KR101753126B1 - Manufacturing method of graphene/platinum-gold nano composite and graphene/platinum-gold 3D nano composite using the same - Google Patents

Abstract

The present invention provides a method for preparing a graphene oxide colloid solution comprising: a) preparing a graphene oxide colloid solution; b) preparing a platinum-gold nanocomposite colloidal solution; c) mixing the colloidal solution of steps a) and b) to prepare a mixed colloidal solution; d) aerosol droplet spraying said mixed colloid solution; And e) transporting the sprayed droplets to a heating furnace and pyrolyzing the grains to obtain a graphene-platinum-gold nanocomposite, and a process for producing the graphene-platinum-gold nanocomposite.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphene-platinum-gold nanocomposite and a graphene / platinum-gold 3D nanocomposite,

The present invention relates to a method for producing a graphene-platinum-gold nanocomposite and a graphene-platinum-gold three-dimensional nanocomposite prepared therefrom and a fuel cell including the nanocomposite.

In addition to the development of conventional energy technologies, research on new types of environmentally friendly and energy-efficient energy transmission media has been actively pursued. Among them, fuel cell (fuel cell) has recently become popular.

Fuel cells are devices that generate electrical energy by electrochemically reacting fuel and oxidizer. Depending on the operating temperature and type of main fuel, the polymer electrolyte fuel cell and the direct methanol fuel cell operate at low temperatures. Particularly, the performance depends on the activity of the electrode catalyst. In addition, such fuel cells are highly efficient, environmentally friendly energy sources, and have unlimited potential markets for portable batteries for mobile phones and notebooks, as well as households, industrial and power generators, as substitutes for boilers. Therefore, due to the nature of the spotlight, countries around the world are fiercely competing to advance the fuel cell market, and it is urgent to develop more advanced technologies in Korea.

On the other hand, platinum has been used as an electrode catalyst since the development of a polymer electrolyte fuel cell and a direct methanol fuel cell. However, the activity is high but it is expensive. Therefore, studies for increasing utilization rate of platinum by highly dispersing platinum in carbon have been progressing steadily. As a strategy for this, a method of attaching a platinum nanomaterial to a high surface area and porous solid support has been extensively studied, Activated carbon, carbon nanotubes (CNTs), carbon nanosheets, and silica gel were used as carriers for platinum nanoparticles for use as catalysts. The open structure of such a support can be advantageous as an additional catalyst because it can promote the diffusion and adsorption of reactants, and it is now necessary to develop a more efficient carrier material.

Also, it is a material that can induce various self-assembly phenomenon through chemical transformation of gold and silver particle surface. Depending on the size and shape of the particle, various fields such as catalyst, chemical and biosensor, photoelectric device, optical device, In recent years, the field of application and usefulness have been increasing.

Gaphene (GR), on the other hand, is the first 'two-dimensional crystal' created by mankind that exists as a unique structure of a two-dimensional nanosheet composed of hexagonal sp ² shell carbon atoms of single atom-size thickness , Can be used as a substrate material for electrocatalysts for fuel cells due to their unique electrical conductivity and structural properties such as carbon nanotubes and carbon nanofibers. Also, graphene can be produced by direct peeling of graphite sheet or by chemical reduction of graphene oxide (GO) nanosheet, and GR that is chemically synthesized from GO is also referred to as reduced graphene oxide (rGO) by its nature . Thus, in recent years, GR-based composite materials have attracted worldwide attention due to their improved material properties such as electrical conductivity, chemical properties, and electrical properties, and many studies have been reported on the production of GR-based composites.

In addition, GO (graphene oxide) is a thermally unstable material that can be easily deoxidized by reduction by heat treatment. Some of the partially oxidized graphite during the progress of the thermal reduction of GO is reduced As in the case of graphene, it is converted into fully oxidized CO ₂ form. The unstable thermal properties of GO are applied to the synthesis of GR nanosheets from GO nanosheets by spraying GO nanosheet colloidal droplets without any reducing agent in the hot gaseous state. In addition, if the colloidal droplets of the GO nanosheets and the Pt precursor solution are subjected to the same heat treatment, the Pt precursor and the GO can be simultaneously reduced by pyrolysis, and then the Pt nanoparticles filled with the GR nanosheets can be synthesized . Recently, it has been reported that GR nanosheets made of nanoparticles of noble metals and transition metal oxides can be prepared through a redox reaction such as a domino by a flame treatment using a GO film containing a metal precursor and a potassium salt.

