CN112960670A

CN112960670A - Edge hydroxylation modified graphene and preparation method thereof

Info

Publication number: CN112960670A
Application number: CN202110440808.1A
Authority: CN
Inventors: 张贺新; 韩威; 闫鑫; 解翰林; 吴俊杰; 从冉; 夏友谊; 林鹏; 高宏; 宋志健
Original assignee: Anhui University of Technology AHUT
Current assignee: Anhui University of Technology AHUT
Priority date: 2021-04-23
Filing date: 2021-04-23
Publication date: 2021-06-15

Abstract

The invention discloses an edge hydroxylation modified graphene technology, wherein the edge of the modified graphene has rich hydroxyl functional groups, so that the dispersibility of the graphene in a polar solvent can be obviously improved. According to the invention, the organic compound containing boron-hydrogen (B-H) bonds and the active double bonds at the edge of the graphene are subjected to hydroboration-oxidation reaction to form the graphene with hydroxyl at the edge. The preparation method of the modified graphene has the advantages of simple process, no special requirements on equipment, low cost, high efficiency, easiness in industrial production and the like.

Description

Edge hydroxylation modified graphene and preparation method thereof

Technical Field

The invention relates to the technical field of graphene modification, in particular to edge hydroxylation modified graphene and a preparation method thereof.

Background

Graphene (Graphene) is a two-dimensional carbon nanomaterial consisting of carbon atoms in a hexagonal honeycomb lattice with sp2 hybridized orbitals. Graphene has an ideal lattice structure and unique properties of optics, electricity, heat, mechanics and the like, has a wide application prospect in the fields of electronic devices, energy storage devices, biological and chemical sensors, composite materials and the like, and is considered to be a revolutionary material in the future.

Common methods for producing graphene powder can be classified into chemical methods and physical methods in a macroscopic view. The chemical method mainly comprises the steps of oxidizing graphite by a strong acid strong oxidant, peeling the graphite to prepare graphene oxide, and finally carrying out reduction treatment to obtain the graphene. Because the structure of the graphene sheet layer can be seriously damaged in the strong oxidation process, although the electronic conjugated structure of the graphene sheet layer is partially recovered after reduction treatment, various performance indexes of the obtained graphene material still have great difference with high-quality graphene. In addition, a large amount of strong acid oxidants such as concentrated sulfuric acid, concentrated nitric acid, potassium permanganate and the like are usually required in the oxidation process of graphite, and high-temperature treatment or use of toxic chemical substances such as hydrazine hydrate, sodium borohydride and the like in the reduction process of graphite, so that the energy consumption is high, the efficiency is low, the cost is high, and the environment is polluted. The physical method for preparing the graphene is environment-friendly in process, low in cost, few in product defects, excellent in electric and thermal conductivity, good in stability and high in mechanical strength, and is the best method for preparing the graphene from the perspective of sustainable development. However, the graphene prepared by a physical method has no polar group, has relatively poor compatibility with a polymer, is difficult to apply to fields such as polymer functionalization and the like, has a great limitation on the thickness of the obtained graphene lamellar layer, and is difficult to prepare a thinner graphene lamellar layer structure. Therefore, the development of the graphene preparation process which has excellent compatibility and conductivity, is simple and feasible, has low cost, high efficiency and small pollution and is easy to implement on a large scale has important significance. Based on the above problems, the preparation of modified graphene has become a research hotspot of a great number of graphene researchers at present, but the existing modification process usually damages the original structure of graphene, thereby greatly reducing the electrical conductivity of graphene. In the prior art, graphite and alkali metal solid are continuously ball-milled in a high-energy ball mill, and low-frequency high-voltage pulse current is applied to graphene dispersed in water to obtain hydroxylated graphene. However, the use of a high-energy ball mill requires a long time for grinding, and the energy consumption is large.

Disclosure of Invention

In view of the above, the invention is based on that the graphene edge has a large number of active double bonds, and the graphene edge containing hydroxyl groups is formed by performing a hydroboration-oxidation reaction on an organic compound containing a boron-hydrogen (B-H) bond and the active double bonds at the graphene edge. The preparation method of the modified graphene has the advantages of simple process, no special requirements on equipment, low cost, high efficiency, easiness in industrial production and the like.

