Electrolysis cell and electrolysis device

Abstract

To provide an electrolysis cell and an electrolysis device having a better electrolysis performance.SOLUTION: The electrolysis cell includes an ion exchange membrane, a power feeder provided on the surface of the ion exchange membrane and constituted 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 including catalyst particles with at least a portion thereof protruding from the surface of the binder layer. At least a portion of the catalyst particles protrude from the surface of the binder layer. Therefore, the contact area with the electrolytic solution can be increased since the surface area of the exposed portion of the catalyst particles is increased.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an electrolytic cell and an electrolysis apparatus.

Background Art

[0002] As a device for generating hydrogen, a device (electrolysis apparatus) for electrolyzing water is known. In this type of device, water is filled in an electrolytic cell partitioned into a cathode chamber and an anode chamber by an ion exchange membrane, and electrolysis of water is performed by supplying power to a cathode and an anode. Hydrogen is generated in the cathode chamber by the reaction of water and electrons. The hydroxide ions generated 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 such a reaction, a large amount of hydrogen can be obtained.

[0003] On both sides in the thickness direction of the ion exchange membrane, current collectors interposed between an anode and a cathode are respectively arranged. As a specific example of the current collector, the one described in Patent Document 1 below is known. In the device according to Patent Document 1 below, a barrier layer for protecting a catalyst substance such as platinum is provided on the surface of the current collector. The barrier layer is formed of a polymer binder, a conductive ceramic material, or the like. Thereby, it is said that early corrosion of the current collector during the progress of the electrolysis reaction can be suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when giving priority to corrosion resistance as described above, there is a problem that the contact area between the catalyst substance and the electrolytic solution decreases by the amount of the barrier layer provided, and the desired electrolysis performance cannot be obtained.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide an electrolytic cell having better electrolytic performance and an electrolysis apparatus.

Means for Solving the Problems

[0007] In order to solve the above problems, an ion exchange membrane according to the present disclosure, 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 including catalyst particles at least partially protruding from the surface of the binder layer are provided.

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

Effects of the Invention

[0009] According to the present disclosure, an electrolytic cell having better electrolytic performance and an electrolysis apparatus can be provided.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an electrolytic cell and an electrolysis apparatus according to embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same reference numerals are given to configurations having the same or similar functions. In the present disclosure, "opposing" means that two members overlap when viewed in a certain direction, and may include the case where another member (for example, another layer) exists between the two members.

[0012] First, the Z direction, X direction, and Y direction 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 a direction intersecting (for example, orthogonal to) the Z direction, and is the direction from the central portion C of the membrane electrode assembly 43 to one end of the membrane electrode assembly 43, which will be described later. The Y direction is a direction intersecting (for example, orthogonal to) the Z direction and the X direction, and is, for example, the depth direction of the paper surface in FIG. 2. In the present disclosure, "area" means the area when viewed in the Z direction (that is, the area extending in the X direction and the Y direction). Also, in the present disclosure, "outer dimensions" means the outer dimensions when viewed in the Z direction. That is, "outer dimensions" and "area" may substantially mean the same thing and may be read interchangeably as appropriate.

[0013] <1. Configuration of the Electrolysis Apparatus> FIG. 1 is a schematic configuration diagram showing the overall configuration of the electrolysis apparatus 1 of the present embodiment. The electrolysis apparatus 1 is, for example, a device that generates hydrogen by electrolyzing water contained in an electrolytic solution. The electrolysis apparatus 1 is, for example, an anion exchange membrane (AEM) type electrolysis apparatus. However, the electrolysis apparatus 1 is not limited to the above example, and may be a different type of electrolysis apparatus such as a device for electrolytically reducing carbon dioxide.

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

[0015] (Electrolytic Cell Stack) The electrolytic cell stack 10 is an assembly 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.

[0016] (Electrolyte supply unit) The electrolyte supply unit 20 is a supply unit that supplies electrolyte to each electrolytic cell 11. The electrolyte is, for example, pure water or an aqueous alkali solution. The electrolyte 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 electrolyte 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 electrolyte supply unit 24, and piping lines L1, L2.

[0018] The hydrogen gas-liquid separator 21 stores the electrolyte. The supply port of the hydrogen gas-liquid separator 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 electrolyte stored in the hydrogen gas-liquid separator 21 toward the cathode chamber Sa of the electrolytic cell 11.

