CN110526293B

CN110526293B - Method for preparing two-dimensional nano material by aid of easily decomposed salt

Info

Publication number: CN110526293B
Application number: CN201910865043.9A
Authority: CN
Inventors: 毋伟; 李月微; 王武; 尹翔鹭
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2019-09-09
Filing date: 2019-09-09
Publication date: 2021-02-19
Anticipated expiration: 2039-09-09
Also published as: CN110526293A

Abstract

A method for preparing a two-dimensional nano material by the aid of easily decomposed salt belongs to the technical field of preparation of two-dimensional nano materials. Mixing and ball-milling layered materials (graphite, molybdenum disulfide and the like) and low-temperature easily-decomposed salt, annealing to obtain pre-intercalation powder, preparing the pre-intercalation powder into dispersion, and stripping by ultrasonic or high-shear to obtain the two-dimensional nano material with less than ten layers. In the invention, the easily decomposable salt is used as the stripping aid, which is beneficial to crushing the layered material and preventing the overlapping of the layers, in addition, part of the easily decomposable salt can be inserted into the layers of the layered powder, which is beneficial to shearing and stripping, and the obtained two-dimensional nano sheet has few layers, controllable size and high yield. The method has the advantages of high stripping efficiency, simple preparation, industrial application prospect and the like.

Description

Method for preparing two-dimensional nano material by aid of easily decomposed salt

Technical Field

The invention belongs to the technical field of two-dimensional nano material preparation, and particularly relates to application of a liquid phase shearing and stripping method in the field of preparation of two-dimensional nano materials.

Background

Compared with bulk phase materials, the nano material has the effects of small size, surface and interface, quantum size, macroscopic quantum tunneling and the like, and has wide application prospect in the fields of optics, magnetics, electrons, biology and the like due to the special properties and rules. Since 2004, Novoselov et al prepared graphene by a micromechanical exfoliation method, and confirmed that two-dimensional nanomaterials can stably exist under ambient conditions. The discovery breaks the traditional cognition of people on the two-dimensional nano material, and promotes more and more researchers to research the preparation, properties and application of the two-dimensional ultrathin nano material. Two-dimensional nanomaterials such as graphene, transition metal sulfides (such as molybdenum disulfide and tungsten disulfide), transition metal oxides (such as molybdenum oxide and titanium oxide) and Mxene have great development potential in the fields of devices, energy storage, sensing, catalysis, medicines and the like, but in order to realize industrial application of the two-dimensional nanomaterials in various fields, a method for preparing a high-quality nanosheet, which is simple, efficient and low in cost, is urgently needed to be developed, is one of bottlenecks which are urgently needed to be overcome at present, and is also a research focus and a difficulty at present.

At present, common methods for preparing two-dimensional nanomaterials include bottom-up methods (such as hydrothermal synthesis, vapor deposition, and epitaxial growth), and top-down methods (such as lithium ion intercalation, redox, electrochemical exfoliation, supercritical fluid exfoliation, and liquid exfoliation). Among them, the bottom-up method and the lithium ion intercalation method have high quality and high yield of the prepared product, but have strict requirements on the operation environment, complicated post-treatment and easy introduction of impurities, which affect the product performance; the redox method is often accompanied with the problems of more product defects and easy environmental pollution; the electrochemical stripping method drives repeated intercalation of anions and cations in an electrolyte solution by using the action of an electric field to finally obtain a few-layer two-dimensional nano material, and the method has relatively high cost and is difficult to realize large-scale production; in addition, although the supercritical fluid exfoliation method which is recently developed has simple process and relatively low cost, the operation process needs to maintain higher pressure for a long time to promote the intercalation exfoliation of the supercritical fluid, and the problem of safe operation of the method becomes a difficult point of industrial amplification; in view of productivity and operation cost, the liquid phase exfoliation method is considered as one of the very easy ways to realize industrial production because it is simple and efficient to operate and produces nanomaterials without special environments. In the liquid phase stripping process, equipment is required to provide enough energy, such as ultrasonic and shearing equipment, to overcome weak van der waals force between layers of the layered material, and proper auxiliary agents and solvent-assisted stripping are also required to be selected, such as natural bulk raw materials or chemically synthesized raw materials are dispersed in water, organic solvents, co-solvents or ionic liquids, and proper auxiliary agents, such as surfactants, salts, metal hydroxides or polymers, are selected to assist stripping, so that the yield and dispersion stability of the nanosheets are improved. Although the methods for preparing two-dimensional nanomaterials by a liquid phase stripping method are infinite, the yield is relatively low at present, and the yield is generally improved by pretreatment, such as microwave pretreatment, dry ice-assisted ball milling and the like, which often requires special environment or expensive additives, so that the process cost is increased, and the method is not favorable for industrial production. Therefore, the development of a liquid phase stripping method which can improve the yield and ensure the product quality at normal temperature and normal pressure, is beneficial to industrial amplification and has high efficiency is a research hotspot in the field of nano material preparation nowadays.

