CN110963490B

CN110963490B - Method for preparing carbon nano hollow polyhedron by hydrothermal method

Info

Publication number: CN110963490B
Application number: CN201911372756.8A
Authority: CN
Inventors: 蔡强; 何永凯; 颜昊; 王煜
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2019-12-27
Filing date: 2019-12-27
Publication date: 2021-04-02
Anticipated expiration: 2039-12-27
Also published as: CN110963490A

Abstract

The invention discloses a method for preparing a carbon nanometer hollow polyhedron by a hydrothermal method, and belongs to the field of nanometer graphite preparation. The invention utilizes a chemical synthesis method, uses pyrene with a benzene ring structure as a raw material, and conducts the reaction under alkaline conditions and lower temperature, and the obtained reaction product has a high degree of graphitization, a large cavity volume, and potential light weight. high-strength characteristics. The invention has low energy consumption, short time consumption and high product quality, and the chemical synthesis method adopted by the invention is completely different from the prior art, and has innovation and novelty.

Description

Method for preparing carbon nano hollow polyhedron by hydrothermal method

Technical Field

The invention belongs to the field of nano-graphite preparation, and particularly relates to a method for preparing a carbon nano hollow polyhedron by using a hydrothermal method.

Background

Due to the size effect, the nano material has physical and chemical properties far superior to or not possessed by a macroscopic bulk material, and the performance of the nano material greatly depends on the shape, the size and the crystalline phase structure of the nano material. The hollow nano material is a unique nano structure with a hollow inner cavity and a continuous shell layer with nano-scale thickness. The structure can provide larger specific surface area, shorter charge diffusion/transmission length, additional guest material loading space, unique photoelectric transmission effect and the like, and has wide application prospect in the fields of energy, catalysis, photoelectric materials, drug transportation and the like. The graphite material has good chemical stability, thermal stability, electrical conductivity and thermal conductivity, and is widely applied to the fields of energy, catalysis, biomedical treatment and the like. The carbon hollow nano polyhedron combines the advantages of graphite and hollow nano structures, and is a functional nano material with novel structure and unique performance.

In the last thirty years, people carry out a great deal of research work on hollow nano polyhedral graphite nodules, and provide a plurality of different preparation methods. For example, diamond particles are treated at 1700 ℃ in a vacuum state and annealed to obtain nano onion-like fullerenes of about 5nm, and almost all of the nano onion-fullerenes are converted into polyhedral nano onion-fullerenes at 2000 ℃; immersing graphite electrode in deionized water, and generating electric arc when high-purity cathode is contacted with anode graphiteThe temperature is as high as 4000 ℃, carbon plasma is generated by thermal evaporation of the anode, and the product contains a large amount of hollow nano polyhedral graphite nodules; calcium carbide is used as raw material and AlCl is used₃Or NiCl₂Reacting in a stainless steel reaction kettle at 250-500 ℃ for 5h to obtain a large amount of hollow nano polyhedral graphite nodules with high graphitization degree; the method takes potatoes as raw materials and 30 percent (w/v) NaOH as a catalyst to react for 2 hours in a muffle furnace at 240 ℃ to obtain the irregular-shaped hollow nano polyhedral graphite nodule.

Although these prior art techniques can produce similar onion carbon or hollow polyhedral graphite spheres, they suffer from many problems, such as high energy consumption, thousands of temperatures required, or low graphitization of the product with limited performance improvements.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for preparing a carbon nano hollow polyhedron by a hydrothermal method.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention takes mesoporous carbon CMK-3 as a template and adopts a hydrothermal method to synthesize hollow nano polyhedral graphite nodules, and the method comprises the following steps:

(1) adding mesoporous carbon CMK-3 and 1,3, 6-trinitropyrene into NaOH solution according to the mass ratio of 3-7:5-15, placing the mixture into a polytetrafluoroethylene reaction kettle, heating to 240 ℃, and reacting for 10-24 h;

(2) filtering, cleaning and drying the reaction product by a filter membrane.

Further, before the mesoporous carbon CMK-3 used in the step (1) is used, oxidation treatment is carried out, namely, the mesoporous carbon CMK-3 is put into 0.8-1.2M ammonium persulfate solution prepared by deionized water, and is refluxed for 10-14h at the temperature of 55-65 ℃, filtered, washed and dried.

Further, before the mesoporous carbon CMK-3 used in the step (1) is used, oxidation treatment is carried out, namely, the mesoporous carbon CMK-3 is put into 0.8-1.2M ammonium persulfate solution prepared by 2M sulfuric acid, and is refluxed for 10-14h at the temperature of 55-65 ℃, filtered, washed and dried.

Further, 1-1.4M ammonia solution is used in the step (1) instead of NaOH solution.

Further, the ammonia aqueous solution concentration in the step (1) is 1.2M.

Further, the ammonium persulfate solution is 1M in concentration.

