Manufacturing method for iridium-coated titanium electrodes

Abstract

Provided is a method for producing an iridium-coated titanium electrode that can suppress titanium elution when used as an electrode for water electrolysis. [Solution] The manufacturing method for an iridium-coated titanium electrode 100 includes a chemical solution application step in which a chemical solution containing iridium is applied to an electrode precursor 2, which is an electrode precursor 2 made of a substrate 1 formed of titanium or a titanium alloy and coated with platinum.The chemical solution contains an iridium-organic acid complex as the iridium, and this iridium-organic acid complex does not contain chlorine.

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an iridium-coated titanium electrode. [Background technology]

[0002] Patent Document 1 discloses an electrode for electrolysis having an electrode substrate containing a conductive metal and a catalyst layer formed on the electrode substrate. This electrode for electrolysis is used, for example, in the electrolysis of an aqueous solution containing chlorides to generate hypochlorous acid.

[0003] The electrolysis electrode disclosed in Patent Document 1 has a catalytic layer including a platinum-containing layer containing platinum and an iridium oxide-containing layer containing iridium oxide, and the platinum-containing layer is substantially free of platinum oxide. For example, this electrolysis electrode is manufactured by forming a platinum-containing layer containing 99% by mass of platinum on a titanium substrate, and then forming an iridium oxide-containing layer containing 70% by mass of iridium oxide and 30% by mass of tantalum oxide on the platinum-containing layer so as to occupy 50% of the area of ​​the platinum-containing layer. Specifically, this electrode is manufactured by the following method. First, a Ti plate is sandblasted to roughen the surface of the Ti plate, and then the Ti surface is degreased with an ultrasonic degreasing solution and etched with a 5 wt% ammonium fluoride aqueous solution. Then, half the area of ​​the Ti plate was masked with tape, and the masked Ti plate was placed in a Pt plating solution (Pt: 5 wt%, sulfuric acid: 50 g / L, pH = 1) at 0.5 A / dm 2 By electroplating Pt under these conditions for 15 minutes, a platinum-containing layer is formed on half of the area of ​​the Ti plate. The remaining half of the area is then masked with tape and coated with an iridium chloride solution (Ir: 5 wt%, pH = 1). The plate is then dried in a dryer at 100°C for 15 minutes and baked in an electric furnace at 500°C for 30 minutes. By repeating this process of coating with the iridium chloride solution, drying, and heat treatment, a desired iridium oxide-containing layer is formed, resulting in an electrode for electrolysis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-111874 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, iridium-coated titanium electrodes, which are titanium electrodes in which a titanium substrate is coated with iridium, are used as electrodes for electrolyzing, for example, aqueous solutions containing chlorides to generate hypochlorous acid. However, with such iridium-coated titanium electrodes, titanium may dissolve into water during use as an electrode for electrolysis. Therefore, it is desirable to provide a method for producing iridium-coated titanium electrodes that can suppress titanium dissolution when used as an electrode for water electrolysis.

[0006] The present disclosure has been made in light of these circumstances, and its purpose is to provide a method for producing an iridium-coated titanium electrode that can suppress titanium elution when used as an electrode for water electrolysis. [Means for solving the problem]

[0007] In order to achieve the above object, the method for producing an iridium-coated titanium electrode according to the present disclosure comprises the steps of: a chemical solution application step of applying a chemical solution containing iridium to an electrode precursor in which a substrate formed of titanium or a titanium alloy is coated with platinum; the chemical solution contains an iridium organic acid complex as iridium, The organic acid complex of iridium does not contain chlorine.

[0008] According to the present disclosure, it is possible to provide a method for producing an iridium-coated titanium electrode that can suppress titanium elution when used as an electrode for water electrolysis. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram of a substrate. [Figure 2] FIG. 2 is a schematic diagram of an electrode precursor. [Figure 3] FIG. 2 is a schematic diagram of a second precursor. [Figure 4] FIG. 1 is a schematic diagram of a third precursor. [Figure 5] FIG. 1 is a schematic diagram of an iridium-coated titanium electrode. DETAILED DESCRIPTION OF THE INVENTION

[0010] A method for producing an iridium-coated titanium electrode according to an embodiment of the present disclosure will now be described.

