CN110127660B - Method for Microwave Preparation of Porous Carbon Nanomaterials - Google Patents

Abstract

The invention discloses a method for preparing porous carbon nanometer material by microwave. The method uses a mixture of carbon powder and toluene with a mass ratio of 1:1 as a microwave reactant, mixes the microwave reactant and potassium citrate at a mass ratio of 1:10-200, grinds them, and then places them under 200-800W Microwave heating is used to prepare porous carbon nanomaterials. The method of the invention is simple, efficient and low in cost, and the prepared porous carbon nanometer material has relatively high specific surface area and specific capacitance, and can be used as a high-performance supercapacitor material.

Description

Method for Microwave Preparation of Porous Carbon Nanomaterials

technical field

The invention relates to the technical field of carbon material preparation, and relates to a method for preparing porous carbon nanomaterials by microwave.

Background technique

Porous carbon materials have the characteristics of size-controllable pore structure, good electrical and thermal conductivity, and adjustable surface composition. They can be used as excellent electrode materials for lithium-ion batteries and supercapacitors. The preparation of porous carbon materials is mainly formed by high-temperature treatment of carbon-containing precursor raw materials under the protection of an inert atmosphere. By selecting the type of precursor and various activation methods, the morphology, pore structure and surface components of carbon materials are regulated. In addition to high temperature activation to synthesize carbon materials, it is often necessary to add some additives such as water vapor, CO ₂ , KOH, ZnCl ₂ , etc. during the material activation process. Although the above methods can obtain porous carbon materials with high pore size distribution and high specific surface area, they often consume high energy consumption and low yield, and post-processing will cause secondary pollution, which is not conducive to energy conservation and environmental protection.

As a new heating method, the microwave reaction method has the advantages of fast heating rate, high reaction degree, energy saving and environmental protection. Voiry's research group adopted the method of household microwave preheating combined with microwave reduction (Science, 2016, 353, 1413), and the prepared graphene has a high content of carbon groups and a small number of surface defects. The instantaneous high heat generated by microwave can deeply deoxidize graphene oxide and promote the recombination of carbon atoms to reduce defects. However, the pretreatment requires a long time of traditional heating to pre-reduce graphene oxide. In the Chinese patent application CN108258240A, although microwave-assisted experiments were used, the mixture was only synthesized by microwaves, and subsequent high-temperature calcination was required to produce hollow carbon spheres with a porous structure. The experimental steps were cumbersome, time-consuming, and costly.

Contents of the invention

The purpose of the present invention is to provide a rapid and efficient method for preparing porous carbon nanomaterials by microwave with high specific surface area and high specific capacitance, so as to solve the problems of long reaction time, large energy consumption and high production cost in the prior art.

The technical scheme that realizes the object of the present invention is as follows:

The method for microwave preparation of porous carbon nanomaterials, the specific steps are as follows:

Use the mixture of carbon powder and toluene with a mass ratio of 1:1 as the microwave reactant, mix the microwave reactant and potassium citrate at a mass ratio of 1:10-200, grind them, and then place them under 200-800W for microwave heating. After the reaction is finished, cool naturally, wash, filter under reduced pressure and dry to obtain a porous carbon nanomaterial.

The carbon powder of the present invention is selected from graphite, acetylene black or activated carbon.

Preferably, the mass ratio of the microwave reactant to potassium citrate is 1:100-200.

Preferably, the grinding time is 10-20 min, and the microwave heating time is 60-600 s, which can reduce energy consumption while ensuring sufficient reaction of raw materials.

Preferably, the washing is sequentially washing with 10-50% dilute hydrochloric acid and water to remove impurities.

Preferably, the drying temperature is 50-100° C., which can not only fully dry the porous carbon nanomaterials, but also prevent the surface oxidation of the porous carbon nanomaterials.

Compared with the prior art, the present invention has the following advantages:

The method of the invention is simple and easy, has short reaction time, does not need to use a large-scale high-energy-consuming heating device, uses potassium citrate as a carbon source, is environmentally friendly, and has low cost, and the prepared porous carbon nanomaterial has stable physical and chemical properties and has a relatively high specific surface area. and specific capacitance.

Description of drawings

FIG. 1 is a scanning electron microscope image of the material prepared in Example 1.

Fig. 2 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in Example 1.

Fig. 3 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in Example 2.

Fig. 4 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in Example 3.

Fig. 5 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in Comparative Example 1.

Fig. 6 is (a) cyclic voltammetry curve and (b) charge-discharge curve diagram of the material prepared in Comparative Example 2.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and accompanying drawings.

