KR20080058104A - Method for preparing tio2 photocatalyst using anodic aluminum oxide template and the tio2 photocatalyst prepared by the method - Google Patents

Abstract

A method for preparing a TiO2 photocatalyst is provided to secure a catalyst support by an aluminum anodized film, increase surface area of the catalyst using nano-sized pores on a surface of the aluminum anodized film, and prepare the catalyst without surface defects by performing the heat treatment process of a TiO2 thin film, and a TiO2 photocatalyst prepared by the method is provided. A method for preparing a TiO2 photocatalyst comprises the steps of: electropolishing a thin aluminum sheet in an electrolyte; performing a first anodizing process in an acid solution relative to the electropolished thin aluminum sheet; performing an etching process relative to the first anodized thin aluminum sheet; performing a second anodizing process relative to the etched thin aluminum sheet; and depositing a thin TiO2 film onto a surface of the second anodized thin aluminum sheet. The electrolyte is a solution prepared by mixing ethanol with perchloric acid at a volume ratio of 3:1 to 5:1. The acid solution is an oxalic acid solution, a phosphoric acid solution, a sulfuric acid solution, a chromic acid solution, or mixed solutions thereof. The first and second anodizing processes are performed at a voltage of 30 to 50 V, an electric current of 0.001 to 0.009 A, and a temperature of 5 to 10 deg.C for 15 to 25 hours in the acid solution with a concentration of 0.1 to 1.0M. The etching process is performed at a temperature of 50 to 70 deg.C for 25 to 50 hours in a solution in which phosphoric acid is mixed with chromic acid at a weight ratio of 1:2 to 1:4. Further, the step of depositing a thin TiO2 film is performed by atomic layer deposition.

Description

{Method for preparing TiO2 photocatalyst using anodic aluminum oxide template and the TiO2 photocatalyst prepared by the method}

1 is a view showing a schematic process diagram of a method for producing a TiO ₂ photocatalyst according to the present invention.

FIG. 2 is a view illustrating a deposition process of a TiO ₂ thin film layer by a conventional atomic layer deposition method.

The present invention on aluminum anodic oxide films by relates to a TiO ₂ photocatalyst produced by the production method and the method of the TiO ₂ photocatalyst, more specifically it grows in the form of a very thin and uniform thin film of TiO ₂ on the aluminum anodic oxide film template It is possible to increase the catalyst surface area by using nano-sized pores on the surface of the aluminum anode oxide film, and to produce the crystallinity of the TiO ₂ thin film in a form suitable for catalysis without surface defects through the heat treatment process. production method of the TiO ₂ photocatalyst and a process for the TiO ₂ photocatalyst produced by the method.

The photocatalyst refers to a substance that receives a light to promote a chemical reaction, and examples thereof include a semiconductor, chlorophyll, V ₂ O ₃ , ZnO, ZrO ₂ , perovskite-type composite metal oxide (SrTiO ₃ ), and TiO ₂ . The use of TiO _{2 as} a photocatalyst was discovered by two Japanese scholars in 1967, and it was recognized that TiO ₂ could decompose hardly decomposable organic substances when exposed to ultraviolet rays. . In particular, TiO ₂ is semi-permanent because it does not change even when it receives light, and since most organic substances are oxidized and decomposed into carbon dioxide and water, it is less secondary pollution and effective for removing bleach and odor. Therefore, considering the activity of the oxide film for the above points and photocatalytic reaction, TiO ₂ has emerged as a representative material in the photocatalyst field, and many studies have been conducted.

