A method for preparing three-dimensional carbon nanotubes

Abstract

The present invention relates to a method for preparing three-dimensional carbon nanotubes, and belongs to the technical field of electrode material preparation. Hydroxyl multi-walled carbon nanotubes, cobalt acetate, and melamine are dissolved in methanol to obtain a mixture solution; the mixture solution is evaporated to remove methanol to obtain an evaporated mixture; the evaporated mixture is subjected to two-stage high-temperature treatment: the high-temperature treatment product is cooled to room temperature to obtain a precursor; the obtained precursor is soaked in a sulfuric acid solution with a concentration of 0.5-0.8 mol / L for 24-36 hours, and three-dimensional carbon nanotubes are obtained after the soaking is completed. The method of the present invention is simple, easy to control, and can prepare three-dimensional carbon nanotubes with excellent performance.

Description

Technical Field

[0001] The invention relates to a method for preparing three-dimensional carbon nanotubes, and belongs to the technical field of electrode material preparation. Background Art

[0002] As a one-dimensional nanomaterial, carbon nanotubes are light in weight, have perfectly connected hexagonal structures, and have many extraordinary mechanical, electrical and chemical properties. However, with the in-depth research on carbon nanotubes and nanomaterials, three-dimensional carbon nanotubes will have a wider range of application scenarios in the future. Compared with one-dimensional carbon nanotubes, three-dimensional carbon nanotubes have multi-dimensional conductivity and better mechanical properties.

[0003] At present, the main methods for preparing carbon nanotubes are: arc discharge method, laser ablation method, chemical vapor deposition method and the like.

[0004] Patent application number 2014103441241, a method for preparing a three-dimensional carbon nanotube network. Active metals: sodium, potassium, magnesium, calcium, carbon dioxide are used as raw materials, and a metal mesh is used as a template. The above-mentioned active metals and metal mesh are placed in a high-temperature furnace, heated under the protection of argon or nitrogen, and then carbon dioxide or a mixed gas of carbon dioxide and nitrogen or argon is introduced. The three-dimensional carbon nanotube network is directly prepared on the metal mesh by the redox reaction between the active metal and carbon dioxide. The size of the carbon nanotube can be controlled by adjusting the reaction temperature, reaction time and the flow rate of the gas introduced. The raw materials of the present invention are cheap and easy to obtain, low in cost, simple in synthesis process, and greenhouse gas carbon dioxide is used as raw material, which is environmentally friendly. The obtained carbon nanotube network has good electrical conductivity and mechanical properties, and can be widely used in the preparation of electrode materials for supercapacitors or lithium-ion electronics. However, this method must use a metal mesh as a template, and the method is relatively complicated.

[0005] Patent application number is 2017108182957, a three-dimensional stereoscopic carbon nanotube and its preparation method. In this method, ferrocene and thiophene are dissolved in benzene, heated under nitrogen protection, and then the reaction solution is introduced into a high-temperature reactor in a nitrogen and hydrogen atmosphere by a pulse pump, and high-temperature catalytic cracking is performed into carbon nanotubes. The three-dimensional stereoscopic carbon nanotubes prepared by this method are formed by straight or curved carbon nanotubes connected to each other in a three-dimensional structure, and even form a closed-loop structure. However, this method must rely on certain equipment during the preparation process, such as pulse pumps and other equipment.

[0006] How to find a simple method to prepare three-dimensional carbon nanotubes and produce three-dimensional carbon nanotubes with excellent performance is a technical challenge. Summary of the invention

[0007] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for preparing three-dimensional carbon nanotubes. The method of the present invention is simple and easy to control, and can prepare three-dimensional carbon nanotubes with excellent performance. The present invention is achieved through the following technical solutions.

[0008] A method for preparing three-dimensional carbon nanotubes, the specific steps of which include:

[0009] Step 1, dissolving hydroxyl multi-walled carbon nanotubes, cobalt acetate and melamine in methanol to obtain a mixture solution;

[0010] Step 2, evaporating the mixture solution obtained in step 1 to remove methanol to obtain an evaporated mixture;

[0011] Step 3: subjecting the evaporated mixture obtained in step 2 to two-stage high-temperature treatment:

[0012] Step 3.1, under the condition of continuous nitrogen flow, the evaporated mixture was heated to 600-700°C at a heating rate of 2°C / min and kept at this temperature for 3-4h;

[0013] Step 3.2, continue to introduce nitrogen, and then heat up to 800-900°C at a heating rate of 3°C / min and keep warm for 2-2.5h to obtain a high temperature treatment product;

[0014] After the heat preservation of step 3.3 and step 3.2 is completed, nitrogen is continuously introduced to cool the high temperature treated product to room temperature to obtain a precursor;

[0015] Step 4: Soak the precursor obtained in step 3.3 in a sulfuric acid solution with a concentration of 0.5-0.8 mol / L for 24-36 hours to obtain three-dimensional carbon nanotubes.

