A method for preparing a capacitive graphene
Using litchi tree trunks as raw material, capacitor graphene was prepared by high-temperature carbonization, pore formation, acidification, and ultrasonic exfoliation. This method solved the problem of large-scale production of high-performance capacitor graphene and achieved excellent cycle performance and low-cost preparation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 深圳材启新材料有限公司
- Filing Date
- 2022-11-09
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies make it difficult to mass-produce high-performance graphene, especially since methods for preparing high-performance capacitor graphene are not yet mature, and traditional methods suffer from environmental pollution and high preparation costs.
Capacitor graphene was prepared using litchi tree trunks as raw materials through four steps: high-temperature carbonization, pore formation, acidification, and ultrasonic exfoliation. The specific steps include high-temperature carbonization reaction, pore formation reaction with the addition of potassium hydroxide and calcium hydroxide as pore-forming agents, acidification treatment, and ultrasonic exfoliation.
The prepared capacitive graphene exhibits excellent cycle performance and high specific capacitance as an electrode material for supercapacitors. The method is safe, environmentally friendly, easy to operate, and readily applicable to industrial production.
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Figure CN115579250B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of capacitive graphene preparation, and particularly relates to a preparation method of capacitive graphene. BACKGROUND
[0002] Graphene was discovered in 2004, and the discoverer of graphene won the Nobel Prize in 2010. Graphene has received very wide attention due to its extremely excellent electrical properties. For example, the carrier transport behavior of graphene is similar to that of neutrinos in relativity, quantum Hall effect can be observed at room temperature, and two-pole field effect, etc. In addition, the unique physical and mechanical properties of graphene further broaden the application space of graphene: graphene has a large theoretical specific surface area (2630 m 2 g -1 ), high carrier mobility (2×10 5 cm 2 v - 1 s -1 ), high Young's modulus (~1.0TPa), high thermal conductivity (~5000Wm -1 K -1 ), high light transmittance (97.7%) and high electrical conductivity (>6×10 6 S / m). In the near future, graphene can be used to prepare new generation electronic elements or electronic transistors that are thinner and faster in conductive speed. Moreover, due to the good light transmittance and electrical conductivity of graphene, graphene is also suitable for replacing ITO to manufacture transparent touch screens, light panels and even solar cells. The good mechanical properties of graphene have been applied to thermal shrinkage materials or film materials to improve the tensile strength. Since graphene is considered to be the hardest material ever discovered, some researchers have been developing bulletproof vests made of graphene. Such bulletproof vests are lighter and thinner, which will greatly reduce the load of soldiers. The extremely high theoretical surface area of graphene makes it suitable for application in the field of catalysis as a carrier material for catalysts. In addition, the extremely high electrical conductivity of graphene can promote the transfer of photoelectrons, improve the exciton lifetime and improve the photocatalytic efficiency, and thus graphene is applied in the field of photocatalysis.
[0003] The demand for graphene will also continue to increase as its application fields expand, so a means for cheap and large-scale synthesis of graphene is necessary. Graphene materials can be divided into two categories: powder graphene and thin film graphene, and for different application fields, powder graphene is widely used in the fields of energy, corrosion prevention, reinforcement, heat dissipation, etc., so the research on the preparation method is the most extensive and diverse. The preparation methods of graphene mainly include mechanical exfoliation method, chemical vapor deposition method, SiC epitaxial growth method, oxidation-reduction method and liquid phase exfoliation method. Among them, the chemical vapor deposition method, the SiC epitaxial growth method and the mechanical exfoliation method are complicated to operate, have low yield and high preparation cost, and cannot realize large-scale production of graphene. The oxidation-reduction method can produce graphene in large quantities, but it produces a lot of harmful gases and a large amount of corrosive waste liquid in the process of producing graphene, which is easy to cause environmental pollution, and the synthesized graphene contains a large number of structural defects, which seriously limits its wide application. The graphene prepared by the liquid phase exfoliation method has fewer structural defects and lower oxygen content, but the liquid phase exfoliation method is often affected by poor exfoliation efficiency and low graphene concentration (usually <0.1 mg / mL).
[0004] Litchi tree trunk is rich in resources and low in raw material cost; however, there is no report on preparing capacitive graphene from litchi tree trunk, especially on preparing high-performance capacitive graphene. Therefore, it is of important application value to develop a method for preparing capacitive graphene from litchi tree trunk, especially to prepare high-performance capacitive graphene. SUMMARY
[0005] In order to overcome at least one of the technical problems existing in the prior art, the present application provides a preparation method of capacitive graphene.
