Preparation method and application of thermally oxidized activated carbon for supercapacitors

Abstract

The present invention belongs to the technical field of activated carbon modification, and discloses a preparation method and application of thermally oxidized activated carbon for supercapacitors. The method comprises the following steps: subjecting the activated carbon to a thermogravimetric test in an O2 atmosphere to determine the starting temperature at which the activated carbon reacts with O2; and then subjecting the activated carbon to a thermal oxidation treatment in an O2-containing atmosphere. In the thermally oxidized activated carbon prepared by the present invention, oxygen is mainly embedded in the defect sites of the activated carbon, and the mass fraction of oxygen reaches more than 15wt%. At the same time, a large number of new pores are generated as part of the carbon atoms in the activated carbon are converted into gaseous carbon oxides, and the structure of the graphitized carbon in the activated carbon is basically not destroyed. This helps to enhance the wettability between the activated carbon electrode and the electrolyte, facilitates the transmission and expansion of the electrolyte ions, and at the same time, the newly generated pores provide more storage space for the electrolyte ions, which is conducive to obtaining high supercapacitor performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and relates to a modification technology process for activated carbon materials used to improve the electrochemical performance of supercapacitors. Background Art

[0002] Carbon materials, with their high electrical conductivity, corrosion resistance, oxidation resistance, and lightweight properties, have found widespread application in energy storage, composite materials, aerospace, electronic information, and electromagnetic compatibility. Activated carbon (AC), a carbon material, boasts a rich pore structure, large specific surface area, and strong adsorption properties, finding widespread application in supercapacitors, adsorption of harmful gases, catalyst supports, and wastewater treatment. In the supercapacitor field, AC's rich pore structure and high specific surface area facilitate the rapid diffusion and transport of electrolyte ions, resulting in excellent supercapacitor performance. Activators used to prepare activated carbon primarily include potassium hydroxide, phosphoric acid, water vapor, and carbon dioxide. However, despite their high specific surface area, the resulting activated carbon possesses very low oxygen content. The wetting effect of the electrolyte on the activated carbon material also significantly impacts supercapacitor performance. High wettability reduces the diffusion resistance of electrolyte ions, increases the contact rate between electrolyte ions and the activated carbon, and improves the utilization efficiency of the specific surface area. Oxygen-containing groups on the AC surface, such as hydroxyl (-OH), carboxyl (-COOH), and ethers (COC), can effectively improve the wettability between activated carbon and polar electrolytes, thereby achieving excellent supercapacitor performance. Chinese patent CN 111977653A discloses hydrothermal modification of activated carbon with oxidizing acids such as HNO3, H2O2, or H2SO4. The modified activated carbon exhibits significantly improved rate performance and specific capacitance for supercapacitors, and exhibits excellent cycling stability.

[0003] Although the commonly used method of modifying activated carbon with oxidizing acid can attach oxygen to activated carbon, thereby improving the ion transfer rate, the attached oxygen atoms occupy the activated carbon micropores, thereby reducing its micropore volume. In addition, the attached oxygen increases the mass of the activated carbon. These two aspects lead to a significant reduction in the specific surface area of ​​activated carbon oxidized by strong acids. Although the attached oxygen increases the wetting effect between the activated carbon and the polar electrolyte, the reduction in specific surface area is not conducive to the high capacity of supercapacitors. Therefore, it would be very meaningful to explore methods to enable activated carbon to attach oxygen while maintaining a high specific surface area. Summary of the Invention

[0004] The present invention aims to develop an activated carbon that retains a high specific surface area while adhering to oxygen, and exhibits excellent supercapacitor properties. The activated carbon is heat-treated in an O2-containing atmosphere at a specific temperature for a period of time to obtain an oxygen-rich activated carbon with a high specific surface area.