[0016] In the step 1, the mass ratio of hydroxyl multi-walled carbon nanotubes to cobalt acetate and melamine is 3-15:60-298.9:64-320.

[0017] The evaporation process of step 2 is: evaporating with magnetic stirring in a water bath at 60° C.-70° C. for 3-4 hours.

[0018] The nitrogen flow rate in steps 3.1, 3.2 and 3.3 is 5-6 L / min.

[0019] The beneficial effects of the present invention are:

[0020] (1) The method of the present invention is simple and easy to control;

[0021] (2) The three-dimensional carbon nanotubes prepared by the present invention are tightly connected and overlapped with each other, and the macro-network skeleton is clear. The diameter of a single carbon nanotube is about 10 nanometers and the length varies from several micrometers. The three-dimensional carbon nanotubes prepared by the present invention have excellent performance and can be directly used in the process of preparing electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a TEM image A of the three-dimensional carbon nanotubes prepared in Example 1 of the present invention;

[0023] Figure 2 is a TEM image B of the three-dimensional carbon nanotubes prepared in Example 1 of the present invention;

[0024] Figure 3 This is TEM image C of the three-dimensional carbon nanotubes prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0026] Example 1

[0027] The preparation method of the three-dimensional carbon nanotubes comprises the following specific steps:

[0028] Step 1, dissolving 0.015 g of hydroxyl multi-walled carbon nanotubes, 0.2989 g of cobalt acetate and 0.32 g of melamine in 50 mL of methanol, and stirring magnetically for 1 h to obtain a mixture solution;

[0029] Step 2, the mixture solution obtained in step 1 is placed in a 60° C. water bath with magnetic stirring for 3 h to evaporate and remove methanol to obtain an evaporated mixture;

[0030] Step 3: subjecting the evaporated mixture obtained in step 2 to two-stage high-temperature treatment:

[0031] Step 3.1, under the condition of continuous nitrogen flow (nitrogen flow rate is 5 L / min), the evaporated mixture is heated to 600°C at a heating rate of 2°C / min and kept at this temperature for 3 h;

[0032] Step 3.2, continue to introduce nitrogen (the amount of nitrogen introduced is 5 L / min), then increase the temperature to 800°C at a heating rate of 3°C / min and keep it for 2 hours to obtain a high temperature treatment product;

[0033] After the heat preservation of step 3.3 and step 3.2 is completed, nitrogen is continuously introduced (the amount of nitrogen introduced is 5 L / min), and the high-temperature treatment product is cooled to room temperature to obtain a precursor;

[0034] Step 4: Soak the precursor obtained in step 3.3 in 20 mL of 0.5 mol / L sulfuric acid solution for 24 hours to obtain three-dimensional carbon nanotubes.

[0035] The TEM image of the three-dimensional carbon nanotubes prepared in this example is as follows Figures 1 to 3 As shown. Figures 1 to 3 It can be seen that this method has obtained a large number of three-dimensional carbon nanotubes, the tubes are tightly connected and overlapped with each other, and the large network skeleton is clear. The diameter of a single carbon nanotube is about 10 nanometers and the length varies from several microns.

[0036] The three-dimensional carbon nanotubes prepared by the present invention have a specific capacitance value of up to 80F / g, have excellent electrical conductivity, and can be directly used in the process of preparing electrode materials.

[0037] Example 2

[0038] The preparation method of the three-dimensional carbon nanotubes comprises the following specific steps:

[0039] Step 1, dissolving 0.003 g of hydroxyl multi-walled carbon nanotubes, 0.06 g of cobalt acetate and 0.064 g of melamine in 30 mL of methanol, and magnetically stirring for 1 h to obtain a mixture solution;

[0040] Step 2, the mixture solution obtained in step 1 is placed in a 70° C. water bath with magnetic stirring for 4 hours to evaporate and remove methanol to obtain an evaporated mixture;

[0041] Step 3: subjecting the evaporated mixture obtained in step 2 to two-stage high-temperature treatment:

