Electrode for electrolysis and its manufacturing method

Abstract

Provided is a method for producing an electrolysis electrode that is provided with a catalyst that has excellent catalytic activity such as having a low oxygen overvoltage and that has excellent stability such as having less loss of a catalyst component such as iridium (Ir). This method is for producing an electrolysis electrode, and comprises a step for applying, on the surface of an electrically conductive substrate, a catalyst precursor composition containing an iridium component or the like, a step for obtaining a primary fired body by heating the electrically conductive substrate on which the catalyst precursor composition is applied, and a step for forming, on the surface of the electrically conductive substrate, a catalyst layer containing iridium oxide by heating the primary fired body. The iridium component is an iridium compound including a carboxy group. In the catalyst precursor composition, the nickel (Ni) content is 10-35 mass%, the cobalt (Co) content is 25-55 mass%, and the iridium (Ir) content is 15-55 mass% (provided that Ni+Co+Ir=100 mass% is satisfied).

Description

[Technical field]

[0001] The present invention relates to an electrode for electrolysis and a method for producing an electrode for electrolysis. [Background technology]

[0002] Hydrogen is suitable for storage and transportation, and is a secondary energy with a small environmental impact, so hydrogen energy systems that use hydrogen as an energy carrier are attracting attention. Currently, hydrogen is mainly produced by steam reforming of fossil fuels, but from the perspective of global warming and the problems of fossil fuel depletion, alkaline water electrolysis using renewable energy as a power source is becoming increasingly important.

[0003] Water electrolysis can be broadly divided into two types. One is alkaline water electrolysis, in which a highly concentrated alkaline aqueous solution is used as the electrolyte. The other is solid polymer water electrolysis, in which a solid polymer membrane (SPE) is used as the electrolyte. When performing large-scale hydrogen production by water electrolysis, it is said that alkaline water electrolysis, which uses inexpensive materials such as nickel and other iron-based metals, is more suitable than solid polymer water electrolysis, which uses electrodes that use large amounts of expensive precious metals.

[0004] High-concentration alkaline aqueous solutions become more conductive as the temperature rises, but they also become more corrosive. For this reason, the upper limit of the operating temperature is limited to around 80 to 90°C. Through the development of materials for the electrolytic cell and various piping materials that can withstand high temperatures and high-concentration alkaline aqueous solutions, as well as the development of low-resistance diaphragms and electrodes with enlarged surface areas and catalysts, the electrolysis performance has improved to a current density of 0.3 to 0.4 Acm. -2 The output voltage has improved to about 1.7 to 1.9 V (efficiency 78 to 87%).

[0005] Nickel-based materials that are stable in highly concentrated alkaline aqueous solutions are used as anodes for alkaline water electrolysis, and it is known that nickel-based anodes have a lifespan of several decades or more in alkaline water electrolysis using a stable power source. However, when renewable energy is used as the power source, harsh conditions such as frequent start-stops and load fluctuations are often encountered, and the performance degradation of nickel-based anodes becomes an issue.

[0006] Conventionally, platinum group metals, platinum group metal oxides, valve metal oxides, iron group oxides, lanthanide group metal oxides, etc. have been used as catalysts (anode catalysts) for oxygen generation anodes used in alkaline water electrolysis. Other known anode catalysts include nickel-based alloys such as Ni-Co and Ni-Fe, nickel with expanded surface area, conductive oxides (ceramic materials) such as spinel-based Co3O4, NiCo2O4, and perovskite-based LaCoO3, LaNiO3, etc., precious metal oxides, and oxides made of lanthanide group metals and precious metals.

