WO2012026686A2

WO2012026686A2 - Nanocomposite including carbon nanotubes and platinum and method of manufacturing the same

Info

Publication number: WO2012026686A2
Application number: PCT/KR2011/005759
Authority: WO
Inventors: Han Oh Park; Jae Ha Kim; Sei Jeong Park; Kug Jin Yun
Original assignee: Bioneer Corporation.
Priority date: 2010-08-25
Filing date: 2011-08-08
Publication date: 2012-03-01
Also published as: KR20120019137A; WO2012026686A3; KR101357145B1

Abstract

Provided are a method of manufacturing a carbon nanotube-platinum composite, including: dispersing carbon nanotubes in a reductive solvent to prepare a dispersion liquid; adding a stabilizer and a platinum precursor to the dispersion liquid to prepare a mixed solution; and heat-treating the mixed solution to reduce the platinum precursor, and a carbon nanotube-platinum composite manufactured by the method. The method is advantageous in that a carbon nanotube-platinum composite can be manufactured, in which platinum particles having a size of several nanometers are uniformly dispersed in carbon nanotubes and the size of platinum particles bonded with carbon nanotubes is uniform.

Description

NANOCOMPOSITE INCLUDING CARBON NANOTUBES AND PLATINUM AND METHOD OF MANUFACTURING THE SAME

The present invention relates to a nanocomposite in which platinum particles are bonded with carbon nanotubes, and a method of manufacturing the same. More particularly, the present invention relates to a carbon nanotube-platinum composite in which platinum particles having a size of several nanometers are uniformly dispersed in carbon nanotubes and the size of platinum particles is uniform, and a method of manufacturing the same.

Carbon nanotubes, which were recently discovered, can be put to practical use in various fields related to energy, environment, electronic materials and the like because they have excellent mechanical strength, thermal conductivity, electrical conductivity and chemical stability. In 1999, Ijima, a researcher of a research institute attached to Nippon Electric Corporation (NEC), first recovered carbon nanotubes that had the shape of a thin and long bamboo tube during the process of analyzing a lump of carbon, which was formed on a graphite cathode by electro-discharging, using a transmission electron microscope (TEM), and then disclosed these carbon nanotubes in the journal “Nature”. Carbon nanotubes are configured such that a graphite plane is rolled in a nanosized diameter, and exhibits metal or semiconductor properties according to the angle and structure of the rolled graphite plane. It is expected that carbon nanotubes will be practically used for ultrafine connecting wires, ultrafine pipes, ultrafine liquid injectors, gas sensors, medical materials using the affinity of carbon for body tissue, etc. The application of carbon nanotubes into electron emission sources, field emission displays (FEDs) and the like is one of the actively-researched fields. Further, the application of carbon nanotubes as the raw materials for solar cells, fuel cell and secondary batteries, which are being highlighted as alternative energy sources, and as high-strength lightweight bulk materials is being actively conducted.

Currently, compared to a carbon nanotube itself, a carbon nanotube-metal composite is a high-performance material which can be used for materials used in the electronics industry, such as electrode materials for field emission flat panel displays, fuel cells and solar cell, raw materials for hydrogen storage units of fuel cells, electromagnetic wave shielding materials, electronic ink, and the like, and high-strength lightweight materials for tool steel, automobile parts, weapons, and the like. This carbon nanotube-metal composite is a novel material which is manufactured by introducing functional groups into carbon nanotubes and then reacting the functional groups with a metal (cobalt, copper, nickel or the like) to chemically bond the carbon nanotubes with metal, and can be effectively used to fabricate field emission displays, hydrogen storage units, electrodes, super capacitors, electromagnetic wave shielding materials, high-strength lightweight products, and the like because they contain a metal component. Here, when the metal particles chemically bonded with carbon nanotubes are nanosized metal particles, the physical properties thereof are different from the original metal particles. Typically, the melting point thereof becomes low. Further, the melting point thereof becomes lower as the size thereof decreases. For this reason, a carbon nanotube-metal composite has peculiar physical properties different from those of conventional carbon nanotubes, thus providing various applications as a new material.

