KR20210129937A - Pyrochlore-type metal oxide based catalytic electrode for electrolysis of ballast water and preparation method thereof - Google Patents

Abstract

The present invention relates to a method for manufacturing a catalyst electrode for ballast water electrolysis which is used in ballast water electrolysis and includes a mixed catalyst layer of a pyrochlore-based metal oxide excellent in oxidation stability and catalytic effect and a mixed metal compound, and a catalyst electrode for ballast water electrolysis manufactured thereby.

Description

Catalyst electrode for ballast water electrolysis containing pyrochloric metal oxide and manufacturing method thereof

The present invention is a method for producing a catalyst electrode for ballast water electrolysis, which is used in ballast water electrolysis, and includes a mixed catalyst layer of a pyrochloric metal oxide and a metal compound, which is excellent in oxidation stability and catalytic effect, and manufactured by the method It relates to a metal oxide catalyst electrode.

Ballast water refers to seawater or fresh water stored in a tank in a ship to balance the ship by lowering the center of gravity. Ballast water is filled in one port through ballasting work, transferred to another port, and discharged into the new port through deballasting work. In particular, the amount of seawater used as ballast water for international sailing ships moving around the world amounts to about 10 billion tons per year. .

Accordingly, there is a movement to protect the marine environment. For example, the International Maritime Organization (IMO) made the Ballast Water Management Convention in 2004 to prevent disturbance of the marine ecosystem due to the discharge of ballast water, and Environmental regulations that mandate the installation of water treatment systems have been announced.

In order to solve the above-mentioned ecological disturbance problem, ballast water must be treated to kill marine organisms. Examples of such ballast water treatment include ozone sterilization treatment, disinfection treatment using hydrogen peroxide, treatment using an electrolysis method, and the like.

Among them, the ozone sterilization method has a problem in operating for a long time because the sterilization efficiency is low in turbid water and the life of the UV lamp required for ozone generation is short. Disinfection treatment using hydrogen peroxide has the advantage of strong sterilization power and low cost, but there is a possibility of residual hydrogen peroxide being discharged, which makes practical use difficult.

On the other hand, the electrolysis treatment technology of ballast water is a technology necessary for sterilizing marine organisms by applying a constant current to the electrolysis tank when injecting or discharging ballast water to generate a total residual oxidant from seawater, It has the advantage of being able to control the concentration of residual oxidizing agent required for sterilization in real time.

However, since the catalyst electrode used for seawater electrolysis is manufactured using noble metals (Ruthenium, Palladium, Iridium, etc.) as a material, it is difficult to use in large quantities due to problems such as high price and scarcity. For this reason, it is necessary to develop a high-efficiency noble metal reduction catalyst.

In particular, in the case of a metal oxide catalyst electrode used in a conventional seawater electrolysis tank, ruthenium oxide (RuO _x ) and palladium oxide (PdO _x ) are used as main catalysts, so a catalyst electrode with 100% noble metal content must be used for continuous electrolysis In the reaction, research on noble metal reduction catalysts is insufficient because it is possible to increase the efficiency and maintain a long operating life by stabilizing the redox reaction between electrodes.

In particular, the precious metal used in the method is expensive because it is a rare metal, and palladium (Pd) is one of the precious metals that is more expensive than gold (Au).

Therefore, in order to develop an electrolysis tank for ballast water that is inexpensive and has a long life, it is required to develop a catalyst electrode in which palladium (Pd), an expensive catalyst material, is reduced.

As a prior document related to the catalytic electrode of an electrolysis tank, Korean Patent Application Laid-Open No. 2004-0002809 discloses a one-component or two-component complex or multi-component compound composed of an alkoxide such as Ti and Zr and a chloride such as Ru and Ir is diluted with alcohol. After the hydrolysis reaction and polycondensation reaction, a coating solution is prepared, and a method of manufacturing an electrode for electrolysis pretreated with the coating solution is disclosed.

In addition, Korean Patent No. 10-0553364 discloses a metal mixed oxide electrode and a method for manufacturing the same, comprising: an electrode substrate; Iridium (Ir) compound Ruthenium (Ru) compound Tin (Sn) compound and manganese (Mn) compound Titanium (Ti) compound Molybdenum (Mo) compound Tantalum (Ta) compound At least one selected from zirconium (Zr) compound in an organic solvent Disclosed is an electrode comprising a coating layer formed by applying and drying a mixed coating solution to the electrode substrate, performing a first heat treatment process 4 to 15 times, and then performing a second heat treatment.