The invention successfully prepares the two-dimensional nanosheet with clean surface and high yield in a simple, efficient and economic manner by using the easily decomposable salt as an auxiliary agent and treating the nanosheet with a ball mill and an ultrasonic/high shear mixer. The advantage of using easily decomposable salts as the auxiliary agent is that: (1) plays the role of physical grinding, accelerates the ball milling and crushing process of the raw materials, and simultaneously prevents the stacking of the sheets. (2) The easily decomposed salt is easily decomposed, the post-treatment is simple, the salt can be separated at high temperature, the product quality is high, and no impurity is introduced. (3) The easily decomposed salt can be partially inserted into the interlayer of the layered material, so that the van der Waals force between the layers is weakened, and the stripping yield is improved. (4) The cost of the easily decomposed salt phase is lower than that of other auxiliary agents. Meanwhile, a ball mill, an ultrasonic or a high-shear mixer which is extremely easy to scale up is used as stripping equipment, so that the possibility of realizing industrial production by the method is improved.

Disclosure of Invention

The invention provides a novel method for preparing a two-dimensional nano material by the aid of easily decomposed salt. The method comprises the steps of taking easily-decomposable salt as an auxiliary agent, performing ball milling in an auxiliary manner, performing annealing treatment to obtain pre-intercalation powder, dispersing the pre-intercalation powder in a solvent, and peeling by ultrasonic or high shear to obtain the two-dimensional nano material with high quality and few defects.

The invention discloses a method for preparing a two-dimensional nano material by the aid of easily decomposed salt, which comprises the following steps:

1) mixing a large-particle layered material serving as a raw material with easily-decomposed salt in a certain proportion, performing ball milling, and performing annealing treatment to remove redundant easily-decomposed salt while annealing so as to increase the distance between the primarily-crushed layered powder layers and obtain pre-intercalated powder;

2) preparing the pre-intercalated powder obtained in the step 1) into dispersion liquid, and stripping and processing the dispersion liquid in an ultrasonic or high-shear mixer to obtain the two-dimensional nano material.

The bulk layered material of step 1) includes, but is not limited to: various kinds of graphite (natural graphite, expanded graphite, flake graphite, etc.), molybdenum disulfide (natural molybdenum disulfide, synthetic molybdenum disulfide), etc.

Easily decomposable salts of step 1), including and not limited to: easily decomposable carbonates such as: ammonium bicarbonate, ammonium carbonate, urea, and the like; nitrate, oxalate and hydrochloride which are easy to decompose, and the salt in the nitrate, the oxalate and the hydrochloride is ammonium salt, and the like.

The mass ratio of the large-particle layered material in the step 1) to the easily decomposed salt is 1:0.1-1: 10.

The ball milling time of the step 1) is 1-24h, and the ball milling rotating speed is 50-350 rpm.

The annealing treatment in the step 1) is carried out under the protection of inert gas, the lowest annealing temperature is the initial decomposition temperature of the easily decomposed salt, the highest annealing temperature is 900 ℃, the temperature rising speed is 2-10 ℃/min, and the annealing is carried out for 2 h.