However, conventional graphene researches have been conducted to synthesize composites using various liquid chemical methods such as hydrazine, impregnation-reduction method, colloid method, chemical reduction by polyol method, and so on. The complexes prepared in addition to the steps sometimes exhibit severe lamination or aggregation and the severe lamination phenomenon of the GR nanosheets has a problem in that the super-high surface area merit of the two-dimensional nanomaterial is lost.

Although the platinum catalyst itself is a very effective material for a direct methanol fuel cell, there is a problem such as high production cost, low efficiency, limited platinum availability, etc. Therefore, It is a fact that repeatedly.

Korean Patent Publication No. 10-2013-0121799 (November 06, 2013)

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method for producing a graphene-platinum-gold nanocomposite in which a low efficiency and a limited platinum availability of a conventional platinum catalyst are improved.

Another object of the present invention is to provide a direct methanol fuel cell comprising the graphene-platinum-gold nanocomposite.

The present invention relates to a method for producing a graphene-platinum-gold nanocomposite and a graphene-platinum-gold three-dimensional nanocomposite prepared therefrom.

One aspect of the present invention is

a) preparing a graphene oxide colloidal solution;

b) preparing a platinum-gold nanocomposite colloidal solution;

c) mixing the colloidal solution of steps a) and b) to prepare a mixed colloidal solution;

d) aerosol droplet spraying said mixed colloid solution; And

e) pyrolyzing the atomized droplets by transferring them to a heating furnace to obtain a graphene-platinum-gold nanocomposite;

Platinum-gold nanocomposite comprising the graphene-platinum-gold nanocomposite.

Wherein in the present invention step b) colloidal solution of sodium tetrachloro player TEA (Na ₂ PtCl _4), potassium tetrachloro player TEA (K ₂ PtCl _4), platinum chloride (PtCl _2), chloroplatinic acid (H ₂ PtCl ₆ ) tetrachloride, chloroplatinic acid (H ₂ PtCl ₄₎ and four amine chloro platinum _{(Pt (NH 3) 4Cl 2} ) or more of either or both selected from the platinum precursor tetrachloride Keumsan (HAuCl _4), trichloroacetic gold (AuCl ₃₎ tetrachloride gold potassium (KAuCl _4), hydroxide, gold (Au (OH) _3), oxide of gold (Au ₂ O _3), bromide, gold (AuBr ₃₎ and sulfide gold (Au ₂ S ₃₎ one or more cash is selected from the specific and tetrakis (hydroxymethyl) phosphonium chloride, sodium borohydride (NaBH _4), formaldehyde (HCHO), sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO _3), methanol (CH ₃ OH), citrate (C ₆ H ₈ O ₇ ) and sodium citrate (Na ₃ C ₆ H ₅ O ₇ ).

The mixed colloidal solution may contain 0.01 to 10% by weight of a graphene oxide colloidal solution and 0.001 to 1% by weight of a platinum-gold nanocomposite colloidal solution, 0.001 to 1% by weight of a reducing agent, and the balance solvent.

In the present invention, the temperature of the heating furnace may be 150 to 400 ° C.

Another aspect of the present invention relates to a graphene-platinum-gold three-dimensional nanocomposite prepared by a method produced by the above method.

Another aspect of the present invention is directed to a direct methanol fuel cell comprising the graphene-platinum-gold three-dimensional nanocomposite.

The graphene-platinum-gold three-dimensional nanocomposite according to the present invention and its manufacturing method are manufactured by crumpled paper ball in three-dimensional form without severe lamination or aggregation which is a disadvantage of conventional metal doped graphene And it is possible to maintain super high surface area which is an advantage of graphene.

Also, by combining platinum and gold with graphene, it is possible to improve the high production cost, low efficiency and limited usability, which are disadvantages of platinum.