Recently, a new carbon nanotube-metal composite obtained by physically mixing carbon nanotubes and metal particles and then sintering the mixture was developed (P.J.F. Harris, International Materials Reviews, Vol 49, p31-43, 2004). However, this carbon nanotube-metal composite is problematic in that, since metal particles are not bonded with carbon nanotubes, the metal particles conglomerate without being uniformly dispersed in the carbon nanotubes, thus deteriorating the applicability of the carbon nanotube-metal composite. Differently from the above carbon nanotube-metal composite, another new carbon nanotube-metal composite obtained by chemically bonding metal particles with carbon nanotubes was developed. However, this carbon nanotube-metal composite is also problematic in that carbon nanotubes are entirely coated with metal particle to be covered therewith, and thus the characteristics of carbon nanotubes are not exhibited.

Meanwhile, Korean Patent Registration Nos. 616071 and 778094 disclose methods of reducing a metal precursor by introducing a metal precursor and a reductant into a carbon nanotube-dispersed solvent. However, these methods are problematic in that the reaction that reduces the metal precursor using the reductant is not uniform over the entire reaction system, so that the size of the metal particles in the manufactured carbon nanotube-metal composite is not uniform, thereby deteriorating the dispersibility of metal particles in the carbon nanotube-metal composite.

Further, U.S. Patent Publication No. 20070161501 discloses a method of manufacturing a composite in which platinum particles are bonded with carbon nanotubes. However, there is a problem in that this method is complicated because acid-alkali titration must additionally be conducted.

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a carbon nanotube-platinum composite in which platinum particles having a size of several nanometers are uniformly dispersed in carbon nanotubes and the size of platinum particles bonded with carbon nanotubes is uniform, and a method of manufacturing the same.

Another object of the present invention is to provide a method of manufacturing a carbon nanotube-platinum composite, in which small and uniform sized platinum particles can be uniformly dispersed in carbon nanotubes and bonded with carbon nanotubes by adjusting the size of the platinum particles bonded with the carbon nanotubes.

The present inventors have continuously researched in order to accomplish the above objects. As a result, they found that a carbon nanotube-platinum composite in which reduced platinum particles are uniformly dispersed carbon nanotubes can be manufactured by dispersing carbon nanotubes in a reductive solvent selected from polyalcohols, glycol ethers, and mixtures thereof, adding a stabilizer and a platinum precursor thereto and then conducting heat treatment. Particularly, they found that, when a stabilizer was used, the stability of platinum particles was able to be improved during the process of forming platinum particles by the reduction of a platinum precursor, and small and uniform sized platinum particles were able to be formed compared to when a stabilizer was not used.

The reductive solvent according to the present invention serves to disperse carbon nanotubes and to reduce a platinum precursor. This reductive solvent may be selected from polyalcohols, glycol ethers and mixtures thereof.

Since the reductive solvent has moderate reducing ability, the reduction reaction of a platinum precursor is conducted at a proper rate, so that uniform sized platinum particles can be formed, and the agglomeration of the formed platinum particles can be prevented, with the result that the platinum particles can be uniformly dispersed in the manufactured carbon nanotube-platinum composite. More preferably, when a mixed solution of polyalcohol and glycol ether is used as the reductive solvent, the dispersibility of platinum particles is more improved.

As described above, the method of manufacturing a carbon nanotube-platinum composite according to the present invention is advantageous in that various carbon nanotube-platinum composites, in each of which uniform nanosized platinum particles are uniformly dispersed in carbon nanotubes, can be easily manufactured using inexpensive polyalcohol, glycol ether or a mixture thereof as a reductant, and in that it is possible to adjust the size of platinum particles to be small and uniform by using a stabilizer. Further, the method according to the present invention is advantageous in that the carbon nanotube-platinum composite manufactured in this method can be used as an electrode material of solar cells, fuel cells, secondary cells and electronic appliances.

