KR101290956B1 - Synthesis of TiO2 nanorod-decorated graphene sheets to visible light photocatalyst - Google Patents

Abstract

The present invention relates to the production of a graphene sheet bonded with titanium dioxide nanorods and its application as a photocatalyst reacting to visible light, and a method for growing titanium dioxide nanorods on a graphene oxide layer through a non-hydrolyzed sol-gel reaction. When used as a photocatalyst, it shows high efficiency under visible light, thus suggesting the possibility of application as a next-generation photocatalyst.
According to the present invention, the introduction of the titanium dioxide precursor to the graphene oxide dispersed in the oleyl amine solution induces a non-hydrolyzed sol-gel reaction, and the titanium dioxide nanorods and the graphene sheet can be easily combined in the process without further processing. Has the advantage. Moreover, the titanium dioxide density on the graphene sheet can be easily controlled by changing the concentration of the titanium dioxide precursor. The graphene sheet combined with the uniform titanium dioxide nanorods thus prepared showed better performance than commercialized titanium dioxide particles even in photocatalytic action under visible light.

Description

Synthesis of TiO2 nanorod-coupled graphene sheet and its application as photocatalyst in response to visible light {Synthesis of TiO2 nanorod-decorated graphene sheets to visible light photocatalyst}

The present invention uses a non-hydrolytic sol-gel method (non-hydrolytic sol-gel method), a method for producing a graphene sheet bonded with titanium dioxide (TiO ₂ ) Nanorod (photocatalyst) and a photocatalyst reacting to visible light The present invention relates to a method for preparing a graphene sheet with titanium dioxide having excellent dispersibility through a synthesis reaction of titanium dioxide on a graphene oxide sheet and having high efficiency under visible light. Provide a photocatalyst.

Nanomaterial generally refers to a material having a size between 1 and 100 nanometers, and has a superior physical properties compared to conventional bulk materials due to the large surface area. Among them, titanium dioxide nanoparticles have been applied to applications as photocatalysts due to high efficiency of photoactivity, low cost, non-toxicity, and chemical stability.

In addition, graphene is an atomic-thick carbon sheet made of sp ² bond carbon, and is currently in the spotlight as a composite material with titanium dioxide due to the following advantages. First, the high electrical conductivity of graphene facilitates the separation and transfer of charges, which is advantageous for suppressing charge recombination. Second, two-dimensional planar graphene creates a large surface area and increases reactivity. Third, because of the easy adjustment of the energy bandgap by carbon doping, the absorption region of light is increased to the visible region. Finally, these graphenes have strong adsorption to contaminants because they have strong pi-pie bonds with aromatics of pollutant molecules.

As a conventional method for preparing a titanium dioxide / graphene composite material, a hydrothermal method, a two phase method of reacting at the interface of two solvents, and graphene oxide are obtained from titanium dioxide. UV-reduction method for reducing electrons (self-assembly method using a surfactant) and the like. In general, a hydrothermal synthesis method of inducing a bond between titanium dioxide and graphene through high heat and pressure may be referred to as a manufacturing method most widely used.

However, the production of the titanium dioxide / graphene composite material through such a hydrothermal synthesis method is not easy to manufacture nanoparticles due to the high reactivity of the titanium dioxide precursor, the prepared titanium dioxide does not have a uniform size, Rather than having a shape, the entanglement between nanoparticles occurs to form an aggregate. In addition, since the bond between the titanium dioxide and the graphene sheet is not uniform, it has a bond only in the limited graphene sheet region, thereby limiting the efficient transfer of generated charges.

Therefore, it exhibits high efficiency photocatalytic activity, has a uniform size of titanium dioxide less than 100 nanometers, bonds over the entire graphene sheet, simple experimental method, and reliable titanium dioxide / graph There is a strong demand for a method for producing fin nanocomposites.

An object of the present invention is to grow a titanium dioxide nanomaterial on a graphene oxide sheet using a non-hydrolyzed sol-gel reaction to solve the problems of the prior art at once, graphene combined with a uniform titanium dioxide nanorods It is to provide a method for producing a sheet.

In addition, the technical problem of the present invention is that the graphene sheet combined with the titanium dioxide nanorods is a titanium dioxide / graphene composite material having a high processability and excellent photocatalytic efficiency under visible light compared to the photocatalyst particles according to the prior art To provide.