The decomposition of organic matter by the photocatalyst of TiO ₂ generates electrons and holes when the photocatalyst is irradiated with light energy of more than the band gap energy, and the photocatalyst is formed by the strong oxidizing power of the hydroxyl radical (-0H) produced by them. This is due to an oxidation reaction in which organic substances in a gaseous or liquid phase adsorbed on the surface are decomposed, which will be described in more detail as follows. When the surface of the photocatalytic material is irradiated with UV light having energy above the bandgap of the material, electrons excited and released from the photocatalytic surface react with dissolved oxygen in water to form OH radicals, and at the same time Holes form OH radicals. That is, in the surface of titanium oxide ^{_{TiO 2 + hυ -> e -}} ( generation) + h ⁺ takes place. The reaction of the former is as follows.

e ^_ + O _2- > O ₂ ㆍ ^- (super oxide radical)

And 2O ₂ ^- + 2H ₂ O ^-> ₂ and OH + 2OH ^- + O ₂

In addition, on the surface of TiO ₂ , a reaction such as h ⁺ + OH ^_- > 2 .OH proceeds to decompose harmful organic substances by OH radicals formed.

As a method for using TiO ₂ as a photocatalyst, the prepared TiO ₂ powder is directly used as a photocatalyst, or a binder such as silica is added to TiO ₂ to be applied to a support or a carrier as a coating material, and titanium tetrachloride, titanium alkoxide, and the like. After coating a titanium compound on a support, a method of forming TiO ₂ on the surface of a support using a sol-gel method and the like has been widely known.

In order to use TiO ₂ powder itself as a photocatalyst, powder TiO ₂ mixed with anatase and rutile crystal structures as a primary material must be synthesized through a sulfuric acid method and a chlorine method. The TiO ₂ powder thus prepared is used in the form of a slurry or surface coated on a support. In addition, when TiO ₂ powder is directly used as a photocatalyst for wastewater treatment, a UV lamp is installed inside the photocatalytic reactor, and wastewater and TiO ₂ powder are mixed and used in a slurry form in the reaction cell, depending on the reaction time and throughput of the wastewater. The reaction cells are connected and used. In addition, a catalyst (TiO ₂ powder) recovery device is attached to the reaction cell terminal of the device.

However, in order to recover and recycle the powdered TiO ₂ , a separate device is required and the cost is enormous, which is uneconomical. In addition, a part of the waste water is adsorbed on the surface of the powdered catalyst, thereby decreasing the efficiency of the catalyst. Has problems with surface defects and crystallinity.

Thus, a method of coating or depositing a predetermined support surface using a Ti precursor in the form of a metal alkoxide as a starting material can be considered as a method for preparing a TiO ₂ photocatalyst, in which case TiO ₂ is thin and uniform on the support. There is a need to be able to grow in the form of a thin film and to increase the effective surface area of the catalytic reaction to the maximum.

Accordingly, the first technical problem to be achieved by the present invention is to grow TiO ₂ in the form of a very thin and uniform thin film on the aluminum anode oxide film template to secure the catalyst support by the aluminum anode oxide film, it is possible to use the nano-sized pores to increase the catalyst surface area, through to a heat treatment provides a method for producing TiO ₂ photocatalyst can be produced without surface defects in a form suitable for determination of the TiO ₂ thin film in the catalytic reaction.

In addition, a second technical problem to be achieved by the present invention is to provide a TiO ₂ photocatalyst prepared by the above method.

The present invention to achieve the first technical problem,

Electrolytic polishing the thin aluminum plate in an electrolyte solution;

Performing a first anodization process in an acid solution on the electropolished aluminum sheet;

Performing an etching process on the first anodized aluminum sheet;

Performing the second anodization process on the etched aluminum sheet; And

It provides a method for producing a TiO ₂ photocatalyst comprising depositing a TiO ₂ thin film on the surface of the second anodized aluminum thin film.

According to a preferred embodiment of the present invention, the electrolyte may be a mixed solution of 3: 1 to 5: 1 volume ratio of ethanol and perchloric acid.

According to another preferred embodiment of the present invention, the acid solution may be a solution of oxalic acid, phosphoric acid, sulfuric acid, chromic acid or a mixture thereof.

According to another preferred embodiment of the present invention, the first anodization process and the second anodization process is a voltage of 30V to 50V and a current of 0.001A to 0.009A in the acid solution of 0.1M to 1.0M concentration As a condition, it may be carried out at 5 to 10 ℃ for 15 to 25 hours.