Further, the mass ratio of the mesoporous carbon CMK-3 to the 1,3, 6-trinitropyrene in the step (1) is 1: 2.

Further, the reaction temperature of the polytetrafluoroethylene reaction kettle in the step (1) is 200 ℃.

Further, in the step (1), the concentration of the NaOH solution is 0.2-1.5M.

Further, the reflux temperature of the mesoporous carbon CMK-3 during the oxidation treatment is 60 ℃, and the time is 12 hours.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention adopts a hydrothermal method, can complete the reaction at a lower temperature (160-;

(2) the principle of the invention is a chemical synthesis method, which takes pyrene with a benzene ring structure as a raw material to react under an alkaline condition. The prior art relies on high temperature or metal catalysis, using different carbon sources, to achieve the preparation of products by morphological transformation of carbon. The chemical synthesis method adopted by the invention is completely different from the prior art and has innovation and novelty.

(3) The reaction product has high graphitization degree, large cavity volume and potential light weight and high strength. The products prepared by the prior art are often onion-shaped, the cavity volume is small, and the graphitization degree is obviously lower than that of the products prepared by the method.

(4) The method has the advantages of low energy consumption, short time consumption and high product quality, and is pioneering work.

Drawings

FIG. 1 is a high-resolution electron microscope photograph of the nano onion carbon in comparative example 1.

Fig. 2 is a general TEM image of a carbon nano hollow polyhedron in example 1.

Fig. 3 is an HRTEM of a carbon nano hollow polyhedron in example 1.

Fig. 4 is an SEM image of a carbon nano hollow polyhedron in example 1.

Fig. 5 is a general TEM image of a carbon nano hollow polyhedron in example 2.

Fig. 6 is a general TEM image of a carbon nano hollow polyhedron in example 5.

Fig. 7 is a general TEM image of a carbon nano hollow polyhedron in example 6.

Fig. 8 is a general TEM image of a carbon nano hollow polyhedron in example 7.

Detailed Description

Comparative example 1

The high-temperature high-pressure preparation method of the nano onion carbon comprises the following steps: pressing and molding diamond powder with the average particle size of 2-50 nanometers by using a hydraulic machine, and then loading a sample into the synthesis cavity; the graphite pipe is adopted for heating in the assembly cavity, pyrophyllite is used as a heat insulation material, hexagonal boron nitride is used for protecting the cavity, the synthesis pressure is 1.0-5.2 GPa, the synthesis temperature is 1273-1773K, the heat insulation and pressure maintaining time is 1-90 minutes, the sample is naturally cooled to room temperature after the heating is stopped and then is released, the nano onion carbon core internally wrapped with diamond prepared under the condition is nano diamond, the shell is a graphite sphere layer, and a high-resolution electron microscope picture is shown in figure 1.

Example 1

In the embodiment, mesoporous carbon CMK-3 is used as a template and a hydrothermal method is adopted to synthesize hollow nano polyhedral graphite nodules, and the method comprises the following steps:

(1) preparing an ammonium persulfate solution by using a 2M sulfuric acid solution, adding 0.5g of mesoporous carbon CMK-3 into 30mL of the solution, stirring and refluxing for 12h at 60 ℃, washing the mesoporous carbon CMK-3 for multiple times by using deionized water and ethanol, filtering, and drying for more than 6h at 60 ℃ for later use, wherein the final concentration of the ammonium persulfate is 1M;

(2) grinding 0.5g of pyrene, adding the ground pyrene into 40mL of concentrated nitric acid, stirring and refluxing for 10h at 80 ℃, washing with deionized water and ethanol, filtering, and drying for more than 6h at 60 ℃ to obtain 1,3, 6-trinitropyrene;

(3) adding 30.05 g of oxidized CMK prepared in the step (1) and 0.1g of 1,3, 6-trinitropyrene prepared in the step (2) into 50ml of 0.2M NaOH solution, fully carrying out ultrasonic crushing, heating to 200 ℃ in a polytetrafluoroethylene reaction kettle, and reacting for 10 hours;

(4) filtering the reaction product with 0.2 μm filter membrane, washing with water and ethanol for several times, drying at 60 deg.C for more than 6 hr.

The common TEM image, HRTEM image and SEM image of the hollow nano-polyhedral graphite sphere prepared in this example are shown in fig. 2-4, respectively, after detection. As can be seen from FIGS. 2-4, the product prepared in this example agglomerated into a mass that was relatively large; meanwhile, the hollow structure is clear, the cavity proportion is large, and the theoretical density is low; the graphitization degree of the shell layer is high, good parallel state is kept among layers, and the theoretical hardness is high.

Compared with the embodiment, the method adopted in the comparative example 1 has the advantages of high raw material cost, high preparation temperature and high pressure, high equipment requirement, high risk, unclear shell structure of the prepared product, poor graphitization degree and no particularly prominent morphological feature.