[0005] In order to achieve the above object, the first aspect of the present invention provides a method for preparing thermally oxidized activated carbon for supercapacitors, the method comprising the following steps:

[0006] (1) Perform thermogravimetric testing on activated carbon in an O2 atmosphere to determine the reaction temperature of activated carbon and O2;

[0007] (2) The activated carbon is placed in a high-temperature furnace and heated to the reaction temperature. At the same time, a small flow of O2-containing atmosphere is introduced and maintained at the reaction temperature for a period of time to obtain oxygen-rich thermally oxidized activated carbon with a high specific surface area.

[0008] The second aspect of the present invention provides thermally oxidized activated carbon for supercapacitors prepared by the above method.

[0009] The third aspect of the present invention provides the use of the thermally oxidized activated carbon material in a supercapacitor.

[0010] Through the above technical solution, the present invention has the following beneficial effects:

[0011] The thermal oxidation treatment adopted by the present invention allows a large amount of oxygen to be attached to the activated carbon without substantially changing the activated carbon skeleton structure, and the oxygen loaded by the obtained thermally oxidized activated carbon is mainly in the defect sites of the activated carbon, and the mass fraction of oxygen can reach more than 15wt%, which helps to enhance the wettability between the activated carbon electrode and the electrolyte. At the same time, compared with acidified activated carbon, thermally oxidized activated carbon has a high specific surface area. This is because as part of the carbon atoms in the thermally oxidized activated carbon is converted into gaseous carbon oxides, a large number of pores will be left in situ, while the acidified activated carbon only attaches a large amount of oxygen and no new pores are generated. In the thermally oxidized activated carbon prepared by the present invention, the distribution of the minimum pore size of the raw material disappears, while the number of individual pore sizes increases, mainly with a pore size of 0.55-1.10nm. The added new pores can increase the specific surface area of ​​the thermally oxidized activated carbon to a certain extent. The high specific surface area and good wettability can provide a large number of sites for the adsorption of electrolyte ions and help accelerate the diffusion and migration of ions, thereby obtaining excellent supercapacitor performance. The wettability and penetration of thermally oxidized activated carbon with electrolyte are greatly enhanced compared with raw activated carbon. -1 Capacity up to 370.0F g -1 , and has a high coulombic efficiency of 97.9%, and has good cycle stability. Even after 5000 charge and discharge cycles, it still maintains 95.5% of the initial capacity. In addition, the process of the present invention is simple, safe, and environmentally friendly, and has the potential for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1This is the thermogravimetric test curve of the activated carbon used in the present invention in an O2 atmosphere;

[0013] Figure 2 X-ray photoelectron spectroscopy (XPS) diagram of the thermally oxidized activated carbon prepared in Example 1 of the present invention and its raw material activated carbon;

[0014] Figure 3 (a) TEM image and (b) dark field image, (c) C element distribution map and (d) O element distribution map of the thermally oxidized activated carbon prepared in Example 1 of the present invention;

[0015] Figure 4 This is a water contact angle diagram of the thermally oxidized activated carbon film and the raw material activated carbon film prepared in Example 1 of the present invention;

[0016] Figure 5 The nitrogen isothermal adsorption and desorption curves of the thermally oxidized activated carbon and the raw activated carbon prepared in Example 1 of the present invention are shown;

[0017] Figure 6 This is a pore size distribution curve of the thermally oxidized activated carbon and the raw activated carbon prepared in Example 1 of the present invention;

[0018] Figure 7 X-ray diffraction (XRD) patterns of thermally oxidized activated carbon prepared in Example 1 of the present invention and raw material activated carbon;

[0019] Figure 8 Capacity curves of thermally oxidized activated carbon and raw material activated carbon prepared in Example 1 of the present invention at different current densities;

[0020] Figure 9 The heat-treated activated carbon prepared in Example 1 of the present invention was heated to a current density of 10.0Ag. -1 Constant current capacity curve and coulombic efficiency diagram;

[0021] Figure 10 This is the XPS graph of the acidified activated carbon prepared in Comparative Example 1 of the present invention;

[0022] Figure 11 The nitrogen isothermal adsorption and desorption curves of the acidified activated carbon prepared in Comparative Example 1 of the present invention, the raw activated carbon, and the thermally oxidized activated carbon prepared in Example 1;