FIG. 1 illustrates a method of manufacturing a graphene-platinum-gold nanocomposite according to an embodiment of the present invention.
2 shows an XRD pattern of a graphene-platinum-gold nanocomposite according to an embodiment of the present invention.
FIG. 3 shows a cyclic current-voltage curve of a graphene-platinum-gold nanocomposite according to an embodiment of the present invention.
FIG. 4 shows a cyclic current-voltage curve according to the graphene oxide content or the content ratio of the platinum-gold alloy nanoparticles of the graphene-platinum-gold nanocomposite according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. It should be understood, however, that the invention is not limited thereto and that various changes and modifications may be made without departing from the spirit and scope of the invention.

Unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

In addition, the following drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms, and the drawings presented below may be exaggerated in order to clarify the spirit of the present invention. Also, throughout the specification, like reference numerals designate like elements.

Also, the singular forms as used in the specification and the appended claims are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The process for preparing a graphene-platinum-gold nanocomposite according to the present invention comprises

a) preparing a graphene oxide colloidal solution;

b) preparing a platinum-gold nanocomposite colloidal solution;

c) mixing the colloidal solution of steps a) and b) to prepare a mixed colloidal solution;

d) aerosol droplet spraying said mixed colloid solution; And

e) The sprayed droplets are transferred to a heating furnace to pyrolyze the graphene-platinum-gold nanocomposite ;

. ≪ / RTI >

In the present invention, the graphene oxide is a thermally unstable material which can be easily deoxidized by reducing the graphene by a chemical heat treatment. The reducing graphene oxide may be prepared by adding a reducing agent, or may be formed by a chemical vapor deposition ), A chemical surface treatment method, and the like. The grain shape of the graphene oxide is not limited to the shape, but it is preferable to have a sheet.

The graphene oxide colloid liquid includes graphene oxide and a solvent. The solvent is not limited to the kind used in the art, but acetone, methyl ethyl ketone, methyl alcohol, ethyl alcohol, iso Propyl alcohol, butyl alcohol, ethylene glycol, polyethylene glycol, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, hexane, cyclohexanone, toluene, It is preferable that at least one of dichlorobenzene, dimethylbenzene, trimethylbenzene, pyridine, methylnaphthalene, nitromethane, acrylonitrile, octadecylamine, aniline and dimethylsulfoxide is used.

The graphene oxide colloid solution may be formed using at least one selected from a homogenizer, an ultrasonic machine, and a high-pressure homogenizer for easy dispersion of the graphene oxide. Preferably, an ultrasonic machine is used Vertical, horizontal and all directions of shear stress are applied, which is effective for hollow particle production. At this time, the kind of the ultrasonic machine and the irradiation time can be freely adjusted according to the quantity and concentration of the dispersion and the manufacturing conditions of the graphene hollow particles.

In the present invention, the platinum-gold nanocomposite colloid liquid may further include a platinum precursor, a gold precursor, and a reducing agent, and may further include a solvent capable of dissolving the materials.

In the present invention, the platinum precursor is not limited to the present invention but may be selected from the group consisting of sodium tetrachloroplatinate (Na ₂ PtCl ₄ ), potassium tetrachloroplatinate (K ₂ PtCl ₄ ), platinum chloride (PtCl ₂ ) (H ₂ PtCl ₆₎ tetrachloride, chloroplatinic acid (H ₂ PtCl ₄₎ and four amine chloro platinum _{(Pt (NH 3) 4Cl 2} ) which may include one or two or more, and more preferably from H ₂ PtCl ₆ is selected from It is easy to spray droplets onto the aqueous solution and it is possible to disperse easily.

The gold precursor in the present invention include, but are not limited in the present invention as with the platinum precursor, tetrachloride Keumsan _{(HAuCl 4, Hydrogen tetrachloro aurate (} III)), trichloroacetic gold (AuCl _3, Gold trichloride), titanium tetrachloride potassium gold (KAuCl _4, (Au) ₃ , Gold (III) hydroxide, Au ₂ O ₃ , Gold oxide) and gold sulfide (Au ₂ S ₃ , Gold sulfide), gold bromide (AuBr ₃ ), tetrachloro-gold (ⅲ) sodium (NaAuCl4), tetrachloro Keumsan ammonium (NH ₄ AuCl _4), tetrachloro Keumsan lithium (LiAuCl _4), tetrabromo-raising potassium (KAuBr _4), and tetrabromo-raising sodium ( NaAuBr ₄ ). Preferably, the use of tetrachloromethane is preferred because it is easy to spray droplets onto the aqueous solution in the same manner as the platinum precursor, and can be easily dispersed.

