles 73. In this disclosure, "XX oxide" may include other materials in addition to XX and oxygen.

[0050] Note that, when forming the above-described cathode catalyst layer 54, for example, a method is employed in which the cathode power supplier 71 is immersed in a slurry containing the cathode catalyst particles 73 and the substance that forms the binder layer 72. At this time, by adjusting the volume fraction of the substance that forms the cathode catalyst particles 73 and the binder layer 72, it becomes possible to expose the cathode catalyst particles 73 from the surface of the binder layer 72 as described above, and to control the proportion of the surface area of ​​the exposed portion within the above-described numerical range.

[0051] (Anode Catalyst Layer) The anode catalyst layer 56 is a layer that promotes the chemical reaction in the anode chamber Sb. The anode catalyst layer 56 has, for example, a rectangular sheet shape. In this embodiment, the outer size of the anode catalyst layer 56 is smaller than the outer size of the second ion exchange membrane 52. The anode catalyst layer 56 is disposed in the anode chamber Sb and adjacent to the second ion exchange membrane 52. Note that, for example, a portion of the anode catalyst layer 56 may extend into the surface portion of the second ion exchange membrane 52. In this embodiment, the anode catalyst layer 56 is provided on the third surface 52a of the second ion exchange membrane 52. For example, the anode catalyst layer 56 is formed by applying a material for the anode catalyst layer 56 to the third surface 52a of the second ion exchange membrane 52. A positive voltage is applied to the anode catalyst layer 56 from the power supply unit 30 via the second separator 42, and the anode catalyst layer 56 functions as part of the anode 48 of the electrolysis cell 11.

[0052] 5 , the anode catalyst layer 56 includes an anode current collector 81, a binder layer 82, and anode catalyst particles 83. The anode current collector 81 is an electrical connection part that transmits the voltage applied to the second separator 42 to the anode catalyst layer 56 itself. The anode current collector 81 is in the form of a mesh made of, for example, stainless steel fibers. In other words, the sheet-like anode current collector 81 is formed by entangling a plurality of stainless steel fibers.

[0053] The surface of each of these fibers is covered with a binder layer 82. The binder layer 82 is a substance that adheres the anode catalyst particles 83 to the surface of the stainless steel fibers. As with the cathode catalyst layer 54, a fluorine-based resin material is preferably used for the binder layer 82. In particular, polytetrafluoroethylene (PTFE (registered trademark)), fluoroethylene vinyl ether (FEVE), and polyvinylidene fluoride (PVdF) are preferably used. This is because these resin materials can maintain a high level of adhesion between materials, i.e., bonding strength, for a long period of time.

[0054] The anode catalyst particles 83 are fixed to the fiber surface of the anode current collector 81 by the binder layer 82. Specifically, as shown in FIG. 6 , the anode catalyst particles 83 exist as individual particles or as aggregates of these individual particles. Most of the anode catalyst particles 83 protrude from the surface of the binder layer 82. That is, at least a portion of the surface of the granular anode catalyst particles 83 protrudes outward beyond the outer surface of the binder layer 82. The ratio of the surface area of ​​the exposed portion of the anode catalyst particle 83 to the total surface area of ​​the binder layer 82 is preferably the same as the numerical range based on the simulation example of the cathode catalyst particle 73 described above. Furthermore, the method of forming the anode catalyst layer 56 and the method of controlling the exposed area of ​​the anode catalyst particles 83 are also the same as the methods described above for the cathode catalyst layer 54.

[0055] The anode catalyst particles 83 may be made of one or more of 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 in addition to XX and oxygen. For example, "nickel oxide" may include other materials such as iron or cobalt in addition to nickel and oxygen. "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.

[0056] Furthermore, in the above-described cathode catalyst layer 54 and anode catalyst layer 56 (hereinafter collectively referred to as electrode catalyst layer 90), the above-described materials are used as the cathode catalyst particles 73 and anode catalyst particles 83 (hereinafter collectively referred to as catalyst particles 91), and therefore these materials have electronic conductivity. Therefore, the binder layers 72, 82 and the electrode catalyst layer 90 do not contain a conductive additive to supplement electronic conductivity.