[0023] Figure 12 The pore size distribution curves of the acidified activated carbon and the raw activated carbon prepared in Comparative Example 1 of the present invention are shown;

[0024] Figure 13 Capacity curves of the acidified activated carbon prepared in Comparative Example 1 of the present invention, the raw activated carbon, and the thermally oxidized activated carbon prepared in Example 1 at different current densities;

[0025] Figure 14 This is the XPS graph of the thermally reduced activated carbon prepared in Comparative Example 2 of the present invention;

[0026] Figure 15 This is a water contact angle diagram of the thermally reduced activated carbon membrane prepared in Comparative Example 2 of the present invention;

[0027] Figure 16 Capacity curves of the thermally reduced activated carbon prepared in Comparative Example 2 of the present invention, the raw activated carbon, and the thermally oxidized activated carbon prepared in Example 1 at different current densities;

[0028] Figure 17 The nitrogen isothermal adsorption and desorption curves of the thermally oxidized activated carbon prepared in Comparative Example 3 of the present invention (thermal oxidation for 6 hours), the raw material activated carbon, and the thermally oxidized activated carbon prepared in Example 1 are shown;

[0029] Figure 18 The pore size distribution curves of the thermally oxidized activated carbon (thermal oxidation for 6 hours) and the raw activated carbon prepared in Comparative Example 3 of the present invention are shown;

[0030] Figure 19 The XPS graphs of the thermally oxidized activated carbon prepared in Comparative Example 3 of the present invention (thermal oxidation for 6 hours) and the thermally oxidized activated carbon prepared in Example 1;

[0031] Figure 20 Capacity curves of the thermally oxidized activated carbon prepared in Comparative Example 3 of the present invention (thermal oxidation for 6 hours) and the thermally oxidized activated carbon prepared in Example 1 at different current densities;

[0032] Figure 21 These are the Raman shift patterns of the thermally oxidized activated carbon prepared in Comparative Example 3 of the present invention (thermal oxidation for 6 hours), the raw material activated carbon, and the thermally oxidized activated carbon prepared in Example 1. DETAILED DESCRIPTION

[0033] The specific content of the present invention is further illustrated by the following examples.

[0034] This embodiment provides a method for preparing thermally oxidized activated carbon for supercapacitors, the method comprising the following steps:

[0035] The activated carbon is subjected to thermogravimetric testing in an O2 atmosphere at a certain heating rate to determine the reaction temperature of the activated carbon and O2; then the activated carbon is placed in a high-temperature furnace and heated to the reaction temperature at a certain heating rate, while a small flow of O2-containing atmosphere is introduced and maintained at the reaction temperature for a period of time, so that oxygen adheres to the defect sites of the activated carbon. At the same time, as some carbon atoms in the activated carbon are converted into gaseous carbon oxides, a large number of new pores are generated, thereby producing oxygen-rich thermally oxidized activated carbon with a high specific surface area.

[0036] The key to the present invention is to determine the temperature at which activated carbon can react with O2, and then control the activated carbon to react slowly with O2 through heat treatment temperature, time and atmosphere flow, so that oxygen is attached to the defect sites of the activated carbon, and part of the carbon is converted into gaseous carbon oxides to generate new pores.

[0037] In the present invention, the atmosphere of the thermogravimetric test is O2, and the heating rate is 5℃min -1 ; 1~10℃min -1 The temperature is raised to the reaction temperature at a rate of 50°C or higher, the reaction temperature being the initial reaction temperature and not more than 50°C. The initial reaction temperature refers to the temperature at which the activated carbon initially loses weight. The reaction temperature described herein is determined by the physical properties of the activated carbon material and is based on the reaction temperature obtained by thermogravimetric testing. The set temperature ensures that the activated carbon reacts with O2 while limiting and controlling the reaction rate.