An object of the present invention is to reduce the expensive palladium content by coating a pyrochlore-based metal oxide catalyst with excellent oxidation stability and catalytic effect on the surface of a titanium electrode, including a pyrochlore-based oxide with secured electrolysis performance. To provide a method for manufacturing a catalyst electrode for ballast water electrolysis.

To this end, an object of the present invention is to provide a method capable of reducing the content of palladium used in an existing commercial electrode by synthesizing a pyrochlore-based metal oxide and coating a metal oxide catalyst on the surface of a titanium electrode.

The above-mentioned task, synthesizing a pyrochlor-based metal oxide; preparing a catalyst electrode coating solution by mixing the pyrochlore-based metal oxide and a metal compound; and coating the catalyst electrode coating solution on the titanium electrode and then heat-treating to form a catalyst electrode.

Preferably, the pyrochlore-based metal oxide is Ru _2-x Pb _2+x O _7-y (x=0.25, y=0.5).

Also preferably, the metal compound is ruthenium (Ru), palladium (Pd), titanium (Ti), tin (Sn), iridium (Ir), platinum (Pt), tantalum (Ta), antimony (Sb) And it may be at least one metal selected from the group consisting of manganese (Mn).

Also preferably, the catalyst electrode coating solution may be prepared by mixing a first solution in which the pyrochlore-based metal oxide and an organic solvent are mixed, a second solution in which the metal compound and an organic solvent are mixed, and a binder solution. .

Also preferably, the binder solution may be a salt selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide and titanium butoxide.

Also preferably, the titanium electrode may be of a general plate material, a regular perforated network, a perforated perforated network, an expanded wire mesh type or a mesh type.

In addition, an object of the present invention is achieved by a catalyst electrode prepared by the above method and comprising a titanium electrode and a mixed catalyst layer comprising a pyrochlore-based metal oxide and a metal oxide formed on the titanium electrode.

According to the method of the present invention, the stability of the catalyst electrode is increased by synthesizing a pyrochloric metal oxide having excellent oxidation stability and catalytic effect and coating a catalyst electrode coating solution containing the metal oxide and the metal compound on the titanium electrode, and expensive palladium It is expected that it will be an opportunity to manufacture a stable catalyst electrode that maintains electrolysis efficiency by reducing the (Pd) content, thereby solving the price problem, which is a problem of insoluble electrodes for electrolysis, and contributing to the catalyst industry for seawater electrolysis. .

1 is a diagram illustrating a cross-section of a catalyst electrode manufactured by a method according to the present invention.
Figure 2 is a schematic diagram showing the reaction occurring at the cathode (Cathode) and the anode (Anode) during the seawater electrolysis operation of the present invention.
3 is an SEM image and elemental analysis data of the pyrochloric ruthenium-lead oxide synthesized in Example 1. FIG.
4 is an SEM image and elemental analysis data of the catalyst electrode prepared in Example 2.
5 is an SEM image and elemental analysis data of the electrode prepared in Comparative Example 1.
6 is a graph showing the voltage change ^{in the seawater electrolysis experiment (current density, 0.05A/cm 2} ) conducted for 30 hours by applying the catalyst electrode of Example 2 and Comparative Example 1 as the anode of the electrolysis tank.

All technical terms used in the present invention, unless otherwise defined, have the following definitions and have the meanings as commonly understood by one of ordinary skill in the art in the relevant field of the present invention. In addition, although preferred methods and samples are described herein, similar or equivalent ones are also included in the scope of the present invention.

The term "about" refers to 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, means an amount, level, value, number, frequency, percentage, dimension, size, amount, weight or length varying by 4, 3, 2 or 1%.

Throughout this specification, unless the context requires otherwise, the terms "comprises" and "comprising" include the steps or elements presented, or groups of steps or elements, but any other step or element, or It is to be understood that a step or group of elements is not excluded.

The present invention relates to a method for manufacturing a catalyst electrode for ballast water electrolysis containing a pyrochloric metal oxide, and to a catalyst electrode manufactured by the method.

According to an embodiment of the present invention, the catalyst electrode comprising a pyrochloric metal oxide for ballast water electrolysis comprises the steps of synthesizing a pyrochloric metal oxide; preparing a catalyst electrode coating solution by mixing the pyrochlore-based metal oxide and a metal compound; and coating the catalyst electrode coating solution on the titanium electrode and then heat-treating it to form a catalyst electrode.

