Electrodes for water electrolysis, water electrolysis cells, and water electrolysis apparatus

Abstract

This invention provides a novel electrode for water electrolysis that is advantageous in that it exhibits high performance when water electrolysis is performed at high temperatures. [Solution] The water electrolysis electrode 1 comprises a conductive substrate 10 and a layered double hydroxide (LDH) layer 20. The conductive substrate 10 contains Ni. The LDH layer 20 is provided on the conductive substrate 10 and contains Ni. In the diffraction pattern of the microangle incident X-ray diffraction (GIXD) measurement of the water electrolysis electrode 1, the relative r 110 / Ni111 The ratio is between 0.0030 and 0.0050. 110 / Ni111 This is the ratio of the intensity of the diffraction peak of the LDH(110) plane to the intensity of the diffraction peak of the Ni(111) plane.

Description

Technical Field

[0001] The present disclosure relates to an electrode for water electrolysis, a water electrolysis cell, and a water electrolysis apparatus.

Background Art

[0002] In recent years, the development of electrodes for water electrolysis used in water electrolysis apparatuses has been expected.

[0003] Patent Document 1 describes a method for manufacturing an electrode for electrolysis of water, including a step of immersing an electrode substrate containing a predetermined layered double hydroxide in an organic solvent. In this manufacturing method, the electrode substrate is manufactured by performing an electrodeposition treatment in an aqueous solution containing a compound containing metal M1 and a compound containing metal M2 with a conductive substrate as an anode.

[0004] Patent Document 2 describes an oxygen generation catalyst including a graphene oxide layer and a nickel-iron layered double hydroxide layer supported on the surface of the graphene oxide layer, wherein the average thickness of the graphene oxide layer is 0.33 to 4 nm.

[0005] In Non-Patent Document 1, the activity of the oxygen evolution reaction (OER) of an electrode of Ni-Fe layered double hydride (Ni-Fe LDH) has been studied.

[0006] Non-Patent Document 2 describes that the interfacial interaction between FeOOH and Ni-Fe LDH adjusts the local electronic structure of Ni-Fe LDH and enhances the OER electrode catalysis.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0008] [Non-Patent Document 1] Seyeong Lee et al., “Operational durability of three-dimensional Ni-Fe layered double hydroxide electrocatalyst for water oxidation,” Electrochimica Acta, 2019, Vol.315, p.94-101 [Non-Patent Document 2] Jiande Chen et al., “Interfacial Interaction between FeOOH and Ni-Fe LDH to Modulate the Local Electronic Structure for Enhanced OER Electrocatalysis,” ACS Catalysis, 2018, Vol.8, p.11342-11351 [Summary of the Invention] [Problems to be Solved by the Invention]

[0009] The descriptions in the above documents have room for reconsideration from the viewpoint of exhibiting high performance when the temperature at which water electrolysis is performed is high. Therefore, the present disclosure provides a novel electrode for water electrolysis that is advantageous from the viewpoint of exhibiting high performance when the temperature at which water electrolysis is performed is high. [Means for Solving the Problems]

[0010] The present disclosure provides an electrode for water electrolysis, comprising a conductive substrate containing Ni, and a layered double hydroxide layer containing Ni provided on the conductive substrate, and in the diffraction pattern of the small-angle incident X-ray diffraction measurement of the electrode for water electrolysis, the ratio of the intensity of the diffraction peak of the layered double hydroxide (110) plane to the intensity of the diffraction peak of the Ni(111) plane is 0.0030 or more and 0.0050 or less. We provide electrodes for water electrolysis. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide a novel electrode for water electrolysis that is advantageous in that it exhibits high performance when the temperature at which water electrolysis is performed is high. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a cross-sectional view showing an example of a water electrolysis electrode according to the present disclosure. [Figure 2] Figure 2 is a plan view showing an example of a conductive substrate. [Figure 3] Figure 3 is a schematic diagram showing an example of the crystal structure of a layered double hydroxide (LDH). [Figure 4] Figure 4 is a schematic diagram illustrating an example of the manufacturing mechanism of electrodes for water electrolysis. [Figure 5] Figure 5 is a cross-sectional view showing an example of a water electrolysis cell according to the present disclosure. [Figure 6] Figure 6 is a cross-sectional view showing an example of a water electrolysis apparatus according to the present disclosure. [Figure 7] Figure 7 is a cross-sectional view showing another example of a water electrolysis cell according to the present disclosure. [Figure 8] Figure 8 is a cross-sectional view showing another example of a water electrolysis apparatus according to the present disclosure. [Figure 9A] Figure 9A is a graph showing the diffraction pattern of the electrode measured by micro-angle incident X-ray diffraction (GIXD) according to Example 1. [Figure 9B] Figure 9B is a graph showing the diffraction pattern of the electrode according to Example 2 obtained by GIXD measurement. [Figure 9C] Figure 9C is a graph showing the diffraction pattern of the electrode according to Example 3 obtained by GIXD measurement. [Figure 9D] Figure 9D is a graph showing the diffraction pattern of the electrode according to Example 4 obtained by GIXD measurement. [Figure 9E] Figure 9E is a graph showing the diffraction pattern of the electrode according to Comparative Example 1 obtained by GIXD measurement. [Figure 9F] Figure 9F is a graph showing the diffraction pattern of the electrode according to Comparative Example 2 obtained by GIXD measurement. [Figure 9G] Figure 9G is a graph showing the diffraction pattern of the electrode according to Comparative Example 3 obtained by GIXD measurement. [Modes for carrying out the invention]

[0013] (Knowledge that forms the basis of this disclosure) As a measure against global warming, the use of renewable energy sources such as solar and wind power is attracting attention. However, a problem arises with renewable energy generation: surplus electricity goes to waste. Therefore, the utilization efficiency of renewable energy is not always sufficient. As a result, methods are being considered to effectively utilize surplus electricity by producing and storing hydrogen from it.

[0014] Electrolysis of water is a possible method for producing hydrogen from surplus electricity. To produce hydrogen cheaply and stably, there is a need for the development of highly efficient and long-lasting water electrolysis devices. In a water electrolysis device, oxygen is produced at the anode and hydrogen at the cathode. The reaction in which oxygen is produced at the anode is called the anodic reaction, and the reaction in which hydrogen is produced at the cathode is called the cathode reaction. To provide a highly efficient water electrolysis device, it is desirable to have low overvoltage at the anode. It is also desirable to have low overvoltage at the cathode. Therefore, the development of high-performance electrodes for the anodic or cathode reaction in water electrolysis is highly anticipated.

