Electrolysis electrode and method for manufacturing same

Abstract

Provided is a method for manufacturing an electrolysis electrode having a catalyst with excellent catalytic activity such as low oxygen overvoltage and excellent stability such as reducing the loss of catalyst components such as iridium (Ir). A method for manufacturing an electrolysis electrode includes the following steps: a step of coating a surface of a conductive substrate with a catalyst precursor composition containing an iridium component, etc.; a step of heat-treating the conductive substrate coated with the catalyst precursor composition to obtain a first fired product; and a step of heat-treating the first fired product to form a catalyst layer containing iridium oxide on the surface of the conductive substrate, wherein the iridium component is an iridium compound containing a carboxyl group, and in the catalyst precursor composition, the content of nickel (Ni) is 10 to 35% by mass, the content of cobalt (Co) is 25 to 55% by mass, and the content of iridium (Ir) is 15 to 55% by mass (wherein, Ni + Co + Ir = 100% by mass).

Description

Technical Field

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

[0002] Hydrogen is a secondary energy source that is suitable for storage and transportation and has a low environmental load, so a hydrogen energy system that uses hydrogen as an energy carrier has attracted much attention. Currently, hydrogen is mainly produced by steam reforming fossil fuels. However, from the perspective of the global greenhouse effect and the depletion of fossil fuels, the importance of using renewable energy for alkaline water electrolysis as a power source has increased.

[0003] There are two types of water electrolysis. One is alkaline water electrolysis, which uses a high-concentration alkaline aqueous solution as the electrolyte. The other is solid polymer water electrolysis, which uses a solid polymer membrane (SPE) as the electrolyte. When using water electrolysis for large-scale hydrogen production, alkaline water electrolysis using cheap materials such as iron-based metals such as nickel is considered more suitable than solid polymer water electrolysis using electrodes that use a large amount of expensive precious metals.

[0004] The conductivity of a high-concentration alkaline aqueous solution increases with temperature, but the corrosiveness also increases. Therefore, the upper limit of the operating temperature is suppressed to about 80-90°C. Through the development of electrolytic cell materials that can withstand high temperatures and high-concentration alkaline aqueous solutions, various piping materials, low-resistance diaphragms, and electrodes with enlarged surface areas and catalysts, the electrolytic performance is improved to 0.3-0.4Acm -2 The voltage is improved to around 1.7-1.9V (efficiency 78-87%).

[0005] As anodes for alkaline water electrolysis, nickel-based materials that are stable in high-concentration alkaline aqueous solutions are used, and it is known that nickel-based anodes have a lifespan of more than several decades in the case of alkaline water electrolysis using a stable power source. However, when renewable energy is used as a power source, there are many severe conditions such as drastic start-stop and load fluctuations, and performance degradation of nickel-based anodes has become a problem.

[0006] In the past, platinum group metals, platinum group metal oxides, valve metal oxides, iron group oxides, lanthanide metal oxides, etc. were used as catalysts for oxygen-producing anodes used in alkaline water electrolysis (anode catalysts). Other known anode catalysts include nickel-based alloy systems such as Ni-Co and Ni-Fe; nickel with enlarged surface area; spinel-based Co 3 O 4 、NiCo 2 O 4 , LaCoO of perovskite system 3 、LaNiO 3 Conductive oxides (ceramic materials); precious metal oxides; oxides formed by lanthanide metals and precious metals, etc.

[0007] As an oxygen-producing anode used in alkaline water electrolysis, for example, an alkaline water electrolysis anode having a catalyst layer including a nickel-cobalt oxide and an iridium oxide or a ruthenium oxide formed on the surface of a nickel substrate has been proposed (Patent Document 1). In addition, an alkaline water electrolysis anode having a catalyst layer formed of a lithium-containing nickel oxide formed on the surface of a nickel substrate has been proposed (Patent Document 2). Furthermore, an electrolysis electrode having a catalyst layer including a catalyst such as a nickel-cobalt spinel oxide and an iridium oxide formed on the surface of a nickel substrate via an intermediate layer has been proposed (Patent Document 3).

