Water electrolysis electrode, water electrolysis anode, water electrolysis cathode, water electrolysis cell, and water electrolysis device

Abstract

This water electrolysis electrode comprises a conductive base material containing Ni, and a layered double hydroxide (LDH) layer containing Ni. The LDH layer is provided on the conductive base material. In a diffraction pattern of a grazing incidence X-ray diffraction (GIXD) measurement of the water electrolysis electrode, the ratio r003 / Ni111 of the intensity of the diffraction peak of the (003) plane of the LDH to the intensity of the diffraction peak of the Ni(111) plane is 0.025 or more. In addition, the ratio r012 / 003 of the intensity of the diffraction peak of the (012) plane of the LDH to the intensity of the diffraction peak of the (003) plane of the LDH is 0.60 to less than 1.0.

Description

Water electrolysis electrodes, water electrolysis anodes, water electrolysis cathodes, water electrolysis cells, and water electrolysis devices

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

[0002] Electrodes for water electrolysis have been known in the past.

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

[0004] Patent Document 2 describes an oxygen generating catalyst that includes a graphene oxide layer and a nickel-iron layered double hydroxide layer supported on the surface of the graphene oxide layer, in which the graphene oxide layer has an average thickness of 0.33 to 4 nm.

[0005] Non-Patent Document 1 investigates the activity of an electrode made of Ni-Fe layered double hydride (Ni-Fe LDH) for the oxygen evolution reaction (OER).

[0006] Non-Patent Document 2 describes that the interface interaction between FeOOH and Ni-Fe LDH adjusts the local electronic structure of Ni-Fe LDH, thereby enhancing the OER electrocatalytic activity.

[0007] International Publication No. 2017 / 154134 Japanese Patent Application Laid-Open No. 2018-043193

[0008] Seyeong Lee et al., “Operational durability of three-dimensional Ni-Fe layered double hydroxide electrocatalyst for water oxidation,” Electrochimica Acta, 2019, Vol.315, p.94-101Jiande 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

[0009] The descriptions in the above documents need to be reconsidered from the viewpoint of improving the performance of electrodes for water electrolysis. Therefore, the present disclosure provides a novel electrode for water electrolysis that is advantageous in terms of achieving high performance.

[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; wherein, in a diffraction pattern obtained by grazing incidence X-ray diffraction measurement of the electrode for water electrolysis, the ratio of the diffraction peak intensity of the (003) plane of the layered double hydroxide to the diffraction peak intensity of the Ni (111) plane is 0.025 or more; and the ratio of the diffraction peak intensity of the (012) plane of the layered double hydroxide to the diffraction peak intensity of the (003) plane of the layered double hydroxide is 0.60 or more and less than 1.0.

[0011] According to the present disclosure, it is possible to provide a novel electrode for water electrolysis that is advantageous in terms of exhibiting high performance.

[0012] FIG. 1 is a cross-sectional view showing an example of a water electrolysis electrode according to the present disclosure. FIG. 2 is a diagram schematically showing an example of the crystal structure of a layered double hydroxide (LDH). FIG. 3 is a diagram schematically showing an example of a mechanism for producing a water electrolysis electrode. FIG. 4 is a cross-sectional view showing an example of a water electrolysis cell according to the present disclosure. FIG. 5 is a cross-sectional view showing an example of a water electrolysis apparatus according to the present disclosure. FIG. 6 is a cross-sectional view showing another example of a water electrolysis cell according to the present disclosure. FIG. 7 is a cross-sectional view showing another example of a water electrolysis apparatus according to the present disclosure. FIG. 8A is a graph showing a diffraction pattern obtained by grazing incidence X-ray diffraction (GIXD) measurement of the electrode according to Example 1. FIG. 8B is a graph showing a diffraction pattern obtained by GIXD measurement of the electrode according to Example 2. FIG. 8C is a graph showing a diffraction pattern obtained by GIXD measurement of the electrode according to Example 3. FIG. 9A is a graph showing a diffraction pattern obtained by GIXD measurement of the electrode according to Comparative Example 1. FIG. 9B is a graph showing a diffraction pattern obtained by GIXD measurement of the electrode according to Comparative Example 2. Fig. 9C is a graph showing a diffraction pattern obtained by GIXD measurement of an electrode according to Comparative Example 3. Fig. 9D is a graph showing a diffraction pattern obtained by GIXD measurement of an electrode according to Comparative Example 4. Fig. 9E is a graph showing a diffraction pattern obtained by GIXD measurement of an electrode according to Comparative Example 5.

[0013] (Knowledge forming the basis of the present disclosure) The use of renewable energy such as solar and wind power has been attracting attention as a measure against global warming. Power generation using renewable energy has the problem of surplus electricity being wasted. For this reason, the utilization efficiency of renewable energy is not necessarily sufficient. Therefore, a method of effectively utilizing surplus electricity by producing and storing hydrogen from surplus electricity has been studied.

[0014] Water electrolysis is one possible method for producing hydrogen from surplus electricity. To produce hydrogen inexpensively and stably, there is a need for the development of a highly efficient, long-life water electrolysis device. In a water electrolysis device, oxygen is generated at the anode, and hydrogen is generated at the cathode. The reaction by which oxygen is generated at the anode is also called the anode reaction, and the reaction by which hydrogen is generated at the cathode is also called the cathode reaction. To provide a highly efficient water electrolysis device, it is desirable that the overvoltage at the anode is low. Additionally, it is also desirable that the overvoltage at the cathode is low. Therefore, there is a need for the development of high-performance electrodes for the anode reaction or cathode reaction in water electrolysis.

