Electrodes, methods for preparing the same, anodes for water electrolysis, electrolytic cells, and methods for producing hydrogen.

Abstract

To provide an electrode with a lower oxygen overvoltage after long-term power supply, a preparation method thereof, a water electrolysis anode, an electrolytic cell using the water electrolysis anode, and a production method of hydrogen using the water electrolysis anode.SOLUTION: An electrode includes a LaNixMyO3-z (x+y is 0.8 or more and 1.2 or less, y is 0.001 or more and 0.6 or less, z is -0.5 or more and 0.5 or less, and M includes at least one of Nb, Ta, Sb, Ti, Mn, and Zr) on a substrate, wherein an initial double layer capacitance is more than 0.6 F / cm2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrode, a method for preparing the same, an anode for water electrolysis, an electrolytic cell using the anode for water electrolysis, and a method for producing hydrogen using the anode for water electrolysis. [Background technology]

[0002] In recent years, hydrogen produced using renewable energy has attracted attention as a clean energy source to address problems such as global warming caused by CO2 and the depletion of fossil fuel reserves. However, hydrogen production using renewable energy requires costs comparable to those of conventional hydrogen production through fossil fuel reforming. Therefore, hydrogen production using renewable energy requires a level of energy efficiency and low-cost equipment that could not be achieved with conventional technologies.

[0003] One method of producing hydrogen that can meet the above requirements is the electrolysis of water (water electrolysis). For example, several concepts have been proposed to produce hydrogen using water electrolysis powered by natural energy sources such as wind or solar power, and then store or transport it. In the electrolysis of water, oxygen is produced at the anode and hydrogen at the cathode when an electric current is passed through water. The main cause of energy loss in electrolysis is overpotential at both the anode and cathode. Reducing this overpotential makes it possible to produce hydrogen efficiently. In particular, the overpotential at the anode is higher than that at the cathode, and research and development to reduce the anode overpotential is being widely pursued.

[0004] Among oxides having a perovskite structure, some materials are known to have high oxygen-evolving ability and are attracting attention as anode materials for water electrolysis (Non-Patent Literature 1). In order to use an oxide having a perovskite structure as an anode for alkaline water electrolysis, there is a method of forming an oxide layer on the surface of a conductive substrate. For example, Patent Literature 1 discloses a water electrolysis anode having a low oxygen-evolving overpotential (oxygen overpotential) and high durability by forming a layer of metal oxide with a high content of perovskite-type oxide in the crystalline components on the surface of a nickel porous substrate, and a water electrolysis apparatus using this anode. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2018 / 155503 [Non-patent literature]

[0006] [Non-Patent Document 1] Science, 2011, 334, 1383 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, it was found that the anode described in Patent Document 1 has a problem in that the oxygen overpotential after long-term energization is not sufficiently low.

[0008] This invention has been made in view of the above problems, and aims to provide an electrode that exhibits a low oxygen overpotential even after prolonged energization, a method for preparing the same, an anode for water electrolysis, an electrolytic cell using the anode for water electrolysis, and a method for producing hydrogen using the anode for water electrolysis. [Means for solving the problem]

[0009] The inventors diligently conducted research and experiments to solve the above problems. As a result, they found that LaNi x My O 3-z An electrode having an initial double-layer capacitance within a specific range has been found to have a low oxygen overvoltage even after long-term energization, leading to the present invention.

[0010] That is, the present invention is as follows. [1] A base material and the On a substrate formed LaNi x M y O 3-z layer (where x + y is 0.8 or more and 1.2 or less, y is 0.001 or more and 0.6 or less, z is -0.5 or more and 0.5 or less, and M contains at least one of Nb, Ta, Sb, Ti, Mn, Zr) and having an initial double-layer capacitance exceeding 0.6 F / cm 2 and , 1cm 2 The number of moles of La per unit is between 0.06 mmol and 1.1 mmol. characterized by being an electrode 。 [2 with a capacitance per mmol of La of 10 F or more and 25 F or less, the electrode described in [1 ] . 3 The electrode according to [1] or [2], wherein the adhesion amount of the above LaNi x M y O 3-z layer exceeds 145 g / m 2 and is 3500 g / m 2 or less. 4 [1] to 3 An electrolytic cell characterized by using the electrode described in any one of [1] to as the anode. 5 4 A method for producing hydrogen, characterized by inputting a fluctuating power source to the electrolytic cell described in . 6 In a method for producing hydrogen by electrolyzing water containing an alkali with an electrolytic cell to produce hydrogen, the electrolytic cell includes at least an anode and a cathode, and the anode A base material and the is on a substrate formed LaNi x M y O 3-z ​​​ layer (x+y is between 0.8 and 1.2, y is between 0.001 and 0.6, z is between -0.5 and 0.5, and M contains at least one of the following: Nb, Ta, Sb, Ti, Mn, or Zr) and It has an initial double-layer capacitance of 0.6 F / cm². 2 Super , 1cm 2 The number of moles of La per unit is between 0.06 mmol and 1.1 mmol. A method for producing hydrogen, characterized by the following: [ 7 The process includes a step of calcining a mixture of La(NO3)3, Ni(NO3)2, and a compound having carboxyl groups and amino groups and composed of C, H, N, and O as constituent elements, and the combustion by-product gases (CO2, H2O, and N2) generated in the calcination 、 The LaNi x M y O 3-z LaNi layer x M y O 3-z Molar ratio (combustion by-product gas / LaNi x M y O 3-z [1]~[ 3 A method for preparing electrodes as described in any of the following. [ 8 The process includes a step of calcining a mixture of La(NO3)3, Ni(NO3)2, and glycine, wherein the glycine / NO3 in the mixture - [1]~[ 3 A method for preparing electrodes as described in any of the following. [Effects of the Invention]

[0011] According to the present invention, an electrode that exhibits a low oxygen overpotential even after prolonged energization, a water electrolysis anode, and a water electrolysis cell equipped with this water electrolysis anode can be obtained. [Brief explanation of the drawing]

[0012] [Figure 1]This is a side view showing an example of an electrolytic cell including an electrolytic cell equipped with the electrode of this embodiment as the anode. [Figure 2] This figure shows a cross-section of the inside of an electrolytic cell in the area enclosed by the dashed rectangle in Figure 1, in an example of an electrolytic cell that includes the electrode of this embodiment as the anode. [Figure 3] This figure shows an overview of the electrolytic apparatus used in the examples and comparative examples. [Figure 4] This diagram shows an overview of the bipolar electrolytic cell used in the electrolysis test. [Figure 5] This figure shows the equivalent circuit fitting model used to calculate the double-layer capacitance. [Modes for carrying out the invention]

[0013] The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "this embodiment"). Note that this embodiment is illustrative for explaining the present invention and is not intended to limit it. Furthermore, the present invention can be modified in various ways without departing from its essence.

[0014] (electrode) In this embodiment, the first characteristic is that the electrode has at least a substrate.

[0015] The substrate is preferably conductive. Examples of conductive substrate materials include nickel, nickel-based materials, titanium, GC (Glassy Carbon), tantalum, zirconium, gold, platinum, and palladium. Examples of nickel-based materials include nickel-based alloys such as Monel, Inconel, and Hastelloy.

[0016] From the viewpoint of heat resistance to the firing process during electrode preparation, the base material is more preferably a metal. In addition, a metal that does not dissolve even at the oxygen evolution potential in an alkaline aqueous solution and is readily available at a lower cost compared to precious metals, and from the viewpoint of durability, conductivity, and economy, nickel or a material mainly composed of nickel is even more preferable.

[0017] The conductive substrate of the electrode may be a flat plate, or it may be a porous body having a large number of holes. Specific shapes of the porous body include expanded metal, perforated metal, plain weave mesh, foamed metal, or similar shapes. Among these, expanded metal is preferred. While the dimensions are not particularly limited, to achieve both an increase in gas generation due to an increase in the electrolytic surface area and efficient removal of gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, the center-to-center distance in the short direction of the mesh (SW) is preferably 2 mm to 5 mm, the center-to-center distance in the long direction of the mesh (LW) is preferably 3 mm to 10 mm, the thickness is preferably 0.2 mm to 2 mm, and the opening ratio is preferably 20% to 80%. More preferably, SW is 3 mm to 4 mm, LW is 4 mm to 6 mm, the thickness is preferably 0.8 mm to 1.5 mm, and the opening ratio is preferably 40% to 60%.

[0018] In this embodiment, La Or x M y O 3-z The second characteristic is that (x+y is between 0.8 and 1.2, y is between 0.001 and 0.6, z is between -0.5 and 0.5, and M contains at least one of Nb, Ta, Sb, Ti, Mn, or Zr). LaNi x M y O 3-z It is laminated directly onto the substrate, LaNi x M y O 3-z It may form a layer, and the substrate and LaNi x M y O 3-z An interface may be formed between the layers. Two or more types of M may be included, such as Nb, Ta, Sb, Ti, Mn, and Zr.

[0019] In this embodiment, high oxygen evolution capacity can be achieved by arranging Ni in at least a portion of the B site as a metal oxide with a perovskite structure. Furthermore, arranging M (where M includes at least one of Nb, Ta, Sb, Ti, Mn, or Zr) together with Ni at the B site is preferable because it can impart a low oxygen overpotential even after prolonged energization.

[0020] x+y is between 0.8 and 1.2 from the viewpoint of providing a low oxygen overpotential even after prolonged energization. Preferably it is between 0.8 and 1.1, more preferably between 0.8 and 1.05, even more preferably between 0.9 and 1.05, and most preferably between 1.0 and 1.05. y is between 0.001 and 0.6. Preferably it is between 0.005 and 0.15, and more preferably it is between 0.01 and 0.1. z is between -0.5 and 0.5. In this invention, z is determined from the composition ratio of O 3-z, calculated by setting La as trivalent, Ni as trivalent, M as pentavalent, Ta as pentavalent, Sb as pentavalent, Ti as tetravalent, Mn as trivalent, Zr as tetravalent, and O as -2valent, so that the valency balance of the composition formula is correct. For example, composition formula LaNi x Nb y O 3-z In this case, if x=0.8 and y=0.2, then from the relationship 3-z=(3+3×0.8+5×0.2) / 2, we can find that z=-0.2.

[0021] On the substrate, LaLi x M y O 3-z Having (x+y is between 0.8 and 1.2, y is between 0.001 and 0.6, z is between -0.5 and 0.5, and M includes at least one of Nb, Ta, Sb, Ti, Mn, or Zr) is, for example, LaNi on a substrate. x M y O 3-z Methods include peeling off the layer, dissolving it in aqua regia, and performing compositional analysis using ICP-AES (inductively coupled plasma atomic emission spectroscopy), or analyzing the LaNi on the substrate. x M y O 3-zMethods include peeling off the layer and performing compositional analysis using an X-ray fluorescence analyzer, and the LaNi of the electrode cross-section. x M y O 3-z This can be confirmed by known methods such as SEM-EDX analysis of the layers.

[0022] In this embodiment, the initial double-layer capacitance is 0.6 F / cm². 2 Being "super" is the third characteristic. In this specification, double-layer capacitance refers to the double-layer capacitance calculated by performing AC impedance measurements using a three-electrode electrochemical cell employing a Lugin tube, obtaining a Cole-Cole plot by plotting the real and imaginary parts, and then analyzing it by equivalent circuit fitting. The specific method for calculating the double-layer capacity will be described later in the examples. In this embodiment, the area (cm²) used for calculating the double-layer capacity is... 2 ) is the geometric area of ​​the electrode. For example, if an electrode made from expanded metal is cut into a square with dimensions of 2 cm x 2 cm when viewed from the thickness direction, its area is 2 x 2 = 4 cm². 2 This is the result.

[0023] The inventors have placed LaNi on a substrate. x M y O 3-z (x+y is between 0.8 and 1.2, y is between 0.001 and 0.6, z is between -0.5 and 0.5, and M contains at least one of Nb, Ta, Sb, Ti, Mn, or Zr) and the initial bilayer capacitance is 0.6 F / cm² 2 We found that the electrode, which is ultra-high voltage, surprisingly exhibited low oxygen overpotential even after prolonged current application. The reason for this is not clear, but it is thought that the addition of element M increased the chemical stability of the electrode, and the large bilayer capacitance contributed to the low oxygen overpotential of LaNi. x M y O 3-z This is likely because the current density based on the catalyst's surface area is kept low, reducing stress on the catalyst surface even during prolonged energization, resulting in lower oxygen overpotential even after extended energization.

[0024] From the perspective of maintaining a low oxygen overpotential even after prolonged energization, the initial double-layer capacitance is set to 0.6 F / cm². 2 It is greater than 1.0 F / cm², preferably 1.0 F / cm². 2 The above is more than 1.5 F / cm 2 The above, and more preferably 1.9 F / cm 2 The above is the most preferred, and most preferably 2.5 F / cm 2 That concludes the explanation. The initial double-layer capacitance is 0.6 F / cm². 2 In the case of "extreme" conditions, the oxygen overvoltage remains low even after prolonged energization. Furthermore, the initial double-layer capacitance is preferably 7.0 F / cm². 2 The following, more preferably 6.8 F / cm 2 The following, and more preferably 6.4 F / cm 2 The following, and even more preferably, 6.3 F / cm 2 The following is the most preferred, and most preferably 6.0 F / cm 2 The following is true: The initial double-layer capacitance is 7.0 F / cm². 2 The following conditions are observed: increasing the amount of catalyst deposition increases the double layer capacity, and the oxygen overpotential tends to decrease even after prolonged energization.