[0007] As an oxygen generating anode used in alkaline water electrolysis, for example, an anode for alkaline water electrolysis has been proposed in which a catalytic layer containing nickel-cobalt oxide and iridium oxide or ruthenium oxide is formed on the surface of a nickel substrate (Patent Document 1). Also, an anode for alkaline water electrolysis has been proposed in which a catalytic layer made of lithium-containing nickel oxide is formed on the surface of a nickel substrate (Patent Document 2). Furthermore, an electrode for electrolysis has been proposed in which a catalytic layer containing a catalyst such as nickel-cobalt spinel oxide or iridium oxide is formed on the surface of a nickel substrate via an intermediate layer (Patent Document 3). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2017-190476 A [Patent Document 2] International Publication No. 2018 / 047961 [Patent Document 3] International Publication No. 2019 / 172160 Summary of the Invention [Problem to be solved by the invention]

[0009] However, even the anodes for alkaline water electrolysis proposed in Patent Documents 1 to 3 do not have sufficiently low oxygen overvoltage, and further improvement in catalytic activity is required. In addition, the catalytic components tend to be lost due to detachment or the like with use, and the catalytic activity cannot be said to be stably exhibited over a long period of time, leaving room for further improvement.

[0010] The present invention has been made in consideration of the problems associated with such conventional techniques, and an object of the present invention is to provide an electrode for electrolysis provided with a catalyst having excellent catalytic activity, such as a low oxygen overvoltage, and excellent stability, such as reduced loss of catalytic components, such as iridium (Ir), and a method for producing the same. [Means for solving the problem]

[0011] That is, according to the present invention, there is provided a method for producing an electrode for electrolysis as described below. [1] A method for producing an electrode for electrolysis, comprising the steps of: directly or indirectly applying a catalyst precursor composition containing a nickel component, a cobalt component, and an iridium component to a surface of a conductive substrate, at least the surface of which is made of nickel or a nickel-based alloy; heat-treating the conductive substrate to which the catalyst precursor composition has been applied at 320 to 600°C to obtain a primary fired product; and heat-treating the primary fired product at 350 to 600°C to directly or indirectly form a catalyst layer containing a nickel-cobalt spinel oxide and an iridium oxide on the surface of the conductive substrate, wherein the iridium component is an iridium compound containing a carboxy group, and the catalyst precursor composition has a nickel (Ni) content of 10 to 35 mass%, a cobalt (Co) content of 25 to 55 mass%, and an iridium (Ir) content of 15 to 55 mass% (wherein Ni+Co+Ir=100 mass%). [2] The method for producing an electrode for electrolysis according to [1], wherein in the catalyst precursor composition, a mass ratio ((Ni+Co) / Ir) of the total content of nickel (Ni) and cobalt (Co) to the content of iridium (Ir) is 0.9 to 4.1. [3] The method for producing an electrode for electrolysis according to [1] or [2] above, wherein the iridium compound is at least one of an iridium hydroxyacetochloride complex and iridium acetate. [4] The method for producing an electrode for electrolysis according to any one of [1] to [3] above, further comprising a step of treating the primary fired product by contacting it with an alkaline component.

[0012] Furthermore, according to the present invention, there is provided the following electrode for electrolysis. [5] An electrode for electrolysis produced by the production method according to any one of [1] to [4] above. [6] The electrode for electrolysis according to [5] above, which is an electrode for alkaline water electrolysis. Effect of the Invention

[0013] Effects of the Invention According to the present invention, it is possible to provide an electrode for electrolysis comprising a catalyst having excellent catalytic activity, such as a low oxygen overvoltage, and excellent stability, such as reduced loss of catalytic components, such as iridium (Ir), and a method for producing the same. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a schematic diagram of one embodiment of an electrode for electrolysis according to the present invention. [Diagram 2] 1 is an SEM image of a cross section of the electrode for electrolysis produced in Example 3. [Diagram 3] 1 is an SEM image of a cross section of the electrode for electrolysis produced in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Electrode for electrolysis> Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited to the following embodiment. Fig. 1 is a cross-sectional view showing a schematic diagram of one embodiment of an electrode for electrolysis of the present invention. As shown in Fig. 1, an electrode for electrolysis 10 of this embodiment includes a conductive substrate 2 and a catalyst layer 6 formed on the surface of the conductive substrate 2. Hereinafter, the electrode for electrolysis of the present invention will be described in detail.

