A method for preparing supercapacitor carbon materials by using bio-oil-derived hydrothermal carbon

Abstract

The present invention discloses a method for preparing a supercapacitor carbon material by using bio-oil-derived hydrochar, which comprises the following steps: placing bio-oil in a reaction kettle for reaction, washing and drying the solid product obtained after the reaction in sequence, and obtaining hydrochar after the drying is completed; placing the hydrochar and an activator in a beaker, adding water to the beaker; stirring by using a magnetic stirrer; after the stirring is completed, transferring it to an oven for drying to obtain a hydrochar-activator mixture; transferring the hydrochar-activator mixture to a tubular furnace and introducing an inert gas for activation reaction, and obtaining an activated product after the reaction is completed; grinding, washing and drying the activated product in sequence, and obtaining the supercapacitor carbon material after the drying is completed. The present invention can solve the problems of low carbon yield and insufficient specific surface area in the prior art when using bio-oil to prepare the supercapacitor carbon material.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitor carbon materials. Specifically, it is a method for preparing supercapacitor carbon materials by using bio-oil-derived hydrothermal carbon. Background Art

[0002] A supercapacitor, also called an electric double-layer capacitor, is a new type of environmentally friendly energy storage device between a capacitor and a battery. It has both the characteristics of capacitor charge and discharge and the energy storage characteristics of a battery, and no material changes occur during its charge and discharge process. Therefore, it has the advantages of short charging time, good temperature characteristics, long service life, etc., and is currently widely used in industries such as wearable devices and electric vehicles. Since a supercapacitor uses a double-layer structure composed of a carbon porous electrode and an electrolyte to achieve a large capacitance, the carbon material of the carbon porous electrode is the key to affecting the supercapacitor.

[0003] Patent document CN110028050A discloses a method for preparing supercapacitor carbon materials using bio-oil: first, bio-oil is prepared from dry biomass raw materials, then the bio-oil is mixed with a templating agent to obtain a mixture, then the above mixture is carbonized in a tubular furnace to obtain a carbonized product, and finally the carbonized product is ground, pickled, washed and dried to obtain supercapacitor carbon materials. This supercapacitor material has excellent electrochemical properties, but in this document, the prepared bio-oil is directly mixed with the templating agent and then carbonized in a tubular furnace. In an open space, the bio-oil is more likely to be lost in the form of volatile components after heating, resulting in a low yield of its porous carbon, only 9.79% - 17.36% [specifically refer to Table 1 in the embodiment part of patent document CN110028050A], and there is still room for improvement in the specific surface area of its porous carbon. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a method for preparing supercapacitor carbon materials by using bio-oil-derived hydrothermal carbon, so as to solve the problems of low carbon yield and insufficient specific surface area when using bio-oil to prepare supercapacitor carbon materials in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing supercapacitor carbon materials by using bio-oil-derived hydrothermal carbon, comprising the following steps:

[0007] Step (1): Place the bio-oil in a reaction kettle for reaction, and sequentially wash and dry the solid product obtained after the reaction. After drying, hydrothermal carbon is obtained;

[0008] Step (2): Place the hydrothermal carbon and the activator in a beaker, add water to the beaker, stir with a magnetic stirrer, and after stirring, transfer it to an oven for drying to obtain a hydrothermal carbon-activator mixture.

[0009] Step (3): Transfer the hydrothermal carbon-activator mixture to a tubular furnace, introduce an inert gas for activation reaction, and after the reaction ends, obtain an activated product.

[0010] Step (4): Grind, wash, and dry the activated product in sequence. After drying, the supercapacitor carbon material is obtained.

[0011] In the above method for preparing the supercapacitor carbon material using bio-oil-derived hydrothermal carbon, in step (1), the bio-oil is fast pyrolysis bio-oil produced by BTG-BTL Company in the Netherlands.