The pyrochloride metal oxide has a cubic crystal structure, and sodium (Na), calcium (Ca), niobium (Nb), ruthenium (Ru), lead (Pb), titanium (Ti), bismuth (Bi) , zirconium (Zr), cadmium (Cd), molybdenum (Mo), magnesium (Mg), radium (Ra), cerium (Ce), yttrium (Y), two or more selected from the group consisting of iridium (Ir) It is a metal oxide containing metal ions. More preferably, the pyrochlore-based metal oxide according to the present invention is Ru _2-x Pb _2+x O _7-y (x=0.25, y=0.5).

Preferably, the method for synthesizing the pyrochloric metal oxide comprises dissolving the compound containing the metal in water and stirring to make a complete solution (if not dissolved, an acid such as nitric acid is added); raising the pH of the solution by adding a base solution such as an aqueous NaOH solution to the solution; adding a sodium hypochlorite (NaClO) solution to the solution and stirring at room temperature or high temperature to precipitate a pyrochloric metal oxide; and filtering, washing, and drying the pyrochlor-based metal oxide compound through filtering (Si Hyoung Oh, et.al., (2012) Synthesis of a metallic mesoporous pyrochlore as a catalyst for lithium-O, Nature Chemistry 4(12):104-1010.)

The catalyst electrode coating solution forming step includes the synthesized pyrochlore-based metal oxide, ruthenium (Ru), palladium (Pd), titanium (Ti), tin (Sn), iridium (Ir), platinum (Pt), tantalum and mixing at least one metal compound selected from the group consisting of (Ta), antimony (Sb) and manganese (Mn).

The forming of the catalyst electrode includes applying the catalyst electrode coating solution on the titanium substrate and then performing heat treatment.

Preferably, the forming of the mixed metal oxide catalyst layer comprises: preparing a first coating solution in which a pyrochloric metal oxide and an organic solvent are mixed; preparing a second coating solution in which a metal compound and an organic solvent are mixed; preparing a coating solution by mixing the first coating solution, the second coating solution, an organic solvent, a binder solution, and carbon and then bathing; After the coating solution is applied on the surface of the titanium electrode, heat treatment at 400° C. to 500° C. (3 minutes to 5 minutes); and further sintering the electrode on which the catalyst layer is formed at 600° C. to 700° C. (1 hour).

The organic solvent may be selected from the group consisting of lower alcohols having 1 to 4 carbon atoms (eg, methanol, ethanol, propanol and butanol) and hydrochloric acid.

The binder solution may be selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide and titanium butoxide.

1 is a cross-sectional view of a pyrochloric metal oxide-containing catalyst electrode prepared by the method of the present invention.

Referring to FIG. 1 , a catalyst layer (MOx) including a pyrochlore-based metal oxide and a metal compound is formed on the surface of a titanium electrode (Ti).

The method of the present invention forms a catalyst layer including a pyrochlore-based metal oxide on a titanium electrode, thereby reducing the content of palladium (Pd), an expensive noble metal, and preparing a mixed metal oxide catalyst electrode stable for seawater electrolysis.

The method of the present invention uses an electrode coated with a catalyst layer containing a pyrochloric metal oxide having excellent oxidation stability and catalytic effect, thereby dramatically reducing the palladium content of the surface catalyst layer and a catalyst showing stable electrolysis efficiency and lifespan electrodes can be manufactured.

In the above, the titanium electrode may include a titanium metal or a titanium alloy having a purity of 100%. The titanium electrode may be of a general plate material, a regular perforated network, a perforated perforated network, an expanded wire mesh type, or a mesh type. In addition, the titanium electrode may be an electrode having a rough surface treated with sand blast or the like in order to increase the reaction area during the electrolysis reaction.

In the present invention, ballast water is water stored inside to balance the ship, and may be seawater or freshwater, and more preferably seawater.

When the ballast water is seawater, the reaction that occurs during electrolysis of seawater can be explained by the following equation.