[0015] For example, LDH is considered promising as a material for water electrolysis electrodes due to its large specific surface area and diverse combinations of metal ions. According to Patent Document 1, an electrode substrate containing a predetermined LDH is manufactured by electrodeposition treatment in an aqueous solution containing a compound containing metal M1 and a compound containing metal M2, with a conductive substrate as the anode. Patent Document 1 evaluates the performance of the electrode at room temperature. Patent Document 1 does not evaluate the performance of the electrode at temperatures higher than room temperature.

[0016] This disclosure has been made in view of the problems of the prior art. The objective of this disclosure is to provide a novel water electrolysis electrode that is advantageous in terms of exhibiting high performance when the temperature at which water electrolysis is performed is high. Through diligent research, the inventors have newly discovered that having a water electrolysis electrode containing an LDH layer in a predetermined state is advantageous in terms of exhibiting high performance when the temperature at which water electrolysis is performed is high, and have completed the water electrolysis electrode of this disclosure.

[0017] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below. The embodiments described below are all comprehensive or specific examples. Therefore, the numerical values, shapes, materials, components, arrangement positions of components, and connection configurations shown in the embodiments below are examples and are not intended to limit this disclosure. In addition, components in the embodiments below that are not described in an independent claim indicating the highest-level concept will be described as optional components. Also, in the drawings, components with the same reference numerals may not be described. Furthermore, the drawings are schematic representations of each component for ease of understanding, and the shapes and dimensional ratios may not be accurately represented.

[0018] (First Embodiment) Figure 1 is a cross-sectional view showing a water electrolysis electrode according to the first embodiment. As shown in Figure 1, the water electrolysis electrode 1 comprises a conductive substrate 10 and a layered double hydroxide (LDH) layer 20. The conductive substrate 10 contains Ni. The LDH layer 20 is provided on the conductive substrate 10 and contains Ni. The LDH layer 20 is bonded to the conductive substrate 10. The LDH layer 20 is directly bonded to the surface of the conductive substrate 10 without an adhesive containing an organic material such as a polymer. In the diffraction pattern of the water electrolysis electrode 1 measured by micro-angle incident X-ray diffraction (GIXD), the relative r 110 / Ni111 The ratio is between 0.0030 and 0.0050. 110 / Ni111This is the ratio of the intensity of the diffraction peak of the LDH(110) plane to the intensity of the diffraction peak of the Ni(111) plane. With this configuration, the water electrolysis electrode 1 tends to exhibit high performance when the temperature at which water electrolysis is performed is high (for example, from 70°C to 90°C).

[0019] ratio 110 / Ni111 It is believed that the LDH crystal growth in the direction perpendicular to the LDH(110) plane is adjusted to the desired state when the value is between 0.0030 and 0.0050, thereby allowing the LDH layer 20 to be formed. As a result, the LDH layer 20 is considered to be in an advantageous state from the viewpoint of exhibiting high performance when the temperature at which water electrolysis is performed is high.

[0020] ratio 110 / Ni111 Preferably, this value is between 0.0034 and 0.0047. In this case, the water electrolysis electrode 1 is more likely to exhibit high performance when the temperature at which water electrolysis is performed is high.

[0021] ratio 110 / Ni111 More preferably, this value is between 0.0038 and 0.0047. In this case, the water electrolysis electrode 1 is more likely to exhibit high performance when the temperature at which water electrolysis is performed is high.

[0022] ratio 110 / Ni111 More preferably, this value is between 0.0043 and 0.0047. In this case, the water electrolysis electrode 1 is more likely to exhibit high performance when the temperature at which water electrolysis is performed is high.

[0023] The conductive substrate 10 is not limited to a specific substrate as long as it contains Ni and is conductive. The conductive substrate 10 may contain metals other than Ni, or it may contain resin. The entire conductive substrate 10 may be made of metal. The conductive substrate 10 may have a configuration in which a surface layer containing metal is formed on a resin component such as polypropylene and polyethylene. In this case, the surface layer containing metal may be a plated film or a sputtered film. The metal contained in the conductive substrate 10 may be a pure metal such as Ni and Fe, or an alloy such as stainless steel and Inconel. Inconel is a registered trademark.

[0024] The surface of the conductive substrate 10 is preferably made of Ni. In this case, the conductive substrate 10 tends to have high alkali resistance. When the surface of the conductive substrate 10 is made of Ni, the entire conductive substrate 10 may be made of Ni, or the conductive substrate 10 may have a surface layer made of Ni. The surface layer made of Ni is, for example, a sputtering film or a plating film.

[0025] When the surface of the conductive substrate 10 is made of Ni, the purity of the Ni forming the surface is not limited to a specific value. For example, the purity is 90% by mass or higher. In this case, the conductive substrate 10 is more likely to have high alkali resistance. The method for determining the purity of the Ni forming the surface of the conductive substrate 10 is not limited to a specific method. The purity of the Ni forming the surface of the conductive substrate 10 may be determined by elemental analysis such as X-ray fluorescence spectroscopy (XRF) and energy-dispersive X-ray spectroscopy (EDX). The purity of the Ni forming the surface of the conductive substrate 10 may also be determined by analyzing the extract obtained by completely dissolving the conductive substrate 10 in aqua regia using a method such as inductively coupled plasma atomic emission spectroscopy (ICP-AES). If the purity of Ni is high, the purity of the Ni forming the surface of the conductive substrate 10 may be determined by comparing the specific gravity of the conductive substrate 10 with the specific gravity of pure Ni.

[0026] The purity of Ni forming the surface of the conductive substrate 10 is preferably 95% by mass or more, more preferably 97% by mass or more, even more preferably 98% by mass or more, and particularly preferably 99% by mass or more.

[0027] Figure 2 is a plan view showing an example of a conductive substrate. As shown in Figure 2, the conductive substrate 10 has, for example, a mesh structure. The conductive substrate 10 is, for example, in the form of a sheet and has a plurality of openings 10h arranged along the main surface of the conductive substrate 10. With such a configuration, the water electrolysis electrode 1 is more likely to exhibit high performance when the temperature at which water electrolysis is performed is high.

[0028] In a plan view of the conductive substrate 10, the multiple openings 10h are arranged, for example, regularly. Each of the multiple openings 10h extends, for example, from one main surface to the other main surface of the conductive substrate 10. Examples of conductive substrates 10 having a mesh structure are expanded metal and mesh.

[0029] The conductive substrate 10 may have a non-porous structure such as a plate or foil, or it may be perforated metal, or it may have a porous structure such as a foam or nonwoven fabric. When the conductive substrate 10 has a plurality of openings 10h or a porous structure, the surface area of ​​the conductive parts of the conductive substrate 10 tends to be large, and the gas generated in the water electrolysis reaction diffuses easily.

