KR101105473B1 - A carbon-based nano composite of novel structure and the method of preparing the same - Google Patents

Abstract

Board; A graphene sheet formed on a top surface of the substrate in a direction parallel to the substrate; And a carbon-based nanocomposite including a carbon-based nanomaterial having an aspect ratio of 2 to 75,000 formed on the other surface of the graphene sheet to form a predetermined angle with graphene. The carbon-based nanocomposite according to the present invention has excellent adhesion with the substrate and can be attached to the substrate without undergoing a paste process, and graphene and carbon nanotubes generate electric current in two directions, thereby greatly reducing electrical resistance. . In addition, it is possible to form a high current density in the carbon nanotubes through graphene, and to accelerate the oxidation-reduction reaction by allowing the carbon nanotubes to have a high specific surface area, and the graphene sheet has excellent heat dissipation characteristics. By transferring the generated heat to the outside quickly, it is possible to prevent degradation of carbon nanotubes. Therefore, when used as a battery electrode or a field emission display device, it is possible to obtain the effect of higher current density and lifespan than in the prior art.

Description

A carbon-based nano composite of novel structure and the method of preparing the same

The present invention relates to a carbon-based nanocomposite having a novel structure, a method for manufacturing the same, an electrode of a battery using a carbon-based nanocomposite, and a field emission display device, and more particularly, to improve adhesion to a substrate and reduce electrical resistance. The present invention relates to a carbon-based nanocomposite having a novel structure capable of extending the life of a device, a method of manufacturing the same, an electrode of a battery using the carbon-based nanocomposite, and a field emission display device.

In general, carbon nanotubes are widely used in various fields using carbon-based nanomaterials. Carbon nanotubes are extremely small cylindrical materials, usually very small in diameter of several nm. In carbon nanotubes, one carbon atom is bonded to three other carbon atoms and forms a hexagonal honeycomb pattern. Carbon nanotubes are materials capable of exhibiting metallic conductivity or semiconductor conductivity according to their structure, and are expected to be widely applied to various technical fields.

This is because carbon nanotubes have high electrical conductivity, mechanical strength, fast redox reaction, excellent electron emission effect, and high cost economy compared to other conventional materials.

For the growth of carbon-based nanomaterials represented by carbon nanotubes, arc discharge, laser vapor deposition, chemical vapor deposition, and plasma enhanced chemical vapor deposition Forming using various methods, such as has been reported.

In the electric discharge method, carbon nanotubes are generated on the anode side and the surface of the chamber by inducing electric discharge after arranging graphite rods having different diameters at a certain distance in the vacuum chamber. However, this method is difficult to mass-produce and there is a lot of impurities such as amorphous carbon or metal powder requires a separate purification process, it is not easy to control the thickness and length of carbon nanotubes.

The laser vapor deposition method irradiates a laser to a graphite rod and vaporizes it, and produces | generates a carbon nanotube. In this case, too, the mass production is unreasonable as in the previous electric discharge method.

Chemical vapor deposition is a method of producing carbon nanotubes by flowing a gas used as a precursor of carbon components in a high-temperature furnace, which is advantageous for mass production, but it requires a high temperature of 600 ~ 1000 ℃ with a catalyst. It requires a lot of effort, and it is difficult to use a substrate such as glass or plastic due to the high temperature process conditions, which limits the selection of the substrate.

In the plasma deposition method, after forming a catalyst metal film on a substrate, the catalyst metal film is etched using plasma generated from an etching gas to form a plurality of catalyst fine particles. A method of synthesizing carbon nanotubes on catalyst particles while supplying a carbon source gas on the substrate on which a plurality of catalyst particles are formed.

BACKGROUND ART Field emission display devices used in conventional displays and radiomedical applications are formed by using carbon nanotubes (CNTs), which are expected to have high current density per unit area, using catalytic metals on a semiconductor substrate to obtain high field emission characteristics. Attempted application to the device.

In order to use the grown carbon-based nanomaterials, they must be bonded or deposited on the substrate of the device. Such bonding is a method of growing directly on a substrate using growth equipment such as chemical vapor deposition and a method of separating a material grown from a directly grown substrate and bonding it to another substrate. The bonding force between the carbon-based nanomaterials (graphene, carbon nanotubes, carbon nanofibers, etc.) and the substrate is based on Van der Waals forces that are proportional to the contact area. Conventional carbon nanotubes and carbon nanofibers have a diameter of several hundred nanometers in diameter, so that the bonding strength with the substrate is very weak, so that the driving time is short and easily deteriorated when the device is applied.

In order to overcome such a problem, a process of removing the grown material from the growth substrate and forming a slurry into a device substrate may be used. At this time, the binder material is added together to improve adhesion to the substrate. The resulting slurry is bonded to the substrate, dried and calcined to form a thin film on the substrate. However, the thin film manufactured by the bonding process is very poor in electrical characteristics such as electrical conductivity, compared to the case where it is directly grown due to the after-burning charcoal derived from the non-conductive binder material.

