WO2016065839A1

WO2016065839A1 - Method for preparing graphene with three-dimensional porous structure

Info

Publication number: WO2016065839A1
Application number: PCT/CN2015/075636
Authority: WO
Inventors: 郑玉婴; 汪晓莉
Original assignee: 福州大学
Priority date: 2014-10-27
Filing date: 2015-04-01
Publication date: 2016-05-06
Also published as: CN104261403B; CN104261403A

Abstract

The present invention provides a method for preparing graphene with a three-dimensional porous structure. A uniform dispersion liquid is formed under the electrostatic interaction of a polystyrene template and graphene oxide, then the polystyrene template is removed through high-temperature calcination, and graphene with a three-dimensional porous structure is obtained after thermal reduction. According to the present invention, polystyrene spheres are taken as the template, and the pore size in the graphene can be effectively controlled in a manner of controlling the particle size of the polystyrene spheres; and the graphene is prepared by using a calcination reduction method, so that the problems of use of a poisonous chemical reagent and graphene agglomeration in a chemical reduction process can be avoided, and the porous structure of the graphene after calcination is firmer.

Description

Method for preparing three-dimensional porous structure graphene

Technical field

The invention belongs to the technical field of materials, and in particular relates to a method for preparing graphene having a three-dimensional pore structure.

Background technique

Graphene is another novel carbon allotrope after the discovery of fullerenes and carbon nanotubes. It has a unique atomic structure and electronic structure, which makes it exhibit many extraordinary properties that traditional materials do not have. Its theoretical specific surface area, good electrical and thermal conductivity, excellent mechanical properties and optical properties have become the choice of a new generation of supercapacitor electrode materials. However, the two-dimensional graphene material has its limitations as a supercapacitor electrode material, such as low coulombic efficiency for the first time, rapid decay during charge and discharge, and easy aggregation of graphene, and the actual specific surface area is much lower than the theoretical specific surface area. It is necessary to effectively design its microstructure from a molecular scale. The 3D porous graphene retains the superior intrinsic properties of two-dimensional graphene, and has a higher specific surface area. A large number of pore-shaped channels facilitate the rapid movement of electrons and ions, and the pore-like structure can relieve internal pressure and protect the electrode from Physical damage.

Summary of the invention

The object of the present invention is to provide a method for preparing graphene having a three-dimensional pore structure, and the obtained three-dimensional pore structure graphene can significantly improve the specific surface area and electrochemical performance of graphene. The preparation of graphene by the calcination reduction method of the invention effectively avoids the problem of toxic chemical reagents and graphene agglomeration used in the chemical reduction process, and the pore structure of the graphene after calcination is more firm.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for preparing a three-dimensional porous structure graphene, which comprises styrene monomer as raw material and potassium persulfate as initiator to prepare polystyrene nanospheres; ultrasonically mixes graphene oxide with polystyrene beads to adjust solution The pH is uniformly dispersed by electrostatic action. After drying, the mixture is calcined at a high temperature to remove polystyrene, and the graphene oxide is thermally reduced to obtain a graphene having a three-dimensional pore structure.

The preparation method of the three-dimensional porous structure graphene, the specific steps are as follows:

(1) Preparation of polystyrene nanospheres:

At room temperature, remove the air from the three-necked bottle with nitrogen, add deionized water, styrene monomer, continue to remove the air in the solution by nitrogen, magnetically stir for 20-40 min; gradually increase the temperature to 30-90 ° C, The initiator potassium persulfate is dissolved in deionized water, and then added to the three-necked bottle at one time, the reaction is continued for 10 to 24 hours, and centrifugally dried to obtain a polystyrene pellet;

(2) Preparation of three-dimensional pore structure graphene:

The graphene oxide is formulated into a solution at a concentration of 2 to 5 g/L, and the polystyrene beads and the graphene oxide are ultrasonically mixed for 2 to 3 hours. The colloidal particles are adjusted to adjust the pH of the solution to 6-8, so that the polystyrene nanospheres are uniformly dispersed in the thin graphite oxide. After being filtered and dried, the pyrolysis polystyrene beads are calcined at a high temperature in a nitrogen atmosphere and the graphite oxide is thermally reduced. Dilute, a graphene having a three-dimensional pore structure is obtained.

The volume ratio of deionized water to styrene monomer in the step (1) is 10:0.5 to 3, and the mass of the initiator is 0.2% to 1% by mass of the styrene monomer.

The mass ratio of polystyrene to graphene oxide in the step (2) is 2 to 5:1; the temperature of the high temperature calcined pyrolysis polystyrene pellet is 300 to 550 ° C, and the calcination time is 1 to 2 h; The reduced temperature of the reduced graphite oxide is 700 to 900 ° C, the calcination time is 2 to 3 h, and the heating rate is 5 to 10 ° C / min.

The preparation process of graphene oxide is:

First, the concentrated sulfuric acid and phosphoric acid are added into the three-necked bottle in a certain proportion. As for the low-temperature water bath, the magnetic stirring is carried out for 10 to 60 minutes, the natural flake graphite is added, and the potassium permanganate is slowly added, and the ice water bath below 10 ° C is kept for 30-60 min; Then move to the oil bath pot for mechanical stirring for 6 ~ 12h, the reaction temperature is controlled at 40 ~ 80 ° C; the reaction product is diluted with ionized water, then slowly add hydrogen peroxide to golden brown and no bubbles are formed; then wash with dilute hydrochloric acid and deionized water To neutral, after drying, graphite oxide is obtained; graphite oxide is ultrasonically stripped into graphene oxide at room temperature.