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2017-190476

[0011] Patent Document 2: International Publication No. 2018 / 047961

[0012] Patent Document 3: International Publication No. 2019 / 172160 Summary of the invention

[0013] Problem that the invention aims to solve

[0014] However, even the alkaline water electrolysis anodes proposed in Patent Documents 1 to 3 cannot be said to have sufficiently low oxygen overvoltages, and further improvements in catalytic activity are required. In addition, the catalyst components are easily lost due to detachment during use, and it cannot be said that the catalytic activity can be stably exerted over a long period of time, and there is room for further improvement.

[0015] The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide an electrode for electrolysis having a catalyst having excellent catalytic activity such as low oxygen overvoltage and excellent stability such as reduced loss of catalyst components such as iridium (Ir), and a method for producing the same.

[0016] Solutions for solving problems

[0017] That is, according to the present invention, there is provided a method for producing an electrode for electrolysis as described below.

[0018] [1] A method for producing an electrode for electrolysis, comprising the following steps:

[0019] A step of directly or indirectly coating a catalyst precursor composition containing a nickel component, a cobalt component and an iridium component on a surface of a conductive substrate at least the surface of which is formed of nickel or a nickel-based alloy;

[0020] The 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

[0021] The step of heat-treating the primary calcined 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.

[0022] The iridium component is an iridium compound containing a carboxyl group,

[0023] The catalyst precursor composition contains 10 to 35 mass % nickel (Ni), 25 to 55 mass % cobalt (Co), and 15 to 55 mass iridium (Ir) (Ni+Co+Ir=100 mass %).

[0024] [2] The method for producing an electrode for electrolysis according to the above [1], wherein the mass ratio of the total content of nickel (Ni) and cobalt (Co) to the content of iridium (Ir) in the above catalyst precursor composition ((Ni+Co) / Ir) is 0.9 to 4.1.

[0025] [3] The method for producing an electrode for electrolysis according to [1] or [2], wherein the iridium compound is at least one of an iridium hydroxyacetyl chloride complex and iridium acetate.

[0026] [4] The method for producing an electrode for electrolysis according to any one of [1] to [3], further comprising the step of contacting and treating the primary calcined product with an alkali component.

[0027] Furthermore, according to the present invention, there is provided the following electrode for electrolysis.

[0028] [5] An electrode for electrolysis produced by the production method described in any one of [1] to [4] above.

[0029] [6] The electrode for electrolysis according to [5], which is an electrode for alkaline water electrolysis.

[0030] Effects of the Invention

[0031] According to the present invention, there can be provided an electrode for electrolysis having a catalyst having excellent catalytic activity such as low oxygen overvoltage and excellent stability such as reduced loss of catalyst components such as iridium (Ir), and a method for producing the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a cross-sectional view schematically showing one embodiment of the electrode for electrolysis of the present invention.

[0033] Figure 2This is a SEM image of a cross section of the electrolytic electrode produced in Example 3.

[0034] Figure 3 This is a SEM image of a cross section of the electrolytic electrode produced in Comparative Example 1. DETAILED DESCRIPTION

[0035] <Electrode for electrolysis>

[0036] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. Figure 1 FIG. 2 is a cross-sectional view schematically showing one embodiment of an electrode for electrolysis of the present invention. Figure 1 As shown, the electrode for electrolysis 10 of the present embodiment includes a conductive substrate 2 and a catalyst layer 6 formed on the surface of the conductive substrate 2. The electrode for electrolysis of the present invention will be described in detail below.