After numerous experiments and in-depth studies, the inventors have introduced titanium chloride (TiCl ₄ ) into graphene oxide dispersed in oleyl amine, which is different from the known methods. After growing titanium, it was confirmed that the titanium dioxide / graphene composite material was prepared through a crystallization step at a high temperature, and that the produced material was found to significantly improve the photocatalytic efficiency under visible light as compared to the photocatalytic particles used in the present invention. It came.

The present invention is to produce a graphene sheet in which titanium dioxide nanorods are bonded by growing titanium dioxide nanorods on a graphene oxide sheet using a non-hydrolyzed sol-gel method.

Method for producing a graphene sheet with titanium dioxide nanorods according to the present invention is

(A) dispersing graphite oxide in oleylamine using an ultrasonic generator to prepare a graphene oxide solution dispersed in oleylamine;

(B) preparing a graphene oxide sheet in which titanium dioxide in the form of nanorods is combined by adding titanium chloride, a titanium dioxide precursor, to the graphene oxide solution dispersed in the oleylamine; And

(C) the titanium dioxide nanorods comprising the step of drying the graphene oxide sheet combined with the titanium dioxide nanorods, followed by heat treatment to induce crystallinity of titanium dioxide and reduction of the graphene oxide sheet. Method for producing a bonded graphene sheet.

Using a non-hydrolyzed sol-gel method according to the present invention, a method for producing a graphene sheet in which titanium dioxide nanorods are combined is a completely new method that has not been reported so far. Significantly reduce the bonding problem in the limited region of the, it is possible to easily control the titanium dioxide content on the graphene sheet by changing the concentration of the titanium dioxide precursor is introduced. In addition, it is possible to mass-produce graphene sheets combined with titanium dioxide nanorods through an easy manufacturing method. Thus prepared graphene sheet combined with titanium dioxide showed better performance than commercially available titanium dioxide particles in the photocatalytic action under visible light, and is expected to be used as a next-generation high-efficiency photocatalyst for industrial use. .

1 is a transmission electron microscope photograph of a graphene sheet bonded to titanium dioxide nanorods prepared in Example 1 of the present invention;
Figure 2 shows the results of the decomposition of methylene blue over time under visible light of the titanium dioxide nanorods bonded graphene sheet prepared in Example 1 of the present invention compared with commercially available titanium dioxide nanoparticles and titanium dioxide nanorods to be.
Figure 3 is a result showing a photograph of a methylene blue solution with time under visible light of the titanium dioxide nanorods bonded graphene sheet prepared in Example 1 of the present invention.

For graphite oxide used in step (A), using the improved Hummers method (Refer to Hummers W, Offeman R., "Preparation of graphite oxide", Jounal of the American Chemical Society, 80, 1958, 1339). Prepared. Graphite oxide was prepared using a mixture of sulfuric acid and nitric acid for acid treatment of graphite, and a mixture of sodium nitrate and potassium chlorate for efficient acid treatment. It was used together.

The prepared graphite oxide was put in oleyl amine, and the amount of graphite oxide added is preferably 0.05 to 1 parts by weight based on 100 parts by weight of oleylamine.

Graphite oxide solution dispersed in oleyl amine was prepared by dispersing graphite oxide on oleyl amine using an ultrasonic generator, and the temperature at the time of dispersion is not particularly limited but proceeds at a temperature of 1 to 30 ° C. The dispersion time is preferably 2 to 5 hours.

30 mL of the graphene oxide solution prepared in step (B) is heated to a temperature of 300 ° C. in a 100 mL round flask reactor and titanium chloride is added. The addition amount of titanium chloride is preferably 1 to 1.75 parts by volume relative to 100 parts by volume of the graphene oxide solution dispersed by the above method. In the non-hydrolyzable sol-gel reaction, the reaction temperature is preferably 280 to 320 ℃, the temperature is less than 280 ℃, it is difficult to produce nanocrystals of uniform size because the simultaneous nucleation does not occur, it is more than 320 ℃ In this case, vaporization of the oleylamine solvent occurs. The reaction time is appropriate for 10 to 60 minutes, after which the reaction is quenched with toluene. The amount of toluene is preferably 30 to 100 ml, but is not limited thereto. 100 ml of acetone is added to the reaction solution, and oleylamine is removed by centrifugation at 10,000 RPM for 1 hour, and the oleylamine removal process is repeated three or more times.