[0006] The above technical problems to be solved by the present application are solved by the following technical solutions:
[0007] A preparation method of capacitive graphene, comprising the following steps:
[0008] (1) crushing litchi tree trunk and then performing high-temperature carbonization reaction to obtain carbonized litchi tree trunk powder;
[0009] (2) performing pore-forming reaction on the carbonized litchi tree trunk powder to obtain mesoporous carbon;
[0010] (3) performing acidification treatment on the mesoporous carbon to obtain acidified mesoporous carbon;
[0011] (4) performing ultrasonic exfoliation on the acidified mesoporous carbon to obtain the capacitive graphene.
[0012] The application first provides a method for preparing capacitive graphene by using litchi trunk as raw material. The inventors surprisingly find that the capacitive graphene prepared by the following four steps, i.e. high-temperature carbonization reaction, pore-forming reaction, acidification treatment and ultrasonic stripping, has high mass specific capacitance and cycle stability when used as supercapacitor electrode material. The specific experimental study shows that when used as supercapacitor electrode material, the capacitive graphene has high mass specific capacitance in aqueous electrolyte, and the specific capacitance does not show obvious attenuation after 30000 cycles, and the cycle performance is excellent.
[0013] In addition, the inventors need to emphasize that the above four reaction steps are very critical and indispensable, and the capacitive graphene prepared by lacking any one step does not have excellent cycle performance when used as supercapacitor electrode material. Only the capacitive graphene prepared by the four steps of high-temperature carbonization reaction, pore-forming reaction, acidification treatment and ultrasonic stripping using litchi trunk as raw material has excellent cycle performance when used as supercapacitor electrode material.
[0014] Preferably, the high-temperature carbonization reaction in step (1) is specifically carried out at 400-600℃ in a nitrogen atmosphere for 2-6h.
[0015] Preferably, the pore-forming reaction in step (2) is specifically carried out by adding a pore-forming agent to the carbonized litchi trunk powder and carrying out high-temperature pore-forming reaction at 800-1000℃ in a nitrogen atmosphere for 2-8h.
[0016] Preferably, the pore-forming agent in step (2) is composed of potassium hydroxide and calcium hydroxide.
[0017] The inventors find in the research that in the process of preparing capacitive graphene by using the method of the application, the selection of pore-forming agent plays an important role in whether the prepared capacitive graphene has excellent cycle performance when used as supercapacitor electrode material. The inventors surprisingly find that when the pore-forming agent is a combined pore-forming agent composed of potassium hydroxide and calcium hydroxide, the prepared capacitive graphene has excellent cycle performance when used as supercapacitor electrode material; the cycle performance is much higher than that of the capacitive graphene prepared by using potassium hydroxide or calcium hydroxide alone as pore-forming agent. When potassium hydroxide and calcium hydroxide are simultaneously used as pore-forming agent, the cycle performance of the prepared capacitive graphene used as supercapacitor electrode material can be synergistically improved.
[0018] Preferably, the mass ratio of potassium hydroxide to calcium hydroxide is 1:1-1:0.1.
[0019] Preferably, the ratio of pore-forming agent to carbonized litchi trunk powder is 30-60g: 10-15g.
[0020] More preferably, the high-temperature carbonization reaction in step (1) specifically involves: first, conducting a high-temperature pore-forming reaction at 350-400°C in a nitrogen atmosphere for 1-2 hours; then, conducting a high-temperature pore-forming reaction at 700-800°C in a nitrogen atmosphere for 1-2 hours; and finally, conducting a high-temperature pore-forming reaction at 900-1000°C for 1-2 hours.
[0021] The inventors were surprised to find in numerous experiments that when the pore-forming agent was a combination of potassium hydroxide and calcium hydroxide, the capacitor graphene prepared under the three-step high-temperature pore-forming reaction conditions described above in this invention exhibited significantly improved cycle performance when used as an electrode material for supercapacitors.
[0022] The inventors would like to further emphasize that only graphene prepared under the above three-step high-temperature pore-forming reaction can significantly improve its cycle performance when used as an electrode material for supercapacitors; graphene prepared under the other three-step high-temperature pore-forming reaction, or graphene prepared under the other two-step high-temperature pore-forming reaction, cannot significantly improve its cycle performance when used as an electrode material for supercapacitors.