The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

FIG. 1 is a transmission electron microscope (TEM) photograph of a carbon nanotube-platinum composite manufactured in Example 1;

FIG. 2 shows the results of energy dispersive X-ray spectroscopy (EDS) analysis of the carbon nanotube-platinum composite manufactured in Example 1; and

FIG. 3 is a scanning electron microscope (SEM) photograph of a carbon nanotube-platinum composite prepared in Comparative Example 1.

Hereinafter, the present invention will be described in detail.

The present invention provides a method of manufacturing a carbon nanotube-platinum composite, including the steps of: dispersing carbon nanotubes in a reductive solvent to prepare a dispersion liquid; adding a stabilizer and a platinum precursor to the dispersion liquid to prepare a mixed solution; and heat-treating the mixed solution to reduce the platinum precursor.

In the method of manufacturing a carbon nanotube-platinum composite according to the present invention, the carbon nanotubes include single wall carbon nanotubes, double wall carbon nanotubes, thin multi-wall carbon nanotubes, and multi-wall carbon nanotubes.

In the present invention, the principle used to bond platinum with carbon nanotubes is as follows. For example, it is known from the paper by M.W. Marshall et. al. published in Carbon (Vol 44, p1137-1141, 2006) that anionic functional groups, such as carboxylic functional group, are induced to defective sites existing on the surface of commercially-available carbon nanotubes in the process of purifying carbon nanotubes.

When carbon nanotubes are formed by chemical vapor deposition (CVD), it is required to remove the metal catalyst. The metal catalyst is removed by melting it using hydrochloric acid or nitric acid in the process of purifying carbon nanotubes. In this case, acid comes into contact with carbon nanotubes, and the acid causes carboxyl functional groups to be formed on the surface of carbon nanotubes. Therefore, in order to form a larger number of functional groups on the surface of carbon nanotubes, carbon nanotubes may be treated with strong acid.

When carbon nanotubes having an anionic functional group such as a carboxyl group come into contact with a platinum compound dissolved in liquid, dissolved cationic platinum approaches around the carboxyl group in the form of a precursor. Here, when a reduction reaction is conducted by increasing temperature using a reductant, reduced platinum is bonded with carbon nanotubes to manufacture a carbon nanotube-platinum composite. In this case, a stabilizer existing in a mixed solution together with a platinum precursor approaches around cationic platinum and reduced platinum, and serves to control a reaction rate such that the reduction reaction of platinum is stably conducted and to prevent platinum particles from conglomerating and aggregating. Therefore, when a stabilizer is used, small and uniform platinum particles can be uniformly dispersed in carbon nanotubes and bonded to carbon nanotubes therewith compared to when the stabilizer is not used.

In the method of manufacturing a carbon nanotube-platinum composite according to the present invention, the stabilizer may be selected from a surfactant, a water-soluble polymer, amines, and mixtures thereof.

Since the size of platinum particles changes depending on the amount of the stabilizer and the amount of the stabilizer can be adjusted depending on the application of a carbon nanotube-platinum composite, the amount thereof is not subject to any limitations. However, considering the effect of adjusting the size of platinum particles and the economical effect depending on the amount of the stabilizer, the ratio (A:B) of a stabilizer (B) to a platinum precursor (A) by weight may be 1 : 0.01 ~ 100, preferably, 1 : 0.05 ~ 50.

Particularly, when a mixture of a water-soluble polymer and amine is used as the stabilizer, the size of platinum particles formed by the reduction reaction of platinum can be made smaller. Generally, the size of platinum particles formed by using the stabilizer is 10 nm or less, concretely, 1 ~ 10 nm. However, when a mixture of a water-soluble polymer and amine is used as the stabilizer, platinum nanoparticles having a particle size of 10 nm or less, preferably, 6 nm or less can be formed.

Hereinafter, the method of manufacturing a carbon nanotube-platinum composite according to the present invention will be described in stepwise fashion.

