KR20240057823A - Manufacturing method of reduced graphene oxide having aqueous dispersable, redispersable and hybridable with heteromaterial - Google Patents

Abstract

The present invention relates to a method for producing reduced graphene, which has water dispersibility and redispersibility and can be composited with heterogeneous materials. More specifically, it relates to a method for producing graphene oxide by exfoliating graphite oxide; Reducing the exfoliated graphite oxide to produce reduced graphene; Dispersing the reduced graphene in a solvent; And a step of modifying the reduced graphene by adding a metal complex having a different functional group to the dispersed reduced graphene dispersion and performing a reforming reaction with the defective portion within the layer or at the edge of the reduced graphene. A method of producing modified reduced graphene is provided, which improves the water dispersibility and redispersibility of reduced graphene and allows it to be complexed by chemically bonding with dissimilar materials.

Description

Manufacturing method of reduced graphene oxide having aqueous dispersable, redispersable and hybridable with heteromaterial}

The present invention manufactures reduced graphene (rGO) and then introduces a metal complex with a different functional group into the layer or edge of the reduced graphene to produce two-dimensional graphene. Even if reduced graphene with a structure aggregates and precipitates due to secondary attraction, it is easily redispersed when shear force is applied and chemical reactions with heterogeneous materials are also possible, making it easy to composite.

Graphene is a two-dimensional carbon material with a honeycomb structure of carbon single atomic layers and a thickness of about 0.3 nm (1 layer) to 1.5 nm (5 layers). It is a material with excellent physical and chemical properties, but its physical properties change significantly depending on the degree of reduction. As the degree of reduction increases, the two-dimensional structure becomes more dense, and the interlayer Van der Waals attraction increases, causing re-agglomeration to become graphite again.

When reduced graphene is re-graphitized, it is crushed without being re-exfoliated or re-dispersed even when a strong shear force is applied, and only the average particle size becomes small, so there is a problem in that the excellent physical and chemical properties of graphene cannot be utilized.

Therefore, the excellent physics of reduced graphene. In order to utilize its chemical properties, it must not only be dispersible in the liquid phase, but also maintain its dispersibility even when redispersed in the liquid phase after solidification. In order to utilize reduced graphene in various materials and applications, it is also necessary to composite it with heterogeneous materials. am.

To achieve this purpose, Republic of Korea Patent No. 10-1590683 uses a compound having an amine group at one end and a carboxylate or sulfonate at the other end. A technology is disclosed in which the epoxy group present due to defects in reduced graphene is reacted to form a chemical bond, and the anion of carboxylate or sulfonate present at the other end is modified to have water dispersibility. In this case, the moisture of reduced graphene is disclosed. Although it has excellent acidity, the other anion can only react with organic substances, making complexation with heterogeneous materials impossible.

In addition, in Republic of Korea Patent No. 10-1605245, N-oxide compounds such as N-methylmorpholine-N-oxide are added to reduced graphene to improve water dispersibility. An improved technology is being developed, but it is also impossible to combine it with dissimilar materials.

The present invention was developed to solve the problems of the prior art as described above, and the present invention is to add a metal complex having two or more functional groups at the completion stage of reducing graphene to form a metal complex within the layer or edge of reduced graphene ( The purpose is to provide a method for producing modified reduced graphene that has water dispersibility or redispersibility due to hydrophilic functional groups by covalently bonding to the defective portion of the reduced graphene molecule to introduce multiple or heterogeneous functional groups in the reduced graphene molecule. Do it as

Another purpose of the present invention is to provide a method for producing reduced graphene that can be chemically combined with dissimilar materials to form a composite.

In order to achieve the above-mentioned object, the present invention includes the steps of manufacturing graphene oxide by exfoliating graphite oxide; Reducing the exfoliated graphite oxide to produce reduced graphene; Dispersing the reduced graphene in a solvent; And a step of modifying the reduced graphene by adding a metal complex having a different functional group to the dispersed reduced graphene dispersion and performing a reforming reaction with the defective portion within the layer or at the edge of the reduced graphene. A method for producing modified reduced graphene is provided, which improves the water dispersibility and redispersibility of reduced graphene and allows it to be complexed by chemically bonding with dissimilar materials.

The metal complex having the heterogeneous functional group preferably has the structure of the following formulas 1 to 2.