[0016] (Conductive substrate) The conductive substrate 2 is a conductor for conducting electricity for electrolysis, and is a member having a function as a carrier for supporting the catalytic layer 6. At least the surface of the conductive substrate 2 (the surface on which the catalytic layer 6 is formed) is made of nickel or a nickel-based alloy. That is, the conductive substrate 2 may be entirely made of nickel or a nickel-based alloy, or only the surface may be made of nickel or a nickel-based alloy. Specifically, the conductive substrate 2 may be a metal material such as iron, stainless steel, aluminum, or titanium, on whose surface a coating of nickel or a nickel-based alloy is formed by plating or the like.

[0017] The thickness of the conductive substrate is preferably 0.05 to 5 mm. The conductive substrate is preferably shaped to have openings for removing bubbles of oxygen, hydrogen, etc. that are generated. For example, an expanded mesh or a porous expanded mesh can be used as the conductive substrate. When the conductive substrate is shaped to have openings, the opening ratio of the conductive substrate is preferably 10 to 95%.

[0018] (catalyst layer) The catalytic layer 6 is a layer having catalytic activity formed on the surface of the conductive substrate 2. As shown in FIG. 1, the catalytic layer 6 may be formed on the surface of the conductive substrate 2 via a nickel oxide layer 4 in order to protect the conductive substrate 2. The catalytic layer 6 contains nickel-cobalt spinel oxide (NiCo2O4) and iridium oxide. Therefore, the electrolysis electrode 10 of this embodiment is useful as an electrode for alkaline water electrolysis, and is particularly suitable as an anode for alkaline water electrolysis. The thickness, density, etc. of the catalytic layer are not particularly limited and can be set appropriately depending on the application of the electrode, etc.

[0019] The types and content ratios of the metal elements in the catalyst layer 6 are substantially the same as the types and content ratios of the metal elements in the catalyst precursor composition used in the manufacturing method of the electrode for electrolysis described below. Therefore, the content of nickel (Ni) in the catalyst layer is preferably 10 to 35 mass%, the content of cobalt (Co) is preferably 25 to 55 mass%, and the content of iridium (Ir) is preferably 15 to 55 mass%, where Ni+Co+Ir=100 mass%. By setting the types and content ratios of the metal elements in the catalyst layer as described above, the oxygen overvoltage is lowered and the loss of catalyst components such as iridium (Ir) can be further reduced.

[0020] The electrode for electrolysis of this embodiment is manufactured by a specific manufacturing method described below. By manufacturing by the specific manufacturing method, it is presumed that the state and composition (e.g., crystal state, crystal structure, type, composition, and content of trace components) of the formed catalyst layer will be different from electrodes for electrolysis manufactured by methods other than the specific manufacturing method. However, it is extremely difficult or practically impossible to analyze and confirm the state and composition of such a catalyst layer.

[0021] <Method of manufacturing electrodes for electrolysis> One embodiment of the method for producing an electrode for electrolysis of the present invention includes a step of directly or indirectly applying a catalyst precursor composition containing a nickel component, a cobalt component, and an iridium component to the surface of a conductive substrate (hereinafter also referred to as the "application step"); a step of heat-treating the conductive substrate to which the catalyst precursor composition has been applied at 320 to 600°C to obtain a primary fired product (hereinafter also referred to as the "heat treatment step"); and a step of heat-treating the primary fired product at 350 to 600°C to directly or indirectly form a catalyst layer containing nickel-cobalt spinel oxide and iridium oxide on the surface of the conductive substrate (hereinafter also referred to as the "post-baking step"). The iridium component in the catalyst precursor composition is an iridium compound containing a carboxyl group. In the catalyst precursor composition, the content of nickel (Ni) is 10 to 35 mass%, the content of cobalt (Co) is 25 to 55 mass%, and the content of iridium (Ir) is 15 to 55 mass% (wherein Ni+Co+Ir=100 mass%). Hereinafter, the details of the method for producing an electrode for electrolysis of the present invention will be described.

