KR20040002809A - Method for preparation of coating solution for electrolysis and a metal oxide electrode by using it - Google Patents

Abstract

PURPOSE: A coating solution for electrolysis electrode is provided which is prepared by adding pure water and acid to the mixture after mixing a matrix of metal alkoxide with one or two chlorides of precious metals including Ru, Ir, Sn, Pt and Pb, and a manufacturing method of metal oxide electrode coated using the same is provided. CONSTITUTION: The method comprises the steps of preparing a coating solution by adding pure water and acid to the mixture after mixing a transition metal alkoxide with one or two chlorides of precious metals including Ru, Ir, Sn, Pt and Pb; dipping a titanium supporter into the coating solution or spraying the coating solution onto the titanium supporter so that the titanium supporter is coated with the coating solution; drying the coating solution coated titanium supporter; and firing the titanium supporter coated and dried in the above steps at a temperature of 300 deg.C or more, wherein alkoxide of metals including Ti and Zr is additionally added to the coating solution in the coating solution preparation process.

Description

Coating solution for electrolysis electrode and method for producing coated metal oxide electrode using same

The present invention relates to a coating solution for an electrolytic electrode and a method for producing a metal oxide electrode coated using the same, and more specifically, to a titanium support, based on a metal alkoxide such as titanium or zirconium, Ru, Ir, Sn, Pt and The present invention relates to a electrolytic electrode coating solution prepared by mixing one or two chlorides of a noble metal including Pb, and then adding ultrapure water and an acid, and to a method of manufacturing a metal oxide electrode prepared by immersion coating thereof.

Methods of manufacturing electrodes for electrolysis include pyrolysis, arc melting, plasma melting, electroplating, and the like. Electrodes are manufactured by one or two or more of these methods. Among them, the most common and economical method is pyrolysis, and many patents have been published centering on the application of alkaline aqueous solution to electrolysis.

Japanese Patent Application Laid-Open No. 03-131385 discloses a technique in which titanium is used as an electrode ceramic material and carbon nitride is coated thereon by arc melting or plasma melting. However, the above method has a disadvantage in that it is difficult to manufacture the electrode because a large amount of coating material is lost, the large electrode cannot be coated uniformly, and the coating process is complicated.

Korean Patent Publication Nos. 79-3290 and 91-2102 describe a method of manufacturing an electrode for producing chlorine and caustic soda. However, the electrode manufactured by the above method consumes a large amount of energy due to low chlorine overvoltage but high oxygen overvoltage, and is used in extreme reactions. Has been pointed out.

Accordingly, in Korean Patent Publication No. 1998-9525, in order to solve the above problems, one or two chlorides of precious metals composed of Ru, Sn, Ir, Pt, and Pb are dissolved in a hydrochloric acid solvent, and then a dispersion solvent is dissolved. The present invention proposes a method for producing an electrode for electrolysis, which has a long lifetime, which can be effectively lowered by chlorine overvoltage and oxygen overvoltage of an electrode by being dipped in a coating solution obtained by mixing in an organic solvent.

However, the above method has a disadvantage in that the coating solution is not stable, so it is difficult to store it for a long time, and the coating film is difficult to form uniformly and cleanly during coating, and the coating film is easily peeled off and worn out.

In view of the above disadvantages, the present inventors can effectively lower the chlorine overvoltage and oxygen overvoltage of the electrode, provide a stable coating solution, and provide a coating solution in which the coating film is uniform and not easily peeled off or worn after coating, and an electrode using the same.

Accordingly, an object of the present invention is to prepare a sol-gel solution by mixing a metal alkoxide and one or two chlorides of noble metals to prepare a sol-gel solution. The present invention provides an electrode for electrolysis, which can effectively reduce overvoltage and oxygen overvoltage, and has a long lifespan.

The above object of the present invention is to dilute the one-component or two-component complex or multicomponent compound consisting of alkoxides such as Ti, Zr and chlorides such as Ru and Ir in alcohol, and then add ultrapure water and acid to hydrolysis and polycondensation reactions. By preparing a coating solution through the coating solution by dipping the conductive support pre-treated in the coating solution to produce an electrode for electrolysis to complete the present invention.

Hereinafter, the configuration of the present invention.

1 is a process for producing a coating solution and a metal oxide by a sol-gel process.

2 is an apparatus diagram of a metal oxide coating process by a immersion method.

3 is a surface state of a pretreated electrode support.

4 is a surface state of an electrode after coating and firing on a pretreated electrode support.

The present invention

1) To prepare an ideal coating solution, a mixture of transition metals (Ti, Zr) alkoxides and one or two chlorides of noble metals consisting of Ru, Ir, Sn, Pt and Pb is mixed and then hydrolyzed by adding ultrapure water and acid. Preparing a stable sol-gel coating solution without precipitation through a polycondensation reaction;

2) coating the titanium support by dipping or spraying the coating solution on the sol-gel;

3) drying the coated titanium support without cracking the coating surface; And

4) firing the coated and dried titanium support to form an oxide in the coating layer.