[0019] The return port of the hydrogen gas-liquid separator 21 is connected to the cathode chamber Sa of the electrolytic cell 11 via the piping line L2. An electrolyte containing hydrogen generated 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 part that separates hydrogen contained in the electrolyte. The hydrogen separated from the electrolyte by the hydrogen gas-liquid separator 21 is recovered by the hydrogen recovery unit 23. The hydrogen gas-liquid separator 21 is replenished with electrolyte from the first electrolyte 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 separation device 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 separation device 26 stores the electrolytic solution. The supply port of the oxygen gas-liquid separation device 26 is connected to the anode chamber Sb of the electrolytic cell 11 via the piping line L3. The second pump 27 is provided in the middle of the piping line L3 and sends the electrolytic solution stored in the oxygen gas-liquid separation device 26 toward the anode chamber Sb of the electrolytic cell 11.

[0022] The return port of the oxygen gas-liquid separation device 26 is connected to the anode chamber Sb of the electrolytic cell 11 via the piping line L4. An electrolytic solution containing oxygen generated in the electrolytic cell 11 flows into the oxygen gas-liquid separation device 26 from the electrolytic cell 11. The oxygen gas-liquid separation device 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 separation device 26 is recovered by the oxygen recovery unit 28. The oxygen gas-liquid separation device 26 is replenished with the electrolytic solution from the 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 necessary for the electrolysis of the electrolytic solution between the anode and the cathode of the electrolytic cell 11.

[0024] <2. Structure of the electrolytic cell> <2.1 Basic structure of the 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 surface of the internal space S of the electrolytic cell 11. The internal space S is a space including a cathode chamber Sa and an anode chamber Sb, which will be described later. The first separator 41 is, for example, in the shape of a rectangular plate and is formed of a metal member. The first separator 41 has a negative voltage applied thereto from the power supply unit 30 via a first current collector 61 (see FIG. 3), which will be described later.

[0026] The first separator 41 has a first end 41e1 (for example, the lower end) and a second end 41e2 (for example, the upper end) located on the side opposite to the first end 41e1. The above-described piping line L1 is connected to the first end 41e1 of the first separator 41. The above-described 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, which will be described later. A first flow path FP1 through which the electrolytic solution supplied from the piping line L1 flows is formed on the first inner surface 41a. The first flow path FP1 is, for example, a groove provided on 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 each structure (for example, the flow path structure) shown in FIG. 2 is merely an example and does not limit the content of the present embodiment. For example, various structures can be used for the flow path structure according to the size, purpose, and use environment of the device. This also applies to each structure shown in other figures.

[0027] (Second Separator) The second separator 42 is disposed with the internal space S interposed therebetween from at least a part 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, in the shape of a rectangular plate and is formed of a metal member. The second separator 42 has a positive voltage applied thereto 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 the electrolytic cell 40 of the electrolytic cell 11 as a pair of separators.

[0028] The second separator 42 has a first end 42e1 (e.g., the lower end) and a second end 42e2 (e.g., the upper end) located on the side opposite to the first end 42e1. The above-described piping line L3 is connected to the first end 42e1 of the second separator 42. The above-described 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 later. A second flow path FP2 through which the electrolytic solution supplied from the piping line L3 flows is formed on the second inner surface 42a. The second flow path FP2 is, for example, a groove provided on 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 through the piping line L4.

[0029] Here, for the sake of convenience of explanation, a configuration is described in which the first inner surface 41a of the first separator 41 has a groove for a flow path (first flow path FP1), and the second inner surface 42a of the second separator 42 has a groove for a flow path (second flow path FP2). However, for example, the first separator 41 of the electrolytic cell 11 included in the electrolytic cell stack 10 (see FIG. 1) may be a bipolar plate having similar grooves for flow paths (first flow path FP1, indicated by a two-dot chain line in FIG. 2) not only on the first inner surface 41a but also on the surface 41b on the side opposite to the first inner surface 41a. Also, the second separator 42 of the electrolytic cell 11 included in the electrolytic cell stack 10 may be a bipolar plate having similar grooves for flow paths (second flow path FP2, indicated by a two-dot chain line in FIG. 2) not only on the second inner surface 42a but also on the surface 42b on the side opposite to the second inner surface 42a. Note that the grooves for flow paths provided on both surfaces of the first separator 41 may have different shapes and arrangements from each other. Also, the grooves for flow paths provided on both surfaces of the second separator 42 may have different shapes and arrangements from each other.