[0015] For example, Ni-containing materials such as LDHs are considered promising materials for water electrolysis electrodes in terms of their large specific surface area and diverse combinations of metal ions. For example, according to Patent Literature 1, an electrode substrate containing a specific layered double hydroxide is produced by electrodeposition in an aqueous solution containing a compound containing metal M1 and a compound containing metal M2, using a conductive substrate as the anode. However, the performance of the electrode produced by electrodeposition is insufficient, leaving room for improvement. After extensive research, the present inventors have newly discovered that the performance of a water electrolysis electrode comprising a Ni-containing LDH layer provided on a Ni-containing conductive substrate can be improved by adjusting the crystalline state of the electrode to a predetermined state, and have completed the water electrolysis electrode of the present disclosure.

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments. Note that the embodiments described below are all comprehensive or specific examples. Therefore, the numerical values, shapes, materials, components, component placement positions, and connection configurations shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims that represent the highest concepts will be described as optional components. Furthermore, in the drawings, descriptions of components with the same reference numerals may be omitted. Furthermore, the drawings schematically illustrate each component to facilitate understanding, and the shapes, dimensional ratios, etc. may not be accurately represented.

[0017] First Embodiment Fig. 1 is a cross-sectional view showing an electrode for water electrolysis according to the first embodiment. As shown in Fig. 1, the electrode for water electrolysis 1 comprises a conductive substrate 10 containing Ni and a layered double hydroxide (LDH) layer 20 containing Ni. The LDH layer 20 is provided on the conductive substrate 10. In a diffraction pattern obtained by grazing incidence X-ray diffraction (GIXD) measurement of the electrode for water electrolysis 1, the ratio r of the diffraction peak intensity of the LDH (003) plane to the diffraction peak intensity of the Ni (111) plane is 003 / Ni111 In addition, the ratio r of the intensity of the diffraction peak of the LDH (012) plane to the intensity of the diffraction peak of the LDH (003) plane is 0.025 or more. 012 / 003 is 0.60 or more and less than 1.0. With this configuration, many crystals having crystal faces capable of exhibiting high activity can be present in the LDH layer 20. This tends to reduce the overvoltage at the anode or cathode for water electrolysis, and the water electrolysis electrode 1 tends to exhibit high performance.

[0018] Ratio 003 / Ni111 The ratio r is, for example, 0.070 or less. 003 / Ni111 is preferably 0.063 or less. In this case, the overvoltage at the anode or cathode of water electrolysis tends to be low, and the water electrolysis electrode 1 tends to exhibit high performance. 003 / Ni111 is more preferably 0.030 or less, and even more preferably 0.028 or less.

[0019] Ratio012 / 003 is preferably 0.69 or more and less than 1.0. 012 / 003 is preferably 0.60 or more and 0.9 or less, more preferably 0.60 or more and 0.86 or less. In this case, the overvoltage at the anode or cathode for water electrolysis is likely to be lower, and the water electrolysis electrode 1 is more likely to exhibit high performance.

[0020] 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 a metal other than Ni or may contain a resin. The entire conductive substrate 10 may be made of metal. The conductive substrate 10 may have a configuration in which a metal-containing surface layer is formed on a resin member such as polypropylene or polyethylene. In this case, the metal-containing surface layer 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 or Fe, or an alloy such as stainless steel or Inconel. Inconel is a registered trademark.

[0021] The conductive substrate 10 has a surface made of, for example, Ni. In this case, the conductive substrate 10 is likely to have high alkali resistance. When the conductive substrate 10 has a surface 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 sputtered film or a plated film.

[0022] When the conductive substrate 10 has a surface made of Ni, the purity of the Ni constituting the surface is not limited to a specific value. The purity is, for example, 90% by mass or more. In this case, the conductive substrate 10 is more likely to have high alkali resistance. The method for determining the purity of the Ni constituting the surface of the conductive substrate 10 is not limited to a specific method. The purity of the Ni constituting 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 constituting the surface of the conductive substrate 10 may 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). When the purity of Ni is high, the purity of the Ni constituting 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.

[0023] 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.

[0024] The shape of the conductive substrate 10 is not limited to a specific shape. The conductive substrate 10 is, for example, sheet-shaped. The conductive substrate 10 may have a non-porous structure such as a plate or foil, or a porous structure such as an expanded metal, mesh, foam, or nonwoven fabric. The conductive substrate 10 preferably has a porous structure. In this case, the surface area of ​​the conductive portion of the conductive substrate 10 tends to be large, and gas generated in the water electrolysis reaction tends to diffuse easily.

[0025] The thickness of the conductive substrate 10 is not limited to a specific value. The thickness is, for example, 0.02 mm or more. In this case, the conductive substrate 10 tends to be easy to handle. The thickness of the conductive substrate 10 is, for example, 10 mm or less, and preferably 1 mm or less.

[0026] The LDH layer 20 has a ratio r 003 / Ni111 is 0.025 or more, and the ratio r 012 / 003The thickness of the LDH layer 20 is not limited to a specific value as long as the ratio is 0.60 or more and less than 1.0. For example, the thickness of the LDH layer 20 is not limited to a specific value. The LDH layer 20 includes a portion having a thickness of, for example, 35 nm or more. With this configuration, the water electrolysis electrode 1 is likely to have high electrode activity. The thickness of the LDH layer 20 can be determined, for example, by observing the cross section of the water electrolysis electrode 1 with a transmission electron microscope (TEM). The thickness of the LDH layer 20 is, for example, 5000 nm or less.

[0027] The LDH layer 20 covers, for example, the surface of the conductive substrate 10. The coverage of the LDH layer 20 on the surface of the conductive substrate 10 is not limited to a specific value. The coverage is preferably 99% or more. In this case, the water electrolysis electrode 1 is more likely to have high electrode activity. In addition, the water electrolysis electrode 1 is more likely to have high durability.

[0028] 2 is a diagram schematically illustrating an example of the crystal structure of an LDH. The LDH 20a contained in the LDH layer 20 is active in a reaction for producing gases such as hydrogen and oxygen at the anode or cathode of water electrolysis. For example, the LDH 20a can be converted into hydroxides during alkaline water electrolysis.

