KR20060018751A - Photocatalyst coating layer and method of making the same with non-thermal plasma - Google Patents

Abstract

According to the present invention, the photocatalyst coating film is made of a photocatalyst material and is subjected to low temperature plasma treatment so as to be activated by visible light. The method of treating the photocatalyst coating film includes a first step of mounting a gas on which a photocatalyst coating film is formed in a chamber of the plasma generator; And a third step of injecting a plasma gas into the chamber, and a third step of surface treating the photocatalyst coating layer using a low temperature plasma generated by the plasma generator to react with visible light.

Photocatalyst, low temperature plasma, reforming

Description

Photocatalyst coating layer and method of making the same with non-thermal plasma}

1 is a cross-sectional view showing a plasma generating apparatus according to the present invention,

2 to 12 are graphs showing the results of methylene blue decomposition experiments by irradiating light using UV-A, UV-C, fluorescent lamps treated with a low temperature plasma treatment of the photocatalyst coating film using a plasma gas,

13A, 13B, 14A, 14B, 15A, 15B, 16A, and 16B are graphs showing the results and absorbance of methylene blue decomposition experiments of a low-temperature plasma-treated photocoated film while varying a plasma gas. .

The present invention relates to a photocatalyst coating film, and more particularly, to a photocatalyst coating film capable of activating a photocatalyst by visible light, and a surface treatment method of a photocatalyst coating film using a low temperature plasma.

Recently, photocatalytic thin bodies using titanium oxide have attracted attention. A photocatalyst is a substance which has semiconducting physical properties and becomes excited when light having energy greater than the bandgap energy of the conducting electron band and the lower electron band is irradiated, thereby generating an electron-hole pair. In titanium oxide having an anatase type crystal structure, when light having a wavelength of 387 nm or less is irradiated, it is photoexcited to cause a decomposition reaction based on a redox reaction and a hydrophilization reaction different from the decomposition reaction (activity). At the present time, titanium oxide, tin oxide and zinc oxide are known as metal oxides which cause these two reactions simultaneously, and as metal oxides causing only a decomposition reaction, strontium titanate and ferric oxide cause only a hydrophilization reaction. Tungsten trioxide is known as a metal oxide.

By using these actions, self-cleaning action, deodorizing action, antibacterial action and the like can be obtained, and various members and product groups coated with a photocatalyst have been proposed.

As a manufacturing method of such a photocatalyst, various methods, such as a binder method, a sol-gel method, and a vacuum vapor deposition method, are proposed. The binder method is a method of dispersing fine titanium oxide in an adhesive binder and applying it on a predetermined substrate, followed by heat drying. However, this method has a problem that the photocatalytic action is liable to be impaired because the particulate titanium oxide is embedded between the binders.

In addition, the sol-gel method is a method of obtaining a photocatalyst film by apply | coating liquid agents, such as titanium chelate and titanium alkoxide, containing titanium on a predetermined | prescribed gas, drying, and baking at high temperature 500 degreeC or more. However, since the high temperature baking process of 500 degreeC or more is required, there exists a problem that what can be used as a gas from the point of heat resistance becomes extremely limited. For this formation method, a formation method using a vacuum deposition method or a sputtering method has been proposed.

However, since the photocatalyst as described above has a relatively large bandgap energy (3.2 eV, anatase type crystal structure), these functions are mainly shown in the ultraviolet (UV) region. This limitation is subject to many limitations in applying the photocatalyst in real life. Therefore, in order to use photocatalysts more efficiently in daily life, researches on photocatalysts reacting with visible rays forming most of solar rays have been made. On the other hand, a method of modifying the photocatalyst includes a method of doping a metal on the surface, a method of doping a transition metal, a method of making a composite semiconductor, a method of doping a photosensitive material. In the method of doping the transition metal, titanium dioxide doped with the transition metal is known to react in visible light and increase efficiency, but is thermally unstable at high temperature, and due to the increase in the recombination portion of the electron-electron pair, Degradation has been pointed out as a problem.

On the other hand, it is disclosed that the coating of TiC on TiO 2 by plasma CVD can improve the catalytic activity by ultraviolet rays, but it is difficult to expect a satisfactory effect.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a photocatalyst coating film which is activated by ultraviolet excitation light and can be excited by visible light and a photocatalyst coating film surface treatment method using low temperature plasma. .

Another object of the present invention to provide a photocatalyst coating film and a photocatalyst coating film surface treatment method using a low-temperature plasma to improve the photocatalytic activation and the reaction by the visible light of the photocatalyst coating film prepared by the sol-gel method.

