Electrode catalyst, water electrolysis unit and water electrolysis device of water electrolysis unit

Abstract

An electrode catalyst for a water electrolysis unit, comprising a catalyst and a neutral, inherently microporous polymer.

Description

Technical Field

[0001] This disclosure relates to electrode catalysts, water electrolysis units, and water electrolysis devices for water electrolysis units. Background Technology

[0002] In recent years, there has been a desire to develop catalyst materials that can be used in water electrolysis devices.

[0003] Patent Document 1 discloses a polymer having a trog base backbone. Patent Document 2 discloses a polymer having a spirodiindene backbone. Patent Document 3 discloses a polymer membrane containing imide groups.

[0004] Non-Patent Document 1 discloses a membrane comprising polymers of intrinsic microporosity (PIM). Non-Patent Document 2 discloses a porous polymer having a trog base.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2017 / 091357

[0008] Patent Document 2: International Publication No. 2005 / 012397

[0009] Patent Document 3: U.S. Patent Application Publication No. 2014 / 255636

[0010] Non-patent literature

[0011] Non-patent literature 1: Canghai Ma et al., Polymers of Intrinsic Microporosity (PIMs) Gas Separation Membranes: A mini Review (PIMs), Proceedings of the Nature Research Society, 2018, Vol. 2, No. 02002, p. 1-19

[0012] Non-patent literature 2: Mariolino Carta et al., The synthesis of microporous polymers using Troger's base formation, Polymer Chemistry, 2014, Vol.5, pp.5267-5272 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] This disclosure provides an electrode catalyst for a water electrolysis unit with low overvoltage.

[0015] Methods for solving problems

[0016] One aspect of this disclosure provides an electrode catalyst for a water electrolysis unit, comprising:

[0017] catalyst, and

[0018] Neutral, inherently microporous polymer.

[0019] Invention Effects

[0020] According to this disclosure, an electrode catalyst for a water electrolysis unit with low overvoltage can be provided. Attached Figure Description

[0021] [ Figure 1 ] Figure 1 A diagram illustrating the electrode catalyst of the water electrolysis unit according to the first embodiment is shown.

[0022] [ Figure 2 ] Figure 2 The diagram illustrates an example of the crystal structure of a layered double hydride (LDH).

[0023] [ Figure 3 ] Figure 3 A cross-sectional view is shown schematically as an example of a water electrolysis unit according to the second embodiment.

[0024] [ Figure 4 ] Figure 4 A cross-sectional view is shown schematically as an example of a water electrolysis apparatus according to the third embodiment.

[0025] [ Figure 5 ] Figure 5 A cross-sectional view is shown schematically of another example of the water electrolysis unit involved in the fourth embodiment.

[0026] [ Figure 6 ] Figure 6 A cross-sectional view is shown schematically of another example of the water electrolysis apparatus according to the fifth embodiment. Detailed Implementation

[0027] (The insights that form the basis of this disclosure)

[0028] As a countermeasure against global warming, the utilization of renewable energy sources such as solar and wind power has attracted much attention. However, in the power generation using renewable energy, there is a problem of surplus electricity being wasted. Therefore, the utilization efficiency of renewable energy is not necessarily full. Thus, a method for producing and storing hydrogen using surplus electricity has been studied.

[0029] Water electrolysis is a common method for producing hydrogen using surplus electricity. To produce hydrogen cheaply and stably, highly efficient and long-life water electrolysis devices need to be developed. A key component of a water electrolysis device is the membrane electrode assembly (MEA), which consists of a gas diffusion layer, a catalyst, and an electrolyte membrane.

[0030] To provide a highly efficient and long-life water electrolysis device, it is particularly necessary to improve the performance and durability of the catalyst. In the electrode catalyst of the water electrolysis unit, organic materials can be used to improve the dispersibility of the catalyst material and / or to enhance its adhesion to substrates such as electrodes. By using organic materials, it is possible to improve either the dispersibility of the catalyst material or the adhesion to the substrate.

[0031] However, organic materials typically have high electrical resistance, and by covering the active sites on the catalyst surface with organic materials, overvoltage increases when a voltage is applied. Therefore, it is important to provide electrode catalysts that reduce losses caused by electrode overvoltage even when organic materials are used. Consequently, the inventors of this application have conducted extensive research on materials capable of suppressing the area covering the catalyst. As a result, it has been discovered for the first time that the use of inherently microporous polymers (PIMs) is advantageous in reducing overvoltage of electrode catalysts in water electrolysis units.

[0032] Based on the above insights, the inventors of this application have discovered the following novel electrode catalyst for a water electrolysis unit.

[0033] (A summary of one approach covered in this disclosure)

[0034] The electrode catalyst of the water electrolysis unit according to the first aspect of this disclosure comprises:

[0035] catalyst, and

[0036] Neutral, inherently microporous polymer.