[0023] Preferably, the acidification treatment in step (3) specifically includes:
[0024] Mesoporous carbon is acidified using 98% sulfuric acid at 60–90°C; the ratio of sulfuric acid to carbonized litchi trunk powder is 20–60 mL: 10–15 g.
[0025] Preferably, the specific method of ultrasonic stripping in step (4) is as follows: acidified mesoporous carbon is dispersed in ultrasonic liquid and then ultrasonically treated for 1 to 12 hours.
[0026] Preferably, the ultrasonic fluid is selected from one or a mixture of two or more of water, N-methylpyrrolidone, N,N-dimethylformamide, and ethanol.
[0027] Preferably, the ratio of ultrasonic liquid to carbonized litchi trunk powder is 50-60 mL: 10-15 g.
[0028] Beneficial Effects: This invention provides a novel method for preparing capacitive graphene using litchi tree trunks as raw material. The method involves four steps: high-temperature carbonization of litchi tree trunk powder, followed by a pore-forming reaction, acidification treatment, and finally ultrasonic exfoliation. The resulting capacitive graphene exhibits high specific capacitance and cycle stability when used as an electrode material for supercapacitors. Furthermore, the method described in this invention is safe, environmentally friendly, simple to operate, low in preparation cost, and easy to industrialize. Attached Figure Description
[0029] Figure 1 This is an appearance diagram of the capacitor graphene powder prepared in Example 1 of the present invention.
[0030] Figure 2 This is a transmission electron microscope image of the capacitive graphene prepared in Example 1 of the present invention. Detailed Implementation
[0031] The present invention will be further explained below with reference to specific embodiments, but the embodiments do not limit the present invention in any way.
[0032] Example 1
[0033] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a pulverizer, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to obtain carbonized lychee tree trunk powder.
[0034] (2) Add 10g of carbonized litchi trunk powder, 15g of potassium hydroxide and 15g of calcium hydroxide pore-forming agent to an alumina crucible, and carry out a high-temperature pore-forming reaction at 900℃ in a nitrogen atmosphere for 3h. Then soak in 1mol / L hydrochloric acid for 2h, and then filter, wash with water and dry to obtain mesoporous carbon.
[0035] (3) Acidified mesoporous carbon was obtained by acidifying the mesoporous carbon with 20 mL of 98% sulfuric acid at 80℃, followed by filtration, washing with water and drying.
[0036] (4) Disperse acidified mesoporous carbon in 50 mL of water, then sonicate for 5 h, filter and dry to obtain capacitor graphene.
[0037] Example 2
[0038] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a crusher, dried in a 120℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 500℃ in a nitrogen atmosphere for 5 hours to carbonize the lychee tree trunk powder.
[0039] (2) Add 15g of carbonized litchi trunk powder, 40g of potassium hydroxide and 20g of calcium hydroxide pore-forming agent to an alumina crucible, carry out a high-temperature pore-forming reaction at 1000℃ in a nitrogen atmosphere for 6h, then soak in 0.5mol / L hydrochloric acid for 3h, and then filter, wash with water and dry to obtain mesoporous carbon.
[0040] (3) Acidified mesoporous carbon was obtained by acidifying the mesoporous carbon with 30 mL of 98% sulfuric acid at 90℃, followed by filtration, washing with water and drying.
[0041] (4) Disperse acidified mesoporous carbon in 60 mL of water, then sonicate for 6 h, filter and dry to obtain capacitor graphene.
[0042] Example 3
[0043] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a pulverizer, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to obtain carbonized lychee tree trunk powder.
[0044] (2) Add 10g of carbonized litchi trunk powder, 15g of potassium hydroxide and 15g of calcium hydroxide pore-forming agent to an alumina crucible. First, carry out a high-temperature pore-forming reaction at 350℃ in a nitrogen atmosphere for 1h; then carry out a high-temperature pore-forming reaction at 800℃ in a nitrogen atmosphere for 1h; finally, carry out a high-temperature pore-forming reaction at 900℃ for 1h, then soak in 1mol / L hydrochloric acid for 2h, and then filter, wash with water and dry to obtain mesoporous carbon.
[0045] (3) Acidified mesoporous carbon was obtained by acidifying the mesoporous carbon with 20 mL of 98% sulfuric acid at 80℃, followed by filtration, washing with water and drying.
[0046] (4) Disperse acidified mesoporous carbon in 50 mL of water, then sonicate for 5 h, filter and dry to obtain capacitor graphene.
