TWI477639B - Preparation of carbon nanotubes and carbon nanotubes and their carbon nanotubes and their applications - Google Patents

Description

Method for preparing carbon nanotubes and carbon nanotubes and carbon nanotube electrodes thereof and application thereof

The invention relates to a method for preparing a carbon nanotube, in particular to a method for pretreating a catalyst by radio frequency hydrogen plasma, regulating the temperature of preparing a carbon nanotube, ammonia gas and a volume flow of hydrogen to prepare a vertical alignment, a high concentration and A method of low amorphous carbon carbon nanotubes. The invention also relates to a carbon nanotube. The invention further relates to a carbon nanotube electrode. The invention further relates to an electrochemical capacitor having the aforementioned carbon nanotube electrode. The invention further relates to a battery having the aforementioned carbon nanotube electrode.

Compared with batteries and capacitors, electrochemical capacitors are a type of charging and discharging device with high power density, long cycle life and high energy density. Therefore, they are often used in energy output devices, electric vehicle braking systems and acceleration tools. , the starting power of notebook computers and fuel cells, etc. According to the form of energy storage, electrochemical capacitors can be divided into two types, one is electric double layer capacitors (EDLC), and the other is pseudo-capacitors. The capacitance of the electric double-layer capacitor is the purpose of storing electric energy by the phenomenon of charge separation caused by Coulomb electrostatic force between the electrode and the electrolyte interface; the capacitance of the pseudo-capacitor mainly uses the electrode surface for rapid and continuous redox reaction. Store electrical energy.

Recent studies have shown that carbon nanotubes (CNTs) have a high accessible surface area (for example, nanometer size of carbon nanotubes, hollow structure, low proportion of microporous structure). Unique characteristics such as low resistance and high stability, so the carbon nanotubes are quite suitable As an electrode material for electrochemical capacitors.

In the current state of the art, in the process of growing carbon nanotubes by catalytic chemical vapor deposition (CCVD), iron (Fe) and cobalt are usually used as transition metals. (Co) and nickel (Ni) as catalysts, and a gas such as methane (CH ₄ ) and acetylene (C ₂ H ₂ ) is introduced as a carbon source required for growing a carbon nanotube; since the catalyst does not reach an appropriate temperature, The shortage of carbon source and the failure of the growth rate of carbon nanotubes have resulted in the formation of a pentagonal or heptacyclic carbon ring inside the carbon nanotubes, which makes the carbon nanotubes bend, low density and high amorphous. Carbon, which in turn causes a decrease in its specific capacitance, also affects its cycle life.

In view of the disadvantages of the prior art carbon nanotubes being curved, low-density and high-amorphous carbon, the object of the present invention is to provide a method for preparing a carbon nanotube by raising the vertical arrangement of the carbon nanotubes. Degree, intensity and average specific surface area reduce amorphous carbon, which in turn increases specific capacitance and lifetime.

To achieve the above object, the present invention provides a method of preparing a carbon nanotube comprising: providing a catalyst-titanium-coated substrate on a surface; radio frequency hydrogen-plasma After pretreating the substrate, a thermal chemical vapor deposition (TCVD) is applied to a heating temperature, and ammonia gas and hydrogen gas are introduced to form a vertical Arranged, high-density and low-amorphous carbon carbon nanotubes.

According to the invention, "catalyst" as used herein is any suitable growth A transition metal of a carbon nanotube; preferably, the catalyst is cobalt (Co).

Preferably, the substrate may be any material suitable for supporting a catalyst to grow a carbon nanotube structure, including, but not limited to, graphite and silicon.

In accordance with the present invention, "radio frequency hydrogen plasma" as used herein is used to promote the formation of nanoparticles of a catalyst and to reduce metal oxides on the surface of the catalyst; for example, the following reaction conditions are employed: placing the substrate in a reaction chamber [frequency 13.56 Megahertz (MHz), a radio frequency plasma with a maximum power of 100 watts (W), pumping the background pressure of the reaction chamber to 7x10 ^-6 torr, and the volumetric flow rate of hydrogen is 50 standard cubic centimeters per minute. (sccm, standard cubic centimeter per minute, cm ³ /min), plasma pressure control of 5 torr, plasma power of 50 W, substrate temperature of 500 ° C, and time of 8 minutes (min).

