Method for manufacturing electrode and method for manufacturing electrode precursor

Abstract

To provide a method for manufacturing an electrode using an aggregate of fibers formed of titanium or a titanium alloy, in which the risk of ignition is suppressed, and a method for manufacturing an electrode precursor.SOLUTION: A method for manufacturing an electrode includes a base layer forming step of forming a base layer made of a noble metal element on a fiber surface of a fiber body which is an aggregate of fibers formed of titanium or a titanium alloy by plating, and a supporting step of supporting a metal element different from the noble metal element on the base layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrode and a method for manufacturing an electrode precursor. [Background technology]

[0002] Patent Document 1 discloses a porous body, an electrochemical cell, and a method for manufacturing the porous body. The porous body includes a porous conductive substrate having interconnected pores and a skeleton forming the pores, and a metal coating provided on a portion of the surface of the skeleton. The porous conductive substrate may be made of Ti or a Ti alloy. The skeleton of the porous conductive substrate may have the shape of a fiber assembly (hereinafter referred to as a fibrous body), an agglomerate of granular material, a laminate of multiple meshes, a membrane with through-holes, or an assembly thereof. As the fibrous body, a sintered fiber body is preferably used, and a sintered nonwoven fabric is more preferably used. When the porous conductive substrate is a fibrous body, the thickness of the fibers constituting the fibrous body is preferably 10 μm or more and 100 μm or less. As the agglomerate of granular material, a sintered granular material body is preferably used.

[0003] Patent Document 2 discloses an electrode for chlorine generation. This electrode comprises an electrode substrate made of titanium or a titanium alloy, on which an electrocatalytic layer is provided via an intermediate layer. The electrocatalytic layer of this electrode is composed of, in metal equivalent, 3 mol % to 10 mol % of iridium oxide, 20 mol % to less than 35 mol % of tantalum oxide, and 55 mol % to 77 mol % of platinum. The intermediate layer of this electrode is said to be a porous platinum coating layer. The intermediate layer is also said to be composed of platinum dispersed and coated at a coverage of 10 to 80% to the extent that the substrate surface is partially exposed, and a mixed metal oxide of 3 to 30 mol % of iridium oxide and 70 to 97 mol % of tantalum oxide that covers at least the exposed portion of the substrate surface. In this case, the intermediate layer is formed by forming dispersed platinum and then providing a mixed metal oxide of iridium oxide and tantalum oxide on the platinum. Before forming the intermediate layer, the electrode substrate of this electrode has a thin layer of titanium hydride formed on the surface of the substrate.

[0004] Patent Document 3 discloses a power supply element that is interposed between a solid electrolyte membrane and an electrode plate of an electrolysis cell and is pressed against the electrode plate. This power supply element is used in an electrolysis cell that performs water electrolysis. This power supply element includes an unsintered fiber layer that is in contact with the plate. This fiber layer is preferably made of titanium fiber. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 179693 [Patent Document 2] Japanese Patent Application Publication No. 2019-119930 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-315933 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, fiber aggregates (fibrous bodies) made of titanium or titanium alloys are sometimes used as substrates for electrodes for water electrolysis and other applications. However, such fibrous bodies may ignite (including unintentional ignition or catching fire) when handled in an oxygen-containing atmosphere, such as the air. Therefore, when manufacturing electrodes using such fibrous bodies, managing the manufacturing process can be cumbersome. Therefore, it is desirable to reduce the risk of ignition in manufacturing methods for electrodes or electrode precursors that use fibrous aggregates made of titanium or titanium alloys.

[0007] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a method for manufacturing an electrode and an electrode precursor using an aggregate of fibers formed from titanium or a titanium alloy, which reduces the risk of fire. [Means for solving the problem]

[0008] In order to achieve the above object, the method for manufacturing an electrode according to the present disclosure includes: a base layer forming step of plating a base layer made of a precious metal element on the surface of the fiber body, which is an aggregate of fibers made of titanium or a titanium alloy; and a supporting step of supporting a metal element other than the noble metal element on the underlayer.

[0009] In order to achieve the above object, the method for manufacturing an electrode according to the present disclosure includes: a base layer forming step of plating a base layer made of platinum on the fiber surface of a fibrous body which is an aggregate of fibers formed of titanium or a titanium alloy; and a supporting step of supporting iridium on the underlayer.