In the case of using carbon nanotubes, in addition to the binder problem, a sharp decrease in electrical characteristics occurs due to a random horizontal arrangement during slurry production. Due to these shortcomings, there is a serious problem that the characteristics such as the ideal efficiency, brightness, etc. obtained as a result of the theoretical calculation are not expressed, and thus the application of carbon nanotubes is not activated. In addition, carbon-based nanomaterials have problems such as adhesion to a substrate and shortening device life due to heat during device driving.

SUMMARY OF THE INVENTION An object of the present invention is to provide a carbon-based nanocomposite having a novel two-dimensional planar structure in order to solve the problem of adhesion in the direct growth method, the binder problem in the bonding process, the limitation of the application of carbon nanotubes. It is.

Another object of the present invention is to provide a novel carbon-based nanocomposite having a two-dimensional planar structure in order to solve the problem of adhesion in the direct growth method, the binder problem in the bonding process, the limitation of the application of carbon nanotubes It is to provide a manufacturing method.

Still another object of the present invention is to provide an electrode of a battery employing a carbon-based nanocomposite having a novel structure in order to solve the problem of increasing resistance and deteriorating electrical characteristics.

It is still another object of the present invention to provide a field emission display device employing a carbon-based nanocomposite having a novel structure in order to solve problems such as adhesion to a substrate and shortening device life due to heat during device driving.

In order to achieve the above object, the present invention

Board;

A graphene sheet formed on a top surface of the substrate in a direction parallel to the substrate; And

Another aspect of the graphene sheet provides a carbon-based nanocomposite including a carbon-based nanomaterial having an aspect ratio of 2 to 75,000 formed to form a predetermined angle with the graphene sheet.

In order to achieve the above another object, the present invention

Forming a substrate;

Forming a graphene sheet on one surface of the substrate in a direction parallel to the substrate; And

Providing a method for producing a carbon-based nanocomposite comprising growing a carbon-based nanomaterial having an aspect ratio of 2 to 75,000 formed on the other side of the graphene sheet to form a predetermined angle with the graphene sheet. do.

In order to achieve the above another object, the present invention

It provides an electrode of a battery prepared using the carbon-based nanocomposite.

In order to achieve the above another object, the present invention

Provided is a field emission display device manufactured using the carbon-based nanocomposite.

The carbon-based nanocomposite according to the present invention has excellent adhesion with the substrate and can be attached to the substrate without undergoing a paste process, and graphene and carbon nanotubes generate electric current in two directions, thereby greatly reducing electrical resistance. . In addition, it is possible to form a high current density in the carbon nanotubes through graphene, and to accelerate the oxidation-reduction reaction by allowing the carbon nanotubes to have a high specific surface area, and the graphene sheet has excellent heat dissipation characteristics. By transferring the generated heat to the outside quickly, it is possible to prevent degradation of carbon nanotubes. Therefore, when used as a battery electrode or a field emission display device, it is possible to obtain the effect of higher current density and lifespan than in the prior art.

1A and 1B illustrate one embodiment of a carbon-based nanocomposite structure according to the present invention.
2 shows Raman spectra of graphene samples prepared according to one embodiment of the invention.
FIG. 3 shows the result of fitting the G band spectrum of the Raman spectrum according to FIG. 2.
FIG. 4 shows a chart comparing the number of graphene layers and the result of fitting the 2D band spectrum of the Raman spectrum according to FIG. 2.
Figure 5 shows the AFM picture and thickness of the graphene formed in accordance with an embodiment of the present invention.
6 shows a TEM photograph of a carbon-based nanocomposite formed according to an embodiment of the present invention.
Figure 7 shows a SEM picture of the carbon-based nanomaterial formed in accordance with an embodiment of the present invention.
FIG. 8 shows Nyquist data values for determining the electrochemical reaction of the counter electrode of a dye-sensitized solar cell (DSSC).
9 shows a bode phase graph according to the shape of an electrode according to an embodiment of the present invention.
FIG. 10 is a graph illustrating IV curves measured after fabrication of a counter electrode of a dye-sensitized solar cell (DSSC) according to an embodiment of the present invention.

The present invention relates to a substrate; A graphene sheet formed on a top surface of the substrate in a direction parallel to the substrate; And a carbon-based nanocomposite comprising a carbon-based nanocomposite including a carbon-based nanomaterial having an aspect ratio of 2 to 75,000 formed on the other side of the graphene sheet to form a predetermined angle with the graphene sheet. .

1A and 1B illustrate one embodiment of a carbon-based nanocomposite structure according to the present invention. According to the present invention, FIG. 1A shows that the graphene 2 is formed on the substrate 1 in a direction parallel to the substrate 1, and the carbon-based nanomaterial 3 is the substrate 1 and the graphene 2. And a predetermined angle θ, and the angle θ in FIG. 1A is less than 90 °, and the angle θ is 90 ° in FIG. 1B. Preferably, the angle θ represents 90 ° as shown in FIG. 1B.