[0037] According to the first method, an electrode catalyst with a low overvoltage water electrolysis unit can be provided.

[0038] In the second aspect of this disclosure, for example, in the electrode catalyst of the water electrolysis unit involved in the first aspect, the aforementioned inherently microporous polymer may have a Trog base framework.

[0039] In the third aspect of this disclosure, for example, in the electrode catalyst of the water electrolysis unit involved in the first aspect, the aforementioned inherently microporous polymer may have a spirodiindene framework.

[0040] In the fourth aspect of this disclosure, for example, in the electrode catalyst of the water electrolysis unit involved in the first aspect, the aforementioned inherently microporous polymer may have a polyimide backbone.

[0041] According to methods 2 to 4, the electrode catalyst of the water electrolysis unit can suppress the increase of overvoltage.

[0042] The water electrolysis unit involved in the fifth method of this disclosure has the following features:

[0043] anode,

[0044] cathode, and

[0045] The electrolyte membrane disposed between the anode and the cathode,

[0046] At least one of the above-mentioned anode and cathode comprises the electrode catalyst involved in any of the first to fourth embodiments.

[0047] According to method 5, the water electrolysis unit can suppress the increase of overvoltage.

[0048] In the sixth aspect of this disclosure, for example in the water electrolysis unit involved in the fifth aspect, the electrolyte membrane may include a proton exchange membrane.

[0049] In the seventh aspect of this disclosure, for example, in the water electrolysis unit involved in the fifth aspect, the electrolyte membrane may include an anion exchange membrane.

[0050] According to methods 6 and 7, the oxygen produced at the anode and the hydrogen produced at the cathode are not easily mixed.

[0051] The water electrolysis unit involved in the eighth method of this disclosure has the following features:

[0052] The membrane separating the first space from the second space

[0053] The anode and the anode set in the first space mentioned above

[0054] The cathode is installed in the aforementioned second space.

[0055] At least one of the above-mentioned anode and cathode comprises the electrode catalyst involved in any of the first to fourth embodiments.

[0056] According to method 8, the water electrolysis unit can suppress the increase of overvoltage.

[0057] The water electrolysis apparatus according to the ninth aspect of this disclosure comprises:

[0058] The water electrolysis unit and voltage applicator involved in any of the methods 5 to 8

[0059] The voltage applicator is connected to the anode and the cathode and applies a voltage between the anode and the cathode.

[0060] According to method 9, the water electrolysis device can suppress the increase of overvoltage.

[0061] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to these embodiments.

[0062] (First Embodiment)

[0063] Figure 1 The diagram illustrates the electrode catalyst of the water electrolysis unit according to this embodiment. The electrode catalyst 1 according to this embodiment includes a catalyst 10 and a neutral, inherently microporous polymer (PIM) 11. PIM 11 is present in at least a portion of the surface of the catalyst 10. With this configuration, even if PIM 11 is present on the surface of the catalyst 10, the area of ​​the surface exposed to the catalyst 10 is not easily reduced, thus suppressing the decrease in the catalytic activity of the electrode catalyst 1. Therefore, when a voltage is applied to the electrode catalyst 1, the increase in overvoltage can be suppressed. That is, the electrode catalyst 1 can have a low overvoltage.

[0064] [Inherently microporous polymers]

[0065] Typically, intrinsically microporous polymers (PIM)11 are organic polymers with a specific molecular structure and inherent microporosity.

[0066] As mentioned above, PIM11 is neutral. "Neutral" means that the molecule does not contain either anion exchange groups or cation exchange groups. Examples of anion exchange groups include quaternary ammonium groups. Examples of cation exchange groups include sulfonic acid ion groups.

[0067] PIM11 may be present in at least a portion of the surface of the catalyst 10. Furthermore, PIM11 may also be present on, for example, the substrate on which the electrode catalyst 1 is to be formed. Specifically, PIM11 may also be present on the surface of the substrate. By including PIM11 in the electrode catalyst 1, and thus forming the electrode catalyst 1 on the substrate, the bonding force between the substrate and the catalyst 10 can be improved. Therefore, an electrode catalyst 1 with high durability can be provided.

[0068] PIM11 can also serve to disperse the electrode catalyst 1 among itself. In this case, by including PIM11 in the electrode catalyst 1, it is possible to prevent the electrode catalyst 1 from agglomerating among itself.

[0069] The molecular structure of PIM11 is not limited to a specific one. Examples of its molecular structures include trog base backbone, spirodiindane backbone, and polyimide backbone.