In the present invention, the platinum-gold nanocomposite colloid solution does not limit the content ratio of the metal precursor but it is preferable that the content (W _Pt ) of the platinum precursor is larger than the content (W _Au ) of the gold precursor. More specifically, W _Pt / W _Au is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, because electrochemical properties are improved.

In the present invention, the content of the platinum precursor and the gold precursor is not limited to the present invention, but is preferably 0.01 to 0.1 wt% of the entire composition.

In the present invention, the reducing agent is not limited to the kind as long as it can reduce the metal precursor, and may be an organic material or an inorganic material. Examples of the reducing agent in the present invention include tetrakis (hydroxymethyl) phosphonium chloride, sodium borohydride (NaBH ₄ ), formaldehyde (HCHO), sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ) (CH ₃ OH), citric acid (C ₆ H ₈ O ₇ ), and sodium citrate (Na ₃ C ₆ H ₅ O ₇ ). The reducing agent may be an electroactive polymer.

In the present invention, the reducing agent is not limited to the present invention, but it is preferably contained in an amount of 0.001 to 1% by weight, preferably 0.1 to 0.5% by weight.

In the present invention, the solvent is not limited to any kind as far as it can effectively disperse the gold precursor and the platinum precursor, and is preferably selected from water, ethanol, isopropanol, N, N-dimethylformamide, Mixtures may be used.

Next, a mixed colloidal solution may be prepared by mixing the graphene oxide colloid solution and the platinum-gold nanocomposite colloid solution prepared as described above. At this time, as in the case of the graphene oxide colloid solution, it is preferable to use at least one selected from a homogenizer, an ultrasonic machine and a high-pressure homogenizer for easy mixing and dispersion of the mixed colloid solution, and preferably using an ultrasonic machine Platelet-gold nanocomposite in which platinum and gold are uniformly dispersed by applying shear stress in the vertical, horizontal and all directions. At this time, the kind of the ultrasonic wave and the irradiation time can be freely adjusted according to the quantity of the dispersion, the concentration, and the manufacturing conditions of the graphene nanocomposite.

The mixed colloidal solution may contain 0.01 to 10% by weight of a graphene oxide colloidal solution and 0.001 to 1% by weight of a platinum-gold nanocomposite colloid solution, 0.001 to 1% by weight of a reducing agent and a residual solvent, The adjustment of the graphene oxide colloid solution in the mixed colloidal solution to 0.1 to 1 wt% and the platinum-gold nanocomposite colloid solution to 0.01 to 0.1 wt% may increase the catalytic activity due to the increase in the electrochemical surface area during the methanol oxidation reaction .

Next, the mixed colloidal liquid is sprayed by aerosol droplets. In this step, the spraying method and the spraying device are not limited, and preferably sprayed through an ultrasonic atomizer. Particularly, when an ultrasonic atomizer is used, it is very advantageous to produce nanocomposites very rapidly and continuously, and the process time is very short as a few seconds, and there is no need of any post-heat treatment or chemical treatment such as a reducing agent.

It is preferable that the ultrasonic atomizer during the droplet spraying is sprayed at a frequency of 1 to 2 MHz because the self-assembly process can easily occur in the pyrolysis process.

The sprayed droplets are transferred to a heating furnace and pyrolyzed in the same manner as in the step (e), thereby preparing a graphene-platinum-gold nanocomposite. At this time, an inert gas such as neon (Ne) or argon (Ar) is preferably used as the carrier gas. At this time, it is preferable that the carrier gas is supplied at a rate of 0.1 to 5 L / min.