[0012] In the above method for preparing the supercapacitor carbon material using bio-oil-derived hydrothermal carbon, in step (1), the reaction temperature is 240 - 270 °C, the reaction time is 7 - 10 h, and the reaction pressure is 8.5 - 9 MPa; the atmosphere in the reaction kettle is nitrogen to protect the product from oxidation; during the reaction, the rotation speed of the reaction kettle is 280 - 400 r / min. Too low a rotation speed will cause too high a viscous force during the formation of the solid product, making it impossible to continue stirring and resulting in an insufficient reaction, thus affecting the yield of hydrothermal carbon; the solid product is washed with absolute ethanol. Since the unreacted bio-oil can dissolve in organic solvents, absolute ethanol is both economical and has a good washing effect; the drying temperature is 105 °C and the drying time is 12 h, which can not only ensure the full drying of the hydrothermal carbon but also prevent over-drying.

[0013] In the method for preparing supercapacitor carbon materials using bio-oil-derived hydrochar described above, in step (1), the reaction temperature is 250 °C, the reaction time is 8 h, and the reaction pressure is 8.9 MPa; during the reaction, the rotation speed of the reaction kettle is 300 r / min. The present invention selects 250 °C as the reaction temperature for the activation reaction. On the one hand, it is to make the reaction pressure in the reaction kettle under a nitrogen atmosphere reach the condition for the conversion of bio-oil to carbon. If too high a concentration of nitrogen is filled in the reaction kettle, the initial pressure in the reaction kettle will be very high, resulting in the inability to ensure the safety of the reaction process when the temperature rises to the reaction temperature. On the other hand, the formation of hydrochar not only requires a specific pressure but also a certain temperature to form aromatic rings. When the reaction temperature is 250 °C, the reaction pressure is 8.9 MPa, and the reaction time is 8 h, the conversion of bio-oil to hydrochar can be more complete, and a higher hydrochar yield can be obtained. In addition, it was also found in the experiment that the hydrochar prepared under this reaction condition, compared with the hydrochar prepared under other reaction conditions, not only has a higher yield during the subsequent activation reaction with the activator, but also the carbon material generated after activation has a better pore structure and a larger specific surface area.

[0014] In the method for preparing supercapacitor carbon materials using bio-oil-derived hydrochar described above, in step (2): the mass ratio of hydrochar to the activator is 1:(0.8 - 1.5). Too low a carbon-to-alkali ratio [i.e., the mass ratio of hydrochar to the activator] will result in incomplete activation, while too high a carbon-to-alkali ratio will cause the pore structure of the generated activated product to collapse, resulting in a decrease in the specific surface area of the prepared carbon material. The mass ratio of hydrochar to water is 1:(10 - 15); the speed of magnetic stirring is 200 - 300 rpm, and the stirring time is 1.5 - 3 h; the drying temperature in the oven is 65 - 75 °C, and the drying time is 8 - 12 h.

[0015] In the method for preparing supercapacitor carbon materials using bio-oil-derived hydrochar described above, in step (2): the mass ratio of hydrochar to the activator is 1:1, the mass ratio of hydrochar to water is 1:12; the speed of magnetic stirring is 200 rpm, the stirring time is 2 h; the drying temperature in the oven is 70 °C, and the drying time is 12 h; the activator is potassium hydroxide.

[0016] In the method for preparing supercapacitor carbon materials using bio-oil-derived hydrochar described above, in step (3), the flow rate of the inert gas is 450 - 550 mL / min, and it is heated to 600 - 900 °C at a heating rate of 7 - 15 °C / min, and after maintaining the temperature for 0.8 - 1.2 h, it is naturally cooled to room temperature.

[0017] In the method for preparing a supercapacitor carbon material using bio - oil - derived hydrochar described above, in step (3), the inert gas introduced is argon; the flow rate of the inert gas is 500 mL / min, the temperature is raised to 700 °C at a heating rate of 10 °C / min, and after maintaining the temperature for 1 h, it is naturally cooled to room temperature. Under these reaction conditions, a porous carbon with excellent pore structure and large specific surface area can be prepared.

[0018] In the method for preparing a supercapacitor carbon material using bio - oil - derived hydrochar described above, in step (4): The activated product is ground and passed through a 300 - mesh sieve; during washing, first, it is pickled with a 0.2 mol / L hydrochloric acid solution and stirred for 6 h, and the solid obtained after filtration is washed with deionized water until the supernatant is neutral [this can effectively remove related potassium compounds such as potassium hydroxide]; finally, it is dried at 105 °C for 12 h to obtain the supercapacitor carbon material.