Formula 1

(R ¹ O) _n -M-(XR ² -Y) _4-n

here,

R ¹ : C ₁ ~ C ₄ alkyl, C ₂ ~ C ₄ alkenyl or C ₃ ~ C ₄ isoalkyl

R ² : C ₁ ~ C ₁₈ alkyl, C ₃ ~ C ₁₈ isoalkyl, C ₂ ~ C ₁₈ alkenyl or C ₄ ~ C ₁₈ isoalkenyl

M: titanium or zirconium

X: carboxylate, sulfonate, phosphate or pyrophosphate

Y: amine, hydroxyl, epoxy, or acid

Formula 2

(R ¹ O) _n -M-(OR ² -Y) _4-n

here,

R ¹ : C ₁ ~ C ₄ alkyl, C ₂ ~ C ₄ alkenyl or C ₃ ~ C ₄ isoalkyl

R ² : C ₁ ~ C ₁₈ alkyl, C ₃ ~ C ₁₈ isoalkyl, C ₂ ~ C ₁₈ alkenyl or C ₄ ~ C ₁₈ isoalkenyl

M: titanium or zirconium

Y: amine, hydroxyl, epoxy or acid

It is preferable to perform a reforming reaction when the reduction degree of the reduced graphene has a C _1s / O _1s ratio of 10 to 100 as determined by X-ray photoelectron spectroscopy.

It is preferable that the amount of the metal complex having the different functional groups added is 0.1% to 50% by weight relative to the reduced graphene.

It is preferable to carry out the reforming reaction at a hydrogen ion concentration in the range of 6 to 10.

It is preferable to carry out the reforming reaction at a reaction temperature of 30°C or more and 100°C or less.

According to the present invention as described above, after producing reduced graphene, a metal complex is added and covalently bonded to the defective portion within the layer or at the edge of the reduced graphene, thereby inserting a plurality of or different functional groups within the reduced graphene molecule, resulting in reduction. Reduced graphene modified by hydrophilic groups introduced into graphene has water dispersibility or redispersibility and can be chemically combined with dissimilar materials to form a complex.

Figure 1 is a schematic diagram of the reaction between (a) the defective epoxy and (b) the proton of Formula 1 and the alkoxy group of Formula 1 in the reduced graphene layer.
Figure 2 is a schematic diagram of the reaction between (a) the defective epoxy and the amine group of Chemical Formula 2 (b) the proton and the alkoxy group of Chemical Formula 2 in the reduced graphene layer.
Figure 3 is a representative X-ray photoelectron spectroscopy result confirming the degree of reduction of reduced graphene after reduction.
Figure 4 shows the results of measuring the absorbance of the dispersion using an ultraviolet-visible spectrometer to confirm the water dispersibility and redispersibility of reduced graphene. Figure 4a shows the water dispersibility and re-dispersibility of reduced graphene oxidized/reduced by a common chemical method, and Figure 4b shows the water dispersibility and re-dispersibility of modified reduced graphene reacted with the metal complex of Chemical Formula 1 after producing reduced graphene. It is dispersible, and Figure 4c shows the water dispersibility and redispersibility of modified reduced graphene reacted with the metal complex of Chemical Formula 2 after producing reduced graphene.
Figure 5 is an atomic force microscope (AFM) photograph measuring the thickness of reduced graphene and redispersed reduced graphene. Figure 5a shows reduced graphene and redispersed reduced graphene, Figure 5b shows modified reduced graphene reacted with the metal complex of Chemical Formula 1 and modified reduced graphene redispersed, and Figure 5c shows the metal complex of Chemical Formula 2. It is modified reduced graphene reacted with and modified reduced graphene re-dispersed.

Hereinafter, the present invention will be described in more detail based on the attached drawings and preferred embodiments.

In the present invention, graphite oxide (GPO, graphite oxide) is manufactured by the Brodie or Hummers method, and shear force is applied to the graphite oxide to exfoliate to produce graphene oxide (GO). In addition, a reducing agent such as hydroiodic acid (HI) was added to the graphene oxide to produce reduced graphene. Reduced graphene can be produced in this way, but reduced graphene produced by exfoliating and reducing graphite oxide is also possible, and the method of producing reduced graphene is not particularly limited.

A metal complex such as the following Chemical Formula 1 or Chemical Formula 2 is added to the water-dispersed reduced graphene prepared above and covalently bonded to the defective portion within the layer or at the edge of the reduced graphene to form multiple or different functional groups within the reduced graphene molecule. By providing a method for producing modified reduced graphene that has water dispersibility or redispersibility due to the hydrophilic group introduced in the modified reduced graphene and can be complexed by chemical bonding with dissimilar materials.