[0038] The O2-containing atmosphere described in the present invention is primarily intended to achieve a lower O2 concentration than an air atmosphere, and includes air, a mixture of air and an inert atmosphere, and a mixture of O2 and an inert atmosphere. The inert atmosphere is nitrogen and argon. Since a pure O2 atmosphere can easily lead to excessively high O2 concentrations in some areas during the thermal oxidation process, resulting in significant differences in the reaction rates between the thermally oxidized activated carbon and O2, it is not within the scope of the O2-containing atmosphere described in the present invention. The O2-containing atmosphere described in the present invention preferably has an O2 content of 8-21 vol% in order to control the reaction rate and uniformity.

[0039] The small flow rate mentioned in the present invention is related to the quality of the activated carbon. 5-15 mL min is required for each gram of activated carbon. -1 O2-containing atmosphere; preferably a small flow rate of 1.6 to 2.4 mL min -1 , is the flow rate when the activated carbon raw material is 0.2g, which is intended to limit and control the amount of O2 in the O2-containing atmosphere, thereby controlling the reaction rate of activated carbon and O2.

[0040] The maintenance period of time described in the present invention is 1 to 4 hours. If the time is too short, the amount of attached oxygen will be insufficient. If the time is too long, the structure of the graphitized carbon in the activated carbon will be easily destroyed. At the same time, the carbon atoms in the carbon walls between the micropores in the activated carbon will react with O2 and be converted into gaseous carbon oxides, resulting in the disappearance of a large number of carbon walls between the micropores and the merger of a large number of micropores, thereby greatly reducing the specific surface area of ​​the thermally oxidized activated carbon.

[0041] The high-temperature furnace described in the present invention includes a tube furnace, a muffle furnace, and similar equipment. The preparation of thermally oxidized activated carbon for supercapacitors using a large high-temperature furnace according to the present invention also falls within the scope of protection of the present invention.

[0042] The following examples will be used to describe this embodiment in detail.

[0043] Example 1:

[0044] This example prepares a method for preparing thermally oxidized activated carbon for supercapacitors and conducts electrochemical performance tests:

[0045] (1) Activated carbon (JCAC-3000, Nanjing Jicang Nanotechnology Co., Ltd., Nanjing, China) was heated in an O2 atmosphere at 5 °C min -1 Thermogravimetric test was carried out at a heating rate of 1000 nm, and the starting temperature of the reaction between activated carbon and O2 was determined by the thermogravimetric test curve;

[0046] (2) The above 0.2 g activated carbon was heated in an O2 atmosphere at 5 °C min -1 The temperature was raised to 365 °C in a tube furnace at a heating rate of 1:1. The gas introduced was a mixture of air and nitrogen at a flow rate of 2 mL min -1 About, maintain at 365℃ for 3h, take out after natural cooling, and obtain thermally oxidized activated carbon;

[0047] Electrochemical performance testing: 5.0 mg of thermally oxidized activated carbon and 1.0 mg of carbon black (XF115, Nanjing Xianfeng Nanotechnology Co., Ltd., Nanjing, China) were weighed, and 20 μL of Nafion solution (5 wt%, Aldrich Reagent Inc., USA) and 480 μL of ethanol (analytical grade, Sinopharm Reagent, China) were added and mixed thoroughly by ultrasonic dispersion. 10 μL of the mixture was then applied to a 0.5 cm diameter glassy carbon electrode. Electrochemical testing was performed using a three-electrode system with a carbon rod as the counter electrode, a Hg / HgO electrode as the reference electrode, and 6 M KOH as the electrolyte. The test voltage range was -1.0 V to 0 V.

[0048] Example 2

[0049] Same as Example 1, except that the gas introduced was a mixed gas of O2 and nitrogen with an O2 content of 8 vol%, and the maintenance time was 4 h.

[0050] Example 3

[0051] Same as Example 1, except that the heat-inlet gas was changed to air with a flow rate of 2.0 mL min -1 About, maintaining time is 1h.

[0052] Comparative Example 1:

[0053] (1) 0.2 g of activated carbon (JCAC-3000, Nanjing Jicang Nanotechnology Co., Ltd., Nanjing, China) was added to a 100 mL round-bottom flask, and 60 mL of 30% HNO3 solution was added. After stirring for 30 min, the mixture was heated at 90 °C and refluxed for 6 h.