Carbon-based nanomaterials had weak adhesion with the substrate when grown on the substrate. The carbon nanomaterial is bonded to the substrate by van der Waals force, which is proportional to the contact area. Therefore, carbon-based nanomaterials are only few nm to hundreds of nm in diameter, so they have to be weakly bound to the substrate. Accordingly, the present inventors have found a way to increase the contact area of the carbon-based nanomaterials with the substrate in order to further improve adhesion to the substrate.

According to the present invention, the adhesion with the substrate may be in charge of graphene, which is a two-dimensional planar structure, to increase the adhesion with the substrate. The improved adhesion to the substrate can be obtained in the manufacturing process because it can omit the conventional bonding process used to utilize the carbon-based nanomaterials.

The 'bonding' process refers to a process of preparing a carbon-based nanomaterial paste composition such as carbon nanotubes and carbon wires grown in order to fabricate a device using a carbon-based nanomaterial, applying the same to a substrate, and drying and firing the same. In this process, a binder is used to make a paste composition, and since the binder remains as xanthan even after firing, the binder acts as a resistance in the device, thereby rapidly deteriorating the electrical characteristics of the device.

In addition, during the process of applying the carbon-based nanomaterials by using the paste composition, the nanomaterials were unexpectedly arranged horizontally, thereby dramatically reducing the electrical characteristics. Therefore, carbon-based nanomaterials could not be used intact. However, the structure of the graphene and carbon-based nanomaterials according to the present invention may not use a binder, and solve the electrical resistance problem caused by xanthan coal. In addition, since there is no coating process using the paste composition, there is no reduction in electrical properties due to the arrangement of the carbon-based nanomaterials, and there is an advantage that the carbon-based nanomaterials can be used intact.

According to the present invention, there are two methods of forming graphene, a method of growing directly on a substrate, and a method of chemically synthesizing.

The direct growth method of graphene can be grown by using equipment such as Plasma CVD, Arc CVD, Thermal CVD, and it is possible to obtain graphene free of impurities (high purity) using catalytic metals. Although low, the number of graphene sheet layers can be controlled to some extent depending on the thickness of the catalyst layer. In an embodiment of the present invention, a method of growing graphene on a catalyst metal by using a thermal CVD apparatus is used, and a method of dissolving the catalyst metal by dissolving it in a solvent after the growth of the composite is used.

Chemical synthesis method of graphene was chemically treated in graphite ore by Hummer in 1958 to obtain graphene oxide (GO) aqueous solution, and to remove a large amount of stabilized graphene by removing oxide layer in aqueous solution. Fin aqueous solution can be obtained. This method can easily synthesize large amounts of graphene chemically and can be stored in a relatively stable state of acceptance.

It is preferable that the thickness of a graphene sheet is 2-100 nm. When the graphene sheet is less than 2 nm, it is not preferable because it is smaller than the minimum thickness (1.1 to 1.8 nm) of one layer of graphene, and when it exceeds 100 nm, it is not preferable because it exhibits bulk graphite characteristics.

The graphene sheet may be formed of not only a single layer but also 2 to 50 multiple layers in the form of a thin film. When the graphene sheet is more than 50, it is not preferable because the graphene layer is formed too thick as compared with the carbon nanotube layer. When the graphene sheet is analyzed by Raman spectroscopy, the monolayer shows 2D peaks in a form near 2700 cm ^-1 , and as the layer increases, the 2D peaks move to the right, and the shoulder on the left side of the strongly expressed peaks (shoulder) peaks appear so you can gauge the number of graphene layers.

According to the present invention, the graphene is formed, and then the carbon-based nanomaterial is grown to form a predetermined slope with the graphene. Growth of carbon-based nanomaterials can be divided into direct growth and chemical synthesis.

In the direct growth method, an appropriate catalyst metal for the growth of carbon-based nanomaterials is deposited or coated on the formed graphene thin film. Next, carbon-based nanomaterials are grown using chemical vapor deposition (CVD) or other growth equipment. As the catalytic metal, it is preferable to use at least one metal selected from the group consisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Rh, Si, Ti, W, U, Zr and their alloys. desirable. Preferably, Fe, Pt, Au and the like excellent in electrical conductivity may be used.

In chemical synthesis, graphene oxide or graphene thin film solvent is mixed with an appropriate catalyst metal for the growth of carbon-based nanomaterials, and then the formed mixture is coated on an appropriate concentration on a substrate, dried and then grown.

A carbon-based material may be generated by dip coating a Fe / Mo solution on the graphene-formed silicon wafer substrate. The Fe / Mo solution serves as a catalyst for producing carbonaceous material. The Fe / Mo solution may be mixed with graphene oxide before the graphene is formed and applied on top of the substrate, which may be, for example, a substrate carburized in carbon, preferably a SUS substrate. .