[0070] The trog base skeleton has, for example, a bicyclic compound containing two bridged nitrogen atoms. The nitrogen atoms form a chiral center. The trog base skeleton can further have a bridged ethanoanthracene skeleton and a tripterene skeleton. Specifically, the trog base skeleton has the molecular structure represented by the following general formula (1).

[0071]

[0072] In general formula (1), L represents a linker. The linker L is not limited to a specific structure. Linkers L include, for example, aromatic rings, spirodiindene skeletons, bridged ethylene anthracene skeletons, and tripterene skeletons.

[0073] The spirodiindane skeleton, for example, has two indane atoms. The two indane atoms form a spiro compound bonded together through a central spiro atom. A spiro compound is a bicyclic organic compound in which one of the atoms constituting the ring is shared with other rings. This atom is called a spiro atom. In this disclosure, the indane atoms comprise, for example, a benzene ring bonded to a five-membered ring containing a spiro atom or a six-membered ring containing a spiro atom. Specifically, the spirodiindane skeleton has a molecular structure represented by the following general formula (2) or (3).

[0074]

[0075] The polyimide backbone is formed, for example, by the condensation polymerization of an anhydride and a diamine. The anhydride and diamine may further comprise a spirodiinden backbone, a bridged ethyl anthracene backbone, and a tripterene backbone. The polyimide backbone has, for example, the molecular structure represented by the following general formula (4).

[0076]

[0077] In general formula (4), L represents a linker. The linker L is not limited to a specific structure. Linkers L include, for example, aromatic rings, spirodiindene skeletons, bridged ethylene anthracene skeletons, and tripterene skeletons.

[0078] Examples of PIM11 include organic polymers with a trog base backbone, organic polymers with a spirodiindane backbone, and organic polymers with a polyimide backbone. The specific molecular structure of PIM11 may include at least one backbone selected from the group consisting of a trog base backbone, a spirodiindane backbone, and a polyimide backbone. These backbones may possess inherent microporosity. Furthermore, these backbones may be backbones with high rigidity. By including these backbones in the molecular structure, PIM11 can possess the desired porosity. PIM11 may have these backbones on the main chain or on the side chains. PIM11 may have a trog base backbone, a spirodiindane backbone, and a polyimide backbone, or it may also have other substituents. Examples of other substituents include halogen groups, hydroxyl groups, alkyl groups, alkoxy groups, carboxyl groups, ester groups, acyl groups, amino groups, nitro groups, sulfonyl groups, and aryl groups. Examples of halogen groups include fluorine groups, chloro groups, and bromine groups.

[0079] PIM11 may include at least one organic polymer selected from the group consisting of organic polymers having a Trog base backbone, organic polymers having a spirodiindane backbone, and organic polymers having a polyimide backbone.

[0080] The average pore diameter of PIM11 is, for example, 4 nm or less. The average pore diameter of PIM11 can be determined using the Brunauer-Emmett-Teller (BET) method, which is an N2 gas adsorption method. The average pore diameter of PIM11 can be determined, for example, as described below. Using a pore distribution measuring apparatus VacPrep061 manufactured by Shimadzu Corporation-Micromerity, a sample containing PIM11 was degassed under reduced pressure for 15 hours at 100°C. Then, using an automatic specific surface area measuring apparatus Tristar II 3020 manufactured by Shimadzu Corporation-Micromerity, the pore distribution was analyzed by N2 gas adsorption, thereby allowing the calculation of the average pore diameter of PIM11.

[0081] [catalyst]

[0082] Catalyst 10 is a material active in the generation of gases such as hydrogen and oxygen at the anode or cathode of a water electrolysis unit. Examples of catalyst 10 include metals and metal oxides. An example of a metal is Pt. Examples of metal oxides include layered double hydroxides (LDH) and IrO. x .

[0083] LDH contains, for example, two or more transition metals. Transition metals include, for example, at least two metals selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, W, and Ru.

[0084] LDH has a composition represented by, for example, the following compositional formula (1).

[0085] [M1 2+ 1-x M2 3+ x (OH)2][yA n- ·mH2O]···Composition formula (1)

[0086] In composition formula (1), M1 2+ is a divalent transition metal ion. M2 3+ is a trivalent transition metal ion. A n- is an interlayer anion. x is a rational number satisfying the condition 0 < x < 1. y is a number corresponding to the requirement for charge balance. n is an integer. m is an appropriate rational number.

[0087] LDH may contain Ni and Fe. In composition formula (1), M1 may be Ni, and M2 may be Fe. That is, the transition metal elements contained in LDH may be Ni and Fe. According to such a composition, the electrode catalyst 1 can have higher catalytic activity. <0^000245>The ratio of the amount of substance of Fe contained in LDH to the total amount of substance of Ni and Fe may be 0.25 or more and 0.5 or less. According to such a composition, the electrode catalyst 1 can have higher catalytic activity.

