KR101855747B1 - Manufacturing of visible-light active photocatalyst titanium dioxide and titanium dioxide manufactured therefrom - Google Patents

Abstract

A method for manufacturing visible light-sensitive titanium dioxide is disclosed. The method for manufacturing the visible light-sensitive titanium dioxide according to the present invention comprises: a step (S100) for mixing boron-based hydride or aluminum-based hydride with titanium dioxide; and a step (S200) for reducing the titanium dioxide through heat treatment. The present invention aims to provide the method for manufacturing the visible light-sensitive titanium dioxide in which an oxidation-reduction reaction is performed by the visible light, and to a titanium dioxide photocatalyst.

Description

Technical Field [0001] The present invention relates to a method for producing visible light-sensitive titanium dioxide, and a titanium dioxide prepared from the method. [0001] The present invention relates to a method for producing visible light-

The present invention relates to a process for producing titanium dioxide which is sensitive to visible light and titanium dioxide produced therefrom.

The photocatalyst material reacts to the decomposition of harmful substances when it receives light. The electrons excited from the valence band to the conduction band by the light and the holes formed in the valence band exhibit a strong oxidation or reduction action. Examples of the material exhibiting such an oxidation or reduction action include TiO2, ZnO, Nb2O5, SnO2, ZrO2, CdS, ZnS, CdSe, GaP, and CdTe.

Among these, TiO ₂ itself can be used semi-permanently because its characteristics do not change even if it receives light itself. However, ZnO or CdS itself is decomposed by light and generates harmful Zn and Cd ions.

In addition, titanium dioxide decomposes all organic materials into CO ₂ and H ₂ O, but WO ₃ has only good photocatalytic efficiency for certain materials, and other materials are much lower in efficiency than titanium dioxide, which limits its use. In addition, titanium dioxide is excellent in durability and abrasion resistance, has no change in its own properties, is environmentally friendly, and has no concern about secondary pollution even if it is disposed of.

On the other hand, the band gap or forbidden band energy (Eg) of the anatase type titanium dioxide is 3.23 eV, and the rutile type titanium dioxide is 3.02 eV. Since the wavelengths are 388 nm and 413 nm, respectively, the wavelengths are substantially unreactive at 400 nm to 800 nm in the visible light region and react at 270 nm to 400 nm in the ultraviolet region. In the case of sunlight, about 5% reaching the surface is ultraviolet, and about 40% is known as visible light. The titanium dioxide thus commercialized reacts with ultraviolet rays, so the catalytic efficiency is low. The catalyst efficiency can be relatively high if it can be reacted by visible light which occupies 40% of the sunlight.

In order to activate the photocatalytic activity of conventional visible light, a method of doping titanium dioxide with a metal or a nonmetal such as transition metal, nitrogen, carbon, sulfur, phosphorus, or fluorine has been mainly used. However, the above method is sensitive to solar irradiation but still lacks absorption in visible light.

For this purpose, ion implantation, sputtering, and heat treatment of high temperature gas heat treatment, which are basically costly processes, are used. These methods have the problem that the unit cost of manufacturing the visible light-sensitive titanium dioxide photocatalyst is greatly increased It is holding.

On the other hand, X. B Chen et al. First reduced titanium dioxide to hydrogen gas in high temperature and high pressure environments to form disordered layers on the surface of titanium dioxide [Xiaobo Chen, Lei Liu, Peter Y. Yu and Samuel S. Mao , "Increasing Solar Absorption for Photocatalysis with Black Hydrogenated Titanium Dioxide Nanocrystals" Science, vol.331, no.6018 (2011) pp.746-750]. As a result, the visible light response and photocatalytic efficiency are increased as compared with the conventional white titanium dioxide, and various conditions for the hydrotreated titanium dioxide according to the present method are known. However, the use of hydrogen gas in an ultra-high temperature and high-pressure environment is very dangerous in industrial production and requires a long reaction time.

 Therefore, it is required to develop a photocatalyst exhibiting a high photocatalytic activity in the visible light region through a novel manufacturing method which will replace the conventional technique.