In the method of manufacturing a carbon nanotube-platinum composite according to the present invention, first, carbon nanotubes are dispersed in a reductive solvent to prepare a dispersion liquid. Generally, the reduction reaction can be conducted by dispersing carbon nanotubes in an organic solvent and then adding a reductant to the organic solvent. However, the present invention is characterized in that the reduction reaction of platinum can be more completely conducted by using an inexpensive neat reductant.

In this case, sodium borohydride, hydrazine and the like are used as the reductant, but these reductants are disadvantageous in that production costs become high because they are expensive although they have excellent reducing ability, and in that platinum particles synthesized by the reduction reaction are not uniform.

In the method of manufacturing a carbon nanotube-platinum composite according to the present invention, polyalcohols, glycol ethers or mixtures thereof serve as both a solvent and a reductant. That is, the method of the present invention is advantageous in that processes are simple because a separate reductant is not used, and in that, since a solvent acts as a reductant and has moderate reducing ability, a reduction reaction can be entirely conducted at a regular and proper reaction rate, so that uniform-sized platinum particles of several nanometers to several tens of nanometers can be obtained by the reduction reaction of a platinum precursor, with the result that these platinum particles can be uniformly dispersed in carbon nanotubes. Further, the method of the present invention is advantageous in that the obtained platinum particles are uniform in terms of shape because they are spherical particles.

Polyalcohols, glycol ethers or mixtures thereof may be used as the reductive solvent of the present invention. The polyalcohols are compounds having two or more hydroxy groups, and may be selected from the group consisting of glycols represented by Formula 1 below, glycerin, threitol, arabitol, glucose, mannitol, galactitol, and sorbitol. More preferably, the polyalcohols may be glycols.

The glycol ethers are glycols, one or two hydroxy groups of which are substituted with alkyl groups, allyl groups, alkylcarbonyl groups or the like, and may be selected from compounds represented by Formula 2 below. More preferably, the glycol ethers may be glycol ethers having one hydroxy group.

It is more preferred that high-melting reductive solvents, such as threitol, arabitol, glucose, mannitol, galactitol, sorbitol and the like, be mixed with low-melting reductive solvents.

[Formula 1]

H-(OR¹)_n-OH

[Formula 2]

R⁴-(OR²)_m-OR³

(wherein R¹ and R² are each independently selected from straight-chain or branched-chain alkylenes of C2~C10; R³ is selected from a hydrogen atom, an allyl group, an alkyl group of C1~C10, an aryl group of C5~C20, and an aralkyl group of C6~C30; and R⁴ is selected from an allyl group, an alkyl group of C1~C10, an aryl group of C5~C20, an aralkyl group of C6~C30, and alkylcarbonyl group of C2~C10, alkyl of the alkycarbonyl group includes a double bond in a carbon chain, and n and m are each independently an integer of 1 to 100.)

Examples of the glycols may include, but are not limited to, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, hexylene glycol, and the like, more preferably, ethylene glycol and triethylene glycol.

Examples of the glycol ethers may include, but are not limited to, methyl glycol, methyl diglycol, methyl triglycol, methyl polyglycol, ethyl glycol, ethyl diglycol, butyl glycol, butyl diglycol, butyl triglycol, butyl polyglycol, hexyl glycol, hexyl diglycol, ethylhexyl glycol, ethylhexyl diglycol, allyl glycol, phenyl glycol, phenyl diglycol, benzyl glycol, benzyl diglycol, methyl propylene glycol, methyl propylene diglycol, methyl propylene triglycol, propyl propylene glycol, propyl propylene diglycol, butyl propylene glycol, butyl propylene diglycol, phenyl propylene glycol, methyl propylene glycol acetate, and the like.

In the method of manufacturing a carbon nanotube-platinum composite according to the present invention, the process of dispersing carbon nanotubes in the reductive solvent may be conducted using any commonly-known method. Among them, ultrasonic treatment is more advantageous in terms of dispersibility because carbon nanotubes are easily dispersed. It can be observed with an electron microscope that carbon nanotubes become intertwined with each other at the time they are purchased. Since the tangle of carbon nanotubes prevents platinum particles from being uniformly dispersed, it is preferred that ultrasonic treatment is conducted at the time of manufacturing a carbon nanotube-platinum composite.

