KR101865993B1 - Nitrogen and Metal doped Porous Carbon Materials and Method of Manufacturing the Same - Google Patents

Abstract

The present invention relates to a porous carbon material in which a nitrogen-containing polymer is simultaneously doped with a nitrogen and a metal through a simple process, and a production method thereof.
The carbon material produced by the present invention can be used as a cathode material of a fuel cell which is an electric energy conversion device and an electrode material of a supercapacitor which is an electric energy storage device

Description

TECHNICAL FIELD [0001] The present invention relates to a porous carbon material doped with nitrogen and a metal, and a method of manufacturing the porous carbon material.

The present invention relates to a porous carbon material in which nitrogen and metal are simultaneously doped, and a method of manufacturing the same. The carbon material produced by the present invention can be used as a cathode material of a fuel cell which is an electric energy conversion device and an electrode material of a supercapacitor which is an electric energy storage device

Modern society, which has achieved a high level of civilization, has potential threats such as environmental pollution, and its seriousness is increasing. The importance of renewable energy, which is a measure to cope with this problem, has been emphasized, and related researches are actively conducted. In particular, among these research areas, fuel cells that convert environmentally friendly chemical energy of fuels into electric energy, and super capacitors, which are highly specialized in electric capacity as electric energy storage devices, show remarkable achievements.

First, in the case of fuel cells, electrochemical catalysts used in the anode are most actively studied. This is because the reaction rate of the oxygen reduction reaction (ORR: Oxygen Reduction Reaction) occurring at the anode is slow, which is why an effective catalyst is required. Platinum-based catalysts, which are currently being commercialized, are expensive, and research for developing non-whitening catalysts for the commercialization of fuel cells has been conducted for a long time. This is particularly true for carbon materials doped with nitrogen or boron atoms, and particularly the superiority of nitrogen-doped carbon materials has been disclosed (Bashyam, R. & Zelenay, P., Nature, 2006, 443: 63). In addition, it showed improved conductivity and catalytic activity by doping nitrogen with Graphene, which is one of the most popular carbon materials, and forming a hybrid through the introduction of a metal oxide (Liang, YYet al., Nat Mater, 2011, 10: 780).

Second, the storage capacity, which is the core of the supercapacitor, is inversely proportional to the distance between the plates and proportional to the area. Thus, if the distance between two plates is fixed, the area determines the storage capacity. However, since the size of the entire supercapacitor becomes larger when the surface area is larger, it is more effective to have a larger effective area than the surface area. In light of this, the majority of studies have focused on porous carbon materials with a wide surface area. In particular, activated carbon prepared by heat treatment of carbon precursor at high temperature is commercially used in supercapacitors (Pandolfo et al, Journal of Power Sources, 2006, 157: 11).

In this way, the surface area and the kind of the doped hetero element have a great influence on the catalytic activity of the fuel cell anode and the storage capacity of the supercapacitor. First of all, there are two main ways to increase the surface area of these carbon materials. The first is physical activation, which utilizes a gas that acts as an oxidant at high temperatures. The gas reaction can greatly increase the volume and surface area of the pores present in the carbon material, and temperature and reaction time are important parameters. The second is chemical activation, which proceeds at a lower temperature than the physical activation, and has the advantage of a shorter holding time and a relatively high yield. Potassium hydroxide (KOH), H3PO4, ZnCl2 and other reagents are mainly used for chemical activation. Of these, potassium hydroxide is widely used because it forms very small pores and high surface area (Wang et al, Journal of Materials Chemistry, 2012, 22: 23710).

A method of doping a carbon material with a hetero-element is widely used in which a specific gas (general air, argon, nitrogen, etc.) is flowed and subjected to heat treatment. This is because not only the process itself is simple but also the performance and safety of the hetero-element doped carbon material produced by heat treatment is excellent (Gupta, S., Tryk, D., Bae, I., Aldred, W. & Yeager , E., J. Appl Electrochem 1989, 19:19).

The scientific community has been studying fuel cells and supercapacitors by applying a variety of carbon materials to the aforementioned approach. In particular, studies based on carbon nanotubes (CNTs) and graphene, which have attracted attention as promising carbon materials, are showing the most active movements. Unlike other carbon materials, carbon nanotubes and graphenes have a wide effective surface area because all carbon atoms are exposed on the surface. In addition, since the electric conductivity is higher than that of the existing activated carbon, it has a strong point as a material to be used in electrochemistry. Despite these advantages, there is a need for additional research in commercialization due to the difficulty of mass production.