[Scheme 1]

Anode(+pole) :

2OH ^- → H ₂ O + 1/2O ₂ ↑ + 2e ^-

NaCl → Na ⁺ + Cl ^-

2Cl ^- → Cl ₂ ↑ + 2e ^- (main reaction)

Cl ₂ + H ₂ O → HClO (hypochlorous acid) + H ⁺ + Cl ^- (side reaction)

[Scheme 2]

Cathode (-pole):

2H ₂ O +2e ^- → H ₂ ↑ + 2OH ^- (main reaction)

Na ⁺ + OH ^- → NaOH (side reaction)

Mg ⁺² + Ca ⁺² + 4OH ^- → Mg(OH) ₂ + Ca(OH) ₂ (side reaction)

A schematic diagram related to the reaction is shown in FIG. 2, and as in Scheme 1, if the catalyst layer is not densely formed due _{to the generation of Cl 2} gas and O _{2 gas generated in the anode reaction during seawater electrolysis, the catalyst layer} Cracks or fragments may occur. In addition, in order for the reaction to proceed well, the reduction in seawater electrolysis efficiency can be prevented only when the conductivity of the catalyst to receive and reduce electrons is high.

In the present invention, a catalyst layer containing a pyrochlore-based metal oxide having excellent oxidation stability and catalytic effect is formed on the surface of the titanium electrode to prevent corrosion of the titanium metal, which is the current collector, and to reduce the palladium oxide (PdO _x ) content, which is a noble metal catalyst. It is possible to prevent a decrease in the efficiency of the electrolysis process by enhancing the efficiency.

When the catalyst electrode manufactured according to the method of the present invention is used in a ballast water electrolysis facility, the amount of expensive palladium is remarkably reduced, but the reduction of the reduction reaction efficiency for reducing _{Cl 2} or O _{2 is prevented, so that the ballast water} It can be used for a long time without a decrease in energy efficiency and residual oxidizing agent (TRO) generation efficiency even in the continuous electrolysis reaction in or out.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the following examples and the accompanying drawings are only examples used to show the state after the coating of the present invention, and the scope of the electrode coating of the present invention is not limited by the drawings.

Example 1 - Preparation of pyrochloric metal oxide

The pyrochlore-based metal oxide (Ru _2-x Pb _2+x O ₇ (x=0.25, y=0.5)) used in the present invention was prepared by the following low-temperature synthesis process. Dissolve 33.03 g of a commercial ruthenium(III) nitrosyl nitrate solution (manufactured by Sigma-Aldrich) and 1.34 g of lead subacetate (manufactured by Sigma-Aldrich) in 60 mL of distilled water and stir for 1 hour. to make a complete solution. Then, 33 mL of 2.0 M aqueous NaOH solution is slowly added to adjust the pH to 10 or higher, and the mixture is further stirred for 3 hours. After that, 5 mL of commercial NaClO solution (13.7 %) is slowly added and further stirred for 24 hours. Then, the compound is filtered through filtering and washed with distilled water. Then, it ^{was dried in an oven at 80 °} C to obtain a compound (composite weight: about 1.4 g).

Example 2 - Preparation of Catalyst Electrode Containing Pyrochloric Metal Oxide

First, 0.5 g of the pyrochloric metal oxide (Ru _2-x Pb _2+x O _7-y (x=0.25, y=0.5)) of Example 1 was dispersed in _{10 mL of butanol to prepare Solution 1, RuCl 2} 1 g was dissolved in 5 mL of HCl to prepare solution 2. As the final coating solution, 0.14 mL of solution 1, 0.6 mL of titanium propoxide, 0.015 g of carbon, and 6.4 mL of solution 2 were mixed with 3 mL of butanol and bathed for 2 hours to prepare a catalyst electrode coating solution.

The catalyst electrode coating solution was coated on the titanium electrode using gun spray at a rate of 1 mL/min, dried, and then heat-treated at 450° C. for 3 minutes. After this process was performed 5 times, a catalyst electrode was prepared by heat treatment at 650° C. for 1 hour.

In addition, the surface of the prepared catalyst electrode is shown in FIG. 4 . In addition, the prepared catalyst electrode was used as an anode in the electrolysis tank and a titanium electrode, the same material, was applied to the cathode without pretreatment, and a continuous seawater electrolysis experiment (current density, 0.05A/cm) for 30 hours. ² ) was performed twice or more. The voltage change during seawater electrolysis was measured and shown in FIG. 6 .

Comparative Example 1 - Conventional Commercial Titanium Electrode

First, solution 1 was prepared by adding 1 g _{of RuCl 2} to 10 mL of butanol _{, and solution 2 was prepared by dissolving 5 g of PdCl 2} (or PdCl ₃ ) in 5 mL of HCl. As the final catalyst electrode coating solution, 0.14 mL of solution 1, 0.6 mL of titanium propoxide, 0.015 g of carbon, and 6.4 mL of solution 2 were mixed in 3 mL of butanol and bathed for 2 hours to prepare a catalyst electrode coating solution.

