KR101454401B1 - Carbon nanotube electrodes by post-thermal oxidation and its method - Google Patents

Abstract

 The present invention relates to a carbon nanotube electrode, comprising: a first step of mixing a carbon nanotube powder and a dispersant with a solvent to prepare a carbon nanotube dispersion solution; A second step of coating or transferring the dispersion solution of the first step onto a substrate; And a third step of subjecting the sample prepared in step 2 to a post-heat treatment at a temperature of 250 ° C. to 550 ° C. in an oxygen atmosphere. The present invention also provides a method of manufacturing a carbon nanotube electrode by post-annealing oxidation. Preferably, the method further comprises a second post-heat treatment step of vacuum-drying the sample after the third step at a temperature of 20 to 150 ° C. The oxygen required for the first post-annealing process may be one or two or more of oxygen-enriched atmosphere, separate oxygen gas injection, or oxidation of a polymer such as polycarbonate, and the carbon nano The thickness of the tube film is made to be 0.5 탆 or less. The present invention improves the hydrophilicity of the surface of the electrode drastically by oxidizing the surface of the electrode through post-heat treatment to improve the interaction with the ions in the organic electrolyte, so that the reaction time required for the reduction reaction of electron transfer at the interface with the electrolyte, The electron transport performance can be improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a carbon nanotube electrode manufactured by a post-

The present invention relates to a carbon nanotube electrode, and more particularly, to a carbon nanotube electrode capable of facilitating interaction with ions in an organic electrolyte by improving hydrophilicity of an electrode surface to be brought into contact with an electrolyte by post- The present invention relates to a carbon nanotube electrode manufactured by a post heat treatment oxidation method which can achieve an excellent transparency and an electrochemical performance corresponding to platinum while minimizing the amount of a carbon nanotube material to be carried.

In general, carbon nanotubes have electrical conductivity similar to that of metals, have a large specific surface area, are chemically and mechanically stable, and serve as catalysts when used as electrodes for electrochemical reactions. It is expected to replace expensive platinum electrodes that have been used previously. It can also be used as an electrochemical electrode for use in other cells, supercapacitors, and the like.

Considering the case of the dye-sensitized solar cell, the dye-sensitized solar cell has a structure in which a photosensitive n-type semiconductor oxide oxide film capable of absorbing photoelectrons and moving to an external electrode, And the excited electrons are injected into the n-type semiconductor oxide layer in the electrolyte layer, and ions that supply electrons to the oxidized dye are continuously absorbed. The electrons are supplied to the photoelectrode and the oxidized ions move to the counter electrode across the electrolyte layer. The oxidized ions receive the electrons through the reduction reaction at the counter electrode and then move to the photoelectrode side, and continuously convert the solar energy into electrical energy.

In this case, it is important to minimize the loss of electrons in the counter electrode in order to maximize the catalytic characteristics by minimizing the ionization and reduction reaction rate and interface resistance in the electrolyte. Conventionally, noble metals such as platinum and palladium are used as materials meeting these requirements, but they are expensive and have limited reserves, and chemical stability in a strong acid electrolyte is questioned over a long period of use.

To solve this problem, a technology has been developed that utilizes carbon nanotubes as counter electrodes, which are relatively inexpensive and have excellent chemical stability in the electrolyte. The carbon nanotube counter electrode is manufactured by applying a paste prepared by mixing a carbon nanotube with a polymer binder to a substrate using a screen printing and a spraying process, and removing the insulating binder and organic impurities through heat treatment Post-processing is included.

Referring to FIGS. 1 and 2, an electrode structure of a general carbon nanotube will be described. FIG. 1 is a view showing an electrode structure of a conventional carbon nanotube. As shown, when the carbon nanotube film 20 coated on the surface of the conductive substrate 10 is used as a counter electrode, the cost is relatively low and the chemical stability is excellent. However, when the thickness of the carbon nanotube film is Lt; / RTI > In this case, it is opaque due to the thickness of the carbon nanotube film, and a large amount of carbon nanotubes are used.