The three-dimensional porous structure of graphene is used to prepare a supercapacitor electrode material.

The significant advantages of the present invention are:

The template method can control the pore size; the high temperature calcination removes the template while reducing the graphene oxide, and the steps are simple; the calcination reduction method for preparing the graphene effectively avoids the toxic chemical reagent used in the chemical reduction process and the graphene agglomeration problem, and after calcination The pore structure of graphene is more robust.

DRAWINGS

1 is an XRD pattern of graphene obtained in Example 1 and Example 2, wherein (1) represents the product of Example 1, and (2) represents the product of Example 2;

2 is a graph showing the adsorption and desorption of graphene obtained in Example 1;

3 is a graph showing a pore size distribution of graphene obtained in Example 1;

4 is a graph showing the adsorption and desorption of graphene obtained in Example 2;

Figure 5 is a graph showing the pore size distribution of graphene obtained in Example 2;

6 is a charge and discharge diagram of graphene obtained in Example 1 and Example 2, in which (1) represents the product of Example 1, and (2) represents the product of Example 2.

detailed description

The invention is further illustrated by the following specific examples of the invention, but the invention is not limited thereto.

Example 1

(1) Firstly, the modified Hummers method was used to prepare graphite oxide; then, 90 mL of deionized water and 9 mL of styrene monomer were added to the three-necked flask, and the air in the solution was continuously removed by nitrogen, magnetically stirred for 30 min; the temperature was gradually increased to 70. °C, adding 0.03g / mL potassium persulfate 10mL; continue the reaction for 24h, centrifugal drying to obtain polystyrene beads;

(2) Ultrasonic stripping of the graphite oxide prepared above into a graphene oxide at room temperature, the concentration is 5 g / L, polystyrene beads and graphene oxide are added to the above solution in a mass ratio of 3:1, and ultrasonically mixed for 2 hours to form colloidal particles. Adjusting pH=8, the polystyrene nanospheres are uniformly dispersed in the thin graphite oxide, and after being filtered and dried, the thermally decomposed polystyrene beads are calcined at a high temperature in a nitrogen atmosphere and the graphite oxide is thermally reduced to obtain a three-dimensional pore structure. Graphene.

Example 2

The polystyrene pellet template was not added as a comparative test, and the same procedure was used to prepare graphene by a thermal reduction method. Firstly, the improved Hummers method was used to prepare graphite oxide, and then the graphite oxide was ultrasonically stripped into graphene oxide at room temperature at a concentration of 5 g/L, and then ultrasonicated for 2 h to adjust pH=8. After drying by suction filtration, it is calcined at a high temperature in a nitrogen atmosphere, and the graphite oxide is thermally reduced to obtain graphene.

In the experiment, we compared the effect of the template method and the template method on the specific surface area, pore size and specific capacitance of graphene. It was found that the specific surface area and specific capacitance of graphene were significantly improved after using the template method, and the average pore size distribution also occurred. A big change.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should fall within the scope of the present invention.

Claims

A preparation method of three-dimensional porous structure graphene, characterized in that: styrene monomer is used as raw material, potassium persulfate is used as initiator to prepare polystyrene nanospheres; and graphene oxide and polystyrene beads are ultrasonicated Mixing, adjusting the pH of the solution, uniformly dispersing the two by electrostatic action, drying, then calcining the mixture at a high temperature to remove polystyrene, and thermally reducing the graphene oxide to obtain a graphene having a three-dimensional pore structure.
The method for preparing a three-dimensional porous structure graphene according to claim 1, wherein the specific steps are:

(1) Preparation of polystyrene nanospheres: at room temperature, the air in the three-necked flask is removed by nitrogen, and then deionized water and styrene monomer are added, and the air in the solution is continuously removed by nitrogen, and magnetically stirred for 20 to 40 minutes; The temperature is gradually increased to 30-90 ° C, the initiator potassium persulfate is dissolved in deionized water, and then added to the three-necked bottle at one time, the reaction is continued for 10 to 24 hours, and centrifugally dried to obtain a polystyrene pellet;

(2) Preparation of three-dimensional pore structure graphene: The graphene oxide is formulated into a solution at a concentration of 2 to 5 g/L, and the polystyrene beads and the graphene oxide are ultrasonically mixed for 2 to 3 hours to form colloidal particles, and the pH of the solution is adjusted. From 6 to 8, the polystyrene nanospheres are uniformly dispersed in the graphite oxide thinner, and after being filtered and dried, the thermally decomposed polystyrene beads are calcined at a high temperature in a nitrogen atmosphere and the graphite oxide is thermally reduced to obtain a three-dimensional pore structure. Graphene.
The method for preparing a three-dimensional porous structure graphene according to claim 2, wherein the volume ratio of the deionized water to the styrene monomer in the step (1) is 10:0.5 to 3, and the mass of the initiator It is 0.2% to 1% of the mass of the styrene monomer.
The method for preparing a three-dimensional porous structure graphene according to claim 2, wherein the mass ratio of polystyrene to graphene oxide in the step (2) is 2 to 5:1; high temperature calcination thermal decomposition polymerization The temperature of the styrene pellet is 300-550 ° C, the calcination time is 1-2 h; the temperature of the high-temperature thermal reduction graphite oxide is 700-900 ° C, the calcination time is 2-3 h, and the heating rate is 5-10 ° C/min.