[0047] The difference between Example 3 and Example 1 is that Example 3 prepares capacitor graphene under a three-step high-temperature pore-forming reaction, while Example 1 prepares capacitor graphene under a single-step high-temperature pore-forming reaction.
[0048] Comparative Example 1
[0049] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a pulverizer, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to obtain carbonized lychee tree trunk powder.
[0050] The difference between Comparative Example 1 and Example 1 is that only carbonized litchi trunk powder was prepared in Comparative Example 1, while capacitor graphene was prepared in Example 1.
[0051] Comparative Example 2
[0052] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a crusher, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to carbonize the lychee tree trunk powder.
[0053] (2) Add 10g of carbonized litchi trunk powder, 15g of potassium hydroxide and 15g of calcium hydroxide pore-forming agent to an alumina crucible, and carry out a high-temperature pore-forming reaction at 900℃ in a nitrogen atmosphere for 3h. Then soak in 1mol / L hydrochloric acid for 2h, and then filter, wash with water and dry to obtain mesoporous carbon.
[0054] The difference between Comparative Example 2 and Example 1 is that only mesoporous carbon was prepared in Comparative Example 2, while capacitor graphene was prepared in Example 1.
[0055] Comparative Example 3
[0056] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a pulverizer, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to obtain carbonized lychee tree trunk powder.
[0057] (2) Add 10g of carbonized litchi trunk powder, 15g of potassium hydroxide and 15g of calcium hydroxide pore-forming agent to an alumina crucible, and carry out a high-temperature pore-forming reaction at 900℃ in a nitrogen atmosphere for 3h. Then soak in 1mol / L hydrochloric acid for 2h, and then filter, wash with water and dry to obtain mesoporous carbon.
[0058] (3) Acidified mesoporous carbon was obtained by acidifying the mesoporous carbon with 20 mL of 98% sulfuric acid at 80℃, filtering, washing with water and drying.
[0059] The difference between Comparative Example 3 and Example 1 is that only acidified mesoporous carbon was prepared in Comparative Example 3, while capacitor graphene was prepared in Example 1.
[0060] Comparative Example 4
[0061] (1) The lychee tree trunks were crushed into particles with a diameter of 10-20 micrometers by a crusher, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours.
[0062] (2) Add 10g of carbonized litchi trunk powder, 15g of potassium hydroxide and 15g of calcium hydroxide pore-forming agent to an alumina crucible, and carry out a high-temperature pore-forming reaction at 900℃ in a nitrogen atmosphere for 3h. Then soak in 1mol / L hydrochloric acid for 2h, and then filter, wash with water and dry to obtain mesoporous carbon.
[0063] (3) Disperse mesoporous carbon in 50 mL of water, then sonicate for 5 h, filter and dry to obtain capacitor graphene.
[0064] The difference between Comparative Example 4 and Example 1 is that Comparative Example 6 did not use 98% sulfuric acid-treated mesoporous carbon, while Example 1 used 98% sulfuric acid-treated mesoporous carbon.
[0065] Comparative Example 5
[0066] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a pulverizer, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to obtain carbonized lychee tree trunk powder.
[0067] (2) Add 10g of carbonized litchi trunk powder and 30g of potassium hydroxide pore-forming agent to an alumina crucible. Perform a high-temperature pore-forming reaction at 900℃ in a nitrogen atmosphere for 3h. Then soak in 1mol / L hydrochloric acid for 2h. Then filter, wash with water and dry to obtain mesoporous carbon.
[0068] (3) Acidified mesoporous carbon was obtained by acidifying it with 20 mL of 98% sulfuric acid at 80℃, filtering, washing with water and drying.
[0069] (4) Disperse acidified mesoporous carbon in 50 mL of water, then sonicate for 5 h, filter and dry to obtain capacitor graphene.
[0070] The difference between Comparative Example 5 and Example 1 is that the pore-forming agent used in Comparative Example 5 is potassium hydroxide, while the pore-forming agent used in Example 1 is a mixture of potassium hydroxide and calcium hydroxide.
[0071] Comparative Example 6
[0072] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a pulverizer, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to obtain carbonized lychee tree trunk powder.
[0073] (2) Add 10g of carbonized litchi trunk powder and 30g of calcium hydroxide pore-forming agent to an alumina crucible. Perform a high-temperature pore-forming reaction at 900℃ in a nitrogen atmosphere for 3h. Then soak in 1mol / L hydrochloric acid for 2h. Then filter, wash with water and dry to obtain mesoporous carbon.