As one method for solving such a problem, as shown in FIG. 2, carbon nanotubes are formed in the form of microballs 20 'and applied to a conductive substrate. In this case, the amount of the carbon nanotubes to be used is relatively small and the transparency is improved, so that the translucent electrode can exhibit the performance similar to that of platinum, however, there is a problem that a separate micro ball type fabrication process is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above needs, and it is an object of the present invention to provide a thin carbon nanotube film having transparency by using a carbon nanotube dispersion and post-heat treatment thereof in an oxygen source, The present invention aims to provide a carbon nanotube electrode by heat treatment oxidation method and a manufacturing method thereof by making it possible to use a small amount of carbon nanotubes by achieving a high efficiency catalyst electrode by reducing a time constant and an interface resistance.

According to an aspect of the present invention, there is provided a method of manufacturing a carbon nanotube dispersion, comprising: a first step of mixing a carbon nanotube powder and a dispersant with a solvent to prepare a carbon nanotube dispersion solution; A second step of coating or transferring the dispersion solution of the first step onto a substrate; A third step of subjecting the sample prepared in step 2 to a post-heat treatment at a temperature of 250 to 550 ° C. in an oxygen atmosphere to oxidize the carbon nanotube surface to impart hydrophilicity; And a second post-heat treatment step of vacuum-drying the sample that has undergone the third step at a temperature of 20 to 150 ° C to remove water. The present invention also provides a method of manufacturing a carbon nanotube electrode by post-annealing oxidation.

Preferably, the oxygen required in the post-heat treatment process is in atmospheric, separate oxygen gas injection, or oxidation of a polymer such as polycarbonate, and the thickness of the carbon nanotube film is 0.5 Mu] m or less, and the post-heat treated carbon nanotube film formed on the substrate in an oxygen atmosphere is subjected to a second post-heat treatment in vacuum drying at a temperature of 20 to 150 [deg.] C

The present invention can increase conversion efficiency in an energy conversion device including a dye-sensitized solar cell by increasing the electrode reaction efficiency in a carbon nanotube electrochemical electrode. In particular, by oxidizing the electrode surface through post-heat treatment, the hydrophilicity of the electrode surface is drastically improved to improve the interaction with ions in the electrolyte, thereby reducing the reaction time and interface resistance required for the reduction reaction of electron transfer at the interface with the electrolyte It is possible to improve the electron transfer performance.

In addition, since it is made thinner and more uniform than the conventional one, it is possible to use a small amount of carbon nanotubes, and the transmittance to visible light is further improved, so that it is possible to achieve high transmittance and high performance similar to those of conventional platinum, There are advantages that can be used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an electrode structure of a conventional carbon nanotube. FIG.
BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a carbon nanotube.
3 is a conceptual view of a carbon nanotube electrode post-heat-treated in an oxygen atmosphere on a conductive substrate according to the present invention.
4 is a view illustrating a process of fabricating a carbon nanotube electrode by a post-heat treatment oxidation method according to the present invention.
5 is a graph showing a characteristic value of a dye-sensitized solar cell using an iodine (I ^- / I ₃ ^- redox pair) electrolyte of a carbon nanotube electrode according to the present invention.
6 is a graph showing a current-voltage characteristic curve of a dye-sensitized solar cell using a carbon nanotube electrode as a counter electrode according to the present invention.
7 is a graph showing an impedance spectrum of a dye-sensitized solar cell using an iodine (I ^- / I ₃ ^- redox pair) electrolyte of a carbon nanotube electrode according to the present invention.
FIG. 8 is a photograph of a carbon nanotube electrode manufactured by the present invention, wherein (a) is a surface scanning microscope photograph, (b) is a thermal analysis curve of a multi-walled carbon nanotube powder treated for 1 hour, and ) Is a diagram showing a contact angle with water, and (d) is a diagram showing a Raman spectrum.
FIG. 9 is a graph showing a transmittance curve of visible light according to the present invention. FIG. 9 (b) is a graph showing the transmittance (25%) and transmittance (75% FIG. 5 is a graph showing a battery current-voltage characteristic curve. FIG.
10 is a graph showing a characteristic value of a dye-sensitized solar cell using a cobalt-based (Co / (bpy) ₃ ) ^{3 + / 2 +} redox pair electrolyte of the carbon nanotube electrode according to the present invention.
11 is a graph showing a current-voltage characteristic curve of a dye-sensitized solar cell using a carbon nanotube electrode as a counter electrode according to the present invention.

According to the present invention, there is provided an electrode and a method for manufacturing the same, wherein carbon nanotubes in a thin film form are bonded to a conductive substrate to be used as a counter electrode in a dye-sensitized solar cell and as a general electrochemical electrode. And the electrode reaction performance is improved by post-annealing and oxidizing the nanotube electrode.