The present inventors paid attention to the fact that mass production is difficult and the manufacturing cost is large. In order to solve this problem, the present inventors focused on the development of a porous carbon material excellent in processability and unit price, not graphene. Thus, it has been confirmed that when potassium hydroxide activation is applied to polyacrylonitrile (PAN), which is a polymer containing nitrogen, a nitrogen-doped porous carbon material is obtained without a nitrogen precursor. In addition, it is possible to produce porous carbon doped in the form of cobalt oxide when the cobalt precursor is mixed with the nitrogen-doped porous carbon material by the impregnation method, and can be used as the anode catalyst and the super capacitor electrode of the fuel cell .

Korean Patent Laid-Open No. 10-2005-0063501 discloses a method of producing activated carbon fibers having a large specific surface area and increased storage capacity by carrying out a simple chemical and physical activation treatment so that polyacrylonitrile can be used as an electrode material of a supercapacitor Method. However, this is not a process of processing the polyacrylonitrile polymer itself, but has a limitation in that unnecessary processes and costs are added to the polyacrylonitrile polymer as a raw material.

An object of the present invention is to provide a method for producing a porous carbon material in which nitrogen and metal are simultaneously doped, which can be mass-produced. The present invention also provides a porous carbon material doped with nitrogen and metal which can be used as a cathode material and a super capacitor of a fuel cell.

Another object of the present invention is to provide an optimal content ratio of a precursor or an additive so as to exhibit excellent performance as a positive electrode material or a super capacitor of a fuel cell.

In one aspect, the present invention provides a method comprising: stabilizing a nitrogen-containing polymer in contact with air;

Mixing the stabilized polymer with an activator;

Carbonizing the polymer mixed with the activating agent to produce a nitrogen-doped porous carbon material;

Mixing the nitrogen-doped porous carbon material with a metal salt;

Impregnating the carbonaceous material with the carbonaceous material;

And then heat-treating (carbonizing) the carbonaceous material impregnated with the metal salt. The present invention also relates to a method for producing a porous carbon material doped with nitrogen and metal.

In another aspect, the present invention relates to a porous graphite structure made by the method, wherein nitrogen and metal are co-doped with the graphite structure.

Since the present invention uses a polymer containing nitrogen and uses relatively inexpensive reagents (such as potassium hydroxide and cobalt acetate), the production cost can be effectively reduced. In addition, since the present invention can provide a porous carbon material by oxidizing and heat-treating a nitrogen-containing polymer, mass production is also possible. In addition, the carbon material of the present invention exhibits current density or capacitance corresponding to conventional graphene or platinum-based materials by beneficially changing the shape of a previously doped nitrogen functional group in a doping process such as cobalt. Based on these characteristics, it is believed that the present invention will contribute to the mass production and commercialization of fuel cell anodes and supercapacitor materials.

FIG. 1 is a flow chart showing a step of producing a porous carbon in which nitrogen and metal are simultaneously doped according to the present invention.
Figure 2 shows the variation of the chemical structure occurring in the stabilization step.
Figure 3 shows the variation of the chemical structure resulting from the carbonization step.
Fig. 4 shows the specific structure of nitrogen that can be generated when synthesizing a nitrogen-doped porous carbon material. The name of each nitrogen structure is shown in a gray box.
5 is a photograph of the synthesis process of the nitrogen-doped porous carbon material. (a: polyacrylonitrile subjected to a stabilization step, b: polyacrylonitrile and potassium hydroxide before mixing, c: polyacrylonitrile-based nitrogen-doped porous carbon material after synthesis)
Fig. 6 is an image showing the surface change of the carbon structure due to activation of potassium hydroxide. Fig.
FIG. 7 is a photograph showing a process of mixing a nitrogen-doped porous carbon material with a cobalt precursor (cobalt acetate) and impregnating the mixture with a sound wave treatment.
8 is an image showing the change in surface structure due to cobalt doping.
FIG. 9 shows the performance of the synthesized nitrogen and cobalt-doped porous carbon material as a fuel cell cathode material. For the measurement, a rotating ring-disk electrode measurement method was used.
Fig. 10 shows the performance of the synthesized nitrogen and cobalt-doped porous carbon material as a supercapacitor.
Fig. 11 shows capacitance values according to potassium hydroxide throughput and cobalt doping amount.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing steps of producing the porous carbon doped with nitrogen and metal of the present invention. Fig. Figure 2 shows the variation of the chemical structure occurring in the stabilization step. Figure 3 shows the variation of the chemical structure resulting from the carbonization step.