[0022] (Pretreatment process) It is preferable to perform a chemical etching process on the conductive substrate in advance to remove contaminant particles such as metals and organic matter from the surface before the coating process. The amount of wear of the conductive substrate due to the chemical etching process is 30 g / m 2 More than 400g / m 2 It is preferable that the surface of the conductive substrate is roughened in advance in order to increase the adhesion to the intermediate layer. Examples of the roughening treatment include blasting treatment by spraying powder, etching treatment using an acid that is soluble in the substrate, and plasma spraying.

[0023] As shown in FIG. 1, a nickel oxide layer 4 may be formed on the surface of the conductive substrate 2 in order to protect the conductive substrate 2. The nickel oxide layer 4 may be formed, for example, by baking the conductive substrate 2 in air at 450 to 550° C. for 5 to 60 minutes. Alternatively, an intermediate layer may be formed on the conductive substrate by applying a solution obtained by dissolving nickel carboxylate in a solvent such as water to the surface of the conductive substrate and then heat-treating the solution at a temperature of 450° C. or higher and 600° C. or lower. When an intermediate layer is formed on the conductive substrate, the catalyst layer is formed on the conductive substrate via the intermediate layer.

[0024] (coating process) In the coating step, a catalyst precursor composition containing a nickel component, a cobalt component, and an iridium component is coated directly on the surface of a conductive substrate, or indirectly through another layer such as the intermediate layer. An iridium compound containing a carboxyl group is used as the iridium component. By using a catalyst precursor composition containing an iridium compound containing a carboxyl group as the iridium component and adopting a so-called thermal decomposition method, the oxygen overvoltage is lower, the loss of catalyst components such as iridium (Ir) is reduced, and a catalyst layer with excellent stability can be formed directly on the conductive substrate, or indirectly through another layer such as an intermediate layer, compared to the case where a catalyst precursor composition containing other iridium compounds such as iridium nitrate is used as the iridium component.

[0025] Examples of iridium compounds containing a carboxy group (hereinafter, simply referred to as "iridium compounds") include iridium hydroxyacetochloride complexes (IrHAC), iridium acetate (Ir-acetate), etc. Among these, it is preferable to use at least one of iridium hydroxyacetochloride complexes and iridium acetate as the iridium compound.

[0026] As the nickel component and the cobalt component, inorganic acid salts and organic acid salts capable of generating nickel ions and cobalt ions can be used. Among them, it is preferable to use nickel nitrate as the nickel component, and it is preferable to use cobalt nitrate as the cobalt component.

[0027] The catalyst precursor composition is, for example, an aqueous solution containing a nickel component, a cobalt component, and an iridium component. In the catalyst precursor composition, the content of nickel (Ni) is 10 to 35 mass%, preferably 15 to 30 mass%. In addition, in the catalyst precursor composition, the content of cobalt (Co) is 25 to 55 mass%, preferably 30 to 55 mass%. In addition, in the catalyst precursor composition, the content of iridium (Ir) is 15 to 55 mass%, preferably 20 to 55 mass%, more preferably 23 to 52 mass%. Note that Ni + Co + Ir = 100 mass%. By using a catalyst precursor composition in which the contents of nickel (Ni), cobalt (Co), and iridium (Ir) are within the above ranges, the oxygen overvoltage is lower, the loss of catalyst components such as iridium (Ir) is reduced, and a catalyst layer with excellent stability can be formed.

[0028] In the catalyst precursor composition, the mass ratio ((Ni+Co) / Ir) of the total content of nickel (Ni) and cobalt (Co) to the content of iridium (Ir) is preferably 0.9 to 4.1, more preferably 0.9 to 3.5, and particularly preferably 1.0 to 2.8. By using a catalyst precursor composition having a "(Ni+Co) / Ir" ratio value within the above range, it is possible to form a catalyst layer with lower oxygen overvoltage, reduced loss of catalyst components such as iridium (Ir), and further excellent stability.

[0029] The catalyst precursor composition can be applied to the surface of the conductive substrate by a known method such as brush coating, roller coating, spin coating, electrostatic coating, etc. Then, if necessary, the conductive substrate coated with the catalyst precursor composition is dried. The drying temperature is preferably set to a temperature (for example, about 60 to 80° C.) that avoids rapid evaporation of the solvent.