[0037] (Conductive substrate)

[0038] The conductive substrate 2 is a conductor used for passing electricity for electrolysis, and is a member having a function as a carrier for supporting the catalyst layer 6. At least the surface of the conductive substrate 2 (the surface forming the catalyst layer 6) is formed of nickel or a nickel-based alloy. That is, the conductive substrate 2 can be formed of nickel or a nickel-based alloy as a whole, or only the surface can be formed of nickel or a nickel-based alloy. Specifically, for the conductive substrate 2, a coating of nickel or a nickel-based alloy can be formed on the surface of a metal material such as iron, stainless steel, aluminum, titanium, etc. by plating.

[0039] The thickness of the conductive substrate is preferably 0.05 to 5 mm. The shape of the conductive substrate is preferably a shape having an opening for removing bubbles of generated oxygen, hydrogen, etc. For example, an expanded mesh or a porous expanded mesh can be used as the conductive substrate. When the conductive substrate is a shape having an opening, the opening ratio of the conductive substrate is preferably 10 to 95%.

[0040] (Catalyst layer)

[0041] The catalyst layer 6 is a layer having catalytic ability formed on the surface of the conductive substrate 2. Figure 1 As shown, in order to protect the conductive substrate 2, a catalyst layer 6 can be formed on the surface of the conductive substrate 2 via the nickel oxide layer 4. The catalyst layer 6 contains nickel cobalt spinel oxide (NiCo 2 O 4 ) and iridium oxide. Therefore, the electrolysis electrode 10 of the present embodiment is useful as an electrode for alkaline water electrolysis, and is particularly suitable as an anode (anode) for alkaline water electrolysis. There are no particular restrictions on the thickness and density of the catalyst layer, and it can be appropriately set according to the purpose of the electrode.

[0042] The types of metal elements in the catalyst layer 6 and their content ratios are substantially the same as the types of metal elements in the catalyst precursor composition used in the method for manufacturing an electrode for electrolysis described later and their content ratios. Therefore, in the catalyst layer, the content of nickel (Ni) is preferably 10 to 35% by mass, the content of cobalt (Co) is preferably 25 to 55% by mass, and the content of iridium (Ir) is preferably 15 to 55% by mass. Among them, Ni+Co+Ir=100% by mass. By making the types of metal elements in the catalyst layer and their content ratios as described above, the oxygen overvoltage becomes lower, and the loss of catalyst components such as iridium (Ir) can be further reduced.

[0043] The electrode for electrolysis of the present embodiment is manufactured by a specific manufacturing method described later. It is manufactured by a specific manufacturing method, so it is speculated that the state and composition (such as crystal state, crystal structure, type, composition and content of trace components, etc.) of the catalyst layer formed by the electrode for electrolysis manufactured by a method other than the specific manufacturing method are different. However, it is extremely difficult or substantially impossible to analyze and confirm the state and composition of such a catalyst layer.

[0044] <Method for producing an electrolytic electrode>

[0045] One embodiment of the method for manufacturing an electrode for electrolysis of the present invention comprises the following steps: a step of directly or indirectly coating a catalyst precursor composition containing a nickel component, a cobalt component and an iridium component on the surface of a conductive substrate (hereinafter, also referred to as a "coating step"); a step of heat-treating the conductive substrate coated with the catalyst precursor composition at 320 to 600° C. to obtain a primary calcined product (hereinafter, also referred to as a "heat treatment step"); and a step of heat-treating the primary calcined 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 a "post-baking step"). The iridium component in the catalyst precursor composition is an iridium compound containing a carboxyl group. In addition, in the catalyst precursor composition, the content of nickel (Ni) is 10 to 35% by mass, the content of cobalt (Co) is 25 to 55% by mass, and the content of iridium (Ir) is 15 to 55% by mass (wherein Ni+Co+Ir=100% by mass). Hereinafter, the method for producing the electrode for electrolysis of the present invention will be described in detail.

[0046] (Pre-treatment process)

[0047] Before the coating process, in order to remove the contamination particles such as metal and organic matter on the surface, it is preferred to perform chemical etching on the conductive substrate in advance. The consumption of the conductive substrate by chemical etching is preferably set to 30 g / m 2 Above and 400g / m 2In order to improve the adhesion with the intermediate layer, it is preferred to roughen the surface of the conductive substrate in advance. Examples of roughening treatment include sandblasting with sprayed powder, etching with an acid soluble in the substrate, and plasma spraying.

