Method for manufacturing an electrode for electrolysis

Abstract

The present invention relates to a method for manufacturing an electrode for electrolysis, which uses both urea and octadecylamine in a coating composition to improve the durability and performance of the manufactured electrode for electrolysis.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0159200 filed in the Korean Intellectual Property Office on November 24, 2020, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0004] The present invention relates to a method for producing an electrode for electrolysis that exhibits low overvoltage performance and has excellent durability. Background Art

[0005] The technology for producing hydroxide, hydrogen, and chlorine by electrolyzing low-cost brine, such as seawater, is well known. This electrolysis process, also known as the chlor-alkali process, has been proven in commercial operation for decades, with its performance and reliability.

[0006] As a method for electrolyzing brine, the most widely used at present is an ion exchange membrane method, in which an ion exchange membrane is installed inside an electrolytic cell to divide the electrolytic cell into a cation chamber and an anion chamber, and brine is used as an electrolyte to obtain chlorine gas from the anode and hydrogen gas and caustic soda from the cathode.

[0007] Meanwhile, the electrolysis process of the brine is achieved through the reaction shown in the following electrochemical reaction formula.

[0008] Reaction at the anode: 2Cl - →Cl2+2e - (E 0 = +1.36V)

[0009] Reaction at the cathode: 2H2O + 2e - →2OH - +H2(E 0 =-0.83V)

[0010] Overall reaction: 2Cl - +2H2O-→2OH - +Cl2+H2(E 0 =-2.19V)

[0011] When performing brine electrolysis, the electrolysis voltage must be determined by considering the theoretically required voltage for brine electrolysis, the overvoltage of the anode, the overvoltage of the cathode, the voltage caused by the resistance of the ion exchange membrane, and the voltage caused by the distance between the anode and cathode. Among these voltages, the overvoltage of the electrode serves as an important variable.

[0012] Therefore, methods capable of reducing overvoltage of electrodes have been studied, and specifically, research has been actively conducted on how to construct components of electrode coatings, and what coating compositions are used and under what conditions the coatings are formed during the manufacturing process of electrodes to produce excellent electrodes.

[0013] Prior art literature

[0014] (Patent Document 1) JP2003-277967A Summary of the Invention

[0015] Technical issues

[0016] One aspect of the present invention provides a method for manufacturing an electrode for electrolysis, which is capable of improving the durability and overvoltage performance of a finally manufactured electrode for electrolysis by optimizing the type and proportion of a stabilizer used in a coating composition for forming a coating layer.

[0017] Technical Solution

[0018] According to one aspect of the present invention, a method for manufacturing an electrode for electrolysis is provided.

[0019] (1) The present invention provides a method for manufacturing an electrode for electrolysis, the method comprising: applying a coating composition on at least one surface of a metal substrate; and drying and heat-treating the metal substrate coated with the coating composition to form a coating, wherein the coating composition comprises a ruthenium precursor and a stabilizer, wherein the stabilizer comprises urea and octadecylamine.

[0020] (2) In the above (1), the present invention provides a method for producing an electrode for electrolysis, wherein urea and octadecylamine are contained in a molar ratio of 90:10 to 10:90.

[0021] (3) In the above (1) or (2), the present invention provides a method for producing an electrode for electrolysis, wherein urea and octadecylamine are contained in a molar ratio of 80:20 to 60:40.

[0022] (4) In any one of the above (1) to (3), the present invention provides a method for producing an electrode for electrolysis, wherein the ruthenium precursor and the stabilizer are contained in a molar ratio of 100:20 to 100:40.

[0023] (5) In any one of (1) to (4) above, the present invention provides a method for producing an electrode for electrolysis, wherein the coating composition further contains a cerium precursor.

[0024] (6) In any one of (1) to (5) above, the present invention provides a method for producing an electrode for electrolysis, wherein the coating composition further contains a platinum precursor.

[0025] (7) In any one of (1) to (6) above, the present invention provides a method for producing an electrode for electrolysis, wherein the solvent of the coating composition is a mixture of isopropyl alcohol and 2-butoxyethanol.

[0026] (8) In any one of the above (1) to (7), the present invention provides a method for manufacturing an electrode for electrolysis, wherein coating, drying and heat treatment are repeated so that the content of ruthenium oxide per unit area of ​​the electrode for electrolysis is 7 g / m 2 above.