[0030] The thickness of the conductive substrate 10 is not limited to a specific value. Its thickness is, for example, 0.02 mm or more. In this case, the conductive substrate 10 is easier to handle. The thickness of the conductive substrate 10 is, for example, 10 mm or less, and preferably 1 mm or less.

[0031] The thickness of the LDH layer 20 is not limited to a specific value. The thickness of the LDH layer 20 is, for example, 35 nm or more. With such a configuration, the electrode 1 for water electrolysis is likely to have high electrode activity. The LDH layer 20 includes, for example, a portion having a thickness of 35 nm or more. The thickness of the LDH layer 20 is, for example, 4000 nm or less. The thickness of the LDH layer 20 can be determined, for example, by transmission electron microscope (TEM) observation of the cross-section of the electrode 1 for water electrolysis.

[0032] The LDH layer 20 covers, for example, the surface of the conductive substrate 10. The coverage rate of the LDH layer 20 on the surface of the conductive substrate 10 is not limited to a specific value. The coverage rate is preferably 99% or more. In this case, the electrode 1 for water electrolysis is likely to have high electrode activity.

[0033] FIG. 3 is a diagram schematically showing an example of the crystal structure of LDH. The LDH 20a contained in the LDH layer 20 is active with respect to the gas generation reaction such as hydrogen and oxygen in the anode or cathode of water electrolysis. For example, the LDH 20a can change to a hydroxide in alkaline water electrolysis.

[0034] The LDH 20a has, for example, a composition represented by the following formula (1). In 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 required amount of charge balance. n is an integer. m is an appropriate rational number. [M1 2+ 1-x M2 3+ x (OH)2][yA n- ·mH2O] Formula (1)

[0035] The LDH 20a may contain two or more types of transition metals. The two or more types of transition metals in the LDH 20a are not limited to specific transition metals. In other words, M1 and M2 in the composition shown in formula (1) are not limited to specific transition metals.

[0036] The LDH layer 20, for example, contains Ni, plus at least one selected from the group consisting of V, Cr, Mn, Fe, Co, Cu, W, and Ru. In this case, the water electrolysis electrode 1 is likely to have high electrode activity.

[0037] The LDH layer 20 preferably contains Fe in addition to Ni. In this case, the water electrolysis electrode 1 is likely to have high electrode activity. In addition, the manufacturing cost of the water electrolysis electrode 1 is likely to be lower. For example, in the composition shown in formula (1), M1 may be Ni and M2 may be Fe. In this case, the water electrolysis electrode 1 is even more likely to have high electrode activity.

[0038] In LDH20a, the interlayer anion A n- This can be an inorganic ion or an organic ion. An example of an inorganic ion is CO3. 2- NO3 - Cl - SO4 2- , Br - , OH - F - , I - Si2O5 2- B4O5(OH)4 2- , and PO4 3- An example of an organic ion is CH3(CH2). n SO 4- CH3(CH2) n COO - CH3(CH2) n PO 4- , and CH3(CH2) n NO 3- A n- It can be inserted between layers of metal hydroxide along with water molecules. n- The charge and ion size are not limited to specific values. LDH20a is one type A n- It may include multiple types of A n- It may include.

[0039] As shown in Figure 3, LDH20a is M1 2+or M2 3+ At each vertex of an octahedron centered at OH - It contains ions. LDH20a contains [M1 2+ 1-x M2 3+ x (OH)2] x+ It contains metal hydroxides represented by . These metal hydroxides have a layered structure in which octahedrons of hydroxide are linked together in two dimensions, sharing edges. Between the layers of metal hydroxide are anions A n- and water molecules are present. The metal hydroxide layer functions as the host layer 21, and anion A n- And a guest layer 22 containing water molecules is placed between the host layers 21. In other words, LDH20a as a whole consists of a host layer 21 of metal hydroxide and anion A n- It has a sheet-like structure in which the guest layer 22 of water molecules and the metal hydroxide are alternately stacked. LDH20a contains M1 2+ Part of M2 3+ It has a structure that has been replaced by [this].

[0040] The crystal structure and crystallinity of LDH20a can be qualitatively and quantitatively analyzed by X-ray diffraction (XRD) measurement. When the LDH layer 20 is thin, the signal becomes weak and analysis becomes difficult, so it is more preferable to analyze it qualitatively and quantitatively by micro-angle incident X-ray diffraction (GIXD) measurement. In GIXD measurement, for example, CuKα rays are used. The angle between the incident X-ray and the sample surface is fixed at 3°, and the water electrolysis electrode 1 is rotated horizontally 360°, and the diffraction peak intensity originating from the (111) plane of Ni contained in the conductive substrate 10 that appears in the diffraction angle range 2θ from 42° to 46° is measured. The diffraction pattern of the water electrolysis electrode 1 is measured in the plane direction of the water electrolysis electrode 1 where the diffraction peak intensity originating from the Ni(111) plane is at its maximum intensity. In this diffraction pattern, for example, diffraction peaks originating from the (003), (012), (015), and (110) planes of LDH20a are obtained in the diffraction angle 2θ ranges of 10° to 12°, 33° to 36°, 38° to 40°, and 59° to 61°, respectively. The peak intensity of each diffraction peak is determined as the height from the baseline of each diffraction peak.

[0041] The crystallite size of LDH20a is not limited to a specific value. For example, the crystallite size of LDH20a is between 5 nm and 15 nm. In this case, the water electrolysis electrode 1 tends to exhibit higher performance when the temperature at which water electrolysis is performed is high. The crystallite size of LDH20a is calculated, for example, based on Scherrer's formula in equation (2) below, according to the method described in the examples. In equation (2), D is the crystallite size [nm], K is the Scherrer constant, λ is the wavelength of X-rays [nm], B is the diffraction line width broadening [rad], and θ is the Bragg angle [rad]. D=Kλ / Bcosθ Equation (2)

[0042] The LDH layer 20 contains, for example, a chelating agent. The chelating agent may be coordinated to the transition metal ions contained in LDH20a. This allows LDH20a to exist stably in the LDH layer 20. In addition, LDH20a is easily synthesized to have a small particle size. Furthermore, because the nucleated LDH20a on the conductive substrate 10 tends to grow slowly, a dense LDH layer 20 with few voids containing LDH20a tends to be firmly fixed to the conductive substrate 10 with the desired thickness. As a result, the LDH layer 20 tends to contribute effectively to the anode or cathode reaction, and the water electrolysis electrode 1 tends to have high electrode activity.

