KR101264878B1 - Fabricating method of titanate nanotube containing titanium dioxide - Google Patents

Abstract

(a) reacting titanium dioxide in a strong alkaline aqueous solution to obtain a titanate nanotube powder; And (b) reacting the titanate nanotube powder with a strong acid solution and a titanate adsorbent to obtain a titanium dioxide-containing titanate nanotube having an anatase crystal phase. do.

Description

Fabrication method of titanate nanotube containing titanium dioxide}

The technology disclosed herein relates to a method for producing titanium dioxide-containing titanate nanotubes, and more particularly, to titanate nanoparticles containing anatase particles having good photoactivity in the manufacturing process and without the generation of rutile particles by phase transition. It relates to a method for producing a tube.

Titanate nanotubes are materials that can be applied to various fields such as photocatalysts, solar cells, sensors, and hydrogen storage. Recently, many studies have been conducted to support metal catalysts in order to increase efficiency. Meanwhile, in order to increase the efficiency of conventional titanate nanotubes, a technique of making titanate nanotubes doped with transition metals (Patent No. 10-0850027) and a technique of making titanate nanotubes supported with platinum and palladium metal catalysts (Patent No. 10-0810122) has been reported.

However, the conventional method is characterized in that the platinum or palladium precursor is added to the process of obtaining titanate nanotubes from titanium dioxide (TiO ₂ ) particles so that the platinum or palladium catalyst is dispersed in the titanate nanotubes through hydrothermal synthesis. have. In the existing method, since platinum or palladium catalysts will be dispersed throughout the titanate nanotubes, it is thought that the economic efficiency will be reduced by using a large amount of expensive metal catalysts.

According to one embodiment, (a) reacting titanium dioxide in a strong alkaline aqueous solution to obtain a titanate nanotube powder; And

(b) reacting the titanate nanotube powder with a strong acid aqueous solution and titanate adsorbent to obtain a titanium dioxide-containing titanate nanotube having an anatase crystal phase, thereby providing a method for producing titanium dioxide-containing titanate nanotubes. .

According to another embodiment, there is provided a titanium dioxide-containing titanate nanotube produced by the above-described manufacturing method.

1 is a process flow diagram showing an embodiment of a method for producing a titanate nanotube.
2 is a high-resolution transmission electron microscope (HR-TEM) photograph of titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2 (FIG. 2A: Comparative Example 1 and FIG. 2B: Comparative Example 2 and FIG. 2). 2c Example 1, FIG. 2D Example 2).
FIG. 3 shows X-ray diffractometer (XRD) analysis results of titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2. FIG.
4 shows the results of diffuse reflection spectroscopy (DRS) analysis of titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2. FIG.
5 is a graph comparing the degree of decomposition of methylene blue according to ultraviolet irradiation of the titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2.
6 is a graph comparing the decomposition degree of acetaldehyde according to ultraviolet irradiation of the titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2.

Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings.

1 is a process flow diagram showing an embodiment of a method for producing a titanate nanotube. Referring to FIG. 1, in step S1, titanium dioxide is reacted in a strong alkaline aqueous solution to obtain a titanate nanotube powder. The strong alkaline aqueous solution may be at least one aqueous solution selected from the group consisting of LiOH, NaOH, and KOH. The titanium dioxide used can be in the form of a powder and usually have a diameter of 2 to 100 nm. The powder of titanium dioxide may be stirred in a reflux reactor for a predetermined time by applying heat in the strong alkaline aqueous solution. The titanium dioxide powder may be immersed in a strong alkaline aqueous solution having a concentration of 5 to 20M, preferably 8 to 15M, and then refluxed at a temperature of 50 to 180 ° C. for 10 to 60 hours. When the concentration of the strong alkali is less than the above range, the reaction time may be long to form the nanotubes, which may be industrially inefficient, and when the concentration exceeds the above range, it may be difficult to obtain a nanotube form. In addition, when the temperature is lower than the temperature, the reaction time is long, and when the temperature is exceeded, it may be difficult to obtain a nanotube form. The titanate nanotubes can be obtained by washing with water after the reaction.

