KR20210121750A - Titanium dioxide coated 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 including a titanium dioxide coating layer and a metal oxide catalyst layer that are chemically stable in ballast water electrolysis, and a catalyst electrode for ballast water electrolysis manufactured by the method.

Description

Titanium dioxide-coated catalyst electrode for ballast water electrolysis and manufacturing method thereof

The present invention relates to a method for manufacturing a metal oxide catalyst electrode for ballast water electrolysis comprising a titanium dioxide coating layer that is chemically very stable in ballast water electrolysis, and a metal oxide catalyst electrode manufactured by the method.

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 precious 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 lifespan, it is required to develop a catalyst electrode in which noble metals (Ru, Pd), which are main catalysts of the catalyst electrode, are 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; At least one selected from an iridium (Ir) compound, a ruthenium (Ru) compound, a tin (Sn) compound, a manganese (Mn) compound, a titanium (Ti) compound, a molybdenum (Mo) compound, a tantalum (Ta) compound, and a zirconium (Zr) compound Disclosed is an electrode comprising a coating layer formed by applying and drying a coating solution in which a species is mixed with an organic solvent to the electrode substrate, performing a primary heat treatment process 4 to 15 times, and then performing a secondary heat treatment.

The present invention is a titanium dioxide coating for ballast water electrolysis that secures electrolysis performance while reducing expensive palladium content by using an electrode coated with chemically stable titanium dioxide on the surface of a titanium electrode as a current collector for a metal oxide catalyst electrode It is for manufacturing a catalyst electrode.

To this end, an object of the present invention is to provide a method capable of reducing the content of palladium used in conventional commercial electrodes by coating _{titanium dioxide (TiO 2 ) on the surface of a titanium electrode.}

The above-described task, forming a coating layer by coating _{titanium dioxide (TiO 2 ) on the surface of the titanium electrode;} And comprising the step of forming a mixed metal oxide catalyst layer on the coating layer, for ballast water electrolysis titanium dioxide (TiO ₂ ) It is achieved by a method of manufacturing a catalyst electrode.

Preferably, the coating layer forming step may be formed by purging a mixed gas of argon and oxygen in a vacuum chamber and evaporating the titanium target using plasma at a temperature of 300° C. to 400° C. to deposit titanium oxide on the surface of the titanium electrode. have.

Also preferably, in the step of forming the mixed metal oxide catalyst layer, ruthenium (Ru), palladium (Pd), titanium (Ti), tin (Sn), iridium (Ir), platinum (Pt), tantalum (Ta), anti After applying a coating solution in which two or more kinds of metal ions selected from the group consisting of mono (Sb) and manganese (Mn), an organic solvent, and a binder solution, heat treatment may be included.

Also preferably, the mixed metal oxide catalyst layer may contain ruthenium (Ru) and palladium (Pd) in an atomic ratio of 1 to 10:1.

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.

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

In addition, an object of the present invention is achieved by a titanium dioxide coated catalyst electrode for ballast water electrolysis prepared by the above method and comprising a titanium electrode, a titanium dioxide coating layer formed on the titanium electrode, and a mixed metal oxide catalyst layer formed on the coating layer. .

According to the method of the present invention, titanium dioxide (TiO ₂ ), a transition metal oxide, is thinly coated on the initial coating electrode to increase the stability of the catalyst electrode and reduce the expensive palladium (Pd) content to maintain the electrolysis efficiency. By manufacturing it, it is expected to solve the problem of price, which is a problem of insoluble electrodes for electrolysis, and to contribute 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 a photograph, SEM image, and elemental analysis data of the electrode coated with titanium oxide in Example 1.
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 a seawater electrolysis experiment (current density, 0.05A/cm 2} ) conducted for 10 hours by applying the catalyst electrode of Example 2 and Comparative Example 1 as an anode of an 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 titanium dioxide-coated catalyst electrode for ballast water electrolysis and a catalyst electrode manufactured by the method.

According to an embodiment of the present invention, the titanium dioxide coating catalyst electrode for ballast water electrolysis _{is formed by coating titanium dioxide (TiO 2} ) on the surface of the titanium electrode to form a coating layer; and forming a mixed metal oxide catalyst layer on the coating layer.

The coating layer may be coated with a thin film thickness of titanium oxide using a plasma method that can be deposited within a short time in a temperature range in which the deformation of titanium is small.