[0057] 3 is an exploded perspective view showing the electrolytic cell 11. In addition to the components 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 insulator 65, a second insulator 66, a first end plate 67, and a second end plate 68.

[0058] (First current collector) The first current collector 61 is an electrical connection part that transmits a negative voltage applied from the power supply unit 30 to the first separator 41. The first current collector 61 is a metal plate member (e.g., a copper plate). The first current collector 61 contacts the first separator 41 from the side opposite to the internal space S of the electrolysis cell 11, for example, and is electrically connected to the first separator 41. A negative voltage required for electrolysis in the electrolysis 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 adjacent electrolysis cells 11 in the electrolysis cell stack 10.

[0059] (Second current collector) The second current collector 62 is an electrical connection part that transmits a positive voltage applied from the power supply unit 30 to the second separator 42. The second current collector 62 is a metal plate member (e.g., a copper plate). The second current collector 62 contacts the second separator 42 from the side opposite to the internal space S of the electrolysis cell 11, for example, and is electrically connected to the second separator 42. A positive voltage required for electrolysis in the electrolysis 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 adjacent electrolysis cells 11 in the electrolysis cell stack 10.

[0060] (First insulator) The first insulator 63 is a member that provides insulation between the outer periphery of the first separator 41 and the outer periphery of the second separator 42. The first insulator 63 is attached to the first inner surface 41 a of the first separator 41 and covers the end of the first inner surface 41 a. The material of the first insulator 63 is not particularly limited as long as it is an insulating material, and is, for example, a sheet-like resin such as PTFE (polytetrafluoroethylene).

[0061] (Second Insulator) Similar to the first insulator 63, the second insulator 64 is a member that provides insulation between the outer periphery of the first separator 41 and the outer periphery of the second separator 42. 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, and is, for example, a sheet-like resin such as PTFE. The first insulator 63 and the second insulator 64 may also be used as an integrated insulator.

[0062] (First Insulating Material) The first insulating material 65 is located between the first current collector 61 and the first end plate 67. The outer size of the first insulating material 65 is, for example, the same as or larger than the outer size of the first current collector 61.

[0063] (Second Insulating Material) The second insulating material 66 is located between the second current collector 62 and the second end plate 68. The outer size of the second insulating material 66 is, for example, the same as or larger than the outer size of the second current collector 62.

[0064] (First End Plate) The first end plate 67 is located on the opposite side of the first insulating material 65 with respect to the internal space S of the electrolysis cell 11. The outer size of the first end plate 67 is larger than the outer size of the first insulating material 65, for example.

[0065] (Second End Plate) The second end plate 68 is located on the opposite side of the second insulating material 66 with respect to the internal space S of the electrolysis cell 11. The outer size of the second end plate 68 is larger than the outer size of the second insulating material 66, for example.

[0066] The electrolytic cell 11 is not limited to the configuration described above. For example, when a plurality of electrolytic cells 11 are arranged side by side in the electrolytic cell stack 10, two adjacent electrolytic cells 11 among the plurality of electrolytic cells 11 may share a first separator 41 or a second separator 42, which is a bipolar plate. 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 insulator 65 or second insulator 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.

[0067] (Effects) In the manufacture of electrolytic cells, a method has been proposed in which a layer (barrier layer) is provided on the surface of a solid, non-fibrous current collector to protect a catalytic material such as platinum. The barrier layer is formed of a polymer binder and a conductive ceramic material, etc. This is intended to prevent early corrosion of the current collector during the electrolytic reaction. However, prioritizing corrosion resistance in this way reduces the contact area between the catalytic material and the electrolyte by the amount of the barrier layer, resulting in the problem of not being able to achieve the desired electrolytic performance. To solve this problem, the present embodiment employs the above-described configurations.

