KR101100745B1 - Method for synthesizing transition metal oxide and carbon nanotube composites by using microwave-polyol process - Google Patents

Abstract

The present invention relates to a method for producing a transition metal oxide and carbon nanotube composites using a microwave-polyol synthesis method, and more particularly, the acid-treated carbon nanotube powder is dispersed in a polyol solvent through ultrasonication, and the transition metal By adding salts and protective agents to synthesize the transition metal oxide / carbon nanotube complex under microwave, microwave-polyols reduce the synthesis time and allow the transition metal oxide to be coated on a carbon nanotube surface in a very uniform and small size. It relates to a method for producing a transition metal oxide and carbon nanotube composite using a synthesis method.

Microwave-polyol synthesis method, nano-sized transition metal oxide, ruthenium oxide, carbon nanotube, transition metal oxide / carbon nanotube composite, transition metal oxide / carbon nanotube hybrid material, forced hydration

Description

Method for synthesizing transition metal oxide and carbon nanotube composites by using microwave-polyol process

The present invention relates to a method for producing a transition metal oxide and carbon nanotube composites using a microwave-polyol synthesis method, and more particularly, the acid-treated carbon nanotube powder is dispersed in a polyol solvent through ultrasonication, and the transition metal By adding salts and protective agents to synthesize the transition metal oxide / carbon nanotube complex under microwave, microwave-polyols reduce the synthesis time and allow the transition metal oxide to be coated on a carbon nanotube surface in a very uniform and small size. It relates to a method for producing a transition metal oxide and carbon nanotube composite using a synthesis method.

Carbon nanotubes have a quasi one-dimensional quantum structure, and various quantum phenomena are observed at low levels. Especially, the carbon nanotubes have excellent mechanical robustness, chemical stability, and thermal conductivity. Indicates.

In addition, when the transition metal is attached to the carbon nanotubes, it can be used as a hybrid material capable of improving the excellent material properties or expression of new properties of the carbon nanotubes. The transition metal oxide / carbon nanotube composite is applicable to electrochemical energy storage materials, catalysts and electrode materials for conversion devices, gas sensors, FEDs and electronic devices, and the like. Nanonization and size distribution control are essential.

Conventional methods of preparing transition metal oxide / carbon nanotube composites include electrochemical plating of transition metals on carbon nanotubes ( J. Am . Chem . Soc ., 127, 6146, 2005) or using metal vapor ( Appl . Phys . Lett ., 77,3015,2005), and the method of preparing a transition metal oxide / carbon nanotube composite through heat treatment was mostly performed. However, the method of synthesizing transition metal oxide / carbon nanotubes through heat treatment shows a time and economic limitation due to the complexity of the manufacturing process from the practical application point of view.

On the other hand, the polyol process (polyol process) is a process using a polyol solvent containing at least two hydroxyl groups (OH), the polyol type of EG (Ethylene Glycol), DEG (Diethylene Glycol), TEG (Triethylene Glycol), TTEG (Tetraethylene Glycol), TetEg (Tetratethylene Glycol), and the like. The polyol process allows for the synthesis of uniform nanoscale metals or metal oxides, and because the reaction proceeds in solution, the reaction occurs at lower temperatures as compared to the solid state method or heat treatment in a reducing hydrogen gas atmosphere. It is an efficient method for the synthesis of metal oxides (Korean Patent Nos. 2007-0053667, 2007-0048675).

The synthesis mechanism and synthesis result according to the role of the polyols in the polyol process is different from (Journal of Solid State Chemistry 154, 405-411 (2000), Angew. Chem. 2005, 117, 4465-4469)

First, when the role of the polyol in the polyol process is a reducing agent, the synthesis mechanism is as follows.

<Mechanism Ⅰ>

CH ₂ OH-CH ₂ OH (polyol) → CH ₃ CHO (reductant) + H ₂ O ‥‥ (1)

2CH ₃ CHO + 2M ⁺ → 2M + 2H ⁺ + CH ₃ COCOCH ₃ ‥‥(2)

The polyol (CH ₂ OH-CH ₂ OH) is dehydrated at high temperature like reaction (1) to separate acetaldehyde (acetealdehyde: CH ₃ CHO) and water (reaction (1)). At this time, the acetaldehyde produced acts as a reducing agent of metal ions as in reaction (2) to form metal particles after the polyol reaction.