According to the present invention, "thermal chemical vapor deposition" as used herein means placing a catalyst/titanium-covered substrate in a reaction chamber, and introducing a carbon source gas such as acetylene (C ₂ H ₂ ) and argon (Ar). And generating a carbon nanotube by a chemical reaction; taking the following reaction conditions as an example: the substrate is heated in a high temperature furnace, and acetylene of 50 cm ³ /min and argon of 100 cm ³ /min are introduced. (Ar) and after 20 minutes.

Preferably, the heating temperature is between 700 ° C and 800 ° C.

Preferably, the volume flow rate of the ammonia gas is between 0 cm ³ /min and 60 cm ³ /min.

Preferably, the volume flow rate of the hydrogen gas is between 0 cm ³ /min and 21 cm ³ /min.

In accordance with the present invention, "vertical alignment" as used herein means that the substrate has a horizontal plane and the carbon nanotubes are grown substantially perpendicular to the horizontal plane of the substrate. The extension of the growth, based on the characteristics of the carbon source and the self-combination, the direction in which the formed carbon nanotubes extend may be slightly different. Preferably, the direction in which the axes of the respective carbon nanotubes extend is about the horizontal surface of the substrate. 85° to 95°; more preferably, about 88° to 93°; still more preferably about 89° to 91°.

According to the present invention, "highly dense" as used herein means that the specific surface area of the carbon nanotubes is between 2.36 x 10 ¹⁶ square nanometers per square centimeter (nm ² /cm ² ) to 2.67 × 10 ¹⁶ nm ² /cm. Between ² .

In accordance with the present invention, "low amorphous carbon" as used herein refers to a degree of graphitization (I _G /I _D value) of between 0.89 and 0.95.

The invention further provides a carbon nanotube comprising the method as described above, wherein the axial direction of the carbon nanotube extends perpendicularly to a horizontal surface of the substrate of about 85° to 95°; The specific surface area of the carbon nanotubes is between 2.36×10 ¹⁶ nm ² /cm ² and 2.67×10 ¹⁶ nm ² /cm ² ; the degree of graphitization of the carbon nanotubes (I _G /I _D value) is between Between 0.89 and 0.95.

The present invention further provides a carbon nanotube electrode comprising a carbon nanotube as described above.

The present invention further provides an electrochemical capacitor comprising the carbon nanotube electrode as described above.

The present invention further provides a battery comprising the carbon nanotube electrode as described above.

Compared with the prior art, the invention has the following advantages:

1. The present invention uses titanium as a barrier layer to prevent the formation of telluride, and the titanium barrier layer can increase the adhesion of the carbon nanotubes to the substrate.

2. The hydrogen plasma can be reduced by the pretreatment of the catalyst by hydrogen plasma in the present invention. The surface oxide of the catalyst keeps the activity of the catalyst, and the catalyst can form a nano-grain structure, which can promote the growth of the carbon nanotube electrode with a large density and an average specific surface area, and can also enhance its Specific capacitance value.

3. The invention can improve the activation energy of the catalyst and the decomposition rate of carbon atoms (acetylene) by regulating the temperature of the preparation of the carbon nanotubes, thereby increasing the specific capacitance value and the lifetime.

4. In the process of growing a carbon nanotube electrode by thermal chemical vapor deposition in the invention, the introduction of ammonia gas and hydrogen gas can inhibit the formation of amorphous carbon, and the introduction of ammonia gas and hydrogen gas can also help the growth to have vertical alignment. The carbon nanotube electrode makes the electrolyte ion easily penetrate into the potential electroactive site at the bottom of the carbon nanotube, which can increase the specific capacitance value and the lifetime, and the process is easy to enlarge and compare. With commercial production potential.

5. The invention directly grows the carbon nanotubes on the substrate, the process does not need to carry out the carbon nanotube extraction, does not need to use the solvent to dissolve the carbon nanotubes, and does not need to further deposit the carbon nanotubes on the base. The carbon nanotubes are adhered to the substrate by using an adhesive or an adhesive to increase the contact resistance between the current collector and the carbon nanotubes, thereby lowering the electrochemical characteristics.