[0010] To achieve the above object, the method for producing an electrode precursor according to the present disclosure includes: The method includes a base layer forming step of plating a base layer made of a first platinum group element on the fiber surface of a fibrous body, which is an aggregate of fibers made of titanium or a titanium alloy. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a method for manufacturing an electrode and a method for manufacturing an electrode precursor using an aggregate of fibers formed of titanium or a titanium alloy, with reduced risk of fire. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram of a fibrous body. [Figure 2] FIG. 2 is a schematic diagram of the internal structure of a fibrous body on which a base layer is formed. [Figure 3] FIG. 2 is a schematic diagram of a first precursor. [Figure 4] 1A and 1B are schematic diagrams illustrating an example of an electrode manufactured by a method for manufacturing an electrode according to an embodiment of the present invention. [Figure 5] 1A and 1B are schematic diagrams illustrating an example of an electrode manufactured by a method for manufacturing an electrode according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a method for manufacturing an electrode and a method for manufacturing an electrode precursor according to an embodiment of the present disclosure will be described.

[0014] The method for manufacturing an electrode according to this embodiment includes a base layer forming step of plating a base layer made of a precious metal element on the fiber surface of a fibrous body, which is an aggregate of fibers made of titanium or a titanium alloy, and a supporting step of supporting a metal element other than the precious metal element on the base layer.

[0015] The method for manufacturing an electrode precursor according to this embodiment includes a base layer forming step of plating a base layer made of a precious metal onto the fiber surface of a fibrous body, which is an aggregate of fibers made of titanium or a titanium alloy.

[0016] According to the electrode manufacturing method of this embodiment and the electrode precursor manufacturing method of this embodiment, in the electrode manufacturing method using an aggregate of fibers (hereinafter referred to as a fibrous body) formed of titanium or a titanium alloy, it is possible to suppress ignition of the fibrous body during the manufacturing process.

[0017] The electrode manufactured by the electrode manufacturing method according to the present embodiment can be suitably used as a so-called insoluble electrode, for example, as an electrode for water electrolysis.

[0018] The method for producing an electrode and a method for producing an electrode precursor according to this embodiment will be described in detail below.

[0019] The base layer forming step is a step of forming a base layer on the fiber surface of the fibrous body by plating. Hereinafter, the fibrous body on which the base layer is formed may be referred to as a first precursor. The first precursor is included in the electrode precursor according to this embodiment.

[0020] The fibrous body is a substrate of the electrode. As described above, the fibrous body is an assembly of fibers made of titanium or a titanium alloy. The fibrous body may be, for example, a sintered body obtained by forming an assembly of fibers made of titanium or a titanium alloy into a plate shape and sintering the plate.

[0021] The diameter of the fibers forming the fibrous body is, for example, 5 μm or more and 70 μm or less, and preferably 10 μm or more and 60 μm or less.

[0022] When the fibrous body is a sintered body, the porosity thereof may be 40% or more and 90% or less, and preferably 45% or more and 85% or less.

[0023] When the fibrous body is formed into a plate shape, the plate thickness may be, for example, 0.1 mm or more and 5.0 mm or less, and preferably 0.1 mm or more and 2.0 mm or less.

[0024] The base layer is a layer that covers the surface of the fibers of the fibrous body. The base layer is a metal layer that is substantially made of a noble metal element (noble metal). In this embodiment, the noble metal element (noble metal) refers to gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), or iridium (Ir).

[0025] The underlayer is preferably a metal layer made of a platinum group element including at least one of ruthenium, rhodium, palladium, osmium, iridium, and platinum, or a metal layer made of gold. The underlayer may be, for example, a layer made of platinum. The underlayer may also be a layer made of an alloy containing two or more platinum group elements. The underlayer may also be a layer made of an alloy of a platinum group element and gold. In particular, when the electrode is used for water electrolysis, the underlayer is preferably made of platinum or gold.

[0026] By forming the base layer, the surface of the fibers of the fibrous body is coated, making the fibrous body less likely to catch fire. In other words, the formation of the base layer suppresses the fibrous body from catching fire.

[0027] The undercoat layer is preferably not a porous film or layer, but rather one that covers the entire surface of the fibrous body.