In step S2, the titanate nanotube powder is reacted with an aqueous solution containing a strong acid and titanate adsorbent to obtain titanium dioxide containing titanate nanotubes having an anatase crystal phase. When the titanate nanotubes are treated with the strong acid aqueous solution and stirred in a reflux reactor for a predetermined time, the residual alkali metal in the titanate nanotubes may be removed, and an anatase crystal phase may be generated. The strong acid aqueous solution may be at least one selected from the group consisting of HCl, HNO ₃ , and H ₂ SO ₄ , the concentration may be 0.05 to 5M. When the concentration is lower than the above-mentioned concentration, the reaction time for generating the anatase crystal phase becomes long, and when the concentration is exceeded, only the rutile crystal phase, not the anatase crystal phase, may occur. The reaction is preferably refluxed for 4 to 40 hours at a temperature of 40 to 120 ℃. Below the temperature, the reaction time is long, and when the temperature is exceeded, a phase transition from anatase to rutile may occur.

The titanate adsorbent material may be in the form of a salt and dissociate in an aqueous solution to produce anions that can electrostatically bond with the titanate nanotubes. Specific examples of the titanate adsorbent include salts containing fluorine ion (F-), phosphate ion (PO ₄ ^3- ), silicate ion (SiO ₄ ^4- ), and the like.

Since the titanate nanotubes can be positively charged on the surface in acidity, the titanate adsorption material is adsorbed onto the titanate nanotube surface by electrostatic attraction to prevent recrystallization of the titanate nanotubes and only a part of the titanates. By allowing the transition to the anatase crystal phase, the titanate nanotubes carrying the anatase crystal phase particles can be maintained.

The process of step S2 may be performed by simultaneously reacting the titanate nanotube powder with the strong acid aqueous solution and the titanate adsorbent material. Alternatively, the titanate adsorbent may be reacted with the titanate nanotube powder first, and then the strong acid aqueous solution may be reacted.

According to the above production method, a titanate nanotube having an anatase crystal phase can be obtained by a simple process, and the transition of the crystal phase to rutile can be prevented.

Hereinafter, the disclosed technology will be further embodied by comparative examples and examples, and the following examples are only specific examples and are not intended to limit the protection scope of the disclosed technology.

Comparative Example 1

4 g of titanium dioxide powder (Degussa P25) was added to 200 ml of 10 M NaOH aqueous solution, and a mixed solution was prepared. Next, the mixed solution was refluxed at 120 ° C. for 24 hours to change the titanate powder into a tube structure, and then washed three times or more with water to finally obtain titanate nanotubes.

Comparative Example 2

1 g of the powder of Comparative Example 1 was added to a 100 ml aqueous solution containing 0.1 M HNO ₃ to prepare a mixed solution. The mixed solution was refluxed at 80 ° C. for 24 hours, and then washed three times or more with water.

Example 1

1 g of powder of Comparative Example 1 was dissolved in 0.1 M HNO _3. And it was added to a 100ml aqueous solution containing 0.1M NaF, the mixed solution was refluxed at 80 ℃ for 24 hours, and then washed three times or more with water.

[Example 2]

1 g of powder of Comparative Example 1 was dissolved in 0.1 M HNO _3. And 0.1 M NH ₄ H ₂ PO ₄ was added to a 100 ml aqueous solution. The mixed solution was refluxed at 80 ° C. for 24 hours, and then washed three times or more with water.

2 is a high-resolution transmission electron microscope (HR-TEM) photograph of titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2 (FIG. 2A: Comparative Example 1 and FIG. 2B: Comparative Example 2 and FIG. 2). 2c Example 1, FIG. 2D Example 2). Comparing FIG. 2A and FIG. 2B, it can be seen that the titanate nanotubes of Comparative Example 1 prepared without an acid treatment did not show titanium dioxide in the anatase crystal phase, which mainly contributes to photocatalytic activity. On the other hand, in the case of titanate nanotubes prepared according to Comparative Example 2 subjected to the acid treatment step, it was confirmed that the anatase particles were produced on the nanotubes, and it was also confirmed that rutile particles of several hundred nanometers were produced. This indicates that the acid treatment step produces titanium dioxide particles in anatase or rutile crystals on the existing titanate nanotubes.