The technical means used by the present invention to achieve the above objects will be further clarified by the following description of the technical contents of the present invention.

Materials and methods

Material

The purity of the titanium target is 99.995%, purchased from SCM, Inc., USA; the purity of the cobalt target is 99.9%, purchased from SCM, Inc., USA; acetylene The purity is 99.999%, purchased from Yizhan Gas Company; the purity of argon is 99.999%, purchased from Cold Research Gas Company; the purity of ammonia is 99.999%, purchased from Cold Research Gas Company; the purity of hydrogen 99.999%, purchased from Cold Research Gas Company; model of potentiostat is CHI 608B, purchased from CH Instrument Company of the United States; model of constant temperature circulating water tank is G10, purchased from DENG YNG Company; field emission scanning electron microscope (field-emission-scanning electron microscopy, FE-SEM) model JSM-6700F, purchased from Japan JEOL company; transmission electron microscopy (TEM) model JSM-2010, purchased from Japan JEOL The company; the microscopes Raman spectrometer is model inVia and is available from Renishaw, UK.

2. Method

(1) Electrochemical charge and discharge test analysis

A silver/silver chloride (Ag/AgCl) electrode is used as a reference electrode, and platinum (Pt) is used as a counter electrode and each sample is used as a working electrode to form a three-electrode cell. The potentiometer was tested by cyclic voltammetry. Before the test, the working electrode, the reference electrode and the corresponding electrode were placed in a solution, and the solution was degassed using nitrogen (N ₂ ). The solution was placed in a constant temperature circulating water bath and the temperature of the solution was maintained at 25 °C. The test was carried out in an aqueous solution of 0.5 molar (M) sulfuric acid (H ₂ SO ₄ ) at a scan rate of 100 millivolts per second (mVs ^-1 ) and applied at a voltage of 0 volts (V). ) to 1 volt, and normalize the measured value to the capacitance of a 1 gram (g) carbon nanotube electrode; then plot the cycle number versus capacitance to analyze the cycle life and compare the cycle number Capacitance plotting compares the effect of carbon nanotubes grown under different conditions on the capacitance and lifetime of the electrodes.

(2) Observation of field effect emission scanning electron microscope

Each sample was placed under a field emission scanning electron microscope to observe the analysis at a magnification of 10,000 times to 100,000 times.

(3) Observation by penetrating electron microscope

Each sample was placed under a transmission electron microscope, and the analysis was observed at a magnification of 40,000 to 80,000 times.

(4) Test and analysis of micro Raman spectrometer

The degree of graphitization (I _G /I _D value) of the carbon nanotube electrode can be detected by a micro-Raman spectrometer and used to determine the life of the carbon nanotube electrode.

Preparation Example 1: Preparation of Substrate

A silicon foil having a volume of 1 x 1 x 0.05 cubic centimeters (cm ³ ) (or 1 x 2 x 0.05 cubic centimeters) was prepared. The ruthenium foil is immersed in a solution containing de-ionized water and acetone, and the volume ratio of deionized water to acetone is 1:1; and then oscillated by ultrasonic for 15 min for degreasing, and then, It was placed in an oven and dried at a temperature of 50 ° C to make the weight of the degreased enamel foil constant.

A titanium target of 3.5-inch disk was placed on top of the above-mentioned tantalum foil at a distance of 10 cm (cm) and a vacuum of 7 × 10 ^-6 torr was applied to the sputtering background. In the environment, the sputtering time is 1.5 hours, the sputtering power is 60 W, the sputtering pressure is 20 mTorr, and the argon volume flow is 25 cm ³ /min. Using radio frequency magnetron sputtering (radio frequency) Magnetron sputtering) deposits titanium on the surface of the tantalum foil to form a tantalum foil containing titanium on the surface, and does not heat the substrate during sputtering.

Next, a 3.5-inch-diameter cobalt target was placed on the surface of the tantalum foil containing titanium on the surface, and the distance was 10 cm, and the sputtering background pressure was 7×10 ^-6 torr. In a vacuum environment, the sputtering time is 10 min, the sputtering power is 50 W, the sputtering pressure is 5 mtorr, and the argon volume flow rate is 25 cm ³ /min. The cobalt is deposited on the surface by RF magnetron sputtering. The surface of the tantalum foil of titanium, that is, the titanium system, is located between the surface of the cobalt and the tantalum foil to form a substrate having a surface covered with cobalt/titanium, wherein cobalt is used as a catalyst.