Formula 1

(R ¹ O) _n -M-(XR ² -Y) _4-n

here,

R ¹ : C ₁ ~ C ₄ alkyl, C ₂ ~ C ₄ alkenyl or C ₃ ~ C ₄ isoalkyl

R ² : C ₁ ~ C ₁₈ alkyl, C ₃ ~ C ₁₈ isoalkyl, C ₂ ~ C ₁₈ alkenyl or C ₄ ~ C ₁₈ isoalkenyl

M: titanium or zirconium

X: carboxylate, sulfonate, phosphate or pyrophosphate

Y: amine, hydroxyl, epoxy, or acid

Formula 2

(R ¹ O) _n -M-(OR ² -Y) _4-n

here,

R ¹ : C ₁ ~ C ₄ alkyl, C ₂ ~ C ₄ alkenyl or C ₃ ~ C ₄ isoalkyl

R ² : C ₁ ~ C ₁₈ alkyl, C ₃ ~ C ₁₈ isoalkyl, C ₂ ~ C ₁₈ alkenyl or C ₄ ~ C ₁₈ isoalkenyl

M: titanium or zirconium

Y: amine, hydroxyl, epoxy or acid

Conventional reduced graphene manufacturing methods include existing physical or chemical reduced graphene manufacturing methods, and if reduced graphene is manufactured with a C _1s / O _1s ratio of 10 to 100 according to X-ray photoelectron spectroscopy, the manufacturing method It can be applied to the present invention regardless. In the present invention, when the ratio of C _1s / O _1s in X-ray photoelectron spectroscopy is less than 10, the number of defects in the layer or at the edge of the reduced graphene increases, and this causes a plurality of Y functional groups of Formula 1 or Formula 2 to be reduced. It is not limited to the intramolecular reaction of graphene, but the chemical bonds between molecules increase and cohesion increases, so the purpose of water dispersibility or redispersibility cannot be achieved. If the ratio of C _1s /O _1s is more than 100, the Because the degree of reduction is high, defects within the layer or at the edge of the reduced graphene are minimal, so the alkoxy reaction with the proton present in the layer of the reduced graphene is the main reaction rather than the reaction with the Y functional group of Chemical Formula 1 or Chemical Formula 2. Since the functional group to be complexed is consumed, complexation cannot be expected, so the ratio of C _1s /O _1s in X-ray photoelectron spectroscopy has critical significance in the above range.

The amount of the metal complex added is preferably proportional to the specific surface area (BET surface area) of reduced graphene. In the case of the present invention, the specific surface area is 100 m ² /g or less and C _1s /O according to X-ray photoelectron spectroscopy. Since it is applied to reduced graphene with a relatively high degree of reduction where the ratio of _1s is 10 to 100, defects within the layer or at the edges of the reduced graphene are small, so the amount is preferably within 0.1% by weight to 50% by weight compared to the reduced graphene. If the amount of the metal complex added is 0.1% by weight or less, the repulsive force due to the hydrophilic groups within the layer or at the edge of the modified reduced graphene is weaker than the Vander Waals force that occurs between reduced graphene, resulting in interlayer cohesion, causing precipitation and At the same time, there is a problem of reduced redispersibility. In addition, if the amount of the metal composite added is more than 50% by weight, the excess metal composite remaining after reacting with the defective portion within the layer or at the edge of the reduced graphene reacts between the layers of the reduced graphene, causing agglomeration, resulting in water dispersion and redispersion. Since problems arise in terms of stability, the amount of metal complex added is of critical significance within the above range.

It is preferable that the hydrogen ion concentration (pH) of the reforming reaction in which the metal complex is added and covalently bonded to the defective portion within the layer or at the edge of the reduced graphene is carried out in the range of 6 to 10. When the above-described reforming reaction is performed in a weakly to strongly acidic condition with a hydrogen ion concentration of less than 6, a plurality of alkoxy groups are hydrolyzed to form metal hydroxide, so the metal hydroxide can be complexed by chemical bonding with dissimilar materials. Not only is the target for complexation limited due to mutual dehydration, but also the carboxylate indicated by Not only is there no functional group to complex, but it has the disadvantage of not being able to be complexed. In addition, when the hydrogen ion concentration of the reforming reaction is more than 10, the functional group of the metal complex has a strong tendency to polymerize through self-condensation reaction rather than reacting with defects in the layer or edge of the reduced graphene, resulting in water dispersibility in the reduced graphene. Alternatively, it has the disadvantage of not only being unable to provide redispersibility but also failing to achieve the original purpose of complexation, so the hydrogen ion concentration in the reforming reaction is of critical significance in the above range.