[0029] The LDH 20a has, for example, a composition represented by the following formula (1): 2+ is a divalent transition metal ion. 3+ is a trivalent transition metal ion. n- is an anion between layers. x is a rational number satisfying the condition 0<x<1. y is a number corresponding to the amount of charge balance required. n is an integer. m is an appropriate rational number. [M1 2+ 1-x M2 3+ x (OH)2][yA n- ・mH2O] Formula (1)

[0030] 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 a specific transition metal. In other words, M1 and M2 in the composition shown in formula (1) are not limited to a specific transition metal.

[0031] The LDH 20a further contains, for example, at least two elements selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, W, and Ru. In this case, the water electrolysis electrode 1 is more likely to have high electrode activity.

[0032] The LDH 20a preferably contains Fe. In this case, the water electrolysis electrode 1 is more likely to have high electrode activity. In addition, the production cost of the water electrolysis electrode 1 is likely to be low. For example, in the composition represented by formula (1), M1 may be Ni and M2 may be Fe. In this case, the water electrolysis electrode 1 is more likely to have high electrode activity.

[0033] In LDH20a, the interlayer anion A n- may be an inorganic ion or an organic ion. An example of an inorganic ion is CO 2- , NO3 - , Cl - , SO4 2- ,Br - , O.H. - , F - , I - , Si2O5 2- , B4O5(OH)4 2- , and PO 3- An example of an organic ion is CH3(CH2) n SO 4- , CH3 (CH2) n COO - , CH3 (CH2) n P.O. 4- , and CH3(CH2) n NO 3- It is. A n- can be intercalated between the layers of the metal hydroxide along with water molecules. n- The charge and ion size of LDH20a are not limited to a specific value. n- or a plurality of types of A n- may also include:

[0034] As shown in FIG. 2, LDH20a is a soluble form of M1 2+ or M2 3+ OH at each vertex of the octahedron centered at - LDH20a contains [M12+ 1-x M2 3+ x (OH) x+ This metal hydroxide has a layered structure in which hydroxide octahedra are connected two-dimensionally, sharing edges. Between the metal hydroxide layers, anions A n- and water molecules are present. The metal hydroxide layer functions as a host layer 21, and anions A n- and a guest layer 22 containing water molecules is disposed between the host layers. In other words, the LDH 20a as a whole is composed of a host layer 21 of metal hydroxide and an anion A n- The LDH 20a has a sheet-like structure in which M1 contained in the metal hydroxide layer and a guest layer 22 of water molecules are alternately laminated. 2+ Part of M2 3+ It has a structure substituted with:

[0035] The crystalline structure and crystallinity of the LDH 20a can be qualitatively and quantitatively analyzed by XRD. When the LDH layer 20 is thin, the XRD signal is reduced, making analysis difficult. Therefore, grazing incidence X-ray diffraction (GIXD) measurement is preferably used for qualitative and quantitative analysis. The angle between the incident X-rays and the sample surface is fixed at 3°, and the water electrolysis electrode 1 is rotated horizontally by 360° to measure the diffraction peak intensity derived from the crystal plane of the conductive substrate 10 at which the XRD diffraction peak intensity is maximized. For example, if the conductive substrate 10 contains Ni, the diffraction peak intensity derived from the (111) plane of Ni, which appears in the range of 2θ = 42° to 46°, is measured. A diffraction pattern of the LDH layer 20 is obtained by XRD in the plane direction of the water electrolysis electrode 1 at which the diffraction peak intensity derived from the crystal plane of the conductive substrate 10 is maximized. In this diffraction pattern, for example, diffraction peaks originating from the (003), (012), (015), and (018) planes of LDH20a are obtained in the ranges of 2θ = 10° to 12°, 2θ = 33° to 36°, 2θ = 38° to 40°, and 2θ = 46° to 48°, respectively. The intensity of each diffraction peak is determined as the diffraction peak height, which is the height of each diffraction peak from the baseline.

[0036] Ratio 003 / Ni111is considered to be correlated with the degree of crystal growth in the thickness direction of the sheet-like structure of the LDH 20a. 003 / Ni111 The large ratio r is considered to indicate that the crystal growth in the thickness direction of the sheet-like structure of LDH 20a is progressing. 012 / 003 is considered to be correlated with the degree of crystal growth in the in-plane direction of the sheet-like structure of the LDH 20a. 012 / 003 The large value of σ is considered to indicate that crystal growth in the thickness direction of the sheet-like structure of LDH 20a has progressed.

[0037] The LDH layer of the water electrolysis electrode may contain a chelating agent. The chelating agent is, for example, an organic compound capable of coordinating with transition metal ions in the LDH 20a. The chelating agent may be at least one selected from the group consisting of bidentate organic ligands and tridentate organic ligands. Examples of the chelating agent include β-diketones, β-ketoesters, hydroxycarboxylic acids, and hydroxycarboxylates. Examples of β-diketones include acetylacetone (ACAC), trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, thenoyltrifluoroacetone, dipyrrolylmethane, dibenzoylmethane, and ascorbic acid. Examples of β-ketoesters 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-oxopentanoate. Examples of hydroxycarboxylic acids and their salts are tartaric acid, citric acid, malic acid, gluconic acid, ferulic acid, lactic acid, glucuronic acid, and salts thereof.

[0038] On the other hand, the LDH layer 20 does not contain, for example, a chelating agent. 003 / Ni111 and ratio r 012 / 003 is likely to fall within the desired range, and the water electrolysis electrode 1 is likely to have high electrode activity.

[0039] The method for producing the water electrolysis electrode 1 is not limited to a specific method. The water electrolysis electrode 1 is produced, for example, by immersing the conductive substrate 10 in a solution containing two or more types of transition metal ions and adjusting the solution to alkaline. According to such a method, for example, the LDH layer 20 can be formed on the conductive substrate 10 in a simple manner.

