CN108658064B

CN108658064B - Nitrogen-doped graphene and preparation method thereof

Info

Publication number: CN108658064B
Application number: CN201810897074.8A
Authority: CN
Inventors: 王超; 肖祥; 钟国彬; 徐凯琪; 伍世嘉; 赵伟; 卢锡洪; 冯浩槟
Original assignee: Guangdong Power Grid Co Ltd; Electric Power Research Institute of Guangdong Power Grid Co Ltd
Current assignee: Guangdong Power Grid Co Ltd; Electric Power Research Institute of Guangdong Power Grid Co Ltd
Priority date: 2018-08-08
Filing date: 2018-08-08
Publication date: 2021-07-30
Anticipated expiration: 2038-08-08
Also published as: CN108658064A

Abstract

The invention relates to the field of nano materials, in particular to nitrogen-doped graphene and a preparation method thereof. The invention provides a preparation method of nitrogen-doped graphene, which comprises the following steps: step 1: carrying out electrochemical intercalation on graphite to obtain expanded graphite; step 2: and mixing the expanded graphite with a nitrogen source, heating to 100-800 ℃, and annealing to obtain the nitrogen-doped graphene. The invention also provides the nitrogen-doped graphene prepared by the method. The nitrogen-doped graphene and the preparation method thereof provided by the invention solve the technical problems of higher cost, complex preparation process, lower purity and poorer performance of the prepared graphene material in the existing graphene preparation method.

Description

Nitrogen-doped graphene and preparation method thereof

Technical Field

The invention relates to the field of nano materials, in particular to nitrogen-doped graphene and a preparation method thereof.

Background

Graphene is a single-atom graphite material, and the crystal lattice of the graphene is a two-dimensional honeycomb structure formed by carbon atoms. In 2004, people obtain few graphene sheet layers for the first time by a mechanical stripping method, and find that the graphene sheet layers have unique chemical structures and excellent performance. Graphene, now known as "black gold", is considered to be a novel material with great development prospect in the 21 st century. In recent decades, scientists in all countries around the world have made a lot of researches on graphene, so that graphene can be applied to the fields of semiconductors, solar cells, batteries, sensors and the like.

However, the following problems still exist in the graphene: firstly, the graphene preparation process is complex, the cost is high, and the large-scale production is difficult; secondly, at present, a plurality of manufacturers for preparing graphene exist at home, but the product quality is good and uneven, the consistency is poor, and a unified and standardized preparation process is lacked; third, product design for supercapacitor applications is lacking. Aiming at the preparation process of graphene, the currently common preparation method is a chemical oxidation method, which comprises the steps of oxidizing carbon nanospheres by using a Hummers method to obtain graphene oxide, and then carrying out high-temperature thermal reduction and drying to obtain graphene. In addition, there is a chemical vapor deposition method, which generally uses plasma chemical vapor deposition to prepare graphene, and specifically, a metal catalyst film is plated on a substrate, and the film is placed in a reaction chamber of a chemical vapor deposition apparatus, and a graphene material is obtained through high-temperature catalytic growth. The graphene prepared by the method has high quality and purity, but the preparation process is complex, the requirement on instruments and equipment is high, and the cost is expensive. The above-mentioned methods only disclose a method for preparing graphene. Therefore, the existing method for preparing graphene has high cost and complex preparation process, and the prepared graphene material has low purity and poor performance, which is a technical problem to be solved urgently by technical personnel in the field.

Disclosure of Invention

The invention provides nitrogen-doped graphene and a preparation method thereof, and solves the technical problems that the existing method for preparing graphene is high in cost and complex in preparation process, and the prepared graphene material is low in purity and poor in performance.

The invention provides a preparation method of nitrogen-doped graphene, which comprises the following steps:

step 1: carrying out electrochemical intercalation on graphite to obtain expanded graphite;

step 2: and mixing the expanded graphite with a nitrogen source, heating to 100-800 ℃, and annealing to obtain the nitrogen-doped graphene.

Preferably, the voltage of the electrochemical intercalation is 2-15V.

Preferably, the time of the electrochemical intercalation is 30-120 min.

Preferably, the electrochemical intercalation method specifically comprises: and (3) applying voltage between the positive electrode and the negative electrode by taking graphite carbon paper as a positive electrode, taking metal platinum or graphite as a negative electrode and taking mixed acid as electrolyte to obtain the expanded graphite.

Preferably, the mixed acid is any two of sulfuric acid, nitric acid, acetic acid, phosphoric acid, benzoic acid and benzenesulfonic acid.

Preferably, the thickness of the graphite carbon paper is 0.2-5 mm.

Preferably, the step 2 specifically comprises heating the expanded graphite to 100-800 ℃ in an atmosphere containing nitrogen gas, and annealing to obtain nitrogen-doped graphene;

the nitrogen-containing gas comprises ammonia gas, nitrogen gas or a mixture of the ammonia gas and the nitrogen gas.

Preferably, the step 2 specifically comprises mixing the expanded graphite with a nitrogen precursor source, heating to 100-800 ℃ in an argon atmosphere, and annealing to obtain nitrogen-doped graphene;

the nitrogen precursor source includes one or more of urea, melamine, aniline, pyrrole, and an amino acid.

Preferably, the annealing time is 1-10 h.

The invention also provides nitrogen-doped graphene prepared by the preparation method of the nitrogen-doped graphene.