[0043] The chelating agent is not limited to any particular chelating agent. A chelating agent is, for example, an organic compound that can coordinate to transition metal ions in LDH20a. The chelating agent may be at least one selected from the group consisting of bidentate organic ligands and tripidentate organic ligands. Examples of chelating agents are β-diketones, β-ketoesters, hydroxycarboxylic acids, and hydroxycarboxylate salts. Examples of β-diketones are acetylacetone (ACAC), trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, tenoyltrifluoroacetone, dipyrobilmethane, dibenzoylmethane, and ascorbic acid. Examples of β-ketoesters are methyl acetoacetate, ethyl acetoacetate, allyl acetoacetate, benzyl acetoacetate, n-propyl acetoacetate, iso-propyl acetoacetate, n-butyl acetoacetate, iso-butyl acetoacetate, tert-butyl acetoacetate, 2-methoxyethyl acetoacetate, and methyl 3-oxopentanoate. 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. An example of a citrate is trisodium citrate.

[0044] The chelating agent preferably includes at least one selected from the group consisting of acetylacetone and citrate. In this case, the water electrolysis electrode 1 is more likely to have high electrode activity.

[0045] The method for manufacturing the water electrolysis electrode 1 is not limited to a specific method. The water electrolysis electrode 1 can be manufactured, for example, by immersing a conductive substrate 10 in a solution containing a chelating agent and two or more transition metal ions, and then adjusting the solution to be alkaline. With such a method, for example, an LDH layer 20 containing LDH 20a and a chelating agent can be formed on the conductive substrate 10 in a simple manner.

[0046] The temperature of the solution when adjusting it to an alkaline state is not limited to a specific temperature. For example, the temperature of the solution can be room temperature, 20°C ± 15°C. In this case, a water electrolysis electrode 1 with high electrode activity is easily obtained.

[0047] The solvent in the solution may be water, an organic solvent, or a mixed solvent of water and an organic solvent.

[0048] The method for manufacturing the water electrolysis electrode 1 preferably includes increasing the pH of the above solution. This allows the LDH layer 20 to be formed on the conductive substrate 10 in a short period of time, making it easier to obtain a water electrolysis electrode 1 with high electrode activity.

[0049] The method for adjusting the solution to be alkaline is not limited to any particular method. For example, the solution may be adjusted to be alkaline by mixing the above solution with an alkaline solution. Alternatively, the solution may be adjusted to be alkaline by adding a pH-raising agent to the above solution. In this case, the pH-raising agent is not limited to any particular compound. A pH-raising agent is, for example, a compound having an epoxy group. Examples of pH-raising agents are propylene oxide, ethylene oxide, butylene oxide, and glycidol.

[0050] When a pH-raising agent containing an epoxy group, such as propylene oxide, is added to a solution, hydrogen ions present in the solution can be captured by the pH-raising agent through a ring-opening reaction of the epoxy group in the presence of a nucleophile such as chloride ions. This can raise the pH of the solution, making it alkaline. The pH-raising agent is preferably glycidol. When glycidol is used, the ring-opening compound of glycidol interacts with transition metal ions, making it easier to form LDH with the desired crystalline properties. As a result, the water electrolysis electrode 1 tends to exhibit higher performance when the temperature at which water electrolysis is performed is high. From the standpoint of manufacturing safety, glycidol has a higher flash point than other epoxides, making it less flammable and safer. Therefore, the use of glycidol eliminates the need for explosion-proof specifications in the manufacturing equipment, which tends to lower the cost of the manufacturing equipment.

[0051] When a pH-raising agent is added to the above solution, the pH of the solution gradually increases, for example, from 1, and the solution may eventually become alkaline. The final pH of the solution may be, for example, between 8 and 12. The addition of the pH-raising agent to the solution triggers a reaction in which hydrogen ions in the solution are captured. This causes the pH of the solution to gradually increase. The time it takes for the pH of the solution to reach a steady state after the addition of the pH-raising agent is not limited to a specific time. This time can be, for example, more than one hour, or several days.

[0052] The two or more transition metal ions contained in the solution are not limited to specific transition metal ions. For example, the two or more transition metal ions contained in the solution are at least two transition metal ions selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, W, and Ru. In this case, it is easier to manufacture a water electrolysis electrode 1 with high electrode activity.

[0053] The solution preferably contains two or more transition metal ions, including at least one transition metal ion selected from the group consisting of Ni and Fe. In this case, a water electrolysis electrode 1 with high electrode activity is more easily manufactured.

[0054] As described above, the surface of the conductive substrate 10 is preferably made of Ni. In this case, for example, it is easier to manufacture an electrode for water electrolysis that has advantageous properties from the viewpoint of achieving both corrosion resistance and conductivity in alkaline water electrolysis.

[0055] As described above, the conductive substrate 10 contains Ni. The solution contains two or more transition metal ions, preferably Fe ions. The solution preferably contains chloride ions. In this case, the reaction shown in formula (3) may occur. This may etch the conductive substrate 10. The method for manufacturing the water electrolysis electrode 1 preferably includes promoting the mixing of the solution before adjusting the solution to alkaline while the conductive substrate 10 is immersed in it. Promoting the mixing of the solution can be done, for example, by vibrating the conductive substrate 10, shaking the container containing the solution and the conductive substrate 10, or stirring the solution using a stirrer piece and a stirrer. Such methods can cause forced convection of the solution and promote the mixing of the solution. This may etch the conductive substrate 10 to the desired state and form the LDH layer 20 on the conductive substrate 10 to the desired state. As a result, the water electrolysis electrode 1 is likely to have high durability. Note that promoting the mixing of the solution may be done with the container containing the solution and the conductive substrate 10 sealed, or under an inert gas atmosphere. 4Ni 2+ Cl - 2 + 2Fe 3+ Cl - 3+ 2Ni → 5Ni 2+ Cl - 2 + 2Fe 2+ Cl - 2+ 1Ni Equation (3)

[0056] For example, the molar ratio of the chelating agent to the Fe ion content in the solution, the concentration of chloride ions in the solution, and the molar ratio of the Ni ion content to the Fe ion content in the solution are adjusted. This adjusts the ratio r 110 / Ni111 It is likely to be adjusted to between 0.0030 and 0.0050.

[0057] In the manufacture of the water electrolysis electrode 1, the molar ratio of Fe ions to Ni in the conductive substrate 10 is not limited to a specific value. For example, the molar ratio is 0.75 or less. In this case, it is possible to prevent the Ni in the conductive substrate 10 from dissolving due to the reaction shown in equation (3), which would make the manufacture of the water electrolysis electrode 1 difficult.

[0058] The above molar ratio is preferably between 0.05 and 0.25. In this case, the LDH layer 20 is more easily formed uniformly on the conductive substrate 10, and the water electrolysis electrode 1 is more likely to have high electrode activity.