[0054] (2) washing the acid-treated activated carbon with water several times until the pH value of the washing solution reaches 7, and then freeze-drying to obtain acidified activated carbon;

[0055] The electrochemical performance test was the same as that in Example 1.

[0056] Comparative Example 2:

[0057] Same as Example 1, except that the heat treatment atmosphere is inert gas nitrogen, the heat treatment temperature is 1000° C., and the heat treatment time is 2 h.

[0058] Comparative Example 3:

[0059] The method of Example 1 was followed, except that the heat treatment time of the activated carbon in the tube furnace was changed to 6 h.

[0060] Figure 1 This is a thermogravimetric test curve of the activated carbon raw material used in Example 1 of the present invention. It can be seen from the figure that the temperature at which the raw activated carbon starts to react with O2 is about 362°C.

[0061] Figure 2 XPS spectra of the thermally oxidized activated carbon prepared in Example 1 and its raw material activated carbon show a peak at 285.0 eV attributed to C1s. The peak around 533.0 eV corresponds to O1s. Calculated oxygen contents in the thermally oxidized activated carbon and the raw material activated carbon are 15.7 wt% and 10.5 wt%, respectively.

[0062] Figure 3 (a) TEM image and (b) dark field image, (c) C element distribution map and (d) O element distribution map of the thermally oxidized activated carbon prepared in Example 1 of the present invention. Figure 3 d It can be seen that a large amount of oxygen elements are uniformly distributed on the surface of the thermally oxidized activated carbon, which further proves that a large amount of oxygen is attached to its surface.

[0063] Figure 4 The water contact angles of the thermally oxidized activated carbon membrane and the raw activated carbon membrane prepared in Example 1 of the present invention are shown. The test sample is a rolled film approximately 0.6 mm thick, composed of an active material, acetylene black (Li-2060, Tianjin Annohe New Energy Technology Co., Ltd.), and polytetrafluoroethylene (PTFE, 60 wt% aqueous dispersion, Aladdin Reagent Company) in a mass ratio of 8:1:1. The test shows that the water contact angle of the activated carbon membrane is approximately 120.0°, while the water contact angle of the thermally oxidized AC is 106.0°, indicating that the wettability and penetration of the thermally oxidized activated carbon with the electrolyte are significantly enhanced compared to the raw activated carbon.

[0064] Figure 5The nitrogen isothermal adsorption and desorption curves of the thermally oxidized activated carbon and the raw activated carbon prepared in Example 1 of the present invention are shown in the figure. The test shows that the specific surface areas of the thermally oxidized activated carbon and the raw activated carbon are 3260.4 and 3642.4 m 2 g -1 The specific surface area of ​​thermally oxidized activated carbon is smaller than that of raw activated carbon. The decrease in the specific surface area of ​​thermally oxidized activated carbon is mainly attributed to the following three aspects: on the one hand, the oxygen attached to the thermally oxidized activated carbon increases its mass; on the other hand, the oxygen attached during the thermal oxidation process occupies the space of micropores; and the newly generated pores lead to the interconnection of micropores, making some pores larger, such as Figure 6 As shown in FIG, from the pore size distribution curves of thermally oxidized activated carbon and raw activated carbon, it can be seen that the pore size distribution of thermally oxidized activated carbon at 0.59 nm increases significantly, while the pore size distribution at 0.50 nm disappears.

[0065] Figure 7 XRD patterns of thermally oxidized activated carbon and raw activated carbon prepared in Example 1 of the present invention. The two broad diffraction peaks in the figure indicate the amorphous carbon structure of the thermally oxidized activated carbon and the raw activated carbon. The peaks near 2θ=21.3° and 42.6° correspond to the (002) and (101) crystal planes of mixed-layer graphite, respectively. The interlayer spacing calculated from the center position of the (002) peak is 0.417nm, which is larger than the interlayer spacing of natural graphite (0.335nm). This is due to the disordered superposition of graphitized carbon and mixed-layer graphite. The peak positions of the thermally oxidized activated carbon and the raw activated carbon are basically the same, which indicates that thermal oxidation has basically not changed the carbon skeleton structure of the activated carbon.