Preparation Example 2: Pretreatment of Cobalt with Hydrogen Plasma

The substrate with the cobalt/titanium coating on the surface obtained in Example 1 was placed in a reaction chamber (reaction conditions: radio frequency plasma with a frequency of 13.56 MHz and a maximum power of 100 W), and the background pressure of the reaction chamber was pumped to 7×10. ^-6 torr, hydrogen volume flow rate is 50 cm ³ /min, plasma pressure is controlled to 5 torr, plasma power is 50 W, substrate temperature is 500 ° C, and time is 8 min.

Preparation Example 3: Preparation of a Carbon Nanotube Electrode by Thermal Chemical Vapor Deposition (TCVD)

In this embodiment, a carbon nanotube is grown on a substrate having a cobalt/titanium coating on the surface by thermal chemical vapor deposition under various conditions.

Sample 1: The substrate having the cobalt/titanium coating on the surface of Preparation Example 1 was placed in a quartz boat, and the quartz boat was placed in a quartz tube of a high temperature furnace and heated to 700 ° C. Acetylene (C ₂ H ₂ ) and argon (Ar), wherein the acetylene volume flow rate is 50 cm ³ /min, the argon volume flow rate is 100 cm ³ /min; and the ammonia gas volume flow rate of 50 cm ³ /min is introduced. After 20 minutes, the carbon nanotubes are directly grown on the substrate, and a carbon nanotube can be obtained as shown in "Sample 1" in the following text; to increase the conductivity of the substrate, a small amount of electrically conductive adhesive (electrically conductive cement) A carbon nanotube electrode is obtained by fixing a cobalt/titanium coated substrate having a carbon nanotube to an aluminum current collector.

Sample 2: The substrate with the cobalt/titanium coating on the surface of Preparation Example 1 was placed in a quartz boat, and the quartz boat was placed in a quartz tube of a high temperature furnace and heated to 750 ° C. The remaining preparation steps were the same as the preparation steps of the sample 1. In the same manner, the obtained carbon nanotubes are represented by "sample 2" in the following texts.

Sample 3: The substrate with the cobalt/titanium coating on the surface of Preparation Example 1 was placed in a quartz boat, and the quartz boat was placed in a quartz tube of a high temperature furnace and heated to 800 ° C. The remaining preparation steps were the same as the preparation steps of the sample 1. In the same manner, the obtained carbon nanotubes are represented by "sample 3" in the following texts.

Sample 4: The substrate having the cobalt/titanium coating on the surface of Preparation Example 1 was placed in a quartz boat and heated to 750 ° C in a high temperature furnace. The preparation steps were the same as those in the sample 1 except that ammonia gas was not introduced. The obtained carbon nanotubes are represented by "Sample 4" in the following texts.

Sample 5: The substrate with the cobalt/titanium coating on the surface of Preparation Example 1 was placed in a quartz boat, heated to 750 ° C in a high temperature furnace, and a volume flow rate of ammonia of 40 cm ³ /min was introduced, and the remaining preparation steps were performed. The preparation steps of the sample 1 were the same, and the obtained carbon nanotubes were represented by "sample 5" in the following text.

Sample 6: The substrate with cobalt/titanium on the surface of Preparation Example 1 was placed in a quartz boat, heated to 750 ° C in a high temperature furnace, and a volume flow of ammonia gas of 60 cm ³ /min was introduced, and the remaining preparation steps were all with the sample. The preparation steps of 1 are the same, and the obtained carbon nanotubes are represented by "sample 6" in the following texts.

Sample 7: A substrate having a cobalt/titanium coating on the surface of Preparation Example 2 was placed After the quartz boat was heated to 750 ° C in a high temperature furnace, the remaining preparation steps were the same as those in the preparation of Sample 1, and the obtained carbon nanotubes were represented by "Sample 7" in the following text.