[0048] like Figure 1 As shown, in order to protect the conductive substrate 2, a nickel oxide layer 4 can be formed on the surface of the conductive substrate 2. The nickel oxide layer 4 can be formed, for example, by calcining the conductive substrate 2 at 450 to 550° C. in the atmosphere for 5 to 60 minutes. Alternatively, a solution obtained by dissolving nickel carboxylate in a solvent such as water can be applied to the surface of the conductive substrate, and then heat-treated at a temperature of 450° C. to 600° C. to form an intermediate layer on the conductive substrate. When the intermediate layer is formed on the conductive substrate, the catalyst layer is formed on the conductive substrate via the intermediate layer.

[0049] (Coating process)

[0050] In the coating process, a catalyst precursor composition containing a nickel component, a cobalt component and an iridium component is directly or indirectly coated on the surface of a conductive substrate via other layers such as the aforementioned intermediate layer. Then, 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 an iridium component, and adopting a so-called thermal cracking method, for example, compared with the case of using a catalyst precursor composition containing other iridium compounds such as iridium nitrate (Ir-nitrate) as an iridium component, 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 further formed directly or indirectly on a conductive substrate via other layers such as an intermediate layer.

[0051] Examples of the iridium compound containing a carboxyl group (hereinafter also referred to as "iridium compound") include iridium hydroxyacetyl chloride complex (IrHAC), iridium acetate (Ir-acetate), etc. Among them, at least one of iridium hydroxyacetyl chloride complex and iridium acetate is preferably used as the iridium compound.

[0052] As the nickel component and the cobalt component, both inorganic acid salts and organic acid salts that can generate nickel ions and cobalt ions can be used. Among them, nickel nitrate is preferably used as the nickel component, and cobalt nitrate is preferably used as the cobalt component.

[0053] 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% by mass, preferably 15 to 30% by mass. In addition, in the catalyst precursor composition, the content of cobalt (Co) is 25 to 55% by mass, preferably 30 to 55% by mass. Moreover, in the catalyst precursor composition, the content of iridium (Ir) is 15 to 55% by mass, preferably 20 to 55% by mass, and further preferably 23 to 52% by mass. It should be noted that Ni+Co+Ir=100% by mass. By using a catalyst precursor composition in which the content of nickel (Ni), cobalt (Co) and iridium (Ir) is within the above range, 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 further formed.

[0054] In the catalyst precursor composition, the mass ratio of the total content of nickel (Ni) and cobalt (Co) to the content of iridium (Ir) ((Ni+Co) / 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 in which the value of the "(Ni+Co) / Ir" ratio is within the above range, 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.

[0055] As a method for applying the catalyst precursor composition to the surface of the conductive substrate, a known method such as brush coating, roll coating, spin coating, electrostatic coating, etc. can be used. Then, the conductive substrate coated with the catalyst precursor composition is dried as needed. The drying temperature is preferably set to a temperature that avoids rapid evaporation of the agent (for example, about 60 to 80° C.).

[0056] (Heat treatment process)

[0057] In the heat treatment process, the conductive substrate coated with the catalyst precursor composition is heat treated (calcined) at 320 to 600°C, preferably at 330 to 550°C, and more preferably at 340 to 520°C. By making the temperature of the heat treatment within the above range, the metal components (nickel component, cobalt component and iridium component) in the catalyst precursor composition can be effectively thermally cracked to obtain a primary calcined product. It should be noted that if the temperature of the heat treatment is too high, the oxidation of the conductive substrate is easy to proceed, the electrode resistance increases, and sometimes leads to an increase in voltage loss. The time of the heat treatment can be appropriately set in consideration of the reaction rate, productivity, and the oxidation resistance of the surface of the catalyst layer formed.