According to the preparation method provided by the invention, the nitrogen atoms are adopted to dope the graphene, so that the defect degree of the graphene material is effectively increased, the higher the defect degree of the graphene material is, the higher the ion mobility of the graphene material in the energy storage process is, and the specific capacity of the graphene material can be effectively improved. The preparation method adopted by the invention is simple and quick, is convenient to operate, can save cost and improve benefit. Is easy to realize large-scale production. In addition, the preparation method adopts an electrochemical intercalation method to prepare, so that the electrolyte can be recycled, and the preparation method is environment-friendly and saves the production cost. The nitrogen-doped graphene prepared by the preparation method provided by the invention has a thin-layer structure, not only successfully dopes nitrogen atoms to introduce pseudo-capacitance, but also has higher defect degree, so that the specific capacitance of the nitrogen-doped graphene is far superior to that of the existing graphene material

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

FIG. 1 is a schematic diagram of electrochemical intercalation in an embodiment of the present invention;

fig. 2 is an SEM image of nitrogen-doped graphene prepared in example 1 of the present invention;

fig. 3 is an XPS curve of nitrogen-doped graphene prepared in example 1 of the present invention;

fig. 4 is a raman spectrum of nitrogen-doped graphene prepared in example 1 of the present invention;

fig. 5 is a comparison graph of cyclic voltammetry curves of conventional graphene and nitrogen-doped graphene prepared in example 1 of the present invention;

wherein the reference numbers are as follows:

A. a positive electrode; B. a negative electrode; C. and (3) an electrolyte.

Detailed Description

The embodiment of the invention provides nitrogen-doped graphene and a preparation method thereof, and solves the technical problems that the existing method for preparing graphene is high in cost and complex in preparation process, and the prepared graphene material is low in purity and poor in performance.

In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The nitrogen-doped graphene and the preparation method thereof provided by the embodiment of the invention are further described below.

Example 1:

step 1: as shown in figure 1, graphite carbon paper with the thickness of 1mm is used as a positive electrode A, a platinum wire is used as a negative electrode B, mixed acid is used as electrolyte C, 2V voltage is applied between the two electrodes, electrochemical intercalation is carried out for 30min, the product is washed to be neutral, and the expanded graphite is obtained by drying.

Step 2: and (3) placing the expanded graphite carbon obtained in the step (1) in an ammonia atmosphere, heating to 700 ℃, and carrying out annealing reaction for 1h to obtain the nitrogen-doped graphene.

The prepared nitrogen-doped graphene is subjected to capacitance performance test, and the test result in figure 5 shows that the material has the volume of 100mVs^-1Next, the specific capacitance was 55.73F/g.

Examples 2 to 6 and comparative examples 1 to 6

Based on the scheme of the embodiment 1, the embodiments 2 to 6 and the comparative examples 1 to 6 are obtained by regulating different reaction conditions, and the specific reaction parameters and performances are shown in table 1:

TABLE 1 reaction parameters and Properties of examples 2-6 and comparative examples 1-6

From the results of example 1 and table 1, it is seen that the nitrogen-doped graphene material prepared in example 1 has the best performance and good capacitance characteristics. Through calculation, the sweep rate of the graphene material is 100mVs^-1The capacitance value was 55.73F/g. Fig. 2 is an SEM image of the nitrogen-doped graphene prepared in example 1, and it can be seen from fig. 2 that the material has a thin-layer structure, which is beneficial to increase of the specific surface area, thereby further improving the specific capacitance. Fig. 3 is an XPS curve of the nitrogen-doped graphene prepared in example 1, and as can be seen from fig. 3, the XPS curve of the processed graphene shows a signal of pyridine N, which indicates that nitrogen atoms are successfully doped after ammonia gas treatment, so that a pseudocapacitance is introduced, and the capacity of the material is improved. Fig. 4 is a raman spectrum of the nitrogen-doped graphene prepared in example 1, in which a D peak represents a defect degree, a G peak represents an order degree of the graphene, and an intensity ratio of the D peak to the G peak represents a defect degree of the graphene, and it can be seen from fig. 4 that I of the upper nitrogen-doped graphene is compared with I of the lower graphite paper_D/I_GThe value (═ 0.83) increased significantly, and the defect level became high. Fig. 5 is a comparison graph of cyclic voltammetry curves of the existing graphene and the nitrogen-doped graphene prepared in embodiment 1 of the present invention, in which a solid line is the cyclic voltammetry curve of the existing graphene, and a dotted line is the cyclic voltammetry curve of embodiment 1 of the present invention, and it can be seen from the graph that the current density corresponding to the nitrogen-doped graphene is significantly increased, and a calculation result shows that the capacity of the processed graphene is increased by 10 times.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of nitrogen-doped graphene is characterized by comprising the following steps:

step 2: heating the expanded graphite to 100-800 ℃ in the atmosphere of ammonia gas, and annealing to obtain nitrogen-doped graphene;

the electrochemical intercalation method specifically comprises the following steps: applying voltage between the positive electrode and the negative electrode by taking graphite carbon paper as a positive electrode, taking metal platinum or graphite as a negative electrode and taking mixed acid as electrolyte to obtain the expanded graphite;

the mixed acid is any two of sulfuric acid, nitric acid, acetic acid, phosphoric acid, benzoic acid and benzenesulfonic acid.

2. The preparation method of nitrogen-doped graphene according to claim 1, wherein the voltage of the electrochemical intercalation is 2-15V.

3. The preparation method of nitrogen-doped graphene according to claim 1, wherein the time for electrochemical intercalation is 30-120 min.

4. The preparation method of nitrogen-doped graphene according to claim 1, wherein the thickness of the graphite carbon paper is 0.2-5 mm.

5. The method for preparing nitrogen-doped graphene according to any one of claims 1 to 4, wherein the annealing time is 1 to 10 hours.

6. The nitrogen-doped graphene is characterized by being prepared by the preparation method of the nitrogen-doped graphene as claimed in any one of claims 1 to 5.