The invention relates to a preparation method of edge hydroxylation modified graphene.

In the above preparation method, preferably, the modifying agent is a boron hydride compound, and the oxidizing agent is a peroxide. Such boron hydrides include, but are not limited to, borane, diborane, borane, pentaborane, trimethylamine borane, dimethylamine borane, tetramethylamine borohydride, N, N-diethylaniline borane, borane dimethylsulfide complex, 2-methylpyridine borane, diethyl (3-pyridine) borane, borane tetrahydrofuran complex, borane triphenylphosphine complex, borane pyridine complex, and the like. The peroxides include, but are not limited to, hydrogen peroxide, benzoyl peroxide, m-chloroperoxybenzoic acid, and the like.

In the above preparation method, preferably, the weight ratio of the graphene to the boron hydride is 100: 1-1000, more preferably 100: 5-1000, most preferably 100: 8-100.

In the above preparation method, the post-treatment preferably includes the steps of standing, filtering, washing, and drying.

In the above-mentioned production method, the temperature of the modification reaction and the oxidation reaction is preferably controlled to 40 to 300 ℃.

In the above preparation method, ultrasonic dispersion is preferably used in the modification reaction and oxidation reaction processes. The reaction system can be a solvent-free system, water or an organic solvent.

According to the edge-hydroxylated modified graphene obtained by the invention, the edge of the modified graphene contains a large number of hydroxyl functional groups, so that the dispersibility of the graphene in a polar solvent can be obviously improved. The modification of graphene is carried out based on a hydroboration-oxidation reaction, and the mechanism is shown in the following figure:

the hydroboration-oxidation reaction of graphene occurs at the active double bond at the edge of graphene, as shown in the following figure, the double bond marked by the elliptic dotted line is an active double bond:

according to the method, based on the fact that the graphene edge has a large number of active double bonds, the organic compound containing boron-hydrogen (B-H) bonds and the active double bonds on the edge of the graphene are subjected to hydroboration-oxidation reaction to form the graphene with hydroxyl on the edge. The preparation method of the modified graphene has the advantages of simple process, no special requirements on equipment, low cost, high efficiency, easiness in industrial production and the like.

Drawings

Fig. 1 shows the infrared spectra of graphene before and after modification.

FIG. 2 is an SEM electron micrograph and EDS elemental analysis of the corresponding sites.

Fig. 3 is a dispersion experiment control of graphene before and after modification.

Detailed Description

The following examples are further illustrative of the present invention as to the technical content of the present invention, but the essence of the present invention is not limited to the following examples, and one of ordinary skill in the art can and should understand that any simple changes or substitutions based on the essence of the present invention should fall within the protection scope of the present invention.

Example 1

5g of graphene (Wanhe alkene new material, D90:10 μm) is added into a 250ml reactor, 100ml of distilled water is added, and the obtained mixture is placed into an ultrasonic dispersion device for ultrasonic dispersion for 30 min. 5ml of 10 percent aqueous solution of dimethylamine borane (Lesan chemical) is added into a beaker, the reactor is sealed, and the dispersion is continued in an ultrasonic dispersion device for 2 hours at the reaction temperature of 40 ℃. Adding 10ml (30 mass percent) of hydrogen peroxide solution into a beaker, sealing the reactor, reacting at the temperature of 40 ℃, and continuously dispersing in an ultrasonic dispersing device for 1 hour.

And filtering the mixture in the beaker (a filter membrane of 5 mu m), washing the mixture with distilled water for three times, and drying the mixture in an air-blast drying oven at 100 ℃ to obtain the high-dispersity graphene, wherein the oxygen content in the graphene is detailed in table 1.

The washed and dried modified graphene is put into a glass bottle, added with water and stirred for 2 hours, then kept stand for more than 24 hours, meanwhile, the same amount of unmodified graphene is taken and put into the glass bottle, added with water and stirred for 2 hours, then kept stand for more than 24 hours, and the obtained product is used as a control group of the modified graphene, and the experimental result is shown in figure 3. The left side of the graph is an effect graph of raw material graphene standing for 24 hours, the bottom of the container is obviously accumulated by a large amount of precipitates (sediments), the solution is gradually transparent, and the right side of the graph is an effect graph of modified graphene standing for 24 hours, the solution is totally black, and has no transparent sign or accumulation of precipitates (sediments).