[0025] In the electrode of this embodiment, 1 cm 2 The number of moles of La per unit is preferably 0.06 mmol or more and 1.1 mmol or less, more preferably 0.13 mmol or more and 0.91 mmol or less, and even more preferably 0.15 mmol or more and 0.68 mmol or less. 2 If the number of moles of La per unit is within the above range, the initial bilayer volume is 0.6 F / cm². 2 It tends to be easier to achieve "super" (highly competitive). 1cm 2 The number of moles of La per unit is the LaNi on an electrode with a defined area. x M y O 3-z The catalyst is dissolved in acid, and the concentration of La in the solution is measured using the ICP-AES method to calculate the mass of La contained on the electrode. This mass is then divided by the atomic weight of La (138.9) to obtain the number of moles, and then divided by the area of ​​the electrode. The area used in the calculation (cm²) is also used.2 ) is the geometric area of the electrode. For example, when an electrode with expanded metal as the base material is cut out to form a square with a length of 2 cm and a width of 2 cm when viewed from the thickness direction, its area is 4 cm 2 This will be described in the examples for the specific calculation method.

[0026] In the electrode of this embodiment, the capacitance per mmol of La is preferably 10 F or more and 25 F or less, more preferably 12 F or more and 23 F or less, and even more preferably 14 F or more and 21 F or less. When the capacitance per mmol of La is within the above range, there is a tendency to achieve a low oxygen overvoltage with a small amount of catalyst. When the capacitance per mmol of La is 10 F or more, the oxygen overvoltage per amount of catalyst adhesion tends to be low. When the capacitance per mmol of La is 25 F or less, the double-layer capacitance does not decrease even after long-term energization, and the oxygen overvoltage tends to be low. The capacitance per mmol of La is obtained by dividing the double-layer capacitance by the number of moles (mmol) of La per 1 cm 2 This can be determined by dividing by the number of moles (mmol) of La per 1 cm.

[0027] In this embodiment, the adhesion amount of LaNi x M y O 3-z on the base material is preferably more than 145 g / m 2 and 3500 g / m 2 or less, more preferably 200 g / m 2 or more and 3000 g / m 2 or less, and even more preferably 350 g / m 2 or more and 2500 g / m 2 or less. When the adhesion amount of LaNi x M y O 3-z is more than 145 g / m 2 , the oxygen overvoltage after long-term energization tends to be smaller. Also, when the adhesion amount of LaNi x M y O 3-z is 3500 g / m 2The following conditions are observed: increasing the amount of catalyst deposited increases the double layer capacity, and the oxygen overpotential tends to decrease even after prolonged energization. Area used to calculate the amount of deposit (m²) 2 ) is the geometric area of ​​the electrode. For example, for an electrode made of expanded metal, if the base material is cut to form a square with dimensions of 10 cm (0.1 m) in length and 10 cm (0.1 m) in width when viewed from the thickness direction, then its area is 0.01 m². 2 And then 1g of LaNi is added to the base material. x M y O 3-z If it is present, the amount of adhesion is 100g / m 2 This is the result. Note that the amount of LaNi deposited is calculated from a certain area of ​​the electrode. x M y O 3-z After completely removing the catalyst, metal powders such as Ni originating from the substrate were removed from the powder obtained by the removal using a magnet, and the attached LaNi x M y O 3-z This can be determined by obtaining a catalyst powder, weighing its mass using an electronic balance, and dividing the result by the value of the aforementioned fixed area of ​​the electrode. LaNi x M y O 3-z Various methods can be used to remove the catalyst, including using files such as precision files or ultra-fine files, using spatulas such as micro spatulas or wire brushes, etc., as these methods allow for removal without introducing foreign matter that cannot be removed by magnets.

[0028] The electrode of this embodiment can be used in practical applications as an anode for water electrolysis, and it is possible to provide an electrolytic cell for water electrolysis using the electrode of this embodiment as the anode, and a method for producing hydrogen using the water electrolysis anode. Water containing alkali may be used for water electrolysis.

[0029] (Method for preparing electrodes) The electrode of this embodiment is prepared by applying an aqueous solution (coating solution) containing a metal salt of La, Ni, and M (where M contains at least one of Nb, Ta, Sb, Ti, Mn, or Zr) to a substrate, drying and calcining, and then applying a predetermined mass of LaNi to the substrate. x M y O 3-z It can be prepared by forming a precursor and then calcining it.

[0030] As metal salts, water-soluble salts such as nitrates, oxynitrates, chlorides, oxalates, tartrates, acetates, and sulfates can be used. The metal salt may be anhydrous or hydrated. Instead of metal salts, La, Ni, and M may be replaced with aqueous dispersible sols of oxides or hydroxides. When Nb is used as M, it is preferable to use niobium oxalate or ammonium niobium oxalate from the viewpoint of solubility. Furthermore, when Sb is used as M, it is preferable to use antimony tartrate.

[0031] Adding organic ligands such as amino acids like glycine, or carboxylic acids like oxalic acid and tartaric acid to the coating solution results in LaNi exhibiting a low oxygen overpotential. x M y O 3-z This is preferable from the viewpoint of facilitating the preparation of the product. In particular, using a coating solution containing glycine and a metal nitrate makes it easier to prepare electrodes that exhibit lower oxygen overpotentials, making glycine a preferred organic ligand. In the preparation of the electrode of this embodiment, glycine / NO3 - If the process includes a step of calcining a mixture of La(NO3)3, Ni(NO3)2, and glycine in a molar ratio of 0.1 to 0.3, the initial double-layer volume is 0.6 F / cm². 2 This facilitates the preparation of electrodes, which is preferable. Glycine / NO3 - The process of calcining a mixture of La(NO3)3, Ni(NO3)2, and glycine having a molar ratio of 0.1 to 0.3 involves mixing La(NO3)3·6H2O, Ni(NO3)2·6H2O, and glycine with NO3 -This process involves applying an aqueous solution, formulated so that the molar ratio of glycine to glycine is between 0.1 and 0.3, to a substrate, drying it, and then firing it. (Glycine / NO3) - If the molar ratio is less than 0.1, a subcrystal consisting of La and Ni other than the perovskite crystalline phase may be obtained, and the oxygen overpotential may not be low. If it is 0.3 or less, the initial bilayer capacitance is 0.6 F / cm². 2 To prepare an electrode that is superior, it is preferable to be able to reduce the number of coating applications. In preparing the electrodes of this embodiment, from the viewpoint of increasing the capacitance per 1 mmol of La, glycine / NO3 - It is more preferable to include a step of calcining a mixture of La(NO3)3, Ni(NO3)2, and glycine having a molar ratio of 0.1 to 0.25. In the preparation of the electrode in this embodiment, the amount of gas generated due to glycine decomposition during firing is reduced, and the initial double-layer volume is 0.6 F / cm² with fewer coating applications. 2 From the perspective of enabling the preparation of ultra-high-performance electrodes, glycine / NO3 - It is even more preferable to include a step of calcining a mixture of La(NO3)3, Ni(NO3)2, and glycine having a molar ratio of 0.1 to 0.2.

[0032] In the preparation of the electrode of this embodiment, if the process includes a step of calcining a mixture of La(NO3)3, Ni(NO3)2, and compounds whose constituent elements are C, H, N, and O, which have carboxyl groups and amino groups, such as amino acids like glycine and aspartic acid, dipeptides like carnosine, and polypeptides like polylysine, then the LaNi of the combustion by-product gas (CO2, H2O, and N2) generated during calcination may be affected. x M y O 3-z Molar ratio (combustion by-product gas / LaNi x M y O 3-z It is preferable that the ratio is 5 or more and less than 12.6. Combustion by-product gas / LaNi x M y O 3-zWhen the molar ratio is 5 or higher, when the aqueous solution of the mixture is used as a coating solution for coating, drying, and firing, the deposits on the electrodes are less likely to dissolve or detach, and it tends to be easier to increase the amount of deposits on the electrodes by repeating the coating, drying, and firing process. Also, combustion by-product gas / LaNi x M y O 3-z When the molar ratio is less than 12.6, it becomes possible to increase the amount of material deposited in a single application, drying, and firing cycle when using an aqueous solution of the mixture as a coating solution. This tends to allow for the easy preparation of electrodes with a high amount of deposition in fewer applications. Combustion by-product gas / LaLi x M y O 3-z The specific method for calculating the molar ratio will be described later in the examples. Furthermore, the amount of combustion by-product gases (CO2, H2O, and N2) generated can be measured by thoroughly drying the coating solution at 100°C and then subjecting the resulting product to an organic elemental analyzer such as the Flash2000 manufactured by Thermo Fisher Scientific Inc. x M y O 3-z The amount produced can be calculated from the mass of the powder obtained by firing the product, which is obtained by thoroughly drying the coating solution at 100°C, under predetermined firing conditions. Therefore, the amount of combustion by-product gases (CO2, H2O, and N2) obtained by measurement and LaNi x M y O 3-z From the amount produced, combustion by-product gas / LaNi x M y O 3-z It is possible to calculate the molar ratio.

[0033] The concentration of an aqueous solution containing metal salts La, Ni, and M is LaNi x M y O 3-zA standard molality of 0.1 mol / kg solvent or more and 4.0 mol / kg solvent or less is preferred. A solvent concentration of 0.1 mol / kg or more allows for the preparation of electrodes with a predetermined amount of adhesion with fewer coating and firing cycles, which is preferred from the viewpoint of productivity. A solvent concentration of 4.0 mol / kg or less facilitates the dissolution of metal salts and organic ligands, which is preferred from the viewpoint of productivity of the coating solution. More preferably, the solvent concentration is 0.2 mol / kg solvent or more and 2.0 mol / kg solvent or less, even more preferably 0.3 mol / kg solvent or more and 2.0 mol / kg solvent or less, even more preferably 0.35 mol / kg solvent or more and 2.0 mol / kg solvent or less, and even more preferably 0.4 mol / kg solvent or more and 1.0 mol / kg solvent or less. Also, especially LaNi x M y O 3-z If M is Nb, then the concentration of an aqueous solution containing metal salts of La, Ni, and Nb is LaNi x Nb y O 3-z A standard molar concentration of 0.3 mol / kg or more and 4.0 mol / kg or less is preferred. For solvents of 0.3 mol / kg or more, 0.785 μm 2 Super 20μm 2 The sum of the areas of the following pores is 10 μm 2 More than 200μm 2 The following conditions are easily met: At solvent concentrations of 4.0 mol / kg or less, metal salts and organic ligands dissolve easily, which is preferable from the viewpoint of the productivity of the coating solution. More preferably, the solvent concentration is 0.35 mol / kg or more and 2.0 mol / kg or less, and even more preferably 0.4 mol / kg or more and 1.0 mol / kg or less.

[0034] The drying temperature after applying the coating solution to the substrate is preferably between 50°C and 200°C. A temperature of 50°C or higher is preferable from a productivity standpoint, as drying is completed within 3 minutes to 1 hour. A temperature of 200°C or lower is also preferable from a productivity standpoint, as the cooling time of the substrate after drying is shortened.

[0035] As a method for applying the coating solution to the substrate, the spray coating method is preferred. In particular, if the coating solution atomized from the spray nozzle dries appropriately and becomes highly viscous before it lands on the substrate, the coating film will not move on the substrate after landing, allowing for the formation of a uniform film thickness on the substrate, and making it easy to prepare electrodes that exhibit low oxygen overpotential even after prolonged energization.

[0036] The temperature for pre-firing the dried substrate is preferably between 300°C and 500°C. A temperature of 300°C or higher is preferable from the viewpoint of productivity, as pre-firing can be completed in 3 minutes to 1 hour. A temperature of 500°C or lower is preferable from the viewpoint of productivity, as the cooling time of the dried substrate is shortened.

[0037] Coating, drying, and calcination are performed as desired. x M y O 3-z This process may be repeated to adjust the electrode adhesion amount. The adhesion amount per application, drying, and calcination is 10 g / m². 2 More than 50g / m 2 The following conditions are preferable from a productivity standpoint, as they reduce the number of coating applications. Furthermore, the amount of adhesion per application, drying, and calcination is 10 g / m². 2 More than 20g / m 2 If the value is less than 0.785 μm 2 Super 20μm 2 The sum of the areas of the following pores is 10 μm 2 More than 20μm 2 The following is preferable as it makes the process easier.

[0038] The firing temperature can be between 500°C and 1000°C, but firing at 650°C or higher is preferable. Firing at 650°C or higher is preferable from a productivity standpoint because it makes it easy to prepare electrodes exhibiting low oxygen overpotential within a firing time of 10 minutes to 24 hours.

[0039] M may also be added by first applying a coating solution containing a water-dispersible sol of a metal salt, oxide, or hydroxide of La or Ni, drying and calcining the electrode, then applying a coating solution containing a water-dispersible sol of a metal salt, oxide, or hydroxide of M as a topcoat, drying and calcining the electrode, and finally calcining the electrode.

[0040] Alternatively, M may be added by first applying a coating solution containing a water-dispersible sol of a metal salt, oxide, or hydroxide of La or Ni, then drying, calcining, and firing the electrode, and then applying a coating solution containing a water-dispersible sol of a metal salt, oxide, or hydroxide of M as a topcoat, drying, calcining, and firing the electrode.