Hereinafter, a carbon nanotube electrode post-heat-treated on a conductive substrate according to the present invention and a method of manufacturing the same will be described with reference to the accompanying drawings.

3 is a conceptual view of a carbon nanotube electrode post-heat-treated on a conductive substrate according to the present invention.

As shown in the figure, a carbon nanotube (CNT) 200 is applied on a conductive substrate 100 in the form of a thin film. At this time, the carbon nanotube film has a thickness of about 0.5 탆 or less. It can be seen that this thickness is about 10 times or more thinner than the conventional thickness of 5 mu m or more. It goes without saying that the transmittance of visible light is increased due to such a thin film form. In this case, the transmittance with respect to visible light is increased to form a translucent shape, which means that it can be used as a transparent electrode. The surface of the carbon nanotubes according to the present invention is oxidized by a post heat treatment, thereby improving the hydrophilicity and increasing the energy conversion efficiency by improving the electron transfer performance. Hereinafter, a process for fabricating the carbon nanotube transparent electrode of the present invention having such a structure will be described with reference to the drawings.

4 is a view illustrating a process of fabricating a carbon nanotube electrode by the post-heat treatment oxidation method according to the present invention.

As shown in the figure, the most significant feature of the present invention is that the surface of the carbon nanotube film is oxidized by applying a dispersion of carbon nanotubes to a conductive substrate and then post-heating in the presence of oxygen.

First, the first step process will be described. Any conductive substrate such as FTO (ITO), a carbon nanotube conductive electrode, a metal substrate, a plastic substrate, and a fibrous substrate can be used as the base substrate. Then, a commercially available carbon nanotube powder and a dispersant are mixed with a solvent to prepare a dispersion solution. The solvent used herein may be any of water, alcohol, acetone, dimethylsulfoxide (DMSO), dimethylformamide (DMF), benzene, toluene, xylene, pyridine and tetrahydrofuran It may be used. The dispersing agent may be sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, Triton X, or the like. The solvent may be a dispersing agent for uniform dispersion of the carbon nanotube powder. Examples of usable dispersing agents include sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, ) Or a mixture of two or more of them may be used. These solvents and dispersants are generally usable in the production of carbon nanotube dispersions, and there is no particular limitation.

The second step is a step of coating or transferring the carbon nanotube dispersion solution prepared in step 1 on a conductive substrate, and any one of a spray coating method, a film transfer method, and an ink jet method may be used. However, such coating and transfer are different from conventional ones in that the amount of the carbon nanotubes is dramatically reduced by using a thinner film than the conventional one after completion of the post-heat treatment after the third step described later, and the transmittance to visible light is secured have. In the case of using a nanocarbon dispersion solution having excellent dispersibility, that is, a nanocarbon dispersion solution having no macroscopically solidified material, the amount of the electrode used is inversely proportional to the transmittance. It is preferable that the visible light transmittance of the carbon nanotube electrode is adjusted at a wavelength of 550 nm Adjusting it to 10% or more will be enough.

According to the existing nano-carbon electrode technology, the electrochemical performance similar to that of platinum is exhibited when the amount of the electrode is increased or the thickness is several micrometers or more. Therefore, the transmittance that can reduce the amount of nano-carbon material and realize electron transfer efficiency similar to platinum depends on the type of nano-carbon material or the shape of carbon nanotubes. The amount of material used or thickness is inversely related to the transmittance. The nano-carbon material shown in the embodiment of the present invention is a multi-walled carbon nanotube containing a large amount of structural defects. In the case where the coated or transferred electrode is uniform and flat, the electrode having a transmittance of 10% Electron transfer performance. An electrode having a transmittance of 10% or less is similar to the existing carbon nanotube electrode technology because it uses a large amount of material and has a low transmittance. The thickness of the electrode having a transmittance of 10% or more depends on the type and the type of the nano-carbon material. The thickness of the electrode having the 10% transmittance used in the embodiment is approximately 0.5 탆. Therefore, the application amount of various kinds of nano-carbon dispersion solution can be from 10 to 90% by measurement of transmittance.