[0011] The method for manufacturing an iridium-coated titanium electrode according to this embodiment includes a chemical solution application step in which a chemical solution containing iridium (Ir) is applied to an electrode precursor in which a substrate formed of titanium (Ti) or a titanium alloy is coated with platinum (Pt), and this chemical solution contains an organic acid complex of iridium as iridium, and this organic acid complex of iridium does not contain chlorine.

[0012] The method for producing an iridium-coated titanium electrode according to this embodiment makes it possible to produce an iridium-coated titanium electrode that can suppress titanium elution when used as an electrode for electrolyzing water.

[0013] The iridium-coated titanium electrode produced by the method for producing an iridium-coated titanium electrode according to this embodiment can be suitably used as a so-called insoluble electrode, and when used as an electrode for electrolyzing water, titanium elution is effectively suppressed.

[0014] The iridium-coated titanium electrode manufactured by the method for manufacturing an iridium-coated titanium electrode according to this embodiment can be particularly suitably used as an electrode for electrolyzing an aqueous solution containing chloride to generate hypochlorous acid.

[0015] The method for producing an iridium-coated titanium electrode according to this embodiment will be described in detail below.

[0016] As an example, the method for producing an iridium-coated titanium electrode according to this embodiment can include a base layer forming step of coating a substrate (hereinafter sometimes simply referred to as substrate) made of titanium or a titanium alloy with platinum to obtain an electrode precursor, a chemical solution applying step of applying a chemical solution containing iridium to the electrode precursor formed by coating a substrate made of titanium or a titanium alloy with platinum, and a firing step of firing the electrode precursor with the chemical solution applied thereto.

[0017] The underlayer forming step is a step of forming a platinum layer as an underlayer on the surface of the substrate by plating or the like, thereby obtaining an electrode precursor as a substrate coated with platinum.

[0018] The substrate may be any material formed from titanium or a titanium alloy. The substrate may be solid or porous. The substrate may be in the form of a thick block or a thin plate. The substrate may be a solid plate, a mesh such as expanded metal or micromesh, a sintered body made by entangling and sintering fine wires (fibers) of titanium or a titanium alloy, or a sintered body made by molding and sintering titanium or titanium alloy powder.

[0019] The underlayer is preferably formed so that when an iridium-coated titanium electrode using a substrate is used for water electrolysis (hereinafter sometimes simply referred to as electrolysis), the entire portion of the iridium-coated titanium electrode that comes into contact with the electrolyte (for example, the aqueous solution to be electrolyzed) is covered with platinum. By producing an iridium-coated titanium electrode using an electrode precursor in which an underlayer is formed on a substrate, it becomes easier to suppress titanium elution when the iridium-coated titanium electrode is used for electrolysis.

[0020] The thickness of the underlayer is preferably 0.3 μm or more. This makes it easier to suppress the elution of titanium when an iridium-coated titanium electrode produced from this electrode precursor is used. In other words, it makes it easier to suppress the elution of titanium from the iridium-coated titanium electrode.

[0021] The underlayer is sufficient if it has a thickness of 0.3 μm or more and at most 1.2 μm or less. The underlayer may be formed to a thickness exceeding 1.2 μm, but it is not necessary to form the underlayer excessively thick. The underlayer is preferably 0.5 μm or more. From an economical standpoint, the underlayer is sufficient if it is 1.0 μm or less.

[0022] The method for coating the substrate with platinum is not particularly limited, but one example of a method for coating the substrate with platinum is a plating method. The plating method may be an electrolytic plating method or an electroless plating method. By forming the underlayer by plating, the surface of the substrate can be densely covered. By densely covering the surface of the substrate, it becomes easier to suppress the elution of titanium from the iridium-coated titanium electrode.