[0030] The membrane electrode assembly (MEA: Membrane Electrode Assembly) 43 is a structure in which an ion exchange membrane, a catalyst, and a current collector 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 permeates 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) with hydroxide ion conductivity. However, the first ion exchange membrane 51 is not limited to the above example and may be a different type of ion exchange membrane from the above example. The first ion exchange membrane 51 is, for example, in the shape of a rectangular sheet. The outer dimension of the first ion exchange membrane 51 is smaller than the outer dimension 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 side opposite to the first surface 51a. In the internal space S, a cathode chamber Sa is defined between the first surface 51a of the first ion exchange membrane 51 and the first inner surface 41a 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 and hydrogen is generated from the electrolytic solution. Note that in this application, "XX is generated" may include the case 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 through the membrane electrode assembly 43. 2H2O + 2e- → H2 + 2OH- …(Chemical formula 1)

[0033] (Second ion exchange membrane) The second ion exchange membrane 52 is a membrane that selectively permeates 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 having hydroxide ion conductivity. However, the second ion exchange membrane 52 is not limited to the above examples, and may be an ion exchange membrane of a type different from the above examples. The second ion exchange membrane 52 is, for example, in the shape 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 side opposite 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, and oxygen is generated from the electrolytic solution. 2OH- → 1 / 2O2 + H2O + 2e- …(Chemical formula 2)

[0035] As a result, when viewed from the entire electrolytic cell 11, the following chemical reaction occurs. H2O → H2 + 1 / 2O2 …(Chemical formula 3)

[0036] In addition, in the present disclosure, ordinal numbers such as "first" and "second" attached to the names of the components are for convenience of explanation. For example, the names "third" and "fourth" do not assume the existence of the names "first" and "second" for the same member. In the present embodiment, the names "third surface 52a" and "fourth surface 52b" of the second ion exchange membrane 52 do not assume the existence of the first surface and the second surface on the second ion exchange membrane 52. Therefore, the names "third surface 52a" and "fourth surface 52b" may be read as "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 the second surface 51b of the first ion exchange membrane 51 facing the fourth surface 52b of the second ion exchange membrane 52. In the present disclosure, "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, and may also include the case where another layer (for example, the ionomer layer 53 described later) exists 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 as or different from each other. For example, the materials of the first ion exchange membrane 51 and the second ion exchange membrane 52 are selected as follows. That is, since no oxidation reaction occurs in the cathode chamber Sa, the first ion exchange membrane 51 does not need to have high oxidation resistance. Therefore, as the first ion exchange membrane 51, for example, a membrane made of a material with higher ion conductivity than the second ion exchange membrane 52 is adopted. On the other hand, since an oxidation reaction occurs in the anode chamber Sb, it is preferable that the second ion exchange membrane 52 has high oxidation resistance. Therefore, as the second ion exchange membrane 52, for example, a membrane made of a material with higher oxidation resistance than the first ion exchange membrane 51 is adopted.

[0039] The "membrane with high ion conductivity" is, for example, a membrane including a polystyrene-based or tetraphenyl-based composition in the main chain and an imidazolium group or a quaternary ammonium group in the side chain. The "membrane with high oxidation resistance" is, for example, a membrane including 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 area of the second surface 51b of the first ion exchange membrane 51 and over the entire area of the 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 the present 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 described above. The cathode catalyst layer 54 is, for example, in the shape of a rectangular sheet. In the present 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 is adjacent to the first ion exchange membrane 51. Note that in the present application, “adjacent” is not limited to the case where two members are adjacent to each other independently, and may also include the case where at least a part of one of the two members enters the other member. In the present embodiment, the cathode catalyst layer 54 is provided on the first surface 51a 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 a part of the cathode 47 of the electrolytic cell 11.

[0042] As shown in FIG. 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 portion that transmits the voltage applied to the first separator 41 to the cathode catalyst layer 54 itself. The cathode current collector 71 is, for example, in a mesh shape formed of carbon fibers. That is, a plurality of carbon fibers are intertwined to form the sheet-like cathode current collector 71.