[0089] LDH may contain a chelating agent. In this case, the chelating agent can coordinate with the transition metal ions in LDH. Thereby, the dispersion stability of LDH can be further improved. In addition, since LDH contains a chelating agent, LDH with a small particle size can be synthesized. As a result, the surface area of LDH can be increased, and thus the catalytic activity can be improved. The average particle size of LDH may be 100 nm or less, or may be 50 nm or less. In addition, the average particle size of LDH may be 10 nm or less. The average particle size of LDH is the following value: when the particle size distribution of LDH obtained by small-angle X-ray scattering (SAXS) is represented by a two-dimensional distribution diagram showing the relationship between the particle size and the distribution, the value obtained by dividing the area of the two-dimensional distribution diagram by the total number of particles. The so-called distribution is a value proportional to the total volume occupied by the number of particles of that particle size. The area of the two-dimensional distribution diagram is, for example, the product of the particle size and the number of particles corresponding to that particle size.

[0090] Chelating agents are not limited to specific chelating agents. Chelating agents are, for example, organic compounds that coordinate with a transition metal in an LDH. Chelating agents can be at least one organic ligand selected from bidentate and tripentate organic ligands. Examples of chelating agents include β-diketones, β-keto esters, and hydroxycarboxylic acids. Examples of β-diketones include acetylacetone (ACAC), trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, thiophenecarboxyltrifluoroacetone, di-tert-valerylmethane, dibenzoylmethane, and ascorbic acid. Examples of β-keto esters include methyl acetoacetate, ethyl acetoacetate, allyl acetoacetate, benzyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, isobutyl acetoacetate, tert-butyl acetoacetate, 2-methoxyethyl acetoacetate, and methyl 3-oxovalerate. Examples of hydroxycarboxylic acids and their salts include tartaric acid, citric acid, malic acid, gluconic acid, ferulic acid, lactic acid, glucuronic acid, and their salts. The chelating agent may include at least one chelating agent selected from the group consisting of acetylacetone and trisodium citrate. Alternatively, the chelating agent may be at least one chelating agent selected from acetylacetone and trisodium citrate.

[0091] A n- These are interlayer ions. A n- These can be inorganic or organic ions. An example of an inorganic ion is CO32-. 2- NO3 - Cl - SO4 2- ,Br - OH - F - I - Si2O5 2- B4O5(OH)4 2- and PO4 3- Examples of organic ions include CH3(CH2). n SO 4- CH3(CH2) n COO - CH3(CH2) n PO 4- and CH3(CH2) n NO 3- A n- It is an anion that is inserted between the layers of metal hydroxide along with water molecules. A n- The charge and size of the ions are not limited to specific values. LDH can contain one type of A. n- It can also contain multiple A's. n- .

[0092] Figure 2 A diagram illustrating an example of the crystal structure of LDH represented by formula (1). Figure 2As shown, LDH20 in M1 2+ or M2 3+ The vertices of the octahedron centered on the center have OH - Ions. Metal hydroxides are composed of [M1] 2+ 1-x M2 3+ x (OH)2] x+ The metal hydroxide has a layered structure in which hydroxide octahedrons share edges and are connected in two dimensions. Anions and water molecules are located between the layers of metal hydroxide. The metal hydroxide layer functions as the host layer 21, while the anions and water molecules are inserted as guest layers 22. That is, as a whole, LDH20 has a sheet-like structure formed by alternating layers of the host metal hydroxide layer 21 and the guest layers of anions and water molecules 22. LDH20 has M1 contained in the metal hydroxide layer 2+ Part of it was replaced with M2 3+ The structure formed by this process. Therefore, the surface of LDH20 is usually positively charged.

[0093] [Carrier]

[0094] Electrode catalyst 1 may also include a support. With this configuration, catalyst 10 is stably configured using a support for catalyst 10, and therefore, the catalytic activity of electrode catalyst 1 is easily maintained at a high level.

[0095] Typically, the carrier is conductive. The carrier is not limited to a specific material. Examples of carriers include transition metals and carbon materials. Examples of transition metals include V, Cr, Mn, Fe, Co, Ni, Cu, W, and Ru. Examples of carbon materials include acetylene black and Ketjen black (KB).

[0096] The shape of the carrier is not limited to a specific shape. The carrier can be foam-like or particle-like.

[0097] The electrode catalyst 1 described in this embodiment can be used in, for example, a proton exchange membrane type water electrolysis device, an anion exchange membrane type water electrolysis device, or an alkaline diaphragm type water electrolysis device. In the aforementioned water electrolysis devices, the electrode catalyst 1 can be selected from at least one of the anode and cathode.

[0098] (Second Implementation)

[0099] Figure 3 A cross-sectional view is shown schematically as an example of a water electrolysis unit according to this embodiment.