According to another preferred embodiment of the present invention, the etching process may be carried out at a temperature of 50 ℃ to 70 ℃ in a mixed solution of 1: 2 to 1: 4 weight ratio of phosphoric acid and chromic acid.

According to another preferred embodiment of the present invention, the etching process may be performed for 25 to 50 hours.

According to another preferred embodiment of the present invention, the pore diameter of the surface of the aluminum sheet produced by the second anodization process is 10nm to 100nm, the distance between the pores is 80nm to 120nm, the pore depth is 0.5㎛ to 1.5㎛ Can be.

According to another preferred embodiment of the present invention, the deposition of the TiO ₂ thin film may be performed by atomic layer deposition (atomic layer deposition).

According to another preferred embodiment of the present invention, Ti (OCH (CH ₃ ) ₂ ) ₄ is used as the Ti precursor of the atomic layer deposition method, H ₂ O is used as the oxygen source, and Ar is used as the purge gas. Can be used.

According to another preferred embodiment of the present invention, evaporation of the Ti precursor is carried out at a temperature of 60 ℃ to 80 ℃, deposition of the TiO ₂ thin film may be carried out at 150 ℃ to 220 ℃.

In addition, the present invention to achieve the second technical problem,

It provides a TiO ₂ photocatalyst prepared by the above method.

According to the present invention, by using the aluminum anodic oxide film as a support for supporting a TiO ₂ photocatalyst, using a nano-size pores of the aluminum anodic oxide film surface which can dramatically increase the catalyst surface area, of the TiO ₂ thin film by the heat treatment Crystallinity can be produced without surface defects in a form suitable for catalysis.

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

1 shows a schematic process diagram of a method for manufacturing a TiO ₂ photocatalyst according to the present invention. Referring to FIG. 1, the method for manufacturing a TiO ₂ photocatalyst according to the present invention includes an electropolishing step of an aluminum thin plate and a first anode. Five steps of an oxidation step, an etching step, a second anodization step and a TiO ₂ thin film deposition step are included.

That is, in the present invention, an alumina template having nano-sized pores was used as a support for supporting the TiO ₂ photocatalyst. The fabrication of the alumina template was performed by electropolishing an aluminum sheet in an acid solution, followed by first anodization and etching. And a second anodization process. Through this process, an alumina template having nano pores in a regular hexagonal array can be manufactured, and in particular, in the present invention, a support having a more regular nanocylindrical surface is obtained by performing anodization twice. It becomes possible. At this time, the size of the nano-cylinder and the distance between each nano-cylinder can be adjusted by the type of acid used. In addition, by performing an etching process between the first anodization process and the second anodization process, it is possible to form a nano cylinder having a more regular and constant arrangement and shape.

Preferably, the electrolytic solution used for electropolishing of thin aluminum sheet may be an electrolyte solution commonly used in the art, but is not limited thereto, and a mixed solution of 3: 1 to 5: 1 volume ratio of ethanol and perchloric acid may be used. Can be used. In addition, as an aluminum thin plate, an aluminum thin plate of 99% or more, for example, a purity of 99.999% may be used.

As can be seen from FIG. 1, when the electropolishing process for the aluminum sheet is completed, the surface is polished to have surface curvature, thereby obtaining an aluminum sheet suitable for performing the subsequent anodization process. The first anodization process is performed.

Anodizing refers to a surface treatment in which an anode is applied to a metal to be treated and an anode is applied to a metal to be treated, and an oxide film is coated on the metal to be treated. The aluminum oxide film thicker than the natural oxide film produced by polarization is called anodized aluminum oxide.

The oxide film coated by the anodization process improves the corrosion resistance, durability, and adhesion of the metal surface to be treated according to the type of the oxide film, and generally, the surface of the metal to be treated has surface curvature or irregularities. In addition, a solution such as boric acid, phosphoric acid, sulfuric acid, or chromic acid may be used as the treating solution used in the anodizing process. Sometimes classified.

Treatment solutions that can be used in the aluminum anodization process in the present invention include, but are not limited to, solutions of oxalic acid, phosphoric acid, sulfuric acid, chromic acid or mixtures thereof.