[0019] In the method for preparing a supercapacitor carbon material using bio - oil - derived hydrochar described above, in step (1): The bio - oil is fast - pyrolysis bio - oil produced by BTG Company;

[0020] In step (1), the reaction temperature is 250 °C, the reaction time is 8 h, and the reaction pressure is 8.9 MPa; the atmosphere in the reaction kettle is nitrogen; the rotation speed of the reaction kettle during the reaction is 300 r / min; after the reaction, the solid product is washed with absolute ethanol; the drying temperature is 105 °C, and the drying time is 12 h;

[0021] In step (2): The mass ratio of hydrochar to the activator is 1:1, and the mass ratio of hydrochar to water is 1:12; the speed of magnetic stirring is 200 rpm, and the stirring time is 2 h; the drying temperature in the oven is 70 °C, and the drying time is 12 h; the activator is potassium hydroxide;

[0022] In step (3), the inert gas introduced is argon; the flow rate of the inert gas is 500 mL / min, the temperature is raised to 700 °C at a heating rate of 10 °C / min, and after maintaining the temperature for 1 h, it is naturally cooled to room temperature;

[0023] In step (4): The activated product is ground and passed through a 300 - mesh sieve; during washing, first, it is pickled with a 0.2 mol / L hydrochloric acid solution and stirred for 6 h, and the solid obtained after filtration is washed with deionized water until the supernatant is neutral; finally, it is dried at 105 °C for 12 h to obtain the supercapacitor carbon material.

[0024] The technical solution of the present invention has achieved the following beneficial technical effects:

[0025] 1. The method for preparing a supercapacitor carbon material using bio-oil-derived hydrochar provided by the present invention first uses bio-oil as a carbon precursor to synthesize hydrochar in a high-temperature and high-pressure autoclave; then mixes the hydrochar with KOH and performs high-temperature activation in an inert gas to obtain activated carbon; and performs pickling on it, followed by suction filtration, washing with deionized water, and drying to obtain bio-oil-based porous carbon. Compared with traditional biomass-based activated carbon, the hydrochar prepared from bio-oil contains less ash, which can effectively reduce the influence of ash on the electrode material, and the carbon structure after hydrothermal carbonization is relatively soft and is more easily eroded by the activator to form more pore structures, making the product have a higher specific capacitance and excellent rate performance; and first converting bio-oil into hydrochar and then activating the hydrochar to prepare bio-oil-based hierarchical porous carbon has a high carbon yield. The present invention prepares bio-oil-based hierarchical porous carbon with a uniform pore size distribution and excellent electrochemical performance, which can be used as a supercapacitor carbon material.

[0026] 2. The present invention prepares hierarchical porous carbon with a uniform pore size using bio-oil. Compared with traditional high-temperature carbonization, hydrothermal carbonization can be more energy-saving, has a high carbon yield, and the prepared hierarchical porous carbon material exhibits excellent electrochemical performance; using 6M KOH as the electrolyte, at a current density of 1A / g, the specific capacitance of the supercapacitor carbon material prepared by the present invention is as high as 398.7 F / g; under the condition of a large current density of 50A / g, its specific capacitance still reaches a relatively high level, showing excellent rate performance.

[0027] 3. Bio-oil has the characteristics of having too many oxygen-containing functional groups, being difficult to preserve, and being difficult to utilize. The present invention uses hydrothermal carbonization to convert liquid bio-oil into solid hydrochar, and then using the solid hydrochar to prepare a supercapacitor carbon material is innovative; during the carbonization process, the oxygen-containing functional groups of bio-oil can introduce oxygen atoms during the carbonization process to enhance its electrochemical performance.