[0040] The temperature of the solution when adjusted to be alkaline is not limited to a specific temperature. The temperature of the solution is, for example, room temperature of 20° C.±15° C. In this case, a water electrolysis electrode 1 having high electrode activity is likely to be obtained.

[0041] The solvent of the solution may be water, an organic solvent, or a mixed solvent of water and an organic solvent.

[0042] The method for producing the water electrolysis electrode 1 preferably includes increasing the pH. 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. In addition, the produced water electrolysis electrode 1 is likely to have high durability.

[0043] The method for adjusting the solution to alkaline is not limited to a specific method. For example, the solution may be adjusted to alkaline by mixing the above solution with an alkaline solution. Alternatively, the solution may be adjusted to alkaline by adding a pH-increasing agent to the above solution. In this case, the pH-increasing agent is not limited to a specific compound. The pH-increasing agent is preferably glycidol. In this case, the above ratio r 003 / Ni111 and ratio r 012 / 003 is likely to fall within the desired range, and the water electrolysis electrode 1 is likely to have high electrode activity. Glycidol has an epoxy group and a hydroxyl group. In the presence of a nucleophile such as chloride ions, the ring-opening reaction of the epoxy group of glycidol occurs, and the pH-elevating agent can capture hydrogen ions present in the solution. This increases the pH of the solution, making it alkaline.

[0044] The interaction of the ring-opened compound of glycidol with the transition metal ion facilitates the adjustment of the crystallinity of the crystals contained in the LDH layer 20 to a desired state, and the above ratio r 003 / Ni111 and ratio r012 / 003 In particular, it is considered that the interaction between the hydroxy group of the ring-opened compound of glycidol and the transition metal ion is likely to be in the desired range. 003 / Ni111 and ratio r 012 / 003 For example, when the molar ratio of the amount of transition metal ions to the amount of glycidol in the solution is 0.4 or more and 2.8 or less, the ratio r 003 / Ni111 and ratio r 012 / 003 Therefore, even if an organic compound having an epoxy group and a hydroxy group other than glycidol is used as the pH-raising agent, the above ratio r 003 / Ni111 and ratio r 012 / 003 It is believed that the pH can be in the desired range. The pH-raising agent is preferably an organic compound having an epoxy group and a hydroxy group.

[0045] Organic compounds having an epoxy group and a hydroxy group, such as glycidol, have a higher flash point, are less flammable, and are less expensive than other epoxides. Therefore, the use of such organic compounds as a pH-increasing agent can eliminate the need for explosion-proof specifications in the manufacturing equipment for the water electrolysis electrodes 1, and tends to reduce the manufacturing cost of the water electrolysis electrodes 1.

[0046] The pH increasing agent may be sodium carbonate.

[0047] The pH of a solution containing two or more types of transition metal ions is, for example, 1. When a pH-raising agent is added to this solution, the pH of the solution gradually increases from, for example, 1, and the solution may eventually become alkaline. The final pH of the solution is, for example, 8 or more and 12 or less. The addition of the pH-raising agent to the solution causes a reaction to occur in which hydrogen ions in the solution are captured. This causes the pH of the solution to gradually increase. The time from the addition of the pH-raising agent to the solution until the pH of the solution reaches a steady state is not limited to a specific time. This time may be, for example, one hour or more, or several days.

[0048] The two or more types of transition metal ions contained in the solution are not limited to specific transition metal ions. For example, the two or more types of transition metal ions contained in the solution are ions of at least two transition metals selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, W, and Ru. In this case, a water electrolysis electrode 1 having high electrode activity can be more easily produced.

[0049] The two or more types of transition metal ions contained in the solution preferably include ions of at least one transition metal selected from the group consisting of Ni and Fe. In this case, a water electrolysis electrode 1 having high electrode activity can be more easily produced.

[0050] The two or more transition metal ions contained in the solution preferably include Fe ions. The solution preferably includes chloride ions. In this case, the reaction represented by the following formula (2) may occur. This may etch the conductive substrate 10. The method for producing the water electrolysis electrode 1 preferably includes promoting mixing of the solution before adjusting the solution to alkaline while the conductive substrate 10 is immersed in the solution. Promotion of solution mixing may be achieved, 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 or a stirrer. Such methods may generate forced convection in the solution, promoting solution mixing. This allows the conductive substrate 10 to be etched in a desired state, and the LDH layer 20 to be formed on the conductive substrate 10 in a desired state. As a result, the water electrolysis electrode 1 is likely to have high durability. Promotion of solution mixing may be achieved while the container containing the solution and the conductive substrate 10 is sealed, or may be achieved in an inert gas atmosphere. 4Ni 2+ Cl - 2+ 2Fe 3+ Cl - 3 + 2Ni → 5Ni 2+ Cl - 2+ 2Fe 2+ Cl - 2 + 1Ni formula (2)

[0051] In the production of the water electrolysis electrode 1, the molar ratio of the Fe ion content to the Ni content in the conductive base material 10 is not limited to a specific value. The molar ratio is, for example, 0.75 or less. In this case, it is possible to prevent the dissolution of Ni in the conductive base material 10 due to the reaction represented by formula (2), which would make it difficult to produce the water electrolysis electrode 1.

[0052] The molar ratio is preferably 0.05 to 0.25. In this case, the LDH layer 20 is more likely to be formed uniformly on the conductive substrate 10, and the water electrolysis electrode 1 is more likely to have high electrode activity.

[0053] FIG. 3 is a schematic diagram illustrating an example of a mechanism for producing a water electrolysis electrode 1. As shown in FIG. 3 , a conductive substrate 10 is immersed in a solution containing transition metal ions TM1 and TM2. For example, the transition metal ions TM1 are Ni ions, and the transition metal ions TM2 are Fe ions. In addition, Ni is present on the surface of the conductive substrate 10. Some of the transition metal ions TM2 etch and dissolve the Ni present on the surface of the conductive substrate 10. When the solution is adjusted to an alkaline pH, LDH 20a is synthesized in the solution along the surface of the conductive substrate 10. For example, when a pH-increasing agent such as glycidol is added, the epoxide ring-opening compound interacts with the transition metal ions TM1 and TM2 to adjust the crystal growth of LDH 20a to a desired state. As a result, an LDH layer 20 containing LDH 20a is formed on the conductive substrate 10, and a water electrolysis electrode 1 is obtained.