[0074] (3) Acidified mesoporous carbon was obtained by acidifying it with 20 mL of 98% sulfuric acid at 80℃, filtering, washing with water and drying.
[0075] (4) Disperse acidified mesoporous carbon in 50 mL of water, then sonicate for 5 h, filter and dry to obtain capacitor graphene.
[0076] The difference between Comparative Example 6 and Example 1 is that the pore-forming agent used in Comparative Example 6 is calcium hydroxide, while the pore-forming agent used in Example 1 is a mixture of potassium hydroxide and calcium hydroxide.
[0077] Comparative Example 7
[0078] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a pulverizer, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to obtain carbonized lychee tree trunk powder.
[0079] (2) Add 10g of carbonized litchi trunk powder, 15g of potassium hydroxide and 15g of calcium hydroxide pore-forming agent to an alumina crucible. First, carry out a high-temperature pore-forming reaction at 350℃ in a nitrogen atmosphere for 2h; then carry out a high-temperature pore-forming reaction at 900℃ for 1h, followed by soaking in 1mol / L hydrochloric acid for 2h, and then filter, wash with water and dry to obtain mesoporous carbon.
[0080] (3) Acidified mesoporous carbon was obtained by acidifying it with 20 mL of 98% sulfuric acid at 80℃, filtering, washing with water and drying.
[0081] (4) Disperse acidified mesoporous carbon in 50 mL of water, then sonicate for 5 h, filter and dry to obtain capacitor graphene.
[0082] The difference between Comparative Example 7 and Example 3 is that Example 3 prepared capacitor graphene under a three-step high-temperature pore-forming reaction, while Comparative Example 7 prepared capacitor graphene under a two-step high-temperature pore-forming reaction.
[0083] Comparative Example 8
[0084] (1) The lychee tree trunk is crushed into particles with a diameter of 10-20 micrometers by a pulverizer, dried in an 80℃ forced-air drying oven, and then subjected to a high-temperature carbonization reaction at 400℃ in a nitrogen atmosphere for 2 hours to obtain carbonized lychee tree trunk powder.
[0085] (2) Add 10g of carbonized litchi trunk powder, 15g of potassium hydroxide and 15g of calcium hydroxide pore-forming agent to an alumina crucible. First, carry out a high-temperature pore-forming reaction at 500℃ in a nitrogen atmosphere for 1h; then carry out a high-temperature pore-forming reaction at 850℃ in a nitrogen atmosphere for 1h; finally, carry out a high-temperature pore-forming reaction at 1100℃ for 1h, then soak in 1mol / L hydrochloric acid for 2h, and then filter, wash with water and dry to obtain mesoporous carbon.
[0086] (3) Acidified mesoporous carbon was obtained by acidifying it with 20 mL of 98% sulfuric acid at 80℃, filtering, washing with water and drying.
[0087] (4) Disperse acidified mesoporous carbon in 50 mL of water, then sonicate for 5 h, filter and dry to obtain capacitor graphene.
[0088] The difference between Example 3 and Comparative Example 8 is that the three-step high-temperature pore-forming reaction conditions in Comparative Example 8 are different from those in Example 3.
[0089] When the capacitor graphene, carbonized lychee trunk powder, mesoporous carbon and acidified mesoporous carbon prepared in Examples 1-2 and Comparative Examples 1-8 were used as electrode materials for supercapacitors, the specific capacitance (F / g) after 30,000 cycles was tested. The test results are shown in Table 1.
[0090] Table 1
[0091]
[0092] As shown in Table 1, the specific capacitance of the graphene prepared in Examples 1-2 after 30,000 cycles as a supercapacitor electrode material is greater than 235 F / g, which is significantly higher than the specific capacitance of the graphene prepared in Examples 1-4 using carbonized lychee trunk powder, mesoporous carbon, acidified mesoporous carbon, and graphene as electrode materials. This indicates that the graphene prepared using lychee trunk as raw material according to the method described in this invention exhibits excellent cycling performance and a high specific capacitance as a supercapacitor electrode material. It also demonstrates that the four reaction steps of the method described in this invention are crucial and indispensable. Without any one of these steps, the graphene prepared will not possess excellent cycling performance when used as a supercapacitor electrode material. Only graphene prepared from lychee trunk as raw material through the four steps of high-temperature carbonization, pore-forming reaction, acidification treatment, and ultrasonic exfoliation exhibits excellent cycling performance when used as a supercapacitor electrode material.