[0068] According to the above configuration, at least a portion of the catalyst particles 91 protrudes from the surfaces of the binder layers 72, 82. This increases the surface area of ​​the exposed portions of the catalyst particles 91, thereby increasing the contact area with the electrolyte. This makes it possible to improve the electrolysis performance from the beginning to the end of the reaction. In particular, because the catalyst particles 91 are fixed to each of the fibers of the current feeder via the binder layers 72, 82, the electrolyte penetrates between the fibers, allowing the electrolysis reaction to proceed more stably and efficiently. In this way, the performance of each electrolysis cell 11 is improved, making it possible to reduce the number of electrolysis cells 11 required for the same amount of hydrogen production. As a result, the overall size of the electrolysis device 1 can be reduced, and energy savings can be achieved in the plant.

[0069] According to the above configuration, the surface area of ​​the protruding portions of the catalyst particles 91 is 20% or more and 80% or less of the total surface area of ​​the binder layers 72, 82. This allows for improved electrolysis performance while maintaining the binder layers 72, 82's ability to hold the catalyst particles 91. Conversely, if the surface area of ​​the catalyst particles 91 exposed from the binder layers 72, 82 is small, the catalyst particles 91 cannot contact ions through the electrolytic solution, which could result in a decline in electrolysis performance. According to the above configuration, this possibility can be significantly reduced. Furthermore, because the binder layers 72, 82 themselves have a considerable surface area, the holding force for the catalyst particles 91, and therefore the lifespan, can be extended. This allows the electrolysis cell 11 to continue operating stably for an even longer period of time.

[0070] According to the above configuration, since the catalyst particles 91 have electronic conductivity, there is no need to supplement conductivity with the binder layers 72, 82 and the electrode catalyst layer 90. Therefore, good electrolysis performance can be obtained without incorporating a conductive additive into the binder layers 72, 82 and the electrode catalyst layer 90 as a whole. Therefore, the manufacturing costs and maintenance costs of the device can be reduced by the amount that the conductive additive can be omitted. As a result, the supply price of hydrogen, which is the final product produced by the electrolysis reaction, can be reduced.

[0071] While efforts are being made to improve the electrolysis performance of the electrolysis cell 11, there is also a growing demand for a longer life for the electrode catalyst layer 90 to ensure operability. Therefore, in this embodiment, a fluorine-based resin material is used for the binder layers 72, 82. Fluorine-containing resin materials are known to have stronger adhesive (bonding) strength between objects than other substances. According to the above configuration, the use of a fluorine-containing resin material for the binder layers 72, 82 makes it possible to maintain a state in which the power feeder and the catalyst particles 91 are strongly bonded to each other by the binder layers 72, 82. This prevents deterioration of the electrolysis cell 11 and achieves a longer life. In other words, the electrolysis cell 11 can be used stably for a long period of time without the need for replacement, etc. This significantly reduces the operating costs of the entire device.

[0072] Among fluorine-containing resin materials, polyvinylidene fluoride is known to have particularly high adhesive strength (bonding strength) between objects compared to other fluorine-based resins. According to the above configuration, the binder layers 72, 82 are made of a fluorine-containing resin, which allows the current feeder and the catalyst particles 91 to be strongly bonded to each other via the binder layers 72, 82. In particular, in an alkaline electrolyte environment, the adhesive strength of polyvinylidene fluoride is maintained at an even higher level, making it more advantageous than other materials. This prevents deterioration of the electrolytic cell 11 and extends its lifespan. In other words, the electrolytic cell 11 can be used stably for a long period of time without replacement, etc. This significantly reduces the operating costs of the entire device.

[0073] (Other Embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope that does not deviate from the gist of the present disclosure are also included.

[0074] For example, the materials of the cathode power supply 71 and the anode power supply 81 described in the above embodiment are merely examples, and any substance that is not corroded by hydrogen or oxygen and promotes an oxidation-reduction reaction with the electrolyte can be used as the cathode power supply 71 or the anode power supply 81.

[0075] In the above embodiment, the two ion exchange membranes 120 are bonded together, but the configuration of the ion exchange membrane 120 is not limited to this. As another example, it is also possible to adopt a configuration in which a catalyst layer and a power supply are provided on both sides of a single ion exchange membrane 120.