[0054] The water electrolysis electrode 1 according to this embodiment can be used, for example, as an electrode in a water electrolysis cell of an alkaline water electrolysis apparatus or an anion exchange membrane water electrolysis apparatus. The water electrolysis electrode 1 is used, for example, in at least one selected from the group consisting of an anode and a cathode in these water electrolysis apparatuses. In other words, at least one selected from the group consisting of a water electrolysis anode including the water electrolysis electrode 1 and a water electrolysis cathode including the water electrolysis electrode 1 can be provided. This tends to increase the activity of the anode reaction or the cathode reaction in water electrolysis.

[0055] Second Embodiment Figure 4 is a cross-sectional view schematically illustrating an example of a water electrolysis cell according to a second embodiment. As shown in Figure 4, the water electrolysis cell 2 includes an anode 2a, a cathode 2b, and a diaphragm 2p. At least one selected from the group consisting of the anode 2a and the cathode 2b 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 is likely to be high, and the anode 2a or the cathode 2b is likely to exhibit high performance.

[0056] The water electrolysis cell 2 is, for example, an alkaline water electrolysis cell that uses an alkaline aqueous solution. The alkaline aqueous solution used in the water electrolysis cell 2 is not limited to a specific alkaline aqueous solution. Examples of the alkaline aqueous solution include a potassium hydroxide aqueous solution and a sodium hydroxide aqueous solution.

[0057] 4 , the water electrolysis cell 2 includes, for example, an electrolytic cell 2s, a first chamber 2m, and a second chamber 2n. A diaphragm 2p is disposed inside the electrolytic cell 2s, separating the interior of the electrolytic cell 2s into the first chamber 2m and the second chamber 2n. An anode 2a is disposed in the first chamber 2m, and a cathode 2b is disposed in the second chamber 2n.

[0058] 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 the electrolyte. The material of the diaphragm 2p is not limited to a specific material. Examples of materials for the diaphragm 2p include asbestos, polymer-reinforced asbestos, potassium titanate bound with polytetrafluoroethylene (PTFE), zirconia bound with PTFE, and antimonic acid and antimony oxide bound with polysulfone. Other examples of materials for the diaphragm 2p include sintered nickel, nickel coated with ceramics and nickel oxide, and polysulfone. The diaphragm 2p may be Zirfon Perl UTP 500 manufactured by AGFA.

[0059] The anode 2a may be disposed in a zero-gap state, i.e., in contact with the diaphragm 2p, or may be disposed with a gap between it and the diaphragm 2p. The cathode 2b may be disposed in a contact state with the diaphragm 2p, or may be disposed with a gap between it and the diaphragm 2p.

[0060] The water electrolysis cell 2 electrolyzes an alkaline aqueous solution to produce hydrogen and oxygen. An aqueous solution containing a hydroxide of an alkali metal or alkaline earth metal is supplied to the first chamber 2m. In addition, an alkaline aqueous solution can be supplied to the second chamber 2n. Electrolysis is performed while an alkaline aqueous solution of a predetermined concentration is discharged from the first chamber 2m and the second chamber 2n, and hydrogen and oxygen are produced.

[0061] When the anode 2a includes the water electrolysis electrode 1, the cathode 2b may include, for example, a known electrode material for the cathode of an alkaline water electrolysis cell. When the cathode 2b includes the water electrolysis electrode 1, the anode 2a may include a known electrode material for 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.

[0062] According to the above configuration, at least one selected from the group consisting of the anode 2a and the cathode 2b includes the water electrolysis electrode 1, and therefore the water electrolysis cell 2 can exhibit high performance.

[0063] Third Embodiment Fig. 5 is a cross-sectional view schematically illustrating an example of a water electrolysis apparatus according to a third embodiment. As shown in Fig. 5, the water electrolysis apparatus 3 includes the water electrolysis cell 2 according to the second embodiment and a voltage applicator 40. The voltage applicator 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.

[0064] The voltage applicator 40 is electrically connected to the anode 2a and the cathode 2b. The voltage applicator 40 makes the potential of the anode 2a higher than the potential of the cathode 2b. The voltage applicator 40 is not limited to a specific type of voltage applicator as long as it can apply a voltage between the anode 2a and the cathode 2b. The voltage applicator 40 may be a device that adjusts the voltage applied between the anode 2a and the cathode 2b. When the voltage applicator 40 is connected to a DC power source such as a battery, a solar cell, or a fuel cell, the voltage applicator 40 includes, for example, a DC / DC converter. When the voltage applicator 40 is connected to an AC power source such as a commercial power source, the voltage applicator 40 includes, for example, an AC / DC converter. The voltage applicator 40 may be, for example, a power-type power supply. In the power-type 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 reaches a predetermined set value.

[0065] With the above configuration, the water electrolysis device 3 can exhibit high performance.

[0066] Fourth Embodiment Figure 6 is a cross-sectional view schematically illustrating an example of a water electrolysis cell according to a fourth embodiment. As shown in Figure 6, the water electrolysis cell 4 includes 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 the anode 4a and the 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 is likely to be high, and the anode 4a or the cathode 4b is likely to exhibit high performance.

[0067] The water electrolysis cell 4 is, for example, an anion exchange membrane (AEM)-type water electrolysis cell. As shown in Fig. 6 , the anode 4a includes, for example, an electrode catalyst layer 4m and a gas diffusion layer 4n. The cathode 4b includes, 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.