Graphene oxide combined with titanium dioxide nanorods in step (C) is dried in a vacuum oven at 25 ℃ through a heat treatment in a carbonization furnace undergoes crystallization of titanium dioxide and reduction of graphene oxide. Heat treatment conditions can be 30 to 60 minutes from 300 degreeC to 800 degreeC, and 30 minutes are preferable at 500 degreeC. Heat treatment time

[Example]

Hereinafter, specific examples of the present invention will be described with reference to examples, but the scope of the present invention is not limited thereto.

Example 1

After adding 1 g of natural graphite and 0.5 g of sodium nitrate to a 20 mL sulfuric acid solution, and slowly adding 3 g of potassium permanganate (or potassium chlorate) over 45 minutes while cooling, slowly adding 50 ml of distilled water and raising the temperature to 98 ° C. It can be seen that the color is brown, and as the hydrogen peroxide was added, the color of the solution was changed to yellowish brown. After repeated centrifugation, the supernatant was discarded, washed with distilled water, and finally rinsed with water to give a reddish brown thick graphite oxide solution (slightly gelled), and when dried in a vacuum oven, graphite oxide in the form of a film was obtained. . 0.2 g of the prepared graphite oxide was added to 40 ml of oleylamine, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours, and analyzed using an atomic force microscope, and the thickness was about 1.2 nm. And it can be seen that the plate-shaped graphene having a width of 2 um size is formed.

[Example 2]

0.02 g of graphite oxide was added to 40 ml of oleyl amine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours, and analyzed using an atomic probe microscope. As a result, it was confirmed that the plate-shaped graphene having a thickness of about 1 nm and a width of 1 ~ 2 um size is formed.

[Example 3]

0.05 g of graphite oxide was added to 40 ml of oleyl amine using the same method as in Example 1, and graphene oxide dispersed in oleyl amine was prepared by ultrasonic grinding for 3 hours, and analyzed using an atomic probe microscope. As a result, it was confirmed that the plate-shaped graphene having a thickness of about 1 nm and a width of 1 ~ 2 um size is formed.

Example 4

0.1 g of graphite oxide was added to 40 ml of oleyl amine using the same method as in Example 1, and graphene oxide dispersed in oleyl amine was prepared by ultrasonic grinding for 3 hours, and analyzed using an atomic probe microscope. As a result, it was confirmed that the plate-shaped graphene having a thickness of about 1 nm and a width of 1 ~ 2 um size is formed.

[Example 5]

0.4 g of graphite oxide was added to 40 ml of oleyl amine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours, and analyzed using an atomic probe microscope. As a result, it was confirmed that plate-shaped graphene having a thickness of about 3 nm and a width of 1 to 2 um was formed. When the amount of graphite oxide increased by more than 0.4 g, graphite oxide was not properly dispersed. Could be confirmed.

[Example 6]

0.2 g of graphite oxide was added to 40 ml of oleylamine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 2 hours, and analyzed using an atomic probe microscope. As a result, it was confirmed that the plate-shaped graphene having a thickness of about 1.8 nm and a width of 3 μm was formed. When the ultrasonic grinding time is less than 2 hours, it was confirmed that the dispersion of the graphene oxide is not properly made.

[Example 7]

0.2 g of graphite oxide was added to 40 ml of oleylamine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 4.5 hours, and analyzed using an atomic probe microscope. As a result, it was confirmed that the plate-shaped graphene having a thickness of about 1.5 nm and a width of 5 μm was formed. When the ultrasonic grinding time is more than 5 hours, it was confirmed that the dispersion of graphene oxide is rather reduced.

[Example 8]

0.2 g of graphite oxide was added to 40 ml of oleylamine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 5 hours, and analyzed using an atomic probe microscope. As a result, it was confirmed that the plate-shaped graphene having a thickness of about 1.2 nm and a width of 5 μm was formed. When the ultrasonic grinding time is more than 5 hours, it was confirmed that the dispersion of graphene oxide is rather reduced.