[0093] The specific capacitance of the capacitive graphene prepared in Comparative Examples 5 and 6 after 30,000 cycles as a supercapacitor electrode material is significantly lower than that of the capacitive graphene prepared in Example 1. This indicates that the choice of pore-forming agent plays a crucial role in the excellent cycling performance of the prepared capacitive graphene when used as a supercapacitor electrode material during the preparation of capacitive graphene using the method described in this invention. When a combined pore-forming agent composed of potassium hydroxide and calcium hydroxide is used, the prepared capacitive graphene exhibits excellent cycling performance as a supercapacitor electrode material; its cycling performance is significantly higher than that of capacitive graphene prepared using potassium hydroxide or calcium hydroxide alone as the pore-forming agent. When both potassium hydroxide and calcium hydroxide are used as the pore-forming agent, the cycling performance of the prepared capacitive graphene as a supercapacitor electrode material can be synergistically improved.
[0094] As can be seen from the experimental data in Table 1, the specific capacitance of the graphene prepared in Example 3 after 30,000 cycles as a supercapacitor electrode material is significantly higher than that in Example 1. This indicates that when the pore-forming agent is a combination of potassium hydroxide and calcium hydroxide, the graphene prepared under the above-mentioned three-step high-temperature pore-forming reaction conditions of the present invention has a significantly improved cycle performance when used as a supercapacitor electrode material compared with the graphene prepared under the single-step high-temperature pore-forming reaction conditions.
[0095] Furthermore, the specific capacitance of the capacitive graphene prepared in Comparative Examples 7 and 8 after 30,000 cycles as a supercapacitor electrode material was not higher than or significantly higher than that in Example 1. This indicates that only capacitive graphene prepared under the above three-step high-temperature pore-forming reaction can significantly improve its cycle performance when used as a supercapacitor electrode material; while capacitive graphene prepared under other three-step high-temperature pore-forming reactions, or under other two-step high-temperature pore-forming reactions, cannot significantly improve its cycle performance when used as a supercapacitor electrode material.
Claims
1. A method for preparing capacitive graphene, characterized in that, It includes the following steps: (1) The lychee tree trunk is crushed and then subjected to high-temperature carbonization reaction to obtain carbonized lychee tree trunk powder; (2) The carbonized litchi trunk powder was subjected to a pore-forming reaction to obtain mesoporous carbon; (3) The mesoporous carbon is acidified to obtain acidified mesoporous carbon; (4) The capacitor graphene is obtained by ultrasonically exfoliating the acidified mesoporous carbon. The high-temperature carbonization reaction mentioned in step (1) is specifically carried out at 400~600℃ in a nitrogen atmosphere for 2~6 h; The pore-forming reaction in step (2) is as follows: a pore-forming agent is added to the carbonized litchi tree trunk powder, and a high-temperature pore-forming reaction is carried out at 600~1000℃ in a nitrogen atmosphere for 2~8 h. The pore-forming agent is composed of potassium hydroxide and calcium hydroxide.
2. The method for preparing capacitive graphene according to claim 1, characterized in that, The mass ratio of potassium hydroxide to calcium hydroxide is 1:1 to 1:0.
1.
3. The method for preparing capacitive graphene according to claim 1, characterized in that, The ratio of pore-forming agent to carbonized litchi trunk powder is 30-60g: 10-15g.
4. The method for preparing capacitive graphene according to claim 1, characterized in that, The acidification treatment described in step (3) specifically includes: Mesoporous carbon is acidified using 98% sulfuric acid at 60-90℃; the ratio of sulfuric acid to carbonized litchi trunk powder is 20-60mL:10-15g.
5. The method for preparing capacitive graphene according to claim 1, characterized in that, The specific method of ultrasonic stripping in step (4) is as follows: acidified mesoporous carbon is dispersed in ultrasonic liquid and then ultrasonically treated for 1~12 h.
6. The method for preparing capacitive graphene according to claim 5, characterized in that, The ultrasonic fluid is selected from one or a mixture of two or more of the following: water, N-methylpyrrolidone, N,N-dimethylformamide, and ethanol.
7. The method for preparing capacitive graphene according to claim 5, characterized in that, The ratio of ultrasonic fluid to carbonized litchi trunk powder is 50-60 mL: 10-15 g.