[0068] The anion exchange membrane 4p is not limited to a specific type of anion exchange membrane. The anion exchange membrane 4p has conductivity of anions such as hydroxide ions. The anion exchange membrane 4p can prevent mixing of oxygen gas generated at the anode 4a and hydrogen gas generated at the cathode 4b. The oxygen gas passes through the gas diffusion layer 4n and is guided to the outside of the anode 4a. The hydrogen gas passes through the gas diffusion layer 4k and is guided to the outside of the cathode 4b.

[0069] In the water electrolysis cell 4, when the anode 4a includes the water electrolysis electrode 1, the cathode may be a known cathode for AEM water electrolysis cells. In the water electrolysis cell 4, when the cathode 4b includes the water electrolysis electrode 1, the anode 4a may be a known anode for AEM water electrolysis cells. In the water electrolysis cell 4, both the anode 4a and the cathode 4b may include the water electrolysis electrode 1.

[0070] According to the above configuration, at least one selected from the group consisting of the anode 4a and the cathode 4b includes the water electrolysis electrode 1, and therefore the water electrolysis cell 4 can exhibit high performance.

[0071] Fifth Embodiment Fig. 7 is a cross-sectional view schematically illustrating an example of a water electrolysis apparatus according to a fifth embodiment. As shown in Fig. 7, the water electrolysis apparatus 5 includes a water electrolysis cell 4 and a voltage applicator 40. The voltage applicator 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.

[0072] The voltage applicator 40 is electrically connected to the anode 4a and the cathode 4b. The voltage applicator 40 makes the potential of the anode 4a higher than the potential of the cathode 4b. The voltage applicator 40 is not limited to a specific type of voltage applicator as long as it can apply a voltage between the anode 4a and the cathode 4b. The voltage applicator 40 may be a device that adjusts the voltage applied between the anode 4a and the cathode 4b. When the voltage applicator 40 is connected to a DC power source such as a battery, a solar cell, or a fuel cell, the voltage applicator 40 includes, for example, a DC / DC converter. When the voltage applicator 40 is connected to an AC power source such as a commercial power source, the voltage applicator 40 includes, for example, an AC / DC converter. The voltage applicator 40 may be, for example, a power-type power supply. In the power-type 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 reaches a predetermined set value.

[0073] With the above configuration, the water electrolysis device 5 can exhibit high performance.

[0074] (Additional Notes) The above disclosure discloses the following technologies: (Technology 1) An electrode for water electrolysis, comprising: a conductive base material containing Ni; and a layered double hydroxide layer containing Ni provided on the conductive base material, wherein in a diffraction pattern obtained by grazing incidence X-ray diffraction measurement of the electrode for water electrolysis, the ratio of the diffraction peak intensity of the (003) plane of the layered double hydroxide to the diffraction peak intensity of the Ni(111) plane is 0.025 or more, and the ratio of the diffraction peak intensity of the (012) plane of the layered double hydroxide to the diffraction peak intensity of the (003) plane of the layered double hydroxide is 0.60 or more and less than 1.0. (Technology 2) The water electrolysis electrode according to Technology 1, wherein in the diffraction pattern, the ratio of the diffraction peak intensity of the (012) plane of the layered double hydroxide to the diffraction peak intensity of the (003) plane of the layered double hydroxide is 0.69 or more and less than 1.0. (Technology 3) The electrode for water electrolysis according to Technology 1, wherein, in the diffraction pattern, the ratio of the diffraction peak intensity of the (012) plane of the layered double hydroxide to the diffraction peak intensity of the (003) plane of the layered double hydroxide is 0.60 or more and 0.86 or less. (Technology 4) The electrode for water electrolysis according to Technology 1, wherein, in the diffraction pattern, the ratio of the diffraction peak intensity of the (003) plane of the layered double hydroxide to the diffraction peak intensity of the Ni(111) plane is 0.063 or less. (Technology 5) The electrode for water electrolysis according to Technology 4, wherein, in the diffraction pattern, the ratio of the diffraction peak intensity of the (003) plane of the layered double hydroxide to the diffraction peak intensity of the Ni(111) plane is 0.028 or less. (Technology 6) The electrode for water electrolysis according to any one of Techniques 1 to 5, wherein the layered double hydroxide contains ions of at least two transition metals selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, W, and Ru. (Technology 7) The electrode for water electrolysis according to Technique 6, wherein the layered double hydroxide contains Fe. (Technology 8) The electrode for water electrolysis according to any one of Techniques 1 to 7, wherein the conductive substrate has a surface made of Ni. (Technology 9) The electrode for water electrolysis according to Technique 8, wherein the nickel forming the surface of the conductive substrate has a purity of 90 mass% or more.(Technology 10) The electrode for water electrolysis according to any one of Technologies 1 to 9, wherein the layered double hydroxide does not contain a chelating agent. (Technology 11) An anode for water electrolysis, comprising the electrode for water electrolysis according to any one of Technologies 1 to 10. (Technology 12) A cathode for water electrolysis, comprising the electrode for water electrolysis according to any one of Technologies 1 to 10. (Technology 13) A water electrolysis cell comprising an anode, a cathode, and a diaphragm, wherein at least one selected from the group consisting of the anode being the anode for water electrolysis according to Technology 11 and the cathode being the cathode for water electrolysis according to Technology 12 is satisfied. (Technology 14) A water electrolysis cell comprising an anode, a cathode, and an anion exchange membrane, wherein at least one selected from the group consisting of the anode being the anode for water electrolysis according to Technology 11 and the cathode being the cathode for water electrolysis according to Technology 12 is satisfied. (Technology 15) A water electrolysis device comprising: the water electrolysis cell according to Technology 13 or 14; and a voltage applicator that applies a voltage between the cathode and the anode.

[0075] The present disclosure will be described in more detail below with reference to examples. Note that the following examples are examples of the present disclosure, and the present disclosure is not limited to the following examples.