[Example 9]

0.2 g of graphite oxide was added to 40 ml of oleylamine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours. Graphene oxide combined with titanium dioxide was prepared by adding 0.4 ml of titanium chloride and reacting at 300 ° C. for 10 minutes while the prepared solution was heated to 300 ° C. in a round flask, and analyzed using a transmission electron microscope. As a result, it was confirmed that the rod-shaped titanium dioxide having a diameter of about 4 nanometers and a length of 25 nanometers was formed on the graphene sheet, and the density of titanium dioxide on the graphene sheet was about 300 particles / μm ² . .

[Example 10]

0.2 g of graphite oxide was added to 40 ml of oleylamine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours. Graphene oxide combined with titanium dioxide was prepared by adding 0.7 ml of titanium chloride and reacting at 300 ° C. for 10 minutes while the prepared solution was heated to 300 ° C. in a round flask, and analyzed using a transmission electron microscope. As a result, it was confirmed that the rod-shaped titanium dioxide having a diameter of about 4 nanometers and a length of 25 nanometers was formed on the graphene sheet, and the density of titanium dioxide on the graphene sheet was about 700 particles / μm ² . . In addition, when the addition amount of titanium chloride is more than 0.7 ml, it was confirmed that the size of the produced titanium dioxide is greatly increased.

[Example 11]

Using the same method as in Example 1, 0.2 g of graphite oxide was added to 40 ml of oleylamine, and then graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours, and the prepared solution was used in a round flask. Heated to 300 deg. 0.55 ml of titanium chloride was added and reacted at 300 ° C. for 5 minutes to prepare titanium oxide-bonded graphene oxide, and analyzed using a transmission electron microscope. As a result, a diameter of about 4 nanometers and a length of 25 nanometers were obtained. It was confirmed that titanium dioxide in the form of a rod was formed on the graphene sheet. When the reaction time was reduced to within 5 minutes, it was confirmed that the form of the titanium dioxide rod was formed nonuniformly.

[Example 12]

0.2 g of graphite oxide was added to 40 ml of oleylamine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours, and the prepared solution was placed in a round flask. Heated to 300 ° C. 0.55 ml of titanium chloride was added and reacted at 300 ° C. for 30 minutes to produce titanium oxide-bonded graphene oxide. A TEM was analyzed using a transmission electron microscope, and the diameter was about 4 nanometers and 25 nanometers in length. It was confirmed that the rod-shaped titanium dioxide was formed on the graphene sheet.

[Example 13]

0.2 g of graphite oxide was added to 40 ml of oleylamine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours, and the prepared solution was placed in a round flask. Heated to 300 ° C. Titanium dioxide-bonded graphene oxide was prepared by adding 0.55 ml of titanium chloride for 45 minutes at 300 ° C., and analyzed by transmission electron microscopy, and it had a diameter of about 4 nanometers and a length of 25 nanometers. It was confirmed that the rod-shaped titanium dioxide was formed on the graphene sheet, it was confirmed that formed on the graphene sheet.

[Example 14]

0.2 g of graphite oxide was added to 40 ml of oleylamine using the same method as in Example 1, and graphene oxide dispersed in oleylamine was prepared by ultrasonic grinding for 3 hours, and the prepared solution was placed in a round flask. Heated to 300 ° C. After adding 0.55 ml of titanium chloride and reacting at 300 ° C. for 60 minutes, titanium dioxide-bonded graphene oxide was prepared. As a result of analysis using a transmission electron microscope, a diameter of about 5 nanometers and a length of 30 nanometers were obtained. It was confirmed that the rod-shaped titanium dioxide was formed on the graphene sheet, it was confirmed that formed on the graphene sheet. When the reaction time increased to 60 minutes or more, it was confirmed that the size of the formed titanium dioxide nanorods increased significantly.

[Example 15]

Graphene oxide combined with titanium dioxide nanorods prepared in Example 1 was dried in a vacuum oven at 25 ℃ and heat treatment for 15 minutes at 500 ℃ temperature in a carbonization furnace, crystallization of titanium dioxide and reduction of graphene oxide Was performed. As a result of X-ray diffraction analysis, when the heat treatment was performed at 500 ° C. for 15 minutes or less, it was confirmed that the crystallinity of titanium dioxide was weak in the anatase type.