[0058] 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 aforementioned application step. It should be noted that the application and drying of the catalyst precursor composition may be repeated in each layer, and the entirety may be heat-treated after the uppermost layer is formed, or the application and heat treatment of the catalyst precursor composition may be repeated in each layer, and the entirety may be heat-treated after the uppermost layer is formed.

[0059] (Alkali treatment process)

[0060] The manufacturing method of the electrode for electrolysis of the present embodiment preferably further comprises: a step (alkali treatment step) of contacting and treating the primary calcined product obtained in the above-mentioned heat treatment step with an alkali component. By contacting and treating the primary calcined product with an alkali component, impurities generated by the heat treatment can be effectively removed, the oxygen overvoltage is lower, and a catalyst layer with excellent stability can be further formed. Among them, when a catalyst precursor composition containing an iridium hydroxyacetyl chloride complex (IrHAC) is used as an iridium component, an acid component generated from IrHAC sometimes remains in the primary calcined product. Therefore, by contacting and treating the alkali component, the generated acid component can be effectively removed, the oxygen overvoltage is lower, and a catalyst layer with excellent stability can be further formed, so it is preferred.

[0061] As a specific method for contacting the primary burnt product with the alkali component and treating it, for example, there can be cited a method of immersing the primary burnt product in an aqueous solution of the alkali component. As the alkali component, alkali metal hydroxides such as sodium hydroxide (NaOH) and potassium hydroxide (KOH) can be used. The concentration of the alkali component in the aqueous solution of the alkali component can be appropriately set, for example, in the range of 4 to 8 mass %. The temperature of the aqueous solution of the alkali component can be appropriately set, for example, in the range of 20 to 40°C. In addition, the time for immersing the primary burnt product in the aqueous solution of the alkali component can be appropriately set, for example, in the range of 1 to 5 hours. It is preferred that the primary burnt product be immersed in the aqueous solution of the alkali component and then washed and dried.

[0062] (Post-baking process)

[0063] In the post-baking process, the primary calcined product is heat treated at 350-600°C, preferably at 380-580°C, and more preferably at 400-560°C. After the primary calcined product is naturally cooled, it is heat treated again (post-baking) under prescribed temperature conditions, so that a catalyst layer containing nickel-cobalt spinel oxide and iridium oxide can be formed on the surface of the conductive substrate to obtain the target electrolysis electrode. It should be noted that if post-baking is not implemented (the primary calcined product is directly used as an electrolysis electrode), iridium is easily lost from the catalyst layer due to repeated electrolysis, and a catalyst layer with excellent stability cannot be formed.

[0064] <Electrolytic Cell>

[0065] The electrode for electrolysis of the present embodiment can be used not only as an anode for electrolysis, but also as a cathode for electrolysis. Furthermore, the electrode for electrolysis of the present embodiment can be used as an anode for alkaline water electrolysis, and can also be used as a cathode for alkaline water electrolysis. That is, if the electrode for electrolysis of the present embodiment is used, an electrolytic cell such as an alkaline water electrolyzer can be formed. Hereinafter, the constituent materials other than the anode when the electrode for electrolysis of the present embodiment is used as an anode for alkaline water electrolysis to form an alkaline water electrolyzer are described.

[0066] As the cathode, it is preferred to select 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 covered with an active cathode can be used. As the shape of the cathode substrate, in addition to a plate-like shape, an expanded mesh, a porous expanded mesh, etc. can also be cited.

[0067] As cathode materials, there are porous nickel with large surface area, Ni-Mo system materials, etc. In addition, there are Raney nickel system materials such as Ni-Al, Ni-Zn, Ni-Co-Zn; sulfide system materials such as Ni-S; Ti 2 Ni and other hydrogen storage alloy materials. As catalysts, catalysts with low hydrogen overvoltage, high short-circuit stability, high anti-poisoning properties are preferred. As other catalysts, metals such as platinum, palladium, ruthenium, iridium, and their oxides are preferred.