Conventional electrode coating solution manufacturing method dissolves a metal salt of a desired composition in a solvent and coated on the electrode support, and then pyrolyzed to prepare a coating, but in the extreme reaction has a high oxygen overvoltage and the catalyst membrane is easy to deflect. When the electrode is coated by preparing a stable solution without precipitation due to the preferred composition by the sol-gel process, the coating layer forms a network structure, thereby producing an electrode having excellent adhesion and wear resistance.

To this end, in the present invention, metal alkoxides such as Ti and Zr, and one or two chlorides or complex compounds such as Ru, Ir, Sn, Pt, and Pb are added, followed by addition of ultrapure water and acid to hydrolysis and polycondensation reactions. To provide a stable sol-gel solution.

Electrolytic electrode production method for achieving the object of the present invention comprises the following steps.

1) To prepare an ideal coating solution, one or two chlorides or complex compounds such as transition metal (Ti, Zr) alkoxide and Ru, Ir, Sn, Pt and Pb are added, followed by addition of ultrapure water and acid Preparing a stable sol-gel coating solution without precipitation through decomposition and polycondensation reaction;

2) coating the titanium support by dipping or spraying the coating solution on the sol-gel;

3) drying without cracks on the coating surface;

4) firing step for forming oxide in the coating layer.

Hereinafter, the coating solution for preparing the electrode for electrolysis of the present invention and the electrode manufacturing method thereof will be described in more detail.

The electrolytic electrode manufacturing process of the present invention is divided into a coating sol-gel solution manufacturing process and an electrode coating process.

One component consisting of chlorides such as Ru, Ir, Sn, Pt and Pb after diluting one kind of alkoxide of Ti and Zr in alcohol to 50 to 100 times in order to prepare an ideal coating solution while reducing oxygen overvoltage and chlorine overvoltage Alternatively, a dilution solution of a bicomponent compound or a multicomponent compound is added dropwise to the mixture, followed by addition of ultrapure water and acid to prepare a sol-gel solution for coating through a hydrolysis reaction and a polycondensation reaction. Here, the alcohol dilution solution of a one-component or two-component complex or multicomponent compound composed of chlorides such as Ru, Ir, Sn, Pt, and Pb may also be used as a single component composed of chlorides such as Ru, Ir, Sn, Pt, and Pb in alcohol. It is the solution which diluted 50-100 times of mole ratio compound or multicomponent compound in molar ratio.

In the present invention, the molar ratio of one or two chlorides of the noble metals composed of Ru, Ir, Sn, Pt and Pb and one alkoxide of a metal composed of Ti and Zr is preferably 0.4: 0.6.

In the present invention, the sol-gel solution is preferably aged for 2 to 4 hours.

The conductive support pretreated in the solution is immersed to coat the withdrawal rate at 1-15 cm / min. If the withdrawal speed is too fast out of the above range, the thickness becomes thin and the surface condition becomes rough, and if out of the above range is too slow, the manufacturing speed is low and manufacturing efficiency is low.

The drying process removes moisture and organics from the coating layer and affects the physical state of the final coating layer and dried at a temperature of 50-350 ° C.

The firing process completely removes the residual organics and crystallizes the metal alkoxide and chloride with the metal oxide, which is then fired to a temperature of 400-800 ° C. to prepare the electrode.

In the present invention, the drying and firing is repeated once to 20 times, the last firing is preferably performed for 1 to 5 hours.

In the present invention, the metal alkoxide is composed of titanium isopropoxide, titanium ethoxide, titanium n-propoxide, titanium butoxide, zirconium n-propoxide, zirconium isopropoxide, zirconium butoxide and zirconium ethoxide. At least one selected from the group consisting of is preferable.

In the present invention, the acid is preferably any one or more selected from the group consisting of hydrochloric acid, nitric acid, acetic acid and sulfuric acid.

Hereinafter, the present invention will be described in more detail with reference to the following Examples and Experimental Examples. However, the following Examples and Experimental Examples are only for illustrating the present invention, the scope of the present invention is not limited to these.

Example 1: RuO ₂ -TiO ₂ Coated titanium electrode

a. Coating solution manufacturing

The starting material is ruthenium chloride and titanium isopropoxide in a molar ratio of 0.4: 0.6. First, dilute titanium isopropoxide in an alcohol molar ratio 50 to 100 times, and then add ruthenium chloride dissolved in alcohol. Ultrapure water diluted with alcohol and hydrochloric acid are added thereto to undergo a hydrolysis reaction and a polycondensation reaction. This sol solution is aged for 2-4 hours.

b. Coating, drying, firing step, i.e. electrode manufacturing step

The pretreated titanium support is coated by dipping into the prepared sol solution at a rate of 5 cm / min. The electrode is dried at a temperature of 50-100 ° C. using a hot air fan, and then fired at 450-600 ° C. for 10 minutes. As described above, the coating was repeatedly baked 10 times, dried and calcined at 450-600 ° C. for 2 hours.

c. Electrochemical analysis

The prepared electrode was used as a cathode and platinum and rhonium alloy electrode as a negative electrode, and a saturated calomel electrode was used as a reference electrode, and electrochemical analysis was performed using 1 M sulfuric acid as an electrolyte. A Tafel's plot was performed to determine the overvoltage and current density. The experimental conditions were the potential range from 0 to 1.4V and the scan rate to 1mV / s. In addition, in order to determine the degree of polarization of the electrode at the same current density, an analysis of the negative polarity curve was performed under the same conditions as the Tafel's plot.

d. Performance measurement result

When the molar ratio of RuO ₂ and TiO ₂ is 0.4 to 0.6, it shows higher exchange current density and lower overvoltage than 100% RuO ₂ electrode manufactured by conventional pyrolysis method.