[0059] The chelating agent included in the solution may be selected with reference to the above examples of chelating agents included in the LDH layer 20. Preferably, the chelating agent included in the solution contains at least one selected from the group consisting of acetylacetone and citrate. This increases the stability of the dispersion of the complex in the solution, making it easier for the LDH layer 20 to form in the desired state on the water electrolysis electrode 1. As a result, the water electrolysis electrode 1 is more likely to have high electrode activity.

[0060] Figure 4 schematically illustrates the mechanism of manufacturing electrodes for water electrolysis. As shown in Figure 4, a conductive substrate 10 is immersed in a solution containing transition metal ions TM1, transition metal ions TM2, and a chelating agent CH. For example, transition metal ions TM1 are nickel ions, and transition metal ions TM2 are iron ions. In addition, nickel is present on the surface of the conductive substrate 10. Some of the transition metal ions TM2 etch and dissolve the nickel present on the surface of the conductive substrate 10. Some of the chelating agent CH reacts with the surface of the conductive substrate 10, forming a complex C1 between the transition metal ions TM1 derived from the conductive substrate 10 and the chelating agent CH. Furthermore, when the solution is adjusted to be alkaline, a complex C1 derived from the transition metal ions TM1 derived from the solution and the chelating agent CH is formed in the solution, and a complex C2 between the transition metal ions TM2 and the chelating agent CH is formed. Next, complexes C1 and C2 react on the surface of the conductive substrate, and LDH20a is synthesized along the surface of the conductive substrate 10. In addition, since complexes C1 and C2 contain the chelating agent CH, the crystal growth of LDH20a is suppressed. As a result, an LDH layer 20 containing LDH20a and the chelating agent CH is formed on the conductive substrate 10, and an electrode 1 for water electrolysis is obtained.

[0061] The water electrolysis electrode 1 according to this embodiment can be used, for example, as an electrode in the water electrolysis cell of an alkaline water electrolysis apparatus or an anion exchange membrane type water electrolysis apparatus. The water electrolysis electrode 1 is used, for example, in at least one selected from the group consisting of anode and cathode in these water electrolysis apparatuses. This tends to increase the activity of the anodic or cathode reaction of water electrolysis.

[0062] (Second Embodiment) Figure 5 is a schematic cross-sectional view showing an example of a water electrolysis cell according to the second embodiment. As shown in Figure 5, the water electrolysis cell 2 comprises an anode 2a, a cathode 2b, and a diaphragm 2p. At least one selected from the group consisting of anode 2a and cathode 2b includes, for example, the water electrolysis electrode 1 according to the first embodiment. In this case, the overvoltage tends to be low when the temperature at which water electrolysis is performed is high, and the anode 2a or cathode 2b tends to exhibit high performance.

[0063] Water electrolysis cell 2 is, for example, an alkaline water electrolysis cell that uses an alkaline aqueous solution. The alkaline aqueous solution used in water electrolysis cell 2 is not limited to a specific alkaline aqueous solution. Examples of alkaline aqueous solutions are potassium hydroxide aqueous solution and sodium hydroxide aqueous solution.

[0064] As shown in Figure 5, the water electrolysis cell 2 comprises, for example, an electrolytic cell 2s, a first chamber 2m, and a second chamber 2n. The diaphragm 2p is located inside the electrolytic cell 2s, dividing the inside of the electrolytic cell 2s into the first chamber 2m and the second chamber 2n. The anode 2a is located in the first chamber 2m, and the cathode 2b is located in the second chamber 2n.

[0065] The diaphragm 2p is, for example, a diaphragm for alkaline water electrolysis. The diaphragm 2p is, for example, a sheet-like porous membrane. The diaphragm 2p has a thickness of, for example, 100 μm to 500 μm and has pores that serve as passages for ions or electrolytes. The material of the diaphragm 2p is not limited to a specific material. Examples of materials for the diaphragm 2p are asbestos, polymer-reinforced asbestos, potassium titanate bonded with polytetrafluoroethylene (PTFE), zirconia bonded with PTFE, and antimony acid and antimony oxide bonded with polysulfone. Another example of materials for the diaphragm 2p is sintered nickel, nickel coated with ceramics and nickel oxide, and polysulfone. The diaphragm 2p may also be Zirfon Perl UTP 500 manufactured by AGFA.

[0066] The anode 2a may be positioned in a zero-gap state, in contact with the diaphragm 2p, or it may be positioned with a gap between it and the diaphragm 2p. The cathode 2b may be positioned in contact with the diaphragm 2p, or it may be positioned with a gap between it and the diaphragm 2p.

[0067] The water electrolysis cell 2 produces hydrogen and oxygen by electrolyzing an alkaline aqueous solution. An aqueous solution containing an alkali metal or alkaline earth metal hydroxide is supplied to the first chamber 2m. In addition, an alkaline aqueous solution may be supplied to the second chamber 2n. Electrolysis is performed while alkaline aqueous solutions of a predetermined concentration are discharged from the first chamber 2m and the second chamber 2n, producing hydrogen and oxygen. The temperature of the aqueous solutions supplied to the first chamber 2m and the second chamber 2n can be adjusted, for example, from room temperature to 90°C or below.

[0068] If the anode 2a includes the water electrolysis electrode 1, the cathode 2b may include, for example, an electrode material known as the cathode of an alkaline water electrolysis cell. If the cathode 2b includes the water electrolysis electrode 1, the anode 2a may include an electrode material known as the anode of an alkaline water electrolysis cell. In the water electrolysis cell 2, both the anode 2a and the cathode 2b may include the water electrolysis electrode 1.

[0069] With the above configuration, since at least one selected from the group consisting of anode 2a and cathode 2b includes the water electrolysis electrode 1, the water electrolysis cell 2 can exhibit high performance when the temperature at which water electrolysis is performed is high.

[0070] (Third embodiment) Figure 6 is a schematic cross-sectional view showing an example of a water electrolysis apparatus according to the third embodiment. As shown in Figure 6, the water electrolysis apparatus 3 comprises a water electrolysis cell 2 according to the second embodiment and a voltage inductor 40. The voltage inductor 40 applies a voltage between the cathode 2b and the anode 2a. The water electrolysis apparatus 3 is an alkaline water electrolysis apparatus that uses an alkaline aqueous solution.