[0030] (Heat treatment process) In the heat treatment step, the conductive substrate coated with the catalyst precursor composition is heat treated (calcined) at 320 to 600°C, preferably 330 to 550°C, and more preferably 340 to 520°C. By setting the heat treatment temperature within the above range, the metal components (nickel component, cobalt component, and iridium component) in the catalyst precursor composition can be effectively thermally decomposed to obtain a primary calcined product. If the heat treatment temperature is too high, the oxidation of the conductive substrate is likely to proceed, and the electrode resistance may increase, leading to an increase in voltage loss. The heat treatment time may be appropriately set in consideration of the reaction rate, productivity, and the oxidation resistance of the surface of the catalyst layer to be formed.

[0031] The thickness of the catalyst layer formed can be controlled by appropriately setting the number of times the catalyst precursor composition is applied in the above-mentioned application step. The application and drying of the catalyst precursor composition may be repeated for each layer, and the whole may be heat-treated after the top layer is formed, or the application and heat-treatment of the catalyst precursor composition may be repeated for each layer, and the whole may be heat-treated after the top layer is formed.

[0032] (Alkaline treatment process) The method for producing an electrode for electrolysis according to the present embodiment preferably further includes a step of contacting the primary fired product obtained in the above-mentioned heat treatment step with an alkaline component to treat it (alkaline treatment step). By contacting the primary fired product with an alkaline component to treat it, it is possible to effectively remove impurities and the like generated by the heat treatment, and a catalyst layer having a lower oxygen overvoltage and excellent stability can be formed. In particular, when a catalyst precursor composition containing an iridium hydroxyacetochloride complex (IrHAC) as an iridium component is used, an acid component generated from IrHAC may remain in the primary fired product. For this reason, it is preferable to contact the primary fired product with an alkaline component to treat it, since the generated acid component can be effectively removed and a catalyst layer having a lower oxygen overvoltage and excellent stability can be formed.

[0033] A specific method for contacting the primary fired product with an alkaline component for treatment may include, for example, immersing the primary fired product in an aqueous solution of the alkaline component. As the alkaline component, an alkaline metal hydroxide such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) may be used. The concentration of the alkaline component in the aqueous solution of the alkaline component may be appropriately set within a range of, for example, 4 to 8 mass %. The temperature of the aqueous solution of the alkaline component may be appropriately set within a range of, for example, 20 to 40°C. The time for immersing the primary fired product in the aqueous solution of the alkaline component may be appropriately set within a range of, for example, 1 to 5 hours. After immersing the primary fired product in the aqueous solution of the alkaline component, it is preferable to wash the primary fired product with water and dry it.

[0034] (Post-bake process) In the post-baking step, the primary fired product is heat-treated at 350 to 600°C, preferably 380 to 580°C, and more preferably 400 to 560°C. After the primary fired product is allowed to cool, it is again heat-treated (post-baked) under a specified temperature condition to form a catalyst layer containing nickel-cobalt spinel oxide and iridium oxide on the surface of the conductive substrate, thereby obtaining the intended electrode for electrolysis. If this post-baking is not performed (the primary fired product is used as the electrode for electrolysis as it is), iridium is easily lost from the catalyst layer due to repeated electrolysis, and a catalyst layer with excellent stability cannot be formed.

[0035] <Electrolytic cell> The electrode for electrolysis of this embodiment can be used, for example, not only as an anode for electrolysis but also as a cathode for electrolysis. Furthermore, the electrode for electrolysis of this embodiment can be used as an anode for alkaline water electrolysis as well as a cathode for alkaline water electrolysis. That is, the electrode for electrolysis of this embodiment can be used to configure an electrolysis cell such as an alkaline water electrolysis cell. Hereinafter, constituent materials other than the anode when an alkaline water electrolysis cell is configured using the electrode for electrolysis of this embodiment as an anode for alkaline water electrolysis will be described.

