Preparation method of camphor seed-based activated carbon for supercapacitor

Abstract

The present invention belongs to the field of supercapacitors, and particularly relates to a preparation method of camphor seed-based activated carbon for supercapacitors. First, the camphor seeds are pretreated by washing, drying, etc. to remove surface impurities, then the carbon materials are obtained by using the one-step carbonization / activation method with anhydrous copper chloride, and finally, they are stirred in a mixed solution of sulfuric acid and hydrogen peroxide and washed and filtered with deionized water to obtain the activated carbon material derived from camphor seeds with good supercapacitance characteristics. The activated carbon material for supercapacitors derived from camphor seeds prepared by the present invention has excellent electrochemical performance. During its preparation process, the raw materials are cheap and easily available, the cost is low, the method is simple and feasible, and there is no template and surfactant. The supercapacitor electrode of the prepared activated carbon material has a high specific capacitance, and the maximum specific capacitance can reach 433 F / g. When it is assembled into a symmetric supercapacitor, after 5000 cycles, the Coulomb efficiency remains 100%, and the capacitance remains above 80 F / g.

Description

Technical Field

[0001] The present invention belongs to the field of supercapacitors, and particularly relates to a preparation method of camphor seed-based activated carbon for supercapacitors. Technical Background

[0002] Supercapacitors have characteristics such as high specific capacitance, wide working voltage range, environmental friendliness, high energy density and high power density, and possess the high power output of traditional capacitors and the ability of secondary batteries to store charges. Supercapacitors mainly consist of four parts, namely current collectors, electrolytes, electrode materials, and separators, among which the electrode materials are the main factors determining the capacitance of the capacitors. Activated carbon is currently the most widely used electrode material for supercapacitors, and its future application fields and application quantities will both increase rapidly. The raw materials for preparing activated carbon are very rich, and activated carbon prepared from carbon-rich substances such as coal, petroleum coke, and phenolic resin through carbonization and activation can all be used as electrode materials for supercapacitors. However, finding a preparation method of activated carbon with low cost, environmental friendliness, renewability, and high performance has attracted wide attention. In recent years, there have been many reports on using biomass to prepare carbon materials, such as almond shells, wheat straws, sugarcane bagasse, fruit peels, etc. This kind of carbon material has greatly reduced the cost compared with the carbon materials prepared using traditional chemical reagents. At the same time, it has also reduced environmental pollution and is conducive to the sustainable development of society. However, there have been no reports on using camphor seeds to prepare activated carbon materials. Camphor seeds are inexpensive and easy to obtain, and the preparation process is simple and easy to operate. Therefore, using camphor seeds to prepare supercapacitor electrode materials to solve the problems of high price and environmental pollution existing in the preparation methods of traditional carbon materials has good research significance. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of camphor seed-based activated carbon for supercapacitors with rich raw materials and low cost. By using a simple one-step carbonization / activation method with copper chloride anhydrous, an activated carbon material derived from camphor seeds with good supercapacitance characteristics is obtained, and the supercapacitor electrode of the prepared activated carbon material has a high specific capacitance.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A preparation method of camphor seed-based activated carbon for supercapacitors. First, the camphor seeds are pretreated to remove surface impurities; then, through a one-step carbonization / activation method with copper chloride, a camphor seed-based activated carbon material with good supercapacitance characteristics is obtained.

[0006] The preparation method of the camphor seed-based activated carbon for supercapacitors includes the following steps:

[0007] (1) The pretreatment is washing and drying. The collected camphor tree seeds are ultrasonically washed with deionized water and absolute ethanol for 0.5 - 2 h respectively to remove impurities on the material surface. After the ultrasonic treatment is completed, they are placed in a blast drying oven and dried at 60°C - 80°C for 6 - 12 h. The dried camphor tree seeds are placed in a mortar and ground to obtain powder.

[0008] (2) The powder ground in step (1) is mixed evenly with anhydrous copper chloride powder. The mixed powder is placed in a magnetic boat and transferred into a tube furnace. A protective gas is introduced, and the temperature is raised to 650 - 950°C and kept constant for 1 - 4 h. After the tube furnace is cooled to room temperature, the carbonized product of camphor tree seeds is obtained.

[0009] (3) The carbonized product obtained in step (2) is transferred into a mixed solution of sulfuric acid and hydrogen peroxide. The concentration of sulfuric acid in the mixed solution is 0.2 - 1 mol / L, and the concentration of hydrogen peroxide is 1 - 2.5 mol / L. They are mixed and stirred for 12 - 24 h; then washed with deionized water and filtered by suction. Finally, the material obtained by suction filtration is placed in a drying oven and dried at 100 - 150°C for 8 - 16 h to obtain the activated carbon material derived from camphor tree seeds.