Referring to FIG. 1, the present invention includes a stabilization step, mixing with an activator, a carbonization step, a metal salt mixing step, an impregnation step and a heat treatment (carbonization) step.

The stabilization step is a step of reacting the nitrogen-containing polymer with air.

Referring to FIG. 2, the stabilization step may be a step of cyclizing the polymer containing nitrogen by an oxidation reaction. In the stabilization step, the polymer is stabilized while being cyclized, and the nitrogen is included in the cyclized hydrocarbon structure to increase the nitrogen content on the pore surface.

Referring to FIG. 2, the stabilization step is performed including a dehydration reaction and a cyclization reaction. As a result, the stabilized polymer may contain a considerable amount of nitrogen in the ring structure.

The nitrogen-containing polymer includes nitrogen and is not particularly limited as long as it is a polymer which can be used as a carbon precursor which can be changed into a carbon material through carbonization. In the present invention, polyacrylonitrile ( polyacrylonitrile (PAN), polyaniline (PANI), polypyrrole (PPy), and polyrhodanine. PAN may be used alone, or PANI or PPy may be mixed with PAN at a weight ratio of 1 to 90%.

The stabilization step may be performed at a temperature of 1 to 20 ° C / min and at a temperature of 250 to 300 ° C for 1 to 3 hours. If the rate of temperature rise is less than 1 / min, the time required takes a long time. If the rate is more than 20 / min, the reaction occurs sharply and there is a problem in stabilization. If the stabilizing temperature is less than 250, the stabilization time is long. If the stabilizing temperature is more than 300, the polymer may melt.

At this time, the flow rate of the supplied air is preferably 50 to 200 ml / min. If the flow rate is less than this, the oxygen required for stabilization may be insufficient. On the other hand, when the amount is exceeded, there is a problem that the polymer is not stabilized and burned. As the polymer is oxidized by oxygen, conversion to a more stable chemical structure occurs, exposing a large amount of nitrogen to the surface. Therefore, there is an advantage that it can be used for an electrode of a fuel cell or a supercapacitor.

The mixing step is a step of mixing the stabilized polymer with an activator.

The activating agent may be potassium hydroxide, sodium hydroxide, H3PO4, ZnCl2.

The polymer treated with the activator can broaden the surface area of the carbon material in the carbonization step and increase the number of pores.

The mixing ratio of the polymer and potassium hydroxide is preferably 1: 0.5 to 1: 5. At this time, the solid potassium hydroxide may be directly mixed with the polymer, or potassium hydroxide may be dissolved in water, alcohol or an organic solvent, followed by mixing with the polymer and then evaporating. The alcohol may be ethanol or a C1-C7 alcohol, and the organic solvent may be THF, acetone, etc., but is not limited thereto.

The carbonization step is a step of carbonizing the polymer mixed with the activating agent to prepare a nitrogen-doped porous carbon material.

The carbonization step is a step of transferring the cyclized polymers to a graphite structure by heat treatment in the presence of an inert gas. Referring to FIG. 3, as the temperature increases, the cyclized polymer binds to the adjacent polymer and is transferred to a carbon material exhibiting a nitrogen-containing porous graphite structure.

The carbonization step is carried out at a rate of 1 ~ 10 ° C / min under an inert gas and maintained at 600 ~ 1300 ° C for a predetermined time. The heating rate is suitably from 1 to 10 / min. When the temperature is maintained at 600 to 1300 ° C for a predetermined time, the activation is successful. If the heating rate is less than 1 / min, the heat treatment time is unnecessarily increased. If the heating rate is more than 10 / min, the pores are not sufficiently developed. If the heat treatment temperature is lower than 600 ° C, the surface area of the polymer decreases. If the temperature exceeds 1300 ° C, the yield decreases and the corrosion of the heat treatment apparatus becomes more severe, thereby affecting the durability. At this time, in order to prevent the polymer from being oxidized and disappearing, the reaction is performed under an inert gas such as nitrogen or argon, and further gas such as carbon dioxide (CO2) may be added to the polymer for further reaction.

In addition, the carbonization step includes a reaction in which the activator reacts with a part of carbon forming the carbon material skeleton to form the porosity.