[0043] The surface of each of these carbon fibers is covered with a binder layer 72. The binder layer 72 is a substance for fixing the cathode catalyst particles 73 to the surface of the carbon fiber. Specifically, a fluororesin 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. This is because these resin materials can maintain a high level of adhesion between substances, that is, bonding strength, over a long period of time. In particular, polyvinylidene fluoride exhibits particularly good bonding strength in an alkaline environment, and thus is effective when the electrolytic solution is an alkaline aqueous solution (for example, an aqueous potassium hydroxide 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 a single particle or an aggregate of these single particles. Most of the cathode catalyst particles 73 protrude from the surface of the binder layer 72. That is, at least a part of the surface of the granular cathode catalyst particles 73 protrudes further outside than the outer surface of the binder layer 72. As shown in FIG. 6, when the particle diameter of the cathode catalyst particles 73 is D (radius r), the surface area A of the particles exposed from the binder layer 72 with a thickness t is obtained by A = 2πr(2r - t).

[0045] However, since the actual particle diameter D of the cathode catalyst particles 73 varies within a range of about 1σ / D = 0.1 to 0.4 with respect to the average particle diameter σ, the total exposed area needs to be obtained by statistical simulation. That is, since the surface area of the catalyst exposed from the binder layer changes due to the variation in particle size, 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 the catalyst, since 1σ / D varies within a range of about 0.1 to 0.4 with respect to the average particle diameter D, the ratio of the surface area of the exposed portion of the cathode catalyst particles 73 to the total surface area (the total surface area of the binder layer 72) is as shown in FIG. 7 as an example of the calculation result. Specifically, considering the electrolytic performance and lifespan of the cathode catalyst particles 73, it is desirable that the surface area of the cathode catalyst particles 73 exposed from at least the binder layer 72 is in the range of 20% to 80% of the total surface area. More desirably, this surface area ratio is 40% to 60%. Most desirably, this surface area ratio is 50%.

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

[0047] Also, it is desirable that the thickness of the binder layer 72 is 20 to 100% of the average particle diameter. Furthermore, considering the balance between electrode performance and lifespan, since it is desirable to expose 40 to 60% of the total surface area to the electrolyte, the thickness of the binder layer 72 at that time is desirably 40 to 65% of the average particle diameter.

[0048] Even when the cathode catalyst particles 73 are aggregates, the index related to the control of the exposed area is the same as in the case of the single particles described above. That is, when the aggregate particle diameter = D (radius r), the surface area A of the exposed aggregate from the binder layer 72 with thickness t is obtained by A = 2kπr(2r - t). Here, k is a proportionality constant, which is appropriately set according to the primary particle diameter of the particles and the aggregate size.

[0049] As the material of the cathode catalyst particles 73, it contains one or more of nickel, nickel alloy, cerium oxide, lanthanum oxide, or platinum. Particularly preferably, platinum-supported carbon is used as the cathode catalyst particles 73. In the present disclosure, "XX oxide" may contain another material other than XX and oxygen.

[0050] In forming the cathode catalyst layer 54 as described above, for example, a method is adopted in which the cathode current collector 71 is immersed in a slurry containing the cathode catalyst particles 73 and a substance for forming the binder layer 72. At this time, by adjusting the volume fraction of the cathode catalyst particles 73 and the substance for forming the binder layer 72, the cathode catalyst particles 73 are exposed from the surface of the binder layer 72 as described above, and the ratio of the surface area of the exposed portion can be controlled within the above numerical range.

[0051] (Anode catalyst layer) The anode catalyst layer 56 is a layer that promotes the chemical reaction in the anode chamber Sb described above. The anode catalyst layer 56 is, for example, in the shape of a rectangular sheet. In the present 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 is adjacent to the second ion exchange membrane 52. For example, a part of the anode catalyst layer 56 may enter the surface portion of the second ion exchange membrane 52. In the present 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 the material of 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 it functions as a part of the anode 48 of the electrolytic cell 11.

[0052] As shown in FIG. 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 portion that transmits the voltage applied to the second separator 42 to the anode catalyst layer 56 itself. The anode current collector 81 is, for example, in a mesh shape formed of stainless steel fibers. That is, a plurality of stainless steel fibers are intertwined to form the sheet-like anode current collector 81.

[0053] The surface of each of these fibers is covered with a binder layer 82. The binder layer 82 is a substance for fixing the anode catalyst particles 83 to the surface of the stainless steel fiber. As with the cathode catalyst layer 54, a fluororesin material is preferably used as 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 the adhesiveness between substances, that is, the bonding strength, at a high level over 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 a single particle or an aggregate of these single particles. Most of the anode catalyst particles 83 protrude from the surface of the binder layer 82. That is, at least a part of the surface of the granular anode catalyst particles 83 protrudes further outside than the outer surface of the binder layer 82. It is desirable that the ratio of the surface area of the exposed portion of the anode catalyst particles 83 to the total surface area of the binder layer 82 be the same as the numerical range based on the simulation example of the cathode catalyst particles 73 described above. Also, the method for producing the anode catalyst layer 56 and the method for controlling the exposed area of the anode catalyst particles 83 are the same as the above-described methods for the cathode catalyst layer 54.