Sample 8: The substrate with the cobalt/titanium coating on the surface of Preparation Example 2 was placed in a quartz boat, heated to 750 ° C in a high temperature furnace, and a volume flow of hydrogen of 11 cm ³ /min was introduced, and the remaining preparation steps were all with the sample. The preparation steps of 1 are the same, and the obtained carbon nanotubes are represented by "Sample 8" in the following text.

Sample 9: The substrate with the cobalt/titanium coating on the surface of Preparation Example 2 was placed in a quartz boat, heated to 750 ° C in a high temperature furnace, and a volume flow of hydrogen of 16 cm ³ /min was introduced, and the remaining preparation steps were all with the sample. The preparation steps of 1 are the same, and the obtained carbon nanotubes are represented by "sample 9" in the following texts.

Sample 10: The substrate with the cobalt/titanium coating on the surface of Preparation Example 2 was placed in a quartz boat, heated to 750 ° C in a high temperature furnace, and a volume flow of hydrogen of 21 cm ³ /min was introduced, and the remaining preparation steps were all with the sample. The preparation steps of 1 are the same, and the obtained carbon nanotubes are represented by "sample 10" in the following texts.

Table 1 shows the growth environment of each sample under different conditions. Samples 1 to 3 fixed the ammonia volume flow rate to 50 cm ³ /min to compare the effects of different heating temperatures on the growth of carbon nanotubes; sample 2 and sample 4 to sample 6 fixed the heating temperature to 750 ° C. To compare the effects of different ammonia volume flow rates on the growth of carbon nanotubes.

Samples 7 to 10 were prepared by placing a substrate having a cobalt/titanium coating on the surface of Preparation Example 2 on a quartz boat, fixing the heating temperature to 750 ° C, and fixing the ammonia gas volume flow rate to 50 cm ³ /min to compare different hydrogen gases. The effect of volume flow on the growth of carbon nanotubes.

Example 1 Analysis of Growth Carbon Tubes at Different Temperatures

This embodiment utilizes the electrochemical charge and discharge test, field emission emission scanning electron microscope observation, and microscopic Raman spectrometer test analysis as described in "Materials and Methods" to evaluate different temperatures for growing carbon nanotubes. The impact.

Please refer to FIG. 1 , which is a comparison result of the specific capacitance of the sample 1 to the sample 3 and the number of cycles. As can be seen from Fig. 1, when the number of cycles is 100, the heating temperature is increased from 700 ° C to 750 ° C, but the heating temperature is decreased from 750 ° C to 800 ° C; please refer to Table 2 The average specific surface area of the sample 2 grown at a heating temperature of 750 ° C is larger than the average specific surface area of the sample 3 grown at a heating temperature of 700 ° C or the sample 3 grown at 800 ° C, so that the sample grown at a heating temperature of 750 ° C The specific capacitance value of 2 is higher than the specific capacitance value of sample 3 grown at 700 ° C or sample 3 grown at 800 ° C.

Please refer to FIG. 2A to FIG. 2C , which are graphs of the results of the field emission scanning electron microscope observation of the sample 1 to the sample 3, respectively. Compared with sample 1 (Fig. 2A) grown at 700 °C or sample 3 (Fig. 2C) grown at 800 °C, sample 2 (Fig. 2B) with a heating temperature of 750 °C has a uniform and vertical alignment tendency; When the sample 2 is grown at °C, the electrolyte ion is more permeable to the bottom of the carbon nanotube, and the electroactive site at the bottom can be fully utilized, which can further improve the ratio. Capacitance value. In addition, when the heating temperature is 750 ° C, the sample 2 is obtained. When the heating temperature is 750 ° C, it is known from Table 2 that the I _G /I _{D is} large, that is, the amount of amorphous carbon is small, and the heating temperature is 750. The specific capacitance decay rate of the °C carbon nanotube electrode is slower than the heating temperature of 700 ° C or 800 ° C.

Example 2 Analysis of different ammonia gas volume flow rates for growing carbon nanotubes

This embodiment utilizes electrochemical charge and discharge tests, field emission emission scanning electron microscope observations, and transmission electron microscope observations as described in "Materials and Methods" to evaluate the flow rate of different ammonia gas flows for growth of nanometers. The impact of carbon tubes.