The tubular heating furnace may be a furnace commonly used in the art, and is not limited to the form and the like. In a preferred form, the length of the tubular heating furnace is preferably 20 to 50 cm, and the heating zone may have a diameter of 10 to 50 mm. The temperature of the heating furnace is preferably maintained at 400 to 1,000 ° C, more preferably 600 to 900 ° C. When the temperature is lower than 400 ° C., the crystallinity of the metal supported inside the nanocomposite is lowered. When the temperature is higher than 1000 ° C., unnecessary thermal energy consumption is increased during thermal decomposition.

When the graphene-platinum-gold nanocomposite according to the present invention passes through the pyrolysis-type tubular heating furnace of the droplet, the nanocomposite is formed by the binding of the graphene oxide.

The term " self-assembly " used in the present invention means the spontaneous formation of a composite structure from a basic molecule without the aid of a specific substance or catalyst. In the present invention, graphene oxide It means the formation process of the complex.

More specifically, when the aerosol droplets transferred to the tubular furnace by the carrier gas pass through the heating zone in the heating furnace, self-assembly of the graphene oxide occurs. First, when the solvent present in the aerosol droplet evaporates, graphene oxide particles are gathered together by capillary molding. This is also called crumpling. At the same time, when the mixed metal precursors are dried with the metal nanoparticles, the graphene oxide can be thermally reduced by the high temperature to become a graphene nanocomposite. The reduction time may be 20 to 60 minutes, but is not limited thereto.

When the colloidal solution is included in the preparation of the dispersion, graphene oxide particles are wrapped around the surface of the polymer particles by capillary molding when the solvent in the aerosol droplet evaporates due to the self-assembly phenomenon. At the same time, the polymer particles serving as a template are deteriorated and removed, and the graphene oxide can be thermally reduced by high temperature to become graphene hollow particles. The reduction time may be 20 to 60 minutes, but is not limited thereto.

The transport gas and graphene nanocomposite passing through the furnace collect only pyrolyzed nanocomposites. The collection is not limited to apparatuses and methods such as filters commonly used in the art or collection methods using water. In the case of using a filter, it is preferable to adjust the size of the mesh in consideration of the average diameter of the nanocomposite to be produced, and it is preferable to use a Teflon filter membrane although it is not limited to the material.

The nanocomposite prepared through the above process may have an average diameter of 0.5 to 2 탆, a surface area of 100 to 200 m 2 / g, and an average diameter of the metal nanoparticles carried in the nanocomposite may be 0.01 to 10 nm, but is not limited thereto. When the average diameter is less than 0.5 탆, the amount of metal that can be supported is small, so that it is difficult to have desired catalytic properties in the present invention. When the average diameter exceeds 2 탆, the metal supported nanocomposite It can be difficult to process the secondary workpiece. However, the present invention is not limited thereto, and the average diameter and the like can be freely adjusted according to the pyrolysis time, the temperature, and the number of laminated layers of a single layer of graphene oxide.

The graphene-platinum-gold nanocomposite prepared according to the present invention can be utilized as a catalyst of a direct methanol fuel cell including the graphene-platinum-gold nanocomposite.

As used herein, the term " fuel cell " refers to a fuel cell that does not require replacement or charging of a battery, but instead supplies fuel, such as hydrogen or methanol, Conversion. The advantages of fuel cells are high efficiency (about 60% of energy conversion efficiency), availability of various fuels as a pollution-free energy source, advantages of small area and short construction period, It is expected that the potential market size will be very large if the operation of fuel cell vehicle, which is the next generation transportation device, is put into practical use in a wide variety of applications, ranging from power generation to distributed power generation for household and electric power business. In particular, proton exchange membrane (PEM) fuel cells are attracting attention as energy sources for automobiles and transportation that require greater power.

The graphene-platinum-gold nanocomposite according to the present invention exists in a form in which platinum-gold alloy nanoparticles are mixed in the inside, so that the surface area, especially the electrochemical surface area, can be dramatically increased, And an active region is formed in a large amount to increase catalytic activity in the methanol oxidation reaction.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples and comparative examples are only for illustrating the present invention in more detail, and the present invention is not limited by the following examples and comparative examples.

The materials used in the following examples and comparative examples, and the equipment and physical properties used in the experiments are as follows.