By forming a graphene oxide layer on the substrate by a chemical synthesis method different from that described above, the carbon-based nanomaterial may be formed by etching the catalytic metal film. In detail, a catalytic metal film is formed on the graphene oxide layer by a thickness of several nm to several hundred nm, preferably 2 nm to 10 nm, by thermal evaporation, electron beam evaporation, or sputtering. The metals available for the production of the catalytic metal film are the same as the metals according to the direct growth method. The catalyst metal film is then etched to form independently isolated nano-sized catalytic metal particles. Forming the separated nano-sized catalytic metal particles may be performed by using a gas etching method or plasma using an etching gas, which thermally decomposes an etching gas selected from the group consisting of ammonia gas, hydrogen gas and hydride gas. It is performed by etching.

In the present invention, the graphene thin film, which is a lower structure for maintaining adhesion to the substrate, has a two-dimensional planar structure. Accordingly, the movement of electrons in graphene is generated in the horizontal direction, and current flows in the horizontal direction. Carbon-based materials such as carbon nanotubes and carbon wires, which are upper structures, move in a direction in which electrons form a predetermined angle with the graphene sheet to generate current flow in a direction different from that of the graphene sheet. This is because when the current is applied to the graphene thin film in an external circuit, electrons move directly to the same carbon-based nanomaterial without loss of resistance between interfaces, so that there is no resistance loss due to material differences between interfaces. In addition, carbon nanotubes and carbon wires having a predetermined slope with graphene provide a wider specific surface area than those using a bonding process, thereby providing excellent electrical properties in various fields.

In the present invention, the carbon-based nanomaterial refers to a nanomaterial having a linear shape having an aspect ratio of 2 to 75,000. When the aspect ratio is shorter than 2, it is not preferable because the efficiency is reduced as a field emission source as it has a low aspect ratio, and if it is longer than 100,000, it is not preferable because there is a disadvantage that the thickness of the emitting device is thick.

Carbon-based nanomaterials are formed to form a predetermined angle with the graphene sheet. Here, the term 'predetermined angle θ' means to form a constant angle θ that is not parallel to the graphene sheet, and the angle may be applicable when the angle exceeds 0 °. For example 5 to 90 °, preferably 30 to 90 °, more preferably 60 to 90 °, most preferably 90 ° to be formed perpendicular to the graphene sheet.

Carbon-based nanomaterials of the present invention is a material of 1 to 150 ㎛ in length, 2 to 500 nm in diameter may be a hollow tube form, or may be a hollow fiber form. If the diameter is 2 nm or less, it is not preferable because it is difficult to grow to a uniform diameter and the electrode characteristics are inferior, and if it is 500 nm or more, it is not preferable because the efficiency is lowered as it has a relatively low aspect ratio.

Examples of carbon-based nanomaterials include, but are not limited to, carbon nanotubes, carbon nanowires, or carbon nanofibers. In the case of carbon nanotubes, the diameter is preferably 2 to 100 nm. The carbon nanotubes may be single-walled, double-walled, or multi-walled carbon nanotubes. It may be formed of these bundles. When the bundle is formed, it has the advantage of having a high current density during field emission by showing a high density in a narrow area.

When using a coating, drying, and firing process using a conventional paste composition, the transparent conductive substrate has a problem in that it does not endure high temperature growth. Can be used selectively depending on the range. In particular, plastic, as well as glass, Si, and SUS substrates can be used, and may be useful for flexibility when used in future displays. A substrate imparting conductivity to form an ITO thin film on an insulating substrate such as glass may also be used.

In addition, according to one embodiment of the present invention, it includes a case in which carbon is added to the substrate in order to improve the adhesion of the substrate. The carbon content in the substrate can be increased by injecting (carburizing) carbon into the substrate. The injected carbon forms a carbon layer between the substrate and the graphene so that the carbon layer and the graphene may form a covalent bond. Although many kinds of substrates can be used here, it is preferable to use SUS.

Explaining the carbon input method using SUS, for example, after coating a graphene sheet or graphene oxide on the carbon carburized SUS substrate, growth of carbon-based nanomaterials including multi-walled carbon nanotubes or carbon nanowires is observed. In order to heat the SUS substrate. Due to the heating of the substrate, the bonding force of the carbon bonder and the graphene bond group on the surface of the SUS substrate is increased due to the heat energy.

According to another aspect of the invention, forming a substrate; Forming a graphene sheet on one surface of the substrate in a direction parallel to the substrate; And growing a carbon-based nanomaterial having an aspect ratio of 2 to 75,000 so as to form a predetermined inclination with the graphene sheet on the other side of the graphene sheet. do.