[0041] (electrolytic cell) Figure 1 shows an overall side view of an example of an electrolytic cell including an electrolytic cell equipped with the electrode of this embodiment as the anode. Figure 2 shows a cross-sectional view of the zero-gap structure of an electrolytic cell, including an electrolytic cell equipped with the electrode of this embodiment as the anode (a cross-sectional view of the inside of the electrolytic cell in the area of ​​the dashed rectangle shown in Figure 1). In this embodiment, the bipolar electrolytic cell 50 (see Figure 3) has a diaphragm 4 in contact with the anode 2a and cathode 2c to form a zero-gap structure Z (see Figure 2). Figure 3 shows an overview of the electrolytic apparatus used in the examples and comparative examples. Figure 4 shows an overview of the bipolar electrolytic cell used in the electrolytic test.

[0042] (element) As shown in Figure 1, in the bipolar electrolytic cell 50, the bipolar element 60 is positioned between the anode terminal element 51a and the cathode terminal element 51c, and the diaphragm 4 is positioned between the anode terminal element 51a and the bipolar element 60, between adjacent bipolar elements 60, and between the bipolar element 60 and the cathode terminal element 51c.

[0043] In this embodiment, the portion between the partition walls 1 between two adjacent bipolar elements 60 in the bipolar electrolytic cell 50, and the portion between the partition walls 1 between an adjacent bipolar element 60 and a terminal element, are referred to as the electrolytic cell 65. The electrolytic cell 65 includes the partition wall 1, anode chamber 5a, anode 2a, and diaphragm 4 of one element, and the cathode 2c, cathode chamber 5c, and partition wall 1 of the other element.

[0044] (electrode chamber) In the bipolar electrolytic cell 50 of this embodiment, as shown in Figure 2, the electrode chambers 5 through which the electrolyte passes are defined by a partition wall 1, an outer frame 3, and a diaphragm 4. Here, the electrode chamber 5 on the anode side of the partition wall 1 is the anode chamber 5a, and the electrode chamber 5 on the cathode side is the cathode chamber 5c. In this embodiment, both internal and external header configurations can be adopted for the header tube arrangement of the bipolar electrolytic cell, and the space occupied by the anode and cathode themselves may also be considered as a space inside the electrode chamber. Furthermore, in particular, if a gas-liquid separation box is provided, the space occupied by the gas-liquid separation box may also be considered as a space inside the electrode chamber.

[0045] (rib) In the bipolar electrolytic cell 65 for alkaline water electrolysis of this embodiment, it is preferable that the ribs 6 are physically connected to the electrodes 2. With this configuration, the ribs 6 act as a support for the electrodes 2, making it easier to maintain the zero-gap structure Z. It is also preferable that the ribs 6 are electrically connected to the partition wall 1. Furthermore, by providing the ribs 6, it is possible to reduce the convection generated in the electrode chamber 5 due to turbulence in the gas-liquid flow within the electrode chamber 5, thereby suppressing a localized rise in the electrolyte temperature. Here, electrodes may be provided on the rib, and a current collector, a conductive elastic body, and electrodes may be provided on the rib in this order.

[0046] In the aforementioned example of a bipolar electrolytic cell for alkaline water electrolysis, the cathode chamber employs a structure in which cathode ribs, cathode current collector, conductive elastic body, and cathode are stacked in that order, while the anode chamber employs a structure in which anode ribs and anode are stacked in that order. In the example of the bipolar electrolytic cell for alkaline water electrolysis described above, the cathode chamber employs the "cathode rib-cathode current collector-conductive elastic body-cathode" structure, and the anode chamber employs the "anode rib-anode" structure. However, the present invention is not limited to this, and the "anode rib-anode current collector-conductive elastic body-anode" structure may also be employed in the anode chamber. In detail, in the bipolar electrolytic cell for alkaline water electrolysis of this embodiment, it is preferable that ribs 6 (anode ribs, cathode ribs) are attached to the partition wall 1, as shown in Figure 2. It is preferable that the ribs (anode ribs, cathode ribs) not only serve to support the anode or cathode, but also to transmit the current from the partition wall to the anode or cathode.

[0047] In the bipolar electrolytic cell for alkaline water electrolysis of this embodiment, it is preferable that at least a portion of the ribs are conductive, and it is even more preferable that the entire rib is conductive. With this configuration, it is possible to suppress the rise in cell voltage due to electrode deflection.

[0048] Generally, conductive metals are used as the material for the ribs. For example, nickel-plated mild steel, stainless steel, and nickel can be used. It is especially preferable that the rib material be the same as the partition wall material, and nickel is the most preferable.

[0049] The spacing between adjacent anode ribs, or between adjacent cathode ribs, is determined by taking into account factors such as the electrolysis pressure and the pressure difference between the anode and cathode chambers.

[0050] If the spacing between anode ribs, or between adjacent cathode ribs, is too narrow, it not only hinders the flow of electrolyte and gas but also increases costs. A rib pitch of 10 mm or more allows for good gas escape to the back surface of the electrodes. If the spacing is too wide, it can cause deformation of the electrodes (anode and cathode) held in place by the slight pressure difference between the anode and cathode chambers, and can also increase electrical resistance due to a reduced number of anode and cathode ribs. A rib pitch of 150 mm or less makes the electrodes less prone to bending. The number of ribs, the length of the ribs, the angle between the ribs and the partition wall, the number of through holes, and the spacing (pitch) of the through holes in a given direction along the partition wall can be determined as appropriate, as long as the effects of the present invention are obtained. It is preferable that the ribs are provided parallel to a given direction along the partition wall (for example, the vertical direction, or, if the plan view shape of the partition wall is substantially rectangular, the same direction as one of the two pairs of opposite sides). The rib pitch of the anode rib and the rib pitch of the cathode rib may be the same or different, and it is preferable that both the rib pitch of the anode rib and the rib pitch of the cathode rib satisfy the above range.

[0051] Laser welding or similar methods are used to attach the anode ribs and cathode ribs to the partition walls.

[0052] Furthermore, the thickness of the ribs can be between 0.5 mm and 5 mm, taking into consideration cost, manufacturability, strength, etc., and while 1 mm to 2 mm is easy to use, it is not particularly limited to these dimensions.

[0053] The electrodes and current collectors are usually attached to the ribs by spot welding, but other methods such as laser welding may also be used, or they may be tied together using wire or string-like materials. The ribs are fixed to the bulkhead by means of spot welding, laser welding, etc., similar to the anode or cathode.

[0054] (Method of producing hydrogen) Next, a method for producing hydrogen by alkaline water electrolysis using the bipolar electrolytic cell of this embodiment will be described.

[0055] In this embodiment, hydrogen is produced at the cathode by performing water electrolysis by applying an electric current to a bipolar electrolytic cell equipped with the anode and cathode described above, through which an electrolyte is circulated. At this time, a fluctuating power source can be used as the power source. A fluctuating power source is a power source originating from a renewable energy power plant whose output fluctuates in increments of a few seconds to a few minutes, unlike a power source that has a stable output, such as grid power. The method of renewable energy generation is not particularly limited, but examples include solar power generation and wind power generation.

[0056] For example, in electrolysis using a bipolar electrolytic cell, cationic electrolytes in the electrolyte solution move from the anode chamber of one element through the diaphragm to the cathode chamber of the adjacent element, while anionic electrolytes move from the cathode chamber of one element through the diaphragm to the anode chamber of the adjacent element. Therefore, the current during electrolysis flows along the direction in which the elements are connected in series. In other words, the current flows through the diaphragm from the anode chamber of one element to the cathode chamber of the adjacent element. During electrolysis, oxygen gas is generated in the anode chamber and hydrogen gas is generated in the cathode chamber.

[0057] The bipolar electrolytic cell 65 for alkaline water electrolysis of this embodiment can be used in a bipolar electrolytic cell 50, an electrolytic apparatus 70 for alkaline water electrolysis, etc. An example of the above-mentioned electrolytic apparatus 70 for alkaline water electrolysis is an apparatus having the bipolar electrolytic cell 50 of this embodiment, a liquid transfer pump 71 for circulating the electrolyte, a gas-liquid separation tank 72 for separating the electrolyte from hydrogen and / or oxygen, and a water supply device for replenishing the water consumed by electrolysis.

[0058] The above-described electrolytic apparatus for alkaline water electrolysis may further include a rectifier 74, an oxygen concentration meter 75, a hydrogen concentration meter 76, a flow meter 77, a pressure gauge 78, a heat exchanger 79, a pressure control valve 80, and the like.

[0059] In the alkaline water electrolysis method using the above-described electrolytic apparatus for alkaline water electrolysis, the current density applied to the electrolytic cell is 4kA / m³. 2 ~20kA / m 2 Preferably, it is 6 kA / m2 ~15kA / m 2 It is even more preferable that this be the case. In particular, when using a fluctuating power supply, it is preferable to set the upper limit of the current density within the above range.

[0060] The electrodes, electrolytic cells, and hydrogen production methods of the present invention have been described above with reference to the drawings, but the electrodes, electrolytic cells, and hydrogen production methods of the present invention are not limited to the above examples, and the above embodiments can be modified as appropriate. [Examples]

[0061] The present invention will be described in detail below with reference to examples, but it goes without saying that the present invention is not limited to these examples and can be implemented in various ways within the scope of the gist of the present invention.

[0062] (Example A1) As a nickel porous substrate, a 10cm square piece of nickel expanded metal was prepared, measuring 10cm vertically and 10cm horizontally, with a width of SW 3.0mm, a length of LW 4.5mm, a thickness of 1.2mm, and an aperture ratio of 54%. This nickel expanded metal was blast-treated, then acid-treated in hydrochloric acid at 50°C and 6N for 6 hours, followed by washing with water and drying to prepare it as a coating substrate. 18.61 g of Ni(NO3)2·6H2O, 34.64 g of La(NO3)3·6H2O, and 8.29 g of glycine were dissolved in 200 g of pure water, and the mixture was transferred to a rectangular polyethylene container with a base of 6 cm x 10 cm and a height of 11 cm to form Solution A of Example A1. Ammonium niobium oxalate was dissolved in pure water to prepare 200 g of an aqueous solution of ammonium niobium oxalate with a Nb concentration of 80 mmol / kg, which was used as solution B in Example A1. The Nb concentration was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry). While stirring solution A of Example A1 with a magnetic stirrer, solution B of Example A1 was slowly mixed in to obtain the coating solution of Example A1. While stirring the coating solution, the substrate was placed vertically, and the lower half was slowly immersed in the coating solution and held for 5 seconds. Then, the substrate was lifted out, flipped over, and the upper half was slowly immersed in the coating solution and held for 5 seconds. After coating the entire surface of the substrate, the substrate was placed horizontally and excess coating solution was blown off with an air gun. Subsequently, it was dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the surface of the substrate. This coating, drying, and firing cycle was repeated 60 times. Afterward, it was fired again at 750°C for 1 hour, resulting in an adhesion amount of 502 g / m² to the coating substrate. 2 The electrode of Example A1 was obtained by forming a metal oxide layer.

[0063] (Example A2) A coating substrate was prepared in the same manner as in Example A1. Next, solution A with the composition shown in Table 1 and solution B with the composition shown in Table 2 were prepared. Solution B was prepared by adding pure water to Nb2O5 sol with a primary particle size of 5 nm or less, and the concentration of Nb was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry). Using a spray coating device (rCoater, sold by Asahi Sanac Co., Ltd.), solution A was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating the application, drying, and firing cycle of solution A six times, solution B was applied to both sides of the substrate using a spray coating device and dried at 60°C for 10 minutes. The mass increase of the substrate compared to before application of solution B was calculated to be 77 mg. Further firing was performed at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. This cycle of applying solution A six times and solution B once, drying, and baking was repeated five times, resulting in a total of 30 applications of solution A and 5 applications of solution B. Furthermore, it was baked at 650°C for 1 hour, resulting in an adhesion amount of 488g / m². 2 A metal oxide layer was formed to obtain the electrode of Example A2. The amount of metal oxide layer attached to the substrate was 4.88 g, and LaNi 0.85 O 2.775Since the mass of one mole of LaNi is 233.1g and the mass of one mole of Nb2O5 is 265.8g, applying 385mg of Nb2O5 results in LaNi 0.85 O 2.775 A mixture of Nb and LaNi was coated at a ratio of 0.15 moles per mole of Nb. 0.85 Nb 0.15 O 3.15 It was found that the electrodes were obtained.

[0064] (Example A3) The coating substrate was prepared in the same manner as in Example A1. Next, solutions A and B of Example A3 in Tables 1 and 2 were prepared. In the same manner as in Example A2, solution A was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating the application, drying, and firing cycle of solution A 25 times, solution B was applied to both sides of the substrate and dried at 60°C for 10 minutes. The mass increase relative to the substrate before application was calculated to be 14.6 mg. Further firing at 400°C for 10 minutes was performed to form a metal oxide layer on the substrate surface. Furthermore, it was baked at 700°C for 1 hour, resulting in an adhesion amount of 501 g / m². 2 The metal oxide layer was formed to obtain the electrode of Example A3. The amount of metal oxide layer attached to the substrate was 5.01 g, and LaNi 0.795 O 2.6925 Since the mass of one mole of LaNi is 228.6g and the mass of one mole of Nb2O5 is 265.8g, applying 14.6mg of Nb2O5 results in LaNi 0.795 O 2.6925 A ratio of 0.005 moles of Nb is applied to 1 mole, resulting in a composition of LaNi 0.795 Nb 0.005 O 2.705 It was found that the electrodes were obtained.