[0028] The underlayer is formed by plating, such as electrolytic plating or electroless plating. By forming the underlayer by plating, the entire surface of the fiber body can be covered, which can better prevent the fiber body from catching fire.

[0029] The thickness of the underlayer is preferably 0.2 μm or more. If the thickness of the underlayer is 0.2 μm or more and 1.0 μm or less, it is sufficient to suppress the ignition of the fibrous body.

[0030] If the underlayer is formed by plating so that the thickness of the underlayer is 0.2 μm or more, the entire surface of the fibrous body can be sufficiently covered, that is, densely enough to prevent ignition.

[0031] The supporting step is a step of supporting, on the underlayer, a metal element other than the noble metal element forming the underlayer.

[0032] For example, when the underlayer is a layer made of a platinum group element (first platinum group element), the supporting step is a step of supporting, on the underlayer, a metal element other than the first platinum group element that forms the underlayer. An example of this other metal element is a second platinum group element other than the first platinum group element. Note that the second platinum group element being other than the first platinum group element means that the second platinum group element is an element different from the first platinum group element.

[0033] For example, when the underlayer is a layer made of gold, the supporting step may be a step of supporting a platinum group element on the underlayer.

[0034] Hereinafter, a portion supported on the underlayer and containing a metal element (for example, a second platinum group element) different from the noble metal element forming the underlayer may be referred to as a supported portion.

[0035] The support is preferably a moiety that may include at least one of the platinum group elements, ie, ruthenium, rhodium, palladium, osmium, iridium, and platinum.

[0036] The support portion is a portion that functions as a catalyst when the electrode according to this embodiment is used as an electrode for water electrolysis or the like.

[0037] The support may be formed of an alloy containing two or more platinum group elements. When the underlayer is platinum, the support contains at least one of ruthenium, rhodium, palladium, osmium, and iridium. When the underlayer is platinum, the support preferably contains iridium. When the underlayer is made of a platinum-containing metal element other than platinum, the support may contain platinum.

[0038] The support may contain an element other than a platinum group element (e.g., tantalum). The support may be, for example, an alloy of a platinum group element and a metal element other than a platinum group element. When the support contains an element other than a platinum group element, the element is preferably a metal element.

[0039] The support portion may be formed on the base layer in the form of a dense layer, or may be formed on the base layer in the form of islands (scattered), or in the form of a porous layer (with defects, i.e., many holes). The support portion may be formed from the base layer of a certain fiber to the base layer of an adjacent fiber, i.e., in a state where the fibers are bridged. In other words, the support portion may be disposed at least on the first precursor.

[0040] The support portions do not necessarily need to be dispersed over the entire surface of the base layer. For example, when the fibrous body is a sintered body formed into a plate shape, more support portions may be segregated near the surface of the plate. In other words, the support portions may be densely distributed near the surface of the plate, and sparsely distributed inside the plate.

[0041] The support portion can be formed, for example, by applying a chemical solution containing a second platinum group element to a fibrous body on which a base layer is formed. Hereinafter, the process of applying a chemical solution containing a second platinum group element to a fibrous body on which a base layer is formed may be referred to as an application process. Hereinafter, a fibrous body on which a base layer is formed (including the electrode according to this embodiment) and further supported with a chemical solution may be referred to as a second precursor. 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.

[0042] The chemical solution attached to the fibrous body can be converted into a support, for example, by a calcination step in which the second precursor is calcined as needed. That is, the electrode according to this embodiment can be obtained from the second precursor by this calcination. When calcining the second precursor, the second precursor may be dried to form a third precursor, which is then calcined.

[0043] When the calcination step is carried out, the second precursor may be calcined 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 containing a metal consisting of a platinum group element.

[0044] The firing temperature in the firing step is preferably less than 700° C., and more preferably not more than 600° C. If the firing temperature is less than 700° C., it is possible to avoid thermal deterioration of the titanium in the fibrous body.

[0045] As described above, when the underlayer is platinum, the support preferably contains iridium. When the support contains iridium, an example of a component contained in the chemical solution (chemical solution containing iridium as a second platinum group element) to be applied to the fibrous body can be, for example, an iridium chloride salt such as sodium iridium chloride. In this case, since the thermal decomposition temperature of iridium chloride is in the upper 300°C range, the firing temperature is preferably 400°C or higher. Furthermore, the firing time is preferably 20 minutes or longer.