Second, when polyol is used as a capping agent, it is possible to synthesize metal oxide nanoparticles. Fe ₂ O ₃ , TiO ₂ , ZnO, V ₂ O ₅ , Mn ₃ O ₄ and the like. The synthesis mechanism of the metal oxide by the polyol process is as follows.

<Mechanism II>

When polyol reaction, a certain amount of H ₂ O is added to hydrate the metal ions, and the hydrated metal ions react with the polyol to synthesize a hydroxide compound of the intermediate metal and heat the hydroxide compound. Converted to metal oxides. As above solution H ₂ O was added an amount of the preparation is to enable the synthesis of a metal oxide without an additional heat treatment causes a forced hydration when the polyol process conducted (Materials Research Bulletin , Vol. 40, 2153, 2005; Inorg . Chem . 41, 6137, 2002).

To date, there are no known examples of preparing metal oxide / carbon nanotube composites without heat treatment using the second mechanism of the polyol process.

An object of the present invention is a transition metal oxide and carbon nanotubes capable of synthesizing a transition metal oxide in a short time without performing a heat treatment process, which is a post-treatment process of a reaction product using a microwave-polyol process. It is to provide a method for producing a composite.

In order to achieve the above object, the present invention

Acid treating the carbon nanotube powder;

Dispersing the acid treated carbon nanotube powder in a polyol solvent;

Mixing the dispersed solution, the transition metal salt and the protecting agent in the step;

Mixing water with the mixed solution of the step; And

It provides a method for producing a transition metal oxide and carbon nanotube composite comprising the step of preparing a transition metal oxide and carbon nanotube composite from the mixed solution.

The present invention also provides a transition metal oxide and carbon nanotube composite prepared according to the method for producing a transition metal oxide and carbon nanotube composite of the present invention.

The present invention also provides an article comprising the transition metal oxide and carbon nanotube composite of the present invention.

The present invention has the effect of simplifying the provision process and shortening the manufacturing time by selectively coating the transition metal oxide on the surface of the carbon nanotubes without a heat treatment process through forced hydration.

In addition, the transition metal oxide and carbon nanotube composites prepared according to the method of the present invention are very small and uniform in size, so that the surface area of the transition metal oxide and fuel cell (supercapacitor) is maximized. ), Filtration membranes, chemical detectors, gas sensors and the like.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated concretely.

The present invention

Acid treating the carbon nanotube powder;

Dispersing the acid treated carbon nanotube powder in a polyol solvent;

Mixing the dispersed solution, the transition metal salt and the protecting agent in the step;

Mixing water with the mixed solution of the step; And

It relates to a method for producing a transition metal oxide and carbon nanotube composite comprising the step of preparing a transition metal oxide and carbon nanotube composite from the mixed solution.

Hereinafter, a method of preparing the transition metal oxide and carbon nanotube composite of the present invention will be described in detail with reference to the accompanying drawings.

Acid treatment of the carbon nanotube powder (100) by dissolving the carbon catalyst in the manufacturing of carbon nanotube powder by dissolving the carbon nanotube powder in a strong acid solution as a strong acid, as well as not dispersed in a solvent such as water It is a step for causing carbon nanotube powder to be easily dispersed in a solvent by imparting hydrophilicity to the carbon nanotubes by causing a functional group on the surface of the carbon nanotube powder exhibiting hydrophobic properties.

The acid treatment of the carbon nanotube powder preferably includes the following steps:

i) adding carbon nanotube powder to an aqueous strong acid solution and acid-treated at 60 to 90 ° C. for 2 to 6 hours;

ii) filtering and washing the aqueous solution; And

iii) removing the water of the cleaned carbon nanotubes to prepare a powder.

Specifically, the carbon nanotube powder is added to an aqueous solution of a strong acid, followed by acid treatment with heat, the acid-treated aqueous solution is filtered through a filter, and the filtered carbon nanotubes are washed one to several times with distilled water. Next, heat is applied to the cleaned carbon nanotubes to evaporate moisture to make the powder again.

The term "carbon nanotube powder" of the present invention includes both single-walled carbon nanotubes and multi-walled carbon nanotubes. In general, carbon nanotube powders exhibit hydrophobic properties and thus are not dispersed in an aqueous solution such as water. Therefore, the hydrophilicity is given through the acid treatment so that it can be easily dispersed in the polyol solvent of the next step.