In the method of manufacturing a carbon nanotube-platinum composite according to the present invention, second, a stabilizer and a platinum precursor are added to the dispersion liquid to prepare a mixed solution.

The platinum precursor may be selected from platinum-containing compounds and mixtures thereof.

The platinum precursor includes any one selected from inorganic platinum salts, such as hydroxy compounds, carbonate compounds, chloride compounds, nitrate compounds; organic platinum complex compounds, such as carboxylate compounds represented by Formula 3 below, ß-diketonate compounds represented by Formula 4 below; hydrates thereof; and mixtures thereof:

[Formula 3]

[Formula 4]

(wherein M is platinum (Pt); R⁵, R⁶ and R⁷ are independently selected from an allyl group, an alkyl group of C1~C10, an aryl group of C5~C20, and an aralkyl group of C6~C30; R⁸ is selected from a hydrogen atom and an alkyl group of C1~C7; and p and q are independently a valence of M.)

The platinum precursor may be selected from platinum nitrate, platinum acetylacetonate, platinum acetate, platinum carbonate, platinum chloride, platinum hydroxide, and hydrates thereof, but is not limited thereto.

As described above, the stabilizer serves to adjust the size of platinum particles to be smaller and more uniform by improving the stability of the platinum precursor and the platinum particles formed by the reduction of the platinum precursor to control a reduction reaction rate and to prevent the platinum particles from conglomerating and aggregating.

The stabilizer may be selected from a surfactant, a water-soluble polymer, amines, and mixtures thereof. More preferably, the stabilizer may be a mixture of a water-soluble polymer and amines.

The surfactant may be selected from a nonionic surfactant, a cationic surfactant, an anionic surfactant, and mixtures thereof. Examples of the nonionic surfactant may include, but are not limited to, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene octyl decyl ether, polyoxyethylene tridecyl ether, polyoxyethylene nonylphenol ether, polyoxyethylene octylphenol ether, polyoxyethylene phenyl ether, polyoxyethylene sorbitan ester, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene glycol, polyoxyethylene oleyl ester, and the like. Examples of the cationic surfactant may include, but are not limited to, dodecyl ammonium chloride, cetyltrimethylammonium bromide, alkylammonium methosulfate, alkyl dimethyl ammonium chloride, and the like. Examples of the anionic surfactant may include sodium stearate, sodium laurate, sodium palmitate, potassium stearate, potassium laurate, potassium palmitate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, and the like.

Example of the water-soluble polymer may include, but are not limited to, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinyl sulfonic acid, polydiallyl dimethyl ammonium chloride, polyvinyl pyrrolidone, polyoxyethylene, polyvinyl acetate, polyvinylcyanoethyl ether, hydroxyethyl cellulose, cellulose sulfate, amylopectin, polyethylene glycol monomethyl ether, polyethylene glycol tert-octylphenyl ether, and the like. More preferably, the water-soluble polymer may be polyvinyl pryrrolidone.

Examples of the amines may include, but are not limited to, propylamine, butylamine, hexylamine, heptylamine, octylamine, decylamine, dodecylamine, octadecylamine, oleylamine, and the like. More preferably, the amine may be oleylamine.

It is preferred that the stabilizer be a mixture of a water-soluble polymer and amine because the size of platinum particles formed by the reduction reaction can be made smaller and spherical platinum particles can be uniformly formed. In this case, it is more preferred that the mixture of a water-soluble polymer and amine include polyvinyl pyrrolidone or oleylamine.