[0028] 4. The hydrothermal carbonization method of the present invention can convert bio-oil into hydrochar, making the graphitization degree of the prepared hydrochar relatively low, which is beneficial to further modifying and optimizing the pore structure of the hydrochar. The carbon material generated by the activation reaction of the hydrochar prepared by the method of the present invention with the activator has a higher specific surface area and excellent electrochemical performance. In addition, using the hydrothermal carbonization method can avoid the loss of carbon-containing substances caused by the gasification of bio-oil during the heating process. Hydrothermal carbonization can enable carbon-containing substances to participate in a secondary reaction in a closed space, increasing the carbon yield of the prepared product. Description of the Drawings

[0029] Figure 1 Charge-discharge curve of the supercapacitor prepared in Example 1 of the present invention;

[0030] Figure 2Capacitance change diagram of the supercapacitor prepared in Example 1 of the present invention;

[0031] Figure 3a Scanning electron microscope image (30um) of the supercapacitor material prepared in Example 1 of the present invention;

[0032] Figure 3b Scanning electron microscope image (15um) of the supercapacitor material prepared in Example 1 of the present invention;

[0033] Figure 3c Scanning electron microscope image (15um) of the supercapacitor material prepared in Example 1 of the present invention;

[0034] Figure 3d Scanning electron microscope image (15um) of the supercapacitor material prepared in Example 1 of the present invention;

[0035] Figure 3e Scanning electron microscope image (15um) of the supercapacitor material prepared in Example 1 of the present invention.

[0036] Note: The discharge curve diagrams, capacitance change diagrams, and scanning electron microscope images of the supercapacitor materials prepared in other examples are similar to those in Example 1, so they are not shown here. Detailed implementation manners

[0037] Example 1

[0038] In this example, a method for preparing a supercapacitor carbon material using bio-oil-derived hydrochar includes the following steps:

[0039] Step (1): Place 60 g of bio-oil in a high-temperature and high-pressure reactor under a nitrogen atmosphere and react at a temperature of 240 °C for 10 h. During the reaction, the reaction pressure is 8.7 MPa; the rotation speed of the reactor is 350 r / min; after the reaction, the obtained solid product is washed and dried in sequence; when washing, the detergent used is anhydrous ethanol; the drying temperature is 105 °C and the drying time is 12 h; after drying, hydrochar is obtained; the bio-oil in this example is fast pyrolysis bio-oil produced by BTG-BTL Company in the Netherlands; the mass yield of hydrochar in this step is 35.7%;

[0040] Step (2): Place 5 g of hydrochar and 4 g of the activator potassium hydroxide in a beaker, and add 60 mL of deionized water to the beaker; stir using a magnetic stirrer at a magnetic stirring speed of 200 rpm for 2.5 h; after stirring, transfer it to an oven and dry at a drying temperature of 75 °C for 12 h to obtain a hydrochar-activator mixture;

[0041] Step (3): Place the hydrothermal carbon-activator mixture in a porcelain boat and transfer it to a tubular furnace. Pass inert gas argon into the furnace at a flow rate of 450 mL / min, heat it up to 600 °C at a heating rate of 8 °C / min, and keep it at a constant temperature for 1 h. After the activation reaction is completed, cool it to room temperature to obtain the activated product;

[0042] Step (4): Grind the activated product first and then pass it through a 300-mesh sieve. Then, wash it with a 0.2 mol / L hydrochloric acid solution by stirring for 6 h, and wash the solid obtained after filtration with deionized water until the supernatant is neutral; finally, dry it at 105 °C for 12 h. After drying, the supercapacitor carbon material is obtained and marked as AHBO 600 。

[0043] The yield of the supercapacitor carbon material prepared in this example reaches 27.9%; mix the AHBO 600 prepared in this example with polytetrafluoroethylene and carbon black according to a mass ratio of 8:1:1, coat it on nickel foam, and obtain a bio-oil-based electrode sheet after drying and pressing. In a 6 M KOH electrolyte, test the electrochemical performance of the bio-oil-based electrode sheet with a three-electrode system; at a current density of 1 A / g, its specific capacitance is 228.5 F / g.

[0044] From Figure 1 it can be seen that: at a current density of 1 - 5 A / g, a symmetric triangular pattern can be maintained, indicating that the capacitance is mainly based on the electric double layer capacitance; from Figure 2 it can be seen that: during the process of increasing the current density, the attenuation of the capacitance is not very obvious, indicating that the material has good stability; from Figures 3a to 3e it can be seen that: the carbon in the carbon material prepared in this example is stacked in a layered and flaky structure, and the edge of the carbon material is eroded by potassium hydroxide, and the carbon material is eroded by potassium hydroxide relatively evenly, indicating that using potassium hydroxide to activate hydrothermal carbon can make the activated carbon obtain a relatively uniform activation. The specific surface area of the supercapacitor carbon material prepared in this example is 1663.3115 m 2 / g; the average pore diameter of the hierarchical porous carbon is 2.3283 nm.