When potassium hydroxide is used as the activating agent in the carbonization step, the process of forming the porosity is as shown in the following reaction formula.

[Reaction Scheme 1]

4KOH + C? 4K + CO ₂ + 2H ₂ 0 (1)

_{4KOH + 2CO 2 ↔ 2K 2 CO} 3 + 2H 2 0 (2)

Carbon reacts with potassium hydroxide, primarily destroying the graphite structure, and the gases (carbon dioxide and water vapor) produced in the process form additional porosity (1). In addition, it plays a role in expanding the holes formed by other solid by-products (K, K 2 CO 3, etc.) (2). Through the above three steps, a nitrogen-doped porous carbon material having both porosity and graphite characteristics can be produced in the present invention.

The method may further comprise the step of performing the acid treatment after the step of producing the nitrogen-doped porous carbon material to remove unreacted residues.

That is, after the carbonization step, a neutralization reaction is carried out to remove unreacted residues (residual activator, potassium hydroxide, etc.). The neutralization reaction may be carried out with a strong acid selected from the group consisting of hydrochloric acid (HCl), perchloric acid (HClO4), nitric acid (HNO3) or sulfuric acid (H2SO4). In this case, the concentration of the strong acid is preferably 0.1 to 10M, and when the concentration of the strong acid is less than 0.1M, the residue is insufficient to remove the residue. If the concentration exceeds 10M, There is a problem that can remain.

The present invention includes the step of mixing the nitrogen-doped porous carbon material with a metal salt. As the metal salt, the metal salt may be a transition metal-based salt such as cobalt salt, nickel salt, iron salt, and manganese salt.

Examples of the cobalt salt include cobalt acetate and cobalt nitrate.

The mixing ratio of the carbon material to the metal salt may be 1: 0.05 to 1: 0.5, preferably 1: 0.05 to 0.2.

The impregnating step is a step of injecting the metal salt into the pores of the porous carbon material.

The impregnating step includes a step of dissolving the metal salt in a solvent (such as water or ethanol) to form a liquid phase, and a step of stirring a mixture of the metal salt solution and the polymer. The stirring is performed by ultrasonic treatment. Since the mobility of the cobalt ions can be increased through the ultrasonic treatment, it becomes easy to settle in the pores of the porous carbon. This process can be replaced by agitation using a magnet. Since the solvent must be removed from the treated product, it is dried at a high temperature of 100 ° C or higher.

The heat treatment step may be performed at a temperature of 1 to 10 ° C / min under an inert gas atmosphere and then heat-treated at 800 to 900 ° C for 1 to 3 hours.

More specifically, the mixture after the ultrasonic treatment has been dried is in the form of a powder, which is subjected to metal doping through heat treatment at 800 ° C or higher. When the heat treatment is performed at a temperature of 800 ° C or higher, cobalt doping is performed, for example, in the form of Co ₃ O ₄ . Thereafter, filtration is performed using water and ethanol to remove unreacted residues (cobalt ions). Likewise, evaporation of the solvent results in a coarse doped porous carbon material in the form of fine powder.

The present invention serves as a new active site while being doped in the form of cobalt oxide (Co ₃ O ₄ ) in a cobalt doping process. It also affects the activity by changing the nitrogen structure in the cobalt doping process. Due to the characteristics reflected in the material, the anode material of the fuel cell shows a performance equivalent to that of graphene and platinum based materials, and has a fixed capacitance of 300 F / g as a super capacitor material

In another aspect, the present invention is a porous carbonaceous material prepared according to the method, which provides a porous carbon in which nitrogen and metal are co-doped.

The carbon material of the present invention has a porous graphite structure and is simultaneously doped with nitrogen and metal.

The porous carbon material has a half wave potential of 0.825 to 0.839 V (standard hydrogen electrode standard) and a current density (0.7 V, standard hydrogen electrode standard) of about 4 mA / cm 2 when used as a fuel cell anode material Show.

When the porous material is used as a supercapacitor electrode, the capacitance may range from 100 to 300 F / g.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for illustrating the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

Example  1: Preparation of Co-doped Porous Carbon Material with Nitrogen and Cobalt

Stabilizing the PAN

A flow diagram of a method for producing a nitrogen-doped porous carbon material according to an embodiment of the present invention is shown in FIG. Polyacrylonitrile (PAN) having the following structural formula was uniformly peened without being processed, and then the temperature was raised to 280 at a heating rate of 2 / min.