According to another aspect of the present invention, there is provided an electrode of a battery produced using a carbon-based nanocomposite. The battery may be used as an electrode of various types of cells, such as solar cells, fuel cells, and secondary cells. The carbon-based nanocomposite of the novel structure according to the present invention generates two current flows in a horizontal direction and a direction formed at a predetermined angle with the horizontal direction, so that electrical resistance between the substrate, carbon nanotubes, and carbon wires is increased. The energy conversion efficiency of the battery can be improved because the material is greatly reduced compared to the electrode or device of the battery.

The solar cell may be used in cells such as silicon solar cells, dye-sensitized solar cells, CIGS solar cells, and the like. By using the carbon-based nanocomposite according to the present invention as the electrode of the solar cell can provide a solar cell having an excellent energy conversion efficiency compared to the prior art.

Fuel cells can be classified into alkali type, phosphate type, molten carbonate type, solid oxide type and solid polymer electrolyte type according to the type of electrolyte used, where fuel cells requiring platinum catalyst are alkali type or phosphate type. It is a solid polymer electrolyte fuel cell. Electrodes employing the carbon-based nanocomposites according to the present invention can be used in alkaline fuel cells, phosphoric acid fuel cells and solid polymer electrolyte fuel cells. In addition, since the structure of the direct methanol fuel cell is the same as that of the solid polymer electrolyte fuel cell, it can be used in this case.

According to still another aspect of the present invention, there is provided a field emission display device manufactured using a carbon-based nanocomposite. Field emission displays (FEDs) using conventional carbon nanotubes (CNTs) as electron emission sources are known. However, even in the case of the field emission display device, when carbon nanotubes are applied using a paste process and subjected to a sintering and activation process, the effect of the field emission is lower than expected, but the carbon-based nanocomposite of the present invention By introducing the structure, the effect of the field emission can be improved.

The carbon-based nanocomposite of the present invention is different from the conventional carbon-based nanomaterials in which electron transfer and field emission occur simultaneously, and the external structure of electron transfer and heat is responsible for the horizontal structure, and the field emission role has a horizontal structure and a predetermined slope. Will be in charge. This characteristic allows graphene to quickly transfer heat generated during device operation to the outside, preventing device life due to deterioration.

Hereinafter, the present invention will be described in more detail with reference to Examples. Embodiments herein are for the purpose of describing the invention only and are not intended to limit the scope thereof.

Example

Graphene  Manufacture of sheets

Example  One

The silicon wafer was organic cleaned and the Fe catalyst was deposited to a thickness of 100 nm using RF and ion sputter. Subsequently, Ar gas was heated to 500 sccm for 30 minutes at a temperature of 900 ° C. under a pressure of 60 torr. After maintaining at 900 ° C. for 5 minutes, methane gas was 25 sccm, carbon nanotubes were grown for 10 minutes, hydrogen gas was 500 sccm, and then cooled for 50 minutes to grow a layer of graphene on a silicon wafer.

Example  2

The vial was placed on a hot plate, and 6 ml of H ₂ SO ₄ was added thereto, followed by heating to 80 ° C. Measure K ₂ S ₂ O ₈ and P ₂ O ₅ with a 2g electronic balance and slowly add 4g of graphite powder. It was confirmed whether the color of the reaction product was dark blue. After the reaction, the mixture was cooled at room temperature (25 ° C.) for 6 hours, and after 6 hours, the graphite powder was filtered through filter paper. Deionized water was continuously poured over the filtered graphite powder to be washed and continued until pH 7.

After filtration and washing, the graphite powder was dried at room temperature (25 ° C.) overnight to prepare graphite oxide. A mechanical stirrer was placed and a teflon beaker, ice and salted ice box were placed on it. Concentrated H ₂ SO ₄ (92 ml) and graphite oxide (GO) were added to a Teflon beaker.

12 g of KMnO ₄ was added little by little while maintaining the temperature inside the Teflon beaker not exceeding 20 ° C. KMnO ₄ was added and the reaction was allowed to stir at 35 ° C. for 2 hours when entering the stable step. After 2 hours, 185 ml of deionized water was added slowly. After 15 minutes, 560 ml of deionized water and 10 ml of 30% H ₂ O ₂ were added. The graphite oxide was filtered and 1 liter of a solution having a ratio of deionized water and HCl of 10: 1 was poured slowly to remove the metal ions attached to the graphite oxide. Graphite oxide remaining on the filter paper was added to deionized water (800 ml). Graphite oxide was filtered through a dialysis membrane and 0.5% w / v of graphite oxide was obtained. Sonication for 30 minutes (500w 30%) and by rotating for 30 minutes at 3,000 rpm in a centrifuge to remove the unexfoliated graphite oxide to obtain a layer of graphene oxide sheet.

Example  3

Except for obtaining graphene by dip coating the substrate in a graphite oxide solution to remove the oxide groups in the graphite oxide, heating to a temperature of 300 ° C. for 5 hours in a heating furnace, and reducing oxygen by annealing. It carried out similarly to Example 2.