Titanium dioxide-based photocatalyst having visible light-sensitive characteristics of Patent Document 1-2013-0042390 and method for producing the same A crystalline titanium dioxide core-crystalline titanium dioxide photocatalyst in the form of amorphous titanium dioxide shell of Patent Registration No. 10-1265781, a process for preparing the same, and a hydrophilic coating agent containing the titanium dioxide photocatalyst Patent Document 10-2017-0002285 discloses a method for enhancing solar energy conversion efficiency using a metal oxide photocatalyst having a core-shell energy band structure for ultraviolet and visible light absorption, and a photocatalyst A method of synthesizing titanium dioxide photocatalyst in which crystal structure is transformed by low-temperature heat treatment of Patent Registration No. 10-0769481

The present invention provides a method for producing visible-light-sensitive titanium dioxide in which an oxidation-reduction reaction is performed by visible light, and a titanium dioxide photocatalyst.

Another object of the present invention is to provide a titanium dioxide photocatalyst and a process for producing visible titanium dioxide at a temperature lower than the conventional temperature of 500 ° C or higher.

The problems to be solved by the present invention are not limited to the above-mentioned problems. Other technical subjects not mentioned will be apparent to those skilled in the art from the following description.

The method for producing visible light-sensitive titanium dioxide according to the present invention comprises the steps of mixing a boron-based hydride or an aluminum-based hydride with titanium dioxide (S100), reducing the titanium dioxide through heat treatment (S200) And washing and drying titanium (S300).

The boron-based hydride M [BH _4] has a structure of _n, n = If = 1 and M is Li, Na, K, Ru, Cu, Ag, Cs, NH 4 and, n = time 2 days M is Be M is Ti, Ga, In, Ce, LiMn when n = 3, and M is Ti, Zr, Sn, NaMn and combinations thereof when n = The material selected from the group consisting of NH ₃ BH ₃ ,

The aluminum-based hydride M [AlH _4] has a structure of _n, n = If = 1 and M is Li, Na, K, Ru, Cu, Ag, Cs, NH 4 and, n = time 2 days M is Be M is Ti, Ga, In, Ce, LiMn when n = 3, and M is Ti, Zr, Sn, NaMn and combinations thereof when n = ≪ / RTI >

Titanium dioxide according to the present invention uses P-25 type titanium dioxide, anatase alone and rutile titanium dioxide, which are mixed with anatase and rutile phases, and materials mixed with titanium dioxide and metals, carbon, and oxides.

Meanwhile, in the mixing step and the heating reaction step, a solution containing water or a solvent is prepared in order to increase the reaction rate, and the solution is synthesized through heat treatment. The heat treatment is performed in an inert gas atmosphere, and the inert gas is argon, neon , Helium, nitrogen, oxygen, hydrogen, and combinations thereof.

Further, the cleaning process according to the present invention is a process for removing impurities on the reduced titanium dioxide, and may be selected from the group consisting of water, ethanol, an acid solution, an organic solvent, and combinations thereof.

According to the present invention, there is no need to react using a conventional high temperature, high pressure, and hydrogen gas of 500 degrees or more, and the visible titanium oxide can be easily and simply obtained in a shorter time without a long reaction time of 24 hours or more.

Accordingly, a visible light-sensitive titanium dioxide photocatalyst can be obtained in a short manufacturing process and a relatively low temperature atmosphere, which is advantageous in that economical efficiency and mass productivity can be secured.

1 shows a process for producing visible light-sensitive titanium dioxide according to the present invention.
Figure 2 is a diagram showing the photoactive mechanism of reduced titanium dioxide.
3 is an image of an image of P-25 titanium dioxide and titanium dioxide obtained according to Examples 1 to 4 of the present invention.
FIG. 4 is a graph comparing the absorbance of titanium dioxide of P-25 type with the titanium dioxide obtained according to the manufacturing process of Example 1 of the present invention using a UV-Vis spectrophotomer (JASCO, V650).
5 is an X-ray diffraction (X-ray) chart of the titanium dioxide obtained according to the manufacturing process of the present invention which was heat-treated at 300 deg., 400 deg. And 500 deg. For the same time (60 min) as the titanium dioxide of the P- diffraction; Ultima IV, Rigaku).

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described in the present invention can be modified into various forms, and the scope of the present invention is not limited to the embodiments described below.

1 shows a process for producing visible light-sensitive titanium dioxide according to the present invention.

The process for producing visible light-sensitive titanium dioxide according to the present invention comprises the steps of mixing a boron-based hydride or an aluminum-based hydride with titanium dioxide (S100), heating the mixture in an inert gas atmosphere to obtain reduced titanium dioxide S200), and washing and drying the reduced titanium dioxide (S300).

The present invention does not limit the starting material of the titanium dioxide photocatalyst. P-25 type titanium dioxide, anatase alone, and rutile alone titanium dioxide in which anatase and rutile phases are mixed can be used, and they can be mixed with other materials such as metals, carbon, oxides and the like and used as a starting material.