[0045] Example 2

[0046] In this example, a method for preparing a supercapacitor carbon material using bio-oil-derived hydrothermal carbon includes the following steps:

[0047] Step (1): Place 60 g of bio-oil in a high-temperature and high-pressure reactor. Under a nitrogen atmosphere, react at a temperature of 250 °C for 8 h. During the reaction, the reaction pressure is 8.9 MPa; the rotation speed of the reactor is 300 r / min; after the reaction, wash and dry the obtained solid product in sequence; when washing, use anhydrous ethanol as the detergent; the drying temperature is 105 °C and the drying time is 12 h; after drying, hydrochar is obtained; the bio-oil in this example is fast pyrolysis bio-oil, which is produced by BTG-BTL Company in the Netherlands; the mass yield of hydrochar in this step is 39.1%.

[0048] Step (2): Place 5 g of hydrochar and 5 g of the activator potassium hydroxide in a beaker, and add 60 mL of deionized water to the beaker; stir using a magnetic stirrer, with the magnetic stirring speed being 200 rpm and the stirring time being 2 h; after stirring, transfer it to an oven and dry at a drying temperature of 70 °C for 12 h to obtain a hydrochar-activator mixture.

[0049] Step (3): Put the hydrochar-activator mixture into a porcelain boat and transfer it to a tube furnace. Pass inert gas argon at a flow rate of 500 mL / min, heat it up to 700 °C at a heating rate of 10 °C / min, and keep it at a constant temperature for 1 h. After the activation reaction, cool it to room temperature to obtain an activated product.

[0050] Step (4): First grind the activated product and then pass it through a 300-mesh sieve, then wash it with 0.2 mol / L hydrochloric acid solution and stir for 6 h. Wash the obtained solid with deionized water until the supernatant is neutral; finally, dry it at 105 °C for 12 h. After drying, the supercapacitor carbon material is obtained, marked as AHBO. 700 。

[0051] The yield of the supercapacitor carbon material prepared in this example reaches 33.3%; mix the AHBO prepared in this example 700 with polytetrafluoroethylene and carbon black according to a mass ratio of 8:1:1, coat it on nickel foam, and obtain a bio-oil-based electrode sheet after drying and pressing. In a 6 M KOH electrolyte, test the electrochemical performance of this bio-oil-based electrode sheet using a three-electrode system; at a current density of 1 A / g, its specific capacitance is 398.7 F / g. The specific surface area of the supercapacitor carbon material prepared in this example is 1820.1699 m; the average pore diameter of the hierarchical porous carbon is 2.0744 nm.

[0052] Example 3

[0053] In this example, a method for preparing a supercapacitor carbon material using bio-oil-derived hydrochar includes the following steps:

[0054] Step (1): Place 60 g of bio-oil in a high-temperature and high-pressure reactor. Under a nitrogen atmosphere, react at a temperature of 250 °C for 8 h. During the reaction, the reaction pressure is 8.9 MPa; the rotation speed of the reactor is 300 r / min; after the reaction, wash and dry the obtained solid product in sequence; when washing, the detergent used is absolute ethanol; the drying temperature is 105 °C and the drying time is 12 h; after drying, hydrochar is obtained; the bio-oil in this example is fast pyrolysis bio-oil produced by BTG-BTL Company in the Netherlands; the mass yield of hydrochar in this step is 39.1%.