[Example 16]

Using the same method as in Example 15, the graphene oxide combined with the titanium dioxide nanorods prepared in Example 1 was dried in a vacuum oven at 25 ℃ through a heat treatment for 30 minutes at 500 ℃ temperature in a carbonization furnace , Crystallization of titanium dioxide and reduction of graphene oxide were carried out. As a result of X-ray diffraction analysis, it was confirmed that the crystallinity of titanium dioxide was Anatase type.

Example 17

Using the same method as in Example 15, the graphene oxide combined with the titanium dioxide nanorods prepared in Example 1 was dried in a vacuum oven at 25 ℃ after heat treatment for 45 minutes at 500 ℃ temperature in a carbonization furnace , Crystallization of titanium dioxide and reduction of graphene oxide were carried out. X-ray diffraction analysis shows that the crystallinity of titanium dioxide is anatase type. there was.

[Example 18]

Using the same method as in Example 15, the graphene oxide combined with the titanium dioxide nanorods prepared in Example 1 was dried in a vacuum oven at 25 ℃ through a heat treatment for 1 hour at 500 ℃ temperature in a carbonization furnace, Crystallization of titanium dioxide and reduction of graphene oxide were performed. As a result of X-ray diffraction analysis, it was confirmed that the crystallinity of titanium dioxide showed rutile type when heat-treated at 500 ° C. for 1 hour or more. In addition, it was confirmed that the aggregation phenomenon of the graphene sheet.

[Example 19]

Using the same method as in Example 15, the graphene oxide combined with the titanium dioxide nanorods prepared in Example 1 was dried in a vacuum oven at 25 ℃ and then 300, 400, 500, 600, 700, and Through a 30-minute heat treatment at 800 ℃ temperature, crystallization of titanium dioxide and reduction of graphene oxide was performed. As a result of X-ray diffraction analysis, the crystallinity of titanium dioxide coexisted with amorphous and anatase type at 300-400 ℃, and strong anatase type at 500 ℃. In addition, the rutile type appeared strongly at the heat treatment temperature of 600 degreeC or more.

[Example 20]

Titanium dioxide nanorods were prepared for a control experiment. 40 ml of oleylamine was heated to 300 ° C. in a round flask, and 0.55 ml of titanium chloride was added thereto and reacted at 300 ° C. for 10 minutes to prepare titanium dioxide nanorods. It was confirmed that the shape of the nanorod having a length of the meter.

Example 21

When 20 mL of 15 ppm methylene blue solution was decomposed under visible light using a graphene sheet having a uniform titanium dioxide bond prepared in Example 15 at a concentration of 0.5 g / L, after 2 hours 1 ppm concentration of methylene blue solution It was confirmed that it was. (Fig. 2)

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Claims (7)

(A) dispersing graphite oxide in oleyl amine using an ultrasonic generator to prepare a graphene oxide solution dispersed in oleyl amine;
(B) preparing a graphene oxide sheet in which titanium dioxide in the form of nanorods is combined by adding titanium chloride, a titanium dioxide precursor, to the graphene oxide solution dispersed in the oleylamine; And
(C) the titanium dioxide nanorods are combined, comprising: drying the graphene oxide sheet to which the titanium dioxide nanorods are bonded, followed by heat treatment to induce high crystallinity of titanium dioxide and reduction of graphene oxide; Method for producing a graphene sheet. The method of claim 1, wherein the amount of graphite oxide added is Method for producing a graphene sheet with titanium dioxide nanorods is characterized in that 0.05 to 1 parts by weight based on 100 parts by weight of oleylamine. According to claim 1, wherein the dispersion time using the ultrasonic generator is a method for producing a graphene sheet with titanium dioxide nanorods, characterized in that 2 to 5 hours. The graphene sheet of claim 1, wherein the addition amount of titanium chloride is 1 to 1.75 parts by volume with respect to 100 parts by weight of the oleylamine solution in the oleylamine solution in which the graphene oxide is dispersed. Manufacturing method. The method of claim 1, wherein the sol-gel reaction of titanium dioxide in the oleylamine solution is heated at 300 ° C. for 10 to 60 minutes. The method of claim 1, wherein the heat treatment temperature is 300 to 800 ℃, the method of producing a graphene sheet with titanium dioxide nanorods combined. The method of claim 1, wherein the heat treatment time is 30 to 60 minutes.

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