[0100] The water electrolysis unit 2 includes an electrolyte membrane 31, an anode 100, and a cathode 200. The electrolyte membrane 31 is disposed, for example, between the anode 100 and the cathode 200. At least one of the anode 100 and the cathode 200 includes the electrode catalyst 1 described in the first embodiment.

[0101] Electrolyte membrane 31 can be an ion-conducting electrolyte membrane. Electrolyte membrane 31 is not limited to a specific type. Electrolyte membrane 31 can include a proton exchange membrane. Electrolyte membrane 31 can also be a proton exchange membrane. Electrolyte membrane 31 can include anion exchange membrane. Electrolyte membrane 31 can also be anion exchange membrane. Electrolyte membrane 31 is configured to prevent the oxygen generated in anode 100 from mixing with the hydrogen generated in cathode 200.

[0102] The anode 100 includes, for example, a catalyst layer 30. The catalyst layer 30 may be disposed on a main surface of the electrolyte membrane 31. The term "main surface" refers to the surface of the electrolyte membrane 31 with the largest area. The electrode catalyst contained in the catalyst layer 30 may be the electrode catalyst 1 of the first embodiment. In the anode 100, a porous and conductive gas diffusion layer 33 may be further disposed on the catalyst layer 30.

[0103] The cathode 200 includes, for example, a catalyst layer 32. The catalyst layer 32 can be disposed on another main surface of the electrolyte membrane 31. That is, the catalyst layer 32 can be disposed on a main surface opposite to the main surface where the catalyst layer 30 is disposed, relative to the electrolyte membrane 31. The catalyst metal used in the catalyst layer 32 is not limited to a specific type. The electrode catalyst can be platinum or electrode catalyst 1. In the cathode 200, a porous and conductive gas diffusion layer 34 can be further disposed on the catalyst layer 32.

[0104] Based on the above configuration, at least one of the anode 100 and cathode 200 contains electrode catalyst 1, so the water electrolysis unit 2 can suppress the increase of overvoltage.

[0105] (Third Implementation)

[0106] Figure 4 A cross-sectional view is shown schematically as an example of a water electrolysis apparatus according to this embodiment.

[0107] The water electrolysis apparatus 3 includes a water electrolysis unit 2 and a voltage applicator 40. The water electrolysis unit 2 is the same as that in the second embodiment, so its description is omitted.

[0108] The voltage applicator 40 is connected to the anode 100 and cathode 200 of the water electrolysis unit 2. The voltage applicator 40 is a device for applying voltage to the anode 100 and cathode 200 of the water electrolysis unit 2.

[0109] The voltage applicator 40 increases the potential in the anode 100 and decreases the potential in the cathode 200. The voltage applicator 40 is not limited to any particular type, as long as it can apply a voltage between the anode 100 and the cathode 200. The voltage applicator 40 can also be a device for adjusting the voltage applied between the anode 100 and the cathode 200. Specifically, when the voltage applicator 40 is connected to a DC power source such as a battery, solar cell, or fuel cell, the voltage applicator 40 has a DC / DC converter. When the voltage applicator 40 is connected to an AC power source such as an industrial power source, the voltage applicator 40 has an AC / DC converter. The voltage applicator 40 can also be a power source that adjusts the voltage applied between the anode 100 and the cathode 200, and the current flowing between the anode 100 and the cathode 200, in a manner that the power supplied to the water electrolysis device 3 becomes a predetermined set value.

[0110] Based on the above configuration, the water electrolysis device 3 can suppress the increase of overvoltage.

[0111] (Fourth implementation)

[0112] Figure 5 A cross-sectional view is shown schematically for another example of the water electrolysis unit involved in this embodiment.

[0113] The water electrolysis unit involved in this embodiment is, for example, an alkaline water electrolysis unit 4 that utilizes an alkaline aqueous solution. In alkaline water electrolysis, an alkaline aqueous solution can be used. Examples of alkaline aqueous solutions include potassium hydroxide aqueous solution and sodium hydroxide aqueous solution.

[0114] The alkaline water electrolysis unit 4 includes an anode 300 and a cathode 400. The alkaline water electrolysis unit 4 also includes an electrolytic cell 70, a first space 50, and a second space 60. The anode 300 is disposed in the first space 50. The cathode 400 is disposed in the second space 60. The alkaline water electrolysis unit 4 has a diaphragm 41. The diaphragm 41 is disposed inside the electrolytic cell 70, separating the first space 50 from the second space 60. At least one of the anode 300 and the cathode 400 includes an electrode catalyst 1.

[0115] Electrode catalyst 1 may be included in the anode 300. The anode 300 may, for example, include a catalyst layer in which electrode catalyst 1 is included.