Photocatalyst coating film of the present invention for achieving the above object,

It is made of a photocatalyst material and characterized in that the low-temperature plasma treatment to be activated by visible light.

In the present invention, it is preferable to use titanium oxide as the photocatalyst material.

A method for surface treatment of a photocatalyst coating film using a low temperature plasma for achieving the above object includes a first step of mounting a substrate on which a photocatalyst coating film is formed in a chamber of a plasma generator, and a second step of injecting a plasma gas into the chamber of the plasma generator; And a third step of surface treating the photocatalyst coating film using a low temperature plasma generated by the plasma generator to react in visible light.

 In the present invention, the plasma gas is preferably hydrogen and argon gas, or the plasma gas is nitrogen and argon gas or hydrogen and nitrogen gas.

Hereinafter, a preferred embodiment of the surface treatment method of the photocatalyst coating film and the photocatalyst coating film using a low temperature plasma according to the present invention will be described in detail with reference to the accompanying drawings.

The photocatalyst coating film according to the present invention is coated with a sol gel method of titanium oxide, a photocatalytic material, on the surface of a substrate, and is a low-temperature plasma surface treatment to react in visible light. Here, the titanium oxide (TiOa 2) is preferably used having a crystal structure of rutile or anatase.

1 shows a plasma generator for surface treatment of a photocatalyst coating film using a low temperature plasma.

Referring to the drawings, the plasma generating apparatus 10 is connected to the vacuum chamber 11, the vacuum chamber 11, the vacuum pump 12 for vacuuming the interior of the chamber, and the inside of the vacuum chamber 11 A pair of electrodes 13 and 14 arranged to be spaced apart from each other by a predetermined interval, an RF plasma generator 15 for supplying electric power to the electrodes 13 and 14 to generate plasma, and the vacuum The chamber 11 includes a gas supply pipe 16 for supplying argon, hydrogen, nitrogen, oxygen, and the like, each of which is connected to each gas tank. The vacuum chamber 11 is provided with a pressure gauge 17 for measuring the pressure of the gas. In addition, although not shown in the drawing, the vacuum chamber 11 may further include a heater and cooling means (not shown) for controlling the temperature of the inside of the vacuum chamber and the gas during plasma discharge. Here, the plasma generating apparatus is not limited to the above-described embodiment, and any plasma structure can be used as long as it can perform a low temperature plasma treatment on the plasma coating film formed on the surface of the substrate.

In order to modify the coated photocatalyst coating film of the substrate using the plasma generator 10 having the above configuration, the first step of mounting the substrate on which the photocatalyst coating film is formed in the vacuum chamber is performed.

Then, hydrogen gas and argon gas, argon gas and nitrogen gas, oxygen or hydrogen gas and nitrogen gas are selectively supplied to the inside of the vacuum chamber 11 through the gas supply pipe 16, and the RF plasma generator 16 A low temperature plasma is generated between the electrodes. And using this to perform a step of modifying the surface of the photocatalyst coating film. 13.56 MHz was used as the plasma generator 16, and the output at this time is preferably 100 to 300W. If the output is less than 100W, it is difficult to obtain the effect of surface modification, and if it exceeds 300W, corona discharge may occur and damage of the photocatalyst coating layer may occur.

In addition to the above-described RF plasma generator 16, it is preferable that the present invention can also be achieved by using an AC generator, a DC generator, or the like.

On the other hand, the plasma gas is preferably hydrogen gas and argon, or argon gas and nitrogen, nitrogen gas and hydrogen gas. The use of other neon, helium, or the like as the plasma gas is difficult to achieve the effect of surface modification, and when using a gas having a large atomic weight or molecular weight is undesirable because it may cause physical damage to the surface. In the surface modification step of the photocatalyst coating film, the pressure inside the vacuum chamber is preferably in the range of 100 mTorr to 300 mTorr, but when it is less than 100 mTorr, corona discharge may occur, and in the case of more than 300 mTorr, an average free path. It is not preferable because) is shortened and plasma is hardly formed.

Hereinafter, the present invention will be described in more detail with reference to Examples, which are only presented to aid the understanding of the present invention, but the present invention is not limited thereto.

Experimental Example 1

In order to modify the photocatalyst coating film using a plasma generator in FIG. 1, titanium oxide was coated on a 7.5 x 2.5 cm 2 slide glass surface using a dip coating machine at a rate of 8 mm / s, and then fired at 50 ° C. for 1 hour. The specimen was mounted inside the vacuum chamber of the plasma generator. Hydrogen gas and argon gas were supplied to the inside of the vacuum chamber at a pressure of 100 mtorr, and the output of the RF plasma generator was plasma treated at 200W for 30 minutes.