In the method of manufacturing a carbon nanotube-platinum composite according to the present invention, third, the mixed solution of carbon nanotubes and a platinum precursor is heat-treated to reduce the platinum precursor. It is preferred that this process be performed after a reactor is charged with an inert gas such as nitrogen or the like. The inert gas serves to prevent the platinum formed by the reduction reaction from being oxidized and to prevent this platinum from reacting with oxygen at high temperature and exploding the reactor. The reduction reaction must be conducted by charging the reactor with inert gas and then heating the mixed solution to a predetermined temperature.

The reductive solvent of the present invention does not exhibit a reduction effect at room temperature, but causes a reduction reaction when the heat-treatment temperature increases to a predetermined temperature or more. Although the increase in the heat treatment temperature may not be limited because the heat treatment temperature changes depending on the composition of the reductive solvent, it is preferred that the heat treatment be conducted within a temperature range of 60 to 300℃. When the heat treatment temperature is below 60℃, the reduction reaction is not sufficiently conducted, and thus platinum particles cannot be easily formed. Further, when the heat treatment temperature is above 300℃, the components of the mixed solution can be decomposed and volatilized, so that the reduction reaction cannot be stably conducted, and the reduction reaction at excessively high temperature can be disadvantageous economically.

Meanwhile, the method of manufacturing a carbon nanotube-platinum composite according to the present invention may include the steps of filtering, washing and drying, which are normally performed.

FIG. 1 is a transmission electron microscope (TEM) photograph of a carbon nanotube-platinum composite manufactured according to an example of the present invention. As shown in FIG. 1, it can be ascertained that spherical platinum particles having a particle size of several nanometers, specifically, 5 ~ 6 nm are uniformly dispersed in the carbon nanotube-platinum composite, and are bonded with carbon nanotubes.

FIG. 2 shows the results of energy dispersive X-ray spectroscopy (EDS) analysis of the carbon nanotube-platinum composite manufactured according to an example of the present invention. As shown in FIG. 2, it can be ascertained that the synthesized metal is platinum. In this case, the carbon comes from the carbon nanotubes.

Hereinafter, the present invention will be described in detail with reference to the following Examples.

However, the following Examples are set forth only to illustrate the present invention, and the scope of the present invention is not limited thereto.

Manufacture of carbon nanotube-platinum composite

[Example 1]

0.3 g of multi-wall carbon nanotubes (manufactured by Hanhwa Nanotech Corporation) were put into a 500 mL round four-neck flask reactor, and then 280 mL of ethylene glycol (manufactured by Partech C&T Corporation) was added thereto. The first mixture was stirred for 30 minutes, and then the round four-neck flask reactor was put into an ultrasonic cleaner to disperse carbon nanotubes in ethylene glycol using ultrasonic waves for 3 hours. In this case, the temperature of the four-neck flask reactor must not exceed 50℃. After the ultrasonic treatment, the round four-neck flask reactor was mounted with a stirrer and was connected with a thermometer and a condenser for cooling. Subsequently, 1.68 g of polyvinyl pyrrolidone (PVP, supplied by by Sigma Aldrich Corporation, weight-average molecular weight (Mw): 40000) and 2.8 mL of oleylamine (supplied by by Sigma Aldrich Corporation) were put into the round four-neck flask reactor, and, subsequently, 0.259 g of platinum acetylacetonate (supplied by by Sigma Aldrich Corporation) was put thereinto to form a second mixture. A vacuum pump was connected to the reactor to remove air from the reactor and to substitute air with nitrogen. When nitrogen was continuously introduced, nitrogen was discharged out of the reactor, thus preventing oxygen from flowing into the reactor. A mantle was provided under a flask, and the second mixture was stirred at a rotation speed of 400 rpm for 30 minutes using the stirrer. Subsequently, the reactor was heated to 200℃ for 40 minutes to react the second mixture for 1 hour. After the reaction was completed, the reactor was slowly cooled to room temperature for 3 hours to synthesize a carbon nanotube-platinum composite. The synthesized carbon nanotube-platinum composite was washed and filtered using a filter paper, washed with 1 L of ethyl acetate and hexane 3 ~ 5 times, and then dried in an oven at 80℃ to obtain carbon nanotube-platinum composite. As the result of transmission electron microscope (TEM) analysis of the obtained carbon nanotube-platinum composite, as shown in FIG. 1, it can be ascertained that spherical platinum particles having a particle size of 5 ~ 6 nm are uniformly dispersed in the carbon nanotube-platinum composite. Further, as the result of energy dispersive X-ray spectroscopy (EDS) analysis thereof, as shown in FIG. 2, it can be ascertained that the synthesized metal is platinum.