[0116] The cathode 400 may contain an electrode catalyst 1. The cathode 400 may, for example, contain a catalyst layer in which the electrode catalyst 1 is contained.

[0117] For example, the diaphragm 41 is a diaphragm used for alkaline water electrolysis.

[0118] The anode 300 can be configured to be in contact with the diaphragm 41, or there can be a gap between the anode 300 and the diaphragm 41. The cathode 400 can be configured to be in contact with the diaphragm 41, or there can be a gap between the cathode 400 and the diaphragm 41.

[0119] The alkaline water electrolysis unit 4 electrolyzes an alkaline aqueous solution to produce hydrogen and oxygen. An aqueous solution containing alkali metal or alkaline earth metal hydroxides can be supplied to the first space 50 of the alkaline water electrolysis unit 4. An alkaline aqueous solution can be supplied to the second space 60 of the alkaline water electrolysis unit 4. Hydrogen and oxygen are produced by electrolysis while discharging alkaline aqueous solutions of a predetermined concentration from both the first space 50 and the second space 60.

[0120] Based on the above configuration, at least one of the anode 300 and cathode 400 contains electrode catalyst 1, thus the alkaline water electrolysis unit 4 can suppress the increase of overvoltage.

[0121] (Fifth Embodiment)

[0122] Figure 6 A cross-sectional view is shown schematically for another example of the water electrolysis apparatus according to this embodiment.

[0123] The water electrolysis apparatus involved in this embodiment is, for example, an alkaline water electrolysis apparatus 5 that utilizes an alkaline aqueous solution. The alkaline water electrolysis apparatus 5 includes an alkaline water electrolysis unit 4 and a voltage applicator 40. The alkaline water electrolysis unit 4 is the same as the alkaline water electrolysis unit 4 in the fourth embodiment, so its description is omitted.

[0124] The voltage applicator 40 is connected to the anode 300 and cathode 400 of the alkaline water electrolysis unit 4. The voltage applicator 40 is a device for applying voltage to the anode 300 and cathode 400 of the alkaline water electrolysis unit 4.

[0125] Based on the above configuration, the alkaline water electrolysis device 5 can suppress the increase of overvoltage.

[0126] Example

[0127] The present disclosure will now be described in more detail through examples. It should be noted that the following examples are only one instance of the present disclosure, and the present disclosure is not limited to the following examples.

[0128] (Example 1)

[0129] (Fabrication of Ni-Fe LDH supported on Ni)

[0130] A mixture containing Ni-Fe LDH and Ni particles was prepared as described below. First, a mixed solvent of water and ethanol (manufactured by Fuji Film and Wako Pure Chemical Industries, reagent grade) was prepared. The volume ratio of water to ethanol was 2:3. In this mixed solvent, nickel chloride hexahydrate (manufactured by Fuji Film and Wako Pure Chemical Industries) and ferric chloride hexahydrate (manufactured by Fuji Film and Wako Pure Chemical Industries) were dissolved such that the total concentration of Ni and Fe ions was 1.0M and the ratio of the amount of Fe ions to the total amount of Ni and Fe ions was 0.33. It should be noted that "M" refers to mol / dm³. 3 Then, acetylacetone (ACAC) was added as a chelating agent in an amount equal to one-third of the total amount of Ni and Fe ions. The resulting solution was stirred for 30 minutes. Ni particles (manufactured by US Research Nanomaterials, Inc., particle size: 40 nm) of the same mass as the Ni-Fe LDH produced if all Ni and Fe contained in the solution had ideally reacted were added to the solution. Next, propylene oxide (POX) was added as a pH-raising agent to the solution containing Ni-Fe LDH and Ni particles in an amount equal to twice the amount of chloride ions in the solution. The resulting solution was stirred for 1 minute. At this time, POX slowly captured hydrogen ions in the solution, thus the pH of the solution slowly increased. Therefore, after the resulting solution was allowed to stand for about 3 days, the mixture of Ni-Fe LDH and Ni particles of the target sample was recovered.

[0131] (The creation of PIM(1))

[0132] The PIM(1) involved in Example 1 was prepared with reference to Non-Patent Document 2. 1 mol equivalent of 4,4'-diamino-3,3'-dimethylbiphenyl was dissolved in 5 mol equivalents of dimethoxymethane. The solution was cooled to 0°C. Next, 120 mol equivalents of trifluoroacetic acid were added dropwise to the solution over 0.5 hours. The mixture was stirred at room temperature for 5 days. Next, the mixture was added to a vigorously stirred aqueous solution of ammonium hydroxide and allowed to stand for 2 hours. The resulting solid was collected by filtration and washed in the order of water, methanol, and acetone.