As the strong acid used in the acid treatment for imparting hydrophilicity to the carbon nanotubes, sulfuric acid, nitric acid, hydrochloric acid, or a mixture thereof may be used alone or in combination of two or more thereof.

The next step is to disperse the acid treated carbon nanotube powder in a polyol solvent (200).

That is, a polyol solvent is added to the acid-treated carbon nanotubes in a powder state, and ultrasonic waves are sprayed to uniformly disperse the carbon nanotubes in the polyol solution.

The acid treated carbon nanotube powder is preferably included in an amount of 0.001 to 0.1 parts by weight based on 100 parts by weight of the polyol solvent so that the transition metal oxide may be evenly coated on the carbon nanotubes with a thickness of 1 layer. More preferably 0.022 part by weight is good. When the content is less than 0.001 parts by weight, it is difficult to expect the electrical conductivity improvement by adding carbon nanotubes in the carbon nanotubes and the transition metal oxide composite after the reaction, and when the content exceeds 0.1 parts by weight, the dispersion of the carbon nanotube powder Because it is difficult.

In addition, the polyol solvent refers to a substance having two or more OH groups in a molecule, and may include ethylene glycol (EG), diethylene glycol (DEG), polyethylene glycol (TT), tetraethylene glycol (TTEG), or tetraethylethylene (TtEg). These may be used alone or in combination of two or more.

The next step is to mix the solution, transition metal salt and the protective agent dispersed in the dispersion step (300). That is, the solution in which the carbon nanotubes are uniformly dispersed is subjected to ultrasonic treatment and mixed with a transition metal salt and a protecting agent.

As the transition metal salt provided to prepare the metal oxide, salts such as ruthenium, nickel, vanadium, cobalt, manganese, or titanium may be used alone or in combination of two or more.

The transition metal salt is preferably included in an amount of 0.01 to 0.5 parts by weight based on 1 part by weight of carbon nanotubes because the amount of deposition of the metal oxide deposited on the surface of the carbon nanotubes can be controlled according to the content. When the content is less than 0.01 parts by weight, the metal oxide is homogeneous (homogeneous) transition metal oxide particles are synthesized as well as on the carbon nanotubes, if more than 0.5 parts by weight, it is difficult to disperse the carbon nanotubes in the synthesis step.

In addition, a protective agent is added to effectively prevent agglomeration of metal oxide particles when synthesizing the metal oxide on the carbon nanotubes, and inhibits the growth of the metal oxide particles to synthesize metal oxide particles having a small particle size and a uniform particle size distribution. This is possible.

As the protective agent, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylic acid (PAA), or sodium acetate (NaAc) may be used alone or in combination of two or more.

The concentration of the protective agent is preferably 0.01M to 5M. If the concentration is less than 0.01M, the amount of the protective agent is too small to limit the growth of the particles, if it exceeds 5M, the addition of the protective agent does not show the effect, it is difficult to dissolve and remove the protective agent. .

The next step is the step 400 of mixing water with the mixed solution of the dispersion solution, the transition metal salt and the protective agent.

The water is preferably added after complete dissolution of the transition metal salt.

The addition of water to the mixed solution of the dispersion solution, the transition metal salt and the protective agent is intended to synthesize the metal oxide without the additional heat treatment process by using the forced hydration when the metal oxide is synthesized through the microwave-polyol process.

Water is preferably included in 5 to 90 parts by weight based on 100 parts by weight of the mixed solution. If the content is less than 5 parts by weight, after synthesis, the transition metal is synthesized in the form of a metal, not an oxide, and if it exceeds 90 parts by weight, the synthesis efficiency of the synthesized transition metal oxide is reduced.

The next step is to prepare a transition metal oxide and carbon nanotube composite from the mixed solution of the step (500).

The transition metal oxide and carbon nanotube composite is preferably synthesized by reacting the mixed solution at 2.45 to 60 GHz under microwave for 10 to 60 minutes.

The microwave heating method is a heating method using a microwave, has a faster temperature increase rate than the heating method using a reflux device, has the advantage that the entire solution is uniformly heated, there is an advantage that the reaction time can be shortened.