[0046] Furthermore, when the support contains iridium, the calcination temperature in the calcination step is preferably less than 700° C., more preferably not more than 600° C. If the calcination temperature is less than 700° C., excessive growth of iridium crystals during calcination can be suppressed, and a decrease in catalytic performance due to iridium can be avoided.

[0047] Methods for applying a chemical solution containing a second platinum group element to a fibrous body on which a base layer has been formed include a method of applying the chemical solution to the fibrous body (hereinafter referred to as the application method) and a method of immersing the fibrous body in the chemical solution.

[0048] Examples of application methods include applying the chemical solution to the outer surface of the fibrous body with a brush or application roller, spraying the chemical solution onto the outer surface of the fibrous body, and transferring the chemical solution to the outer surface of the fibrous body from a carrier holding the chemical solution.

[0049] In the supporting step, the amount of the supported portion may be adjusted by alternately repeating the adhesion step and the firing step. That is, in the supporting step, the amount of the supported portion can be increased by alternately repeating the adhesion step and the firing step. That is, by further repeating the adhesion step and the firing step for the electrode according to this embodiment, the amount of the supported portion in the electrode can be increased.

[0050] A specific example of the method for manufacturing an electrode according to this embodiment will be described below.

[0051] FIG. 1 shows a fibrous body 1, which is an assembly of fibers made of titanium or a titanium alloy and formed as a plate-like sintered body. In the electrode manufacturing method according to this embodiment, a base layer 20 of, for example, platinum is formed on the surface of the fibers 10 made of titanium or a titanium alloy of the fibrous body 1 by, for example, plating, as shown in FIG. 2. In FIGS. 2 and 3, the fibrous body 1 on which the base layer 20 (see FIG. 2) is formed is shown as a first precursor 2. FIG. 2 is a schematic diagram of the internal structure of the first precursor 2, showing an enlarged portion of the first precursor 2. In the first precursor 2, it is preferable that the entire surface of the fibers 10 of the fibrous body 1 is covered with the base layer 20.

[0052] In the method for producing an electrode according to this embodiment, the support portion is formed on the first precursor 2 by coating or immersion.

[0053] For example, when a chemical solution containing iridium is applied to the first precursor 2, and the second precursor in which the chemical solution adheres only to the vicinity of the surface of the plate surface of the first precursor 2 is then fired, an electrode 100 can be formed in which a support region 3 containing a support portion made of iridium is segregated near the surface of the plate surface of the first precursor 2, as shown in FIG. 4.

[0054] Furthermore, for example, when a chemical solution containing iridium is applied to the first precursor 2, the chemical solution is allowed to penetrate into the first precursor 2, and the second precursor having the chemical solution attached to the first precursor 2 is then fired, or when the first precursor 2 is immersed in a chemical solution containing iridium, the chemical solution is allowed to penetrate into the first precursor 2, and the second precursor having the chemical solution attached to the first precursor 2 is then fired, an electrode 200 can be formed in which a support region 3 having a support portion made of iridium present is formed over the entire first precursor 2, as shown in FIG. 5. [Example]

[0055] The method for manufacturing an electrode according to this embodiment will be described below based on examples.

[0056] Example 1 As the fibrous material, a titanium (Ti) fiber sintered body (100 mm x 100 mm, thickness 0.2 mm, porosity 55.7%, average fiber diameter 20 μm, manufactured by Bekaert Toko Metal Fiber Co., Ltd.) was used.

[0057] First, the fiber was subjected to ultrasonic degreasing to degrease the surface of the titanium fiber. The ultrasonic degreasing was performed using Aiwa Medical Industry's AU-710CO-10 (ultrasonic frequency: 28 kHz). The ultrasonic degreasing treatment lasted for 1 minute.

[0058] After ultrasonic degreasing, the fiber was subjected to electrolytic degreasing to degrease the titanium fiber surface. The electrolytic degreasing was performed using Etrex 12 manufactured by EEJA Co., Ltd. The voltage applied during the electrolytic degreasing was 8.0 V. The treatment time for the electrolytic degreasing was 1 minute.