The pre-intercalated powder of step 2) may be dispersed in different solutions such as organic solvents, water, co-solvents, etc.

And 2) ultrasonic treatment, namely stripping by utilizing ultrasonic cavitation effect generated by an ultrasonic cleaner, probe ultrasound and other instruments, wherein the ultrasonic power is 200W, and the stripping time is 1-6 h.

And 2) treating the high-shear mixer, namely utilizing narrow gaps between a moving rotor and a fixed rotor of the mixer to generate higher local energy dissipation rate and extremely high shear rate for stripping, wherein the stripping rotation speed is 300-.

The method is simple to operate, efficient, low in cost, suitable for large-scale production and wide in application prospect.

Drawings

The embodiments of the present invention will be further described with reference to the drawings;

FIG. 1 TEM image of two-dimensional molybdenum disulfide prepared by exfoliation in example 1 of the present invention;

FIG. 2 TEM image of graphene prepared by exfoliation in example 12 of the present invention;

FIG. 3 is an AFM image of graphene prepared by exfoliation in example 12 of the present invention;

FIG. 4 is a graph of the conductivity of graphene prepared by exfoliation in example 12 of the present invention as a function of pressure;

Detailed Description

To facilitate an understanding of the invention, reference will now be made in detail to the following examples, the scope of which is to be construed as including but not limited to the full breadth of the appended claims and any and all modifications that would occur to one skilled in the art without departing from the scope of the invention.

Example 1

Preparing molybdenum disulfide nanosheets;

mixing the blocky molybdenum disulfide and ammonium bicarbonate according to a mass ratio of 1: 2, mixing, wherein the ball milling speed is 320rpm, and ball milling is carried out for 6 hours;

annealing the ball-milled powder by a tube furnace, heating to 200 ℃ at a heating rate of 10 ℃/min under the protection of inert atmosphere, preserving heat for 2h, and decomposing non-intercalated ammonium bicarbonate;

and re-dispersing the pre-intercalation powder into an NMP organic solvent, performing ultrasonic treatment for 1h, centrifuging the suspension, and taking the supernatant to obtain the molybdenum disulfide nanosheet dispersion liquid. The concentration of the molybdenum disulfide nanosheet dispersion is 11.1mg/mL, the average transverse dimension is about 64nm, the number of layers is less than 10, and the yield is 37%. The morphology of the obtained molybdenum disulfide nanosheet is shown in figure 1.

Example 2

Example 2 differs from example 1 in that the mass ratio of bulk molybdenum disulphide to ammonium chloride is 1: 2, the rest processes are consistent, and after ultrasonic treatment, the yield is 20%.

Example 3

Example 3 differs from example 1 in that the high shear mixer was stripped for 2h at 8000rpm/min, the rest of the process was identical and the yield was 30% after sonication;

example 4

Example 4 differs from example 1 in that the temperature increase rate of the annealing treatment was 2 ℃/min, the rest of the processes were identical, and the yield after the ultrasonic treatment was 29%;

example 5

The difference between the example 5 and the example 1 is that the heat preservation temperature of the annealing treatment is 900 ℃, the rest processes are consistent, and the yield is 10 percent after the ultrasonic treatment;

example 6

Example 6 differs from example 1 in that the holding temperature of the annealing treatment was 60 ℃, the rest of the process was identical, and the yield after the ultrasonic treatment was 25%;

example 7

Preparing a graphene nanosheet;

mixing graphite and ammonium bicarbonate in a mass ratio of 1: 2, mixing, ball milling at the speed of 320rpm for 8 hours;

and re-dispersing the pre-intercalation powder into an NMP organic solvent, wherein the concentration is 20mg/mL, performing ultrasonic treatment for 1h, centrifuging the suspension, and taking a supernatant to obtain a graphene dispersion liquid, wherein the concentration is 2.6mg/mL, and the yield is 13%.