(Graphene oxide)

Graphite powders (99.9% purity Alfa Aesar, USA) were mixed and filtered using NaNO ₃ , H ₂ SO ₄ and KMnO ₄ according to the Hummer's method and then washed and dried thoroughly before synthesis. The prepared graphene oxide was in the form of a plate and had an average particle diameter of 500 nm.

(Electrochemical properties)

Platinum-gold complexes were prepared using electrochemical devices (VSP, Bio-Logics, USA) together with working electrodes, respectively, using a two-dimensional and three-dimensional graphene- Respectively. The graphene-platinum-gold complex was dispersed colloidally through low resistance deionized distilled water (DI water, ~ 18 MΩ), ethanol and Nafion (Sigma Aldrich, 5%). Then, the prepared colloidal solution (10 mu m) was dropped on a glassy carbon electrode (thickness: 3 mm) and left at room temperature. The electrochemical device includes a glass-like carbon electrode coated with a graphene-platinum-gold complex as a working electrode, a reference electrode made of silver-silver chloride and a counter electrode made of a platinum foil Respectively.

In addition, methanol-cycle voltage-current curve of the electro-oxidation (CV, Cyclic voltammogram) measurements, the potential range of 1.0 V from 0 (vs. SCE), 50 ^mVs-scan speed of the range of ^1, 0.05 MH ₂ SO ₄ with 1 M CH ₃ OH, and pure nitrogen gas was injected for 15 minutes to remove the oxygen dissolved in the electrolyte before the cyclic voltammetry experiment.

(Composite properties)

The graphene-platinum-gold complexes prepared through Examples and Comparative Examples were observed through a transmission electron microscope (TEM, CM12, Phillips USA) and a scanning electron microscope (FE-SEM, Sirion, FEI, USA). The electrical mixing and binding energy of the graphene-platinum-gold composite was measured by using an energy dispersive X-ray spectroscope (EDS: JSM-6380LA, JEOL, Japan) and an x-ray photoelectron spectroscope (XPS: ESCA LAB 250 Thremo Fisher Scientific, USA) .

The specific surface area was determined by N ₂ adsorption-desorption isotherm (BET; Tristar 3000, Micromeritics, USA) and data collection was performed using a static volume method using a Quadrasorb Quantachrome instrument .

The crystallinity of the prepared particles was analyzed by using an X-ray diffractometer (XRD, Rigaku, RTP 300 RC, Japan) at room temperature and thermogravimetric analysis (DTG-60H, Shimadzu, Japan) 25 to 1000 < 0 > C at a rate of 5 [deg.] C / min to measure the change in metal weight in the composite.

(Example 1)

H ₂ PtCl ₆ 6H ₂ O and HAuCl ₄ 3H ₂ O were prepared as a metal precursor solution in graphene oxide (GO) prepared as described above, and NaBH ₄ was mixed with a reducing agent. At this time, the reducing agent was mixed with 0.25 wt% of the whole colloid mixture, and the Pt / Au weight ratio was 3.0, 1.0, 0.33 (1/3) and the graphene oxide was 0.5 wt%. The addition amount of platinum and gold was maintained at 1/10 weight ratio (0.05 wt%) of graphene oxide.

After the colloid mixture was stirred at room temperature for 1 hour until it turned brown to black, the colloid mixture was sprayed through a vibrator of an ultrasonic atomizer operating in the frequency range of 1.7 MHz and the droplets sprayed from the precursor solution were fed at a feed rate The graphene-platinum-gold nanocomposite of the three-dimensional shape was prepared by transferring it into an electric tubular furnace having a heating zone of 30 cm in diameter at a heating temperature of 200 ° C using 1.0 L / min of argon gas. The prepared nanocomposites were collected by using a Teflon filter membrane under vacuum condition. The surface area and current density ratio (I _f / I _b ) of the prepared nanocomposites were measured and described in Tables 1 and 2.

(Comparative Example 1)

A two-dimensional graphene-platinum-gold nanocomposite in the form of a film was prepared by using the same colloid mixture as in Example 1 and drying it at room temperature. The surface area and current density ratio of the prepared nanocomposites were measured and are shown in Table 1.