In addition, the anodic oxidation process may be performed for 15 hours to 25 hours at 5 ° C to 10 ° C in a treatment solution of 0.1M to 1.0M concentration, at a voltage of 30V to 50V and a current condition of 0.001A to 0.009A. .

When the concentration of the acid solution in the anodic oxidation process is below or above the above range, when the voltage and current are below or above the above range, or when the treatment temperature is below or above the above range, the aluminum foil is cut off. It is not preferable because there is a problem in that it becomes unusable or the size of the pores becomes uneven and the arrangement becomes poor, making it impossible to use as a template.

As described above, in the present invention, an aluminum template is not manufactured by only one anodizing process, but a rough template is prepared by the first anodizing process, etched, and the second anodizing process is performed again. This feature is characterized by the production of aluminum templates having a more regular and precise arrangement.

In performing the etching process after the first anodic oxidation process, the etching process may be performed at a temperature of 50 ° C. to 70 ° C. in a mixed solution of 1: 2 to 1: 4 weight ratio of phosphoric acid and chromic acid.

In addition, the etching process is preferably performed for a time similar to or more than the first anodization step, for example, the etching process may be performed for 25 to 50 hours, but not limited thereto. .

After the above etching process is completed, the pores of the surface are removed to obtain an aluminum template having a predetermined bend or irregularities on the surface, which may be similar in shape to the result of the electrolytic polishing, but bent or uneven portions. The regularity of the arrangement is much better than that of the electrolytic polishing after the completion of the etching process.

Subsequently, after the etching process, a second anodization process is performed on the surface of the aluminum template. The second anodization process may be performed by the same conditions as the first anodization process.

As described above, when subjected to electropolishing, first anodization, etching, and second anodization, an aluminum template having regular nano-sized pores on the surface can be obtained, and by the second anodization The pore diameter of the prepared aluminum sheet surface is 10nm to 100nm, the distance between the pores is 80nm to 120nm, the pore depth may be 0.5㎛ to 1.5㎛.

In the manufacturing method of the TiO ₂ photocatalyst according to the present invention, the final step is a step of growing a TiO ₂ thin film as a catalyst component on the surface of the aluminum template prepared as described above, preferably depositing the TiO ₂ thin film May be performed by atomic layer deposition.

In the present invention, Ti (OCH (CH ₃ ) ₂ ) ₄ may be used as the Ti precursor of the atomic layer deposition method, H ₂ O may be used as the oxygen source, and Ar may be used as the purge gas. In addition, the evaporation of the Ti precursor is carried out at a temperature of 60 ℃ to 80 ℃, the deposition of the TiO ₂ thin film may be carried out at 150 ℃ to 220 ℃.

As shown in the final step of Figure 1 by the above-mentioned procedure, there is a that the TiO ₂ photocatalyst deposited TiO ₂ thin-film layer on the surface of the aluminum template having the nano-pores can be produced, which atom on a conventional flat substrate It is possible to produce a TiO ₂ photocatalyst with an improved reaction surface area based on the same support plane area as compared to forming a TiO ₂ thin film layer by a layer deposition method. For reference, FIG. 2 illustrates a deposition process of a TiO ₂ thin film layer by a conventional atomic layer deposition method.

In addition, the present invention provides a TiO ₂ photocatalyst prepared by the above method in order to achieve the second technical problem.

The TiO ₂ photocatalyst according to the present invention is formed by depositing a TiO ₂ layer as a catalyst component on the surface of an aluminum anodized oxide film having nano-sized pores, which may significantly increase the reaction surface area based on a support having the same planar area. It becomes possible.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are merely to aid the understanding of the present invention, and the scope of the present invention is not limited to the following Examples.

Example

Production Example

According to the invention TiO ₂ Photocatalyst  Produce

Pure aluminum sheet (99.99%, Aldrich) was electropolished in a mixed solution of perchloric acid and ethanol. Subsequently, a first anodization process was performed by oxidizing the aluminum sheet at a constant voltage of 40 V for 21 hours at 7 ° C. in 0.3 M oxalic acid solution. The prepared anodic oxide layer was removed by immersing in a solution of 6 wt% phosphoric acid and 1.8 wt% chromic acid for 25 hours at 60 ° C., and finally, the same conditions as described for the first anodization process were performed. A second anodization process was performed.