Example 8

Example 8 differs from example 7 in that the graphite and ammonium bicarbonate in bulk are present in a mass ratio of 1: 0.5, the rest processes are consistent, and the yield is 4%.

Example 9

Example 9 differs from example 7 in that the graphite and ammonium bicarbonate in bulk are present in a mass ratio of 1:1, the rest processes are consistent, and the yield is 8%.

Example 10

Example 10 differs from example 7 in that ball milling was carried out for 16h, the rest of the procedure was identical, and the yield was 22%;

example 11

Example 11 differs from example 7 in that ball milling was carried out for 24h, the rest of the procedure was identical, with a yield of 30%;

example 12

Embodiment 12 differs from example 7 in that ball milling is preferably performed for 16h, ultrasound is performed for 5h, the rest processes are consistent, the yield is 41%, the size of the lateral surface of the obtained graphene nanosheet is concentrated in the range of 0-1.3 μm (not 0), and the number of layers is 5-6, as shown in fig. 2 and 3. The prepared graphene powder has a relatively high conductivity of 14285S/m, as shown in fig. 4.

Example 13

Example 13 differs from example 7 by the preferred 16h ball milling and 6h sonication, the remaining procedure was consistent with a 40% yield.

Claims

1. a method for preparing two-dimensional nanomaterials assisted by easily decomposable salt, is characterized in that, comprises following process and steps:

1) Using large particle layered material as raw material, mixed with easily decomposable salt in a certain proportion and ball-milled, then annealing treatment, removing excess easily decomposable salt at the same time of annealing, so as to increase the interlayer spacing of the preliminarily crushed layered powder to obtain pre-intercalated powder;

2) The pre-intercalated powder obtained in step 1) is made into a dispersion liquid, and in an ultrasonic or high shear mixer, peeling and processing are performed to obtain a two-dimensional nanomaterial;

The annealing treatment in step 1) is carried out under the protection of inert gas, the minimum annealing temperature is the initial decomposition temperature of the easily decomposable salt, the maximum annealing temperature is 900°C, the heating rate is 2-10°C/min, and the annealing time is 2h.

2. The method for assisted preparation of two-dimensional nanomaterials by a decomposable salt according to claim 1, wherein the block layered materials in step 1) are various graphites and molybdenum disulfide.

3. according to a kind of easily decomposable salt auxiliary preparation method of two-dimensional nanomaterial according to claim 1, it is characterized in that, the easily decomposable salt of step 1) is carbonate and easily decomposable nitrate, oxalate and Any one or more of the hydrochloride salts.

4. according to a kind of easily decomposable salt auxiliary preparation method of two-dimensional nanomaterial according to claim 3, it is characterized in that, carbonate is selected from ammonium bicarbonate, ammonium carbonate and urea; Nitrate, oxalate and hydrochloric acid The salt in the salt is an ammonium salt.

5. The method for assisted preparation of two-dimensional nanomaterials by a decomposable salt according to claim 1, wherein the mass ratio of the large particle layered material in step 1) to the decomposable salt is 1:0.1-1:10.

6. The method according to claim 1, wherein the ball milling time of step 1) is 1-24h, and the ball milling speed is 50-350rpm.

7. According to the method for preparing two-dimensional nanomaterials assisted by a decomposable salt according to claim 1, the pre-intercalated powder in step 2) can be dispersed into different solutions.

8. according to a kind of easily decomposable salt-assisted method for preparing two-dimensional nanomaterials according to claim 1, step 2) described ultrasonic treatment, namely utilize the ultrasonic cavitation effect produced by instruments such as ultrasonic cleaner, probe ultrasonic to carry out. Stripping, ultrasonic power 200W, stripping time is 1-6h.

9. according to a kind of easily decomposable salt-assisted method for preparing two-dimensional nanomaterials according to claim 1, the high shear mixer treatment described in step 2) is to utilize the narrow gap between the movable stator and rotor of the mixer to produce relatively High local energy dissipation rate and great shear rate for peeling, peeling speed 300-18000rpm/min, peeling time 1-6h.