[0076] <Additional Notes> The electrolytic cell and electrolytic device described in each embodiment can be understood, for example, as follows.

[0077] (1) An electrolytic cell according to a first aspect includes an ion exchange membrane, a current collector formed of a plurality of fibers formed into a sheet and disposed on the surface of the ion exchange membrane, a binder layer covering the surface of each of the fibers, and an electrode catalyst layer including catalyst particles at least partially protruding from the surface of the binder layer.

[0078] According to the above configuration, at least a portion of the catalyst particles 91 protrudes from the surfaces of the binder layers 72, 82. This increases the surface area of ​​the exposed portions of the catalyst particles 91, thereby increasing the contact area with the electrolyte.

[0079] (2) The electrolytic cell according to a second aspect is the electrolytic cell of (1), wherein the surface area of ​​the portion of the catalyst particle that protrudes from the surface of the binder layer is 20% to 80% of the total surface area including the protruding portion and the remaining portion of the binder layer.

[0080] According to the above configuration, the surface area of ​​the protruding portions of the catalyst particles 91 is set to 20% or more and 80% or less of the total surface area of ​​the binder layers 72, 82. This makes it possible to achieve improved electrolysis performance while maintaining the holding force of the binder layers 72, 82 for the catalyst particles 91.

[0081] (3) An electrolytic cell according to a third aspect is the electrolytic cell of (1) or (2), wherein the catalyst particles have electronic conductivity, and the binder layer and the electrode catalyst layer do not contain a conductive additive.

[0082] According to the above configuration, the catalyst particles 91 have electronic conductivity, so there is no need to supplement the conductivity with the binder layers 72, 82 and the electrode catalyst layer 90. Therefore, good electrolysis performance can be obtained without including a conductive additive in the binder layers 72, 82 and the electrode catalyst layer 90 as a whole.

[0083] (4) An electrolytic cell according to a fourth aspect is the electrolytic cell according to any one of (1) to (3), wherein the binder layer is formed of a resin material containing fluorine.

[0084] While efforts are being made to improve the electrolysis performance of the electrolysis cell 11, there is also a growing demand for a longer life for the electrode catalyst layer 90 in order to ensure operability. Therefore, in this embodiment, a fluorine-based resin material is used for the binder layers 72, 82. It is known that fluorine-containing resin materials have a stronger adhesive strength (bonding strength) between objects than other substances. According to the above configuration, the use of a fluorine-containing resin material for the binder layers 72, 82 makes it possible to maintain a state in which the power supply element and the catalyst particles 91 are strongly bonded to each other by the binder layers 72, 82.

[0085] (5) The electrolytic cell according to a fifth aspect is the electrolytic cell of (4), wherein the binder layer is formed of polyvinylidene fluoride.

[0086] Among fluorine-containing resin materials, polyvinylidene fluoride is known to have particularly high adhesive strength (bonding strength) between objects compared to other fluorine-based resins. According to the above configuration, since a fluorine-containing resin material is used for the binder layers 72, 82, it is possible to maintain a state in which the power supply element and the catalyst particles 91 are strongly bonded to each other by the binder layers 72, 82. In particular, in an environment where the electrolyte is alkaline, the adhesive strength of polyvinylidene fluoride is maintained at an even higher level, making it more advantageous than other materials.

[0087] (6) An electrolytic cell according to a sixth aspect includes an ion exchange membrane, a current collector body formed of a plurality of fibers formed into a sheet and disposed on the surface of the ion exchange membrane, a binder layer covering the surface of each of the fibers, and an electrode catalyst layer including catalyst particles at least partially protruding from the surface of the binder layer, wherein the binder layer is formed from a resin material containing fluorine.