[0068] As the diaphragm for electrolysis, asbestos, nonwoven fabrics, ion exchange membranes, polymer porous membranes, and composite membranes of inorganic substances and organic polymers can be used. Specifically, the following ion permeable diaphragms can be used: organic fiber cloth is contained in a mixture of hydrophilic inorganic materials such as calcium phosphate compounds and calcium fluoride and organic binding materials such as polysulfone, polypropylene, and polyvinylidene fluoride. In addition, the following ion permeable diaphragms can be used: stretched organic fiber cloth is contained in a film-forming mixture of granular inorganic hydrophilic materials such as antimony and zirconium oxides and hydroxides and organic binders such as fluorocarbon polymers, polysulfone, polypropylene, polyvinyl chloride, and polyvinyl butyral.

[0069] If an alkaline water electrolyzer using the electrolysis electrode of the present embodiment as a constituent element is used, a high concentration of alkaline aqueous solution can be electrolyzed. For the alkaline aqueous solution used as an electrolyte, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) is preferred. The concentration of the alkaline aqueous solution is preferably 1.5 to 40% by mass. In addition, when the concentration of the alkaline aqueous solution is 15 to 40% by mass, the conductivity is large and the power consumption can be suppressed, so it is preferred. Furthermore, considering the cost, corrosiveness, viscosity, operability, etc., the concentration of the alkaline aqueous solution is preferably 20 to 30% by mass.

[0070] Example

[0071] Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples. It should be noted that "parts" and "%" in Examples and Comparative Examples are based on mass unless otherwise specified.

[0072] <Manufacturing of anode substrate>

[0073] After sandblasting, the expanded alumina particles made of nickel were immersed in 20 mass % hydrochloric acid and etched at a temperature near the boiling point for 3 minutes, and then air annealed at 500° C. for 30 minutes to obtain an anode substrate having a nickel oxide (NiOx) layer formed on the surface.

[0074] <Manufacturing of anodes for electrolysis>

[0075] (Example 1)

[0076] Nickel nitrate (Ni(NO 3 ) 2 6H 2 O), cobalt nitrate (Co(NO 3 ) 2 6H 2 O), and iridium hydroxyacetyl chloride complex (IrHAC) were dissolved in pure water to obtain a catalyst precursor composition (coating liquid) having a mass ratio of nickel (Ni): cobalt (Co): iridium (Ir) of Ni: Co: Ir = 27: 53: 20. The obtained coating liquid was coated with a metal amount of 1.5 g / m 2 The surface of the nickel oxide layer of the above-mentioned anode substrate is coated in a manner. Thereafter, thermal cracking is performed at 350°C for 10 minutes by heat treatment (calcination) in an air circulation electric furnace. The treatment from coating of the coating liquid to thermal cracking is repeated 4 times to obtain a primary calcined product. The primary calcined product is subjected to an alkaline treatment by immersing it in a 6% sodium hydroxide aqueous solution at 30°C for 3 hours. After washing with pure water and drying with an air gun, it is placed in an air circulation electric furnace and post-baking is performed by heat treatment at 500°C for 60 minutes. Thus, an anode for alkaline water electrolysis (electrode for electrolysis) having a catalyst layer containing nickel cobalt spinel oxide and iridium oxide formed on the surface of the anode substrate is obtained. The metal amount of the formed catalyst layer is 6 g / m 2 .

[0077] (Examples 2 to 5, Comparative Examples 1 to 5)

[0078] The conditions shown in Table 1 were set, and except for this, an anode for alkaline water electrolysis (electrode for electrolysis) was obtained in the same manner as in Example 1. It should be noted that for Comparative Examples 1 to 5, the primary fired product was used directly as the anode. The SEM images of the cross sections of the electrodes for electrolysis produced in Example 3 and Comparative Example 1 are shown in Figure 2 and 3 .