[0076] Example 1 A solution was prepared by dissolving 0.706 g of nickel chloride hexahydrate and 0.402 g of iron chloride hexahydrate in 3.409 milliliters (mL) of water in a PFA minivial manufactured by Taiyo Co., Ltd. Nickel chloride hexahydrate and iron chloride hexahydrate were purchased from Fujifilm Wako Pure Chemical Industries, Ltd.

[0077] A Ni plate manufactured by Nilaco Corporation was cleaned with acetone for 10 minutes and then with a 1M HCl aqueous solution for 10 minutes to degrease the Ni plate and remove impurities. The Ni plate had a thickness of 0.2 mm and a circular shape with a diameter of 15 mm in plan view. The Ni plate weighed 0.315 g. The Ni plate was then rinsed with water and dried to complete the cleaning process.

[0078] Next, the Ni plate after the cleaning treatment was immersed in the above solution, and in this state, the solution containing the Ni plate was shaken and stirred at 25° C. for 1 hour.

[0079] Next, 1.63 mL of glycidol (GL) was added to the solution as a pH-raising agent. The resulting mixed solution was shaken and stirred at 25°C for 4 hours. GL was purchased from Sigma-Aldrich. After 4 hours of shaking and stirring, the Ni plate was recovered, washed with water, and dried. In this way, the electrode according to Example 1 was obtained.

[0080] Example 2 An electrode according to Example 2 was fabricated in the same manner as in Example 1, except for the following points: To prepare a solution, 0.321 g of nickel chloride hexahydrate and 0.182 g of iron chloride hexahydrate were dissolved in 3.467 mL of water, and 0.313 mL of GL was added to the solution.

[0081] Example 3 An electrode according to Example 3 was fabricated in the same manner as in Example 1, except for the following points: To prepare a solution, 0.409 g of nickel chloride hexahydrate and 0.233 g of iron chloride hexahydrate were dissolved in 3.520 mL of water, and 0.224 mL of GL was added to the solution.

[0082] Comparative Example 1: A solution was prepared by dissolving 0.277 g of nickel chloride hexahydrate and 0.079 g of iron chloride hexahydrate in a PFA minivial manufactured by Taiyo Co., Ltd., with 1.33 mL of water and 2.00 mL of ethanol. The ethanol was manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. 0.0457 mL of acetylacetone (ACAC) was added to this solution as a chelating agent. The ACAC was manufactured by Sigma-Aldrich. Next, a Ni plate that had been cleaned in the same manner as in Example 1 was immersed in the above solution. In this state, the solution was shaken and stirred for 24 hours before the addition of a pH-raising agent. Then, 0.465 mL of propylene oxide (POX) was added as a pH-raising agent. After the addition of the pH-raising agent, the solution was shaken and stirred for 72 hours. The Ni plate was recovered, washed with water, and dried. In this manner, an electrode according to Comparative Example 1 was obtained.

[0083] Comparative Example 2 An electrode according to Comparative Example 2 was fabricated in the same manner as Comparative Example 1, except for the following points: 0.124 g of nickel chloride hexahydrate and 0.071 g of iron chloride hexahydrate were dissolved in 3.65 mL of water to prepare a solution, and 0.265 mL of POX was added to the solution.

[0084] Comparative Example 3 An electrode according to Comparative Example 3 was fabricated in the same manner as Comparative Example 1, except for the following points. In preparing the solution, 0.090 g of nickel chloride hexahydrate and 0.103 g of iron chloride hexahydrate were dissolved in 3.62 mL of water. The amount of the chelating agent added to the solution was 0.0239 mL. The amount of POX added to the solution was 0.274 mL.

[0085] Comparative Example 4 An electrode according to Comparative Example 4 was fabricated in the same manner as Comparative Example 1, except for the following points. To prepare the solution, 0.124 g of nickel chloride hexahydrate and 0.070 g of iron chloride hexahydrate were dissolved in a mixture of 1.46 mL of water and 2.18 mL of ethanol. The amount of chelating agent added to the solution was 0.0123 mL. The amount of POX added to the solution was 0.265 mL.

[0086] Comparative Example 5 An electrode according to Comparative Example 5 was fabricated in the same manner as Comparative Example 1, except for the following points. In preparing the solution, 0.226 g of nickel chloride hexahydrate and 0.128 g of iron chloride hexahydrate were dissolved in 3.32 mL of water. The amount of the chelating agent added to the solution was 0.0448 mL. The amount of POX added to the solution was 0.483 mL.

[0087] [Evaluation of Electrode Crystallinity] The crystallinity of the electrodes according to each example and comparative example was evaluated by small-angle X-ray diffraction (GIXD) measurement, measuring the diffraction peak intensities of the Ni(111) plane, the (012) plane, and the (003) plane. A Rigaku Smartlab was used as the X-ray generator. A Cu anticathode was used. The parallel beam method was used for GIXD. The scanning conditions were as follows: the electrode was placed on a sample stage, the angle between the incident X-rays and the sample surface was fixed at 3°, and the sample was rotated horizontally 360° to measure the peak intensity derived from the Ni(111) plane appearing in the 2θ range from 42° to 46°. GIXD measurements were performed in continuous scanning mode, varying the diffraction angle 2θ from 5° to 60° in the direction where the diffraction peak intensity of the Ni(111) plane was maximized. The step width was 0.04°, and the scanning speed was 3° / min. The baseline was determined by specifying a baseline position that did not overlap with the tails of the diffraction peaks obtained and interpolating the baseline with a spline function. The peak intensity of each peak was calculated by determining its height from the baseline. The results are shown in Table 1.