[0042] Step 3.1, under the condition of continuous nitrogen flow (nitrogen flow rate is 6 L / min), the evaporated mixture is heated to 700°C at a heating rate of 2°C / min and kept at this temperature for 4 h;

[0043] Step 3.2, continue to introduce nitrogen (the amount of nitrogen introduced is 6 L / min), then increase the temperature to 900°C at a heating rate of 3°C / min and keep it for 2.5 hours to obtain a high temperature treatment product;

[0044] After the heat preservation of step 3.3 and step 3.2 is completed, nitrogen is continuously introduced (the amount of nitrogen introduced is 6 L / min), and the high-temperature treatment product is cooled to room temperature to obtain a precursor;

[0045] Step 4: Soak the precursor obtained in step 3.3 in 20 mL of 0.8 mol / L sulfuric acid solution for 36 hours to obtain three-dimensional carbon nanotubes.

[0046] The three-dimensional carbon nanotubes prepared by the present invention have a specific capacitance value of up to 65F / g, have excellent electrical conductivity, and can be directly used in the process of preparing electrode materials.

[0047] Example 3

[0048] The preparation method of the three-dimensional carbon nanotubes comprises the following specific steps:

[0049] Step 1, dissolving 0.003 g of hydroxyl multi-walled carbon nanotubes, 0.06 g of cobalt acetate and 0.064 g of melamine in 40 mL of methanol, and magnetically stirring for 1 h to obtain a mixture solution;

[0050] Step 2, the mixture solution obtained in step 1 is placed in a 65° C. water bath with magnetic stirring for 3.5 hours to evaporate and remove methanol to obtain an evaporated mixture;

[0051] Step 3: subjecting the evaporated mixture obtained in step 2 to two-stage high-temperature treatment:

[0052] Step 3.1, under the condition of continuous nitrogen flow (nitrogen flow rate is 5.5 L / min), the evaporated mixture is heated to 650°C at a heating rate of 2°C / min and kept at this temperature for 3.5 h;

[0053] Step 3.2, continue to introduce nitrogen (the amount of nitrogen introduced is 5.5 L / min), then increase the temperature to 850°C at a heating rate of 3°C / min and keep it for 2.2 h to obtain a high temperature treatment product;

[0054] After the heat preservation of step 3.3 and step 3.2 is completed, nitrogen gas is continuously introduced (the amount of nitrogen introduced is 5.5 L / min), and the high-temperature treatment product is cooled to room temperature to obtain a precursor;

[0055] Step 4: Soak the precursor obtained in step 3.3 in 20 mL of 0.6 mol / L sulfuric acid solution for 30 h to obtain three-dimensional carbon nanotubes.

[0056] The three-dimensional carbon nanotubes prepared by the present invention have a specific capacitance value of up to 70F / g, have excellent performance, and can be directly used in the process of preparing electrode materials.

[0057] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing three-dimensional carbon nanotubes, characterized in that The specific steps include: Step 1, dissolving hydroxyl multi-walled carbon nanotubes, cobalt acetate and melamine in methanol to obtain a mixture solution; Step 2, evaporating the mixture solution obtained in step 1 to remove methanol to obtain an evaporated mixture; Step 3: subjecting the evaporated mixture obtained in step 2 to two-stage high-temperature treatment: Step 3.1, under the condition of continuous nitrogen flow, the evaporated mixture was heated to 600-700°C at a heating rate of 2°C / min and kept at this temperature for 3-4h; Step 3.2, continue to introduce nitrogen, and then heat up to 800-900°C at a heating rate of 3°C / min and keep warm for 2-2.5h to obtain a high temperature treatment product; After the heat preservation of step 3.3 and step 3.2 is completed, nitrogen is continuously introduced to cool the high temperature treated product to room temperature to obtain a precursor; Step 4, soaking the precursor obtained in step 3.3 in a sulfuric acid solution with a concentration of 0.5-0.8 mol / L for 24-36 hours, and obtaining three-dimensional carbon nanotubes after the soaking is completed; In the step 1, the mass ratio of hydroxyl multi-walled carbon nanotubes to cobalt acetate and melamine is 3-15:60-298.9:64-320.

2. The method for preparing three-dimensional carbon nanotubes according to claim 1, characterized in that: The evaporation process of step 2 is: evaporating with magnetic stirring in a water bath at 60° C.-70° C. for 3-4 hours.

3. The method for preparing three-dimensional carbon nanotubes according to claim 1, characterized in that: The nitrogen flow rate in steps 3.1, 3.2 and 3.3 is 5-6 L / min.

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