[0066] Figure 8 The capacity curves of thermally oxidized activated carbon and raw activated carbon prepared in Example 1 of the present invention at different current densities are shown in the figure. As can be seen from the figure, the capacity of thermally oxidized activated carbon is significantly higher than that of raw activated carbon. The current density is 1.0Ag -1 When the specific capacities of thermally oxidized activated carbon and raw activated carbon are 420.0 and 287.0 F g, respectively -1 This is mainly attributed to the fact that the anchored oxygen increases the wettability between the thermally oxidized activated carbon electrode and the electrolyte.

[0067] Figure 9 The thermally oxidized activated carbon prepared in Example 1 of the present invention was -1 The constant current capacity curve and coulomb efficiency diagram of thermal oxidation activated carbon are shown in the figure. -1 Capacity up to 370.0F g -1 , and has a high coulombic efficiency, maintained at 97.9%, and good cycle stability. Even after 5000 charge and discharge cycles, it still maintains 95.5% of the initial capacity.

[0068] Figure 10 This is the XPS graph of the acidified activated carbon prepared in Comparative Example 1 of the present invention. As can be seen from the figure, after nitric acid oxidation, the oxygen content of the acidified activated carbon reaches 18.3wt%. However, its specific surface area has been greatly reduced, as shown in FIG. Figure 11 As shown in the figure, the specific surface area of ​​acidified activated carbon is 2318.8m 2 g -1 , which is significantly smaller than that of raw activated carbon and thermally oxidized activated carbon. This is mainly due to the following two reasons: on the one hand, the oxygen attached to the acidified activated carbon increases its mass; on the other hand, the attached oxygen occupies the space of the micropores. Since no new pores are generated and the attached oxygen increases the mass of the acidified activated carbon, its different pore size distributions are all reduced to a certain extent compared with the raw activated carbon, such as Figure 12 As shown, the specific surface area of ​​acidified activated carbon is significantly smaller than that of thermally oxidized activated carbon.

[0069] Figure 13 The following graph shows the capacity curves of the acidified activated carbon prepared in Comparative Example 1, the raw activated carbon, and the thermally oxidized activated carbon prepared in Example 1 at different current densities. As can be seen from the graph, the capacity of the thermally oxidized activated carbon is significantly higher than that of the acidified activated carbon and the raw activated carbon. This is likely due to the synergistic effect of the thermally oxidized activated carbon's high specific surface area and good wettability.

[0070] Figure 14 This is the XPS graph of the thermally reduced activated carbon prepared in comparative example 2 of the present invention. As can be seen from the figure, the oxygen content of the thermally reduced activated carbon has been greatly reduced. This also leads to an increase in the water contact angle of the thermally reduced activated carbon film to 140.3°, as shown in FIG. Figure 15 shown.

[0071] Figure 16 The following graph shows the capacity curves of the thermally reduced activated carbon prepared in Comparative Example 2, the raw activated carbon, and the thermally oxidized activated carbon prepared in Example 1 at different current densities. As can be seen from the graph, the capacity of the thermally reduced activated carbon is lower, demonstrating the significant influence of the wetting effect between the electrode and the electrolyte on its capacitance performance.

[0072] Figure 17 The nitrogen isothermal adsorption and desorption curves of the thermally oxidized activated carbon prepared in Comparative Example 3 of the present invention (thermal oxidation for 6 hours), the raw material activated carbon, and the thermally oxidized activated carbon prepared in Example 1 are shown in the figure. As can be seen from the figure, when the thermal oxidation time is increased to 6 hours, the specific surface area decreases significantly. This is mainly because as time goes by, pores merge, resulting in the disappearance of some smaller micropores and the increase of larger micropores. Figure 18 shown.