[0088] 8A, 8B, and 8C are graphs showing diffraction patterns of GIXD measurements of electrodes according to Examples 1, 2, and 3, respectively. FIGS. 9A, 9B, 9C, 9D, and 9E are graphs showing diffraction patterns of GIXD measurements of electrodes according to Comparative Examples 1, 2, 3, 4, and 5, respectively. It is believed that LDH containing Ni and Fe was formed on the Ni plate in each electrode. In the diffraction patterns of GIXD measurements of each electrode, diffraction peaks derived from the (003), (012), (015), and (018) planes of LDH were observed in the ranges of 2θ = 10° to 12°, 2θ = 33° to 36°, 2θ = 38° to 40°, and 2θ = 46° to 48°, respectively. Table 1 shows the intensities of the diffraction peaks of the Ni (111) plane, the LDH (003) plane, and the LDH (012) plane in the diffraction pattern of the GIXD measurement of each electrode, and the relationship between them.

[0089] [Electrode Overpotential Evaluation] The current density of the electrodes in each Example and Comparative Example during oxygen evolution (OER) was evaluated. For the measurements, a potentiostat VersaSTAT4 manufactured by Princeton Applied Research, a 200 mL alkali sample vial manufactured by BAS, a 200 mL Teflon cap manufactured by BAS, and an AE-2 plate electrode manufactured by EC Frontier were used as the working electrode fixture. Teflon is a registered trademark. The working electrode of each Example and Comparative Example was fixed to this fixture. A Metrohm double platinum wire counter electrode D.6.0305.200J was used as the counter electrode. The current derived from the anode reaction of the water electrolysis cell was measured using a three-electrode method under the following measurement conditions. The anode reaction was the oxygen evolution reaction. (Measurement conditions) Solution: 1 M (mol / L) KOH solution Potential to reversible hydrogen electrode (RHE): 1.0 V to 1.7 V Number of cycles: 5 cycles Potential sweep rate: 10 mV / sec Temperature: 25°C

[0090] Current density at the fifth cycle: 10 mA / cm 2 The overpotential was determined by subtracting the theoretical potential of 1.229 V required for the oxygen evolution reaction to proceed from the voltage corresponding to the reaction. The results are shown in Table 1.

[0091] As shown in Table 1, when the electrode according to the example is used, the overvoltage is lower than when the electrode according to the comparative example is used. Therefore, the electrode according to the example is likely to reduce the power consumption in water electrolysis and exhibit high performance. Comparing the example and the comparative example, in the diffraction pattern of the GIXD measurement of the electrode, the ratio r 003 / Ni111 is 0.025 or more, and the ratio r 012 / 003 It is understood that when the value is 0.60 or more and less than 1.0, the electrode is likely to exhibit high performance.

[0092]

[0093] It should be noted that many modifications and other embodiments of the present disclosure will be apparent to those skilled in the art from the above description. Accordingly, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the present disclosure. Substantial changes in operating conditions, composition, structure, and / or function can be made without departing from the spirit of the present disclosure.

[0094] The water electrolysis electrode of the present disclosure can be used as an anode or a cathode for water electrolysis.

Claims

1. An electrode for water electrolysis comprising: a conductive substrate containing Ni; and a layered double hydroxide layer containing Ni provided on the conductive substrate; wherein, in a diffraction pattern obtained by grazing incidence X-ray diffraction measurement of the electrode for water electrolysis, the ratio of the diffraction peak intensity of the (003) plane of the layered double hydroxide to the diffraction peak intensity of the Ni (111) plane is 0.025 or more; and the ratio of the diffraction peak intensity of the (012) plane of the layered double hydroxide to the diffraction peak intensity of the (003) plane of the layered double hydroxide is 0.60 or more and less than 1.

0.

2. The electrode for water electrolysis according to claim 1, wherein in the diffraction pattern, the ratio of the diffraction peak intensity of the (012) plane of the layered double hydroxide to the diffraction peak intensity of the (003) plane of the layered double hydroxide is 0.69 or more and less than 1.

0.

3. The electrode for water electrolysis according to claim 1, wherein in the diffraction pattern, the ratio of the diffraction peak intensity of the (012) plane of the layered double hydroxide to the diffraction peak intensity of the (003) plane of the layered double hydroxide is 0.60 or more and 0.86 or less.

4. The water electrolysis electrode according to claim 1, wherein in the diffraction pattern, the ratio of the diffraction peak intensity of the (003) plane of the layered double hydroxide to the diffraction peak intensity of the Ni (111) plane is 0.063 or less.

5. The water electrolysis electrode according to claim 4, wherein in the diffraction pattern, the ratio of the diffraction peak intensity of the (003) plane of the layered double hydroxide to the diffraction peak intensity of the Ni (111) plane is 0.028 or less.

6. The water electrolysis electrode according to any one of claims 1 to 5, wherein the layered double hydroxide contains ions of at least two transition metals selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, W, and Ru.

7. The water electrolysis electrode according to claim 6, wherein the layered double hydroxide contains Fe.

8. The water electrolysis electrode according to any one of claims 1 to 7, wherein the conductive substrate has a surface made of Ni.

9. The water electrolysis electrode according to claim 8, wherein the nickel forming the surface of the conductive substrate has a purity of 90 mass % or more.

10. The water electrolysis electrode according to any one of claims 1 to 9, wherein the layered double hydroxide does not contain a chelating agent.

11. An anode for water electrolysis, comprising the electrode for water electrolysis according to any one of claims 1 to 10.

12. A cathode for water electrolysis, comprising the electrode for water electrolysis according to any one of claims 1 to 10.

13. A water electrolysis cell comprising an anode, a cathode, and a diaphragm, wherein at least one selected from the group consisting of the anode being the anode for water electrolysis according to claim 11 and the cathode being the cathode for water electrolysis according to claim 12 is satisfied.

14. A water electrolysis cell comprising an anode, a cathode, and an anion exchange membrane, wherein at least one selected from the group consisting of the anode being the anode for water electrolysis according to claim 11 and the cathode being the cathode for water electrolysis according to claim 12 is satisfied.

15. A water electrolysis device comprising: the water electrolysis cell according to claim 13 or 14; and a voltage applicator that applies a voltage between the cathode and the anode.

Images