[Comparative Example 1]

0.3 g of multi-wall carbon nanotubes (manufactured by Hanhwa Nanotech Corporation) were put into a 500 mL three-neck flask reactor, and then 500 mL of ultrapure water and 1.0 g of sodium dodecyl sulfate (SDS, supplied by Sigma Aldrich Corporation) were added thereto. The first mixture was stirred for 30 minutes, and then the three-neck flask reactor was put into an ultrasonic cleaner to disperse carbon nanotubes in ultrapure water using ultrasonic waves for 2 hours. In this case, the temperature of the three-neck flask reactor must not exceed 50℃. After the ultrasonic treatment, the three-neck flask reactor was disposed on a hot plate, and then the first mixture was stirred at a rotation speed of 400 rpm. Subsequently, 0.796 g of chloroplatinic acid was added to the first mixture, and then stirred for 30 minutes to form a second mixture. Thereafter, the pH of the second mixture was measured using a pH-meter. In this case, the pH thereof was 2.15. The temperature of the hot plate was set to 40℃, and 1 mL of hydrazine (manufacture by Samchun Pure Chemical Co., Ltd.) was added to the second mixture using a syringe pump (EYELA, MP-1000) for 1 minute at a predetermined flow rate to form a third mixture. After the third mixture had sufficiently stirred for 2 hours and its pH was measured using a pH-meter, the pH thereof was 8.34, which represents a weak base. This third mixture was washed with l L of methanol and ultrapure water three or four times, and then dried in an oven at 80℃ to obtain a carbon nanotube-platinum composite. A scanning electron microscope (SEM) analysis of the obtained carbon nanotube-platinum composite, as shown in FIG. 3, shows that there are large and nonuniform platinum particles having a particle size of about 100 nm. That is, when hydrazine is used as a commonly-known reductant, it can be seen that the sizes of platinum particles are large and nonuniform, differently from the uniform platinum nanoparticles having a particle size of 5 nm, obtained in Example 1.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Simple modifications, additions and substitutions of the present invention belong to the scope of the present invention, and the specific scope of the present invention will be clearly defined by the appended claims.

Claims

A method of manufacturing a carbon nanotube-platinum composite, comprising:

dispersing carbon nanotubes in a reductive solvent to prepare a dispersion liquid;

adding a stabilizer and a platinum precursor to the dispersion liquid to prepare a mixed solution; and