[0010] In the preparation method of the camphor tree seed-based activated carbon for supercapacitors, in step (2), the mass ratio of the ground powder to the anhydrous copper chloride powder is 1:5 - 1:15. The ground powder is a 30 - 50 mesh sieve, and the anhydrous copper chloride powder is a 50 - 100 mesh sieve.

[0011] In the preparation method of the camphor tree seed-based activated carbon for supercapacitors, in step (2), the protective gas is nitrogen.

[0012] In the preparation method of the camphor tree seed-based activated carbon for supercapacitors, in step (2), the heating rate is 2.5°C / min - 5.5°C / min.

[0013] In the preparation method of the camphor tree seed-based activated carbon for supercapacitors, in step (3), the rotation speed of the mixing and stirring is 200 - 300 rpm.

[0014] In the preparation method of the camphor tree seed-based activated carbon for supercapacitors, in step (3), the specific surface area of the obtained camphor tree seed-based activated carbon material is 1350 - 1550 m 2 / g.

[0015] The design concept of the present invention is:

[0016] The present invention uses camphor tree seeds as a precursor and anhydrous copper chloride as an oxidizing divalent copper salt. The two undergo a redox reaction at high temperature and etch the carbon material, forming a large number of micropores on the surface of the carbon material, resulting in the prepared camphor tree seed-based activated carbon having a high specific surface area. As an electrode material for supercapacitors, it has a high specific capacitance, and the assembled symmetric supercapacitor has good cycle stability.

[0017] The remarkable advantages and beneficial effects of the present invention are as follows:

[0018] The present invention adopts the anhydrous copper chloride one-step carbonization / activation method to obtain activated carbon materials derived from camphor tree seeds with good supercapacitor characteristics. The present invention uses naturally fallen camphor tree seeds as raw materials, which are easy to obtain, low in cost, simple and feasible, and without templates and surfactants, enabling the comprehensive utilization of biomass waste. The prepared activated carbon material supercapacitor electrode has a high specific capacitance, and the maximum specific capacitance can reach 433 F / g. When assembled into a symmetric supercapacitor, after 5000 cycles, the Coulomb efficiency remains 100%, and the capacitance remains above 80 F / g. Description of the Drawings

[0019] Figure 1 It is the X-ray diffraction pattern of the camphor tree seed-based activated carbon. In the figure, the abscissa 2θ represents the diffraction angle (degree), and the ordinate Intensity represents the intensity (a.u.).

[0020] Figure 2 It is the scanning electron microscope image of the camphor tree seed-based activated carbon.

[0021] Figure 3 (a)- Figure 3 (b) is the electrochemical performance diagram of the camphor tree seed-based activated carbon. Among them, Figure 3 (a) is the cyclic voltammogram of the camphor tree seed-based activated carbon electrode at different scanning rates. The abscissa Potential represents the potential (V), and the ordinate Current represents the current (A); Figure 3 (b) is the specific capacitance diagram calculated for the camphor tree seed-based activated carbon electrode at different scanning rates. The abscissa Scan Rate represents the scanning rate (mV / s), and the ordinate Specific Capacitance represents the specific capacitance (F / g).

[0022] Figure 4 It is the cycle performance diagram of the symmetric capacitor assembled from the camphor tree seed-based activated carbon material at a current density of 0.5 A / g. In the figure, the abscissa Cycle number represents the number of cycles, the left ordinate Capacitance retention represents the capacitance retention rate (%), and the right ordinate Coulombic efficiency represents the Coulomb efficiency (%). Detailed implementation mode

[0023] In the specific implementation process, the present invention proposes a preparation method of camphor seed-based activated carbon for supercapacitors. First, the camphor seeds are pretreated by washing, drying, etc. to remove surface impurities, and then the carbonization product of camphor seeds is obtained by using anhydrous copper chloride one-step carbonization / activation method. Finally, it is stirred in a mixed solution of sulfuric acid and hydrogen peroxide and washed and filtered with deionized water to obtain an activated carbon material derived from camphor seeds with good supercapacitance characteristics. The function and effect of washing are to remove the residual metal ions and acid in the sample and obtain a purer activated carbon material. The activated carbon supercapacitor electrode material derived from camphor seeds developed by the present invention has excellent electrochemical performance.

[0024] The following examples are used to further illustrate the present invention, but the protection scope of the present invention is not limited to the following examples.