[0055] Step (2): Place 5 g of hydrochar and 7.5 g of the activator potassium hydroxide in a beaker, and add 70 mL of deionized water to the beaker; stir using a magnetic stirrer, the speed of magnetic stirring is 300 rpm, and the stirring time is 3 h; after stirring, transfer it to an oven and dry at a drying temperature of 65 °C for 12 h to obtain a hydrochar-activator mixture;

[0056] Step (3): Put the hydrochar-activator mixture into a porcelain boat and transfer it to a tubular furnace. Pass inert gas argon at a flow rate of 550 mL / min, heat up to 800 °C at a heating rate of 15 °C / min, and keep it at a constant temperature for 1 h. After the activation reaction, cool it to room temperature to obtain an activated product;

[0057] Step (4): First grind the activated product and then pass it through a 300-mesh sieve, then wash it with 0.2 mol / L hydrochloric acid solution and stir for 6 h. Wash the obtained solid with deionized water until the supernatant is neutral; finally, dry it at 105 °C for 12 h. After drying, supercapacitor carbon material is obtained, marked as AHBO 800 。

[0058] The yield of the supercapacitor carbon material prepared in this example reaches 29.8%; mix the AHBO prepared in this example 800 with polytetrafluoroethylene and carbon black according to a mass ratio of 8:1:1, coat it on nickel foam, and obtain a bio-oil-based electrode sheet after drying and pressing. In a 6 M KOH electrolyte, test the electrochemical performance of the bio-oil-based electrode sheet with a three-electrode system; at a current density of 1 A / g, its specific capacitance is 294.2 F / g. The specific surface area of the supercapacitor carbon material prepared in this example is 1697.2518 m; the average pore diameter of the hierarchical porous carbon is 2.1827 nm.

[0059] Example 4

[0060] In this example, a method for preparing supercapacitor carbon material using bio-oil-derived hydrochar includes the following steps:

[0061] Step (1): Place 60 g of bio-oil in a high-temperature and high-pressure reactor. Under a nitrogen atmosphere, react at a temperature of 270 °C for 7 h. During the reaction process, the reaction pressure is 8.5 MPa; the rotation speed of the reactor is 400 r / min; after the reaction, wash and dry the obtained solid product in sequence; when washing, use anhydrous ethanol as the detergent; the drying temperature is 105 °C and the drying time is 12 h; after drying, hydrochar is obtained; the bio-oil in this example is fast pyrolysis bio-oil, which is produced by BTG-BTL Company in the Netherlands; the mass yield of hydrochar in this step is 33.8%.

[0062] Step (2): Place 5 g of hydrochar and 5 g of the activator potassium hydroxide in a beaker, and add 50 mL of deionized water to the beaker; use a magnetic stirrer for stirring, the speed of magnetic stirring is 300 rpm, and the stirring time is 1.5 h; after stirring, transfer it to an oven and dry at a drying temperature of 70 °C for 12 h to obtain a hydrochar-activator mixture;

[0063] Step (3): Put the hydrochar-activator mixture into a porcelain boat and transfer it to a tubular furnace. Pass inert gas argon at a flow rate of 500 mL / min, heat it up to 900 °C at a heating rate of 10 °C / min, and keep it at a constant temperature for 1 h. After the activation reaction, cool it to room temperature to obtain an activated product;

[0064] Step (4): First grind the activated product and then pass it through a 300-mesh sieve, then wash it with 0.2 mol / L hydrochloric acid solution and stir for 6 h. Wash the obtained solid with deionized water until the supernatant is neutral; finally, dry it at 105 °C for 12 h. After drying, the supercapacitor carbon material is obtained and marked as AHBO 900 。

[0065] The yield of the supercapacitor carbon material prepared in this example reaches 28.7%; Mix AHBO 900 prepared in this example with polytetrafluoroethylene and carbon black according to a mass ratio of 8:1:1, coat it on nickel foam, and obtain a bio-oil-based electrode sheet after drying and pressing. In a 6 M KOH electrolyte, test the electrochemical performance of this bio-oil-based electrode sheet with a three-electrode system; at a current density of 1 A / g, its specific capacitance is 337.8 F / g.

[0066] The specific surface area of the supercapacitor carbon material prepared in this example is 1775.4613 m 2 / g; the average pore diameter of the hierarchical porous carbon is 2.0428 nm.

[0067] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or variations derived therefrom still fall within the protection scope of the claims of this patent application.