[0073] Figure 19The XPS curves of the thermally oxidized activated carbon prepared in Comparative Example 3 (thermal oxidation for 6 hours) and the thermally oxidized activated carbon prepared in Example 1 are shown. As can be seen from the figure, after increasing the thermal oxidation time to 6 hours, the oxygen content of the thermally oxidized activated carbon prepared (thermal oxidation for 6 hours) only increases from 15.7wt% of the thermally oxidized activated carbon to 16.4wt%, a relatively small increase.

[0074] Figure 20 The capacity curves of the thermally oxidized activated carbon prepared in Comparative Example 3 (thermal oxidation for 6 hours) and the thermally oxidized activated carbon prepared in Example 1 at different current densities are shown. As can be seen from the figure, the capacity of the thermally oxidized activated carbon (thermal oxidation for 6 hours) is significantly lower than that of the thermally oxidized activated carbon, which is mainly attributed to the higher specific surface area of ​​the thermally oxidized activated carbon.

[0075] Figure 21 The Raman shift diagram of the thermally oxidized activated carbon (thermal oxidation for 6 hours) prepared in Comparative Example 3 of the present invention, the raw material activated carbon, and the thermally oxidized activated carbon prepared in Example 1. As can be seen from the figure, the thermally oxidized activated carbon and the activated carbon raw material in Example 1 have the same Raman shift diagram. D / I G The values ​​are all 0.94, which indicates that the oxygen attached to the thermally oxidized activated carbon is mainly combined with the defective carbon, and the I D / I G The value is 0.97, which has increased significantly, indicating that when the thermal oxidation time is increased to 6h, the structure of graphitized carbon in activated carbon is destroyed to a certain extent.

Claims

1. A method for preparing thermally oxidized activated carbon for supercapacitors, characterized in that: The method comprises the following steps: (1) Determine the starting temperature of the reaction between activated carbon and O2: Perform thermogravimetric testing on the activated carbon in an O2 atmosphere, and determine the initial temperature of the reaction between activated carbon and O2 through the thermogravimetric test curve; (2) Preparation of thermally oxidized activated carbon: The activated carbon raw material is placed in a high-temperature furnace, and the temperature is raised to the reaction temperature at a certain heating rate. At the same time, a small flow of O2-containing atmosphere is introduced, and the temperature is maintained at the reaction temperature for a period of time to obtain oxygen-rich thermally oxidized activated carbon with a high specific surface area; the O2-containing atmosphere is an O2-containing atmosphere with an O2 content of 8-21 vol%; the small flow rate is related to the mass of the activated carbon, and 5-15 mL min is introduced per gram of activated carbon. -1 The O2-containing atmosphere; the maintaining period is 1 to 4 hours; the reaction temperature is the initial reaction temperature and is at most 50°C above, the initial reaction temperature refers to the initial weight loss temperature of the activated carbon; Thermally oxidized activated carbon allows a large amount of oxygen to be attached to the activated carbon without substantially changing the activated carbon skeleton structure. The oxygen loaded on the obtained thermally oxidized activated carbon is mainly located at the defect sites of the activated carbon, and the mass fraction of oxygen reaches more than 15.0 wt%.

2. The method for preparing thermally oxidized activated carbon for supercapacitors according to claim 1, wherein: The O2-containing atmosphere includes air, a mixture of air and an inert atmosphere, and a mixture of O2 and an inert atmosphere. The inert atmosphere is nitrogen and argon.

3. The method for preparing thermally oxidized activated carbon for supercapacitors according to claim 1, wherein: The heating rate is 1-10°C min -1 .

4. The method for preparing thermally oxidized activated carbon for supercapacitors according to claim 1, wherein: The high temperature furnace includes a tube furnace and a muffle furnace.

5. A thermally oxidized activated carbon, characterized in that The method is prepared by any one of claims 1 to 4.

6. The use of the thermally oxidized activated carbon according to claim 5 in supercapacitors, characterized in that: The electrode prepared by thermal oxidation activated carbon was -1 Capacity up to 370.0 F g -1 , and the coulombic efficiency remained at 97.9%. After 5000 charge and discharge cycles, it still maintained 95.5% of the initial capacity.

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