[0071] The voltage inductor 40 is electrically connected to the anode 2a and the cathode 2b. The voltage inductor 40 raises the potential of the anode 2a above the potential of the cathode 2b. The voltage inductor 40 is not limited to any particular type of voltage inductor, as long as it can apply a voltage between the anode 2a and the cathode 2b. The voltage inductor 40 may also be a device that adjusts the voltage applied between the anode 2a and the cathode 2b. When the voltage inductor 40 is connected to a DC power source such as a battery, solar cell, and fuel cell, the voltage inductor 40 includes, for example, a DC / DC converter. When the voltage inductor 40 is connected to an AC power source such as a commercial power supply, the voltage inductor 40 includes, for example, an AC / DC converter. The voltage inductor 40 may also be, for example, a power supply. In a power supply, the voltage applied between the anode 2a and the cathode 2b, and the current flowing between the anode 2a and the cathode 2b are adjusted so that the power supplied to the water electrolysis device 3 is a predetermined set value.

[0072] With the above configuration, the water electrolysis device 3 can exhibit high performance when the temperature at which water electrolysis is performed is high.

[0073] (Fourth Embodiment) Figure 7 is a schematic cross-sectional view showing an example of a water electrolysis cell according to the fourth embodiment. As shown in Figure 7, the water electrolysis cell 4 comprises an anode 4a, a cathode 4b, and an anion exchange membrane 4p. In the water electrolysis cell 4, at least one selected from the group consisting of anode 4a and cathode 4b includes, for example, the water electrolysis electrode 1 according to the first embodiment. In this case, the activity of the anode reaction or the cathode reaction in the water electrolysis cell 4 tends to be high, and the anode 4a or cathode 4b tends to exhibit high performance.

[0074] The water electrolysis cell 4 is, for example, an anion exchange membrane (AEM) type water electrolysis cell. As shown in Figure 7, the anode 4a comprises, for example, an electrode catalyst layer 4m and a gas diffusion layer 4n. The cathode 4b comprises, for example, an electrode catalyst layer 4j and a gas diffusion layer 4k. The electrode catalyst layer 4m of the anode 4a is in contact with one main surface of the anion exchange membrane 4p, and the electrode catalyst layer 4j of the cathode 4b is in contact with the other main surface of the anion exchange membrane 4p. The temperature of the aqueous solution supplied to the water electrolysis cell 4 is adjusted, for example, from room temperature to 90°C or below.

[0075] The anion exchange membrane 4p is not limited to a specific type of anion exchange membrane. The anion exchange membrane 4p is conductive to anions such as hydroxide ions. The anion exchange membrane 4p can prevent the mixing of oxygen gas produced at anode 4a and hydrogen gas produced at cathode 4b. The oxygen gas is guided outside anode 4a through the gas diffusion layer 4n. The hydrogen gas is guided outside cathode 4b through the gas diffusion layer 4k.

[0076] In the water electrolysis cell 4, if the anode 4a includes the water electrolysis electrode 1, the cathode may be a known cathode in an AEM-type water electrolysis cell. In the water electrolysis cell 4, if the cathode 4b includes the water electrolysis electrode 1, the anode 4a may be a known anode in an AEM-type water electrolysis cell. In the water electrolysis cell 4, both the anode 4a and the cathode 4b may include the water electrolysis electrode 1.

[0077] With the above configuration, since at least one selected from the group consisting of anode 4a and cathode 4b includes the water electrolysis electrode 1, the water electrolysis cell 4 can exhibit high performance when the temperature at which water electrolysis is performed is high.

[0078] (Fifth embodiment) Figure 8 is a schematic cross-sectional view showing an example of a water electrolysis apparatus according to the fifth embodiment. As shown in Figure 8, the water electrolysis apparatus 5 comprises a water electrolysis cell 4 and a voltage injector 40. The voltage injector 40 applies a voltage between the cathode 4b and the anode 4a. The water electrolysis apparatus 5 is, for example, an AEM type water electrolysis apparatus.

[0079] The voltage inductor 40 is electrically connected to the anode 4a and the cathode 4b. The voltage inductor 40 raises the potential of the anode 4a above the potential of the cathode 4b. The voltage inductor 40 is not limited to any particular type of voltage inductor, as long as it can apply a voltage between the anode 4a and the cathode 4b. The voltage inductor 40 may also be a device that adjusts the voltage applied between the anode 4a and the cathode 4b. When the voltage inductor 40 is connected to a DC power source such as a battery, solar cell, or fuel cell, the voltage inductor 40 includes, for example, a DC / DC converter. When the voltage inductor 40 is connected to an AC power source such as a commercial power supply, the voltage inductor 40 includes, for example, an AC / DC converter. The voltage inductor 40 may also be, for example, a power supply. In a power supply, the voltage applied between the anode 4a and the cathode 4b, and the current flowing between the anode 4a and the cathode 4b are adjusted so that the power supplied to the water electrolysis device 5 is a predetermined set value.

[0080] With the above configuration, the water electrolysis device 5 can exhibit high performance when the temperature at which water electrolysis is performed is high.

[0081] (Note) Based on the above description, the following technologies are disclosed. (Technology 1) An electrode for water electrolysis, A conductive substrate containing Ni, The conductive substrate is provided with a layered double hydroxide layer containing Ni, In the diffraction pattern of the minute-angle incident X-ray diffraction measurement of the aforementioned water electrolysis electrode, The ratio of the intensity of the diffraction peak of the layered double hydroxide (110) plane to the intensity of the diffraction peak of the Ni(111) plane is 0.0030 or more and 0.0050 or less. Electrode for water electrolysis. (Technology 2) The aforementioned ratio is between 0.0034 and 0.0047. Electrodes for water electrolysis as described in Technology 1. (Technology 3) The aforementioned ratio is between 0.0038 and 0.0047. Electrodes for water electrolysis as described in Technology 2. (Technology 4) The aforementioned ratio is between 0.0043 and 0.0047. Electrodes for water electrolysis as described in Technical 3. (Technology 5) The layered double hydroxide layer further comprises at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Cu, W, and Ru. An electrode for water electrolysis as described in any one of the technical items 1 to 4. (Technology 6) The aforementioned layered double hydroxide layer contains Fe, Electrodes for water electrolysis as described in Technical 5. (Technology 7) The aforementioned layered double hydroxide layer contains a chelating agent. An electrode for water electrolysis as described in any one of the technical items 1 to 6. (Technology 8) The chelating agent comprises at least one selected from the group consisting of acetylacetone and citrate. Electrodes for water electrolysis as described in Technical 7. (Technology 9) The aforementioned layered double hydroxide has a crystallite size of 5 nm to 15 nm. An electrode for water electrolysis as described in any one of the technical items 1 to 8. (Technology 10) The surface of the conductive substrate is made of Ni. An electrode for water electrolysis as described in any one of the technical items 1 to 9. (Technology 11) The Ni forming the surface of the conductive substrate has a purity of 90% by mass or more. An electrode for water electrolysis as described in Technical 10. (Technology 12) The conductive substrate is in the form of a sheet and has a plurality of openings arranged along the main surface of the conductive substrate. An electrode for water electrolysis as described in any one of the technical specifications 1 to 11. (Technology 13) A water electrolysis anode comprising an electrode for water electrolysis as described in any one of the technical items 1 to 12. (Technology 14) A water electrolysis cathode comprising an electrode for water electrolysis as described in any one of the technical items 1 to 12. (Technology 15) A-scatter, Cathode and, Equipped with a diaphragm, At least one of the following conditions is met: the anode is an anode for water electrolysis as described in Technical 13, and the cathode is a cathode for water electrolysis as described in Technical 14. water electrolysis cell. (Technology 16) A-scatter, Cathode and, It comprises an anion exchange membrane, At least one of the following conditions is met: the anode is an anode for water electrolysis as described in Technical 13, and the cathode is a cathode for water electrolysis as described in Technical 14. water electrolysis cell. (Technology 17) A water electrolysis cell as described in Technical 15 or 16, The system includes a voltage injector that applies a voltage between the cathode and the anode. Water electrolysis equipment. [Examples]