[0088] While efforts are being made to improve the electrolysis performance of the electrolysis cell 11, there is also a growing demand for a longer life for the electrode catalyst layer 90 in order to ensure operability. Therefore, in this embodiment, a fluorine-based resin material is used for the binder layers 72, 82. It is known that fluorine-containing resin materials have a stronger adhesive strength (bonding strength) between objects than other substances. According to the above configuration, the use of a fluorine-containing resin material for the binder layers 72, 82 makes it possible to maintain a state in which the power supply element and the catalyst particles 91 are strongly bonded to each other by the binder layers 72, 82.

[0089] (7) The electrolytic cell according to a seventh aspect is the electrolytic cell according to (6), wherein the binder layer is formed of polyvinylidene fluoride.

[0090] Among fluorine-containing resin materials, polyvinylidene fluoride is known to have particularly high adhesive strength (bonding strength) between objects compared to other fluorine-based resins. According to the above configuration, since a fluorine-containing resin material is used for the binder layers 72, 82, it is possible to maintain a state in which the power supply element and the catalyst particles 91 are strongly bonded to each other by the binder layers 72, 82. In particular, in an environment where the electrolyte is alkaline, the adhesive strength of polyvinylidene fluoride is maintained at an even higher level, making it more advantageous than other materials.

[0091] (8) An electrolysis device according to an eighth aspect includes an electrolysis cell according to any one of aspects (1) to (7), an electrolyte solution supply unit that supplies an electrolyte solution to the electrolysis cell, and a power supply unit that applies a voltage to the electrolysis cell.

[0092] According to the above configuration, it is possible to provide an electrolysis device having even higher electrolysis performance.

[0093] According to the present disclosure, it is possible to provide an electrolysis cell and an electrolysis device having better electrolysis performance.

[0094] REFERENCE SIGNS LIST 1...Electrolysis device 10...Electrolytic cell stack 11, 11A, 11B...Electrolytic cell 20...Electrolyte solution supply unit 30...Power supply unit 40...Electrolytic cell 41...First separator 42...Second separator 47...Cathode 48...Anode 51...First ion exchange membrane 51a...First surface 51b...Second surface 52...Second ion exchange membrane 52a...Third surface 52b...Fourth surface 53...Ionomer layer 54...Cathode catalyst layer 55...Cathode current collector 56...Anode catalyst layer 57...Anode current collector 71...Cathode current collector 72...Binder layer 73...Cathode catalyst particle 81...Anode current collector 82...Binder layer 83...Anode catalyst particle 90...Electrode catalyst layer 91...Catalyst particle

Claims

1. An electrolytic cell comprising an ion exchange membrane, a power supply body provided on the surface of the ion exchange membrane and composed of a plurality of fibers formed in a sheet shape, a binder layer covering the surface of each of the fibers, and an electrode catalyst layer containing catalyst particles at least partially protruding from the surface of the binder layer.

2. The electrolytic cell according to claim 1, wherein the surface area of the portion of the catalyst particles protruding from the surface of the binder layer is 20% or more and 80% or less of the total surface area including the protruding portion and the remaining portion of the binder layer.

3. The electrolytic cell according to claim 1 or 2, wherein the catalyst particles have electron conductivity, and the binder layer and the electrode catalyst layer do not contain a conductive aid.

4. The electrolytic cell according to claim 1 or 2, wherein the binder layer is formed of a resin material containing fluorine.

5. The electrolytic cell according to claim 4, wherein the binder layer is formed of polyvinylidene fluoride.

6. An electrolytic cell comprising an ion exchange membrane, a power supply body provided on the surface of the ion exchange membrane and composed of a plurality of fibers formed in a sheet shape, a binder layer covering the surface of each of the fibers, and an electrode catalyst layer containing catalyst particles at least partially protruding from the surface of the binder layer, wherein the binder layer is formed of a resin material containing fluorine.

7. The electrolytic cell according to claim 6, wherein the binder layer is formed of polyvinylidene fluoride.

8. An electrolytic device comprising the electrolytic cell according to claim 1 or 2, an electrolytic solution supply unit for supplying an electrolytic solution to the electrolytic cell, and a power supply unit for applying a voltage to the electrolytic cell.

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