[0065] (Example A4) A coating substrate was prepared in the same manner as in Example A1. 116.3g of Ni(NO3)2·6H2O, 173.2g of La(NO3)3·6H2O, and 16.52g of glycine were dissolved in 200g of pure water to prepare Solution A of Example A4. Ammonium niobium oxalate was dissolved in pure water, and 30% hydrogen peroxide solution was added to prepare 200 g of an aqueous solution of ammonium niobium oxalate with hydrogen peroxide, resulting in a solution with an Nb concentration of 20 mmol / kg and an H2O2 / Nb molar ratio of 2.5. This solution was used as solution B in Example A4. The Nb concentration was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry). Solution A was delivered at a rate of 0.64 mL / min and solution B at a rate of 0.36 mL / min. The two solutions were mixed immediately before the spray coating device using a PEEK T-shaped reactor with an inner diameter of 1 mm (distributed by YMC Co., Ltd., Japan), and then supplied to the spray coating device at a delivery rate of 1 mL / min. Using the spray coating device, the mixture of solutions A and B was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating the application, drying, and firing cycle of the mixed solution of liquids A and B 13 times, the mixture was further fired at 700°C for 1 hour, resulting in an adhesion amount of 506 g / m². 2 A metal oxide layer was formed to obtain the electrode of Example A4. The density of solution A is 1.45 g / cm³. 3 Therefore, the density of solution B is 1 g / cm³. 3 Therefore, since solution A was mixed at a rate of 0.64 mL / min and solution B at a rate of 0.36 mL / min, the composition obtained by drying and calcining the mixture is LaNiNb 0.01 O 3.025 It turned out to be true.

[0066] (Example A5) The coating substrate was prepared in the same manner as in Example A1. Next, solutions A and B of Example A5 in Tables 1 and 2 were prepared. In the same manner as in Example A2, solution A was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating the application, drying, and firing cycle of solution A 16 times, solution B was applied to both sides of the substrate and dried at 60°C for 10 minutes. The mass increase relative to the substrate before application was calculated to be 54 mg. Further firing at 400°C for 10 minutes was performed to form a metal oxide layer on the substrate surface. Furthermore, it was baked at 700°C for 1 hour, resulting in an adhesion amount of 505g / m². 2 A metal oxide layer was formed to obtain the electrode of Example A5. The amount of metal oxide layer attached to the substrate was 5.05 g. Since the mass of 1 mole of LaNiO3 is 245.5 g and the mass of 1 mole of Nb2O5 is 265.8 g, by applying 54 mg of Nb2O5, the ratio of Nb to 1 mole of LaNiO3 was 0.02 moles, resulting in the composition LaNiNb. 0.02 O 3.05 It was found that the electrodes were obtained.

[0067] (Example A6) The coating substrate was prepared in the same manner as in Example A1. Next, solutions A and B of Example A6 in Tables 1 and 2 were prepared. Solution A was transferred to a polyethylene container measuring 13cm x 13cm at the base and 10cm in height. The substrate for coating was slowly placed in liquid A in a container with the substrate facing diagonally, completely immersed, and held for 5 seconds. Then the substrate was removed, turned on its side, and excess coating liquid was blown off with an air gun. After that, it was dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the surface of the substrate. This coating, drying, and firing cycle was repeated 20 times. When placing the substrate into the coating solution in the container, it was slowly placed at an angle to ensure that the voids in the metal oxide layer were completely replaced by the coating solution. Next, using a spray coating device, solution B was applied to both sides of the substrate and dried at 60°C for 10 minutes. The mass increase compared to the substrate before application was calculated to be 67.7 mg. Further firing was performed at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. This process of applying solution B, drying, and firing was repeated one more time. Afterward, it was further baked at 700°C for 1 hour, resulting in an adhesion amount of 514 g / m² on the coating substrate. 2 The metal oxide layer was formed to obtain the electrode of Example A6. The amount of metal oxide layer attached to the substrate was 5.14 g. Since the mass of 1 mole of LaNiO3 is 245.5 g and the mass of 1 mole of Nb2O5 is 265.8 g, by applying 135 mg of Nb2O5, the ratio of Nb to 1 mole of LaNiO3 was 0.05 moles, resulting in the composition LaNiNb. 0.05 O 3.125 It was found that the electrodes were obtained.

[0068] (Example A7) The coating substrate was prepared in the same manner as in Example A1. Next, solution A of Example A7 in Table 1 was prepared. In the same manner as in Example A2, solution A was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. The cycle of applying solution A, drying, and baking was repeated four times. Ammonium niobium oxalate was dissolved in pure water to prepare an aqueous solution of ammonium niobium oxalate with an Nb concentration of 310 mmol / kg, which was used as solution B in Example A7. This aqueous solution of ammonium niobium oxalate was transferred to a polyethylene container with a base of 13 cm x 13 cm and a height of 10 cm. A substrate with a metal oxide layer formed on its surface was completely immersed in solution B and then removed. After applying solution B to the entire surface of the substrate, the substrate was turned on its side, and a weak blast of air from an air gun was used to remove any solution B that was clogging the substrate's pores. After the air gun treatment, the mass of the substrate was measured, and it was found that 1.3g of solution B had been applied to the substrate. This substrate coated with solution B was dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes. This process of applying solution A four times and solution B once, drying, and baking is repeated five times, followed by further baking at 600°C for one hour, resulting in an adhesion amount of 526 g / m² on the substrate. 2 The electrode of Example A7 was obtained by forming a metal oxide layer. The amount adhering to the substrate was 5.26g, LaNi 1.1 O 3.15Since the mass of one mole of is 253.8 g and the mass of one mole of Nb2O5 is 265.8 g, applying a 1.3 g Nb concentration 310 mmol / kg aqueous solution of niobium oxalate five times results in LaNi 1.1 O 3.15 A mixture of LaNi is coated with Nb at a ratio of 0.1 moles per mole. 1.1 Nb 0.1 O 3.4 It was found that the electrodes were obtained.

[0069] (Example A8) The procedure was the same as in Example A5, except that the baking temperature was changed from 700°C for 1 hour to 750°C for 1 hour, resulting in an adhesion amount of 505 g / m². 2 The electrode of Example A8 was obtained by forming a metal oxide layer.

[0070] (Example A9) The coating substrate was prepared in the same manner as in Example A1. Next, solutions A and B of Example A9 in Tables 1 and 2 were prepared. In the same manner as in Example A2, solution A was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating the application, drying, and firing cycle of solution A 11 times, solution B was applied to both sides of the substrate and dried at 60°C for 10 minutes. The mass increase compared to the substrate before application was calculated to be 38 mg. Further firing was performed at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. Furthermore, it was baked at 700°C for 1 hour, resulting in an adhesion amount of 354 g / m². 2 The electrode of Example A9 was obtained by forming a metal oxide layer. The amount of metal oxide layer deposited on the substrate was 3.54 g. Since the mass of 1 mole of LaNiO3 is 245.5 g and the mass of 1 mole of Nb2O5 is 265.8 g, by coating 38 mg of Nb2O5, the ratio of Nb to 1 mole of LaNiO3 was 0.02 moles, resulting in the composition LaNiNb. 0.02 O 3.05 It was found that the electrodes were obtained.

[0071] (Example A10) The coating substrate was prepared in the same manner as in Example A1. Next, solutions A and B of Example A10 in Tables 1 and 2 were prepared. In the same manner as in Example A2, solution A was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating the application, drying, and firing cycle of solution A 13 times, solution B was applied to both sides of the substrate and dried at 60°C for 10 minutes. The mass increase compared to the substrate before application was calculated to be 43 mg. Further firing at 400°C for 10 minutes was performed to form a metal oxide layer on the substrate surface. Furthermore, it was baked at 700°C for 1 hour, resulting in an adhesion amount of 404 g / m². 2 The electrode of Example A10 was obtained by forming a metal oxide layer. The amount of metal oxide layer deposited on the substrate was 4.04 g. Since the mass of 1 mole of LaNiO3 is 245.5 g and the mass of 1 mole of Nb2O5 is 265.8 g, by coating 43 mg of Nb2O5, the ratio of Nb to 1 mole of LaNiO3 was 0.02 moles, resulting in the composition LaNiNb. 0.02 O 3.05 It was found that the electrodes were obtained.

[0072] (Comparative Example A1) As a nickel porous substrate, a 10cm square nickel expanded metal with a width of SW 3.0mm, a length of LW 4.5mm, a thickness of 1.2mm, and an aperture ratio of 54% was prepared. After blasting this nickel expanded metal, it was acid-treated in hydrochloric acid at 50°C and 6N for 6 hours, then washed with water and dried to prepare it as a coating substrate. Next, coating solutions were prepared by mixing lanthanum acetate pentahydrate and nickel nitrate hexahydrate to concentrations of 0.20 mol / L and 0.20 mol / L, respectively. A tray containing the above coating liquid was placed at the bottom of the coating roll, the coating liquid was soaked into the EPDM coating roll, another roll was placed above it so that the roll and the coating liquid were always in contact, and a PVC roller was placed on top of that to apply the coating liquid to the substrate (roll method). The substrate was quickly passed between two EPDM sponge rolls before the coating liquid dried. After drying at 50°C for 10 minutes, it was baked in a muffle oven at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating this roll coating, drying, and baking cycle 75 times, the coating was further baked at 600°C for 1 hour, resulting in an adhesion amount of 303 g / m². 2 A metal oxide layer was formed to obtain the electrode of Comparative Example A1.

[0073] (Comparative example A2) A coating substrate was prepared in the same manner as in Comparative Example A1. Next, lanthanum nitrate hexahydrate, nickel nitrate hexahydrate, ammonium niobium oxalate n hydrate, and glycine were mixed to concentrations of 0.20 mol / L, 0.16 mol / L, 0.04 mol / L, and 0.36 mol / L, respectively, to prepare the coating solution. Similar to Comparative Example A1, the roll coating, drying, and firing cycle was repeated 40 times using the roll method, followed by further firing at 700°C for 1 hour to form a metal oxide layer, resulting in an adhesion amount of 145 g / m². 2 An electrode for comparative example A2 was obtained.

[0074] (Example B1) As a nickel porous substrate, nickel expanded metal with a width of 3.0 mm, a length of 4.5 mm, a thickness of 1.2 mm, and an aperture ratio of 54% was prepared. After blasting this nickel expanded metal, a substrate measuring 10 cm in length and 10 cm in width was cut out, acid-treated in hydrochloric acid at 50°C and 6N for 6 hours, then washed with water and dried to be used as a substrate for coating. Next, solutions A and B with the compositions of Example B1 in Table 4 were prepared. Solution B was prepared by dissolving ammonium niobium oxalate in pure water, and the concentration of Nb was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry). Liquid A was placed in a rectangular polyethylene container with a base of 6 cm x 10 cm and a height of 11 cm. Liquid B was slowly mixed in while stirring with a magnetic stirrer to obtain the coating solution for Example B1. While stirring the coating solution, the substrate for coating was placed vertically, and the lower half was immersed in the coating solution. Then, the substrate was flipped over and the upper half was also immersed in the coating solution. After coating the entire surface of the substrate with the coating solution, the excess coating solution was blown off using an air gun while the substrate was still in the vertical position. Subsequently, the substrate was dried at 60°C for 10 minutes, and then fired at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating this coating, drying, and firing cycle 13 times, the coating is further fired at 800°C for 1 hour, resulting in an adhesion amount of 40 g / m² to the substrate. 2 A metal oxide layer was formed to obtain an anode for water electrolysis.

[0075] (Examples B2-6) The coating substrate was prepared in the same manner as in Example B1. After preparing solutions A and B with the compositions of Examples B2-6 in Table 4, solutions A and B were mixed in a rectangular polyethylene container in the same manner as in Example B1 to prepare the coating solutions of Examples B2-6. The coating, drying, and firing cycle was repeated in the same manner as in Example B1, followed by firing at 800°C for 1 hour, resulting in an adhesion amount of 40 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain anodes for water electrolysis as shown in Examples B2 to B6.

[0076] (Example B7) Dissolve 9.30g of Ni(NO3)2·6H2O, 34.64g of La(NO3)3·6H2O, 30.03g of glycine (C2H5NO2), and 13.78g of Mn(NO3)2·6H2O in 400g of pure water to prepare the coating solution of Example B7. Transfer this coating solution to a polyethylene container with a base of 13cm x 13cm and a height of 10cm. A substrate for coating was prepared in the same manner as in Example B1. The substrate was completely immersed in the coating solution in the container and then removed. After applying the coating solution to the entire surface of the substrate, the substrate was turned upright and excess coating solution was blown off using an air gun. Subsequently, the substrate was dried at 60°C for 10 minutes, and then fired at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating this coating, drying, and firing cycle 13 times, the coating is further fired at 800°C for 1 hour, resulting in an adhesion amount of 40 g / m² to the substrate. 2 A metal oxide layer was formed to obtain an anode for water electrolysis.

[0077] (Example B8) 18.61 g of Ni(NO3)2·6H2O, 34.64 g of La(NO3)3·6H2O, and 27.63 g of glycine were dissolved in 200 g of pure water to prepare solution A of Example B8. 200 g of TiO2 sol with a primary particle size of 10 nm was diluted with pure water to prepare solution B of Example B8, with a Ti concentration of 80 mmol / kg. Similar to Example B1, Solution A and Solution B were mixed in a rectangular polyethylene container to obtain the coating solution for Example B8. After repeating the coating, drying, and baking cycle as in Example B1, the solution was baked at 800°C for 1 hour, resulting in an adhesion amount of 40 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example B8.