[Chemical Formula 1]

The air was then continuously pumped at a flow rate of 100 ml / min while maintaining it at a constant temperature for 2 hours. After the target time has passed, the air has been poured continuously and cooled. As a result, it was confirmed that the white PAN changed to black or brown (Fig. 5 (a)). The variation of the chemical structure occurring in the stabilization process is as shown in Fig.

Mixing with potassium hydroxide

The potassium hydroxide pellets were pulverized into powders, and the stabilized PAN and potassium hydroxide powders were mixed in a mass ratio of 1: 3 (PAN: potassium hydroxide) (FIG. 5B).

Carbonated  step

The evenly mixed sample was heated to 750 at a heating rate of 5 / min, held for 1 hour, and cooled. Then, argon gas (argon gas) was continuously flowed at a flow rate of 50 ml / min. The variation of the chemical structure occurring in the carbonization process is as shown in Fig. In addition, the structure of the carbon ring containing nitrogen is also diversified, as shown in FIG.

Potassium hydroxide removal step

After the reaction was completed, 5M hydrochloric acid was used to remove residual potassium hydroxide in the sample. After the neutralization reaction of potassium hydroxide and hydrochloric acid was completed, the solution was washed several times with boiling water to remove residual potassium hydroxide and hydrochloric acid to neutralize. The finally obtained product is shown in Fig. 5 (c).

Nitrogen-doped porous carbon Cobalt acetate and  Mixing step

Based on a nitrogen-doped porous carbon material, cobalt acetate powder is mixed. The mixing ratio was 20% of cobalt acetate based on the carbon mass. (A in Fig. 7)

Impregnated  step

The mixture of the above process is put into a 20 ml vial, and water is added to make a liquid. Thereafter, the cobalt ions are effectively impregnated by sonication in a sonication apparatus for 1 hour. After impregnation, drying is carried out in a vacuum oven at 120 DEG C to evaporate water as a solvent.

Heat treatment step

After drying, the mixture powder was poured with argon gas and the temperature was raised to 800 at a rate of 5 / min. At this time, the flow rate of argon gas was maintained at 50 ml / min. After reaching the target temperature, heat treatment was performed for 1 hour.

Step of removing unreacted residue

After completion of the reaction, water and ethanol were successively filtered to remove unreacted residues such as cobalt ions remaining in the sample. The final product obtained by filtration and drying in a vacuum oven is shown in Figure 7b.

The change in the surface structure due to cobalt doping is shown in FIG.

Referring to FIG. 8, the left side shows a nitrogen doped carbon material, and the right side is a carbon material doped with cobalt. In the right picture, cobalt oxides are observed as black spots.

[Test Example]

Electrostatic Capacity and Polarization Curve Measurements: The instrument used to measure capacitance and polarization curves was the VSP model manufactured by Biologic, Inc. The electrochemical reaction was used to measure the chemical and physical properties of the material Data were obtained and analyzed to determine the electrode potential of the sample.

During the performance evaluation as a fuel cell anode, the measured reaction appears as an opening of the polarization curve by an oxygen reduction reaction (ORR). (FIG. 9) The measurement potential range was 0 to -1 V, the scanning speed was 10 mV / s, and the rotation speed of the electrode was set to 1600 RPM. In addition, the experiment was carried out on an oxygen saturation aqueous solution of 1M sodium hydroxide. As shown in FIG. 9, the nitrogen and cobalt-doped porous carbon material (denoted by PANKCo2 in FIG. 9) is a platinum-based carbonaceous material, as shown in FIG. 9, in which the current rapidly increases on the polarization curve is represented by an onset potential or a half- Showing the corresponding initiation potential. The higher the initiation potential is, the higher the activity toward the oxygen reduction reaction is, which indicates the superiority of the carbon material produced by the embodiment of the present invention. In addition, as the voltage increases, the strength of the current is higher than that of the platinum-based carbon material, which is advantageous as the anode material. In addition, it can be seen that performance is greatly improved by applying the embodiment of the present invention, as compared to the comparative example (denoted as p-PAN in FIG. 9) and the nitrogen doped carbon material (denoted as PANK2 in FIG. 9).

FIG. 10 is a graph of a cyclic voltammetry measured as a supercapacitor electrode at a measurement potential range of 0 to -1 V and a scan speed of 20 mV / s. The experiment was carried out in a 6M aqueous solution of potassium hydroxide. Since the area of the graph is proportional to the electrostatic capacity, the capacitance of the material to which the embodiment 1 (co-doped with nitrogen cobalt, denoted as PANKC _O 3) of the present invention is applied (p-PAN) (PANK3), and the results are better than those of nitrogen doped material (PANK3).