[0055] As the material of the anode catalyst particles 83, it contains one or more of nickel, nickel alloy, nickel oxide, copper oxide, iridium oxide, niobium oxide, lead oxide, or bismuth oxide. As described above, in the present disclosure, "XX oxide" may contain another material other than XX and oxygen. For example, "nickel oxide" may contain another material such as iron or cobalt in addition to nickel and oxygen. Also, "copper oxide" may contain another material such as cobalt in addition to copper and oxygen. "Iridium oxide" may contain another material such as ruthenium in addition to iridium and oxygen. "Lead oxide" may contain another material such as ruthenium in addition to lead and oxygen. "Bismuth oxide" may contain another material such as ruthenium in addition to bismuth and oxygen.

[0056] Also, in the above-described cathode catalyst layer 54 and anode catalyst layer 56 (hereinafter collectively referred to as the electrode catalyst layer 90), since the above-described materials are used as the cathode catalyst particles 73 and anode catalyst particles 83 (hereinafter sometimes collectively referred to as the catalyst particles 91), these materials have electron conductivity. Therefore, the binder layers 72, 82, and the electrode catalyst layer 90 do not contain a conductive aid for complementing the electron conductivity.

[0057] FIG. 3 is an exploded perspective view showing the electrolytic cell 11. The electrolytic cell 11 includes, in addition to the above-described configuration, 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.

[0058] (First current collector) The first current collector 61 is an electrical connection portion that transmits the negative voltage applied from the power supply unit 30 to the first separator 41. The first current collector 61 is a plate member made of metal (for example, a copper plate). The first current collector 61 is in contact with 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, for example. A negative voltage required for electrolysis in the electrolytic cell 11 is applied to the first current collector 61 from the power supply unit 30. Note that the first current collector 61 may be shared by two adjacent electrolytic cells 11 in the electrolytic cell stack 10.

[0059] (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 plate member made of metal (for example, a copper plate). The second current collector 62 is in contact with the second separator 42 from the side opposite to the internal space S of the electrolytic cell 11, for example, and is electrically connected to the second separator 42. A positive voltage necessary for electrolysis in the electrolytic cell 11 is applied to the second current collector 62 from the power supply unit 30. Note that the second current collector 62 may be shared by two adjacent electrolytic cells 11 in the electrolytic cell stack 10.

[0060] (First insulator) The first insulator 63 is a member that insulates between the outer peripheral part of the first separator 41 and the outer peripheral part of the second separator 42. 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, 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 insulates between the outer peripheral part of the first separator 41 and the outer peripheral part 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. Also, the first insulator 63 and the second insulator 64 can 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 dimension of the first insulating material 65 is, for example, the same as the outer dimension of the first current collector 61 or larger than the outer dimension 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 the outer size of the second current collector 62 or larger than the outer size of the second current collector 62.

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

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

[0066] Note that the electrolytic cell 11 is not limited to the above-described configuration. 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 the first separator 41 or the second separator 42, which are both bipolar plates. In this case, between two adjacent electrolytic cells 11, there may be no current collector (the first current collector 61 or the second current collector 62), insulator (the first insulator 63 or the second insulator 64), insulating material (the first insulating material 65 or the second insulating material 66), or end plate (the first end plate 67 or the second end plate 68).

[0067] (Function and effect) Here, in manufacturing an electrolytic cell, a method has been proposed in which a layer (barrier layer) that protects a catalyst substance such as platinum is provided on the surface of a solid current collector that is not a fiber material. The barrier layer is formed of a polymer binder, a conductive ceramic material, or the like. This is for the purpose of suppressing premature corrosion of the current collector during the progress of the electrolytic reaction. However, when such corrosion resistance is prioritized, there has been a problem that the contact area between the catalyst substance and the electrolytic solution decreases by the amount of the barrier layer provided, and the desired electrolytic performance cannot be obtained. To solve this problem, each of the above-described configurations is adopted in the present embodiment.