TiO ₂ growth experiments were performed using Ti (OCH (CH ₃ ) ₂ ) ₄ (Strem chemicals, 99,9%) as the Ti-source, H ₂ O (purified by Millipore Milli-Q) as the Oxygen source, High purity N ₂ (99.99%) was used as purging gas and carrier gas.

The order of the process was to grow TiO ₂ thin films by repeating H ₂ O / purging / Ti (OCH (CH ₃ ) ₂ ) ₄ / purging / pumping process several times, and the time of each process was 0.5s / 3s / 1s / 3s. It was / 10s.

According to the present invention, TiO ₂ is grown on the aluminum anodic oxide template in the form of a very thin and uniform thin film to secure the catalyst support by the aluminum anodic oxide film, and at the same time, the surface area of the catalyst is made by using nano-sized pores on the surface of the aluminum anodic oxide film. can be increased, and it is possible to provide a TiO ₂ photocatalyst produced by the crystallinity of the TiO ₂ thin film in the manufacturing method and the method of the TiO ₂ photocatalyst can be produced without surface defects in a form suitable for the catalytic reaction through the heat treatment process.

Claims (11)

Electrolytic polishing the thin aluminum plate in an electrolyte solution; Performing a first anodization process in an acid solution on the electropolished aluminum sheet; Performing an etching process on the first anodized aluminum sheet; Performing the second anodization process on the etched aluminum sheet; And A method of manufacturing a TiO ₂ photocatalyst comprising depositing a TiO ₂ thin film on a surface of the second anodized aluminum sheet. The method of claim 1, wherein the electrolytic solution of ethanol and perchloric acid 3: method for producing a TiO ₂ photocatalyst, characterized in that a mixture of a volume ratio of 1: 1 to 5. The method of claim 1 wherein the acid solution is a method for producing a TiO ₂ photocatalyst, characterized in that a solution of oxalic acid, phosphoric acid, sulfuric acid, chromic acid or a mixture thereof. The method of claim 1, wherein the first anodization process and the second anodization process are performed at 5 ° C. under a voltage of 30 V to 50 V and a current condition of 0.001 A to 0.009 A in the acid solution at 0.1 M to 1.0 M concentration. Method for producing a TiO ₂ photocatalyst, characterized in that carried out for 15 to 25 hours at 10 ℃. The method of claim 1, wherein the etching process is one of phosphoric acid and chromic acid: 2 to 1: 4 The method of TiO ₂ photocatalyst, characterized in that is carried out at a temperature of 50 ℃ to 70 ℃ in a mixed solution of a weight ratio. The method of claim 1, wherein the etching process is process for producing a TiO ₂ photocatalyst, characterized in that is carried out for 25 hours to 50 hours. The TiO according to claim 1, wherein the pore diameter of the surface of the aluminum sheet prepared by the second anodization process is 10 nm to 100 nm, the pore distance is 80 nm to 120 nm, and the pore depth is 0.5 μm to 1.5 μm. ₂ photocatalyst production method. The method of claim 1 wherein the deposition of the TiO ₂ thin film process for producing a TiO ₂ photocatalyst, characterized in that is carried out by the ALD (atomic layer deposition). The Ti precursor according to claim 8, wherein Ti (OCH (CH ₃ ) ₂ ) ₄ is used as the Ti precursor in the atomic layer deposition method, H ₂ O is used as the oxygen source, and Ar is used as the purge gas. Method for producing a TiO ₂ photocatalyst. The method of claim 9, wherein the vaporization of the Ti precursor is carried out at a temperature of 60 ℃ to 80 ℃, the deposition method for producing a TiO ₂ photocatalyst, characterized in that is carried out at 150 ℃ to 220 ℃ of the TiO ₂ thin film. TiO ₂ photocatalyst prepared by the method according to any one of claims 1 to 10.

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