Then, the third step is post-heat treatment in an oxygen atmosphere. In general, it is dried at about 100 ° C to volatilize only the solvent. In the present invention, however, a high-temperature heat treatment is performed under oxygen. This is for oxidation treatment of the electrode surface. That is, since the volatilization of the solvent is performed in an oxygen atmosphere as well as the volatilization of the solvent by the high-temperature oxidation method, oxygen oxidizes the surface of the carbon nanotube. This surface oxidation treatment improves the hydrophilicity of the surface of the carbon nanotube film in contact with the electrolyte, Facilitating interaction. The temperature by the heat treatment after the oxygen treatment is usually from 250 to 550 DEG C, and the oxygen source to be supplied may be carried out in the air or by using oxygen supplied by a separate oxygen supply or oxidation of a polymer such as polycarbonate Or a mixture of two or more of them may be used. A feature of the present invention is to achieve an electron transfer performance comparable to that of platinum even in the case of a uniform thin film having a small amount of consumption due to oxidation of the surface of the carbon nanotube film produced simultaneously with solvent volatilization through high temperature heat treatment in an oxygen atmosphere.

In the meantime, a conventional patent (Applicant: Korea Electrotechnology Research Institute, Application No.: 10-2006-0088792, post-annealed carbon nanotube electrode and dye-sensitized solar cell using the same) It is to be noted that the post-annealing process is not the surface treatment by the oxidation method but the insulating impurities existing in the carbon nanotubes are removed through the carbonization process by post-heat treatment at a temperature of 200 to 230 ° C., The present invention relates to a technique for improving the electrical conductivity of a carbon nanotube and the electrolyte by maintaining the characteristics of the surface of the carbon nanotube, It differs from existing technology in the processing technology.

The post heat treatment in this oxygen atmosphere is related to the pyrolysis characteristics of the material used. Chemically functionalized nano-carbon materials are preferred to avoid temperatures above 550 ° C because most of the material is oxidized and extinguished. At the post-annealing temperature lower than 550 ° C., the time for the complete oxidation is thermodynamically different, and the temperature and time at which the local oxidation only occurs on the surface of the electrode depend greatly on the characteristics of the nano-carbon material used and the type of oxygen source , Proper post-heat treatment temperature and time setting are required. Since the multi-wall carbon nanotube material shown in the embodiment of the present invention undergoes complete oxidation of the electrode when it is annealed at 550 ° C for at least 1 hour in the atmosphere, the annealing at 500 ° C for 30 minutes to 1 hour is preferably performed at an electrochemical performance The local oxidation of the surface of the electrode was made possible.

Next, the fourth step includes a second post-heat treatment step. This step is to remove the water molecule adsorption on the surface of the carbon nanotubes with improved hydrophilicity. That is, when post-heat treatment is performed using oxygen present in the atmosphere, since the hydrophilicity is improved, atmospheric moisture can be easily adsorbed on the surface of the electrode. That is, in an electrochemical application device using an organic solvent electrolyte, adsorbed water molecules can be a barrier for electron transfer, so that water molecules are removed. For this purpose, it is dried in a vacuum oven at a temperature of 20 to 150 ° C for 1 hour to 30 hours according to the state of humidity in the air, thereby completely removing water molecules. At this time, if the vacuum drying temperature is too high, not only the water molecules but also the oxygen-based hydrophilic functional groups introduced into the electrode surface by the post-heat treatment oxidation method in the third step may be removed, so that the vacuum drying temperature is preferably not higher than 200 ° C. Further, the vacuum drying time depends on the degree of hydrophilicity of the electrode surface after the post-heat treatment oxidation in the third step, the exposure time in the atmosphere of the electrode, the humidity of the exposed air, and the vacuum drying temperature. Vacuum drying at 45 to 12 hours is preferred when exposed to air of 60% relative humidity for less than 4 hours in the cooling and storage processes after post heat treatment.

After the above process, the fifth step is used as an electrochemical electrode, which is a conventionally used carbon nanotube electrode and can be used as a catalyst electrode in any of dye-sensitized solar cell including an electrolyte, super capacitor, and fuel cell .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Example

Step 1

To improve the dispersibility of carbon nanotubes, 0.1 g of commercially available multi-walled carbon nanotube powder is added to 100 ml of a solution prepared by mixing sulfuric acid and nitric acid in a volume ratio of 3: 1, and sonicated in an ice-filled water bath for 1 hour.

Water is added to the ultrasonic treated carbon nanotube solution, followed by filtering and drying, to obtain a carboxyl-functionalized carbon nanotube powder.