In addition, the reaction temperature for adding the metal complex and covalently bonding it to the defective portion within the layer or at the edge of the reduced graphene is preferably carried out at 30°C to 100°C. When the reforming reaction temperature is 30°C or lower, side reactions occur as the reaction rate between the functional group represented by Y in Chemical Formulas 1 and 2 of the metal complex and epoxy, which forms most of the defects in the layer or edge of the reduced graphene, slows down. There is a disadvantage in that the alkoxy and the portion indicated by When the reforming reaction temperature is 100°C or higher, not only the reaction between the functional group represented by Y in Formula 1 and Formula 2 in the metal complex and epoxy, which forms most of the defects in the layer or edge of the reduced graphene, but also the alkoxy in the metal complex As the reaction with the proton present in the layer of reduced graphene occurs competitively, the concentration of the metal complex increases in the layer of the modified reduced graphene, and the functional group for complexing with the heterogeneous material is consumed, so complexation cannot be expected, so the modification reaction temperature has critical significance in the above range.

Hereinafter, the present invention will be described in detail based on the accompanying drawings and examples. The present invention can be implemented in many different forms and is not limited to the embodiments described herein.

Manufacturing of reduced graphene

10 g of graphite with an average particle diameter of 8 ㎛ and 200 ml of fuming nitric acid were added to a jacket-type 0.5 liter reaction tank equipped with a stirrer and thermometer, maintained at 25°C, and 60 g of sodium chlorate as an oxidizing agent was added three times while stirring under a nitrogen stream. It was divided and added at 15-minute intervals and then oxidized for 2 hours. The oxidized graphite was filtered to remove concentrated nitric acid, and to inhibit further oxidation, it was washed by adding 20 ml of hydrogen peroxide to 200 ml of distilled water, and then washed with distilled water until the hydrogen ion concentration of the filtrate reached 6. The graphite oxide prepared as above was dried at -40°C for 24 hours using a freeze dryer.

500 ml of distilled water and 1 g of graphite oxide prepared as above were added to a 1-liter jacketed reaction tank equipped with a stirrer and thermometer, and then exfoliated at 6,000 rpm for 2 hours using a homogenizer to produce graphene oxide. Then, 10 ml of hydroiodic acid was added thereto and reduced for 7 hours while stirring at 70°C to prepare reduced graphene. The reduced graphene prepared by the above method was washed with distilled water, separated by a centrifuge, and purified until the hydrogen ion concentration of the filtrate reached 6 to prepare reduced graphene to be modified.

[Example 1] Reduced graphene modified with Chemical Formula 1

Lithium hydroxide was added to 500 ml of the reduced graphene dispersion prepared by the above reduced graphene production method until the hydrogen ion concentration reached 9, and the reaction temperature was raised to 70°C while stirring. Add 100 mg of Titanium IV (4-amino)benzene sulfonate-O, bis(dodecyl)benzene sulfonate-O, and 2-propanolato, react for 2 hours, and cool to room temperature to obtain a modified product that can be dispersed in water and redispersed. Reduced graphene was prepared. The reaction with reduced graphene according to Chemical Formula 1 is as shown in Figure 1.

[Example 2] Reduced graphene modified with Chemical Formula 2

Lithium hydroxide was added to 500 ml of the reduced graphene dispersion prepared by the above reduced graphene production method until the hydrogen ion concentration reached 9, and the reaction temperature was raised to 70°C while stirring. 100 mg of Titanium IV 2-propanolato and tris(3,6-diaza)hexanolato were added here, reacted for 2 hours, and then cooled to room temperature to prepare modified reduced graphene capable of water dispersion and re-dispersion. The reaction with reduced graphene according to Formula 2 is as shown in FIG. 2.

[Comparative example] Reduced graphene without modification

The reduced graphene dispersion prepared by the above reduced graphene production method was used as is.

[Evaluation example]

Water dispersibility measurement method

After leaving the 0.1% by weight solution of reduced graphene at room temperature for 1 hour, the absorbance was scanned from 400 nm to 700 nm using an ultraviolet-visible spectrometer, and the absorbance at 600 nm was measured and compared.

Redispersibility measurement method

The water dispersibility measurement solution was centrifuged at 10,000 G-force for 10 minutes, then redispersed for 10 minutes with ultrasound at a frequency of 40 kHz and an output of 400 W. The absorbance was measured and compared using the same method as the water dispersibility measurement method, and the redispersibility was calculated using the formula below. Calculated.

Redispersibility (%) = (A ₁ /A ₀ ) x 100

here,

A ₀ : Absorbance of sample before centrifugation

A ₁ : Absorbance of sample re-dispersed after centrifugation

The closer the result is to 100, the better the redispersibility.