[0036] As the cathode, it is preferable to select and use a substrate made of a material that can withstand alkaline water electrolysis and a catalyst with a small cathode overvoltage. As the cathode substrate, a nickel substrate or a nickel substrate coated with an active cathode can be used. The shape of the cathode substrate can be a plate, an expanded mesh, a porous expanded mesh, or the like.

[0037] Cathode materials include porous nickel with a large surface area, Ni-Mo-based materials, etc. Other examples include Raney nickel-based materials such as Ni-Al, Ni-Zn, and Ni-Co-Zn; sulfide-based materials such as Ni-S; and hydrogen storage alloy-based materials such as Ti2Ni. Catalysts that have low hydrogen overvoltage, high short-circuit stability, and high poisoning resistance are preferred. Other preferred catalysts include metals such as platinum, palladium, ruthenium, and iridium, and oxides of these metals.

[0038] Examples of the electrolytic diaphragm include asbestos, nonwoven fabrics, ion exchange membranes, polymeric porous membranes, and composite membranes of inorganic substances and organic polymers. Specifically, an ion-permeable diaphragm can be used in which an organic fiber cloth is embedded in a mixture of a hydrophilic inorganic material such as a calcium phosphate compound or calcium fluoride and an organic binding material such as polysulfone, polypropylene, or polyvinylidene fluoride. Also, an ion-permeable diaphragm can be used in which a stretched organic fiber cloth is embedded in a film-forming mixture of a granular inorganic hydrophilic material such as an oxide or hydroxide of antimony or zirconium and an organic binding agent such as a fluorocarbon polymer, polysulfone, polypropylene, polyvinyl chloride, or polyvinyl butyral.

[0039] By using an alkaline water electrolysis cell including the electrolysis electrode of this embodiment as a component, a high-concentration alkaline aqueous solution can be electrolyzed. The alkaline aqueous solution used as the electrolyte is preferably an aqueous solution of an alkali metal hydroxide such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). The concentration of the alkaline aqueous solution is preferably 1.5 to 40 mass%. In addition, the concentration of the alkaline aqueous solution is preferably 15 to 40 mass% because it has high electrical conductivity and can reduce power consumption. Furthermore, in consideration of cost, corrosiveness, viscosity, operability, etc., the concentration of the alkaline aqueous solution is preferably 20 to 30 mass%. EXAMPLES

[0040] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified.

[0041] <Production of anode substrate> A nickel expanded mesh was blasted with alumina particles, then immersed in 20% by mass hydrochloric acid and etched at near the boiling point for 3 minutes, and then baked at 500°C for 30 minutes to obtain an anode substrate with a nickel oxide (NiOx) layer formed on the surface.

[0042] <Manufacture of anodes for electrolysis> Example 1 Nickel nitrate (Ni(NO3)2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), and iridium hydroxyacetochloride complex (IrHAC) were dissolved in pure water to obtain a catalyst precursor composition (coating solution) with a mass ratio of nickel (Ni):cobalt (Co):iridium (Ir) of Ni:Co:Ir=27:53:20. The obtained coating solution was applied in a coating solution having a metal amount of 1.5 g / m2 per coating. 2The coating solution was applied to the surface of the nickel oxide layer of the anode substrate so that the anode substrate had a nickel-cobalt spinel oxide and iridium oxide-containing catalyst layer. The coating solution was then ... applied to the surface of the anode substrate so that the anode substrate had a nickel-cobalt spinel oxide and iridium oxide-containing catalyst layer. The coating solution was applied to the surface of the anode substrate so that the anode substrate had a nickel- 2 It was.

[0043] (Examples 2 to 5, Comparative Examples 1 to 5) An anode for alkaline water electrolysis (electrode for electrolysis) was obtained in the same manner as in Example 1 described above, except that the conditions were as shown in Table 1. In Comparative Examples 1 to 5, the primary fired product was used as the anode as it was. SEM images of the cross sections of the electrodes for electrolysis produced in Example 3 and Comparative Example 1 are shown in Figures 2 and 3.