Example 1 shown in Figure 2c is prepared by putting NaF at the same concentration, while the acid treatment to the nanotubes of Comparative Example 1 at the same concentration as in Comparative Example 2. Example 2 shown in Figure 2d is prepared by putting the NH ₄ H ₂ PO ₄ in the same concentration while the acid treatment to the nanotubes of Comparative Example 1 at the same concentration as in Comparative Example 2. The biggest difference between Comparative Example 1 and Examples 1 and 2 is the presence or absence of an acid treatment process, and it can be seen that the acid treatment of existing titanate nanotubes results in the formation of an anatase crystal phase known to have good photoactivity. The difference between Comparative Example 2 and Examples 1 and 2 is the presence or absence of surface treatment for titanate nanotubes, and the anatase crystals were applied to the nanotubes of Comparative Example 2 which were carried out according to the existing acid treatment method during the same concentration of acid treatment. In addition to the formation of the phase, it can be seen that the transition to the rutile crystal phase also occurs. On the other hand, in Examples 1 and 2 subjected to acid treatment at the same concentration, anatase crystal phases were produced, and no transition of the crystal phases to rutile was observed. From this, it can be seen that fluorine ions and phosphate ions act on the surface of the titanate nanotubes containing anatase particles, thereby preventing the transition of crystal phases.

FIG. 3 shows X-ray diffractometer (XRD) analysis results of titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2. FIG. The results in FIG. 3 show the crystal phase structure of each titanate nanotube. It can be seen that Comparative Example 2, which had undergone the acid treatment, had a large rutile crystal phase appearing at 27-28 °. On the other hand, Examples 1 and 2, which were subjected to an acid treatment with a surface treatment material, showed the anatase crystal structure appearing at 24-25 °, and the rutile peak of 27-28 ° was not seen. Through this, it can be seen that the acid-treated titanate nanotubes containing the surface treatment material do not undergo crystal phase transition to rutile.

4 shows the results of diffuse reflection spectroscopy (DRS) analysis of titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2. FIG. The absorbance of the diffuse reflectance spectra was plotted by measuring the reflectance and converting it using the Kubelka-munk formula. As shown in FIG. 4, it can be seen that the titanate nanotubes do not absorb light in the visible region, and their ultraviolet absorbances are longer in order of Comparative Example 2, Example 2, Example 1, and Comparative Example 1. You can see that it absorbs light. It is believed that Examples 1 and 2 containing titanium dioxide particles can absorb light of longer wavelengths because the band gap of titanium dioxide is smaller than that of titanate nanotubes, and Comparative Example 2 is titanium dioxide. It is believed that the transition to the rutile phase with lower bandgap can absorb light of the longest wavelength.

Specific surface area analysis results of titanate nanotubes prepared according to Comparative Examples and Examples of the technology disclosed herein are shown in Table 1 below.

 Manufacturing conditions of Comparative Examples and Examples Comparative Example 1 Comparative Example 2 Example 1 Example 2 Specific surface area (m ² / g) 126.2 80.8 151.3 188.2

The acid treatment process of Comparative Example 2 has a lower specific surface area than that of Comparative Example 1, which is a conventional titanate nanotube due to the generation of a rutile crystal phase. On the other hand, in Examples 1 and 2 surface-treated with titanate adsorbents such as NaF and NH ₄ H ₂ PO ₄ , it was confirmed that the anatase crystal phase was formed on existing titanate nanotubes to have a larger specific surface area. Can be.