[0059] After the electrolytic degreasing treatment, the fiber was immersed in a mixed aqueous solution of 2 wt% ammonium hydrogen fluoride and 2 wt% hydrochloric acid for approximately 10 seconds to perform an oxide film removal treatment to remove the oxide film from the fiber.

[0060] After the oxide film removal treatment, the fiber was immersed in a 2 wt% aqueous solution of ammonium hydrogen fluoride and held there for approximately 60 seconds, thereby performing a surface roughening treatment to roughen the titanium fiber surface of the fiber.

[0061] Next, the surface of the fiber body after the surface roughening treatment was subjected to a plating treatment in which platinum (Pt) was plated.

[0062] The plating solution contained 5 wt % platinum and 100 g of sulfuric acid per 1 L of the plating solution. The pH of the plating solution was 1.

[0063] The plating treatment was electrolytic plating. A Pt / Ti plate electrode was placed as the anode in the plating solution (60°C), and the fiber was placed as the cathode. The plating was conducted at a current of 0.5 A / dm 2 A constant current was applied to the anode and cathode to plate the surface of the fiber with platinum, forming a 0.2 μm thick platinum underlayer (platinum layer) to form the first precursor. The time for which the constant current was applied (plating time) was 10 minutes.

[0064] Next, iridium was supported on the first precursor by firing to obtain an electrode as follows: First, a chemical solution containing iridium (Ir) was applied to the plate surface of the first precursor as follows (adhesion step).

[0065] The formulation of the chemical solution applied to the plate surface of the first precursor was as follows: The solvent for the chemical solution was special-grade isopropyl alcohol (2-propanol, Grade 1, manufactured by Kanto Chemical Co., Ltd.). Sodium chloroiridate crystals (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.

[0066] Then, this chemical solution was applied once to the plate surface of the first precursor using a brush, and the chemical solution was attached to the plate surface of the first precursor to obtain a second precursor. This second precursor was further dried in the atmosphere to evaporate the solvent of the attached chemical solution, and a third precursor was obtained as the second precursor. This drying process was carried out in a dryer tank through which hot air at 180°C was passed. The processing time of the drying process (the time held in the tank) was 20 minutes. The drying process was carried out in a batch process.

[0067] The third precursor was further calcined in the atmosphere to produce an electrode. Calcination was carried out by placing the second precursor in a calcination furnace adjusted to 500°C and holding it there for 45 minutes. The first precursor, second precursor, third precursor, and electrode did not ignite before, during, or after calcination.

[0068] (Examples 2 and 3) Examples 2 and 3 differ from Example 1 in that the plating time was extended to increase the thickness of the platinum underlayer, but otherwise the same procedures were followed as in Example 1 to obtain a first precursor, a second precursor, a third precursor, and an electrode. In Examples 2 and 3, the thicknesses of the platinum underlayer on the first precursor were set to 1.0 μm and 1.5 μm, respectively. In both Examples 2 and 3, the first precursor, the second precursor, the third precursor, and the electrodes did not ignite before, during, or after firing.

[0069] (Comparative Example 1) Comparative Example 1 differs from Example 1 in that the electrolytic degreasing treatment, oxide film removal treatment, surface roughening treatment, and plating treatment were omitted, but otherwise the same procedures were carried out as in Example 1, in which a chemical solution was applied to the fibrous body to obtain a dried third precursor equivalent and an electrode obtained by firing the third precursor equivalent. In the case of this comparative example, the third precursor equivalent and the electrode did not ignite before, during, or after firing.

[0070] (Comparative Example 2) Comparative Example 2 differs from Comparative Example 1 in that the applied chemical solution was changed to one containing platinum in addition to iridium, but otherwise a third precursor equivalent and an electrode obtained by firing the third precursor equivalent were obtained in the same manner as Comparative Example 1. In the case of this comparative example as well, the third precursor equivalent and the electrode did not ignite before, during, or after firing.

[0071] In Comparative Example 2, the formulation of the chemical solution was as follows: The solvent for the chemical solution was the same as that used in Example 1. Then, the same sodium chloroiridate crystals as used in Example 1, the same tantalum butoxide as used in Example 1, and chloroplatinic acid crystals (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) were dissolved in this solvent so that the concentrations of iridium, tantalum, and platinum in the solvent were 1.75 wt%, 1.5 wt%, and 1.75 wt%, respectively, to prepare the chemical solution for application according to Comparative Example 2.