[0044] TIFF0007621553000001.tif244170

[0045] <Evaluation> (Oxygen overvoltage measurement) A 30% potassium hydroxide solution was used, and the temperature was 80°C and the current density was 10 kA / m 2 The oxygen overvoltage (mV) of the electrolysis electrode thus produced was measured under the above conditions. The results are shown in Table 2.

[0046] (Measurement of remaining Ir in catalyst layer) Using a fluorescent X-ray analyzer, the fluorescent X-ray intensity of iridium (Ir) in the catalytic layer of the electrolysis electrode before and after the oxygen overvoltage measurement was measured. The remaining amount (%) of iridium (Ir) was calculated based on the amount of iridium (Ir) before the oxygen overvoltage measurement from the measured fluorescent X-ray intensity ratio. The results are shown in Table 2.

[0047] TIFF0007621553000002.tif94170

[0048] <Production and evaluation of electrolysis anodes having intermediate layers> Example 6 Nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O) was dissolved in pure water to obtain an aqueous solution with a nickel acetate concentration of 0.57 mol / L. A nickel expanded mesh was blasted with alumina particles, immersed in 20 mass% hydrochloric acid, and etched for 3 minutes near the boiling point to obtain an anode substrate. An aqueous solution of nickel acetate was applied to the surface of the obtained anode substrate with a brush, and then dried at 60°C for 10 minutes. Next, the substrate was heat-treated at 500°C for 10 minutes in an air atmosphere. The process from application of the aqueous solution of nickel acetate to heat treatment was repeated five times to obtain an anode substrate having an intermediate layer formed on its surface. An anode (electrode for electrolysis) for alkaline water electrolysis in which a catalyst layer was formed on the surface of the anode substrate via an intermediate layer was obtained in the same manner as in Example 3 described above, except that the above anode substrate having an intermediate layer formed on its surface was used.

[0049] The oxygen overvoltage of the obtained electrolysis electrode (current density: 10 kA / m 2 ) was 240 mV. In addition, the remaining amount of iridium (Ir) in the catalyst layer of the electrolysis electrode before and after the oxygen overvoltage measurement was 100%, and it was confirmed that, similarly to the electrolysis electrodes of Examples 1 to 5, iridium (Ir) was not substantially consumed. [Industrial Applicability]

[0050] The electrode for electrolysis of the present invention is suitable as an anode for alkaline water electrolysis, for example. [Explanation of symbols]

[0051] 2: Conductive substrate 4: Nickel oxide layer 6: Catalyst layer 10:Electrode for electrolysis

Claims

1. A step of directly or indirectly applying a catalyst precursor composition containing a nickel component, a cobalt component, and an iridium component to a surface of a conductive substrate, at least the surface of which is made of nickel or a nickel-based alloy; a step of heat-treating the conductive substrate coated with the catalyst precursor composition at 320 to 600° C. to obtain a primary fired product; and a step of heat-treating the primary fired product at 350 to 600° C. to directly or indirectly form a catalyst layer containing nickel-cobalt spinel oxide and iridium oxide on the surface of the conductive substrate, the iridium component is an iridium compound containing a carboxy group; The catalyst precursor composition has a nickel (Ni) content of 10 to 35 mass%, a cobalt (Co) content of 25 to 55 mass%, and an iridium (Ir) content of 15 to 55 mass% (wherein Ni + Co + Ir = 100 mass%).

2. The method for producing an electrode for electrolysis according to claim 1, wherein in the catalyst precursor composition, a mass ratio ((Ni+Co) / Ir) of a total content of nickel (Ni) and cobalt (Co) to a content of iridium (Ir) is 0.9 to 4.

1.

3. 3. The method for producing an electrode for electrolysis according to claim 1, wherein the iridium compound is at least one of an iridium hydroxyacetochloride complex and iridium acetate.

4. The method for producing an electrode for electrolysis according to claim 1 or 2, further comprising a step of treating the primary fired product by contacting it with an alkaline component.

5. An electrode for electrolysis produced by the method according to claim 1 or 2.

6. The electrode for electrolysis according to claim 5, which is an electrode for alkaline water electrolysis.

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