Example 2

(1) the same as the step (1) in example 1;

(2) the same as the step (2) in example 1;

(3) adding 30.05 g of oxidized CMK prepared in the step (1) and 0.1g of 1,3, 6-trinitropyrene prepared in the step (2) into 50ml of 1.2M ammonia water solution, heating the mixture to 200 ℃ in a polytetrafluoroethylene reaction kettle after full ultrasonic crushing, and reacting for 10 hours;

(4) the same procedure as in step (4) of example 1.

The hollow nano polyhedral graphite sphere prepared in this example is detected, and its general TEM image is shown in fig. 5.

Example 3

(1) preparing 1M ammonium persulfate solution by using deionized water, adding 0.5g of mesoporous carbon CMK-3 into 30mL of the solution, stirring and refluxing for 12h at 60 ℃, and then washing, filtering and drying for later use;

(2) the same as the step (2) in example 1;

(3) the same as the step (3) in example 1;

(4) the same procedure as in step (4) of example 1.

Example 4

(1) grinding 0.5g of pyrene, adding the ground pyrene into 40mL of concentrated nitric acid, stirring and refluxing for 10 hours at 80 ℃, washing, filtering and drying to obtain 1,3, 6-trinitropyrene;

(2) adding 0.05g of CMK-3 and 0.1g of 1,3, 6-trinitropyrene obtained in the step (1) into 50mL of 0.2M NaOH solution, carrying out sufficient ultrasonic crushing, heating to 200 ℃ in a polytetrafluoroethylene reaction kettle, and reacting for 10 hours;

(3) the reaction product was filtered, washed and dried using a 0.2 μm filter.

Example 5

The NaOH solution concentration in this example was 0.5M, and the other procedures were the same as in example 1.

The hollow nano polyhedral graphite sphere prepared in this example is detected, and its general TEM image is shown in fig. 6.

Example 6

The NaOH solution concentration in this example was 1M, and the other procedures were the same as in example 1.

The hollow nano polyhedral graphite sphere prepared in this example is detected, and its general TEM image is shown in fig. 7.

Example 7

The NaOH solution concentration in this example was 1.5M, and the other procedures were the same as in example 1.

The hollow nano polyhedral graphite sphere prepared in this example is detected, and its general TEM image is shown in fig. 8.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. a method utilizing hydrothermal method to prepare carbon nanometer hollow polyhedron, is characterized in that, described method comprises the steps:

(1) The mesoporous carbon CMK-3 and 1,3,6-trinitropyrene were added to the NaOH solution according to the mass ratio of 3-7:5-15, and the above mixture was placed in a polytetrafluoroethylene reactor for heating To 160-240 ℃, reaction 10-24h;

(2) The reaction product is filtered, washed and dried through a filter membrane.

2. The method for preparing carbon nano-hollow polyhedron by hydrothermal method according to claim 1, wherein the mesoporous carbon CMK-3 used in the step (1) is to be oxidized before being used, that is, the mesoporous carbon CMK-3 was put into 0.8-1.2M ammonium persulfate solution prepared with deionized water, refluxed at 55-65°C for 10-14h, filtered, washed and dried.

3. The method according to claim 1, wherein the mesoporous carbon CMK-3 used in the step (1) is to be oxidized before being used, that is, the mesoporous carbon CMK-3 was put into 0.8-1.2M ammonium persulfate solution prepared with 2M sulfuric acid, refluxed at 55-65°C for 10-14h, filtered, washed and dried.

4 . The method according to claim 3 , wherein the 1-1.4M ammonia solution is used instead of the NaOH solution in the step (1). 5 .

5 . The method according to claim 4 , wherein the concentration of the aqueous ammonia solution in the step (1) is 1.2M. 6 .

6 . The method for preparing a carbon nanometer hollow polyhedron by a hydrothermal method according to claim 2 , wherein the concentration of the ammonium persulfate solution is 1M. 7 .

7. The method for preparing carbon nano-hollow polyhedron by hydrothermal method according to any one of claims 1-5, wherein the step (1) mesoporous carbon CMK-3 and 1,3,6- The mass ratio of trinitropyrene was 1:2.

8. according to the method for preparing carbon nano hollow polyhedron by hydrothermal method according to any one of claim 1-5, it is characterized in that, in described step (1), the reaction temperature of polytetrafluoroethylene reactor is 200 ℃ .

9 . The method for preparing a carbon nano-hollow polyhedron by a hydrothermal method according to claim 1 , wherein in the step (1), the concentration of the NaOH solution is 0.2-1.5M. 10 .

10. The method for preparing a carbon nano-hollow polyhedron by a hydrothermal method according to any one of claims 2-5, wherein the reflux temperature when the mesoporous carbon CMK-3 is oxidized is 60°C, The time is 12h.