Water dispersibility and redispersibility evaluation results division Example 1 Example 2 Comparative example A ₀ 1.615 1.604 1.526 A ₁ 1.535 1.535 0.191 Redispersibility (%) 95.05 95.70 12.52 note Figure 4b Figure 4c Figure 4a

As shown in Table 1 and Figures 4a to 4c, regardless of the type of metal composite, when modified with a metal composite, water dispersibility and redispersibility are improved to more than 95%, compared to 12.52% when not treated. You can.

In addition _, as shown _in the It can be seen that it is not caused by a compound but is a characteristic of modified reduced graphene.

In addition, as shown in the atomic force microscope results of Figure 5, reduced graphene is not redispersed to its original thickness when redispersed after precipitation (Figure 5a, Rq value 1.025 nm → 20.405 nm), whereas reduced graphene modified with Formula 1 and Formula 2 It can be seen from the results of ultraviolet-visible spectroscopy that reduced graphene has a thickness similar to that before precipitation even after redispersion (Figure 5b, Rq value 1.142 nm → 1.383 nm, Figure 5c, Rq value 1.066 nm → 1.454 nm). It can be seen that redispersibility is significantly improved.

Tables 2 and 3 below show statistical values according to the histogram of Figure 5a, (a) initial and (b) after redistribution, respectively, and Tables 4 and 5 show statistical values according to the histogram of Figure 5b, (a) Initial and (b) after redistribution, respectively, and Tables 6 and 7 are statistical values according to the histogram of Figure 5c, showing (a) initial and (b) after redistribution, respectively.

Although the present invention has been described in more detail by way of examples above, the present invention is not necessarily limited to these examples and may be modified and implemented in various ways without departing from the technical spirit of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but are for explanation, and the scope of the technical idea of the present invention is not limited by these examples. The scope of protection of the present invention shall be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope shall be construed as being included in the scope of rights of the present invention.

Claims (6)

Exfoliating graphite oxide to produce graphene oxide;
Reducing the exfoliated graphite oxide to produce reduced graphene;
Dispersing the reduced graphene in a solvent; and
It includes the step of modifying the reduced graphene by adding a metal complex having a different functional group to the dispersed reduced graphene dispersion and causing a reforming reaction with the defective portion within the layer or at the edge of the reduced graphene,
A method of producing modified reduced graphene, characterized in that it improves the water dispersibility and redispersibility of reduced graphene through the above steps and can be complexed by chemically bonding with dissimilar materials. According to paragraph 1,
A method of producing modified reduced graphene, characterized in that the metal complex having the heterogeneous functional group has the structure of the following Chemical Formula 1 to Chemical Formula 2.
Formula 1
(R ¹ O) _n -M-(XR ² -Y) _4-n
here,
R ¹ : C ₁ ~ C ₄ alkyl, C ₂ ~ C ₄ alkenyl or C ₃ ~ C ₄ isoalkyl
R ² : C ₁ ~ C ₁₈ alkyl, C ₃ ~ C ₁₈ isoalkyl, C ₂ ~ C ₁₈ alkenyl or C ₄ ~ C ₁₈ isoalkenyl
M: titanium or zirconium
X: carboxylate, sulfonate, phosphate or pyrophosphate
Y: amine, hydroxyl, epoxy, or acid
Formula 2
(R ¹ O) _n -M-(OR ² -Y) _4-n
here,
R ¹ : C ₁ ~ C ₄ alkyl, C ₂ ~ C ₄ alkenyl or C ₃ ~ C ₄ isoalkyl
R ² : C ₁ ~ C ₁₈ alkyl, C ₃ ~ C ₁₈ isoalkyl, C ₂ ~ C ₁₈ alkenyl or C ₄ ~ C ₁₈ isoalkenyl
M: titanium or zirconium
Y: amine, hydroxyl, epoxy or acid According to paragraph 1,
A method of producing modified reduced graphene, characterized in that a modification reaction is performed when the degree of reduction of the reduced graphene is at a ratio of 10 to 100 of C _1s /O _1s as determined by X-ray photoelectron spectroscopy. According to paragraph 1,
A method for producing modified reduced graphene, characterized in that the amount of the metal complex having the heterogeneous functional group added is 0.1% to 50% by weight relative to the reduced graphene. According to paragraph 1,
A method of producing modified reduced graphene, characterized in that the reforming reaction is performed at a hydrogen ion concentration in the range of 6 to 10. According to paragraph 1,
A method of producing modified reduced graphene, characterized in that the reforming reaction is performed at a reaction temperature of 30°C or more and 100°C or less.