A boron-based hydride or an aluminum-based hydride is used to reduce titanium dioxide (TiO ₂ ). The boron-based hydride or the aluminum-based hydride serves as a reducing agent for reducing titanium dioxide. The titanium dioxide is reduced through heat treatment, and the color of the titanium dioxide is reduced from conventional white to blue or black (black) series.

The boron-based hydride and the aluminum-based hydride react through the heat treatment as follows.

_{TiO 2 + M [BH 4]} n → TiO 2-x + 2nH 2 + MBO x

_{TiO 2 + M [AlH 4]} n → TiO 2-x + 2nH 2 + MAlO x

In the case of titanium dioxide reduced through the present invention, the surface is converted into an amorphous form, which generates Ti ³⁺ ions accompanied by oxygen vacancy, which contributes to improvement of visible light response and photocatalytic efficiency. These defects improve the visible light sensing efficiency by forming a mid-gap level in the energy band-stop band (forbidden band).

In addition, the amorphous surface shifts the valence band to reduce the bandgap and increase the visible light-sensitive activity.

The oxygen vacancies of the synthesized reduced titanium dioxide increase with increasing reaction temperature and reaction time. In the case of excess oxygen vacancy, even though the absorbance to visible light is excellent, The photocatalytic efficiency can be reduced by acting as a recombination center of the photocatalyst.

According to the present invention, titanium dioxide and the boron-based hydride or the aluminum-based hydride as the reducing agent are sufficiently mixed to obtain a mixed powder.

Mixing may be performed using equipment such as milling, mixer, etc., but is not limited thereto.

Then, the mixed titanium dioxide and the reducing agent are subjected to heat treatment to reduce the titanium dioxide. The heat treatment may be performed in an inert gas atmosphere. The inert gas may be selected from the group consisting of argon, helium, neon, nitrogen, hydrogen, and combinations thereof. At this time, the heating temperature is gradually increased from room temperature to 250 to 400 ° C. The temperature can be raised at a rate of 10 to 15 DEG C / min.

Then, a cleaning process is performed to remove impurities contained in the reduced TiO ₂ powder. The cleaning process may be selected from the group consisting of water, ethanol, acid solution, organic solvent, and combinations thereof.

For example, when sodium borohydride (NaBH ₄ ) is used as a reducing agent, by-product remaining after heat treatment is dissolved in water, it can be washed by water treatment to remove by-products. However, when a small amount of boron-based byproducts reacts with the surface of the reduced titanium dioxide, it remains insoluble in water, thereby reducing the specific surface area (BET) of titanium dioxide, thereby reducing the efficiency of the photocatalyst. In this case, by-products can be removed by pickling treatment to improve the specific surface area.

Finally, after the cleaning process, the drying process is continued to obtain the reduced titanium dioxide. The drying process of the drying process may be performed at about 30 ° C to about 100 ° C, preferably at about 60 ° C to about 80 ° C.

In the process for producing visible light-sensitive titanium dioxide according to the present invention, a reducing agent and titanium dioxide are mixed in a powder state and synthesized through heat treatment. However, in order to increase the reaction rate, a reducing agent and titanium dioxide are mixed with water or a solvent And then heat-treated.

The titanium dioxide thus reduced has a narrow band gap. As a result, it can be used as a photocatalyst which reacts with visible light which occupies most of sunlight.

Hereinafter, a manufacturing process of visible light-sensitive titanium dioxide will be described with reference to examples.

≪ Example 1 >

5 g of titanium dioxide (TiO ₂ ) of the P-25 type and 1.8 g of sodium borohydride (NaBH ₄ ) were mixed and reacted at 300 ° C. for 60 minutes under an inert gas atmosphere of Ar at a heating rate of 10 ° C./min.

After the reaction, the mixed powder was added to water, washed with stirring for about 1 hour, and then washed again with ethanol. Purification and filter treatment were performed to obtain a powder,

The obtained powdery powder was dried in an oven at 70 DEG C for 1 hour to finally obtain titanium dioxide. The obtained powder had little difference from the amount of the powder added at 4.8 g.

≪ Example 2 >

The reaction was carried out under the same conditions as in Example 1, but the reaction was carried out at 400 ° C for 30 minutes.

≪ Example 3 >

The reaction was carried out under the same conditions as in Example 1, but the reaction was carried out at 400 ° C for 60 minutes.