The dispersibility of the edge hydroxylated modified graphene is characterized by observing whether solid precipitates (precipitates can aggregate into clusters) exist in the mixed liquid after standing, and the dispersibility of the modified graphene is detailed in table 1.

The infrared spectrogram analysis is performed on the high-dispersibility graphene in the embodiment 1, and the infrared spectrogram analysis is performed on the raw material graphene which is not processed, and the result is shown in fig. 1. Analysis of the IR spectrum of FIG. 1 shows that the modified graphene is at 3400cm compared to the original graphene^-1A more obvious hydroxyl peak appears. EDS elemental analysis is shown in figure 2, and the modified graphene has rich oxygen content. In the figure, the left image is an SEM electron micrograph showing light green, the middle image is a corresponding position C element map showing obvious purple points, and the right image is an O element map showing obvious white points.

Examples 2 to 5

The experimental procedure of example 1 was used to replace only a 10% aqueous solution of dimethylamine borane with a 10% solution of a different borohydride modifier (solution), the other conditions were the same as in example 1, and the experimental results are shown in table 1.

TABLE 1 results of the experiments

As can be seen from Table 1, the graphene modified by the method of the present invention has rich oxygen content and good dispersibility in polar solvents.

Examples 6 to 11

The other conditions are the same as example 1, except that the ratio of graphene to dimethylamine borane in the system is changed, and the experimental results are shown in table 2.

TABLE 2 Experimental results

As can be seen from Table 2, the weight ratio is greater than 100: 1, obvious sedimentation occurs, and the dispersibility is poor; the weight ratio is less than 100: 1, the oxygen content is increased, and the dispersibility is better.

Examples 12 to 19

The other conditions were the same as in example 1 except that the reaction temperature of the system was changed, and the results of the experiment are shown in Table 3.

TABLE 3 results of the experiment

As is clear from Table 3, the precipitation was more remarkable at a temperature of 20 ℃ or lower, the oxygen content was increased between 40 and 200 ℃ and the dispersibility was good, and the dispersibility at a temperature of 200 ℃ or higher.

It should be noted that the technical contents described above are only explained and illustrated to enable those skilled in the art to know the technical spirit of the present invention, and therefore, the technical contents are not to limit the scope of the present invention. The scope of the invention is defined by the appended claims. It should be understood by those skilled in the art that any modification, equivalent replacement, and improvement made based on the spirit of the present invention should be considered to be within the spirit and scope of the present invention.

Claims

1. The preparation method of the edge hydroxylation modified graphene is characterized in that a modifying agent is adopted to carry out modification reaction with graphene, then an oxidizing agent is added to carry out oxidation reaction, and post-treatment is carried out to obtain the edge hydroxylation modified graphene.

2. The method of claim 1, wherein the modifying agent is a boron hydride and the oxidizing agent is a peroxide.

3. The method of claim 2, wherein the boron hydride compound includes but is not limited to borane, diborane, butylborane, pentaborane, trimethylamine borane, dimethylamine borane, tetramethylammonium borohydride, N, N-diethylaniline borane, borane dimethylsulfide complex, 2-methylpyridine borane, diethyl (3-pyridine) borane, borane tetrahydrofuran complex, borane triphenylphosphine complex, borane pyridine complex.

4. The method of claim 2, wherein the peroxide includes but is not limited to hydrogen peroxide, benzoyl peroxide, m-chloroperoxybenzoic acid.

5. The method of claim 2, wherein the weight ratio of graphene to boron hydride is 100: 1 to 1000.

6. The method of claim 1, wherein the post-treatment comprises the steps of standing, filtering, washing, and drying.

7. The method according to claim 1, wherein the temperature of the modification reaction and the oxidation reaction is controlled to 40 to 300 ℃.

8. The method of claim 1, wherein ultrasonic dispersion is used during the modification reaction and the oxidation reaction.

9. The edge-hydroxylated modified graphene obtained by the preparation method according to any one of claims 1 to 8, wherein the modified graphene contains a large number of hydroxyl functional groups at the edge, and thus the dispersibility of the graphene in a polar solvent can be improved.