[0023] When the substrate is coated with platinum by plating, the plating process may include at least one of a degreasing process for degreasing the substrate surface, an oxide film removal process for removing an oxide film on the substrate surface, and a roughening process for roughening the substrate surface. By including one or more of these processes, it becomes easier to suppress the elution of titanium from the iridium-coated titanium electrode.

[0024] The surface roughening treatment may be performed, for example, by immersing the substrate in an aqueous solution of oxalic acid, an aqueous solution of hydrogen fluoride, or an aqueous solution of ammonium fluoride.

[0025] The chemical solution application step and the firing step are steps for supporting iridium on the surface of the electrode precursor. By performing the chemical solution application step and the firing step, a structure containing iridium (for example, a layer containing iridium, hereinafter sometimes referred to as a supported portion) is formed on the surface of the electrode precursor. Hereinafter, the chemical solution application step and the firing step performed immediately thereafter may be collectively referred to as the supporting step.

[0026] The chemical solution application step and the firing step are outlined below. In the chemical solution application step, a chemical solution containing iridium (hereinafter sometimes simply referred to as chemical solution) is applied to (supported on) the electrode precursor. Then, in the firing step, the electrode precursor with the chemical solution applied thereto is fired, thereby supporting iridium on the surface of the electrode precursor and forming a supported portion. The electrode precursor with the chemical solution applied thereto may be subjected to a drying treatment to remove the solvent component of the chemical solution before firing in the firing step.

[0027] Hereinafter, an electrode precursor to which a chemical solution has been further attached may be referred to as a second precursor. Furthermore, among the second precursors, a precursor from which the solvent of the supported chemical solution has been removed by a drying process or the like may be referred to as a third precursor. Note that the second precursor and the third precursor are included in the electrode precursor according to this embodiment. In the following description, when simply referring to a second precursor, the third precursor is included in the concept of the second precursor.

[0028] The support portion is a portion that functions as a catalyst when the iridium-coated titanium electrode is used in electrolysis.

[0029] The support may contain an element other than iridium (e.g., tantalum). The support may be, for example, an alloy of iridium and a metal element other than a platinum group element. The metal element other than a platinum group element does not have to function as a catalyst when the iridium-coated titanium electrode is used in electrolysis.

[0030] The support portion may be formed in the form of a dense layer on the underlayer, or may be formed in the form of islands (scattered) or porous (a layer with many defects, i.e., holes) on the underlayer.

[0031] The amount of iridium supported on the electrode precursor, i.e., the amount of iridium supported on the iridium-coated titanium electrode, was 2.0 g / m2 (as iridium oxide) in catalytic amount relative to the surface of the substrate. 2 More than 20.0g / m 2The amount of iridium supported is preferably 2.0 g / m or less in terms of catalytic amount. 2 If the amount is more than this, it is possible to effectively suppress the elution of titanium when the iridium-coated titanium electrode is used as an electrode for electrolysis of water. The amount of iridium supported is 20.0 g / m in terms of catalytic amount. 2 If you have enough, 20.0 g / m is sufficient from an economical point of view. 2 It is preferable to do the following:

[0032] The chemical solution used contains an iridium organic acid complex as the iridium supply source. Note that the iridium organic acid complex does not include chlorine (Cl). In other words, the chemical solution used is an iridium organic acid complex that does not contain chlorine as a constituent element. This makes it possible to suppress the elution of titanium when the iridium-coated titanium electrode is used as an electrode for water electrolysis.

[0033] The solvent for the chemical solution may be water or an organic solvent, and is preferably an alcohol-based solvent, with 2-propanol (isopropyl alcohol) being particularly preferred.

[0034] The organic acid complex of iridium is preferably an organometallic complex of iridium having a carboxylic acid group, which increases the solubility of the organic acid complex of iridium in alcoholic solvents, particularly 2-propanol, and improves the efficiency of forming a support by adhesion of the chemical solution.

[0035] Among organometallic complexes of iridium having a carboxylic acid group, iridium diethylhexanoate is particularly suitable. Iridium diethylhexanoate is highly soluble in 2-propanol, which contributes to improving the efficiency of forming a support by adhesion of a chemical solution.