[0025] Example 1

[0026] In this example, the camphor seeds are pretreated by ultrasonic waves in deionized water and anhydrous ethanol for 0.5 h respectively to remove the impurities on the surface of the material. After the ultrasonic wave is completed, it is placed in a blast drying oven and dried at 70 °C for 10 h. The dried camphor seeds are ground into powder, and the ground powder (30-50 mesh sieve) and anhydrous copper chloride (50-100 mesh sieve) are mixed evenly according to the mass ratio of 1:8.5. The mixed powder is placed in a magnetic boat and transferred into a tubular furnace, and high-temperature carbonization is carried out at 750 °C for 2 h in a protective nitrogen atmosphere. After the tubular furnace is cooled to room temperature, the carbonization product of camphor seeds is obtained; the carbonization product is transferred into a mixed solution of 0.2 mol / L sulfuric acid and 1.2 mol / L hydrogen peroxide, and mixed and stirred for 12 h, and the rotation speed of the mixed stirring is 270 rpm. Then it is washed and filtered with deionized water, and finally placed in a vacuum drying oven and dried at 120 °C for 12 h to obtain an activated carbon material derived from camphor seeds, that is, the activated carbon electrode material derived from camphor seeds for the supercapacitor, and its specific surface area is 1350-1550 m 2 / g.

[0027] As Figure 1 shown, from the X-ray diffraction pattern of the camphor seed-based activated carbon, it can be seen that the material prepared by the present invention is an activated carbon material with a certain graphite structure.

[0028] As Figure 2 shown, from the scanning electron microscope image of the camphor seed-based activated carbon, it can be seen that the material prepared by the present invention has a layered porous carbon nanosheet structure.

[0029] Example 2 Electrochemical performance test

[0030] In this example, the camphor seed-based activated carbon electrode prepared in Example 1 was subjected to electrochemical performance testing.

[0031] As Figure 3 (a) shows that when the electrolyte is an aqueous potassium hydroxide solution with a concentration of 6 mol / L, the scanning rates are 1 mV / s, 2 mV / s, 5 mV / s, 10 mV / s, 20 mV / s, 50 mV / s, 100 mV / s, 150 mV / s, and 200 mV / s, and the voltage is -1 to 0 V. As the scanning rate increases, the CV curve maintains a good quasi-rectangular shape, indicating its good capacitive behavior.

[0032] As Figure 3 (b) shows that when the electrolyte is an aqueous potassium hydroxide solution with a concentration of 6 mol / L, the specific capacitance of the camphor seed-based activated carbon electrode is 171 F / g at a scanning rate of 200 mV / s. The scanning rates are 200 mV / s, 150 mV / s, 100 mV / s, 50 mV / s, 20 mV / s, 10 mV / s, 5 mV / s, 2 mV / s, and 1 mV / s. As the scanning rate decreases, the specific capacitance gradually increases. The specific capacitance of the camphor seed-based activated carbon electrode is as high as 433 F / g at a scanning rate of 1 mV / s.

[0033] As Figure 4 shown, the camphor seed-based activated carbon electrode was assembled into a symmetric supercapacitor. After 5000 cycles, the Coulomb efficiency of the device remained 100%, and the capacitance remained above 80 F / g.

[0034] Example 3

[0035] In this example, the camphor seeds were pretreated by ultrasonic treatment with deionized water and absolute ethanol for 1 h respectively to remove impurities on the material surface. After the ultrasonic treatment was completed, they were placed in a blast drying oven and dried at 80 °C for 10 h. The dried camphor seeds were ground into powder. The ground powder (30 - 50 mesh sieve) was mixed evenly with anhydrous copper chloride (50 - 100 mesh sieve) in a mass ratio of 1:9. The mixed powder was placed in a magnetic boat and transferred into a tubular furnace. Nitrogen was introduced as a protective gas, and high-temperature calcination was carried out at 850 °C for 2 h. After the tubular furnace cooled to room temperature, the carbonized product of the camphor seeds was obtained. The carbonized product was transferred into a mixed solution of 0.3 mol / L sulfuric acid and 1.8 mol / L hydrogen peroxide, and mixed and stirred for 16 h at a rotation speed of 300 rpm. Then it was washed by filtration with deionized water, and finally placed in a drying oven and dried at 120 °C for 12 h to obtain the activated carbon material derived from camphor seeds, that is, the activated carbon electrode material for the supercapacitor derived from camphor seeds, and its specific surface area is 1350 - 1550 m 2 / g.