Experimental Example 2

The titanium oxide photocatalyst coating film was subjected to a low temperature plasma treatment in the same manner as in Example 1 except that the plasma catalyst nitrogen and argon were used to modify the photocatalyst coating film.

Experimental Example 3

When the photocatalyst coating film was modified, hydrogen gas and argon gas, which were plasma gases were supplied to the inside of the vacuum chamber at a pressure of 200 mtorr, and the output of the RF plasma generator was plasma treated at 300W for 30 minutes, which was the same as in Example 1. The photocatalyst coating film was subjected to low temperature plasma treatment.

Experimental Example 4

When the photocatalyst coating film was modified, the photocatalyst was prepared in the same manner as in Example 1 except that the oxygen gas, which was a plasma gas, was supplied at a pressure of 100 mtorr, and the output of the RF plasma generator was plasma treated at 200 W for 60 minutes. The coating film was subjected to low temperature plasma treatment.

As described above, after modifying the photocatalyst coating film of each specimen by plasma surface treatment, methylene blue decomposition experiment was performed to evaluate the photocatalyst coating film. The methylene blue solution used in the activity evaluation of the photocatalyst coated horse was diluted to a concentration of 5ppm. 50ml was added to the petty tissue and placed in a UV lamp reactor to irradiate light with UV-visible at 1 hour intervals. Shimazu UV-visible sepectrophotometer 16012450) was used to measure the concentration of methylene blue. The UV lamp used in the test was a 15W UV-A lamp and UV-C lamp (manufactured by SANKYO DENKI). And after irradiating light using a fluorescent lamp, the methylene blue concentration was measured.

As described above, through the decomposition experiment of methylene blue, the results of the graphs as shown in FIGS. 2 to 12 were obtained.

As shown in FIG. 2 to FIG. 7, the low-temperature plasma treatment using hydrogen gas, argon number, nitrogen gas, and hydrogen gas as the plasma gas increases activity in both UV-A and fluorescent lamps. In particular, when hydrogen gas and argon gas are used, oxygen vacancy is formed between the conduction band and the valence band of the photocatalyst, and thus, photocatalytic activation is expected to occur even with a smaller energy.

As shown in FIGS. 8 to 10, when nitrogen and argon are used as the plasma gas, the effect of oxygen deficiency and nitrogen may be overlapped to increase photocatalytic activity even in visible light.

As shown in FIGS. 11 and 12, when oxygen is used as the plasma gas, decomposition of methylene blue proceeds continuously. This is because carbon or impurities on the surface of the photocatalyst coating layer are removed by oxygen plasma treatment, and pure oxidation is performed. It is believed that titanium remains and the electron-hole pairs have been used for photocatalytic decomposition more efficiently.

13A to 16B are graphs showing the absorbance of the photocatalyst coating film according to the low temperature plasma surface treatment. It can be seen that the red shift phenomenon appears under all these conditions, and the larger the red shift, the higher the activity of the photocatalyst. In particular, the peaks of nitrogen gas and argon gas were changed at 365 nm. In the photocatalytic activity evaluation, the activity of UV-A was lower than that of the photocatalyst coating layer without low-temperature plasma surface treatment, but the photocatalytic activity was more visible in visible light. Appeared good.

As described above, the photocatalyst coating film surface-treated using a low temperature plasma was found to increase the chemical conversion of the photocatalyst by ultraviolet light, and the reaction of the photocatalyst which was not reacted in visible light was large. In particular, the photocatalyst coating film according to the present invention can be applied in various fields using visible light activity.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible.

Therefore, the true scope of protection should be defined only by the appended claims.

Claims (6)

A photocatalyst coating film made of a photocatalyst material and subjected to low temperature plasma treatment to be activated by visible light. The method of claim 1, The photocatalyst coating film, characterized in that the photocatalyst material is made of titanium oxide. The method of claim 2, The photocatalyst coating film, characterized in that the titanium oxide is an anatase type or rutile type. A first step of mounting the gas on which the photocatalyst coating film is formed in the chamber of the plasma generator, Injecting a plasma gas into the chamber of the plasma generator; And a third step of surface treating the photocatalyst coating film using a low temperature plasma generated by the plasma generator to react with visible light. The method of claim 4, wherein The plasma gas is a surface treatment method of the photocatalyst coating film, characterized in that hydrogen and argon gas. The method of claim 4, wherein The plasma gas is a surface treatment method of a photocatalyst coating film, characterized in that one of nitrogen and argon gas, hydrogen and nitrogen gas, oxygen gas.

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