0.030 g of the functionalized carbon nanotube powder was dispersed in a 30 ml DMF solvent by ultrasonic treatment and centrifuged at 5,000 rpm for 10 minutes to remove the coagulant to collect only the supernatant with uniform dispersion It is used as carbon nanotube dispersion. Accordingly, the macroscopic non-uniformity of the surface of the carbon nanotube that can be formed when the dispersion is coated with the dispersion is eliminated.

Step 2

The prepared carbon nanotube dispersion solution is spray-coated on F-doped SnO ₂ to form a semi-transparent carbon nanotube electrode. At this time, the temperature of the conductive substrate was set at 115 ° C for uniform coating without stains. The loading amount or transmittance of the electrode is adjusted by changing the spraying time of the spray.

Step 3

The coated electrode is post-heat treated in an oxygen atmosphere. At this time, for the comparative example, comparative experiments were conducted by drying in an oven at 70 ° C. and post-heat treatment at 300 to 550 ° C. for 1 hour in the conventional manner.

Step 4

In the third step, the surface of the post-heat treated electrode under an oxygen atmosphere is dramatically increased in hydrophilicity. Therefore, this hydrophilicity enhancement can be adsorbed on the surface of the electrode. Water molecules adsorbed on the molecular basis can be a barrier for the electron transfer in the electrochemical application device using the organic solvent-based electrolyte. Therefore, Followed by vacuum drying in a vacuum oven at a temperature of 20 to 150 ° C for 1 hour to 30 hours to completely remove water molecules on the surface.

As described above, the surface hydrophilicity enhancement formed through the post-heat treatment under the oxygen of the third stage in the state of completely removing the surface water molecules not only reduces the interfacial resistance in the organic solvent-based electrolyte but also decreases the time constant of electron transfer ) By 10 times or more.

Step 5

The completed carbon nanotube electrode was used as a counter electrode of a dye-sensitized solar cell.

Hereinafter, the results of the experiment using the conductive substrate with the carbon nanotubes by the post-heat treatment oxidation unit as the counter electrode of the dye-sensitized solar cell will be described.

FIG. 5 is a graph showing a characteristic value of a dye-sensitized solar cell using an iodine-based (I ^- / I ₃ ^- redox pair) electrolyte according to the present invention, and FIG. 6 is a graph showing a characteristic value of a carbon nanotube Voltage characteristic curve of a dye-sensitized solar cell using an electrode as a counter electrode.

As shown in the figure, the visible light transmittance of carbon nanotubes is 25% (TR 25%) and is applied to a dye-sensitized solar cell using an iodine (I ^- / I ₃ ^- redox pair) electrolyte. It was found that the characteristics as a counter electrode in case of drying at 70 ° C and relatively low temperature drying at 150 ° C are poor and this is due to the high carbon nanotube / electrolyte interface resistance (R _CE ) as shown in the characteristic value of FIG. . On the contrary, the electrochemical characteristics were improved in the case of the oxygen heat treatment at 300 and 500 ° C, which is relatively high temperature, and the electrochemical characteristics are similar to those of the conventional platinum at 500 ° C.

7 is a diagram showing an impedance spectrum of a dye-sensitized solar cell using an iodine-based (I ^- / I ₃ ^- redox couple) electrolyte of a carbon nanotube electrode according to the present invention.

As shown in the figure, the visible light transmittance of the carbon nanotubes is 25% (TR 25%) and is applied to a dye-sensitized solar cell using an iodine (I ^- / I ₃ ^- redox pair) lt; ² > / cm < ² > light amount. It can be seen that the interface resistance (R _CE ) of the counter electrode after the heat treatment at 500 ° C. is reduced from 58.2 to 3.2Ω cm 2, which is similar to that of platinum, and Z _CE and Z _WE are separated. That is, it can be seen that the resistance to electron transfer and the characteristics of the electron transfer rate are improved by post-heat treatment.

FIG. 8 is a photograph of a carbon nanotube electrode manufactured by the present invention (a) is a surface scanning microscope photograph, (b) is a chart showing a thermal analysis curve of the MWNT powder treated for 1 hour, (D) is a diagram showing a Raman spectrum. Fig.