heat-treating the mixed solution to reduce the platinum precursor.
The method of claim 1, wherein the stabilizer is selected from a surfactant, a water-soluble polymer, an amine, and mixtures thereof.
The method of claim 2, wherein the surfactant is selected from a nonionic surfactant, a cationic surfactant, an anionic surfactant, and mixtures thereof.
The method of claim 3, wherein the nonionic surfactant is selected from polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene octyl decyl ether, polyoxyethylene tridecyl ether, polyoxyethylene nonylphenol ether, polyoxyethylene octylphenol ether, polyoxyethylene phenyl ether, polyoxyethylene sorbitan ester, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene glycol, polyoxyethylene oleyl ester, and mixtures thereof; the cationic surfactant is selected from dodecyl ammonium chloride, cetyltrimethylammonium bromide, alkylammonium methosulfate, alkyl dimethyl ammonium chloride, and mixtures thereof; and the anionic surfactant is selected from sodium stearate, sodium laurate, sodium palmitate, potassium stearate, potassium laurate, potassium palmitate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, and mixtures thereof.
The method of claim 2, wherein the water-soluble polymer is selected from polyethylene glycol, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinyl sulfonic acid, polydiallyl dimethyl ammonium chloride, polyvinyl pyrrolidone, polyoxyethylene, polyvinyl acetate, polyvinylcyanoethyl ether, hydroxyethyl cellulose, cellulose sulfate, amylopectin, polyethylene glycol monomethyl ether, polyethylene glycol tert-octylphenyl ether, and mixtures thereof.
The method of claim 2, wherein the amine is selected from primary amines, secondary amines, tertiary amines, aromatic amines, and mixtures thereof.
The method of claim 6, wherein the amine is selected from propylamine, butylamine, hexylamine, heptylamine, octylamine, decylamine, dodecylamine, octadecylamine, oleylamine, and mixtures thereof.
The method of claim 2, wherein the stabilizer is a mixture of a water-soluble polymer and an amine.
The method of claim 8, wherein the mixture of the water-soluble polymer and the amine includes at least one of polyvinyl pyrrolidone and oleylamine.
The method of claim 1, wherein the reductive solvent is selected from the group consisting of polyalcohols, glycol ethers, and mixtures thereof.
The method of claim 10, wherein the polyalcohol is selected from glycols represented by Formula 1 below, glycerin, threitol, arabitol, glucose, mannitol, galactitol, and sorbitol; and the glycol ether is selected from compounds represented by Formula 2 below:

[Formula 1]

H-(OR¹)_n-OH

[Formula 2]

R⁴-(OR²)_m-OR³

wherein R¹ and R² are each independently selected from straight-chain or branched-chain alkylenes of C2~C10; R³ is selected from a hydrogen atom, an allyl group, an alkyl group of C1~C10, an aryl group of C5~C20, and an aralkyl group of C6~C30; and R⁴ is selected from an allyl group, an alkyl group of C1~C10, an aryl group of C5~C20, an aralkyl group of C6~C30, and alkylcarbonyl group of C2~C10, alkyl of the alkycarbonyl group includes a double bond in a carbon chain, and n and me are each independently an integer of 1 to 100.
The method of claim 11, wherein the glycol is selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, and hexylene glycol; and the glycol ether is selected from methyl glycol, methyl diglycol, methyl triglycol, methyl polyglycol, ethyl glycol, ethyl diglycol, butyl glycol, butyl diglycol, butyl triglycol, butyl polyglycol, hexyl glycol, hexyl diglycol, ethylhexyl glycol, ethylhexyl diglycol, ally glycol, phenyl glycol, phenyl diglycol, benzyl glycol, benzyl diglycol, methyl propylene glycol, methyl propylene diglycol, methyl propylene triglycol, propyl propylene glycol, propyl propylene diglycol, butyl propylene glycol, butyl propylene diglycol, phenyl propylene glycol, and methyl propylene glycol acetate.
The method of claim 1, wherein the platinum precursor includes any one selected from hydroxy compounds, carbonate compounds, chloride compounds, nitrate compounds, carboxylate compounds represented by Formula 3 below, ß-diketonate compounds represented by Formula 4 below and hydrates thereof, and mixtures thereof:

[Formula 3]

[Formula 4]

wherein M is platinum (Pt); R⁵, R⁶ and R⁷ are independently selected from an allyl group, an alkyl group of C1~C10, an aryl group of C5~C20, and an aralkyl group of C6~C30; R⁸ is selected from a hydrogen atom and an alkyl group of C1~C7; and p and q are independently a valence of M.
The method of claim 13, wherein the platinum precursor is selected from platinum nitrate, platinum acetylacetonate, platinum acetate, platinum carbonate, platinum chloride, platinum hydroxide, and hydrates thereof.
A carbon nanotube-platinum composite, manufactured by the method of any one of claims 1 to 14.
The carbon nanotube-platinum composite of claim 15, wherein the carbon nanotube-platinum composite includes spherical platinum particles having a diameter of 1 to 10 nm and carbon nanotubes.