Example  4

5 ml of graphene solution, 5 ml of deionized water, 5 µl of hydrazine (35 wt%) and 35 µl of ammonia (28 wt%) were placed in a vial, vigorously stirred for several minutes, and left for 1 hour in 95 ° C water. Except for completing the wt% of the graphene (Chemical Conversion Graphene) was carried out in the same manner as in Example 2. The substrate was dip-coated with the prepared graphene solution to coat a few layers of graphene on the substrate.

Preparation of Carbon Nanocomposites

Example  5

Fe 6 nm was deposited on the graphene-formed silicon wafer substrates prepared in Examples 1, 3, and 4 using ion sputtering. The Ar / NH ₃ gas was then 1000/140 sccm each in CVD and heated for 30 minutes at a temperature of 900 ° C. under 60 torr pressure. The pressure was raised to 700 torr and maintained at 900 ° C. under Ar / NH ₃ atmosphere (1000/140 sccm) for 5 minutes, C ₂ H ₂ at 20 sccm, carbon nanotubes were grown for 10 minutes, and argon gas at 1000 sccm. After cooling for 50 minutes to complete the carbon-based nanocomposite.

Comparative example  One

The silicon wafer was organic cleaned and the Fe catalyst was deposited to a thickness of 100 nm using RF and ion sputter. Subsequently, Ar gas was heated to 500 sccm for 30 minutes at a temperature of 900 ° C. under a pressure of 60 torr. After maintaining at 900 ° C. for 5 minutes, methane gas was 25 sccm, carbon nanotubes were grown for 10 minutes, hydrogen gas was 500 sccm, and then cooled for 50 minutes to grow a layer of graphene on a silicon wafer.

Comparative example  2

Multi-walled carbon nanotubes (MWNTs) were grown on Si substrates by thermal chemical vapor deposition (thermal CVD), and the grown MWNTs were scraped from the substrate using a knife.

CMC (carboxyl methyl cellulose): D.I. A binder was prepared by mixing water at a ratio of 1: 500, and MWNTs paste was prepared by first mixing MWNTs prepared in a binder, followed by ultrasonic treatment for about 1 hour.

MWNTs paste was coated on the FTO substrate by a doctor blade method to produce MWNTs electrodes, and the MWNTs electrodes formed at this time were patterned to have an area of about 0.3 cm ² using 3M tapes. The 3M tape was removed and dried at room temperature for about 5 hours.

Carbon Nanocomposites  Evaluation and Results

Figure 2 shows the results of measuring the Raman spectrum of the graphene sample synthesized in Example 2 in the 1200 cm ^-1 ~ 3000 cm ^-1 region. In this case it was used for an argon ion laser (Ar ion laser) of 514.4 nm. Typical graphite Raman spectra (514.5 nm) are divided into G-bands around 1580 (± 20) cm ⁻¹ and D-bands showing defect or disorder characteristics around 1350 (± 10) cm ⁻¹ . In particular, graphene exhibits 2D-band near 2700 (± 5) cm ⁻¹ , which is twice the D-band due to double resonance. This band plays an important role in analyzing a graphene sample with multiple layers because it is represented by interference between layers of graphene.

FIG. 3 shows the result of fitting the G band spectrum of the Raman spectrum according to FIG. 2. The Raman characteristic of graphite system tends to move toward the higher wavelength (left direction) near 1580 cm ^{-1 as it} is closer to natural graphite, and to the lower direction (right direction) near 2700 cm ^-1 . . On the other hand, closer to graphene tends to move toward the lower wavelength (right direction) in the vicinity of 1580 cm ⁻¹ , and tends to move toward the higher wavelength (left direction) in the vicinity of 2700 cm ⁻¹ .

FIG. 4 shows a result (a) of fitting the 2D band spectrum of the Raman spectrum according to FIG. 2 and a diagram (b) comparing the number of its pinned layers. It is also known that the thickness of the graphene layer can be determined from the relative sizes of the G-band and the 2D-band [AC Ferrari, PRL 97, 187401 (2006)]. In the present embodiment, since the relative ratio of the G-band and the 2D band in the peak portion of FIG. 2 is larger than the valley, it may be determined that the graphene layer is formed thick. Raffin spectroscopy shows little D-band around 1350 cm ^-1 , and it can be determined whether graphene is present.

Generally, 2D peaks appear in the vicinity of 2700 cm ⁻¹ , and when graphene is a monolayer, the peaks appear strongly in one form. As the number of layers of graphene increases, the 2D peak shifts to the right side, and a shoulder peak appears on the left side of the strongly expressed peak, thereby measuring the number of graphene layers.