As shown in the photograph (a), the electrode structure of the outer carbon nanotube is maintained even in the general dry state of 70 and the heat treatment after the high temperature 500 under the present invention, and there is no change in the surface morphology . It can be seen that there is almost no weight loss up to 500 ° C as shown in the thermal analysis curve of (b), and it can be used as a carbon nanotube electrode. In (c), the contact angle is greatly improved due to the post-annealing. As can be seen from the graph of FIG. 4 (d), the increase in the D / G ratio due to the increase in the structural defects can be seen in the Raman measurement.

FIG. 9 is a graph showing a transmittance curve of visible light according to the present invention. FIG. 9 (b) is a graph showing the transmittance (25%) and transmittance (75% FIG. 6 is a graph showing a battery current-voltage characteristic curve.

As shown in the figure, a carbon nanotube electrode having a transmittance (25%) and a transmittance (75%) was used for the transmittance (100%) of visible light of an FTTHO glass substrate used as a conductive substrate. In this case, the transmittance (25%) has a thickness of 0.35 and the transmittance (75%) has a thickness of 0.15 μm. (b), when applied to a dye-sensitized solar cell using an iodine-based (I ^- / I ₃ ^- redox pair) electrolyte, the carbon nanotube electrode having a transmittance of 75% It can be seen that the solar cell characteristics are remarkably improved.

10 is a graph showing a characteristic value of a dye-sensitized solar cell using a cobalt (Co / (bpy) ₃ ) ^{3 + / 2 +} redox pair) electrolyte according to the present invention, Is a graph showing a current-voltage characteristic curve of a dye-sensitized solar cell using a carbon nanotube electrode as a counter electrode according to the present invention.

As shown in the figure, the visible light transmittance of the carbon nanotube was 25% (TR 25%), and the electrode thermally treated after 300 ° C had a dye response using the iodine (I ^- / I ₃ ^- redox pair) In the case of applying to the solar cell, the efficiency is lower than that of platinum, whereas the cobalt electrolyte shows a characteristic of being superior to platinum. It can be seen that high performance electrochemistry can be realized by relatively low heat treatment only when the redox couple of the electrolyte is larger than the existing iodine molecule (cobalt system).

According to the above experimental results, the hydrophilicity of the surface of the carbon nanotube electrode is improved due to the heat treatment at a high temperature under the oxygen atmosphere. Thus, the thickness of the carbon nanotube electrode can be further reduced to 0.5 μm or less, In this case, the transmittance to visible light is improved, so that it can be used as a transparent electrode with translucency. In the case of a dye-sensitized solar cell using a cobalt-based electrolyte, the post-heat treatment temperature can be further lowered. It can be seen that various applications are possible.

Claims (7)

A first step of mixing a carbon nanotube powder and a dispersant with a solvent to prepare a carbon nanotube dispersion solution;
A second step of coating or transferring the dispersion solution of the first step onto a substrate; And
A third step of post-heat-treating the sample prepared in step 2 in an oxygen atmosphere at a temperature of 250 to 550 ° C. to oxidize the carbon nanotube surface to impart hydrophilicity;
And a second post-heat treatment step of vacuum-drying the sample after passing through the third step at a temperature of 20 to 150 ° C to remove moisture. The method for manufacturing a carbon nanotube electrode according to claim 1, delete The method according to claim 1, wherein the oxygen required in the post-heat treatment process in the third step is one or two or more oxygen supplying environments selected from among air, separate oxygen gas injection, or oxidation of a polymer such as polycarbonate A method for manufacturing a carbon nanotube electrode by post heat treatment oxidation. 4. The method according to claim 3, wherein the thickness of the carbon nanotube film formed on the substrate is 0.5 m or less. A conductive substrate;
A carbon nanotube film formed on the conductive substrate and coated or transferred with a carbon nanotube dispersion solution and post-heated at a temperature of 250 to 550 ° C. in an oxygen atmosphere to oxidize the surface of the oxygen nanotube to impart hydrophilicity thereto; Carbon nanotube electrode produced by the post heat treatment oxidation method, [6] The method of claim 5, wherein the oxygen required in the post heat treatment process is one or two or more oxygen supply environments in the atmosphere, by separate oxygen gas injection or by oxidation of a polymer such as polycarbonate, The carbon nanotube electrode produced by the post heat treatment oxidation method, wherein the thickness is 0.5 mu m or less. The carbon nanotube film according to claim 5 or 6, wherein the post-heat treated carbon nanotube film formed on the substrate is subjected to a second post heat treatment for vacuum drying at a temperature of 20 to 150 ° C. Tube electrode.

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