In particular, the reason for the microwave heating method for the synthesis of the transition metal oxide nanoparticles on the carbon nanotubes in the present invention is that in the case of a material having excellent electrical conductivity such as carbon nanotubes, free electrons present in the carbon nanotubes are micro The absorption of waves is accelerated, which is called the conduction loss action of microwaves. The accelerated electrons accelerate the vibration of the carbon lattice, so that the carbon nanotubes are heated to a relatively high temperature in the solution under microwave heating compared to the surrounding solution. Therefore, since the nucleation of the transition metal oxide is promoted only on the surface of the carbon nanotube in the microwave heating atmosphere, heterogeneous nucleation growth occurs, so that the coating of the transition metal oxide is possible only on the surface of the carbon nanotube.

In addition, after the reaction of the transition metal oxide and carbon nanotube composite is washed in a washing solvent it may be further carried out a step of drying at a temperature condition of room temperature to 70 ℃ (600). This is to remove the remaining polyol solvent or additionally formed organic compounds from the mixed solution of the above step.

It is preferable to repeatedly perform one to several times until all of the remaining polyol solvent or organic compound is removed using the washing solvent.

As the washing solvent, ethanol, acetone, or water may be used alone or in combination of two or more.

In addition, the washed transition metal oxide / carbon nanotube composite is preferably dried at a temperature condition of room temperature to 70 ℃, the drying method is not particularly limited, can be used a common general drying method.

To date, numerous studies on the synthesis of many metal oxides through forced hydration have been made, but there are no studies on ruthenium oxide synthesis. Among the transition metal oxides, ruthenium oxide has advantages such as high conductivity, high thermal stability and high chemical corrosion resistance, but has a disadvantage of high price. In order to overcome these disadvantages, the maximum effect should be made in a small amount, which is a method of increasing the surface area by reducing the size of the synthesized particles.

According to one embodiment of the present invention, ruthenium oxide can be effectively produced through the method for producing the transition metal oxide and carbon nanotube composite of the present invention.

The present invention also relates to a transition metal oxide and carbon nanotube composite prepared according to the method for producing a transition metal oxide and carbon nanotube composite of the present invention.

The transition metal oxide and carbon nanotube composite of the present invention is characterized in that the transition metal oxide is evenly coated on the surface of the carbon nanotube, the particle size of the transition metal oxide is 1 to 2nm.

The transition metal oxide is preferably ultrafine ruthenium oxide.

The present invention also relates to an article comprising the transition metal oxide and carbon nanotube composite of the present invention.

The transition metal oxide and carbon nanotube composite of the present invention has a structure in which the particle size of the transition metal oxide is very small and uniform, so that the surface area is maximized, and an energy storage material, for example, a secondary battery, a fuel cell, or a supercapacitor, a filtration membrane It can be applied to chemical detectors or gas sensors.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only for illustrating the present invention in detail and are not intended to limit the scope of the present invention by these examples.

Example 1 Preparation of Ruthenium Oxide / Carbon Nanotube Composites

Carbon nanotube powder was added to sulfuric acid and acid treated at 80 ° C. for 4 hours. The aqueous solution was filtered through a filter, and the filtered carbon nanotubes were washed several times with distilled water, and heat was added to the washed carbon nanotubes to evaporate water to make powder.

0.022 parts by weight of acid-treated carbon nanotubes were added to diethylene glycol and sonicated for 40 minutes to uniformly disperse the carbon nanotubes.

Next, 30mM RuCl ₃ · nH ₂ O and 0.3M sodium acetate (NaAc,> 99%) were added to the dispersed solution, mixed, and stirred to completely dissolve the ruthenium salt.

Next, 20 parts by weight of water was added to the mixed solution, and reacted at 40 GHz for 20 minutes in a microwave oven at 200 ° C. to synthesize ruthenium oxide.

The synthesized ruthenium oxide was quenched with tap water, washed several times with ethanol, water and acetone and dried in an oven at 60 ° C.

Figure 2 is a graph showing the results of Raman analysis of ruthenium oxide synthesized by the microwave-polyol process according to an embodiment of the present invention, the results show a graph of the Raman form of RuO2 generally known ruthenium prepared above It was confirmed that the oxide was produced.

3A is a FETEM photograph of a ruthenium oxide / carbon nanotube composite according to an embodiment of the present invention, and FIG. 3B is an enlarged view of FIG. 3A.