Preferably, the coating layer of titanium oxide may be formed by evaporating a titanium target using plasma at a temperature of 300° C. to 400° C. in a vacuum chamber to deposit titanium oxide on the surface of the titanium electrode. At this time, the vacuum chamber is preferably purged with argon and oxygen (10 vol.%) gas.

In addition, the coating of the titanium oxide may be applied to a rough surface of a commercial titanium electrode or a surface of a titanium electrode subjected to general polishing or electrolytic polishing.

The titanium oxide (TiO ₂ ) coating may be formed according to the method of Example 1 below, and TiO ₂ may be formed on the surface of a commercial titanium-based electrode.

The coating is characterized in that it is coated on the surface using plasma at a low temperature at which the deformation of titanium does not occur. Preferably, the temperature may be 300 °C to 400 °C, more preferably 350 °C. By performing the heat treatment process at a relatively low temperature that does not cause deformation of the titanium metal, the shape and properties of the metal are not deformed, and the hardness value is higher than that of the general heat treatment surface.

_{Titanium oxide (TiO 2} ) coating according to an embodiment of the present invention by using a 99.99% high-purity titanium target and O ₂ gas (10 vol.% in Ar gas) to form a _{TiO 2 layer on the electrode surface.}

The mixed metal oxide catalyst layer forming step includes ruthenium (Ru), palladium (Pd), titanium (Ti), tin (Sn), iridium (Ir), platinum (Pt), tantalum (Ta), antimony (Sb) and and applying a coating solution in which two or more metal ions selected from the group consisting of manganese (Mn), an organic solvent, and a binder solution are mixed, followed by heat treatment.

Preferably, the step of forming the catalyst layer comprises: preparing a first coating solution in which a ruthenium compound and an organic solvent are mixed; preparing a second coating solution in which a palladium 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 a titanium salt selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide and titanium butoxide.

1 is a cross-sectional view of a titanium dioxide coated catalyst electrode prepared by the method of the present invention.

Referring to FIG. 1 , a titanium oxide layer and a mixed metal oxide catalyst layer (Mixed metal oxide (MOx)) are sequentially formed on a surface of a titanium electrode (Ti).

The method of the present invention reduces the content of precious metals ruthenium (Ru) and palladium (Pd) by forming a titanium layer on the titanium electrode, and prepares a mixed metal oxide catalyst electrode stable for seawater electrolysis.

The method of the present invention _{uses an electrode coated with chemically stable titanium oxide (TiO 2} ), thereby remarkably reducing the palladium content of the surface catalyst layer and producing a catalyst electrode showing stable electrolysis efficiency and lifespan.

Titanium oxide coating can be coated with high hardness titanium oxide using a plasma method that can be deposited in a short time in a temperature range in which the deformation of titanium is small.

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.

Therefore, in the present invention, _{by thinly coating a chemically stable titanium oxide (TiO 2} ) on the surface of the titanium electrode, corrosion of the titanium metal as a current collector is prevented, and _{even if the content of palladium oxide (PdO x} ), which is a noble metal catalyst, is reduced, insufficient catalytic efficiency is obtained. It can be reinforced to prevent a decrease in the efficiency of the electrolysis process.

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 - Titanium Dioxide (TiO ₂ ) Coated Electrode

A mesh-type titanium-based electrode was prepared, and impurities on the electrode surface were primarily removed using alcohol and acetone. The primary treated electrode ^{was placed in a vacuum chamber in which a high vacuum of about 1x10 -6} Torr was maintained, and a high-purity titanium target was prepared. After purging the vacuum chamber with argon (Ar) gas and 10 vol.% oxygen, a voltage of 100 kV to 150 kV was applied to the electrode and the temperature was raised to about 350 ° C. The titanium target was evaporated using plasma. . The titanium target used at this time was a high-purity titanium target of 99.99%, the titanium evaporated due to plasma is in an ionized state, and O ₂ (10 vol.% in Ar) and deposited on the surface of the electrode. A photograph of an electrode having a titanium oxide coating layer on the surface prepared above is shown in FIG. 3 , and it was confirmed that the prepared electrode was gray and titanium and oxygen elements were analyzed on the electrode surface.