[0082] The present disclosure will be described in more detail below with reference to examples. Note that the following examples are merely examples of the present disclosure and are not limited to these examples.

[0083] (Example 1) A solution was prepared by dissolving 0.435 g of nickel chloride hexahydrate and 0.247 g of iron chloride hexahydrate in 3.25 ml (mL) of water. The nickel chloride hexahydrate and iron chloride hexahydrate were purchased from Fujifilm Wako Pure Chemical Industries, Ltd. To this solution, 0.028 mL of acetylacetone (ACAC) was added as a chelating agent to obtain a chelating agent-containing solution. The ACAC was also purchased from Fujifilm Wako Pure Chemical Industries, Ltd. The molar ratio of ACAC content to Fe content in the chelating agent-containing solution was 0.3.

[0084] A single sheet of Ni expanded metal manufactured by Taiyo Kanaami Co., Ltd. was prepared. This Ni expanded metal had a thickness of 1.0 mm and, in plan view, had a shape consisting of a square A with a side length of 10 mm and a square B with a side length of 2 mm connected to it. The Ni expanded metal was washed with water and dried to complete the cleaning process.

[0085] Next, the Ni expanded metal, after the cleaning process was completed, was immersed in the chelating agent-containing solution described above. In this state, the chelating agent-containing solution containing the Ni expanded metal was shaken and stirred at 25°C for 1 hour. At this time, the outermost surface of the Ni expanded metal was etched according to equation (3) above.

[0086] Next, 0.424 mL of glycidol (GL) was added to the chelating agent-containing solution as a pH raising agent. The resulting mixed solution was shaken and stirred at 25°C for 4 hours. After 4 hours of shaking and stirring, the Ni expanded metal was recovered, washed with water, and dried. In this way, the electrode according to Example 1 was obtained.

[0087] (Example 2) An electrode according to Example 2 was prepared in the same manner as in Example 1, except for the points described below. 0.326 g of nickel chloride hexahydrate and 0.185 g of iron chloride hexahydrate were dissolved in 3.33 mL of water. The molar ratio of ACAC content to Fe content in the chelating agent-containing solution was 0.3.

[0088] (Example 3) An electrode according to Example 3 was prepared in the same manner as in Example 1, except for the points described below. 0.272 g of nickel chloride hexahydrate and 0.154 g of iron chloride hexahydrate were dissolved in 3.70 mL of water. The molar ratio of ACAC content to Fe content in the chelating agent-containing solution was 0.3.

[0089] (Example 4) An electrode according to Example 4 was prepared in the same manner as in Example 1, except for the points described below. 0.210 g of nickel chloride hexahydrate and 0.120 g of iron chloride hexahydrate were dissolved in 3.42 mL of water. The molar ratio of ACAC content to Fe content in the chelating agent-containing solution was 0.15.

[0090] (Comparative Example 1) An electrode according to Comparative Example 1 was prepared in the same manner as in Example 1, except for the points described below. 0.149 g of nickel chloride hexahydrate and 0.169 g of iron chloride hexahydrate were dissolved in 3.43 mL of water. The molar ratio of ACAC content to Fe content in the chelating agent-containing solution was 0.15.

[0091] (Comparative Example 2) An electrode according to Comparative Example 2 was prepared in the same manner as in Example 1, except for the points described below. 0.210 g of nickel chloride hexahydrate and 0.120 g of iron chloride hexahydrate were dissolved in 3.41 mL of water. The molar ratio of ACAC content to Fe content in the chelating agent-containing solution was 0.30.

[0092] (Comparative Example 3) An electrode according to Comparative Example 3 was prepared in the same manner as in Example 1, except for the points described below. 0.150 g of nickel chloride hexahydrate and 0.170 g of iron chloride hexahydrate were dissolved in 3.41 mL of water. The molar ratio of ACAC content to Fe content in the chelating agent-containing solution was 0.45.

[0093] [Evaluation of electrode crystallinity] The crystallinity of the electrodes was evaluated by micro-angle X-ray diffraction (GIXD) measurement. For the GIXD measurement, a Rigaku Smartlab was used, with Cu as the anticathode of the X-ray generator. Cu-Kα rays were used as the X-rays. The parallel beam method was employed. As scanning conditions, each electrode was placed on the sample stage, the angle between the incident X-ray and the sample surface was fixed at 3°, and the sample was rotated 360° horizontally. The intensity of the diffraction peaks originating from the Ni(111) plane appearing in the diffraction angle range of 42° to 46° was measured. GIXD measurements were performed in continuous scanning mode in the diffraction angle range of 5° to 65° in the direction where the diffraction peak intensity originating from the Ni(111) plane was maximum, and the diffraction pattern was obtained. The step size for the GIXD measurement was set to 0.04°. In the obtained diffraction pattern, diffraction peaks originating from the (110) plane of the LDH were confirmed in the diffraction angle range of 59° to 61°. The baseline was determined by specifying a baseline position that does not overlap with the tail of the diffraction peak and interpolating the baseline using a spline function. The peak intensity of each diffraction peak was calculated by determining its height from the baseline. Table 1 shows the diffraction peak intensity originating from the Ni(111) plane and the diffraction peak intensity originating from the (110) plane of the LDH for each electrode. Figure 9A is a graph showing the diffraction pattern of the electrode according to Example 1 after GIXD measurement. Figure 9B is a graph showing the diffraction pattern of the electrode according to Example 2 after GIXD measurement. Figure 9C is a graph showing the diffraction pattern of the electrode according to Example 3 after GIXD measurement. Figure 9D is a graph showing the diffraction pattern of the electrode according to Example 4 after GIXD measurement. Figure 9E is a graph showing the diffraction pattern of the electrode according to Comparative Example 1 after GIXD measurement. Figure 9F is a graph showing the diffraction pattern of the electrode according to Comparative Example 2 after GIXD measurement. Figure 9G is a graph showing the diffraction pattern of the electrode according to Comparative Example 3 after GIXD measurement.