[0079] Table 1: Fabrication of Electrodes for Electrolysis

[0080]

[0081] <Evaluation>

[0082] (Determination of oxygen overvoltage)

[0083] Using 30% potassium hydroxide aqueous solution at 80°C and a current density of 10 kA / m 2 The oxygen overvoltage (mV) of the manufactured electrolysis electrode was measured under the conditions of . The results are shown in Table 2.

[0084] (Measurement of Ir Residue in Catalyst Layer)

[0085] The fluorescence X-ray intensity of iridium (Ir) in the catalyst layer of the electrolysis electrode before and after the oxygen overvoltage measurement was measured using a fluorescence X-ray analyzer. Then, the remaining amount (%) based on the amount of iridium (Ir) before the oxygen overvoltage measurement was calculated from the measured fluorescence X-ray intensity ratio of iridium (Ir). The results are shown in Table 2.

[0086] Table 2: Evaluation of electrodes for E electrolysis

[0087]

[0088] <Manufacturing and evaluation of an electrolytic anode having an intermediate layer>

[0089] (Example 6)

[0090] Nickel acetate tetrahydrate (Ni(CH 3 COO 2 ·4H 2O) is dissolved in pure water to obtain an aqueous solution with a concentration of 0.57 mol / L of nickel acetate. In addition, after sandblasting the expanded alumina particles made of nickel, it is immersed in 20% by mass hydrochloric acid and etched for 3 minutes near the boiling point to obtain an anode substrate. After applying an aqueous solution of nickel acetate on the surface of the obtained anode substrate with a brush, it is dried at 60°C for 10 minutes. Then, heat treatment is performed at 500°C for 10 minutes under an atmospheric atmosphere. Repeat the operation from coating with an aqueous solution of nickel acetate to heat treatment 5 times to obtain an anode substrate having an intermediate layer formed on its surface. Then, using the above-mentioned anode substrate having an intermediate layer formed on its surface, in addition, an anode (electrolysis electrode) for alkaline water electrolysis having a catalyst layer formed on the surface of the anode substrate separated by an intermediate layer is obtained in the same manner as in the aforementioned Example 3.

[0091] The oxygen overvoltage of the obtained electrolytic 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 after the oxygen overvoltage measurement was 100%, and it was confirmed that iridium (Ir) was not substantially consumed, similarly to the electrolysis electrodes of Examples 1 to 5.

[0092] Industrial Applicability

[0093] The electrode for electrolysis of the present invention is suitable as, for example, an anode for alkaline water electrolysis.

[0094] Description of Reference Numerals

[0095] 2: Conductive substrate

[0096] 4: Nickel oxide layer

[0097] 6: Catalyst layer

[0098] 10: Electrode for electrolysis.

Claims

1. A manufacturing method of an electrode for electrolysis, comprising the following steps: A step of directly or indirectly coating a surface of a conductive substrate formed of nickel or a nickel-based alloy at least on its surface with a catalyst precursor composition containing a nickel component, a cobalt component, and an iridium component; A step of thermally cracking the conductive substrate coated with the catalyst precursor composition at 320 to 600 °C to obtain a primary fired product; and, A post-baking 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 carboxyl group, In the catalyst precursor composition, the content of nickel (Ni) is 10 to 35% by mass, the content of cobalt (Co) is 25 to 55% by mass, and the content of iridium (Ir) is 15 to 55% by mass, wherein, Ni + Co + Ir = 100% by mass.

2. The manufacturing method of the electrode for electrolysis according to claim 1, wherein, 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 0.9 to 4.

1.

3. The manufacturing method of the electrode for electrolysis according to claim 1 or 2, wherein, The iridium compound is at least any one of iridium hydroxyacetyl chloride complex and iridium acetate.

4. The manufacturing method of the electrode for electrolysis according to claim 1 or 2, further comprising a step of bringing the primary fired product into contact with an alkali component and treating it.

5. An electrode for electrolysis, which is manufactured by the manufacturing method according to any one of claims 1 to 4.

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

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