Example 2 - Mixed Metal Oxide Catalyst Electrode

_{First, 1 g of RuCl 2} was added to 10 mL of butanol to prepare solution 1, and PdCl ₂ or PdCl ₃ 1.66 was dissolved in 5 mL of HCl to prepare solution 2. As a 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 in 3 mL of butanol, followed by boiling for 2 hours to prepare a catalyst electrode coating solution.

The catalyst electrode coating solution was coated on the titanium dioxide (TiO ₂ ) coated electrode prepared in Example 1 at a rate of 1 mL/min using gun spray, 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, followed by a continuous seawater electrolysis experiment (current density, 0.05A/cm) for 10 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 a 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, followed by boiling 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, followed by a continuous seawater electrolysis experiment (current density, 0.05A/cm) for 10 hours. ² ) was performed twice or more. The voltage change during seawater electrolysis is shown in FIG. 6 .

3, the electrode manufactured in Example 1 _{is thinly coated with titanium dioxide (TiO 2} ) on the surface of the titanium electrode, and shows a surface shape similar to the surface of the titanium current collector, and only titanium and oxygen without impurities. appear.

4 is a catalyst electrode prepared in Example 2, an electrode coated with a mixed metal oxide catalyst of ruthenium and palladium on the titanium dioxide-coated electrode prepared in Example 1, titanium dioxide is thinly coated on the surface of the titanium current collector surface As it is, the mixed metal oxide catalyst coating layer also shows an uneven surface phenomenon. As a result of elemental analysis, the palladium content showed an atomic ratio of about 1/3 compared to that of ruthenium.

5 is a catalyst electrode prepared in Comparative Example 1, which is a conventional commercial catalyst electrode. The ruthenium and palladium content ratio (atomic ratio) is about 1:1, which is a mixed metal oxide catalyst electrode coated with a catalyst composed of 100% noble metal.

6 is a graph showing the voltage change when a ^{continuous seawater electrolysis experiment (current density, 0.05A/cm 2} ) is performed two or more times for 10 hours using the catalyst electrode of Example 2 and Comparative Example 1 as an anode. It is a graph. 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, the catalytic electrode manufactured in Example 2 was 3.15 V at the termination voltage after 10 hours of seawater electrolysis, which was about 0.1 V less than the conventional catalyst electrode manufactured in Comparative Example 1.

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)

Forming a coating layer by coating _{titanium dioxide (TiO 2} ) on the surface of the titanium electrode; and forming a mixed metal oxide catalyst layer on the coating layer, the method of manufacturing a titanium dioxide coated catalyst electrode for ballast water electrolysis. The method of claim 1, wherein the coating layer forming step is formed by purging a mixed gas of argon and oxygen in a vacuum chamber and evaporating the titanium target using plasma at a temperature of 300°C to 400°C to deposit titanium oxide on the surface of the titanium electrode. A method of manufacturing a titanium dioxide-coated catalyst electrode for ballast water electrolysis, comprising the step of: According to claim 1, wherein the step of forming the mixed metal oxide catalyst layer is ruthenium (Ru), palladium (Pd), titanium (Ti), tin (Sn), iridium (Ir), platinum (Pt), tantalum (Ta), anti After applying a coating solution in which two or more kinds of metal ions selected from the group consisting of mono (Sb) and manganese (Mn), an organic solvent and a binder solution are mixed, the method comprising the step of heat-treating, for ballast water electrolysis A method for manufacturing a titanium dioxide coated catalyst electrode. [Claim 4] The method of claim 3, wherein the mixed metal oxide catalyst layer contains ruthenium (Ru) and palladium (Pd) in an atomic ratio of 1 to 10:1. . The method of claim 1, wherein the titanium electrode is a general plate, a regular perforated network, a perforated net, an expanded wire mesh or a mesh type, a method of manufacturing a titanium dioxide-coated catalyst electrode for ballast water electrolysis. The method of claim 3, wherein the binder solution is selected from the group consisting of titanium methoxide, titanium ethoxide, titanium propoxide and titanium butoxide. A titanium dioxide coating catalyst electrode for ballast water electrolysis, manufactured by the method of any one of claims 1 to 6, and comprising a titanium electrode, a titanium dioxide coating layer formed on the titanium electrode, and a mixed metal oxide catalyst layer formed on the coating layer .

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