In the Raman spectrum, two peaks of 2668 cm ⁻¹ and 2702 cm ⁻¹ appear to overlap. It can be seen that the half width (FWHM: 68) and the peak intensity of the peak appearing at 2702 cm ⁻¹ are twice as large as those of the peak appearing at 2668 cm ⁻¹ , respectively. Referring to Figure 4 (b), the synthesized graphene showed a shoulder peak similar to the Raman peak of the 2 to 5 layers. However, if the peak of the 2D-band appeared without a peak shift around 2700 cm ^-1 , it can be seen that the graphene sheet composed of about 2 to 4 layers were synthesized.

Figure 5 shows the AFM picture and thickness of the graphene formed in accordance with an embodiment of the present invention. Referring to FIG. 5, the thickness of the graphene may be measured by measuring the stepped portion of the graphene. The graph on the right shows the graphene thickness measured at two locations. It can be seen that it is measured from about 2nm to 6nm.

6 shows a TEM photograph of a carbon-based nanocomposite formed according to an embodiment of the present invention. Referring to FIG. 6, it can be seen that graphene is formed on a SiO ₂ substrate and multi-walled carbon nanotubes are formed on the graphene according to Example 2 of the present invention.

Figure 7 shows a TEM picture of the MWCNT carbon-based nanomaterial formed in accordance with an embodiment of the present invention. Referring to Figure 7, it can be seen that the MWCNT is densely formed.

Dye-Sensitized Solar Cells DSSC Manufacturing

In order to manufacture a transparent dye-sensitized solar cell, a paste including carbon nanocomposites of Example 5 and Comparative Examples 1 and 2 was prepared. On the FTO glass substrate cut to the size of 15 mm x 10 mm by the same method as the titanium oxide layer, the paste including Example 5, Comparative Example 1 and Comparative Example 2 was heated and applied at room temperature to 400 ℃ to prepare an electrode. This coating was prepared with the electrode substrate and the dye-sensitized to the carbon nano-composite electrode substrate element junction solar cells (purchased from Swiss captured solar ^{Optronics) (N719 - - / I3 I} ) dye is adsorbed on the titanium oxide electrolyte.

DSSC of Polarization resistance  evaluation

FIG. 8 shows Nyquist data values measured in half cells to examine the electrochemical reaction of counter electrodes of a dye-sensitized solar cell (DSSC). 9, the same electrolyte I ^- / I3 ^-: value of Rs represents electrolyte resistance because it used a (N719 purchased from Swiss captured solar Optronics) and Cell area shows that the same represents a 6.8 to 7.0 Ω. At the same time, the magnitude of the polarization resistance (Rp) indicating the resistance between the counter electrode and the electrolyte was shown in the order of Example 5 <Comparative Example 2 <Comparative Example 1, and the lowest polarization resistance of Example 5 was obtained. The value was found to be very low, such as 2.5 Ω. Therefore, the electrochemical reaction was confirmed to occur most actively in Example 5.

In the case of Comparative Example 1 (Graphene), it can be interpreted that such a value is shown by not having a structure having a large surface area as in Example 5 of the present invention and not having a sufficient reaction area. It is known that the electrical conductivity of graphene is superior to that of multi-walled carbon nanotubes, but the charge transfer properties are more influenced by the structural aspects than the material properties.

In addition, multi-walled carbon nanotubes have much lower electrical characteristics such as electrical conductivity than when grown directly on xanthan after firing due to a binder material, which is a nonconductor, when pasting onto a substrate surface. In most cases, the rapid decrease of the electrochemical properties due to the non-predictive horizontal arrangement is caused. As a result, due to the structural characteristics of the carbon nanocomposite, which does not use a binder and maintains the vertical arrangement, the reaction area is wide and the electrical resistance is reduced.

DSSC Of frequency bands

9 shows a Bode phase graph according to the shape of the electrode. Referring to FIG. 9, it can be seen that the main reaction frequency band of Comparative Example 1 (Graphene) is in the range of 1000 Hz, and the speed of the reaction is as slow as that. In the case of Comparative Example 2 (MWCNT), the reaction band range is about 1000 Hz to 20000 Hz, but in Example 5, the peak range is 500 Hz to 50000 Hz, which indicates that the reaction starts at a faster frequency band. Able to know. Eventually, it can be seen that the electrochemical reaction occurs faster in GMWNTs.

Carbon nanotubes are known to be more active at the ends than at the sides. Therefore, due to the structural feature of the present invention in which the inclined angle array is maintained than in the case of multi-walled carbon nanotubes having an unpredictable horizontal arrangement, the ends of the carbon nanotubes that contribute to the electrochemical reaction are mostly exposed to the electrolyte. Because of this, it can show better frequency characteristics.

DSSC Evaluation of efficiency

Figure 10 Example 5 and Comparative Examples 1 and 2 the same electrolyte I ^- / I3 ^- was produced (N719) and the counter electrode (counter electrode) of the dye-sensitized solar cell (DSSC) using a Cell Area 1 sun , IV curve graph measured under AM 1.5 conditions. Jsc, Voc, Fill factor, Energy conversion efficiency were measured and shown in Table 1.