[0133] After washing, the solid was dissolved in chloroform, and then methanol was added to precipitate the polymer. This operation was repeated twice. The obtained polymer was dried using a vacuum oven to obtain PIM(1) as described in Example 1. PIM(1) is an organic polymer represented by the following structural formula. PIM(1) is an organic polymer with a Trog base backbone.

[0134]

[0135] (Preparation of samples for evaluating catalyst activity)

[0136] PIM(1) was mixed with a mixture of Ni-Fe LDH and Ni particles at a mass ratio of 20:1, with a total mass of 21 mg. 1.05 mL of chloroform (manufactured by Fuji Film and Wako Pure Chemicals Co., Ltd., reagent grade) was added to the resulting mixture to prepare a catalyst ink liquid. The catalyst ink liquid was micronized using an ultrasonic homogenizer for 30 minutes to prepare the catalyst ink according to Example 1. 10 μL of the catalyst ink according to Example 1 was dropped onto a rotating disk electrode and dried at room temperature to obtain a sample for evaluating the catalyst activity according to Example 1.

[0137] (Example 2)

[0138] As an organic binder, PIM(2) was used instead of PIM(1), and otherwise the same procedure was followed as in Example 1 to obtain the sample for evaluating the catalyst activity involved in Example 2. PIM(2) is an organic polymer represented by the following structural formula. PIM(2) is an organic polymer having a Trog base skeleton.

[0139]

[0140] (Example 3)

[0141] As an organic binder, PIM(3) was used instead of PIM(1), and otherwise the same procedure was followed as in Example 1 to obtain the sample for evaluating the catalyst activity involved in Example 3. PIM(3) is an organic polymer represented by the following structural formula. PIM(3) is an organic polymer having a Trog base skeleton.

[0142]

[0143] (Example 4)

[0144] As an organic binder, PIM(4) was used instead of PIM(1), and otherwise the same procedure was followed as in Example 1 to obtain the sample for evaluating the catalyst activity involved in Example 4. PIM(4) is an organic polymer represented by the following structural formula. PIM(4) is an organic polymer having a Trog base skeleton.

[0145]

[0146] (Example 5)

[0147] (Preparation of Ni-Fe LDH supported on Ketjenblack substrate)

[0148] Ni-Fe LDH was prepared as described below. First, a mixed solvent of water and ethanol (manufactured by Fuji Film and Wako Pure Chemical Industries, premium reagent grade) was prepared. The volume ratio of water to ethanol was 2:3. In this mixed solvent, nickel chloride hexahydrate (manufactured by Fuji Film and Wako Pure Chemical Industries) and ferric chloride hexahydrate (manufactured by Fuji Film and Wako Pure Chemical Industries) were dissolved such that the total concentration of Ni ions and Fe ions was 1.0M and the ratio of the amount of Fe ions to the total amount of Ni ions and Fe ions was 0.33. It should be noted that "M" refers to mol / dm³. 3 Then, acetylacetone (ACAC) as a chelating agent was added in an amount equal to one-third of the total amount of Ni and Fe ions. The resulting solution was stirred for 30 minutes. Next, propylene oxide (POX) as a pH-raising agent was added in an amount twice the amount of chloride ions in the solution, and the mixture was stirred for 1 minute. At this time, POX slowly captured hydrogen ions in the solution, thus slowly increasing the pH. Therefore, after standing for approximately 3 days, the LDH of the target sample was recovered. It should be noted that the above method for LDH modulation is an example and is not limited to this example. Here, the particle size distribution of Ni-Fe LDH dispersed in the solution was obtained using the small-angle X-ray scattering (SAXS) method of SmartLab manufactured by Rigaku Corporation. The relationship between the obtained particle size and distribution was represented by a two-dimensional distribution graph, and the average particle size of the LDH was determined by dividing the area of ​​the two-dimensional distribution graph by the total number of particles. The average particle size of Ni-Fe LDH was 10 nm.

[0149] Ketjen Black EC600JD manufactured by Lion Special Ketjenza was mixed into the obtained Ni-Fe LDH at a Ni-Fe LDH:Ketjen Black mass ratio of 2:1 and a total mass of 8.5 mg to prepare Ni-Fe LDH supported on a Ketjen Black support. In Example 5, Ni-Fe LDH supported on a Ketjen Black support was used, and the procedure was otherwise the same as in Example 1 to obtain the sample for evaluating the catalyst activity involved in Example 5.

[0150] (Example 6)

[0151] IrO produced by Tanaka Precious Metals Co., Ltd. x SA100 is used to replace the mixture of Ni-Fe LDH and Ni particles, and IrO is used. xThe mixture was prepared in a mass ratio of 5:1 with PIM(1) and a total mass of 6 mg. Otherwise, the same procedure as in Example 1 was followed to obtain the catalyst activity evaluation sample involved in Example 6.