Please refer to FIG. 3 , which is a comparison chart of the results of the specific capacitance and the number of cycles of sample 2 and sample 4 to sample 6. The heating temperature is fixed at 750 ° C to compare the specific volume flow of different ammonia gas to the specific capacitance of the carbon nanotubes. ring. The concentration and average specific surface area of sample 2, sample 5 and sample 6 grown by the volume flow of ammonia gas are higher than those of sample 4 grown without the volume flow of ammonia gas; as shown in Table 2 and Figure 3, When the number of cycles is 100, the sample 2, sample 5, and sample 6 grown by the flow rate of ammonia gas have a higher specific capacitance value.

Please refer to FIG. 4A and FIG. 4B , which are the results of the observation of the sample 4 and the sample 2 by field emission scanning electron microscope. 4A and 4B, the sample 2 (Fig. 4B) grown with a volumetric flow rate of ammonia of 50 cm ³ /min has a sample 4 (Fig. 4A) grown with a volume flow of ammonia of 0 cm ³ /min. The trend is more vertical. Further, as shown in Table 2, the growth of ammonia into the sample 2 I _G / I _D significantly higher than the samples without ammonia gas I _G / I _D value of 4, i.e., no ammonia gas The grown sample 4 has a large amount of amorphous carbon, which means that ammonia gas can effectively suppress the generation of amorphous carbon, and as shown in FIG. 3, the specific capacitance decrease rate of the sample 4 grown without the ammonia gas is introduced. The rate of decrease in specific capacitance of sample 2 grown faster than the volumetric flow rate of ammonia gas at 50 cm ³ /min.

Please refer to FIG. 5A and FIG. 5B , which are graphs of the results of observation of the sample 4 and the sample 2 by a transmission electron microscope. 5A and 5B, the sample 2 (Fig. 5B) grown with a volumetric flow rate of ammonia of 50 cm ³ /min has a sample 4 (Fig. 5A) grown with a volume flow of ammonia of 0 cm ³ /min. Bamboo-like structures are produced.

Example 3 Hydrogen plasma pretreatment analysis of growing carbon nanotubes

In this embodiment, the electrochemical charge and discharge test and the field effect emission scanning electron microscope observation and analysis as described in "Materials and Methods" are used to evaluate the effect of hydrogen plasma pretreatment on the growth of carbon nanotubes.

Please refer to FIG. 6 , which is a comparison chart of the results of the specific capacitance and the number of cycles of sample 2 and sample 7. It can be seen from Fig. 6 that the specific capacitance value of the sample 7 grown by the hydrogen plasma pretreatment catalyst is higher than the specific capacitance value of the sample 2 which is not grown by the hydrogen plasma pretreatment catalyst, and the hydrogen plasma pretreatment catalyst is used. The rate of decrease in the specific capacitance of the grown sample 7 is similar to the rate of decrease in the specific capacitance of the sample 2 which is not grown by the hydrogen plasma pretreatment catalyst. It can be seen from Table 2 that the degree of graphitization (I _G /I _D value) of the sample 7 grown by the hydrogen plasma pretreatment catalyst and the sample 2 not grown by the hydrogen plasma pretreatment catalyst are almost the same, so hydrogen is used. The ratio of the specific capacitance drop rate of the sample 7 grown by the plasma pretreatment catalyst is similar to that of the sample 2 which is not grown by the hydrogen plasma pretreatment catalyst.

Please refer to FIG. 7A and FIG. 7B , which are the results of observation of the sample 2 and the sample 7 by field emission scanning electron microscope. It can be seen from Fig. 7B that after the catalyst is pretreated by hydrogen plasma, the cobalt oxide on the surface of the catalyst is reduced to retain the activity of the catalyst cobalt, and the catalyst is formed into a nano-grain structure to grow as a carbon nanotube. a nucleation seed, and as shown in Table 2, the sample 7 grown via the hydrogen plasma pretreatment catalyst has a larger average specific surface area than the sample 2 grown without the hydrogen plasma pretreatment catalyst. The specific capacitance value of the sample 7 grown by the hydrogen plasma pretreatment catalyst is higher than the specific capacitance value of the sample 2 which is not grown by the hydrogen plasma pretreatment catalyst.