Fig. 11 is a graph showing the relationship between the amount of potassium hydroxide treated (PAN: KOH = 1: 1, the ratio of polyaniline and potassium hydroxide being 1: 1) and the amount of cobalt doping (5 wt% Co doping means doping cobalt 5 wt% Quot; Referring to FIG. 11, it can be seen that the capacitance increases with the amount of cobalt doping even when the value of potassium hydroxide is constant. Also, referring to FIG. 11, it can be confirmed that the maximum capacitance is obtained when the doping amount of cobalt is 10 wt%.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. something to do. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (21)

Stabilizing the nitrogen-containing polymer by contact with air;
Mixing the stabilized polymer with an activator;
Carbonizing the polymer mixed with the activating agent to produce a nitrogen-doped porous carbon material;
Mixing the nitrogen-doped porous carbon material with a metal salt;
Impregnating the carbonaceous material with the carbonaceous material;
And heat treating the carbonaceous material impregnated with the metal salt to form a porous carbon material. The method of claim 1, wherein the nitrogen-containing polymer is at least one selected from the group consisting of polyacrylonitrile (PAN), polyaniline (PANI), polypyrrole (PPy), and polyuronan A method for producing a porous carbon material doped with nitrogen and metal, characterized in that the porous carbon material is a polymer. The method of claim 1, wherein the method further comprises the step of performing an acid treatment after removing the unreacted residue to produce a nitrogen-doped porous carbon material. A method for producing a porous carbon material. The method of claim 1, wherein the stabilizing step comprises cyclizing the polymer by an oxidation reaction. The method of claim 1, wherein the stabilizing step is performed at a temperature ranging from 1 to 20 ° C / min and a heat treatment is performed at 250 to 300 ° C for 1 to 3 hours. 2. The method of claim 1, wherein the stabilizing step comprises supplying air at a rate of 50 to 200 ml / min. The method of claim 1, wherein the mixing ratio of the polymer and the activator is 1: 0.5 to 1: 5 by weight. 2. The method of claim 1, wherein the activator is potassium hydroxide, sodium hydroxide, H3PO4, ZnCl2. The method of claim 1, wherein the carbonization step comprises raising the temperature at a rate of 1 to 10 ° C / min under an inert gas, and maintaining the mixture at 600 to 1300 ° C for a predetermined period of time. . 2. The method of claim 1, wherein the carbonizing step is performed by heat treatment in the presence of an inert gas to bind the cyclized polymer to the graphite. 11. The method of claim 10, wherein the carbonizing step is a step of reacting the activating agent with a part of carbon forming the graphite skeleton to form porosity on the graphite. 4. The method of claim 3, wherein the acid is a strong acid selected from the group consisting of hydrochloric acid (HCl), perchloric acid (HClO4), nitric acid (HNO3), and sulfuric acid (H2SO4). 4. The method of claim 3, wherein the concentration of the acid is 0.1 to 10M. The method of claim 1, wherein the metal salt is a transition metal-based salt. 15. The method of claim 14, wherein the transition metal-based salt is selected from the group of cobalt salts, nickel salts, iron salts, and manganese salts. The method of claim 1, wherein the mixing ratio (weight) of the carbon material to the metal salt is 1: 0.05 to 1: 0.5. The method according to claim 1, wherein the impregnating step includes a step of dissolving the carbon material and a metal salt, a step of sonication, or a stirring step using a magnet rod. . 2. The method of claim 1, wherein the heat treatment step is performed at a temperature of 1 to 10 DEG C / min under an inert gas atmosphere, and then heat-treated at 800 to 900 DEG C for 1 to 3 hours to produce a porous carbon material doped with nitrogen and metal. Way. 18. A porous graphite structure produced according to any one of claims 1 to 18, wherein the nitrogen and metal are simultaneously doped to the graphite structure. The method of claim 19, wherein the carbon material has a half-wave potential of 0.825 to 0.839 V (standard hydrogen electrode standard) in an oxygen reduction reaction, a current density of 4 mA / cm 2 at 0.7 V (standard hydrogen electrode standard) Wherein the porous carbon material is a porous carbon material. The porous carbon material according to claim 19, wherein the carbon material has an electrostatic capacity of 100 to 300 F / g.

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