(Comparative Example 2)

The graphene-platinum nanocomposite was prepared under the same conditions as in Example 1, except that only the H ₂ PtCl ₆ 6H ₂ O was used as the metal precursor solution in the colloid mixture of Example 1. The surface area and the current density of the prepared nanocomposite were measured and reported in Table 1.

(Comparative Example 3)

The composition of the colloid mixture was the same as that of Comparative Example 2, and dried at room temperature as in Comparative Example 1 to prepare a film-like two-dimensional graphene-platinum nanocomposite. The surface area and current density ratio of the prepared nanocomposites were measured and are shown in Table 1.

[Table 1]

[Table 2]

2 showing the XRD pattern of the graphene-platinum-gold nanocomposite, peaks ((111), (200), (220)) of platinum-gold alloy nanoparticles in a and b were 38.94 °, 45.34 ° and 66.21 °, respectively. In particular, it can be seen that the position of 38.94 °, which is the position of the (111) peak, is the peak position (39.76 °) of general platinum and the peak position (38.18 °) of gold.

FIG. 2 (b) shows an XRD pattern of a three-dimensional graphene-platinum-gold nanocomposite according to a mixing ratio of platinum-gold. When gold content is higher than platinum, a relatively narrow pattern Thick. This is because the crystallinity of the entire nanocomposite increases as the content of gold in the graphene-platinum-gold nanocomposite increases.

FIG. 2C shows an XRD pattern of a graphene-platinum-gold nanocomposite having a two-dimensional structure according to a mixing ratio of platinum to gold. FIG. 2C shows a pattern similar to that of FIG. Dimensional structure, except that the mixing ratio is 1: 3 (1/3). This is because thermodynamically mixed particles of platinum and gold are different depending on the mixing ratio. It was confirmed that the graphene-platinum-gold nanocomposite was effectively formed according to various platinum-gold mixing ratios through the manufacturing method according to the present invention.

FIG. 2d shows the chemical bonding energy of the three-dimensional structure of the graphene-platinum-gold nanocomposite according to the mixing ratio of platinum-gold. The binding energy is 70.78 eV (Pt 4f _7/2 ) and 74.11 eV (Pt 4f _5/2 ). &_{Lt; /} RTI > In contrast, the binding energy of the graphene-platinum nanocomposite of the comparative example was observed at 71.16 eV (Pt 4f _7/2 ) and 74.41 eV (Pt 4f _5/2 ), indicating that the nanocomposite of the example had lower binding It can be seen that it has energy. This is because the mutual electron transfer of the metal atoms contained in the nanocomposite causes electron delocalization and partial ionization of each metal atom, resulting in additional binding energy reduction effect, resulting in a more stable nano- Complex < / RTI > is formed.

As shown in Tables 1 and 2, the nanocomposite of the examples had much higher surface area than the comparative example, and the surface area of the nanocomposite was at least 8 times higher than the other comparative examples in terms of electrochemical surface area. This is because the platinum-gold alloy nanoparticles are mixed in the nanocomposite to form a large amount of activation region limited to the nanometer level, and these regions make a great contribution to the increase of the catalytic activity. It also means that this structure provides more interaction opportunities between the nanocomposite and the electrode surface.

Table 2 shows the surface area according to the metal content when the content of graphene oxide is 0.5 wt%. It can be seen that the content of platinum is proportional to the electrochemical surface area. As shown in FIG. 2, as the content of gold in the graphene-platinum-gold nanocomposite increases, the crystallinity of the entire nanocomposite increases and the exposed area of the nanocomposite decreases relatively.

(Example 2)

In order to measure the electrochemical surface area (ECSA) according to the cyclic voltammogram, the above-mentioned electrode and electrolytic solution were prepared. The nanocomposite used for the working electrode was prepared from the graphene of Example 1 - platinum - gold nanocomposites were used. A cyclic voltage-current curve according to voltage and current density is shown in Fig.

(Comparative Examples 4 to 7)

(Bare GCE, Comparative Example 4), a graphene of a three-dimensional structure (3D-GR, Comparative Example 5), and a common platinum (Co) electrode were used as the nanocomposite used for the working electrode. Platinum nanostructure (3D-GR / Pt, Comparative Example 7) of a three-dimensional structure was prepared, and the graphene-platinum nanostructure of Comparative Example 7 Was prepared under the same conditions as the nanostructure of Comparative Example 2. A cyclic voltage-current curve according to voltage and current density is shown in Fig.