[0078] (Example B9) The coating solution for Example B9 was prepared by dissolving 20.93 g of Ni(NO3)2·6H2O, 34.64 g of La(NO3)3·6H2O, 30.03 g of glycine, and 2.14 g of ZrO(NO3)2·2H2O in 400 g of pure water. Subsequently, the anode for water electrolysis in Example B9 was obtained in the same manner as in Example B7.

[0079] (Example B10) The coating solution for Example B10 was prepared by dissolving 26.75 g of Ni(NO3)2·6H2O, 34.64 g of La(NO3)3·6H2O, 31.83 g of glycine, and 1.43 g of TaCl5 in 400 g of pure water. Subsequently, the anode for water electrolysis of Example B10 was obtained in the same manner as in Example B7.

[0080] (Example B11) 17.45 g of Ni(NO3)2·6H2O, 34.64 g of La(NO3)3·6H2O, and 27.03 g of glycine were dissolved in 200 g of pure water to prepare solution A of Example B11. Antimony tartrate was dissolved in pure water to prepare 200 g of antimony tartrate solution with an Sb concentration of 20 mmol / kg, which was prepared to prepare solution B of Example B11. The Sb concentration was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry). Similar to Example B1, Solution A and Solution B were mixed in a rectangular polyethylene container to obtain the coating solution for Example B11. After repeating the coating, drying, and baking cycle as in Example B1, the solution was baked at 800°C for 1 hour, resulting in an adhesion amount of 40 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example B11.

[0081] (Example B12) The coating solution for Example B12 was prepared by dissolving 23.26 g of Ni(NO3)2·6H2O, 34.64 g of La(NO3)3·6H2O, and 30.03 g of glycine in 400 g of pure water. A substrate for coating was prepared in the same manner as in Example B1. Using a spray coating device (rCoater sold by Asahi Sanac Co., Ltd.), the coating solution was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. This coating, drying, and firing cycle was repeated 24 times. Furthermore, Nb2O5 sols with a primary particle size of 5 nm or less were diluted to prepare Nb2O5 sols with an Nb concentration of 200 mmol / kg sol. After applying this Nb2O5 sol to both sides using a spray coating device and drying at 60°C for 10 minutes, the weight increase relative to the substrate before coating was calculated to be 38 mg. The amount of LaNiO3 adhering to the substrate was 1.4 g, the weight of 1 mole of LaNiO3 is 245.6 g, and the weight of 1 mole of Nb2O5 is 265.2 g. Therefore, it was determined that by applying 38 mg of Nb2O5, the amount of Nb applied was equivalent to applying 0.05 moles of Nb to 1 mole of LaNiO3. The substrate, dried at 60°C for 10 minutes, was baked at 400°C for 10 minutes, and then further baked at 800°C for 1 hour, resulting in an adhesion amount of 144 g / m².2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example B12.

[0082] (Example B13) The coating solution for Example B13 was prepared in the same manner as in Example B12. Then, this coating solution was transferred to a polyethylene container with a base of 13 cm x 13 cm and a height of 10 cm. A substrate for coating was prepared in the same manner as in Example B1. The substrate was completely immersed in the coating solution in a container and then removed. After applying the coating solution to the entire surface of the substrate, the substrate was turned on its side and excess coating solution was blown off with an air gun. Subsequently, it was dried at 60°C for 10 minutes and then baked at 400°C for 10 minutes to form a metal oxide layer on the surface of the substrate. This coating, drying, and firing cycle was repeated 24 times. A niobium oxalate aqueous solution was prepared by dissolving ammonium oxalate in pure water to obtain a solution with an Nb concentration of 43.8 mmol / kg. This niobium oxalate aqueous solution was transferred to a polyethylene container with a base of 13 cm x 13 cm and a height of 10 cm. A substrate with a metal oxide layer formed on its surface was completely immersed in an aqueous solution of ammonium oxalate and then removed. After applying the coating solution to the entire surface of the substrate, the substrate was turned on its side, and a weak breeze was applied using an air gun to remove any coating solution that was clogging the pores of the substrate. When the weight of the substrate was measured after the air gun treatment, it was found that 1.3 g of aqueous solution of ammonium oxalate had been applied to the substrate. The amount of LaNiO3 attached to the substrate was 1.4 g, and since the weight of 1 mole of LaNiO3 is 245.6 g, it was determined that by applying 1.3 g of aqueous solution of ammonium oxalate with an Nb concentration of 43.8 mmol / kg, Nb was applied at a ratio of 0.01 moles of Nb to 1 mole of LaNiO3. A substrate coated with an aqueous solution of niobium oxalate was dried at 60°C for 10 minutes, then baked at 400°C for 10 minutes, and further baked at 800°C for 1 hour, resulting in a coating weight of 141 g / m². 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example B13.

[0083] (Example B14) In the same manner as in Example B13, the drying and firing cycle was repeated 24 times, followed by firing at 800°C for 1 hour to form a metal oxide layer on the substrate surface. Ammonium niobium oxalate was dissolved in pure water to prepare an aqueous solution of ammonium niobium oxalate with an Nb concentration of 87.7 mmol / kg. This aqueous solution of ammonium niobium oxalate was transferred to a polyethylene container with a base of 13 cm x 13 cm and a height of 10 cm. A substrate with a metal oxide layer formed on its surface was completely immersed in an aqueous solution of ammonium oxalate and then removed. After applying the coating solution to the entire surface of the substrate, the substrate was turned on its side, and a weak blast of air from an air gun was applied to remove any coating solution clogging the substrate's pores. After the air gun treatment, the weight of the substrate was measured, and it was found that 1.3 g of aqueous solution of ammonium oxalate had been applied to the substrate. The amount of LaNiO3 adhering to the substrate was 1.4 g, and since the weight of 1 mole of LaNiO3 is 245.6 g, it was determined that applying 1.3 g of aqueous solution of ammonium oxalate with an Nb concentration of 87.7 mmol / kg resulted in the application of Nb at a ratio of 0.02 moles per mole of LaNiO3. A substrate coated with an aqueous solution of niobium oxalate was dried at 60°C for 10 minutes, then baked at 400°C for 10 minutes, and further baked at 800°C for 1 hour, resulting in an adhesion amount of 142 g / m². 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example B14.

[0084] (Example B15) In the same manner as in Example B13, the drying and firing cycle was repeated 33 times, followed by firing at 800°C for 1 hour to form a metal oxide layer on the substrate surface. Subsequently, an aqueous solution of niobium oxalate with a Nb concentration of 125 mmol / kg was prepared. Using the same method as in Example B14, Nb was applied at a ratio of 0.02 moles per 1 mole of LaNiO3, dried at 60°C for 10 minutes, then calcined at 400°C for 10 minutes, and further calcined at 800°C for 1 hour, resulting in a deposition amount of 202 g / m². 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example B15.

[0085] (Example C1) Solutions A and B with the compositions of Example C1 in Table 6 were prepared. Solution B was prepared by dissolving ammonium niobium oxalate in pure water, and the concentration of Nb was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry). Liquid A was placed in a rectangular polyethylene container with a base of 6 cm x 10 cm and a height of 11 cm. Liquid B was slowly mixed in while stirring with a magnetic stirrer to obtain the coating solution for Example C1. As a nickel porous substrate, nickel expanded metal with a width of 3.0 mm, a length of 4.5 mm, a thickness of 1.2 mm, and an aperture ratio of 54% was prepared. This nickel expanded metal was blast-treated using #100 white fused alumina abrasive, then acid-treated in hydrochloric acid at 50°C and 6N for 6 hours, followed by rinsing with water and drying to prepare it as a coating substrate. The substrate was placed vertically in the coating solution in a container, with the lower half immersed in the solution. Then, the substrate was lifted out, flipped over, and the upper half was also immersed in the solution, thus coating the entire surface of the substrate. After that, the substrate was turned horizontally, and excess coating solution was blown off with an air gun. Subsequently, it was dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the surface of the substrate. This coating, drying, and firing cycle was repeated 50 times. Afterward, it was fired again at 800°C for 1 hour, resulting in an adhesion amount of 503 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C1.

[0086] (Example C2) The procedure was the same as in Example C1, except that solutions A and B with the compositions of Example C2 in Table 6 were prepared, and the coating, drying, and firing cycle was repeated 33 times. After that, it was further fired at 800°C for 1 hour, resulting in an adhesion amount of 496 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C2.

[0087] (Example C3) The procedure was the same as in Example C1, except that solutions A and B with the compositions of Example C3 in Table 6 were prepared, and the coating, drying, and firing cycle was repeated 25 times. After that, it was further fired at 750°C for 1 hour, resulting in an adhesion amount of 498 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C3.

[0088] (Example C4) The coating solution for Example C4 was prepared by dissolving 34.89 g of Ni(NO3)2·6H2O, 51.96 g of La(NO3)3·6H2O, and 45.04 g of glycine in 400 g of pure water. This coating solution was then transferred to a polyethylene container with a base of 13 cm x 13 cm and a height of 10 cm. The substrate was prepared in the same manner as in Example C1. The substrate was completely immersed in the coating solution in the container, then the substrate was removed, turned on its side, and excess coating solution was blown off with an air gun. After that, it was dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. This coating, drying, and baking cycle was repeated 49 times. Ammonium niobium oxalate was dissolved in pure water to prepare an aqueous solution of ammonium niobium oxalate with an Nb concentration of 157 mmol / kg. This aqueous solution of ammonium niobium oxalate was transferred to a polyethylene container with a base of 13 cm x 13 cm and a height of 10 cm. A substrate with a metal oxide layer formed on its surface was completely immersed in an aqueous solution of ammonium oxalate and then removed. After applying the coating solution to the entire surface of the substrate, the substrate was turned on its side, and a weak breeze was applied using an air gun to remove any coating solution that was clogging the substrate's pores. When the weight of the substrate was measured after the air gun treatment, it was found that 1.3 g of aqueous solution of ammonium oxalate had been applied to the substrate. The amount of LaNiO3 attached to the substrate was 5.0 g, and since the weight of 1 mole of LaNiO3 is 245.6 g, it was determined that by applying 1.3 g of aqueous solution of ammonium oxalate with an Nb concentration of 157 mmol / kg, Nb was applied at a ratio of 0.01 moles of Nb to 1 mole of LaNiO3. A substrate coated with an aqueous solution of niobium oxalate was dried at 60°C for 10 minutes, then baked at 400°C for 10 minutes, and further baked at 800°C for 1 hour, resulting in a coating weight of 512 g / m². 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C4.

[0089] (Example C5) The coating solution for Example C5 was prepared by dissolving 40.71 g of Ni(NO3)2·6H2O, 60.62 g of La(NO3)3·6H2O, and 52.55 g of glycine in 400 g of pure water. This coating solution was then transferred to a polyethylene container with a base of 13 cm x 13 cm and a height of 10 cm. Similar to Example C4, the substrate was completely immersed in the coating solution in the container, then the substrate was removed, turned on its side, and excess coating solution was blown off with an air gun. After that, it was dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. This coating, drying, and baking cycle was repeated 32 times. Ammonium niobium oxalate was dissolved in pure water to prepare an aqueous solution of ammonium niobium oxalate with an Nb concentration of 261 mmol / kg. This aqueous solution of ammonium niobium oxalate was transferred to a polyethylene container with a base of 13 cm x 13 cm and a height of 10 cm. A substrate with a metal oxide layer formed on its surface was completely immersed in an aqueous solution of niobium oxalate and then removed. After applying the coating solution to the entire surface of the substrate, the substrate was turned on its side, and a weak breeze was applied using an air gun to remove any coating solution clogging the substrate's pores. After the air gun treatment, the weight of the substrate was measured, and it was found that 1.3g of aqueous solution of niobium oxalate had been applied to the substrate. The substrate coated with aqueous solution of niobium oxalate was dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes. This process of applying 1.3g of aqueous solution of niobium oxalate, drying at 60°C for 10 minutes, and baking at 400°C for 10 minutes was repeated a total of three times, followed by baking at 800°C for 1 hour, resulting in a coating amount of 492g / m². 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C5. Since the amount of LaNiO3 attached to the substrate was 5.0 g, and the weight of 1 mole of LaNiO3 is 245.6 g, it was determined that by applying a total of 3.9 g of niobium oxalate aqueous solution with a Nb concentration of 261 mmol / kg (1.3 g) three times, the Nb was applied at a ratio of 0.05 moles per mole of LaNiO3.

[0090] (Example C6) The procedure was the same as in Example C1, except that solutions A and B with the compositions of Example C6 in Table 6 were prepared, and the coating, drying, and firing cycle was repeated 24 times. After that, it was further fired at 750°C for 1 hour, resulting in an adhesion amount of 486 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C6.

[0091] (Example C7) Dissolve 18.61g of Ni(NO3)2·6H2O, 69.28g of La(NO3)3·6H2O, 60.06g of glycine (C2H5NO2), and 27.56g of Mn(NO3)2·6H2O in 400g of pure water to prepare the coating solution of Example C7. Transfer this coating solution to a polyethylene container with a base of 13cm x 13cm and a height of 10cm. A substrate for coating was prepared in the same manner as in Example C1. The substrate was completely immersed in the coating solution in the container and then removed. After applying the coating solution to the entire surface of the substrate, the substrate was turned on its side and excess coating solution was blown off using an air gun. Subsequently, the substrate was dried at 60°C for 10 minutes, and then fired at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating this coating, drying, and firing cycle 25 times, the coating is further fired at 750°C for 1 hour, resulting in an adhesion amount of 508 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C7.