Claims

1. A method for preparing a supercapacitor carbon material using bio-oil-derived hydrochar, characterized in that, It includes the following steps: Step (1): Place the bio-oil in a reaction kettle for reaction. Wash and dry the solid product obtained after the reaction in sequence. After drying, hydrochar is obtained. The bio-oil is fast pyrolysis bio-oil. The reaction temperature is 240 - 270 °C, the reaction time is 7 - 10 h, and the reaction pressure is 8.5 - 9 MPa. The atmosphere in the reaction kettle is nitrogen. The rotation speed of the reaction kettle during the reaction is 280 - 400 r / min. After the reaction, wash the solid product with absolute ethanol. The drying temperature is 105 °C, and the drying time is 12 h. Step (2): Place the hydrochar and the activator in a beaker, and add water to the beaker. Stir with a magnetic stirrer. After stirring, transfer it to an oven for drying to obtain a hydrochar-activator mixture. The mass ratio of hydrochar to the activator is 1:(0.8 - 1.5), and the mass ratio of hydrochar to water is 1:(10 - 15). The stirring speed of the magnetic stirrer is 200 - 300 rpm, and the stirring time is 1.5 - 3 h. The drying temperature in the oven is 65 - 75 °C, and the drying time is 12 h. The activator is potassium hydroxide. Step (3): Transfer the hydrochar-activator mixture to a tubular furnace and introduce an inert gas for activation reaction. After the reaction, an activated product is obtained. The flow rate of the inert gas is 450 - 550 mL / min. Heat it to 600 - 900 °C at a heating rate of 7 - 15 °C / min, and keep it at a constant temperature for 0.8 - 1.2 h, then naturally cool it to room temperature. Step (4): Grind, wash and dry the activated product in sequence. After drying, the supercapacitor carbon material is obtained. After grinding the activated product, sieve it through a 300-mesh sieve. When washing, first stir with a 0.2 mol / L hydrochloric acid solution for pickling for 6 h. Wash the solid obtained after filtration with deionized water until the supernatant is neutral. Finally, dry it at 105 °C for 12 h to obtain the supercapacitor carbon material.

2. The method for preparing a supercapacitor carbon material using bio-oil-derived hydrochar according to claim 1, wherein In step (1), the reaction temperature is 250 °C, the reaction time is 8 h, and the reaction pressure is 8.9 MPa. The rotation speed of the reaction kettle during the reaction is 300 r / min.

3. The method for preparing a supercapacitor carbon material by using bio-oil-derived hydrochar according to claim 1, wherein In step (2): The mass ratio of hydrochar to the activator is 1:1, and the mass ratio of hydrochar to water is 1:

12. The stirring speed of the magnetic stirrer is 200 rpm, and the stirring time is 2 h. The drying temperature in the oven is 70 °C, and the drying time is 12 h.

4. The method for preparing a supercapacitor carbon material using bio-oil-derived hydrochar according to claim 1, characterized in that, In step (3), the introduced inert gas is argon. The flow rate of the inert gas is 500 mL / min. Heat it to 700 °C at a heating rate of 10 °C / min, and keep it at a constant temperature for 1 h, then naturally cool it to room temperature.

5. The method for preparing a supercapacitor carbon material by using bio-oil-derived hydrochar according to any one of claims 1 - 4, characterized in that In step (1), the reaction temperature is 250 °C, the reaction time is 8 h, and the reaction pressure is 8.9 MPa; the atmosphere in the reaction kettle is nitrogen; during the reaction, the rotation speed of the reaction kettle is 300 r / min; after the reaction, the solid product is washed with absolute ethanol; the drying temperature is 105 °C, and the drying time is 12 h; In step (2): the mass ratio of hydrothermal carbon to the activator is 1:1, and the mass ratio of hydrothermal carbon to water is 1:12; the speed of magnetic stirring is 200 rpm, and the stirring time is 2 h; the drying temperature in the oven is 70 °C, and the drying time is 12 h; In step (3), the inert gas introduced is argon; the flow rate of the inert gas is 500 mL / min, and it is heated to 700 °C at a heating rate of 10 °C / min, and after maintaining the temperature for 1 h, it is naturally cooled to room temperature; In step (4): the activated product is ground and sieved through a 300-mesh sieve; during washing, first, it is pickled with a 0.2 mol / L hydrochloric acid solution and stirred for 6 h, and the solid obtained after filtration is washed with deionized water until the supernatant is neutral; finally, it is dried at 105 °C for 12 h to obtain the supercapacitor carbon material.

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