[0036] It is preferable that the chemical solution does not contain a compound containing chlorine as a component other than the iridium organic acid complex. In this embodiment, not containing a compound containing chlorine means that the chlorine content in the chemical solution is below the detection limit. Although this depends on the detection capability of the measuring device, for example, when chlorine in the chemical solution is quantified using a chlorine analyzer (TOX-2100H) manufactured by Mitsubishi Chemical, the quantified value can be 0 ppm or more and 500 ppm or less.

[0037] Examples of methods for adhering the chemical solution to the electrode precursor in the chemical solution adhering process include a method of applying the chemical solution to the electrode precursor (hereinafter referred to as the application method) and a method of immersing the electrode precursor in the chemical solution.

[0038] Examples of the application method include a method of applying the chemical solution to the surface of the electrode precursor with a brush or a coating roller, a method of spraying the chemical solution onto the surface of the electrode precursor, and a method of transferring the chemical solution from a carrier holding the chemical solution to the surface of the electrode precursor.

[0039] In the firing step, the second precursor may be fired for 20 minutes to 80 minutes in an atmosphere at a temperature of 400° C. or higher but lower than 700° C., preferably 400° C. or higher but lower than 600° C. As a result, the supported portion is formed to contain iridium.

[0040] If the firing step is performed in air, the support portion will be formed mainly of iridium oxide.

[0041] The calcination temperature in the calcination step is preferably less than 700°C, more preferably 600°C or less. When the calcination temperature is less than 700°C, thermal alteration of the titanium substrate can be avoided. Furthermore, when the calcination temperature is less than 700°C, excessive growth of iridium crystals during calcination can be suppressed, and a decrease in the catalytic performance of iridium can be avoided. The calcination temperature is preferably 400°C or higher. Furthermore, the calcination time is preferably 20 minutes or longer. By setting the calcination temperature to 400°C or higher, volatile components such as organic matter can be sufficiently removed from the support, and iridium crystals can be grown appropriately, making it possible to fully utilize the catalytic performance of iridium.

[0042] In the supporting step, the amount of iridium supported on the supported portion may be adjusted by alternately repeating the adhesion step and the calcination step. That is, in the supporting step, the amount of iridium supported on the supported portion can be increased by alternately repeating the adhesion step and the calcination step. That is, by using the iridium-coated titanium electrode according to this embodiment as an electrode precursor and repeating the adhesion step and the calcination step on it in the supporting step, the amount of iridium supported on the supported portion in the iridium-coated titanium electrode can be increased.

[0043] A specific example of the method for producing an iridium-coated titanium electrode according to this embodiment will be described below.

[0044] FIG. 1 shows a substrate 1 made of titanium or a titanium alloy. In the method for producing an iridium-coated titanium electrode according to this embodiment, the substrate 1 shown in FIG. 1 is first subjected to an underlayer formation step. In the underlayer formation step, a platinum underlayer 11 is formed on the surface of the substrate 1 by, for example, plating, as shown in FIG. 2, to produce an electrode precursor 2. Note that it is preferable to roughen the surface of the substrate 1 before forming the platinum underlayer 11 on the surface of the substrate 1.

[0045] Next, as shown in FIG. 3, the electrode precursor 2 is subjected to a supporting step.

[0046] In the supporting step, first, the electrode precursor 2 is subjected to a chemical solution adhering step. In the chemical solution adhering step, the electrode precursor 2 is coated with a chemical solution or the electrode precursor 2 is immersed in the chemical solution, thereby adhering the chemical solution containing iridium to the electrode precursor 2, thereby obtaining a second precursor 3. In FIG. 3, the layer of the chemical solution adhering to the surface of the electrode precursor 2 is shown as a chemical solution layer 12.

[0047] The second precursor 3 is then subjected to a calcination step. As an example, the second precursor 3 may be subjected to a drying treatment before being subjected to the calcination treatment to remove the solvent component of the drug solution layer 12. FIG. 4 shows a third precursor 4, which is the second precursor 3 after being subjected to the drying treatment. In the third precursor 4, the drug solution layer 12 (see FIG. 3) has dried to form a drug layer 13 with a remaining solid content.