Example 1

Take by weighing microwave reactant 0.01g and potassium citrate 1g, wherein microwave reactant is the mixture of graphite and toluene, mass ratio is 1:1, microwave reactant and potassium citrate are mixed in mortar and ground fully 10 minutes, then Place in a microwave reactor for microwave heating, the reaction power is 600W, and the reaction time is 300s. After the product was naturally cooled, the product was washed with 1 mol/L hydrochloric acid and water to remove impurities, filtered under reduced pressure and dried in an oven at 60°C to obtain a porous carbon nanomaterial. Its specific surface area is 1200 m ² /g.

Example 2

Take by weighing microwave reactant 0.01g and potassium citrate 0.1g, wherein microwave reactant is the mixture of graphite and toluene, mass ratio is 1:1, microwave reactant and potassium citrate are mixed in mortar and ground fully 10 minutes, Then place it in a microwave reactor for microwave heating, the reaction power is 600W, and the reaction time is 300s. After the product was naturally cooled, the product was washed with 1 mol/L hydrochloric acid and water to remove impurities, filtered under reduced pressure and dried in an oven at 60°C to obtain a porous carbon nanomaterial.

Example 3

Take by weighing microwave reactant 0.01g and potassium citrate 2g, wherein microwave reactant is the mixture of graphite and toluene, mass ratio is 1:1, microwave reactant and potassium citrate are mixed in mortar and ground fully 10 minutes, then Place in a microwave reactor for microwave heating, the reaction power is 600W, and the reaction time is 300s. After the product was naturally cooled, the product was washed with 1 mol/L hydrochloric acid and water to remove impurities, filtered under reduced pressure and dried in an oven at 60°C to obtain a porous carbon nanomaterial.

Comparative example 1

Take by weighing microwave reactant 0.01g and potassium citrate 0.09g, wherein microwave reactant is the mixture of graphite and toluene, mass ratio is 1:1, microwave reactant and potassium citrate are mixed in mortar and ground fully 10 minutes, Then place it in a microwave reactor for microwave heating, the reaction power is 600W, and the reaction time is 300s. After the product was naturally cooled, the product was washed with 1 mol/L hydrochloric acid and water to remove impurities, filtered under reduced pressure and dried in an oven at 60°C to obtain a porous carbon nanomaterial.

Comparative example 2

Take by weighing microwave reactant 0.01g and potassium citrate 2.1g, wherein microwave reactant is the mixture of graphite and toluene, mass ratio is 1:1, microwave reactant and potassium citrate are mixed in mortar and ground fully 10 minutes, Then place it in a microwave reactor for microwave heating, the reaction power is 600W, and the reaction time is 300s. After the product was naturally cooled, the product was washed with 1 mol/L hydrochloric acid and water to remove impurities, filtered under reduced pressure and dried in an oven at 60°C to obtain a porous carbon nanomaterial.

Fig. 1 is a scanning electron microscope image of the material prepared in Example 1. It can be seen from the figure that the nitrogen-doped carbon nanosheet is a porous structure with a pore diameter of about 0.4 microns and a wall thickness of about 30 nanometers.

Fig. 2 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in embodiment 1, it can be known from the curve that the specific capacitance of the material prepared in embodiment 1 is 318F/g, has higher specific electric capacity capacity.

Fig. 3 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in Example 2, and it can be known from the curve that the specific capacitance of the material prepared in Example 2 is 186.2 F/g.

Fig. 4 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in Example 3, and it can be known from the curve that the specific capacitance of the material prepared in Example 3 is 259 F/g.

Fig. 5 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in comparative example 1, as can be seen from the curve, the specific capacitance of the material prepared in comparative example 1 is 30F/g, has a low specific capacitance .

Fig. 6 is (a) cyclic voltammetry curve, (b) charge-discharge curve diagram of the material prepared in comparative example 2 of the present invention, it can be seen from the curve that the specific capacitance of the material prepared in comparative example 2 is 176F/g, which has a lower Specific capacitance.

Claims (5)

1. microwave prepares the method for porous carbon nanomaterial, it is characterized in that, concrete steps are as follows: Use the mixture of carbon powder and toluene with a mass ratio of 1:1 as the microwave reactant, mix the microwave reactant and potassium citrate at a mass ratio of 1:10-200, grind them, and then place them under 200-800W for microwave heating. After the reaction, cool naturally, wash, filter under reduced pressure and dry to obtain porous carbon nanomaterials; the microwave heating time is 60s; the carbon powder is selected from graphite, acetylene black or activated carbon. 2. The method according to claim 1, characterized in that the mass ratio of the microwave reactant to potassium citrate is 1:100-200. 3. The method according to claim 1, characterized in that, the grinding time is 10-20 minutes. 4. The method according to claim 1, characterized in that, the washing is sequentially washing with 10-50% dilute hydrochloric acid and water to remove impurities. 5. The method according to claim 1, characterized in that, the drying temperature is 50-100°C.