[0072] Example 4 In Example 4, the first precursor in Example 1 was used as an electrode precursor.

[0073] (Comparative Example 3) Comparative Example 3 differs from Example 4 in that instead of plating, platinum was supported on the fiber surface of the fibrous body in the following manner, but otherwise an electrode precursor was produced in the same manner as in Example 4.

[0074] Platinum was supported on the fiber surface of the fibrous body by coating and baking. First, a chemical solution containing platinum was applied to the plate surface of the fibrous body after the surface roughening treatment as follows.

[0075] The formulation of the chemical solution applied to the plate surface of the fibrous body after the surface roughening treatment is as follows: The solvent for the chemical solution was special-grade isopropyl alcohol (2-propanol, Grade 1, manufactured by Kanto Chemical Co., Ltd.). Chloroplatinic acid crystals (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 platinum concentration and tantalum concentration in the solvent were 3.5 wt% and 1.5 wt%, respectively, to prepare the chemical solution for application.

[0076] Then, this chemical solution was applied once to the roughened surface of the fibrous body using a brush, and the chemical solution was adhered to the surface of the fibrous body. The fibrous body with this chemical solution adhered (coated material) was then dried in the atmosphere to evaporate the solvent of the adhered chemical solution. This drying process was carried out in a dryer tank through which hot air at 180°C was circulated. The drying process time (time held in the tank) was 20 minutes. The drying process was carried out in a batch process.

[0077] The dried coated material was further calcined in the atmosphere to produce an electrode precursor (equivalent to a first precursor). The calcination was carried out by placing the dried coated material in a calcination furnace adjusted to 500°C and holding it there for 45 minutes. Before, during, and after calcination, the coated material, the dried coated material, and the electrode precursor did not ignite.

[0078] Example 5 Example 5 differs from Example 4 in that, when forming the first precursor, the oxide film removal treatment and the surface roughening treatment were changed, acid washing was added, and gold was plated instead of platinum in the plating treatment. Otherwise, the first precursor was produced as an electrode precursor in the same manner as Example 4.

[0079] After the electrolytic degreasing treatment, the fiber was immersed in a 10 wt % aqueous solution of ammonium hydrogen fluoride and held there for approximately 10 seconds to perform an oxide film removal treatment to remove the oxide film from the fiber.

[0080] After the oxide film removal treatment, the fiber was immersed in sulfuric acid with a concentration of 9.6 M and held there for approximately 3 minutes, thereby performing a surface roughening treatment to roughen the titanium fiber surface of the fiber.

[0081] After the surface roughening treatment, the fiber was immersed in 10 wt % sulfuric acid and held there for about 30 seconds to wash the titanium fiber surface of the fiber, thereby performing acid washing.

[0082] The following three commercially available plating solutions for gold plating were used: PreciousFab Au-ST300 (manufactured by EEJA Corporation) was used as the first solution; PreciousFab Au-ST100 (manufactured by EEJA Corporation) was used as the second solution; and PreciousFab Au401 (manufactured by EEJA Corporation) was used as the third solution.

[0083] The plating treatment was electrolytic plating, in which a Pt / Ti plate electrode was placed as an anode in a plating solution (60°C), and the fiber was placed as a cathode.

[0084] First, a first gold strike plating was performed using a plating solution as the first solution, by applying a voltage of 6 V and passing a current between the anode and the cathode for 30 seconds.

[0085] Next, the plating solution was replaced with a second solution, and a voltage of 6 V was applied to pass a current between the anode and the cathode for 20 seconds, thereby performing a second gold strike plating.

[0086] Finally, the plating solution was replaced with the third solution and the plating was conducted for 9 minutes at 0.3 A / dm 2 A constant current was passed between the anode and cathode to plate gold on the fiber surface of the fibrous body, and a gold underlayer (gold layer) with a final thickness of 1.0 μm was formed to form a first precursor.

[0087] The electrodes of Examples 1-3 and Comparative Examples 1 and 2, and the electrode precursors of Examples 4 and 5 and Comparative Example 3 were further subjected to ignition tests to evaluate their susceptibility to ignition.