As shown in FIG. 3, the nanocomposite according to the embodiment has a wider electrochemical surface area. As the platinum-gold alloy nanoparticles are mixed in the nanocomposite as described above, a large amount of activation region limited to the nanometer level is formed, It can be confirmed that these regions make a large contribution to the increase of catalytic activity.

4 shows the cyclic voltammetric curve (a) according to the graphene oxide content when the platinum-gold mixing ratio is 3.0 and the cyclic voltammetric curve (b) according to the platinum-gold mixing ratio when the graphene oxide content is 0.5 wt% ). As shown in FIG. 4 (a), it can be seen that the voltage and current density increase as the graphene content decreases. In contrast, it can be seen that Comparative Example 6 using ordinary platinum-carbon black or Comparative Example 7 using a three-dimensional graphene-platinum structure recorded extremely low voltage and current density as compared with the embodiment.

Referring to FIG. 4 (b), when the content ratio of platinum and gold was 1 or 0.33 (1/3), the voltage and current density were almost the same as those of the comparative example. When the content ratio of platinum and gold was 3, And it was confirmed that it showed electrochemical properties. It is believed that they are mixed in the three-dimensional graphene nanostructure to induce a change in the interface adsorption force, resulting in a change in the electrical band structure. However, as the content of platinum decreases, the electrochemical properties of the catalyst decrease. This is because the catalytic activity of platinum is reduced in the methanol oxidation reaction.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (6)

a) preparing a graphene oxide colloidal solution;
b) preparing a platinum-gold nanocomposite colloidal solution;
c) mixing the colloidal solution of steps a) and b) to prepare a mixed colloidal solution;
d) aerosol droplet spraying said mixed colloid solution; And
e) pyrolyzing the atomized droplets by transferring them to a heating furnace to obtain a graphene-platinum-gold nanocomposite,
Wherein the colloidal liquid in step b) comprises a platinum precursor and a gold precursor, and the content of the platinum precursor is equal to or greater than the content of the gold precursor. The method according to claim 1,
The colloid liquid of step b)
(Na ₂ PtCl ₄ ), potassium tetrachloroplatinate (K ₂ PtCl ₄ ), platinum chloride (PtCl ₂ ), chloroplatinic acid (H ₂ PtCl ₆ ), tetrachloroplatinic acid (H ₂ PtCl ₄ ) and (Pt (NH ₃ ) 4 Cl ₂ ), and at least one of the platinum precursor,
(HAuCl ₄ ), gold trichloride (AuCl ₃ ), potassium tetrachloride (KAuCl ₄ ), gold hydroxide (Au (OH) ₃ ), gold oxide (Au ₂ O ₃ ), gold (AuBr ₃ ) (Au ₂ S ₃ ), and / or one or more
Tetrakis (hydroxymethyl) phosphonium chloride, sodium borohydride (NaBH _4), formaldehyde (HCHO), sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO _3), methanol (CH ₃ OH), Citric acid (C ₆ H ₈ O ₇ ) and sodium citrate (Na ₃ C ₆ H ₅ O ₇ ). The method for producing the graphene-platinum-gold nanocomposite according to claim 1, The method according to claim 1,
The colloidal solution of step b) has a W _pt / W _au (platinum precursor / gold precursor content ratio) of 1.0 to 3.0,
Wherein the mixed colloidal liquid comprises 0.1 to 1% by weight of the graphene oxide colloidal solution and 0.01 to 0.1% by weight of the platinum-gold nanocomposite colloidal solution, 0.001 to 1% by weight of the reducing agent and the balance of the solvent. A method for producing a fin-platinum-gold nanocomposite. The method according to claim 1,
Wherein the temperature of the heating furnace is 150 to 400 ° C. A process for the preparation of a compound according to any one of claims 1 to 4,
A crumpled paper ball is in the form,
Platinum-gold three-dimensional nanocomposite in which platinum-gold nanoparticles are supported inside the composite. A direct methanol fuel cell comprising the nanocomposite of claim 5.

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