[0094] The crystallite size D of LDH in the direction parallel to the (110) plane of LDH was calculated according to equation (2) from the full width at half maximum (FMAX) of the diffraction peaks originating from the (110) plane of LDH in the diffraction patterns of each electrode. In this calculation, Scherrer's constant K = 0.9 and the X-ray wavelength λ = 0.15418 nm were used. The FMAX described above was used for the diffraction line width broadening B. The results are shown in Table 1. As shown in Table 1, the crystallite size D of LDH in each example was in the range of 5 nm to 15 nm. On the other hand, the crystallite size of LDH in Comparative Example 1 was greater than 15 nm, and the crystallite sizes of LDH in Comparative Examples 2 and 3 were less than 5 nm.

[0095] [Electrode overvoltage evaluation] The oxygen evolution (OER) overpotential of the electrodes in each example and comparative example was evaluated. For this evaluation, an Ivium-n-Stat potentiostat from Ivium, a custom-made cell from EC Frontier, and working electrodes fabricated by welding nickel wire to each electrode were used. In addition, a nickel coil was used as the counter electrode. A HydroFlex electrode from gaskatal was used as the reference electrode. HydroFlex is a registered trademark. Current control was performed using the three-electrode method and the anode overpotential was measured. A 6 mol / L KOH aqueous solution was used as the aqueous solution, and the temperature of the aqueous solution was adjusted to 80°C.

[0096] Currents of 10mA, 20mA, 30mA, 50mA, 70mA, 100mA, 200mA, 300mA, 400mA, 500mA, 600mA, 700mA, 800mA, 900mA, and 1000mA were applied for 120 seconds each. Then, a current of 1000mA was applied for 18 hours. Currents of 1000mA, 900mA, 800mA, 700mA, 600mA, 500mA, 400mA, 300mA, 200mA, 100mA, 70mA, 50mA, 30mA, 20mA, and 10mA were applied for 120 seconds each. Impedance measurements were performed, and the DC resistance of the electrodes was measured using Zview software from Toyo Technica Co., Ltd. The anode overvoltage was determined by subtracting the product of the current value and the DC resistance from the anode voltage at a current of 10mA after applying a current of 1000mA for 18 hours, and then subtracting the theoretical equilibrium voltage of 1.18V. The results are shown in Table 1.

[0097] As shown in Table 1, the overvoltage of the electrodes in each example was lower than that of the electrodes in the comparative example, indicating that the electrodes in each example can exhibit high performance when the temperature at which water electrolysis is performed is high. A comparison between the examples and the comparative example shows that the ratio r 110 / Ni111 A value between 0.0030 and 0.0050 is advantageous in that the electrodes perform well when the temperature at which water electrolysis is performed is high.

[0098] [Table 1]

[0099] Furthermore, many improvements and other embodiments of the disclosure will be apparent to those skilled in the art from the above description. Therefore, the above description should be interpreted as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the disclosure. Its operating conditions, composition, structure and / or function can be substantially modified without departing from the spirit of the disclosure. [Industrial applicability]

[0100] The electrode for water electrolysis disclosed herein can be used as an anode or cathode for water electrolysis. [Explanation of Symbols]

[0101] 1 Electrode for water electrolysis 2 Water electrolysis cell 2a Anode 2b Cathode 2p septum 3 Water electrolysis device 4 Water electrolysis cell 4a Anode 4b Cathode 4p anion exchange membrane 5 Water electrolysis device 10 Conductive base material 20 Catalyst layer 20a Layered double hydroxide (LDH) 40 Voltage Applyer

Claims

1. An electrode for water electrolysis, A conductive substrate containing Ni, The conductive substrate is provided with a layered double hydroxide layer containing Ni, In the diffraction pattern of the minute-angle incident X-ray diffraction measurement of the water electrolysis electrode, The ratio of the intensity of the diffraction peak of the layered double hydroxide (110) plane to the intensity of the diffraction peak of the Ni (111) plane is 0.0030 or more and 0.0050 or less. Electrode for water electrolysis.

2. The aforementioned ratio is between 0.0034 and 0.0047. The electrode for water electrolysis according to claim 1.

3. The aforementioned ratio is between 0.0038 and 0.0047. The electrode for water electrolysis according to claim 2.

4. The aforementioned ratio is between 0.0043 and 0.0047. The electrode for water electrolysis according to claim 3.

5. The layered double hydroxide layer further comprises at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Cu, W, and Ru. An electrode for water electrolysis according to any one of claims 1 to 4.

6. The aforementioned layered double hydroxide layer contains Fe, The electrode for water electrolysis according to claim 5.

7. The aforementioned layered double hydroxide layer contains a chelating agent. An electrode for water electrolysis according to any one of claims 1 to 6.

8. The chelating agent comprises at least one selected from the group consisting of acetylacetone and citrate. The electrode for water electrolysis according to claim 7.

9. The aforementioned layered double hydroxide has a crystallite size of 5 nm to 15 nm. An electrode for water electrolysis according to any one of claims 1 to 8.

10. The surface of the conductive substrate is made of Ni. An electrode for water electrolysis according to any one of claims 1 to 9.

11. The Ni forming the surface of the conductive substrate has a purity of 90% by mass or more. The electrode for water electrolysis according to claim 10.

12. The conductive substrate has a mesh structure, An electrode for water electrolysis according to any one of claims 1 to 11.

13. A water electrolysis anode comprising the water electrolysis electrode according to any one of claims 1 to 12.

14. A water electrolysis cathode comprising the water electrolysis electrode described in any one of claims 1 to 12.

15. A-scatter, Cathode and, Equipped with a diaphragm, At least one selected from the group consisting of the anode being the anode for water electrolysis described in claim 13 and the cathode being the cathode for water electrolysis described in claim 14 is satisfied. water electrolysis cell.

16. A-scatter, Cathode and, It comprises an anion exchange membrane, At least one selected from the group consisting of the anode being the anode for water electrolysis described in claim 13 and the cathode being the cathode for water electrolysis described in claim 14 is satisfied. water electrolysis cell.

17. A water electrolysis cell according to claim 15 or 16, The system includes a voltage injector that applies a voltage between the cathode and the anode. Water electrolysis equipment.

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