As shown in Figure 3a and 3b, it can be seen that the particles having a nano-size is formed on the carbon nanotubes, the particles are evenly distributed on the carbon nanotubes. It can be seen that the shape of the particles are all spherical. In addition, the growth state of the ruthenium oxide particles composed of nanoparticles of 1 to 2 nm size on the carbon nanotube surface was confirmed.

1 is a process diagram briefly showing a manufacturing process of the transition metal oxide / carbon nanotube composite of the present invention.

Figure 2 is a graph showing the results of Raman analysis of ruthenium oxide synthesized by the microwave-polyol process according to an embodiment of the present invention.

3 is a FETEM photograph of the ruthenium oxide / carbon nanotube composite according to an embodiment of the present invention, Figure 3b is an enlarged view of Figure 3a.

Claims (18)

Acid treating the carbon nanotube powder; Dispersing the acid treated carbon nanotube powder in a polyol solvent; Mixing the dispersed solution, the transition metal salt and the protecting agent in the step; Mixing 5 to 90 parts by weight of water based on 100 parts by weight of the mixed solution of the step; And Method for producing a transition metal oxide and carbon nanotube composite comprising the step of preparing a transition metal oxide and carbon nanotube composite from the mixed solution. The method of claim 1, wherein the step of acid treating the carbon nanotube powder i) adding carbon nanotube powder to an aqueous strong acid solution and acid-treated at 60 to 90 ° C. for 2 to 6 hours; ii) filtering and washing the aqueous solution; And iii) a method for producing a transition metal oxide and carbon nanotube composite, comprising the step of removing the water of the cleaned carbon nanotubes to form a powder. 3. The method of claim 2, Strong acid is a method of producing a transition metal oxide and carbon nanotube composite, characterized in that at least one selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid and mixtures thereof. The method of claim 1, Acid-treated carbon nanotube powder is a method for producing a transition metal oxide and carbon nanotube composites, characterized in that dispersed in a polyol solvent through ultrasonication. The method of claim 1, Acid-treated carbon nanotube powder is a method for producing a transition metal oxide and carbon nanotube composite, characterized in that it comprises 0.001 to 0.1 parts by weight based on 100 parts by weight of the polyol solvent. The method of claim 1, The polyol solvent is transition metal oxide and carbon nano, characterized in that at least one selected from the group consisting of ethylene glycol (EG), diethylene glycol (DEG), tetraethylene glycol (TEG), tetraethylene glycol (TTEG) and tetraethylene polyethylene (TtEg) Method for producing a tube composite. The method of claim 1, Transition metal salt is a method for producing a transition metal oxide and carbon nanotube complex, characterized in that at least one salt selected from the group consisting of ruthenium, nickel, vanadium, cobalt, manganese and titanium. The method of claim 1, Transition metal salt is a method for producing a transition metal oxide and carbon nanotube composite, characterized in that it comprises 0.01 to 0.5 parts by weight based on 1 part by weight of carbon nanotubes. The method of claim 1, Protective agent is a method of producing a transition metal oxide and carbon nanotube composite, characterized in that at least one selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylic acid (PAA) and sodium acetate (NaAc). The method of claim 1, The concentration of the protective agent is a method of producing a transition metal oxide and carbon nanotube composite, characterized in that 0.01M to 5M. delete The method of claim 1, The transition metal oxide and carbon nanotube composite is a method for producing a transition metal oxide and carbon nanotube composite, characterized in that the mixed solution is synthesized by reacting under microwave at 2.45 to 60 GHz, for 10 to 60 minutes. The method of claim 1, A method for producing a transition metal oxide and carbon nanotube composite further comprising the step of washing the finished transition metal oxide and carbon nanotube composite in a washing solvent after drying the reaction at room temperature to 70 ℃. The method of claim 13, The washing solvent is a method for producing a transition metal oxide and carbon nanotube composite, characterized in that at least one selected from the group consisting of ethanol, acetone and water. A transition metal oxide and carbon nanotube composite prepared according to any one of claims 1 to 10 and 12 to 14. The method of claim 15, A transition metal oxide and carbon nanotube composite, wherein the particle diameter of the transition metal oxide is 1 to 2 nm. An article comprising the transition metal oxide of claim 15 and a carbon nanotube composite. The method of claim 17, An article characterized in that any one of a secondary battery, fuel cell, supercapacitor, filtration membrane, chemical detector, or gas sensor.

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