[0092] (Example C8) 37.22 g of Ni(NO3)2·6H2O, 69.28 g of La(NO3)3·6H2O, and 55.25 g of glycine were dissolved in 200 g of pure water to prepare Solution A of Example C8. 200 g of TiO2 sol with a primary particle size of 10 nm was diluted with pure water to prepare a Ti concentration of 160 mmol / kg sol, which was prepared as Solution B of Example C8. Similar to Example C1, Solution A and Solution B were mixed in a rectangular polyethylene container to obtain the coating solution for Example C8. A coating substrate was prepared in the same manner as in Example C1. The coating solution was applied to this substrate using the same method as in Example C1, followed by drying at 60°C for 10 minutes and baking at 400°C for 10 minutes. This cycle was repeated 26 times. Afterward, the substrate was further baked at 750°C for 1 hour, resulting in an adhesion amount of 496 g / m² to the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C8.

[0093] (Example C9) Dissolve 41.87g of Ni(NO3)2·6H2O, 69.28g of La(NO3)3·6H2O, 60.06g of glycine, and 4.28g of ZrO(NO3)2·2H2O in 400g of pure water to prepare the coating solution for Example C9. Transfer this coating solution to a polyethylene container with a base of 13cm x 13cm and a height of 10cm. A coating substrate was prepared in the same manner as in Example C1. The coating solution was applied to this substrate in the same manner as in Example C7, followed by drying at 60°C for 10 minutes and baking at 400°C for 10 minutes. This cycle was repeated 28 times. After that, it was baked again at 750°C for 1 hour, resulting in an adhesion amount of 502 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C9.

[0094] (Example C10) 53.50 g of Ni(NO3)2·6H2O, 69.28 g of La(NO3)3·6H2O, and 63.66 g of glycine were dissolved in 200 g of pure water to prepare solution A of Example C10. 2.87 g of TaCl5 was dissolved in 200 g of pure water to prepare solution B of Example C10. Similar to Example C1, Solution A and Solution B were mixed in a rectangular polyethylene container to obtain the coating solution for Example C10. A coating substrate was prepared in the same manner as in Example C1. The coating solution was applied to this substrate using the same method as in Example C1, followed by drying at 60°C for 10 minutes and baking at 400°C for 10 minutes. This cycle was repeated 25 times. Afterward, the substrate was further baked at 750°C for 1 hour, resulting in an adhesion amount of 498 g / m² to the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C10.

[0095] (Example C11) 34.89 g of Ni(NO3)2·6H2O, 69.28 g of La(NO3)3·6H2O, and 54.06 g of glycine were dissolved in 200 g of pure water to prepare Solution A of Example C11. Antimony tartrate was dissolved in pure water to prepare 200 g of antimony tartrate solution with an Sb concentration of 40 mmol / kg, which was prepared as Solution B of Example C11. The Sb concentration was confirmed by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). Similar to Example C1, Solution A and Solution B were mixed in a rectangular polyethylene container to obtain the coating solution for Example C11. A coating substrate was prepared in the same manner as in Example C1. The coating solution was applied to this substrate using the same method as in Example C1, followed by drying at 60°C for 10 minutes and baking at 400°C for 10 minutes. This cycle was repeated 27 times. Afterward, the substrate was further baked at 750°C for 1 hour, resulting in an adhesion amount of 504 g / m² to the coating substrate. 2 A metal oxide layer was formed to obtain the anode for water electrolysis in Example C11.

[0096] (Example D1) As a nickel porous substrate, nickel expanded metal with a width of 3.0 mm, a length of 4.5 mm, a thickness of 1.2 mm, and an aperture ratio of 54% was prepared. After blasting this nickel expanded metal, a substrate measuring 10 cm in length and 10 cm in width was cut out, acid-treated in hydrochloric acid at 50°C and 6N for 6 hours, then washed with water and dried to be used as a substrate for coating. The coating solution for Example D1 was prepared by dissolving 186.1g of Ni(NO3)2·6H2O, 692.8g of La(NO3)3·6H2O, 90.08g of glycine (C2H5NO2), and 275.6g of Mn(NO3)2·6H2O in 400g of pure water. Using a spray coating device (rCoater sold by Asahi Sanac Co., Ltd.), the coating solution of Example D1 was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. The coating solution was applied, dried, and baked 20 times, and then baked again at 700°C for 1 hour, resulting in an adhesion amount of 1001 g / m². 2 A metal oxide layer was formed to obtain the electrode of Example D1.

[0097] (Example D2) 200 g of pure water was mixed with 372.2 g of Ni(NO3)2·6H2O, 692.8 g of La(NO3)3·6H2O, 99.45 g of glycine, and 200 g of TiO2 sol with a Ti concentration of 1.6 mol / kg sol. The suspension was dispersed using a T18 Digital Ultra-Turrax homogenizer (equipped with an S18N-19G shaft generator) sold by IKA Japan Co., Ltd., to obtain the coating solution for Example D2. Similar to Example D1, the coating solution of Example D2 was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. The coating solution was applied, dried, and baked 15 times, followed by baking at 700°C for 1 hour, resulting in an adhesion amount of 752 g / m². 2 A metal oxide layer was formed to obtain the electrode of Example D2.

[0098] (Example D3) The coating solution for Example D3 was prepared by dissolving 418.7g of Ni(NO3)2·6H2O, 692.8g of La(NO3)3·6H2O, 102.1g of glycine, and 42.76g of ZrO(NO3)2·2H2O in 400g of pure water. Similar to Example D1, the coating solution of Example D3 was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. The coating solution was applied, dried, and baked 30 times, followed by baking at 700°C for 1 hour, resulting in an adhesion amount of 1505 g / m². 2 A metal oxide layer was formed to obtain the electrode of Example D3.

[0099] (Example D4) 535.0 g of Ni(NO3)2·6H2O, 692.8 g of La(NO3)3·6H2O, 70.03 g of glycine, and 28.66 g of TaCl5 were mixed in 400 g of pure water, and the suspension was dispersed using a T18 Digital Ultra-Turrax homogenizer (equipped with an S18N-19G shaft generator) sold by IKA Japan Co., Ltd. to obtain the coating solution for Example D4. Similar to Example D1, the coating solution of Example D4 was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. The coating solution was applied, dried, and baked 40 times, followed by baking at 700°C for 1 hour, resulting in an adhesion amount of 2006 g / m². 2 A metal oxide layer was formed to obtain the electrode of Example D4.

[0100] (Example D5) As a nickel porous substrate, nickel expanded metal with a width of 3.0 mm, a length of 4.5 mm, a thickness of 1.2 mm, and an aperture ratio of 54% was prepared. After blasting this nickel expanded metal, a substrate measuring 10 cm in length and 10 cm in width was cut out, acid-treated in hydrochloric acid at 50°C and 6N for 6 hours, then washed with water and dried to be used as a substrate for coating. 39.54 g of Ni(NO3)2·6H2O, 69.28 g of La(NO3)3·6H2O, and 10.81 g of glycine were dissolved in 200 g of pure water to prepare Solution A of Example D5. Antimony tartrate was dissolved in pure water to prepare an antimony tartrate solution with an Sb concentration of 40 mmol / kg, which was prepared to prepare Solution B of Example D5. The Sb concentration was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry). Liquid A was placed in a rectangular polyethylene container with a base of 6 cm x 10 cm and a height of 11 cm. Liquid B was slowly mixed in while stirring with a magnetic stirrer to obtain the coating solution for Example D5. While stirring the coating solution, the substrate was placed vertically, and the lower half was immersed in the coating solution. Then, the substrate was flipped over and the upper half was also immersed in the coating solution. After the coating solution was applied to the entire surface of the substrate, the substrate was placed horizontally, and excess coating solution was blown off using an air gun. Subsequently, the substrate was dried at 60°C for 10 minutes, and then fired at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. After repeating this coating, drying, and firing cycle 50 times, the coating is further fired at 700°C for 1 hour, resulting in an adhesion amount of 503 g / m² on the coating substrate. 2 A metal oxide layer was formed to obtain the electrode of Example D5.

[0101] (Example D6) 164.7 g of pure water was mixed with 488.5 g of Ni(NO3)2·6H2O, 692.8 g of La(NO3)3·6H2O, 70.03 g of glycine, and 235.3 g of an aqueous solution of niobium oxalate with an Nb concentration of 0.34 mol / kg. The suspension was dispersed using a T18 Digital Ultra-Turrax homogenizer (equipped with an S18N-19G shaft generator) sold by IKA Japan Co., Ltd., to obtain the coating solution for Example D6. Similar to Example D1, the coating solution of Example D6 was applied to both sides of the substrate, dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface. The coating solution was applied, dried, and baked 20 times, and then baked again at 700°C for 1 hour, resulting in an adhesion amount of 1004 g / m². 2 A metal oxide layer was formed to obtain the electrode of Example D6.

[0102] (Example D7) The procedure was carried out in the same manner as in Example D6, except that the coating, drying, and firing cycle of the coating solution was repeated 30 times, resulting in a coating amount of 1507 g / m². 2 A metal oxide layer was formed to obtain the electrode of Example D7.

[0103] (Example D8) The procedure was carried out in the same manner as in Example D6, except that the coating, drying, and firing cycle of the coating solution was repeated 40 times, resulting in a coating amount of 2009 g / m².2 A metal oxide layer was formed to obtain the electrode of Example D8.

[0104] (Example D9) 465.2 g of Ni(NO3)2·6H2O, 692.8 g of La(NO3)3·6H2O, 90.08 g of glycine, and 94.12 g of an ammonium niobium oxalate aqueous solution with a Nb concentration of 0.34 mol / kg were mixed in 305.9 g of pure water, and the suspension was dispersed using an IKA Japan Co., Ltd. sold T18 digital ultra turrax homogenizer (equipped with an S18N-19G shaft generator) to obtain the coating solution of Example D9. Similar to Example D1, after applying the coating solution of Example D9 to both sides of the substrate, it was dried at 60 °C for 10 minutes, and further fired at 400 °C for 10 minutes to form a metal oxide layer on the substrate surface. The cycle of coating, drying, and firing of the coating solution was repeated 20 times, and further fired at 700 °C for 1 hour to form a metal oxide layer with an adhesion amount of 1005 g / m 2 to obtain the electrode of Example D9.

[0105] (Example D10) The coating, drying, and firing cycles of the coating solution were repeated 50 times, and the procedure was carried out in the same manner as in Example D9 to form a metal oxide layer with an adhesion amount of 2500 g / m 2 to obtain the electrode of Example D10.

[0106] (Example D11) The coating, drying, and firing cycles of the coating solution were repeated 60 times, and the procedure was carried out in the same manner as in Example D9 to form a metal oxide layer with an adhesion amount of 3000 g / m 2 to obtain the electrode of Example D11.

[0107] (Example D12) As a nickel porous substrate, nickel expanded metal with SW 3.0 mm, LW 4.5 mm, thickness 1.2 mm, and porosity 54% was prepared. After subjecting this nickel expanded metal to blasting treatment, a substrate with a size of 10 cm in length and 10 cm in width was cut out, acid-treated in 50 °C 6N hydrochloric acid for 6 hours, then washed with water and dried to obtain a substrate for coating. 26.75 g of Ni(NO3)2·6H2O, 34.64 g of La(NO3)3·6H2O, and 3.99 g of aspartic acid were dissolved in 200 g of pure water, and the mixture was transferred to a rectangular polyethylene container with a base of 6 cm x 10 cm and a height of 11 cm to form solution A of Example D12. Ammonium niobium oxalate was dissolved in pure water to prepare 200 g of an aqueous solution of ammonium niobium oxalate with a Nb concentration of 20 mmol / kg, which was used as solution B in Example D12. The Nb concentration was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry). While stirring solution A of Example D12 with a magnetic stirrer, solution B of Example D12 was slowly mixed in to obtain the coating solution of Example D12. While stirring the coating solution, the substrate was placed vertically, and the lower half was slowly immersed in the coating solution and held for 5 seconds. Then, the substrate was lifted out, flipped over, and the upper half was slowly immersed in the coating solution and held for 5 seconds. After coating the entire surface of the substrate, the substrate was placed horizontally and excess coating solution was blown off with an air gun. Subsequently, it was dried at 60°C for 10 minutes, and then baked at 400°C for 10 minutes to form a metal oxide layer on the surface of the substrate. This coating, drying, and firing cycle was repeated 60 times. Afterward, it was fired again at 700°C for 1 hour, resulting in an adhesion amount of 505 g / m² on the substrate. 2 A metal oxide layer was formed to obtain the electrode of Example D12.