The catalyst electrode coating solution was coated on a mesh-type titanium electrode using a gun spray at a rate of 1 mL/min, dried and then heat-treated at 450° C. for 3 minutes. After this process was performed 5 times, a catalyst electrode was prepared by heat treatment at 650° C. for 1 hour.

In addition, the surface of the prepared catalyst electrode is shown in FIG. 5 . In addition, the prepared catalyst electrode was used as an anode in the electrolysis tank and a titanium electrode, the same material, was applied to the cathode without pretreatment, and a continuous seawater electrolysis experiment (current density, 0.05A/cm) for 30 hours. ² ) was performed twice or more. The voltage change during seawater electrolysis is shown in FIG. 6 .

_{3 is an SEM photograph of Ru 2-x} Pb _2+x O _7-y (x=0.25) prepared in Example 1, confirming that catalyst particles with a size of several tens of nanometers were synthesized, and in the results of elemental analysis The atomic ratio of ruthenium to lead was about 1.75 : 2.23.

4 is a SEM photograph of the mixed metal oxide catalyst electrode prepared in Example 2, _{the surface shape of which a catalyst of Ru 2-x} Pb _2+x O _7-y (x=0.25) is rough coated on the titanium electrode. looks like As a result of elemental analysis, it was confirmed that the atomic ratio of ruthenium and lead was about 10.6:6.

5 is an SEM photograph of the catalyst electrode prepared in Comparative Example 1, which is a conventional commercial catalyst electrode. The content ratio (atomic ratio) of ruthenium and palladium is about 1:1, which is a catalyst electrode coated with a catalyst made of 100% noble metal. As a result of elemental analysis, it was confirmed that the atomic ratio of Ru:Pd=1:1 was shown and the noble metal content was 100%.

6 shows the voltage change when the ^{continuous seawater electrolysis experiment (current density, 0.05A/cm 2} ) was performed two or more times for 30 hours using the catalyst electrode prepared in Example 2 and Comparative Example 1 as an anode. is a graph showing The initial voltage of seawater electrolysis of the conventional catalyst electrode (Comparative Example 1) and the catalyst electrode prepared in Example 2 was the same, and it was confirmed that the overvoltage was less than that of Comparative Example 1 in the continuous electrolysis process. In addition, when the seawater electrolysis is restarted after 10 hours (36000s) of electrolysis, a lower overvoltage than Comparative Example 1 is applied, indicating that the reactivation catalyst effect is better.

As described above in detail a specific part of the present invention, for those of ordinary skill in the art, this specific description is only a preferred embodiment, and it is clear that the scope of the present invention is not limited thereto. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (7)

synthesizing a pyrochloric metal oxide;
preparing a catalyst electrode coating solution by mixing the pyrochlore-based metal oxide and a metal compound; and
A method for manufacturing a catalyst electrode containing pyrochlore-based metal oxide for ballast water electrolysis, comprising coating the catalyst electrode coating solution on a titanium electrode and then heat-treating to form a catalyst electrode. The pyrochloride for ballast water electrolysis according to claim 1, wherein the pyrochloric metal oxide is Ru _2-x Pb _2+x O _7-y (x=0.25, y=0.5). A method for manufacturing a catalyst electrode containing a metal oxide. According to claim 1, wherein the metal compound is ruthenium (Ru), palladium (Pd), titanium (Ti), tin (Sn), iridium (Ir), platinum (Pt), tantalum (Ta), antimony (Sb) and at least one metal selected from the group consisting of manganese (Mn). The method of claim 1, wherein the catalyst electrode coating solution is prepared by mixing a first solution in which the pyrochloric metal oxide and an organic solvent are mixed, a second solution in which the metal compound and an organic solvent are mixed, and a binder solution. A method for manufacturing a catalyst electrode containing a pyrochloric metal oxide for ballast water electrolysis, characterized in that. The catalyst electrode of claim 4, wherein the binder solution is selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide and titanium butoxide. manufacturing method. The method of claim 1, wherein the titanium electrode is of a general plate material, a regular perforated network, a perforated perforation network, an expanded wire mesh type or a mesh type. A pyrochloride for ballast water electrolysis prepared by the method of any one of claims 1 to 6, and comprising a titanium electrode and a catalyst electrode comprising a pyrochloric metal oxide and a metal oxide formed on the titanium electrode. Catalyst electrode containing metal oxide.

Images