5 is a graph comparing the degree of decomposition of methylene blue according to ultraviolet irradiation of the titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2. The methylene blue decomposition experiment was carried out by adding 0.05 wt% of each titanate nanotube powder to a 10 μm aqueous solution of 200 μM methylene blue, adjusting the pH, stirring for 30 minutes, and irradiating with UV light over 300 nm for 2 hours. It is a measure of accuracy. From the results shown in FIG. 5, it can be seen that Example 1 and Example 2 which hold | maintain anatase crystal phase have a faster decomposition rate. As can be seen from the results of FIG. 5, it can be considered that the presence of anatase crystal phase having a large specific surface area and high photoactivity has an effect on methylene blue decomposition.

6 is a graph comparing the decomposition degree of acetaldehyde according to ultraviolet irradiation of the titanate nanotubes prepared according to Comparative Examples 1 and 2 and Examples 1 and 2. The decomposition experiment of volatile organic acetaldehyde was made by dispersing each titanate nanotube powder into an aqueous solution of 5 mg / ml concentration, taking 5 ml of it, and drying it. It was carried out in a way to measure. From the results shown in Figure 6 it can be seen that in Example 1 and Example 2, which retained the anatase crystal phase during the acid treatment, it is more advantageous to decompose the volatile organics. This is thought to be the effect of titanate adsorbent material which prevents the anatase crystal phase from transferring to the rutile crystal phase on the surface when acid treated at the same concentration.

According to the above-described manufacturing method, the anatase crystal phase is formed by performing an acid treatment process on the titanate nanotubes, and at the same time, rutile due to acid treatment by adding a titanate adsorption material of NaF and NH ₄ H ₂ PO ₄ to surface treatment The titanate nanotubes having higher photocatalytic function can be prepared by preventing the transition of crystal phases to the phase and maintaining the titanate nanotubes containing the anatase crystal phase with good photoactivity.

In addition, the surface-treated titanate nanotubes containing the high-efficiency anatase titanium dioxide particles produced by the above-described method can be applied to various applications such as photocatalyst field, sensor field, hydrogen storage field and solar cell field. For example, a hydrogen generating device using the anatase titanium dioxide-containing titanate nanotubes as an electrode material, a gas sensing device using the anatase titanium dioxide-containing titanate nanotubes as a gas sensing material, and the anatase titanium dioxide-containing titanate nano It can be applied to filters coated with tubes, textiles and clothes.

Claims (9)

(a) reacting titanium dioxide in a strong alkaline aqueous solution to obtain a titanate nanotube powder; And
(b) reacting the titanate nanotube powder with an aqueous strong acid solution and titanate adsorbent to obtain a titanium dioxide-containing titanate nanotube having an anatase crystal phase,
The titanate adsorbent material is a salt containing at least one of fluorine ion (F ⁻ ), phosphate ion (PO ₄ ^3- ) and silicate ion (SiO ₄ ^4- ). The method according to claim 1,
The strong alkaline aqueous solution is a method for producing titanium dioxide-containing titanate nanotubes are at least one aqueous solution selected from the group consisting of LiOH, NaOH, and KOH. The method according to claim 1,
The concentration of the strong alkaline aqueous solution is a method for producing a titanium dioxide-containing titanate nanotubes of 5 to 20M. The method according to claim 1,
The reaction of step (a) is a method for producing titanium dioxide-containing titanate nanotubes are carried out by refluxing for 10 to 60 hours at 50 to 180 ℃. The method according to claim 1,
The strong acid aqueous solution is a method of producing a titanium dioxide-containing titanate nanotubes of at least one selected from the group consisting of HCl, HNO ₃ , and H ₂ SO ₄ . The method according to claim 1,
The concentration of the strong acid aqueous solution is 0.05 to 5M Titanium dioxide-containing titanate nanotube manufacturing method. The method according to claim 1,
The reaction of step (b) is a method for producing titanium dioxide-containing titanate nanotubes are carried out by refluxing for 4 to 40 hours at 40 to 120 ℃. The method according to claim 1,
The titanate adsorbent material has a salt form and is dissociated in an aqueous solution to produce an anion capable of electrostatically bonding with the titanate nanotubes. Titanium dioxide-containing titanate nanotubes prepared by the method according to any one of claims 1 to 8.

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