Jsc (mA / cm2) Voc (V) Fill factor 侶 (%) Example 5 5.6 0.76 0.70 3.0 Comparative Example 1 5.6 0.71 0.37 1.5 Comparative Example 2 5.5 0.74 0.65 2.6

Referring to Table 1, it can be confirmed that the trend of efficiency (Graphene <MWNTs <GMWNTs) consistent with the results of the cell chemistry reaction (Nyquist, Bode phase plot) shown in FIG. In particular, the fill factor, which represents the efficiency of dye-sensitized solar cells, is most affected by the total reflection conditions of light and the material of each part, but the electrochemical reaction in DSSC has the greatest effect. The fill factor value of 0.7 in GMWNTs cell shows the possibility of replacing platinum with the same fill factor value of 0.7 in DSSC, which has a 10.2% efficiency using platinum from Sharp.

Currently, the DSSC used for the measurement has a total thickness of light because the thickness of TiO ₂ is about 7 μm. However, if the thickness is 12 to 13 ㎛ that can cause the anti-reflective coating is expected to increase the amount of light incident on the dye by about 25% or more can be expected to increase the efficiency.

In addition, the TiO _{2 had} an area of 0.12 cm 2, while the FTO used as the substrate had an area of 3.6 cm 2, whereby Jsc was low due to substrate resistance at the time of measurement. In most papers TiO ₂ Given that the ratio of area / substrate area is 0.25 to 0.36, while the ratio of area used in the experiment is 0.03, if only two design factors are modified and measured, it is expected to increase the efficiency while maintaining the current excellent fill factor. do.

1 ... substrate 2 ... graphene
3.Carbon-based Nanomaterials

Claims (21)

Board;
A graphene sheet formed on a top surface of the substrate in a direction parallel to the substrate; And
A carbon-based nanocomposite comprising a carbon-based nanomaterial having an aspect ratio of 2 to 75,000 formed on the other surface of the graphene sheet to form an angle of 5 to 90 ° with a graphene formation direction. The carbon-based nanocomposite of claim 1, wherein the graphene sheet has a thickness of 2 to 100 nm. The carbon-based nanocomposite according to claim 1, wherein the graphene sheet is formed of 1 to 100 layers. delete The carbon-based nanocomposite of claim 1, wherein the carbon-based nanomaterial is at least one selected from carbon nanotubes, carbon nanowires, and carbon nanofibers. The carbon-based nanocomposite according to claim 5, wherein the carbon nanotubes are single-walled, double-walled, or multi-walled carbon nanotubes. The carbon-based nanocomposite of claim 5, wherein the carbon nanotubes have a diameter of 2 to 100 nm. The method of claim 1, wherein the carbon-based nanomaterial is one selected from the group consisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Rh, Si, Ti, W, U, and Zr A carbon-based nanocomposite formed from the above catalyst metal. The carbon-based nanocomposite of claim 1, wherein the substrate is glass, Si, SuS, or plastic. The carbon-based nanocomposite according to claim 1, wherein carbon is injected into the substrate. The carbon-based nanocomposite according to claim 10, wherein the carbon injected forms a carbon layer between the substrate and the graphene to form a covalent bond between the carbon layer and the graphene. Forming a substrate;
Forming a graphene sheet on one surface of the substrate in a direction parallel to the substrate; And
Producing a carbon-based nanocomposite comprising growing a carbon-based nanomaterial having an aspect ratio of 2 to 75,000 on the other side of the graphene sheet to form an angle of 5 to 90 ° with the graphene sheet Way. The method of claim 12, wherein the graphene sheet is a carbon-based nanocomposite manufacturing method characterized in that the deposition of the catalytic metal using a sputter and then directly grown by chemical vapor deposition. The method of claim 12, wherein the graphene sheet is a method of producing a carbon-based nanocomposite comprising the step of obtaining graphene oxide and removing oxygen through a heat treatment or a chemical treatment process. The method of claim 12, wherein the substrate further comprises the step of introducing carbon. 13. The method of claim 12, comprising mixing the graphene oxide or graphene sheet with Fe / Mo solvent and applying it onto a substrate. The method of claim 12, wherein the carbon-based nanomaterial is at least one selected from carbon nanotubes, carbon nanowires, and carbon nanofibers. The carbon-based nanomaterial of claim 12, wherein the carbon-based nanomaterial is formed by depositing a catalyst metal on a substrate on which a graphene sheet is formed or by impregnating the substrate in an aqueous solution of the catalyst metal, followed by chemical vapor deposition. Method for preparing a composite. An electrode of a battery prepared using the carbon-based nanocomposite according to any one of claims 1 to 11. Solar cell employing the electrode of the battery according to claim 19. A field emission display device manufactured using the carbon-based nanocomposite according to any one of claims 1 to 11.

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