[0068] According to the above configuration, at least a part of the catalyst particles 91 protrudes from the surface of the binder layers 72 and 82. For this reason, since the surface area of the exposed portion of the catalyst particles 91 increases, the contact area with the electrolytic solution can be increased. Thereby, it becomes possible to improve the electrolytic performance from the initial stage to the final stage of the reaction. In particular, since the catalyst particles 91 are fixed to each of the fibers of the current collector via the binder layers 72 and 82, the electrolytic solution penetrates between the fibers, so that the electrolytic reaction can proceed more stably and efficiently. Thus, since the performance of each electrolytic cell 11 is improved, it becomes possible to reduce the number of electrolytic cells 11 required for the same amount of hydrogen generation. As a result, it is possible to achieve miniaturization of the entire electrolysis apparatus 1 and energy saving of the plant.

[0069] According to the above configuration, the surface area of the protruding portion of the catalyst particles 91 is 20% or more and 80% or less with respect to the total surface area of the binder layers 72 and 82. Thereby, while maintaining the holding force for the catalyst particles 91 as the binder layers 72 and 82, it is possible to realize an improvement in electrolysis performance. On the contrary, if the surface area of the catalyst particles 91 exposed from the binder layers 72 and 82 is small, the catalyst particles 91 may not be able to contact ions through the electrolyte, so the electrolysis performance may decrease. According to the above configuration, such a possibility can be greatly reduced. In addition, since a considerable surface area of the binder layers 72 and 82 themselves is ensured, the holding force for the catalyst particles 91, that is, the life can also be extended. Thereby, it is possible to continuously operate the electrolytic cell 11 stably for a longer period of time.

[0070] According to the above configuration, since the catalyst particles 91 have electron conductivity, it is no longer necessary to complement the conductivity by the binder layers 72 and 82 and the electrode catalyst layer 90. Therefore, good electrolysis performance can be obtained without containing a conductive assistant in the entire binder layers 72 and 82 and the electrode catalyst layer 90. Therefore, it is possible to reduce the manufacturing cost and maintenance cost of the device by the amount that the conductive assistant can be omitted. As a result, the offering price of hydrogen, which is the final product generated by the electrolysis reaction, can be lowered.

[0071] Here, while aiming to improve the electrolysis performance of the electrolytic cell 11, there is also an increasing demand for extending the service life of the electrode catalyst layer 90 from the perspective of ensuring operability. Therefore, in the present embodiment, a fluorine-based resin material is used for the binder layers 72 and 82. Resin materials containing fluorine are known to have a higher adhesive force (bonding force) between objects compared to other substances. According to the above configuration, since a resin material containing fluorine is used as the binder layers 72 and 82, it becomes possible to maintain a state in which the power supply body and the catalyst particles 91 are strongly bonded to each other by the binder layers 72 and 82. As a result, deterioration of the electrolytic cell 11 can be avoided, and long service life can be achieved. That is, it is possible to continuously use the electrolytic cell 11 stably without replacing it or the like over a long period of time. Thereby, it becomes possible to significantly reduce the operation cost of the entire apparatus.

[0072] Here, among the resin materials containing fluorine, polyvinylidene fluoride is known to have a particularly high adhesive force (bonding force) between objects compared to other fluorine-based resins. According to the above configuration, since a resin material containing fluorine is used as the binder layers 72 and 82, it becomes possible to maintain a state in which the power supply body and the catalyst particles 91 are strongly bonded to each other by the binder layers 72 and 82. In particular, in an environment where the electrolytic solution exhibits alkalinity, the adhesive force by polyvinylidene fluoride is maintained at an even higher level, which is advantageous compared to other substances. As a result, deterioration of the electrolytic cell 11 can be avoided, and long service life can be achieved. That is, it is possible to continuously use the electrolytic cell 11 stably without replacing it or the like over a long period of time. Thereby, it becomes possible to significantly reduce the operation cost of the entire apparatus.

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

[0074] For example, the materials of the cathode current collector 71 and the anode current collector 81 described in the above embodiment are just examples. Any material that is not attacked by hydrogen or oxygen and promotes the oxidation-reduction reaction with the electrolytic solution can be applied as the cathode current collector 71 or the anode current collector 81.

[0075] In the above embodiment, the form in which two ion exchange membranes 120 are bonded together has been described. However, the form 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 current collector are provided on both surfaces of one ion exchange membrane 120.

[0076] <Supplementary Note> The electrolytic cell and the electrolysis apparatus described in each embodiment can be understood as follows, for example.