[0048] When the third precursor 4 (second precursor 3) is subjected to a firing treatment, organic matter is removed from the drug layer 13 (drug solution layer 12), and a supporting portion, i.e., an iridium layer 14, which is a layer of a metal or oxide containing iridium, is formed, thereby obtaining an iridium-coated titanium electrode 100 in which iridium is coated on the titanium substrate (substrate 1).

[0049] By repeating the supporting step multiple times, an iridium-coated titanium electrode 100 with an increased thickness of the iridium layer 14 (supported portion) can be obtained. [Example]

[0050] The method for manufacturing an iridium-coated titanium electrode according to this embodiment will be described below based on examples.

[0051] Example 1 The substrate used was a titanium (Ti) expanded metal cut into a flat plate (LW (longitudinal distance between centers of mesh) 2 mm, SW (shorter distance between centers of mesh) 3 mm, W (spacing width) 0.65 mm, T (plate thickness) 0.4 mm). This substrate was then subjected to a base layer forming step to obtain an electrode precursor, and the electrode precursor was then subjected to a supporting step to produce the iridium-coated titanium electrode according to Example 1.

[0052] In the underlayer forming process, first, the substrate was subjected to ultrasonic degreasing to degrease the substrate. For the ultrasonic degreasing, Aiwa Medical Industry Co., Ltd. AU-710CO-10 (ultrasonic frequency: 28 kHz) was used. The ultrasonic degreasing treatment time was 1 minute.

[0053] After ultrasonic degreasing, the substrate was subjected to electrolytic degreasing. The electrolytic degreasing was performed using Etrex 12 manufactured by EEJA Co., Ltd. as the electrolytic degreasing solution. The voltage applied during the electrolytic degreasing was 8.0 V. The treatment time for the electrolytic degreasing was 1 minute.

[0054] After the electrolytic degreasing treatment, the substrate was immersed in a mixed aqueous solution of 4 wt% ammonium hydrogen fluoride and 10 wt% nitric acid for about 10 seconds to perform an oxide film removal treatment to remove the oxide film from the substrate.

[0055] After the oxide film removal treatment, the substrate was immersed in a 0.2 wt % aqueous solution of ammonium hydrogen fluoride and held there for approximately 60 seconds, thereby performing a surface roughening treatment to roughen the surface of the substrate.

[0056] Next, the substrate after the surface roughening treatment was subjected to a plating treatment in which platinum was plated.

[0057] The plating solution contained 5 wt % platinum (Pt) and 100 g of sulfuric acid per 1 L of the plating solution. The pH of the plating solution was 1.

[0058] The plating treatment was electrolytic plating. A Pt / Ti plate electrode was placed as the anode in the plating solution (60°C), and the substrate was placed as the cathode. The plating temperature was 0.5 A / dm 2 Platinum was plated on the surface of the substrate by passing a constant current between the anode and cathode, and the amount of platinum carried on the surface of the substrate was 6 g / m 2 An underlayer (platinum layer) was formed so as to form an electrode precursor. The time for which a constant current was applied (plating time) was 10 minutes.

[0059] Next, the electrode precursor was subjected to a supporting step in which iridium (Ir) was supported on the electrode precursor by firing as follows to obtain an iridium-coated titanium electrode.

[0060] In the supporting step, first, the electrode precursor was subjected to a chemical solution application step, and a chemical solution containing iridium was applied to the plate surface of the electrode precursor in the following manner.

[0061] The formulation of the chemical solution applied to the plate surface of the electrode precursor is as follows: The solvent for the chemical solution was special-grade isopropyl alcohol (2-propanol, Grade 1, manufactured by Kanto Chemical Co., Ltd.). Then, iridium diethylhexanoate (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and tantalum butoxide (tantalum (5) N-butoxide, manufactured by Sanyo Chemical Co., Ltd.) were dissolved in this solvent so that the concentrations of iridium and tantalum in the solvent were 3.5 wt% and 1.5 wt%, respectively, to prepare the chemical solution for application. Note that iridium diethylhexanoate is a chlorine-free organic acid complex of iridium, and is an organometallic complex of iridium with a carboxylic acid group.