Example 2: RuO ₂ -ZrO ₂ Coated titanium electrode

a. Coating solution manufacturing

Ruthenium chloride and zirconium normal propoxide are prepared in a molar ratio of 0.4: 0.6. First, after diluting zirconium normal propoxide in alcohol, ruthenium chloride dissolved in alcohol is added dropwise to the previous zirconium dilution solution. Ultrapure water diluted with alcohol and nitric acid are added thereto to undergo a hydrolysis reaction and a polycondensation reaction. This sol matures for 2-4 hours.

b. Coating, drying and firing steps

The pretreated titanium support is dip coated on the prepared sol solution. The coating speed was 5 cm / min. The electrode is dried in a hot air fan at 50-100 ° C., and then fired at 450-600 ° C. for 10 minutes. Thus repeated coating 10 times, dry firing and finally fired at 450-600 ℃ for 2 hours.

c. Electrochemical analysis

It proceeded in the same manner as in Example 1.

d. Performance measurement result

When the molar ratio of RuO ₂ and ZrO ₂ is 0.4 to 0.6, it shows higher exchange current density and lower overvoltage compared to the existing 100% RuO ₂ .

Experimental conversion constant (α) and exchange current density (i ₀ ) α i ₀ (mA / cm ² ) Comparative Example 100% RuO ₂ 0.834 0.050 Example 40% RuO ₂ /60% TiO ₂ 0.851 0.098 Example 40% RuO ₂ /60% ZrO ₂ 0.812 0.044

Overvoltage (η) η (1mA / cm ² ) η (10mA / cm ² ) η (100mA / cm ² ) Comparative Example 100% RuO ₂ 0.231 0.276 0.329 Example 40% RuO ₂ /60% TiO ₂ 0.201 0.252 0.303 Example 40% RuO ₂ /60% ZrO ₂ 0.234 0.249 0.255

As described above, the electrode manufactured according to the present invention can reduce the power ratio by high current density and low oxygen overvoltage, and the coating film has a mesh structure to improve adhesion, thereby providing excellent wear resistance, corrosion resistance, and long life. This is very useful in the electrical and electronics industry.

Claims (9)

Mixing one or two chlorides of noble metals consisting of Ru, Ir, Sn, Pt, and Pb, and then adding ultrapure water and an acid to prepare a coating solution; Coating the titanium solution by dipping or spraying the titanium support; Drying the coated titanium support; And In the manufacturing method of the electrode for electrolysis consisting of the step of firing the coated and dried titanium support in the above step 300 ℃, In the step of preparing the coating solution, a method for producing an electrode for electrolysis, characterized in that it further adds one alkoxide of a metal consisting of Ti and Zr. The electrolysis according to claim 1, wherein the molar ratio of one or two chlorides of the noble metals consisting of Ru, Ir, Sn, Pt and Pb and one alkoxide of one metal of Ti and Zr is 0.4: 0.6. Method for producing an electrode for use. The method according to claim 1, wherein the coating solution is diluted 50 to 100 times in molar ratio of one alkoxide of a metal consisting of Ti and Zr in alcohol and then one chloride of a noble metal consisting of Ru, Ir, Sn, Pt and Pb or Electrolyte characterized in that it is prepared by dropwise mixing the two alcohol dilution solution, and then by adding dropwise ultrapure water and hydrochloric acid dropwise to prepare a transparent sol through hydrolysis and polycondensation reaction and then aged the sol for 2 to 4 hours Method for producing an electrode for use. The method of claim 1, wherein the withdrawal speed is maintained at a rate of 1 to 15 cm / min when the titanium support is immersed in the coating solution in the coating step. The method of claim 1, wherein the temperature of the drying step is in the range of 50 ~ 350 ℃. The method of claim 1, wherein the temperature of the firing step is in the range of 400 ~ 800 ℃. The method of claim 1, wherein the drying and firing are repeated once to 20 times, and the final firing is performed for 1 to 5 hours. The method of claim 1, wherein the metal alkoxide is titanium isopropoxide, titanium ethoxide, titanium n-propoxide, titanium butoxide, zirconium n-propoxide, zirconium isopropoxide, zirconium butoxide and zirconium ethoxy Method for producing an electrode for electrolysis, characterized in that any one or more selected from the group consisting of side. The method of claim 1, wherein the acid is at least one selected from the group consisting of hydrochloric acid, nitric acid, acetic acid, and sulfuric acid.