[0027] (9) In any one of the above (1) to (8), the present invention provides a method for producing an electrode for electrolysis, wherein the drying is performed at 50° C. to 300° C. for 5 minutes to 60 minutes.

[0028] (10) In any one of the above (1) to (9), the present invention provides a method for manufacturing an electrode for electrolysis, wherein the heat treatment is performed at 400° C. to 600° C. for 1 hour or less.

[0029] Beneficial effects

[0030] The electrode for electrolysis produced by the production method of the present invention can exhibit low overvoltage and excellent durability. DETAILED DESCRIPTION

[0031] Hereinafter, the present invention will be described in more detail.

[0032] It should be understood that the words or terms used in this specification and claims of the present invention should not be construed as limited to having the meanings defined in commonly used dictionaries. It should also be understood that the words or terms should be understood to have meanings consistent with their meanings in the context of the relevant art and the technical concept of the present invention, based on the principle that the inventor can appropriately define the meaning of the words or terms to best illustrate the invention.

[0033] Method for manufacturing an electrode for electrolysis

[0034] Research into reducing the overvoltage of electrodes during electrolysis has been ongoing, and as part of this effort, research into methods for stably forming coatings by adding various components to coating compositions used to form the coatings is actively underway. As a typical example, it is known that when a compound having an amino group is added to a coating composition, the structure of the coating to be formed can be optimized to improve the performance of the resulting electrolytic electrode. However, even when a compound having an amino group is used, the method used in the manufacturing process or the performance of the resulting electrolytic electrode can vary depending on the specific chemical structure or specific physical / chemical properties of the compound.

[0035] Therefore, the inventors of the present invention conducted research to develop a coating composition additive that can maximize the performance of an electrode to be manufactured in terms of overvoltage performance and durability of the electrode, and arrived at the present invention as a result of the research.

[0036] Specifically, the present invention provides a method for manufacturing an electrode for electrolysis, the method comprising: applying a coating composition on at least one surface of a metal substrate; and drying and heat-treating the metal substrate coated with the coating composition to form a coating, wherein the coating composition comprises a ruthenium precursor and a stabilizer, wherein the stabilizer comprises urea and octadecylamine.

[0037] In the method for manufacturing an electrolytic electrode of the present invention, the metal substrate to which the coating composition is applied may be nickel, titanium, tantalum, aluminum, hafnium, zirconium, molybdenum, tungsten, stainless steel, or alloys thereof, with nickel being preferred. Furthermore, the metal substrate may be in the form of a mesh or expanded metal. When a metal substrate meeting the above conditions is used, the resulting electrolytic electrode can have excellent durability and electrolytic performance.

[0038] In the method for manufacturing an electrode for electrolysis of the present invention, the coating composition for forming a coating comprises a ruthenium precursor and a stabilizer. The ruthenium precursor is used to form the ruthenium oxide in the coating and can be a hydrate, hydroxide, halide or oxide of ruthenium, and can be, specifically, selected from ruthenium hexafluoride (RuF6), ruthenium (III) chloride (RuCl3), ruthenium (III) chloride hydrate (RuCl3 xH2O), ruthenium (III) bromide (RuBr3), ruthenium (III) bromide hydrate (RuBr3 xH2O), ruthenium iodide (RuI3) and one or more of ruthenium acetate. When using any of the ruthenium precursors listed above, ruthenium oxide can be easily formed.

[0039] The stabilizer is used to impart strong adhesion between the coating to be formed and the metal substrate, and contains urea and octadecylamine. Using these two components as stabilizers significantly improves the coupling between the ruthenium element contained in the coating, and by controlling the oxidation state of the ruthenium-containing particles, it is possible to manufacture an electrode in a form more suitable for electrolytic reactions.

[0040] Meanwhile, the molar ratio of urea to octadecylamine contained in the stabilizer may be 90:10 to 10:90, 80:20 to 20:80, 80:20 to 30:70, or 80:20 to 60:40, more preferably 80:20 to 60:40. When the molar ratio of urea to octadecylamine is within the above range, the combined use of urea and octadecylamine can maximize the effect of improving performance and durability.

[0041] In the method for manufacturing an electrolytic electrode of the present invention, the coating composition may contain a ruthenium precursor and a stabilizer in a molar ratio of 100:20 to 100:40, preferably 100:25 to 100:35. When the composition ratio of the ruthenium precursor to the stabilizer is within the above range, the effect of controlling the oxidation state of the ruthenium element by the stabilizer can be excellent.