<Example 4>

The reaction was carried out under the same conditions as in Example 1, but the reaction was carried out at a temperature of 500 ° C. for 60 minutes.

Fig. 3 is an image of titanium dioxide (white) of P-25 type as a starting material and titanium dioxide (black) obtained according to Examples 1 to 4 of the present invention.

FIG. 4 is a graph comparing the absorbance of titanium dioxide of P-25 type with the titanium dioxide obtained according to the manufacturing process of Example 1 of the present invention using a UV-Vis spectrophotomer (JASCO, V650).

It can be seen that the obtained titanium dioxide significantly increased the absorption of light in the visible region and also increased the absorbance in the UV region than the titanium dioxide before the reaction.

5 is an X-ray diffraction (X-ray) chart of the titanium dioxide obtained according to the manufacturing process of the present invention which was heat-treated at 300 deg., 400 deg. And 500 deg. For the same time (60 min) as the titanium dioxide of the P- diffraction; Ultima IV, Rigaku).

Compared with the crystalline phase of titanium dioxide of the P-25 type before the reaction, the crystal phase of the titanium dioxide obtained is not largely changed, but the shape of the peak is broadened due to the irregular surface. It can also be seen that as the temperature increases, the rutile phase peak around 27 DEG gradually decreases. 5 is that the time condition of the second embodiment is 30 minutes.

The specific surface area (BET, m ² / g) before the HCl washing The specific surface area after the pickling (BET, m ² / g) Example 1 48 50 Example 2 49 49 Example 3 45 51 Example 4 43 52

<Table 1> shows the results of pickling with 1M 100 mL hydrochloric acid (HCl) aqueous solution separately, followed by washing with water three times. The change in the specific surface area (BET: Micromeritics asap2020) of the titanium dioxide powder obtained after drying was analyzed. In Examples 1 and 2, there was no significant change in the specific surface area before and after pickling, but in Examples 3 and 4, the specific surface area decreased due to removal of by-products present on the surface was found to increase . By increasing the specific surface area, the photocatalytic effect of titanium dioxide can be improved. For reference, the specific surface area (BET) of P-25 is 49 m ² / g.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the present invention is not limited to the disclosed exemplary embodiments, but various changes and modifications may be made by those skilled in the art without departing from the scope of the present invention.

Claims (8)

Mixing the boron-based hydride with titanium dioxide,
And reducing the titanium dioxide through heat treatment,
When the boron-based hydride M [BH _4] has a structure of n, n = 1 il, M is Li, Na, K, Ru, Cu, Ag, Cs, NH 4 and, n = time 2 days, M M is Ti, Ga, In, Ce, and LiMn; when n = 4, M is Ti, Zr, Sn, and NaMn; material selected from the group consisting of the combination and contains NH ₃ BH _3,
Wherein the heat treatment has a rate of temperature raising of 10 to 15 占 폚 / min until the temperature reaches 250 to 400 占 폚 at room temperature.
delete Mixing the aluminum-based hydride with titanium dioxide,
And reducing the titanium dioxide through heat treatment,
M is Na, K, Ru, Cu, Ag, Cs, NH4 when n = 1 and M is at least one element selected from the group consisting of Be, Mg , M is Ti, Ga, In, Ce, LiMn when n = 3, M is Ti, Zr, Sn, NaMn and combinations thereof when n = Lt; RTI ID = 0.0 &gt; a &lt; / RTI &gt;
Wherein the heat treatment has a rate of temperature raising of 10 to 15 占 폚 / min until the temperature reaches 250 to 400 占 폚 at room temperature.
The method according to claim 1,
Wherein the titanium dioxide is a mixture of P-25 type titanium dioxide, anatase alone and rutile titanium dioxide, in which anatase and rutile phases are mixed, and titanium dioxide and a metal, carbon and oxide mixed with visible light. &Lt; / RTI &gt;
The method according to claim 1,
Wherein the heat treatment is performed in an inert gas atmosphere and the inert gas is selected from the group consisting of argon, neon, helium, nitrogen, oxygen, hydrogen, and combinations thereof.
The method according to claim 1,
(S300) washing and drying the reduced titanium dioxide after the step of reducing the titanium dioxide through the heat treatment,
Wherein the cleaning is a process for removing impurities on the reduced titanium dioxide and is selected from the group consisting of water, ethanol, acid solution, organic solvent, and combinations thereof. Way.

delete A reduced titanium dioxide produced by the process according to any one of claims 1, 3, 4, 5, 6.

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