[0088] In the ignition test, each electrode or electrode precursor was heated with a lighter flame for 10 seconds, and if the electrode or electrode precursor did not ignite, it was judged as passed, and if the electrode or electrode precursor ignited, it was judged as failed. As a reference example, when the untreated fibrous body used in Example 1 was subjected to the ignition test, it immediately ignited and burned violently.

[0089] As a result, the electrodes according to Examples 1 to 3 and the electrode precursors according to Examples 4 and 5 all passed the test. The electrodes according to Comparative Examples 1 and 2 and the electrode precursor according to Comparative Example 3 all failed the test. From these results, it can be determined that the electrode precursors (first precursor, second precursor, and third precursor) and electrodes according to the examples have a reduced risk of ignition. In other words, it was evaluated that the electrode manufacturing method and electrode precursor manufacturing method according to the present embodiment can suppress ignition of the fibrous body during the manufacturing process in a method for manufacturing an electrode or electrode precursor using an aggregate of fibers (fibrous body) made of titanium or a titanium alloy.

[0090] In the electrode manufacturing method and electrode precursor manufacturing method according to this embodiment, it is believed that by covering the surface of the fibers of the fibrous body with a platinum group element such as platinum that is difficult to burn (ignite, catch fire, or ignite), or a metal group element such as gold that is difficult to burn, contact between the fibers and oxygen is inhibited, thereby suppressing the ignition of the fibrous body.

[0091] In Example 1-4, the case where the base layer was a platinum layer was evaluated. However, if the base layer is a layer that sufficiently covers the entire surface of the fibrous body, such as formed by a plating process, it is considered that even if the base layer is a metal layer made of a platinum group element other than platinum, it can suppress the ignition of the fibrous body during the manufacturing process of an electrode or electrode precursor, as in Example 1-4 above.

[0092] As described above, it is possible to provide a method for manufacturing an electrode and a method for manufacturing an electrode precursor using an aggregate of fibers formed of titanium or a titanium alloy, with reduced risk of ignition.

[0093] 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]

[0094] The present disclosure is applicable to methods for manufacturing electrodes and methods for manufacturing electrode precursors. [Explanation of symbols]

[0095] 1: Fibrous body 10: Fiber 100: Electrode 200: Electrode 2 :First precursor 20: Base layer 3: Supporting area

Claims

1. a base layer forming step of plating a base layer made of a precious metal element on the fiber surface of a fibrous body which is an aggregate of fibers made of titanium or a titanium alloy; and supporting a metal element other than the noble metal element on the underlayer.

2. 2. The method for producing an electrode according to claim 1, wherein the noble metal element is a first platinum group element.

3. 3. The method for producing an electrode according to claim 2, wherein the metal element is a second platinum group element different from the first platinum group element.

4. The method for manufacturing an electrode according to claim 3 , wherein in the supporting step, a chemical solution containing the second platinum group element is applied to the fibrous body on which the underlayer is formed.

5. The method for manufacturing an electrode according to claim 4 , wherein in the supporting step, a chemical solution containing the second platinum group element is applied to the fibrous body on which the underlayer is formed.

6. The method for manufacturing an electrode according to claim 4, wherein the underlayer has a thickness of 0.2 μm or more.

7. The supporting step further includes a firing step of firing the fibrous body to which the chemical solution is attached, The method for producing an electrode according to claim 6, wherein the firing step involves firing in an atmosphere at 400°C or higher and lower than 700°C for 20 minutes or longer and 80 minutes or shorter.

8. the first platinum group element is platinum; The method for producing an electrode according to claim 3 , wherein the second platinum group element is iridium.

9. 2. The method for manufacturing an electrode according to claim 1, wherein the noble metal element is gold.

10. a base layer forming step of plating a base layer made of platinum on the fiber surface of a fibrous body which is an aggregate of fibers formed of titanium or a titanium alloy; and supporting iridium on the underlayer.

11. A method for manufacturing an electrode precursor, comprising a base layer forming step of plating a base layer made of a precious metal element onto the surface of a fibrous body, which is an aggregate of fibers made of titanium or a titanium alloy.

12. The method for producing an electrode precursor according to claim 11, wherein the noble metal element is a first platinum group element.

13. The method for producing an electrode precursor according to claim 11, wherein the noble metal element is gold.

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