[0042] In the method for manufacturing an electrolytic electrode according to the present invention, the coating composition may further include a cerium precursor. The cerium precursor contained in the coating composition is then converted into cerium oxide. The resulting cerium oxide improves the durability of the electrolytic electrode, thereby minimizing the loss of ruthenium, an active material, in the catalyst layer of the electrolytic electrode during activation or electrolysis.

[0043] More specifically, during the activation or electrolysis process of the electrolysis electrode, the particles containing the ruthenium element in the catalyst layer do not change in structure and become a metallic element or are partially hydrated, and are then reduced to an active substance. In addition, the particles containing the cerium element in the catalyst layer change into a needle-like structure and act as a protective material to prevent the physical separation of the particles containing the ruthenium element in the catalyst layer, thereby improving the durability of the electrolysis electrode and preventing the loss of the ruthenium element in the catalyst layer. The cerium oxide includes all types of oxide forms in which the cerium element is combined with an oxygen atom, and can be, specifically, (II), (III) or (IV) oxide.

[0044] The cerium precursor can be used without particular limitation as long as it is a compound capable of forming cerium oxide, and can be, for example, a hydrate, hydroxide, halide, or oxide of elemental cerium, and can be, specifically, one or more cerium precursors selected from cerium (III) nitrate hexahydrate (Ce(NO₃)₃·6H₂O), cerium (IV) sulfate tetrahydrate (Ce(SO₄)₂·4H₂O), and cerium (III) chloride heptahydrate (CeCl₃·7H₂O). When any of the cerium precursors listed above is used, cerium oxide can be easily formed.

[0045] The molar ratio of ruthenium to cerium in the coating composition may be 100:5 to 100:30, preferably 100:10 to 100:20. When the molar ratio of ruthenium to cerium is within the above range, the balance between durability and conductivity of the manufactured electrolysis electrode can be excellent.

[0046] In addition, in the method for manufacturing an electrolytic electrode of the present invention, the coating composition may further include a platinum precursor. The platinum precursor contained in the coating composition can subsequently be converted into platinum oxide, and the platinum element provided by the platinum oxide can serve as an active material together with the ruthenium element. Furthermore, when platinum oxide and ruthenium oxide are included together in the coating, further excellent effects can be exhibited in terms of electrode durability and overvoltage. The platinum oxide includes all types of oxide forms in which the platinum element is combined with an oxygen atom, and can specifically be a dioxide or a tetraoxide.

[0047] The platinum precursor can be used without particular limitation as long as it is a compound capable of forming platinum oxide, and can be, for example, one or more platinum precursors selected from chloroplatinic acid hexahydrate (HPtCl6·6H2O), diamine dinitroplatinum (Pt(NH3)2(NO)2), platinum (IV) chloride (PtCl4), platinum (II) chloride (PtCl2), potassium tetrachloroplatinate (K2PtCl4), and potassium hexachloroplatinate (K2PtCl6). When any of the platinum precursors listed above is used, platinum oxide can be easily formed.

[0048] The molar ratio of the ruthenium element to the platinum element contained in the coating composition may be 100:20 to 100:20, preferably 100:5 to 100:15. When the molar ratio of the ruthenium element to the platinum element is within the above range, it is preferred in terms of improving durability and reducing overvoltage. When the content of the platinum element is lower than the above range, durability and overvoltage may deteriorate. When the content exceeds the above range, it is disadvantageous in terms of economic feasibility.

[0049] In the method for manufacturing an electrolytic electrode of the present invention, an alcoholic solvent can be used as a solvent for the coating composition. When an alcoholic solvent is used, the above-mentioned components can be easily dissolved, and even after the coating composition is applied, the coupling force between the components can be maintained during the coating formation step. Preferably, at least one of isopropyl alcohol and butoxyethanol can be used as the solvent, and more preferably, a mixture of isopropyl alcohol and butoxyethanol can be used. When isopropyl alcohol and butoxyethanol are mixed and used, a more uniform coating can be obtained compared to using either one alone.

[0050] In the manufacturing method of the present invention, a step of pre-treating the metal substrate may be included before the coating step.

[0051] The pretreatment may be chemical etching, sandblasting, or thermal spraying performed on the metal substrate to form irregularities on the surface of the metal substrate.