[0152] (Comparative Example 1)

[0153] As an organic binder, Sustainion manufactured by Dioxide Materials was used instead of PIM (1). Otherwise, the procedure was the same as in Example 1 to obtain the sample for evaluating the catalyst activity involved in Comparative Example 1.

[0154] (Comparative Example 2)

[0155] As an organic binder, FAA-3 manufactured by Fumatech was used instead of PIM (1), and 1.03 mL of chloroform was used. Otherwise, the same procedure as in Example 1 was followed to obtain the sample for evaluating the catalyst activity involved in Comparative Example 2.

[0156] (Evaluation of catalyst overvoltage)

[0157] The overvoltage of the samples used to evaluate the catalyst activity of each example and comparative example was measured. A Princeton Applied Research VersaSTAT4 potentiostat and a Pine Research AFE3T050GC rotating electrode were used in the measurements. The current originating from the anodic reaction of the water electrolysis unit was measured using the rotating disk electrode (RDE) method under the following conditions. The anodic reaction was the oxygen evolution reaction. The results are shown in Table 1.

[0158] [Measurement Conditions]

[0159] Solution: 1M KOH solution

[0160] Potential: 1.0V to 1.65V (vs. Reversible hydrogen electrode (RHE))

[0161] • Potential scan rate: 10mV / sec

[0162] • Electrode rotation speed: 1500 revolutions per minute (rpm)

[0163] [Table 1]

[0164]

[0165] Table 1 shows the overvoltage measurement results of the samples used to evaluate the catalyst activity of Examples 1 to 6, Comparative Examples 1 and 2. Table 1 shows the overvoltage in the first cycle of the redox reaction.

[0166] The catalyst inks described in Examples 1 to 6 exhibit low overvoltages during redox cycles. As a result, the increase in overvoltage is suppressed in the catalyst inks described in Examples 1 to 6. The inherently microporous polymer used as an organic binder in Examples 1 to 6 is porous, thus allowing the catalyst to be exposed from the inherently microporous polymer. It is believed that this suppresses the increase in overvoltage in the catalyst inks described in Examples 1 to 6. Furthermore, the catalyst ink described in Example 6 exhibits low overvoltages during redox cycles. It is evident that even when IrO is used as a conductive catalyst material... x In this case, the catalyst ink also has a low overvoltage.

[0167] On the other hand, the catalyst inks involved in Comparative Examples 1 and 2 exhibit high overvoltages. In the catalyst inks involved in Comparative Examples 1 and 2, porous organic binders were not used. Therefore, it is believed that the organic binder covers the catalyst material, thereby reducing the catalyst activity.

[0168] Industry availability

[0169] The electrode catalyst of the water electrolysis unit disclosed herein can be used in a water electrolysis device.

[0170] Explanation of reference numerals in the attached figures

[0171] 1 Electrode catalyst

[0172] 2 Water Electrolysis Unit

[0173] 3 Water Electrolysis Unit

[0174] 4 Alkaline water electrolysis units

[0175] 5. Alkaline water electrolysis device

[0176] 10 catalysts

[0177] 11. Inherently Microporous Polymers (PIMs)

[0178] 20LDH

[0179] 21 Main Layer

[0180] 22 Object Layer

[0181] 30, 32 catalyst layers

[0182] 31 Electrolyte Membrane

[0183] 33, 34 Gas diffusion layers

[0184] 40 voltage applicator

[0185] 41 Diaphragm

[0186] 50 First Space

[0187] 60 Second Space

[0188] 70 electrolytic cells

[0189] 100, 300 anode

[0190] 200, 400 cathode

Claims

1. An electrode catalyst for a water electrolysis unit, comprising: catalyst, and Neutral, inherently microporous polymers The catalyst is a layered double hydroxide or a metal oxide. The neutral, inherently microporous polymer has a Trog base framework. The neutral, inherently microporous polymer is mixed with the catalyst as a binder.

2. A water electrolysis unit, comprising: anode, cathode, and An electrolyte membrane disposed between the anode and the cathode, At least one of the group consisting of the anode and the cathode comprises the electrode catalyst of claim 1.

3. The water electrolysis unit according to claim 2, wherein the electrolyte membrane comprises a proton exchange membrane.

4. The water electrolysis unit according to claim 2, wherein the electrolyte membrane comprises an anion exchange membrane.

5. A water electrolysis unit, comprising: The membrane separating the first space from the second space The anode and the anode set in the first space The cathode is set in the second space. At least one of the group consisting of the anode and the cathode comprises the electrode catalyst of claim 1.

6. A water electrolysis apparatus, comprising: The water electrolysis unit and voltage applicator as described in any one of claims 2 to 5 The voltage applicator is connected to the anode and the cathode and applies a voltage between the anode and the cathode.

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