[0108] (Method for measuring the oxygen overpotential and double-layer capacitance of electrodes initially and after 500 hours of energization) The oxygen overpotential of the electrodes was measured using the following procedure. The test electrode was cut to form a 2cm x 2cm square when viewed from the thickness direction, and fixed to a nickel rod coated with PTFE using nickel screws. A platinum mesh was used as the counter electrode, and the current density was 6kA / m² in a 32% by mass sodium hydroxide aqueous solution at 80°C. 2 Electrolysis was performed and the oxygen overpotential was measured. The current density was calculated using an electrode area of ​​2 × 2 = 4 cm². 2The oxygen overpotential was calculated as follows. To eliminate the effect of ohmic loss due to liquid resistance, the oxygen overpotential was measured using a three-electrode method with a Lugin tube. The distance between the tip of the Lugin tube and the anode was always fixed at 1 mm. A Solartron 1470E system potentiometer galvanostat was used as the oxygen overpotential measurement device. Silver-silver chloride (Ag / AgCl) was used as the reference electrode for the three-electrode method. The electrolyte resistance that could not be completely eliminated even with the three-electrode method was measured using the AC impedance method, and the oxygen overpotential was corrected based on the measured electrolyte resistance. After obtaining a Cole-Cole plot plotting the real and imaginary parts using a Solartron 1255B frequency response analyzer, the electrolyte resistance R was calculated using the equivalent circuit fitting model shown in Figure 5 with the analysis software Zview (distributed by Scribner Associates, Inc.). s and double layer capacitance C dl The following was calculated. In Figure 5, f is the peak frequency, R f R is oxide film resistance, ct This represents the charge transfer resistance. Double-layer capacitance C dl This was calculated using the following formula.

number

[0109] (1 cm of the electrode after 500 hours of energization) 2 (Method for measuring the number of moles of La per unit) Current density 6kA / m 2Test electrode after 500 hours of electrolysis (2cm x 2cm, 4cm area) 2 ) from an area of ​​2cm² 2 A sample measuring 1 cm x 2 cm was cut out and sealed in a sealed container with a solution consisting of 6 mL of ultrapure water, 4.5 mL of 30% hydrochloric acid, and 1.5 mL of 68% nitric acid. The container was heated at 95°C for 30 minutes to dissolve the entire electrode catalyst and a portion of the substrate. First, the solution was diluted by adding ultrapure water until the total mass was 100 g. Next, 1 g of the diluted solution was diluted with 49 g of ultrapure water, and the concentration of La was measured by ICP-AES (inductively coupled plasma atomic emission spectrometry). From the determined La concentration and dilution ratio, the area is 2 cm². 2 The mass of La contained in the electrode sample was calculated. Then, by dividing the mass of La by the atomic weight of La (138.9), the area of ​​2 cm² was calculated. 2 The number of moles (mmols) of La contained in the electrode sample was calculated. This number of moles of La was then used to determine the electrode area of ​​2 cm². 2 By dividing by this, the 1 cm of the electrode after 500 hours of energization is obtained. 2 Number of moles of La per unit (mmol / cm³) 2 ) was calculated. The evaluation results for the examples and comparative examples are shown in Tables 3, 5, 7, and 8.

[0110] (Method for calculating the capacitance per 1 mmol of La in an electrode after 500 hours of current application) The double-layer capacitance (F / cm²) of the electrode after 500 hours of energization. 2 ) is the number of moles of La per unit area (mmol / cm³). 2 By dividing by (), the capacitance per 1 mmol of La of the electrode after 500 hours of energization (F / mmol) can be calculated. La ) was calculated. The evaluation results for the examples and comparative examples are shown in Tables 3, 5, 7, and 8.

[0111] (Combustion by-product gas / LaNi x M y O 3-z (Method for calculating molar ratios) The reaction equation for calcining a mixture of anhydrous raw materials La, Ni, and M, hydrogen peroxide, and a compound having carboxyl groups and amino groups and composed of C, H, N, and O was created by adding up the reaction equations of each raw material, taking into account the ratio of preparation. x M y O 3-z The total number of moles of CO2, H2O, and N2 produced as by-products when 1 mole of is generated is calculated as the combustion by-product gas / LaNi x M y O 3-z It was calculated as a molar ratio. La May x O 3-z After preparing by combustion, raw material M is added separately to form LaNi x M y O 3-z When preparing this, the CO2, H2O, and N2 produced as by-products by the combustion of raw material M are considered combustion by-product gases / LaNi x M y O 3-z This is not considered when calculating the molar ratio. The reaction equations for each raw material are as follows: <La(NO3)3·6H2O> La(NO3)3→LaO 1.5 +1.5N2+3.75O2...(Formula 1) <Lanthanum acetate pentahydrate> (CH3COO)3La+6O2→LaO 1.5 +6CO2+4.5H2O...(Formula 2) <Ni(NO3) 2· 6H2O> Ni(NO3)2 → NiO 1.5 +N2+2.25O2...(Formula 3) <Niobium oxalate> NH4NbO(C2O4)2+1.75O2→0.5N2+4CO2+2H2O+NbO 2.5 ...(Formula 4) <Nb2O5ゾル> Nb2O5 → 2NbO 2.5 (No by-product gases are generated) ... (Equation 5) <Hydrogen peroxide> H2O2→H2O+0.5O2...(Formula 6) <Mn(NO3)2·6H2O> Mn(NO3)2→MnO 1.5 +N2+2.25O2...(Formula 7) <TiO2ゾル> TiO2 → TiO2 (no by-product gases produced) ... (Equation 8) <ZrO(NO3)2·2H2O> ZrO(NO3)2→ZrO2+N2+2.5O2...(Formula 9) <tacl5> TaCl5 + 1.25O2 → TaO 2.5 + 2.5Cl2 ··· (Equation 10) <Antimony tartrate> H(C4H2O6)Sb + 3O2 → 4CO2 + SbO 2.5 + 1.5H2O ··· (Equation 11) <Glycine> C2H5NO2 + 2.25O2 → 2CO2 + 2.5H2O + 0.5N2 ··· (Equation 12) <Aspartic acid> C4H7NO4 + 3.75O2 → 4CO2 + 3.5H2O + 0.5N2 ··· (Equation 13) For example, when La(NO3)3·6H2O, Ni(NO3) 2· 6H2O, ammonium niobium oxalate, and glycine are mixed and burned in a molar ratio of 1:0.8:0.2:1.38, the reaction equation is as follows: (Equation 1) + 0.8*(Equation 3) + 0.2*(Equation 4) + 1.38*(Equation 12), which is the following (Equation A), and the combustion by-product gas / LaNi x M y O 3-z The molar ratio becomes 3.09 + 3.85 + 3.56 = 10.5. La(NO3)3 + 0.8Ni(NO3)2 + 0.2{NH4NbO(C2O4)2 + 1.75O2} + 1.38(C2H5NO2 + 2.25O2) → (LaO 1.5 + 1.5N2 + 3.75O2) + 0.8(NiO 1.5 + N2 + 2.25O2) + 0.2(0.5N2 + 4CO2 + 2H2O + NbO 2.5 ) + 1.38(2CO2 + 2.5H2O + 0.5N2) → LaNi 0.8 Nb 0.2 O 3.2 + 3.09N2 + 5.55O2 + 3.85H2O + 3.56CO2 ··· (Equation A) The evaluation results in the examples and comparative examples are shown in Tables 3, 5, 7, and 8.

[0112] (Example A11) An electrolytic cell for alkaline water electrolysis and a bipolar electrolytic cell were fabricated as follows. - Anode - Fabricated in the same manner as in Example A5. -cathode- As the conductive substrate, a plain weave mesh substrate was used, on which platinum was supported, and which consisted of 0.15 mm diameter nickel wires woven together at 40 mesh. -Partition wall, outer frame- A bipolar element was used, comprising a partition wall separating the anode and cathode, and an outer frame surrounding the partition wall. The materials of the partition wall and other components of the bipolar element that come into contact with the electrolyte were all made of nickel. -Conductive elastic material- The conductive elastic material used was made by weaving nickel wire with a diameter of 0.15 mm and then corrugating it to a wave height of 5 mm. -diaphragm- A coating solution with the following component composition was obtained using zirconium oxide (trade name "EP Zirconium Oxide," manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.), N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.), polysulfone ("Udel" (registered trademark), manufactured by Solvay Advanced Polymers, Inc.), and polyvinylpyrrolidone (weight-average molecular weight (Mw) 900,000, manufactured by Wako Pure Chemical Industries, Ltd.). Polysulfone: 15 parts by mass Polyvinylpyrrolidone: 6 parts by mass N-methyl-2-pyrrolidone: 70 parts by mass Zirconium oxide: 45 parts by mass The above coating solution was applied to both surfaces of a polyphenylene sulfide mesh substrate (manufactured by Kureba Co., Ltd., film thickness 280 μm, mesh opening 358 μm, fiber diameter 150 μm). Immediately after coating, the substrate coated with the solution was exposed to steam, and then immersed in a solidification bath to form a coating film on the substrate surface. After that, the coating film was thoroughly washed with pure water to obtain a porous film. -gasket- The gasket used was a rectangular shape with a thickness of 4.0 mm, a width of 18 mm, and an inner dimension of 504 mm square. It had an opening on the inside that was the same size as the electrode chamber when viewed from above, and a slit structure for holding the diaphragm in place. -Zero-gap type bipolar element- The external header type zero-gap cell unit 60 is rectangular with dimensions of 540 mm x 620 mm, and the area of ​​the current-carrying surfaces of the anode 2a and cathode 2c is 500 mm x 500 mm. On the cathode side of the zero-gap bipolar element 60, the cathode 2c, conductive elastic body 2e, and cathode current collector 2r are stacked and connected to the partition wall 1 via cathode ribs 6, and there is a cathode chamber 5c through which the electrolyte flows. On the anode side, the anode 2a is connected to the partition wall 1 via anode ribs 6, and there is an anode chamber 5a through which the electrolyte flows (Figure 2). The depth of the anode chamber 5a (anode chamber depth, distance between the partition wall and the anode in Figure 2) was 25 mm, and the depth of the cathode chamber 5c (cathode chamber depth, distance between the partition wall and the cathode current collector in Figure 2) was also 25 mm. The material was nickel. The nickel partition wall 1, to which the nickel anode rib 6 (25 mm high, 1.5 mm thick) and nickel cathode rib 6 (25 mm high, 1.5 mm thick) were attached by welding, had a thickness of 2 mm. A nickel-expanded substrate that had been pre-blast-treated was used as the cathode current collector 2r. The substrate had a thickness of 1 mm and an aperture ratio of 54%. A conductive elastic body 2e was spot-welded and fixed onto the cathode current collector 2r. By stacking these zero-gap type bipolar elements via a gasket holding the diaphragm, a zero-gap structure Z can be formed in which the anode 2a and cathode 2c are pressed against the diaphragm 4.

[0113] Using the electrolytic apparatus of Example A11 described above, with an electrolyte temperature of 80°C and a current density of 6 kA / m², 2 The system was continuously energized for 500 hours to perform water electrolysis. The voltage relative to each cell in Example A11 was monitored, and the trend of the voltage relative to each cell was recorded. The cell voltage of each cell was compared by taking the average value of the three cells in Example A11. In Example A11, the average overvoltage of the three cells was a low 1.73V after 500 hours of energization. Therefore, it can be concluded that the anode of Example A5 was able to achieve a low cell voltage even during long-term operation.

[0114] (Example B16) An electrolytic cell for alkaline water electrolysis, a bipolar electrolytic cell, was fabricated as follows. -anode- It was prepared using the same method as in Example B14. -cathode- As the conductive substrate, a plain weave mesh substrate was used, on which platinum was supported, and which consisted of 0.15 mm diameter nickel wires woven together at 40 mesh. -Partition wall, outer frame- A bipolar element was used, comprising a partition wall separating the anode and cathode, and an outer frame surrounding the partition wall. The materials of the partition wall and other components of the bipolar element that come into contact with the electrolyte were all made of nickel. -Conductive elastic material- The conductive elastic material used was made by weaving nickel wire with a diameter of 0.15 mm and then corrugating it to a wave height of 5 mm. -diaphragm- A coating solution with the following component composition was obtained using zirconium oxide (trade name "EP Zirconium Oxide," manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.), N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.), polysulfone ("Udel" (registered trademark), manufactured by Solvay Advanced Polymers, Inc.), and polyvinylpyrrolidone (weight-average molecular weight (Mw) 900,000, manufactured by Wako Pure Chemical Industries, Ltd.). Polysulfone: 15 parts by mass Polyvinylpyrrolidone: 6 parts by mass N-methyl-2-pyrrolidone: 70 parts by mass Zirconium oxide: 45 parts by mass The above coating solution was applied to both surfaces of a polyphenylene sulfide mesh substrate (manufactured by Kureba Co., Ltd., film thickness 280 μm, mesh opening 358 μm, fiber diameter 150 μm). Immediately after coating, the substrate coated with the solution was exposed to steam, and then immersed in a solidification bath to form a coating film on the substrate surface. After that, the coating film was thoroughly washed with pure water to obtain a porous film. -gasket- The gasket used was a rectangular shape with a thickness of 4.0 mm, a width of 18 mm, and an inner dimension of 504 mm square. It had an opening on the inside that was the same size as the electrode chamber when viewed from above, and a slit structure for holding the diaphragm in place. -Zero-gap type bipolar element- The external header type zero-gap cell unit 60 is rectangular with dimensions of 540 mm x 620 mm, and the area of ​​the current-carrying surfaces of the anode 2a and cathode 2c is 500 mm x 500 mm. On the cathode side of the zero-gap bipolar element 60, the cathode 2c, conductive elastic body 2e, and cathode current collector 2r are stacked and connected to the partition wall 1 via cathode ribs 6, and there is a cathode chamber 5c through which the electrolyte flows. On the anode side, the anode 2a is connected to the partition wall 1 via anode ribs 6, and there is an anode chamber 5a through which the electrolyte flows (Figure 2). The depth of the anode chamber 5a (anode chamber depth, distance between the partition wall and the anode in Figure 2) was 25 mm, and the depth of the cathode chamber 5c (cathode chamber depth, distance between the partition wall and the cathode current collector in Figure 2) was also 25 mm. The material was nickel. The nickel partition wall 1, to which the nickel anode rib 6 (25 mm high, 1.5 mm thick) and nickel cathode rib 6 (25 mm high, 1.5 mm thick) were attached by welding, had a thickness of 2 mm. As the cathode current collector 2r, a nickel expanded substrate that had been pre-blast-treated was used as the current collector. The substrate had a thickness of 1 mm and an aperture ratio of 54%. A conductive elastic body 2e was spot-welded and fixed onto the cathode current collector 2r. By stacking these zero-gap type bipolar elements via a gasket holding the diaphragm, a zero-gap structure Z can be formed in which the anode 2a and cathode 2c are pressed against the diaphragm 4.