[0036] Example 4

[0037] In this embodiment, the camphor tree seeds are pretreated by ultrasonic treatment with deionized water and absolute ethanol for 1 h in sequence to remove impurities on the surface of the material. After the ultrasonic treatment is completed, they are placed in a forced-air drying oven and dried at 80 °C for 12 h. The dried camphor tree seeds are ground into powder, and the ground powder (30 - 50 mesh sieve) and cupric chloride anhydrous (50 - 100 mesh sieve) are mixed evenly according to a mass ratio of 1:12. The mixed powder is placed into a magnetic boat and transferred into a tubular furnace. Nitrogen is introduced as a protective gas, and high-temperature calcination is carried out at 950 °C for 2 h. After the tubular furnace is cooled to room temperature, the carbonized product of the camphor tree seeds is obtained; the carbonized product is transferred into a mixed solution of 0.5 mol / L sulfuric acid and 2.5 mol / L hydrogen peroxide, and mixed and stirred for 20 h at a stirring speed of 240 rpm. Then it is washed by filtration with deionized water, and finally the filter cake is placed in a drying oven and dried at 120 °C for 12 h to obtain the activated carbon material derived from camphor tree seeds, that is, the activated carbon electrode material derived from camphor tree seeds for the supercapacitor, and its specific surface area is 1350 - 1550 m 2 / g.

[0038] The results of the embodiment show that the supercapacitor electrode made of the activated carbon material derived from camphor tree seeds prepared by the present invention has a very high specific capacitance. During the implementation of this method, the raw material cost is low, it is renewable, simple and easy to operate, and there is no template and surfactant.

[0039] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A preparation method of camphor seed-based activated carbon for supercapacitors, characterized in that, First, the camphor tree seeds are pre-treated to remove surface impurities; then, through the copper chloride one-step carbonization / activation method, a camphor tree seed-based activated carbon material with good supercapacitor characteristics is obtained. The preparation method of the camphor tree seed-based activated carbon for supercapacitors includes the following steps: (1) The pre-treatment is washing and drying. The collected camphor tree seeds are ultrasonically washed with deionized water and absolute ethanol for 0.5 - 2 h respectively to remove surface impurities. After ultrasonic treatment, they are placed in a blast drying oven and dried at 60℃ - 80℃ for 6 - 12 h. The dried camphor tree seeds are placed in a mortar and ground into powder. (2) The powder ground in step (1) is mixed evenly with anhydrous copper chloride powder. The mixed powder is placed in a magnetic boat and transferred into a tubular furnace. A protective gas is introduced, and the temperature is raised to 750 - 950℃ and kept constant for 1 - 4 h. After the tubular furnace cools to room temperature, the carbonized product of the camphor tree seeds is obtained. (3) The carbonized product obtained in step (2) is transferred into a mixed solution of sulfuric acid and hydrogen peroxide. The concentration of sulfuric acid in the mixed solution is 0.2 - 1 mol / L, and the concentration of hydrogen peroxide is 1 - 2.5 mol / L. They are mixed and stirred for 12 - 24 h; then washed and filtered with deionized water. Finally, the material obtained by filtration is placed in a drying oven and dried at 100 - 150℃ for 8 - 16 h to obtain the activated carbon material derived from camphor tree seeds. Using camphor tree seeds as the precursor and anhydrous copper chloride as an oxidizing divalent copper salt, an oxidation-reduction reaction occurs between the two at high temperature and etches the carbon material, forming micropores on the surface of the carbon material. The prepared camphor tree seed-based activated carbon material has a layered porous carbon nanosheet structure.

2. The preparation method of camphor tree seed-based activated carbon for supercapacitors according to claim 1, characterized in that, In step (2), the mass ratio of the ground powder to the anhydrous copper chloride powder is 1:5 - 1:

15. The ground powder is 30 - 50 mesh sieve, and the anhydrous copper chloride powder is 50 - 100 mesh sieve.

3. The preparation method of camphor seed-based activated carbon for supercapacitors according to claim 1, characterized in that, In step (2), the protective gas is nitrogen.

4. The preparation method of camphor seed-based activated carbon for supercapacitors according to claim 1, characterized in that, In step (2), the heating rate is 2.5℃ / min - 5.5℃ / min.

5. The preparation method of camphor seed-based activated carbon for supercapacitors according to claim 1, characterized in that, In step (3), the rotation speed of the mixed stirring is 200 - 300 rpm.

6. The preparation method of camphor seed-based activated carbon for supercapacitors according to claim 1, characterized in that In step (3), the specific surface area of the camphor seed-based activated carbon material obtained is 1350 - 1550 m 2 / g.

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