[0052] The pretreatment can be performed by sandblasting the surface of the metal substrate to form minute irregularities, and then treating the surface with salt or acid. For example, the pretreatment can be performed by sandblasting the surface with aluminum oxide to form irregularities on the surface of the metal substrate, immersing the substrate in an aqueous sulfuric acid solution, and then washing and drying the substrate to form minute irregularities on the surface of the metal substrate.

[0053] The coating may be performed by any method known in the art without particular limitation, as long as the coating composition can be uniformly coated on the metal substrate.

[0054] The coating can be performed by any one method selected from doctor blade, die casting, comma coating, screen printing, spraying, electrostatic spinning, roller coating and brush coating.

[0055] The drying may be performed at 50° C. to 300° C. for 5 to 60 minutes. Preferably, the drying is performed at 50° C. to 200° C. for 5 to 20 minutes.

[0056] When the above conditions are met, the solvent can be sufficiently removed while minimizing energy consumption.

[0057] The heat treatment may be performed at 400° C. to 600° C. for less than 1 hour. Preferably, the heat treatment is performed at 450° C. to 550° C. for 5 minutes to 30 minutes.

[0058] When the above conditions are met, impurities in the catalyst layer can be easily removed without affecting the strength of the metal substrate.

[0059] Meanwhile, the coating may be performed by sequentially repeating coating, drying, and heat treatment so that the amount of the metal substrate per unit area (m 2 ) of ruthenium oxide, the ruthenium oxide is 7g or more, preferably 7.5g or more. That is, the manufacturing method according to another embodiment of the present invention can be carried out as follows: the coating composition is applied to at least one surface of the metal substrate, dried and heat-treated, and then the coating is repeated, wherein the coating composition is applied again, dried and heat-treated on one surface of the metal substrate to which the coating composition was applied for the first time. When the content of ruthenium oxide per unit area is within the above range, sufficient electrolytic performance can be achieved.

[0060] Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples, but the present invention is not limited to these Examples and Experimental Examples. According to the embodiments of the present invention, various other forms can be modified, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

[0061] Material

[0062] In this embodiment, ruthenium (III) chloride hydrate (RuCl3·nH2O) was used as a ruthenium precursor, cerium (III) nitrate hexahydrate (Ce(NO3)3·6H2O) was used as a cerium precursor, and chloroplatinic acid hexahydrate (HPtCl6·6H2O) was used as a platinum precursor. As a solvent for the coating composition, a mixture of 2.375 ml of isopropyl alcohol and 2.375 ml of 2-butoxyethanol was used. As a metal substrate, a nickel metal (40 mesh) substrate from Ildong Keummangsa Co., Ltd. was used.

[0063] Pretreatment of metal substrates

[0064] Before forming a coating on a metal substrate, the surface of the substrate to be used in each Example and Comparative Example was sandblasted with aluminum oxide (white aluminum oxide, F120) under 0.4 MPa, and then the substrate was placed in a 5 M H2SO4 aqueous solution heated to 80°C and treated for 3 minutes, and then washed with distilled water to complete the pretreatment.

[0065] Example 1

[0066] In a mixed solvent of the above materials, 3 mmol of ruthenium (III) chloride hydrate, 0.6 mmol of cerium (III) nitrate hexahydrate and 0.25 mmol of chloroplatinic acid hexahydrate were fully dissolved for 1 hour, and then 0.5661 mmol of urea and 0.1887 mmol of octadecylamine were added thereto and mixed to prepare a coating composition.

[0067] The prepared coating composition was applied to a pretreated nickel mesh using a brush. The pretreated nickel mesh, coated with the prepared coating composition, was then dried in a 180°C convection oven for 10 minutes and then further heat-treated in a 500°C electric furnace for 10 minutes. The coating, drying, and heat-treatment process was repeated nine additional times. Finally, the mesh was heat-treated in a 500°C electric furnace for one hour to produce an electrolytic electrode.

[0068] Example 2

[0069] An electrode for electrolysis was manufactured in the same manner as in Example 1, except that 0.3774 mmol of urea and 0.3774 mmol of octadecylamine were added to the coating composition.

[0070] Example 3

[0071] An electrode for electrolysis was produced in the same manner as in Example 1, except that 0.1887 mmol of urea and 0.5661 mmol of octadecylamine were added to the coating composition.

[0072] Comparative Example 1

[0073] An electrode for electrolysis was manufactured in the same manner as in Example 1, except that 0.7548 mmol of urea was added to the coating composition instead of adding octadecylamine.