[0115] Using the electrolytic apparatus of Example B16 described above, with an electrolyte temperature of 80°C and a current density of 6 kA / m², 2 The system was continuously energized for 500 hours to perform water electrolysis. The voltage relative to each cell in Example B16 was monitored, and the trend of the voltage relative to each cell was recorded. The cell voltage of each cell was compared by taking the average value of the three cells in Example B16. In Example B16, the average overvoltage of the three cells was a low 1.77V after 500 hours of energization. Therefore, it can be concluded that the anode of Example B14 was able to achieve a low cell voltage even during long-term operation.

[0116] (Example C12) An electrolytic cell for alkaline water electrolysis, a bipolar electrolytic cell, was fabricated as follows. -anode- It was prepared using the same method as in Example C4. -cathode- As the conductive substrate, a plain weave mesh substrate was used, on which platinum was supported, and which consisted of 0.15 mm diameter nickel wires woven together at 40 mesh. -Partition wall, outer frame- A bipolar element was used, comprising a partition wall separating the anode and cathode, and an outer frame surrounding the partition wall. The materials of the partition wall and other components of the bipolar element that come into contact with the electrolyte were all made of nickel. -Conductive elastic material- The conductive elastic material used was made by weaving nickel wire with a diameter of 0.15 mm and then corrugating it to a wave height of 5 mm. -diaphragm- A coating solution with the following component composition was obtained using zirconium oxide (trade name "EP Zirconium Oxide," manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.), N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.), polysulfone ("Udel" (registered trademark), manufactured by Solvay Advanced Polymers, Inc.), and polyvinylpyrrolidone (weight-average molecular weight (Mw) 900,000, manufactured by Wako Pure Chemical Industries, Ltd.). Polysulfone: 15 parts by mass Polyvinylpyrrolidone: 6 parts by mass N-methyl-2-pyrrolidone: 70 parts by mass Zirconium oxide: 45 parts by mass The above coating solution was applied to both surfaces of a polyphenylene sulfide mesh substrate (manufactured by Kureba Co., Ltd., film thickness 280 μm, mesh opening 358 μm, fiber diameter 150 μm). Immediately after coating, the substrate coated with the solution was exposed to steam, and then immersed in a solidification bath to form a coating film on the substrate surface. After that, the coating film was thoroughly washed with pure water to obtain a porous film. -gasket- The gasket used was a rectangular shape with a thickness of 4.0 mm, a width of 18 mm, and an inner dimension of 504 mm square. It had an opening on the inside that was the same size as the electrode chamber when viewed from above, and a slit structure for holding the diaphragm in place. -Zero-gap type bipolar element- The external header type zero-gap cell unit 60 is rectangular with dimensions of 540 mm x 620 mm, and the area of ​​the current-carrying surfaces of the anode 2a and cathode 2c is 500 mm x 500 mm. On the cathode side of the zero-gap bipolar element 60, the cathode 2c, conductive elastic body 2e, and cathode current collector 2r are stacked and connected to the partition wall 1 via cathode ribs 6, and there is a cathode chamber 5c through which the electrolyte flows. On the anode side, the anode 2a is connected to the partition wall 1 via anode ribs 6, and there is an anode chamber 5a through which the electrolyte flows (Figure 2). The depth of the anode chamber 5a (anode chamber depth, distance between the partition wall and the anode in Figure 2) was 25 mm, and the depth of the cathode chamber 5c (cathode chamber depth, distance between the partition wall and the cathode current collector in Figure 2) was also 25 mm. The material was nickel. The nickel partition wall 1, to which the nickel anode rib 6 (25 mm high, 1.5 mm thick) and nickel cathode rib 6 (25 mm high, 1.5 mm thick) were attached by welding, had a thickness of 2 mm. A nickel-expanded substrate that had been pre-blast-treated was used as the cathode current collector 2r. The substrate had a thickness of 1 mm and an aperture ratio of 54%. A conductive elastic body 2e was spot-welded and fixed onto the cathode current collector 2r. By stacking these zero-gap type bipolar elements via a gasket holding the diaphragm, a zero-gap structure Z can be formed in which the anode 2a and cathode 2c are pressed against the diaphragm 4.

[0117] Using the electrolytic apparatus of Example C12 described above, with an electrolyte temperature of 80°C and a current density of 6 kA / m², 2 The system was continuously energized for 500 hours to perform water electrolysis. The voltage relative to each cell in Example C12 was monitored, and the trend of the voltage relative to each cell was recorded. The cell voltage of each cell was compared by taking the average value of the three cells in Example C12. In Example C12, the average overvoltage across the three cells was a low 1.73V after 500 hours of energization. Therefore, it can be concluded that the anode in Example C4 achieved a low cell voltage even during long-term operation.

[0118] (Example D13) An electrolytic cell for alkaline water electrolysis, a bipolar electrolytic cell, was fabricated as follows. -anode- It was prepared using the same method as in Example D10. -cathode- As the conductive substrate, a plain weave mesh substrate was used, on which platinum was supported, and which consisted of 0.15 mm diameter nickel wires woven together at 40 mesh. -Partition wall, outer frame- A bipolar element was used, comprising a partition wall separating the anode and cathode, and an outer frame surrounding the partition wall. The materials of the partition wall and other components of the bipolar element that come into contact with the electrolyte were all made of nickel. -Conductive elastic material- The conductive elastic material used was made by weaving nickel wire with a diameter of 0.15 mm and then corrugating it to a wave height of 5 mm. -diaphragm- A coating solution with the following component composition was obtained using zirconium oxide (trade name "EP Zirconium Oxide," manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.), N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.), polysulfone ("Udel" (registered trademark), manufactured by Solvay Advanced Polymers, Inc.), and polyvinylpyrrolidone (weight-average molecular weight (Mw) 900,000, manufactured by Wako Pure Chemical Industries, Ltd.). Polysulfone: 15 parts by mass Polyvinylpyrrolidone: 6 parts by mass N-methyl-2-pyrrolidone: 70 parts by mass Zirconium oxide: 45 parts by mass The above coating solution was applied to both surfaces of a polyphenylene sulfide mesh substrate (manufactured by Kureba Co., Ltd., film thickness 280 μm, mesh opening 358 μm, fiber diameter 150 μm). Immediately after coating, the substrate coated with the solution was exposed to steam, and then immersed in a solidification bath to form a coating film on the substrate surface. After that, the coating film was thoroughly washed with pure water to obtain a porous film. -gasket- The gasket used was a rectangular shape with a thickness of 4.0 mm, a width of 18 mm, and an inner dimension of 504 mm square. It had an opening on the inside that was the same size as the electrode chamber when viewed from above, and a slit structure for holding the diaphragm in place. -Zero-gap type bipolar element- The external header type zero-gap cell unit 60 is rectangular with dimensions of 540 mm x 620 mm, and the area of ​​the current-carrying surfaces of the anode 2a and cathode 2c is 500 mm x 500 mm. On the cathode side of the zero-gap bipolar element 60, the cathode 2c, conductive elastic body 2e, and cathode current collector 2r are stacked and connected to the partition wall 1 via cathode ribs 6, and there is a cathode chamber 5c through which the electrolyte flows. On the anode side, the anode 2a is connected to the partition wall 1 via anode ribs 6, and there is an anode chamber 5a through which the electrolyte flows (Figure 2). The depth of the anode chamber 5a (anode chamber depth, distance between the partition wall and the anode in Figure 2) was 25 mm, and the depth of the cathode chamber 5c (cathode chamber depth, distance between the partition wall and the cathode current collector in Figure 2) was also 25 mm. The material was nickel. The nickel partition wall 1, to which the nickel anode rib 6 (25 mm high, 1.5 mm thick) and nickel cathode rib 6 (25 mm high, 1.5 mm thick) were attached by welding, had a thickness of 2 mm. A nickel-expanded substrate that had been pre-blast-treated was used as the cathode current collector 2r. The substrate had a thickness of 1 mm and an aperture ratio of 54%. A conductive elastic body 2e was spot-welded and fixed onto the cathode current collector 2r. By stacking these zero-gap type bipolar elements via a gasket holding the diaphragm, a zero-gap structure Z can be formed in which the anode 2a and cathode 2c are pressed against the diaphragm 4.

[0119] Using the electrolytic apparatus of Example D13 described above, with an electrolyte temperature of 80°C and a current density of 6 kA / m², 2 The system was continuously energized for 500 hours to perform water electrolysis. The voltage relative to each cell in Example D13 was monitored, and the trend of the voltage relative to each cell was recorded. The cell voltage of each cell was compared by taking the average value of the three cells in Example D13. In Example D13, the average overvoltage of the three cells was a low 1.71V after 500 hours of energization. Therefore, it can be concluded that the anode of Example D10 was able to achieve a low cell voltage even during long-term operation.

[0120] [Table 1]

[0121] [Table 2]

[0122] [Table 3]

[0123] [Table 4]

[0124] [Table 5]

[0125] [Table 6]

[0126] [Table 7]

[0127] [Table 8] [Industrial applicability]

[0128] Because the electrode of the present invention has a large initial double-layer capacitance, it exhibits low oxygen overpotential after prolonged energization, making it suitable for use as the anode in a water electrolysis cell during the electrolysis of alkali-containing water. [Explanation of Symbols]

[0129] 1 Bulkhead 2 electrodes 2a anode 2c cathode 2e Conductive elastic material 2r cathode current collector 3 Outer frame 4 Diaphragm 5a Anode chamber 5c cathode chamber 6 Ribs 7 Gasket 50 bipolar electrolyzer 51g Fast head, loose head 51i Insulating board 51a Anode terminal element 51c Cathode Terminal Element 51r tie rod 60 Bipolar Elements 65 electrolytic cells 70 Electrolyzer 71. Liquid transfer pump 72 Gas-liquid separation tank 74 Rectifier 75. Oxygen concentration meter 76 Hydrogen concentration meter 77 Flow meter 78 Pressure gauge 79 Heat exchanger 80 Pressure control valve Z-zero gap structure

Claims

1. A base material and LaNi formed on the base material ｘ M ｙ O ３－ｚ The device has layers (x+y is 0.8 to 1.2, y is 0.001 to 0.6, z is -0.5 to 0.5, and M contains at least one of Nb, Ta, Sb, Ti, Mn, or Zr), and the initial bilayer capacitance is 0.6 F / cm². ２ An electrode characterized by having a molecular weight such that the number of moles of La per 1 cm² is 0.06 mmol or more and 1.1 mmol or less.

2. The electrode according to claim 1, wherein the capacitance per 1 mmol of La is 10F or more and 25F or less.

3. The above LaNi ｘ M ｙ O ３－ｚ The adhesion amount of the layer is 145 g / m ２ over 3500 g / m ２ The electrode according to claim 1 or 2, which is as follows.

4. An electrolytic cell characterized by using the electrode described in claim 1 or 2 as the anode.

5. A method for producing hydrogen, characterized by inputting a fluctuating power supply to the electrolytic cell described in claim 4.

6. In a hydrogen production method for producing hydrogen by electrolyzing water containing alkali in an electrolytic cell, the electrolytic cell comprises at least an anode and a cathode, and the anode comprises a substrate and LaNi formed on the substrate. ｘ M ｙ O ３－ｚ The device has layers (x+y is 0.8 to 1.2, y is 0.001 to 0.6, z is -0.5 to 0.5, and M contains at least one of Nb, Ta, Sb, Ti, Mn, or Zr), and the initial bilayer capacitance is 0.6 F / cm². ２ A method for producing hydrogen, characterized in that the amount of La per 1 cm² is greater than or equal to 0.06 mmol or more and 1.1 mmol or less.

7. La (NO ３ ) ３ Ni (NO ３ ) ２ The process includes a step of calcining a mixture of compounds having carboxyl groups and amino groups and composed of C, H, N, and O as constituent elements, wherein the combustion by-product gas (CO) generated during the calcination is produced. ２ , H ２ O, and N ２ ) the LaNi ｘ M ｙ O ３－ｚ Molar ratio of LaNi x My O 3-z to (combustion by-product gas / LaNi ｘ M ｙ O ３－ｚ A method for preparing an electrode according to claim 1 or 2, characterized in that the value of ) is 5 or more and less than 12.

6.

8. La (NO ３ ) ３ Ni (NO ３ ) ２ The process includes a step of calcining a mixture of glycine and NO ３ － A method for preparing an electrode according to claim 1 or 2, characterized in that the molar ratio is 0.1 or more and 0.3 or less.

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