Please refer to FIG. 8 , which is a cyclic voltammogram of sample 7 under the condition that the scanning rate is 100 mV/s and the electrolyte is 0.1 MH ₂ SO ₄ .

Example 4 Analysis of Different Hydrocarbon Volume Flows for Growing Carbon Tubes

This embodiment utilizes the electrochemical method as described in "Materials and Methods" Charge and discharge test analysis to evaluate the effect of different hydrogen volume flow rates on the growth of carbon nanotubes.

Please refer to FIG. 9 , which is a comparison chart of the results of the specific capacitance and the number of cycles of the sample 8 to the sample 10. Referring to Table 3, the surface area of the sample 9 grown with a hydrogen flow volume of 16 cm ³ /min is higher than the sample 8 grown with a flow volume of 11 cm ³ /min, and the flow volume of the introduced hydrogen gas is The sample 10 grown at 21 cm ³ /min has a higher specific capacitance value than the sample 9 grown with a hydrogen flow volume of 16 cm ³ /min.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. The present invention has been disclosed in the preferred embodiments, but is not intended to limit the present invention. A person skilled in the art can make some modifications or modify equivalent changes in the above-described technical contents without departing from the technical scope of the present invention. The invention is not limited to any simple modifications, equivalent changes and modifications of the above embodiments.

Fig. 1 is a graph comparing the results of the specific capacitance and the number of cycles of Samples 1 to 3 obtained in the preparation example of the present invention.

2A to 2C are samples 1 obtained in the preparation example of the present invention, respectively. The results of the observation of the sample 3 by field emission scanning electron microscope were carried out.

Fig. 3 is a graph comparing the results of the specific capacitance and the number of cycles of sample 2 and sample 4 to sample 6 obtained in the preparation example of the present invention.

4A and 4B are graphs showing the results of field-effect emission scanning electron microscope observation of Sample 4 and Sample 2 obtained in the preparation example of the present invention, respectively.

5A and 5B are graphs showing the results of observation of a sample 4 and a sample 2 obtained by a penetration electron microscope, respectively, in the preparation example of the present invention.

Fig. 6 is a graph comparing the results of the specific capacitance and the number of cycles of the sample 2 and the sample 7 obtained in the preparation example of the present invention.

7A and 7B are the results of the field emission scanning electron microscope observation of the sample 2 (the catalyst is not treated with hydrogen plasma) and the sample 7 (the catalyst is treated with hydrogen plasma) obtained in the preparation example of the present invention, respectively. Figure.

Figure 8 is a cyclic voltammogram of Sample 7 obtained in the preparation of the present invention.

Fig. 9 is a graph comparing the results of the specific capacitance and the number of cycles of the sample 8 to the sample 10 obtained in the preparation example of the present invention.

Claims (8)

A method for preparing a carbon nanotube, comprising: providing a catalyst-titanium-coated substrate on a surface; and pre-treating the substrate with radio frequency hydrogen-plasma After pretreat, ammonia gas and hydrogen are introduced at a heating temperature by thermal chemical vapor deposition (TCVD) to form a vertical alignment, high concentration and low amorphous state. Carbon nanotubes, wherein the heating temperature is between 700 ° C and 800 ° C, and the volume flow rate of ammonia gas is between 40 cm ³ /min and 60 cm ³ /min, and the volume flow rate of hydrogen is between 11 cm. ³ / min to 21 cm ³ /min. The method of claim 1, wherein the catalyst is cobalt (Co). The method of claim 1, wherein the substrate is graphite or silicon. The method of claim 1, wherein the heating temperature is 750 °C. A carbon nanotube comprising the method of any one of claims 1 to 4, wherein the axial direction of the carbon nanotube extends between about 85 and 95 degrees from the horizontal surface of the substrate. Vertically aligned; the specific surface area of the carbon nanotubes is between 2.36×10 ¹⁶ nm ² /cm ² and 2.67×10 ¹⁶ nm ² /cm ² ; the degree of graphitization of the carbon nanotubes (I _G /I _{The D} value) is between 0.89 and 0.95. A carbon nanotube electrode comprising the carbon nanotube of claim 5. An electrochemical capacitor comprising the carbon nanotube electrode of claim 6. A battery comprising the carbon nanotube electrode as claimed in claim 6.