[0062] Then, this chemical solution was applied once to the plate surface of the electrode precursor using a brush, and the chemical solution was adhered to the plate surface of the electrode precursor, thereby obtaining a second precursor.

[0063] Next, the second precursor was subjected to a calcination process. In the calcination process, the second precursor was first further dried under atmospheric conditions to evaporate the solvent of the attached chemical solution, thereby obtaining a third precursor as the second precursor. This drying process was carried out in a dryer tank through which hot air at 100°C was passed. The drying process time (the time held in the tank) was 20 minutes. The drying process was carried out in a batch process.

[0064] The third precursor was further calcined in the atmosphere, thereby supporting iridium oxide on the surface of the electrode precursor to form a support portion, and an iridium-coated titanium electrode was obtained. The calcination was carried out by placing the third precursor in a calcination furnace (in the atmosphere) adjusted to 500°C and holding it for 30 minutes (i.e., calcination for 30 minutes).

[0065] In Example 1, the iridium-coated titanium electrode obtained as described above was used as an electrode precursor, and the chemical solution application step and the baking step were repeated several times. Finally, a catalytic amount (as iridium oxide) of 5 g / m was applied to the surface of the substrate. 2 An iridium-coated titanium electrode carrying the iridium (having an iridium layer formed thereon) was obtained, and this was designated as the iridium-coated titanium electrode according to Example 1.

[0066] (Examples 2 and 3) Examples 2 and 3 differ from Example 1 in that the amount of supported iridium was increased by increasing the number of times the chemical solution application step and the firing step were repeated, but otherwise iridium-coated titanium electrodes were obtained in the same manner as Example 1.

[0067] In Example 2, the catalyst amount was 10 g / m 2 An iridium-coated titanium electrode carrying the above iridium was obtained, which was used as the iridium-coated titanium electrode according to Example 2.

[0068] In Example 3, the catalyst amount was 15 g / m 2 An iridium-coated titanium electrode carrying the above iridium was obtained, which was designated as the iridium-coated titanium electrode according to Example 3.

[0069] (Comparative Example 1) Comparative Example 1 differs from Example 1 in that iridium diethylhexanoate (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) used in the chemical solution in Example 1 was replaced with sodium chloroiridate crystals (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), and an iridium-coated titanium electrode was obtained in the same manner as in Example 1 except for the above.

[0070] (Comparative Example 2) Comparative Example 2 differs from Comparative Example 1 in that the underlayer formation step was omitted, and an iridium-coated titanium electrode was otherwise obtained in the same manner as Comparative Example 1. That is, unlike the iridium-coated titanium electrode of Comparative Example 1, the iridium-coated titanium electrode of Comparative Example 2 does not have a platinum layer as an underlayer.

[0071] (Reference example 1) In Reference Example 1, the substrate used in Example 1 was used as the electrode according to Reference Example 1.

[0072] (Reference example 2) Reference Example 2 differs from Example 1 in that the supporting step was omitted, but otherwise the same procedures as in Example 1 were carried out to obtain an electrode precursor in which only a platinum layer was formed as an underlayer on a substrate, and this was used as the electrode of Reference Example 2.

[0073] Table 1 lists the electrodes according to the examples and comparative examples obtained as described above.

[0074] [Table 1]

[0075] The electrodes of each Example and Comparative Example were further subjected to a test to evaluate the amount of titanium eluted from the electrode when used as an electrode for electrolysis of an aqueous solution containing chloride ions. This test was performed in accordance with the provisions of "7.4.3 Safety test b) for hypochlorous acid water" in the JIS standard "JIS B 8701:2017." The amount of titanium eluted (g / ml) obtained as a result of this elution test is also shown in Table 1.