[0077] (1) The electrolytic cell according to the first aspect includes an ion exchange membrane, a current collector 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 including catalyst particles at least a part of which protrudes from the surface of the binder layer.

[0078] According to the above configuration, at least a part of the catalyst particles 91 protrudes from the surfaces of the binder layers 72 and 82. Therefore, since the surface area of the exposed portion of the catalyst particles 91 increases, the contact area with the electrolytic solution can be increased.

[0079] (2) The electrolytic cell according to the second aspect is the electrolytic cell of (1), and 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.

[0080] According to the above configuration, the surface area of the protruding portion of the catalyst particles 91 is 20% or more and 80% or less with respect to the total surface area of the binder layers 72 and 82. Thereby, while maintaining the holding force of the binder layers 72 and 82 for the catalyst particles 91, an improvement in electrolysis performance can be realized.

[0081] (3) The electrolytic cell according to the 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 assistant.

[0082] According to the above configuration, since the catalyst particles 91 have electronic conductivity, it is not necessary to complement the conductivity by the binder layers 72, 82 and the electrode catalyst layer 90. Therefore, good electrolytic performance can be obtained without containing a conductive assistant in the entire binder layers 72, 82 and the electrode catalyst layer 90.

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

[0084] Here, while aiming to improve the electrolytic performance of the electrolytic cell 11, the demand for extending the life of the electrode catalyst layer 90 has also increased from the viewpoint of ensuring operability. Therefore, in the present embodiment, a fluorine-based resin material is used for the binder layers 72, 82. The resin material containing fluorine is known to have a higher adhesive force (bonding force) between objects than other substances. According to the above configuration, since the resin material containing fluorine is used as the binder layers 72, 82, it is possible to maintain a state in which the power supply body and the catalyst particles 91 are strongly bonded to each other by the binder layers 72, 82.

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

[0086] Here, among resin materials containing fluorine, polyvinylidene fluoride is known to have a particularly high adhesive force (bonding force) between objects compared to other fluorine-based resins. According to the above configuration, since a resin material containing fluorine is used as the binder layers 72 and 82, it is possible to maintain a state in which the power supply body and the catalyst particles 91 are strongly bonded to each other by the binder layers 72 and 82. In particular, in an environment where the electrolytic solution exhibits alkalinity, the adhesive force by polyvinylidene fluoride is maintained at an even higher level, which is advantageous compared to other substances.

[0087] (6) The electrolytic cell according to the sixth aspect includes 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 including catalyst particles at least partially protruding from the surface of the binder layer. The binder layer is formed of a resin material containing fluorine.

[0088] Here, while aiming to improve the electrolytic performance of the electrolytic cell 11, the demand for extending the service life of the electrode catalyst layer 90 is also increasing from the perspective of ensuring operability. Therefore, in the present embodiment, a fluorine-based resin material is used for the binder layers 72 and 82. Resin materials containing fluorine are known to have a higher adhesive force (bonding force) between objects compared to other substances. According to the above configuration, since a resin material containing fluorine is used as the binder layers 72 and 82, it is possible to maintain a state in which the power supply body and the catalyst particles 91 are strongly bonded to each other by the binder layers 72 and 82.

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

[0090] Here, among the resin materials containing fluorine, polyvinylidene fluoride is known to have a particularly high adhesive force (bonding force) between objects compared to other fluorine-based resins. According to the above configuration, since a resin material containing fluorine is used as the binder layers 72 and 82, it becomes possible to maintain a state in which the power supply body and the catalyst particles 91 are strongly bonded to each other by the binder layers 72 and 82. In particular, in an environment where the electrolytic solution exhibits alkalinity, the adhesive force by polyvinylidene fluoride is maintained at a higher level, which is advantageous compared to other substances.

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

[0092] According to the above configuration, an electrolytic device having higher electrolytic performance can be provided.

Explanation of reference numerals

[0093] 1... Electrolytic device 10... Electrolytic cell stack 11, 11A, 11B... Electrolytic cell 20... Electrolytic 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 particles 81…Anode current collector 82…Binder layer 83…Anode catalyst particles 90…Electrode catalyst layer 91…Catalyst particles

Claims

1. 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. An electrolytic cell comprising the above.

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 electronic conductivity, and the binder layer and the electrode catalyst layer do not contain a conductive assistant.

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 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. An electrolytic cell comprising the above, 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. The electrolytic device comprising the above.

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