[0074] Comparative Example 2

[0075] An electrode for electrolysis was manufactured in the same manner as in Example 1, except that 0.7548 mmol of octadecylamine was added to the coating composition instead of urea.

[0076] Experimental Example 1. Confirmation of Electrolytic Electrode Performance Using a Half-Cell Test

[0077] In order to confirm the performance of the electrodes manufactured in each embodiment and comparative example, a cathode voltage measurement experiment using a half-cell in chlor-alkali electrolysis was conducted. Specifically, a 32% NaOH aqueous solution was used as the electrolyte, a Pt wire was used as the counter electrode, and a Hg / HgO electrode was used as the reference electrode. The manufactured electrodes were immersed in the electrolyte and then charged at -0.62 A / cm 2 After activation for 3 hours under the current density of -0.62 A / cm, the 100 nm CMOS was used. 2 The voltage of the activated electrode was measured under the current density of . The results are shown in Table 1 below.

[0078] [Table 1]

[0079] category Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Voltage (unit: V) -1.079 -1.083 -1.079 -1.094 -1.084

[0080] The above results confirm that the electrolysis electrode produced by the manufacturing method of the present invention exhibits low overvoltage and superior electrolytic performance. Specifically, the electrode performance is significantly better than that of Comparative Example 1, which uses only urea as a stabilizer, and slightly better than that of Comparative Example 2, which uses only octadecylamine as a stabilizer.

[0081] Experimental Example 2. Confirmation of Durability of Electrolyte

[0082] The ruthenium oxide in the coating of the electrolytic electrode is converted into metallic ruthenium or ruthenium hydroxide (RuO(OH)2) during the electrolysis process, and in the case of reverse current, the ruthenium hydroxide is oxidized to RuO4 2-And eluted in the electrolyte. Therefore, it can be evaluated that the longer it takes to reach the conditions for generating reverse current, the better the durability of the electrode. In view of the above facts, the electrodes manufactured in the various embodiments and comparative examples were activated, and then the reverse current generating conditions were established, and then the voltage change over time was measured. Specifically, the size of the electrode was 10 mm × 10 mm, and the electrode was activated by electrolysis under the conditions of a temperature of 80 ° C and an electrolyte of 32 wt % sodium hydroxide aqueous solution to generate a reverse current at -0.1 A / cm 2 Hydrogen was generated at a current density of -0.2A / cm for 20 minutes. 2 and -0.3A / cm 2 3 minutes each, and at -0.4A / cm 2 After that, the reverse current was measured at 0.05kA / m 2 The time taken for the lower voltage to reach -0.1 V was measured, and the relative reaching time was calculated based on a commercially available electrode (Asahi-Kasei Co., Ltd.) The results are shown in Table 2 below.

[0083] [Table 2]

[0084]

[0085] The above results confirm that the electrodes according to embodiments of the present invention exhibit excellent durability due to the long time required to reach a reverse current. Specifically, Example 1, which used urea and octadecylamine at a ratio of 75:25, exhibited particularly excellent durability. Compared to Example 1, the comparative example, which used only one of urea and octadecylamine, exhibited relatively poor durability.

Claims

1. A method for manufacturing an electrode for electrolysis, the method comprising: applying a coating composition to at least one surface of a metal substrate; and drying and heat-treating the metal substrate coated with the coating composition to form a coating, wherein the coating composition comprises a ruthenium precursor and a stabilizer, wherein the stabilizer comprises urea and octadecylamine, Urea and octadecylamine are contained in a molar ratio of 90:10 to 10:90, and The ruthenium precursor and the stabilizer are contained in a molar ratio of 100:20 to 100:

40.

2. The method according to claim 1, wherein Urea and octadecylamine are included in a molar ratio of 80:20 to 60:

40.

3. The method according to claim 1, wherein The coating composition also includes a cerium precursor.

4. The method according to claim 1, wherein The coating composition also includes a platinum precursor.

5. The method according to claim 1, wherein The solvent of the coating composition is a mixture of isopropyl alcohol and 2-butoxyethanol.

6. The method according to claim 1, wherein The coating, drying and heat treatment were repeated until the content of ruthenium oxide per unit area of ​​the electrolytic electrode was 7 g / m 2 above.

7. The method according to claim 1, wherein The drying is performed at 50° C. to 300° C. for 5 to 60 minutes.

8. The method according to claim 1, wherein The heat treatment is performed at 400° C. to 600° C. for less than 1 hour.

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