[0076] As shown by the comparison between Reference Examples 1 and 2 in Table 1, the electrode in which only a platinum layer (underlayer) is formed by plating on a titanium substrate (Reference Example 2) better suppresses titanium elution than the electrode in which no platinum layer is formed (Reference Example 1). Note that, in the case of an electrode having a platinum layer but no iridium supported thereon, such as Reference Example 2, it is known that the performance of the electrode for electrolysis of an aqueous solution containing chloride ions is generally insufficient.

[0077] In an electrode having no underlayer and only a support portion containing iridium, as in Comparative Example 2, the elution of titanium can be suppressed more effectively than in Reference Example 1. However, in Comparative Example 2, the elution of titanium cannot be sufficiently suppressed.

[0078] When a chlorine-containing compound is used as the iridium source in the supporting step as in Comparative Example 1, the iridium-coated titanium electrode cannot sufficiently suppress the elution of titanium even when it has a platinum layer as an underlayer. Considering the case of Reference Example 2, it is thought that when a chlorine-containing compound is used as the iridium source in the supporting step, the function of the underlayer to suppress the elution of titanium from the substrate is weakened.

[0079] In contrast to the above-mentioned Reference Example 2 and Comparative Examples 1 and 2, the iridium-coated titanium electrodes of Examples 1 to 3 effectively suppressed titanium elution, and within the range of evaluation according to the above-mentioned JIS standard, the level was below the lower detection limit (0 mg / L). Considering the results of Comparative Example 1, it can be seen that when a chlorine-free compound is used as the iridium source in the supporting step, a supported portion can be formed while maintaining the function of the underlayer to suppress elution of titanium from the substrate.

[0080] In addition, the above-mentioned JIS standard "JIS B 8701:2017" stipulates in "5.3.3 Safety of Hypochlorous Acid Water" that the allowable amount of titanium elution is less than 0.05 g / mL. As shown in Table 1, the iridium-coated titanium electrodes of Examples 1-3 meet this requirement for the amount of elution (in Table 1, the "JIS compliant" column: "compliant"). In the cases of Comparative Examples 1 and 2, this requirement for the amount of elution is not met (in Table 1, the "JIS compliant" column: "non-compliant").

[0081] As described above, a method for producing an iridium-coated titanium electrode that can suppress titanium elution when used as an electrode for water electrolysis can be provided.

[0082] It should be noted that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited to these, and can be modified as appropriate within the scope of the purpose of the present disclosure. [Industrial Applicability]

[0083] The present disclosure is applicable to methods for manufacturing iridium-coated titanium electrodes. [Explanation of symbols]

[0084] 1: Base material 11: Base layer 12: Chemical layer 13: Drug layer 14: Iridium layer (supporting part) 100: Iridium-coated titanium electrode 2: Electrode precursor 3:Second precursor 4:Third precursor

Claims

1. a chemical solution application step of applying a chemical solution containing iridium to an electrode precursor in which a substrate formed of titanium or a titanium alloy is coated with platinum; the chemical solution contains an iridium organic acid complex as iridium, The method for producing an iridium-coated titanium electrode, wherein the organic acid complex of iridium does not contain chlorine.

2. 2. The method for producing an iridium-coated titanium electrode according to claim 1, wherein the organic acid complex of iridium is an organometallic complex of iridium having a carboxylic acid group.

3. 2. The method for producing an iridium-coated titanium electrode according to claim 1, wherein the organic acid complex of iridium is iridium diethylhexanoate.

4. 4. The method for manufacturing an electrode according to claim 1, wherein the solvent of the chemical solution is 2-propanol.

5. The method for manufacturing an electrode according to claim 1 , further comprising a firing step of firing the electrode precursor to which the chemical solution is attached.

6. The method for producing an electrode according to claim 5 , wherein iridium is supported on the surface of the electrode precursor by the firing step.

7. The amount of iridium supported on the electrode precursor was set to 2.0 g / m in terms of iridium oxide relative to the surface of the substrate. ２ 20.0g / m or more ２ The method for manufacturing an electrode according to claim 6, wherein:

Images